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Influence of a breathing process on the perception of the thermal environment using personalised ventilation
Building and Environment 96 (2016) 80e90
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Building and Environment journal homepage: www.elsevier.com/locate/buildenv
Influence of a breathing process on the perception of the thermal environment using personalised ventilation ska a Anna Bogdan a, b, *, Barbara Koelblen a, Marta Chludzin a
Warsaw University of Technology, Faculty of Environmental Engineering, Air Condition and Heating Department, Nowowiejska 20 Str., 00-653 Warsaw, Poland b Central Institute for Labour Protection e National Research Institute, Department of Ergonomics, Czerniakowska 16 Str., 00-701 Warsaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 August 2015 Received in revised form 26 October 2015 Accepted 22 November 2015 Available online 1 December 2015
This paper presents the findings of a study examining the influence of the breathing process on the perception of the thermal environment during the use of personalised ventilation (PV). The measurements were made on a sitting thermal manikin with various options of air terminal device, ambient temperature and PV air supply. The thermal environment was assessed by means of the equivalent temperatures measured for each segment of the thermal manikin. The values of teq were calculated for the variants of the breathing function being switched on or off. Based on the measurement results, the values of equivalent temperature were determined to be lower for a breathing variant than for a nonbreathing variant, irrespective of whether the PV system was used to heat or to cool. Therefore, the results confirmed that breathing air jets have the potential to influence the users' thermal sensation. This information is particularly important for the design of the ventilation and air conditioning systems that affect the parameters of the environment in the vicinity of human body. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Personalised ventilation Breathing Thermal manikin Local airflow
1. Introduction The sensation of the indoor thermal environment is affected by environmental factors (such as temperature, velocity, humidity, and radiative temperature) [1,2], as well as the individual factors affecting the amount of heat produced by each person and dissipated into the surroundings (metabolic rate, adaptation to the environment, and thermal insulation clothing) [3,4]. Note that man is also an element that thermally influences the indoor environment. To maintain a constant core temperature of the human body, the heat produced by the liver and muscles is transferred from the internal organs to outside of the body during the process of diffusion, conductivity, and the transport of fluids between the cells (e.g., via blood). From the skin surface, the heat is dissipated into the environment in the following processes: conduction, convection, radiation and moisture evaporation penetrating through the skin and sweat. In addition, from the interior of the body, heat is emitted with the exhaled air in the process of
* Corresponding author. Warsaw University of Technology, Faculty of Environmental Engineering, Air Condition and Heating Department, Nowowiejska 20 Str., 00-653 Warsaw, Poland. E-mail address: [email protected] (A. Bogdan). http://dx.doi.org/10.1016/j.buildenv.2015.11.024 0360-1323/© 2015 Elsevier Ltd. All rights reserved.
convection and evaporation of moisture from the mucous layer covering the respiratory system. Moreover, around the human body, a convective boundary layer is created as a person exhales or inhales air. In recent years, extensive research regarding the microenvironment of the human has been considered by many researchers [5e8]. Among the results, it was determined that the human thermal plume could produce vertical air velocities of 0.1e0.25 m/s [9e12]. Moreover, in the process of breathing, the maximum velocity of air coming out of the mouth can reach up to 2.7 m/s [13]. It was furthermore noted that exhaled air stream disappeared 20 cm from the plane of the mouth. Regarding the nostrils, the maximum air velocity can reach up to 2.5 m/s, and the air stream disappears 10 cm from the nostrils [13]. The air is exhaled mainly through the nostrils, but it can also be exhaled through the mouth. The air stream flowing out of the mouth/nostrils can be treated as a free non isothermal symmetric jet. In the case of the air expelled through the mouth, the axis of the air jet is perpendicular to the surfaces of the mouth, and in the case of the nostrils, two jets are formed with angles an and bn in relation to the plane perpendicular to the surface of the face (Fig. 1). The outflow surface from the nostrils and mouth depends on the height and weight of the human, and in the case of mouth, it also
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Fig. 1. The development of the airflowing out of the nostrils.
depends on the type of human process: the free exhalation or exhalation air during such activities as talking, coughing, and sneezing. The shape of the nostrils does not change significantly during the process of respiration; therefore, the size of the nostrils may be taken as a constant. Based on research involving 14 volunteers aged 20e25, Bogdan [13] determined the average area of one nostril to be equal to 0.78 cm2 and the average surface of the mouth during free breathing to be equal to 2.09 cm2; in addition, the value of angle a was determined to be within 43 ÷ 60 , and b was determined to be in the range of 73 ÷ 91. According to Gupta et al. [14], in the case of breathing when exhaling through the nose, a human-generated air stream flows at the side angle 60 ± 6 and at the front angle of 69 ± 8 , with the front spreading angle of 23 ± 14 and the side spreading angle of 21 ± 10 . When breathing out through the mouth, the air stream is approximately horizontal, with a spreading angle of 30 . However, the above parameters depend significantly on the inter alia body posture [20]. The minute volume ranges is from 8 to 11 L for men and from 6 to 8 L for women, depending on the surface of a human body [15]. The respiration process is divided into three phases: inhale, exhale and pause. The duration of each phase depends on the age of the subject, the type of activity and the state of emotion of the subject [15]. With the increase of the metabolic rate and the level of emotion, the duration of each phase reduces, thereby increasing the frequency of breathing. In a study described by Bogdan [13], the duration of each phase was highly diverse, ranging from 0.7 s to 1.7 s for inhalation and exhalation and from 0.5 s to 1.5 s for a pause. The breathing rate per minute varied randomly in volunteers, ranging from 16 to 24 breaths/min. However, researchers argue whether the airflow inhaled/ exhaled by humans affects the airflow in the human convective boundary layer. This theory was denied by Johnson et al. [21] Homma and Yakiyama [22] and Gao and Niu [8], whereas Bjorn € and Nielsen [23], Melikov and Kaczmarczyk [24] and Ozcan et al. [25] indicated that jets expired from the nostrils have a potential to break the thermal boundary layer. However, assuming that the airflow inhaled/exhaled has an impact the convective boundary layer, the influence of airflow on human thermal sensation should also be noted. Accounting for the above considerations, the hypothesis that inhaled/exhaled airflows generated by humans can affect the perception of thermal environment was assumed.
This hypothesis was examined, assuming the conditions of the internal environment generated by personalised ventilation. The main purpose of personal ventilation (PV) is to supply fresh air directly to the breathing zone of a human to increase amount of inhaled fresh air [16]. At the same time, this approach can be used to create a thermally comfortable environment for the user in the vicinity of the human by providing cooled/heated air [17e19]. During the studies described in this paper, the fact that PV can operate in a cooling or heating option was taken into account.
2. Methods 2.1. Experimental set-up Experiments were conducted in a climatic chamber with the following dimensions: 3.8 m 4.0 m 2.25 m. The chamber is equipped with a piston ventilation system for vertical airflow (air supply through the ceiling and air outlet through the floor). Ventilation in the chamber was switched on solely during breaks between measurements to maintain the proper indoor temperature. During the measurements, the ventilation was switched off. A test stand was composed of the following elements: a thermal manikin named ‘Newton’, the personal ventilation system, a microclimate metre necessary to check the indoor air temperature, and a smoke generator. Fig. 2 shows the placement scheme of the particular elements in the climatic chamber. Measurements were made on a 34-segment thermal manikin named ‘Newton’, manufactured by Measurement Technology Northwest. The manikin is a male-shaped thermal manikin, 178.5 cm tall, equipped with artificial lungs to simulate human breathing. Segmentation of the thermal manikin is shown in Fig. 3. ‘Newton’ is composed of the following segments (in case of symmetrically placed segments, the first number refers to the right side, and the other number to the left side): (1) face, (2) head, (3,5) upper arm front, (4,6) upper arm back, (7,9) forearm front, (8,10) forearm back, (11,12) hand, (13) upper chest, (14) shoulders, (15) stomach, (16) mid back, (17) waist, (18) lower back, (19,22) upper thigh front, (20,23) upper thigh guard, (21,24) upper thigh back, (25,27) lower thigh front, (26,28) lower thigh back, (29,31) calf front, (30,32) calf back, and (33,34) foot. A personalised ventilation system was composed of an air terminal device with a plenum box, a heating-cooling module,
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visualisation purposes was generated by a smoke generator of the FLZ-2000 multi-angle type, producing smoke of a light type. 2.2. Experimental conditions
Fig. 2. A conceptual scheme for the placement of particular elements in the climatic chamber: a) view from above, b) cross-section; 1 e heating-cooling module, 2 e throttle, 3 e fan, 4 e smoke generator (included into the ventilation system only when making a visualisation of air distribution), 5 e air terminal device, 6 e microclimate metre, and 7 e ‘Newton’ - thermal manikin.
Fig. 3. Division of the ‘Newton’ thermal manikin into segments [30].
throttle, fan and ventilation ducts (Fig. 2). The diffuser of size of 400 mm 200 mm was composed of, inter alia, 1 set of horizontal shutters located in the central part of the front panel and 2 sets of vertical shutters located on the external part of the front panel. The structure of the air terminal device made it possible to change the air outflow by modifying the position of the vertical and horizontal shutters. The air parameters in the climatic chamber were measured using a MM-01 microclimate metre. The microclimate metre allows for measurement of the temperature, humidity and velocity of the air and the black-globe temperature. The smoke for airflow
The experiments were aimed at assessing the influence of breathing on the airflow supplied from the PV for various conditions. For this reason, the measurements were taken at two different ambient temperatures, i.e., 20 C and 24 C. For each variant of the ambient temperature, two air temperatures from the PV were applied, i.e., 22 C and 24 C for the ambient temperature of 20 C and 20 Cand 22 C for the ambient temperature of 24 C. As a result, eight variants were obtained. These variants are presented in Table 1. Each variant was examined with the breathing turned on and off. The PV air was delivered to the climatic chamber from the outside. Next, after heating or cooling, the air was directed to the plenum box of the air terminal device. For each test, the variant airflow was 10 L/s. The measurements were made for four different positions of the shutters in the air terminal device (IeV), as presented in Table 2. During the measurements ‘Newton’ was placed in a sitting position in an office armchair at a desk (Fig. 4). The manikin's feet were placed at the footrest. The thermal manikin was clothed in a clothing ensemble consisting of a long-sleeve shirt, a light sweater, long trousers, boxer shorts, socks and light shoes. The thermal insulation of the clothing ensemble together with an armchair and footrest was equal to 1.46 clo. The distance between the face of the thermal manikin and the front panel of the air terminal device was approximately 0.5 m. The height at which the diffuser was mounted in relation to the face is shown in Fig. 2. The temperature control on the segments was set for comfort mode. In this mode, the power supply for each of the segment is calculated using the equations for thermal comfort on the basis of ambient temperature. The core-to-skin heat transfer is simulated by the use of the manikin's nude thermal resistance, which represents the heat loss between the skin and the ambient air. This heat loss is extrapolated using a one-dimensional model, characterising heat loss between core and skin. The heat flux is calculated on the basis of the following comfort control equation: Heat Flux ¼ ðTcore Tskin Þ=Rcore ½W=m2 , where Tcore ¼ 37 C and Rcore ¼ 0.055 Cm2/W and is assumed to be equal to the nude thermal resistance. The breathing process for ‘Newton’ was simulated by in-built artificial lungs. During the measurements with the breathing function on, the air was collected through two nostrils, for which the total surface was equal to 1 cm2 (the nostril velocity was approximately 4.8 m/s). The air subsequently flowed through a container with water localised inside the manikin. This process made it possible to hydrate and warm the air, which was then exhaled through the mouth. The exhale velocity was equal to 2.5 m/ s (the mouth surface was 1.5 cm2), and the direction of the airflow was perpendicular to the manikin's face and toward the air terminal device. The temperature of the exhaled air was 37 C. The respiration volume was equal to 0.001 m3. During one minute, 10 breaths were simulated. The following additional parameters were also introduced: a delay after breathing in and after breathing out (0.3 and 1.0 s, respectively). Taking into account the above data, the inhaled airflow and the exhaled airflow was 1.72 and 1.39 m3/h, respectively. Measurements for each variant lasted 30 min at a steady state of heat exchange between the thermal manikin and the surroundings. In addition, each variant's measurement was repeated twice to calculate the standard deviation values of the collected data. The parameters of the thermal manikin were recorded at the logging
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Table 1 Test variants e division by temperatures and breathing function. Identification of a given test variant
Ambient temperature
Air temperature supplied from PV air terminal device
Breathing process simulation
Functioning of PV in the option of:
20/22/nb 20/22/b 20/24/nb 20/24/b 24/20/nb 24/20/b 24/22/nb 24/22/b
20 C
22 C
OFF ON OFF ON OFF ON OFF ON
heating
24 C 24 C
20 C 22 C
cooling
Table 2 Test variants e position of the shutters in the air terminal device. Variant
Position of vertical shutters
Position of horizontal shutters
I II III IV
widening the airflow (at an angle of 60 ) narrowing the airflow (at an angle of 30 ) parallel to the direction of air supply
Parallel to the direction of air supply widening the airflow (at an angle of 60 ) narrowing the airflow (at an angle of 30 )
were registered every 1.2 min. In addition, the experiments included a simulation of the airflow from PV using a smoke generator. Each variant was recorded on video to document how the smoke coming out of the PV air terminal device was spreading. 2.3. Presentation of the results Data read from ‘Newton’ provided the basis to calculate an equivalent temperature (teq) for each variant. The equivalent temperature is defined as the temperature of an imaginary enclosure with the mean radiant temperature equal to the air temperature and the still air, where the heat exchange between a human and the environment is the same as in real life conditions. The teq value calculated on the basis of tests performed with the thermal manikin relied on equations included in the research work [26e28]: teq ¼ tsi 0; 155·Icli ·qi where: tsi - surface temperature of manikin i-segment, C; Icli - clothing thermal insulation on manikin i-segment, clo; qi - measured manikin heat loss on manikin isegment, W/m2K. The value of teq was calculated for each segment with the exclusion of guards (segments no. 20 and 23). Simulations performed with a smoke generator provided the basis to select a number of video frames to present the fully developed airflow. On the selected images, the contours of the PV airflow were marked. Next, the contours were placed for measurement with the breathing function on and off on a joint photo (representing the breathing variant). For the variants with the thermal manikin simulating the breathing process, light grey colour was used, whereas dark grey was used for the breathing process being switched off. 3. Results
Fig. 4. ‘Newton’e thermal manikin at the measuring stand.
interval of 0.5 min, and parameters of air in the climatic chamber
Fig. 5 shows the equivalent temperature determined during the tests with the air terminal device of variant I in a heating option. The information is complemented with air distribution simulations (Fig. 6a) and b)), with the breathing function being switched on and off. In the case of the breathing function being switched on, teq decreased in almost all the segments in relation to the results obtained when breathing was switched off. In the case of air terminal device I in a heating option, the teq value was similar, irrespective of the temperature of the supplied
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Fig. 5. Equivalent temperature for the air terminal device variant I operating in a heating option.
air (Fig. 5). In the case of air supplied at 22 C or 24 C and the thermal manikin operating in a non-breathing mode, the differences in the values for given segments were insignificant and amounted to a maximum of0.6 C. A slightly higher teq was determined for the variant with air supplied at 22 C. As shown in Fig. 6a) and b), in the case of air supplied from PV at 24 C, the airflow rises quickly and does not fully reach the thermal manikin, whereas the airflow at 22 C reaches the manikin and its breathing zone to a greater extent. A similar situation can be observed for variants with the breathing switched on. The differences in teq for variants with air supplied at 22 C or 24 C were up to 0.8 C. Again, the airflow having the temperature of 22 C had a greater influence on the manikin's surface; hence teq is higher, particularly in the upper segments of the manikin. Significant differences were noted between the variants with the manikin's breathing function being switched on or switched off. The differences occurred on the majority of segments, except for the hands and the feet. The greatest differences were observed for the following body parts: arms, shoulders, torso and thighs (differences were up to 2.7 C maximum for both variants of the air temperature from the PV system). The differences in the distribution of air supplied from the PV air terminal device can be observed in Fig. 6a) and b). A more intensive air movement in the area of the thermal manikin's torso was observed when the breathing function was switched on. At the same time, the impact of the air supplied from PV onto the manikin tended to decrease. For this type of setup of the air terminal device operating in a heating option, the influence of breathing was higher for air supplied from the PV with temperature equal to 22 C, rather than 24 C.Furthermore, it was observed that the breathing process had a significant influence on the values of teq and its influence was higher than the changes in temperature of the PV air supply. In the case of an air terminal device in variant II operating in a heating option for non-breathing mode, the results of teq significantly vary, depending on the temperature of air supplied from PV (Fig. 7). The setup of the shutters caused the airflow to be narrower.
As a result, the airflow reached the surface of the thermal manikin to a larger extent than the case of air terminal device I, which caused a greater dependence of teq on the temperature of the supplied air for the non-breathing variants. This effect can be observed in Fig. 6 c) and d). The differences in teq between 20/22/nb and 20/24/nb variants are up to 1.9 C, whereas in the upper segments of the thermal manikin, those differences range from 1 to 1.5 C. Turning on the breathing option reduces the impact of the airflow from PV on the manikin. As a result, the values of teq for air supplied from the PV at the temperature 22 C and 24 C are similar on all the segments. The maximum temperature difference between the segments is 0.5 C. At the same time, the difference in teq between breathing and non-breathing variants for air supplied from PV with the temperature equal to 22 C is up to 5.0 C, whereas for air temperature equal 24 C, it is even up to 3.8 C. It can therefore be concluded that breathing, in the case of personalised ventilation, has a significant impact on teq and the thermal environment in the vicinity of the thermal manikin. In the case of this air terminal device, the use of a breathing process caused an increase of the PV airflow above the breathing zone of the thermal manikin. In the case of air terminal device III, the supplied airflow is spreading vertically. As a result, it can again be observed that the airflow from PV at 24 C reaches the thermal manikin to a smaller extent than at 22 C. Such a phenomenon is attributable to the fact that air having the temperature of 24 C bends up quicker towards the top and does not reach the thermal manikin's breathing zone (Fig. 6 e) and f)). For this reason, as shown in Fig. 8, teq for nonbreathing variants was higher for air supplied at 22 C. This difference, amounting to 1.2 C at maximum, is most noticeable on the upper segments of the thermal manikin. At the same time, the standard deviation for air supplied at 22 C is significantly smaller than for air at 24 C. Turning the breathing option on stabilises the airflow around the thermal manikin. In consequence, the temperature of supplied air is of secondary importance and has a
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Fig. 6. Airflow distribution for IeIV air terminal device variants in the case of nonbreathing (light grey colour) and breathing (dark grey colour) modes for the PV operating in a heating option (ambient temperature of 20 C and air supply temperature of 22 or 24 C).
secondary impact on teq for particular segments e differences in teq are up to 0.5 C. At the same time, the standard deviation for breathing variants is significantly lower than for non-breathing variants. In the case of air terminal device IV, the airflow narrows vertically, which results in a higher concentration of the supplied airflow. In the case of non-breathing variants, teq for both options of air supplied temperature was similar and remained within the standard deviation of both variants (the maximum difference up to
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1.3 C). The supplied air of 24 C caused a slightly higher value of teq on the upper segments of the thermal manikin and the air supplied at 22 C caused a slightly higher value on the lower segments (Fig. 9). When the breathing function was switched on, teq on the majority of segments was practically the same, regardless of the temperature of supplied air. Slight differences can only be observed on the upper segments of the thermal manikin (up to 0.6 C). All of the results remain within the standard deviation. As can be clearly seen in Fig. 5h), when the breathing process is switched on, air supplied from PV rises and does not reach the surface of the thermal manikin. It can be therefore concluded that teq is dependent on the stream of breathing air, rather than airflow from PV. The situation is different for PV operating under a cooling option. In the case of air terminal device I, the differences between teq for non-breathing variants are significant (Fig. 10). With the breathing option switched on, a higher teq was obtained for air supplied at 20 C rather than 22 C. The differences in teq reached up to 2 C. Air stream supplied from PV at 20 C had a shorter range and tended to fall more rapidly, failing to fully reach the surface of the thermal manikin. As a result of turning the breathing function on, teq became more independent from the air supplied from PV, and teq levelled out on particular segments. Differences between teq with the breathing option on for both temperatures of supplied air were noted mainly on the upper parts of the thermal manikin's segments, whereas for the remaining segments, they remained within the standard deviation. Fig. 11a) and b) presents distribution of air for air terminal device I in particular variants. In the case of the air terminal device II, for which the air supplied from PV is more concentrated, teq for non-breathing variants was more similar than was the case for the air terminal device I (Fig. 12). Slight differences were only noted for the following segments: face, head and from the upper chest to thighs; however, they remained within the standard deviation. As seen in Fig. 11c) and d), in the case of this air terminal device, the airflow distribution without breathing is similar, irrespective of the temperature of delivered air. As a result of switching the breathing process on, teq decreased by as much as3.7 C. A decrease was noted on all the segments, except for the feet, where teq slightly increased. Again, the values of teq in the breathing variant were similar, irrespective of the temperature of air supplied from the PV, and greater differences were noted only for the following segments: face, head, upper chest, and shoulders. For air supplied from PV at 20 C, the airflow bent downward in the lower part of the thermal manikin. In the case of the air terminal device III, in which the airflow is spreading vertically, the situation is similar to the one for air terminal device I. In the case of the non-breathing variants, the values of teq are higher for air supplied at 20 C (Fig. 13), in which the air supplied from the PV does not fully reach the surface of the thermal manikin. This situation is shown in Fig. 11 e) and f). An introduction of breathing resulted in significant lowering of teq on the majority of the segments. At the same time, teq was similar on the lower segments of the thermal manikin for air supplied from PV at 22 C and 20 C, whereas it significantly differed on the face, head and upper chest. teq for air supplied at 22 C was higher than for 20 C. In the case of air terminal device IV, the airflow is narrow and concentrated vertically. In consequence, a bigger mass reaches the thermal manikin (Fig. 11g) and h)). Airflow from the PV for nonbreathing variants with air supplied at 22 C reaches the manikin's face, and in the case of air supplied at 20 C, it quickly decreases and reaches mainly the manikin's torso. For this reason, differences in teq for the non-breathing variant were observed up from the upper chest, shoulders, stomach down to the thighs (Fig. 14). On the other segments, teq remained similar. For the majority of segments, however, the differences did not exceed the
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Fig. 7. Equivalent temperature for air terminal device variant II operating in a heating option.
Fig. 8. Equivalent temperature for air terminal device variant III operating in a heating option.
standard deviation for both variants. Introduction of a breathing variant resulted again in a significant reduction of teq, and in the case of air supplied at 20 C, an even more rapid reduction towards the lower parts of the thermal manikin was noted. This phenomenon caused differences in teq observed on the upper segments of the thermal manikin, composed of its head and torso. On the remaining segments, the results were similar or remained within
the standard deviation. A comparison of mean teq for the entire thermal manikin (calculated as the surface segments weighted average) captures the global differences between non-breathing and breathing variants. For the heating function in the 20/22/nb variants, the mean teq value ranged between 21.0 C and 22.3 C for different setups (IeIV) of the air terminal device. The introduction of breathing resulted in
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Fig. 9. Equivalent temperature for air terminal device variant IV operating in a heating option.
Fig. 10. Equivalent temperature for air terminal device variant I operating in a cooling option.
a decrease of the mean teq value, which ranged between 19.4 C and 19.8 C. In the 20/24/nb variants the mean teq value ranged from 21.0 C to 21.8 C, and for the same temperature variants with the breathing function on the obtained values remained within the range of 19.5 C e 19.9 C. In the case of the PV working under the cooling option for the 24/22/nb variants, the mean teq value ranged from 23.8 C to 24.7 C, whereas under the breathing variants, the
value ranged from 22.8 C to 22.9 C. In the case of 24/20/nb variants, the teq values ranged from 24.2 C to 24.7 C, whereas in the 24/20/b variants, the values ranged from 22.4 C to 22.8 C.
4. Discussion and conclusions Based on the survey, exhaled air jets were found to have the
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1. Depending on the type of the air terminal device, the airflow from the PV reached, to a larger or smaller extent, the surface of the thermal manikin and influenced the teq value. For this reason, the impact of breathing on teq was conditioned by the type of the air terminal device. 2. Streams of the respiratory air of the thermal manikin influenced the direction of the air supplied from the PV and, in the case of a heating option, caused the air to lift more rapidly, resulting in a smaller volume of PV air reaching the thermal manikin. In the case of a cooling option, these streams caused a more rapid decrease of air for the air supplied from the PV at 20 C. 3. teq for the non-breathing variants and with different temperatures of air supplied from the PV varied to a larger or smaller degree, depending on the test variant. Greater differences were noted in the case of cooling mode than in the case of PV operating in a heating mode. 4. Introduction of a breathing process caused reduction of the teq value in relation to non-breathing variants. The greatest decrease of teq was noted for the 20/22 variant and the air terminal device II (reduction of mean teq value for the entire manikin by 2.6 C), whereas the smallest decrease was found for the 24/22 variant and air terminal devicesI and III (reduction of mean teq value for the whole manikin by 0.9 C). 5. The values of teq in the case of breathing variants at various air temperatures supplied from PV were similar or the same. The changes were mainly noted on the segments of upper arm and upper thigh for the PV operating in a heating mode, and the changes were found on the head, upper chest and shoulders for PV in a cooling mode. The airflow inhaled/exhaled by man has a short range but considerable air velocity, and the temperature is usually higher than the ambient air temperature, thereby affecting the airflow in the human convective boundary layer. The test results are consistent with the results obtained by Bjorn and Nielsen [23], who determined that the exhaled air can penetrate the thermal plume and Impose exposure to the other manikin standing at 0.4 m away, € as well as the results of Melikov and Kaczmarczyk [24] and of Ozcan
Fig. 11. Airflow distribution for IeIV air terminal device variants in the case of nonbreathing (light grey colour) and breathing (dark grey colour) modes for the PV operating in a cooling option (ambient temperature 24 C and air supply temperature 22 or 20 C).
potential to influence the value of the equivalent temperature, thereby affecting the users' heat sensation. In every variant, after the turning on of the manikin breathing process, the decrease of teq was observed compared to the variant without the breathing process on, and the environment experienced by the user was found to be cooler. The following are more detailed conclusions resulting from the research:
et al. [25], who indicated that the jets expired from the nostrils of a seated breathing manikin could break the thermal boundary layer. The thickness of the convective boundary layer depends on a body part, as described by, but it is usually approximately 5 cm [6,7], so that the inhaled/exhaled airflow with velocity greater than 2 m/s is able to pass through this layer and consequently also affects the thermal perception by humans. This information is particularly important for the design of ventilation and air conditioning systems that shape the parameters of the environment in the vicinity of human body. The conducted studies provide sufficient grounds to conclude that streams of respiratory air have a greater influence on teq than air temperature supplied from the PV in relation to the indoor air temperature. Both in a heating and cooling option, teq tended to decrease significantly. At the same time, the values of teq were similar for variants with different air temperatures supplied from the PV. It can be therefore assumed that the breathing process has a significant impact on the perception of the indoor thermal environment using the PV system. The air exhaled by the thermal manikin affected the distribution of air from the PV and caused the flow direction to change. This process stems from a relatively small velocity of air delivered from the PV in relation to the air velocity in the human respiratory stream. In the case of studies presented within this publication, in the first stage, air terminal devices had the construction adjusted to the users' subjective feelings. The minimum volume of hygienic air was assumed in accordance with ASHRAE [29]; however, the size of the air terminal device was
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Fig. 12. Equivalent temperature for air terminal device variant II operating in a cooling option.
Fig. 13. Equivalent temperature for air terminal device variant III operating in a cooling option.
established during the tests with human subjects, so that air velocity reaching the human's body was 0.25 m/s at the maximum. The majority of publications on PV only indicated the values of the airflow volume used for the tests. However, taking into consideration the size of the PV air terminal devices, it can be assumed that air velocities were higher than 0.25 m/s in the user breathing zone. Air velocities amounting to approximately 0.4 m/s at the
outflow from PV terminal devices were observed, in our case, to be uncomfortable for the users. It was determined that the air supplied from PV at the assumed velocity collided with the air exhaled by the thermal manikin. Furthermore, it was observed that only the case of PV the cooling mode had an impact on the indoor thermal environment perceived by the user. The presented studies revealed the problem of the proper
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Fig. 14. Equivalent temperature for air terminal device variant IV operating in a cooling option.
determination of the air velocities supplied from the PV. On one hand, every attempt should be made to maintain the highest level of air quality; hence, the air delivered from the PV should induce indoor air as little as possible. On the other hand, the air velocity cannot be too high due to the users' thermal sensation. At the same time, it is important to bear in mind the influence of the human breathing process on the airflow from the PV. Acknowledgement The studies were developed on the basis of research work conducted within the project no. N R04 0018 10 financed by the National Centre for Research and Development in the years 2011e2015. References [1] P.O. Fanger, Thermal Comfort, McGraw-Hill, New York, USA, 1970. [2] K. Parson, Human Thermal Environments. The Effects of Hot, Moderate and Cold Environments on Human Health, Comfort and Performance, Taylor&Francis, 2003. [3] S. Tanabe, M. Haneda, N. Nishihara, Workplace productivity and individual thermal satisfaction, Build. Environ. 91 (2015) 42e50. [4] S. Karjalainen, O. Koistinen, User problems with individual temperature control in offices, Build. Environ. 42 (2007) 2880e2887. [5] A. Melikov, Human body micro-environment: the benefits of controlling airflow interaction, Build. Environ. 91 (September 2015) 70e77. [6] D. Licina, J. Pantelic, A. Melikov, Sekhar Ch, K.W. Tham, Experimental investigation of the human convective boundary layer in a quiescent indoor environment, Build. Environ. 75 (May 2014) 79e91. [7] D. Licina, A. Melikov, Sekhar Ch, K.W. Tham, Air temperature investigation in microenvironment around a human body, Build. Environ. 92 (October 2015) 39e47. [8] N. Gao, J. Niu, CFD study on micro-environment around human body and personalized ventilation, Build. Environ. 39 (2004) 795e805. [9] D. Zukowska, A. Melikov, Z. Popiolek, Impact of personal factors and furniture arrangement on the thermal plume above a sitting occupant, Build. Environ. 49 (March 2012) 104e116. [10] E. Mundt, Displacement ventilation systems e convection flows and temperature gradients, Build. Environ. 30 (1) (1995) 129e133. [11] A. Bogdan, M. Chludzinska, Comparative evaluation of thermal plumes formed above a thermal manikin and humans e the pilot study results, in:
Proceedings of Indoor Air, 2008. ID: 147, Copenhagen, Denmark. [12] D. Zukowska, A. Melikov, Z. Popiolek, Impact of facially applied air movement on the development of the thermal plume above a sitting occupant, in: Proceedings of the 12th International Conference on Air Distribution in Rooms e Roomvent 2011, Trondheim, Nor., 2011. [13] A. Bogdan, Cieplne oddziaływanie organizmu człowieka na zmiany mikrokli , CIOP-PIB, Warszawa, 2009 (In Polish). matu pomieszczen [14] J.K. Gupta, C.H. Lin, Q. Chen, Characterizing exhaled airflow from breathing and talking, Indoor Air 20 (2009) 31e39. [15] H. Kociuba-Usciłko, Termoregulacja, in: W.Z. Traczyk, A. Trzebski (Eds.), Fizjologa Człowieka Z Elementami Fizjologii Klinicznej I Stosowanej, Red, PZWL, Warszawa, 2003 (In Polish). [16] A.K. Melikov, Personalized ventilation, Indoor Air 14 (7) (2004) 157e167. [17] A.K. Melikov, R. Cermak, M. Majer, Personalized ventilation: evaluation of different air terminal devices, Energy Build. 34 (8) (2002) 829e836. [18] J. Kaczmarczyk, A. Melikov, P.O. Fanger, Human response to personalized ventilation and mixing ventilation, Indoor Air 14 (8) (2004) 17e29. [19] A.K. Melikov, M.A. Skwarczynski, J. Kaczmarczyk, J. Zabecky, Use of personalized ventilation for improving health, comfort, and performance at high room temperature and humidity, Indoor Air 23 (2013) 250e263. [20] T. Zhang, S. Yin, S. Wang, Quantify impacted scope of human expired air under different head postures and varying exhalation rates, Build. Environ. 46 (2011) 1928e1936. [21] A.E. Johnson, B. Fletcher, C.J. Saunders, Air movement around a worker in a low-speed flow field, Annu. Occup. Hyg. 40 (1996) 57e64. [22] H. Homma, M. Yakiyama, Examination of free convection around occupant's body caused by its metabolic heat, ASHRAE Trans. 94 (1988) 104e124. [23] E. Bjørn, P.V. Nielsen, Dispersal of exhaled air and personal exposure in displacement ventilated rooms, Indoor Air 12 (3) (2002) 147e164. [24] A. Melikov, J. Kaczmarczyk, Measurement and prediction of indoor air quality using a breathing thermal manikin, Indoor Air 17 (1) (2007) 50e59. € [25] O. Ozcan, K.E. Meyer, A.K. Melikov, A visual description of the convective flow filed around the head of a human, J. Vis. 8 (1) (2005) 23e31. [26] S. Tanabe, E.A. Arens, F.S. Bauman, Evaluating thermal environments by using a thermal manikin with controlled skin surface temperature, ASHRAE Trans. 100 (1) (1994) 39e48. [27] H.O. Nilsson, I. Holmer, Comfort climate evaluation with thermal manikin methods and computer simulation models, Int. J. Indoor Air Qual. Clim. 13 (2003) 28e37. ska, Assessment of thermal comfort using personalized [28] A. Bogdan, M. Chludzin ventilation, HVAC&R Res. 16 (4) (2010) 529e542. [29] ASHRAE Handbook, ASHRAE Handbook e Fundamentals, Atlanta, GA, 2009. [30] Measurement Technology Northwest, Epoxy Thermal Manikin (Newton) Product Brochure. Available at: http://thermal.mtnw-usa.com/sites/thermal. mtnw-usa.com/files/product_brochures/NEWTON%20Manikin_Spec%20Sheet. pdf [last accessed November 2014].
Contents lists available at ScienceDirect
Building and Environment journal homepage: www.elsevier.com/locate/buildenv
Influence of a breathing process on the perception of the thermal environment using personalised ventilation ska a Anna Bogdan a, b, *, Barbara Koelblen a, Marta Chludzin a
Warsaw University of Technology, Faculty of Environmental Engineering, Air Condition and Heating Department, Nowowiejska 20 Str., 00-653 Warsaw, Poland b Central Institute for Labour Protection e National Research Institute, Department of Ergonomics, Czerniakowska 16 Str., 00-701 Warsaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 August 2015 Received in revised form 26 October 2015 Accepted 22 November 2015 Available online 1 December 2015
This paper presents the findings of a study examining the influence of the breathing process on the perception of the thermal environment during the use of personalised ventilation (PV). The measurements were made on a sitting thermal manikin with various options of air terminal device, ambient temperature and PV air supply. The thermal environment was assessed by means of the equivalent temperatures measured for each segment of the thermal manikin. The values of teq were calculated for the variants of the breathing function being switched on or off. Based on the measurement results, the values of equivalent temperature were determined to be lower for a breathing variant than for a nonbreathing variant, irrespective of whether the PV system was used to heat or to cool. Therefore, the results confirmed that breathing air jets have the potential to influence the users' thermal sensation. This information is particularly important for the design of the ventilation and air conditioning systems that affect the parameters of the environment in the vicinity of human body. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Personalised ventilation Breathing Thermal manikin Local airflow
1. Introduction The sensation of the indoor thermal environment is affected by environmental factors (such as temperature, velocity, humidity, and radiative temperature) [1,2], as well as the individual factors affecting the amount of heat produced by each person and dissipated into the surroundings (metabolic rate, adaptation to the environment, and thermal insulation clothing) [3,4]. Note that man is also an element that thermally influences the indoor environment. To maintain a constant core temperature of the human body, the heat produced by the liver and muscles is transferred from the internal organs to outside of the body during the process of diffusion, conductivity, and the transport of fluids between the cells (e.g., via blood). From the skin surface, the heat is dissipated into the environment in the following processes: conduction, convection, radiation and moisture evaporation penetrating through the skin and sweat. In addition, from the interior of the body, heat is emitted with the exhaled air in the process of
* Corresponding author. Warsaw University of Technology, Faculty of Environmental Engineering, Air Condition and Heating Department, Nowowiejska 20 Str., 00-653 Warsaw, Poland. E-mail address: [email protected] (A. Bogdan). http://dx.doi.org/10.1016/j.buildenv.2015.11.024 0360-1323/© 2015 Elsevier Ltd. All rights reserved.
convection and evaporation of moisture from the mucous layer covering the respiratory system. Moreover, around the human body, a convective boundary layer is created as a person exhales or inhales air. In recent years, extensive research regarding the microenvironment of the human has been considered by many researchers [5e8]. Among the results, it was determined that the human thermal plume could produce vertical air velocities of 0.1e0.25 m/s [9e12]. Moreover, in the process of breathing, the maximum velocity of air coming out of the mouth can reach up to 2.7 m/s [13]. It was furthermore noted that exhaled air stream disappeared 20 cm from the plane of the mouth. Regarding the nostrils, the maximum air velocity can reach up to 2.5 m/s, and the air stream disappears 10 cm from the nostrils [13]. The air is exhaled mainly through the nostrils, but it can also be exhaled through the mouth. The air stream flowing out of the mouth/nostrils can be treated as a free non isothermal symmetric jet. In the case of the air expelled through the mouth, the axis of the air jet is perpendicular to the surfaces of the mouth, and in the case of the nostrils, two jets are formed with angles an and bn in relation to the plane perpendicular to the surface of the face (Fig. 1). The outflow surface from the nostrils and mouth depends on the height and weight of the human, and in the case of mouth, it also
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Fig. 1. The development of the airflowing out of the nostrils.
depends on the type of human process: the free exhalation or exhalation air during such activities as talking, coughing, and sneezing. The shape of the nostrils does not change significantly during the process of respiration; therefore, the size of the nostrils may be taken as a constant. Based on research involving 14 volunteers aged 20e25, Bogdan [13] determined the average area of one nostril to be equal to 0.78 cm2 and the average surface of the mouth during free breathing to be equal to 2.09 cm2; in addition, the value of angle a was determined to be within 43 ÷ 60 , and b was determined to be in the range of 73 ÷ 91. According to Gupta et al. [14], in the case of breathing when exhaling through the nose, a human-generated air stream flows at the side angle 60 ± 6 and at the front angle of 69 ± 8 , with the front spreading angle of 23 ± 14 and the side spreading angle of 21 ± 10 . When breathing out through the mouth, the air stream is approximately horizontal, with a spreading angle of 30 . However, the above parameters depend significantly on the inter alia body posture [20]. The minute volume ranges is from 8 to 11 L for men and from 6 to 8 L for women, depending on the surface of a human body [15]. The respiration process is divided into three phases: inhale, exhale and pause. The duration of each phase depends on the age of the subject, the type of activity and the state of emotion of the subject [15]. With the increase of the metabolic rate and the level of emotion, the duration of each phase reduces, thereby increasing the frequency of breathing. In a study described by Bogdan [13], the duration of each phase was highly diverse, ranging from 0.7 s to 1.7 s for inhalation and exhalation and from 0.5 s to 1.5 s for a pause. The breathing rate per minute varied randomly in volunteers, ranging from 16 to 24 breaths/min. However, researchers argue whether the airflow inhaled/ exhaled by humans affects the airflow in the human convective boundary layer. This theory was denied by Johnson et al. [21] Homma and Yakiyama [22] and Gao and Niu [8], whereas Bjorn € and Nielsen [23], Melikov and Kaczmarczyk [24] and Ozcan et al. [25] indicated that jets expired from the nostrils have a potential to break the thermal boundary layer. However, assuming that the airflow inhaled/exhaled has an impact the convective boundary layer, the influence of airflow on human thermal sensation should also be noted. Accounting for the above considerations, the hypothesis that inhaled/exhaled airflows generated by humans can affect the perception of thermal environment was assumed.
This hypothesis was examined, assuming the conditions of the internal environment generated by personalised ventilation. The main purpose of personal ventilation (PV) is to supply fresh air directly to the breathing zone of a human to increase amount of inhaled fresh air [16]. At the same time, this approach can be used to create a thermally comfortable environment for the user in the vicinity of the human by providing cooled/heated air [17e19]. During the studies described in this paper, the fact that PV can operate in a cooling or heating option was taken into account.
2. Methods 2.1. Experimental set-up Experiments were conducted in a climatic chamber with the following dimensions: 3.8 m 4.0 m 2.25 m. The chamber is equipped with a piston ventilation system for vertical airflow (air supply through the ceiling and air outlet through the floor). Ventilation in the chamber was switched on solely during breaks between measurements to maintain the proper indoor temperature. During the measurements, the ventilation was switched off. A test stand was composed of the following elements: a thermal manikin named ‘Newton’, the personal ventilation system, a microclimate metre necessary to check the indoor air temperature, and a smoke generator. Fig. 2 shows the placement scheme of the particular elements in the climatic chamber. Measurements were made on a 34-segment thermal manikin named ‘Newton’, manufactured by Measurement Technology Northwest. The manikin is a male-shaped thermal manikin, 178.5 cm tall, equipped with artificial lungs to simulate human breathing. Segmentation of the thermal manikin is shown in Fig. 3. ‘Newton’ is composed of the following segments (in case of symmetrically placed segments, the first number refers to the right side, and the other number to the left side): (1) face, (2) head, (3,5) upper arm front, (4,6) upper arm back, (7,9) forearm front, (8,10) forearm back, (11,12) hand, (13) upper chest, (14) shoulders, (15) stomach, (16) mid back, (17) waist, (18) lower back, (19,22) upper thigh front, (20,23) upper thigh guard, (21,24) upper thigh back, (25,27) lower thigh front, (26,28) lower thigh back, (29,31) calf front, (30,32) calf back, and (33,34) foot. A personalised ventilation system was composed of an air terminal device with a plenum box, a heating-cooling module,
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visualisation purposes was generated by a smoke generator of the FLZ-2000 multi-angle type, producing smoke of a light type. 2.2. Experimental conditions
Fig. 2. A conceptual scheme for the placement of particular elements in the climatic chamber: a) view from above, b) cross-section; 1 e heating-cooling module, 2 e throttle, 3 e fan, 4 e smoke generator (included into the ventilation system only when making a visualisation of air distribution), 5 e air terminal device, 6 e microclimate metre, and 7 e ‘Newton’ - thermal manikin.
Fig. 3. Division of the ‘Newton’ thermal manikin into segments [30].
throttle, fan and ventilation ducts (Fig. 2). The diffuser of size of 400 mm 200 mm was composed of, inter alia, 1 set of horizontal shutters located in the central part of the front panel and 2 sets of vertical shutters located on the external part of the front panel. The structure of the air terminal device made it possible to change the air outflow by modifying the position of the vertical and horizontal shutters. The air parameters in the climatic chamber were measured using a MM-01 microclimate metre. The microclimate metre allows for measurement of the temperature, humidity and velocity of the air and the black-globe temperature. The smoke for airflow
The experiments were aimed at assessing the influence of breathing on the airflow supplied from the PV for various conditions. For this reason, the measurements were taken at two different ambient temperatures, i.e., 20 C and 24 C. For each variant of the ambient temperature, two air temperatures from the PV were applied, i.e., 22 C and 24 C for the ambient temperature of 20 C and 20 Cand 22 C for the ambient temperature of 24 C. As a result, eight variants were obtained. These variants are presented in Table 1. Each variant was examined with the breathing turned on and off. The PV air was delivered to the climatic chamber from the outside. Next, after heating or cooling, the air was directed to the plenum box of the air terminal device. For each test, the variant airflow was 10 L/s. The measurements were made for four different positions of the shutters in the air terminal device (IeV), as presented in Table 2. During the measurements ‘Newton’ was placed in a sitting position in an office armchair at a desk (Fig. 4). The manikin's feet were placed at the footrest. The thermal manikin was clothed in a clothing ensemble consisting of a long-sleeve shirt, a light sweater, long trousers, boxer shorts, socks and light shoes. The thermal insulation of the clothing ensemble together with an armchair and footrest was equal to 1.46 clo. The distance between the face of the thermal manikin and the front panel of the air terminal device was approximately 0.5 m. The height at which the diffuser was mounted in relation to the face is shown in Fig. 2. The temperature control on the segments was set for comfort mode. In this mode, the power supply for each of the segment is calculated using the equations for thermal comfort on the basis of ambient temperature. The core-to-skin heat transfer is simulated by the use of the manikin's nude thermal resistance, which represents the heat loss between the skin and the ambient air. This heat loss is extrapolated using a one-dimensional model, characterising heat loss between core and skin. The heat flux is calculated on the basis of the following comfort control equation: Heat Flux ¼ ðTcore Tskin Þ=Rcore ½W=m2 , where Tcore ¼ 37 C and Rcore ¼ 0.055 Cm2/W and is assumed to be equal to the nude thermal resistance. The breathing process for ‘Newton’ was simulated by in-built artificial lungs. During the measurements with the breathing function on, the air was collected through two nostrils, for which the total surface was equal to 1 cm2 (the nostril velocity was approximately 4.8 m/s). The air subsequently flowed through a container with water localised inside the manikin. This process made it possible to hydrate and warm the air, which was then exhaled through the mouth. The exhale velocity was equal to 2.5 m/ s (the mouth surface was 1.5 cm2), and the direction of the airflow was perpendicular to the manikin's face and toward the air terminal device. The temperature of the exhaled air was 37 C. The respiration volume was equal to 0.001 m3. During one minute, 10 breaths were simulated. The following additional parameters were also introduced: a delay after breathing in and after breathing out (0.3 and 1.0 s, respectively). Taking into account the above data, the inhaled airflow and the exhaled airflow was 1.72 and 1.39 m3/h, respectively. Measurements for each variant lasted 30 min at a steady state of heat exchange between the thermal manikin and the surroundings. In addition, each variant's measurement was repeated twice to calculate the standard deviation values of the collected data. The parameters of the thermal manikin were recorded at the logging
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Table 1 Test variants e division by temperatures and breathing function. Identification of a given test variant
Ambient temperature
Air temperature supplied from PV air terminal device
Breathing process simulation
Functioning of PV in the option of:
20/22/nb 20/22/b 20/24/nb 20/24/b 24/20/nb 24/20/b 24/22/nb 24/22/b
20 C
22 C
OFF ON OFF ON OFF ON OFF ON
heating
24 C 24 C
20 C 22 C
cooling
Table 2 Test variants e position of the shutters in the air terminal device. Variant
Position of vertical shutters
Position of horizontal shutters
I II III IV
widening the airflow (at an angle of 60 ) narrowing the airflow (at an angle of 30 ) parallel to the direction of air supply
Parallel to the direction of air supply widening the airflow (at an angle of 60 ) narrowing the airflow (at an angle of 30 )
were registered every 1.2 min. In addition, the experiments included a simulation of the airflow from PV using a smoke generator. Each variant was recorded on video to document how the smoke coming out of the PV air terminal device was spreading. 2.3. Presentation of the results Data read from ‘Newton’ provided the basis to calculate an equivalent temperature (teq) for each variant. The equivalent temperature is defined as the temperature of an imaginary enclosure with the mean radiant temperature equal to the air temperature and the still air, where the heat exchange between a human and the environment is the same as in real life conditions. The teq value calculated on the basis of tests performed with the thermal manikin relied on equations included in the research work [26e28]: teq ¼ tsi 0; 155·Icli ·qi where: tsi - surface temperature of manikin i-segment, C; Icli - clothing thermal insulation on manikin i-segment, clo; qi - measured manikin heat loss on manikin isegment, W/m2K. The value of teq was calculated for each segment with the exclusion of guards (segments no. 20 and 23). Simulations performed with a smoke generator provided the basis to select a number of video frames to present the fully developed airflow. On the selected images, the contours of the PV airflow were marked. Next, the contours were placed for measurement with the breathing function on and off on a joint photo (representing the breathing variant). For the variants with the thermal manikin simulating the breathing process, light grey colour was used, whereas dark grey was used for the breathing process being switched off. 3. Results
Fig. 4. ‘Newton’e thermal manikin at the measuring stand.
interval of 0.5 min, and parameters of air in the climatic chamber
Fig. 5 shows the equivalent temperature determined during the tests with the air terminal device of variant I in a heating option. The information is complemented with air distribution simulations (Fig. 6a) and b)), with the breathing function being switched on and off. In the case of the breathing function being switched on, teq decreased in almost all the segments in relation to the results obtained when breathing was switched off. In the case of air terminal device I in a heating option, the teq value was similar, irrespective of the temperature of the supplied
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Fig. 5. Equivalent temperature for the air terminal device variant I operating in a heating option.
air (Fig. 5). In the case of air supplied at 22 C or 24 C and the thermal manikin operating in a non-breathing mode, the differences in the values for given segments were insignificant and amounted to a maximum of0.6 C. A slightly higher teq was determined for the variant with air supplied at 22 C. As shown in Fig. 6a) and b), in the case of air supplied from PV at 24 C, the airflow rises quickly and does not fully reach the thermal manikin, whereas the airflow at 22 C reaches the manikin and its breathing zone to a greater extent. A similar situation can be observed for variants with the breathing switched on. The differences in teq for variants with air supplied at 22 C or 24 C were up to 0.8 C. Again, the airflow having the temperature of 22 C had a greater influence on the manikin's surface; hence teq is higher, particularly in the upper segments of the manikin. Significant differences were noted between the variants with the manikin's breathing function being switched on or switched off. The differences occurred on the majority of segments, except for the hands and the feet. The greatest differences were observed for the following body parts: arms, shoulders, torso and thighs (differences were up to 2.7 C maximum for both variants of the air temperature from the PV system). The differences in the distribution of air supplied from the PV air terminal device can be observed in Fig. 6a) and b). A more intensive air movement in the area of the thermal manikin's torso was observed when the breathing function was switched on. At the same time, the impact of the air supplied from PV onto the manikin tended to decrease. For this type of setup of the air terminal device operating in a heating option, the influence of breathing was higher for air supplied from the PV with temperature equal to 22 C, rather than 24 C.Furthermore, it was observed that the breathing process had a significant influence on the values of teq and its influence was higher than the changes in temperature of the PV air supply. In the case of an air terminal device in variant II operating in a heating option for non-breathing mode, the results of teq significantly vary, depending on the temperature of air supplied from PV (Fig. 7). The setup of the shutters caused the airflow to be narrower.
As a result, the airflow reached the surface of the thermal manikin to a larger extent than the case of air terminal device I, which caused a greater dependence of teq on the temperature of the supplied air for the non-breathing variants. This effect can be observed in Fig. 6 c) and d). The differences in teq between 20/22/nb and 20/24/nb variants are up to 1.9 C, whereas in the upper segments of the thermal manikin, those differences range from 1 to 1.5 C. Turning on the breathing option reduces the impact of the airflow from PV on the manikin. As a result, the values of teq for air supplied from the PV at the temperature 22 C and 24 C are similar on all the segments. The maximum temperature difference between the segments is 0.5 C. At the same time, the difference in teq between breathing and non-breathing variants for air supplied from PV with the temperature equal to 22 C is up to 5.0 C, whereas for air temperature equal 24 C, it is even up to 3.8 C. It can therefore be concluded that breathing, in the case of personalised ventilation, has a significant impact on teq and the thermal environment in the vicinity of the thermal manikin. In the case of this air terminal device, the use of a breathing process caused an increase of the PV airflow above the breathing zone of the thermal manikin. In the case of air terminal device III, the supplied airflow is spreading vertically. As a result, it can again be observed that the airflow from PV at 24 C reaches the thermal manikin to a smaller extent than at 22 C. Such a phenomenon is attributable to the fact that air having the temperature of 24 C bends up quicker towards the top and does not reach the thermal manikin's breathing zone (Fig. 6 e) and f)). For this reason, as shown in Fig. 8, teq for nonbreathing variants was higher for air supplied at 22 C. This difference, amounting to 1.2 C at maximum, is most noticeable on the upper segments of the thermal manikin. At the same time, the standard deviation for air supplied at 22 C is significantly smaller than for air at 24 C. Turning the breathing option on stabilises the airflow around the thermal manikin. In consequence, the temperature of supplied air is of secondary importance and has a
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Fig. 6. Airflow distribution for IeIV air terminal device variants in the case of nonbreathing (light grey colour) and breathing (dark grey colour) modes for the PV operating in a heating option (ambient temperature of 20 C and air supply temperature of 22 or 24 C).
secondary impact on teq for particular segments e differences in teq are up to 0.5 C. At the same time, the standard deviation for breathing variants is significantly lower than for non-breathing variants. In the case of air terminal device IV, the airflow narrows vertically, which results in a higher concentration of the supplied airflow. In the case of non-breathing variants, teq for both options of air supplied temperature was similar and remained within the standard deviation of both variants (the maximum difference up to
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1.3 C). The supplied air of 24 C caused a slightly higher value of teq on the upper segments of the thermal manikin and the air supplied at 22 C caused a slightly higher value on the lower segments (Fig. 9). When the breathing function was switched on, teq on the majority of segments was practically the same, regardless of the temperature of supplied air. Slight differences can only be observed on the upper segments of the thermal manikin (up to 0.6 C). All of the results remain within the standard deviation. As can be clearly seen in Fig. 5h), when the breathing process is switched on, air supplied from PV rises and does not reach the surface of the thermal manikin. It can be therefore concluded that teq is dependent on the stream of breathing air, rather than airflow from PV. The situation is different for PV operating under a cooling option. In the case of air terminal device I, the differences between teq for non-breathing variants are significant (Fig. 10). With the breathing option switched on, a higher teq was obtained for air supplied at 20 C rather than 22 C. The differences in teq reached up to 2 C. Air stream supplied from PV at 20 C had a shorter range and tended to fall more rapidly, failing to fully reach the surface of the thermal manikin. As a result of turning the breathing function on, teq became more independent from the air supplied from PV, and teq levelled out on particular segments. Differences between teq with the breathing option on for both temperatures of supplied air were noted mainly on the upper parts of the thermal manikin's segments, whereas for the remaining segments, they remained within the standard deviation. Fig. 11a) and b) presents distribution of air for air terminal device I in particular variants. In the case of the air terminal device II, for which the air supplied from PV is more concentrated, teq for non-breathing variants was more similar than was the case for the air terminal device I (Fig. 12). Slight differences were only noted for the following segments: face, head and from the upper chest to thighs; however, they remained within the standard deviation. As seen in Fig. 11c) and d), in the case of this air terminal device, the airflow distribution without breathing is similar, irrespective of the temperature of delivered air. As a result of switching the breathing process on, teq decreased by as much as3.7 C. A decrease was noted on all the segments, except for the feet, where teq slightly increased. Again, the values of teq in the breathing variant were similar, irrespective of the temperature of air supplied from the PV, and greater differences were noted only for the following segments: face, head, upper chest, and shoulders. For air supplied from PV at 20 C, the airflow bent downward in the lower part of the thermal manikin. In the case of the air terminal device III, in which the airflow is spreading vertically, the situation is similar to the one for air terminal device I. In the case of the non-breathing variants, the values of teq are higher for air supplied at 20 C (Fig. 13), in which the air supplied from the PV does not fully reach the surface of the thermal manikin. This situation is shown in Fig. 11 e) and f). An introduction of breathing resulted in significant lowering of teq on the majority of the segments. At the same time, teq was similar on the lower segments of the thermal manikin for air supplied from PV at 22 C and 20 C, whereas it significantly differed on the face, head and upper chest. teq for air supplied at 22 C was higher than for 20 C. In the case of air terminal device IV, the airflow is narrow and concentrated vertically. In consequence, a bigger mass reaches the thermal manikin (Fig. 11g) and h)). Airflow from the PV for nonbreathing variants with air supplied at 22 C reaches the manikin's face, and in the case of air supplied at 20 C, it quickly decreases and reaches mainly the manikin's torso. For this reason, differences in teq for the non-breathing variant were observed up from the upper chest, shoulders, stomach down to the thighs (Fig. 14). On the other segments, teq remained similar. For the majority of segments, however, the differences did not exceed the
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Fig. 7. Equivalent temperature for air terminal device variant II operating in a heating option.
Fig. 8. Equivalent temperature for air terminal device variant III operating in a heating option.
standard deviation for both variants. Introduction of a breathing variant resulted again in a significant reduction of teq, and in the case of air supplied at 20 C, an even more rapid reduction towards the lower parts of the thermal manikin was noted. This phenomenon caused differences in teq observed on the upper segments of the thermal manikin, composed of its head and torso. On the remaining segments, the results were similar or remained within
the standard deviation. A comparison of mean teq for the entire thermal manikin (calculated as the surface segments weighted average) captures the global differences between non-breathing and breathing variants. For the heating function in the 20/22/nb variants, the mean teq value ranged between 21.0 C and 22.3 C for different setups (IeIV) of the air terminal device. The introduction of breathing resulted in
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Fig. 9. Equivalent temperature for air terminal device variant IV operating in a heating option.
Fig. 10. Equivalent temperature for air terminal device variant I operating in a cooling option.
a decrease of the mean teq value, which ranged between 19.4 C and 19.8 C. In the 20/24/nb variants the mean teq value ranged from 21.0 C to 21.8 C, and for the same temperature variants with the breathing function on the obtained values remained within the range of 19.5 C e 19.9 C. In the case of the PV working under the cooling option for the 24/22/nb variants, the mean teq value ranged from 23.8 C to 24.7 C, whereas under the breathing variants, the
value ranged from 22.8 C to 22.9 C. In the case of 24/20/nb variants, the teq values ranged from 24.2 C to 24.7 C, whereas in the 24/20/b variants, the values ranged from 22.4 C to 22.8 C.
4. Discussion and conclusions Based on the survey, exhaled air jets were found to have the
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1. Depending on the type of the air terminal device, the airflow from the PV reached, to a larger or smaller extent, the surface of the thermal manikin and influenced the teq value. For this reason, the impact of breathing on teq was conditioned by the type of the air terminal device. 2. Streams of the respiratory air of the thermal manikin influenced the direction of the air supplied from the PV and, in the case of a heating option, caused the air to lift more rapidly, resulting in a smaller volume of PV air reaching the thermal manikin. In the case of a cooling option, these streams caused a more rapid decrease of air for the air supplied from the PV at 20 C. 3. teq for the non-breathing variants and with different temperatures of air supplied from the PV varied to a larger or smaller degree, depending on the test variant. Greater differences were noted in the case of cooling mode than in the case of PV operating in a heating mode. 4. Introduction of a breathing process caused reduction of the teq value in relation to non-breathing variants. The greatest decrease of teq was noted for the 20/22 variant and the air terminal device II (reduction of mean teq value for the entire manikin by 2.6 C), whereas the smallest decrease was found for the 24/22 variant and air terminal devicesI and III (reduction of mean teq value for the whole manikin by 0.9 C). 5. The values of teq in the case of breathing variants at various air temperatures supplied from PV were similar or the same. The changes were mainly noted on the segments of upper arm and upper thigh for the PV operating in a heating mode, and the changes were found on the head, upper chest and shoulders for PV in a cooling mode. The airflow inhaled/exhaled by man has a short range but considerable air velocity, and the temperature is usually higher than the ambient air temperature, thereby affecting the airflow in the human convective boundary layer. The test results are consistent with the results obtained by Bjorn and Nielsen [23], who determined that the exhaled air can penetrate the thermal plume and Impose exposure to the other manikin standing at 0.4 m away, € as well as the results of Melikov and Kaczmarczyk [24] and of Ozcan
Fig. 11. Airflow distribution for IeIV air terminal device variants in the case of nonbreathing (light grey colour) and breathing (dark grey colour) modes for the PV operating in a cooling option (ambient temperature 24 C and air supply temperature 22 or 20 C).
potential to influence the value of the equivalent temperature, thereby affecting the users' heat sensation. In every variant, after the turning on of the manikin breathing process, the decrease of teq was observed compared to the variant without the breathing process on, and the environment experienced by the user was found to be cooler. The following are more detailed conclusions resulting from the research:
et al. [25], who indicated that the jets expired from the nostrils of a seated breathing manikin could break the thermal boundary layer. The thickness of the convective boundary layer depends on a body part, as described by, but it is usually approximately 5 cm [6,7], so that the inhaled/exhaled airflow with velocity greater than 2 m/s is able to pass through this layer and consequently also affects the thermal perception by humans. This information is particularly important for the design of ventilation and air conditioning systems that shape the parameters of the environment in the vicinity of human body. The conducted studies provide sufficient grounds to conclude that streams of respiratory air have a greater influence on teq than air temperature supplied from the PV in relation to the indoor air temperature. Both in a heating and cooling option, teq tended to decrease significantly. At the same time, the values of teq were similar for variants with different air temperatures supplied from the PV. It can be therefore assumed that the breathing process has a significant impact on the perception of the indoor thermal environment using the PV system. The air exhaled by the thermal manikin affected the distribution of air from the PV and caused the flow direction to change. This process stems from a relatively small velocity of air delivered from the PV in relation to the air velocity in the human respiratory stream. In the case of studies presented within this publication, in the first stage, air terminal devices had the construction adjusted to the users' subjective feelings. The minimum volume of hygienic air was assumed in accordance with ASHRAE [29]; however, the size of the air terminal device was
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Fig. 12. Equivalent temperature for air terminal device variant II operating in a cooling option.
Fig. 13. Equivalent temperature for air terminal device variant III operating in a cooling option.
established during the tests with human subjects, so that air velocity reaching the human's body was 0.25 m/s at the maximum. The majority of publications on PV only indicated the values of the airflow volume used for the tests. However, taking into consideration the size of the PV air terminal devices, it can be assumed that air velocities were higher than 0.25 m/s in the user breathing zone. Air velocities amounting to approximately 0.4 m/s at the
outflow from PV terminal devices were observed, in our case, to be uncomfortable for the users. It was determined that the air supplied from PV at the assumed velocity collided with the air exhaled by the thermal manikin. Furthermore, it was observed that only the case of PV the cooling mode had an impact on the indoor thermal environment perceived by the user. The presented studies revealed the problem of the proper
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Fig. 14. Equivalent temperature for air terminal device variant IV operating in a cooling option.
determination of the air velocities supplied from the PV. On one hand, every attempt should be made to maintain the highest level of air quality; hence, the air delivered from the PV should induce indoor air as little as possible. On the other hand, the air velocity cannot be too high due to the users' thermal sensation. At the same time, it is important to bear in mind the influence of the human breathing process on the airflow from the PV. Acknowledgement The studies were developed on the basis of research work conducted within the project no. N R04 0018 10 financed by the National Centre for Research and Development in the years 2011e2015. References [1] P.O. Fanger, Thermal Comfort, McGraw-Hill, New York, USA, 1970. [2] K. Parson, Human Thermal Environments. The Effects of Hot, Moderate and Cold Environments on Human Health, Comfort and Performance, Taylor&Francis, 2003. [3] S. Tanabe, M. Haneda, N. Nishihara, Workplace productivity and individual thermal satisfaction, Build. Environ. 91 (2015) 42e50. [4] S. Karjalainen, O. Koistinen, User problems with individual temperature control in offices, Build. Environ. 42 (2007) 2880e2887. [5] A. Melikov, Human body micro-environment: the benefits of controlling airflow interaction, Build. Environ. 91 (September 2015) 70e77. [6] D. Licina, J. Pantelic, A. Melikov, Sekhar Ch, K.W. Tham, Experimental investigation of the human convective boundary layer in a quiescent indoor environment, Build. Environ. 75 (May 2014) 79e91. [7] D. Licina, A. Melikov, Sekhar Ch, K.W. Tham, Air temperature investigation in microenvironment around a human body, Build. Environ. 92 (October 2015) 39e47. [8] N. Gao, J. Niu, CFD study on micro-environment around human body and personalized ventilation, Build. Environ. 39 (2004) 795e805. [9] D. Zukowska, A. Melikov, Z. Popiolek, Impact of personal factors and furniture arrangement on the thermal plume above a sitting occupant, Build. Environ. 49 (March 2012) 104e116. [10] E. Mundt, Displacement ventilation systems e convection flows and temperature gradients, Build. Environ. 30 (1) (1995) 129e133. [11] A. Bogdan, M. Chludzinska, Comparative evaluation of thermal plumes formed above a thermal manikin and humans e the pilot study results, in:
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