- Email: [email protected]
Performance characteristics of a pad evaporative cooling system in a broiler house in a Mediterranean climate
biosystems engineering 103 (2009) 100–104
Available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/issn/15375110
Research Paper: SEdStructures and Environment
Performance characteristics of a pad evaporative cooling system in a broiler house in a Mediterranean climate Metin Dag˘tekina, Cengiz Karacab,*, Yılmaz Yıldızb a
C¸ukurova University, Ceyhan Vocation High Scholl, Ceyhan, Adana, Turkey C¸ukurova University, Faculty of Agriculture, Dept of Agric. Machinery, 01330 Adana, Turkey
b
article info Temperatures in Mediterranean regions frequently exceed 30 C for long periods during Article history:
summers. Pad evaporative cooling systems may provide a solution for controlling the high
Received 14 November 2007
temperatures that can negatively affect poultry houses. This research, aiming to investi-
Received in revised form
gate the performance characteristics of evaporative pad cooling systems for the Mediter-
15 January 2009
ranean region of Turkey, was carried out in a typical poultry house from18 July to 3 August
Accepted 16 February 2009
2006. Average evaporative cooling efficiency was determined as 69.2% on July 18, 70.1% on July 19, 69.4% on July 25, 70.8% on July 29 and 72.0% on August 3. The temperature decrease in pad exit during the experiment was determined as 6.1 C, 7.3 C, 4.4 C, 5.0 C and 5.9 C, respectively. ª 2009 IAgrE. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
Animals and plants raised in enclosed spaces in hot climatic conditions are susceptible to heat stress. As a result, agricultural and horticultural businesses in these environments can experience serious economic losses. A number of methods are available to protect animals and plants from heat stress due to increases in temperature and to provide optimal growing conditions. Of these methods the evaporative pad cooling system is the most common. In pad-based evaporative cooling systems, warm air extracted from the surrounding, passed through a wet pad and then released into the interior of the building. An amount of water on the surface of the pad is vaporised and enters into the area to be cooled with the expelled air. Depending on the temperature of the air being pulled through the pad as the water vaporises, the dry bulb temperature of the air entering the area drops. The efficiency of evaporative pad systems is affected by number of factors including the type of material used in the
pad, its thickness and surface area, and the size of the perforations. Efficiency is also affected by the volume of water used, the relative humidity and the flow rate of air passing through the pad (Anonymous, 1983; McNeill et al., 1983; Koca et al., 1991; Simmons and Lott, 1996). The Mediterranean region of Turkey is an important area for agricultural production with high daytime temperatures regularly rising above 30 C for long periods between June and September. During this period, the temperature of the interior of buildings used for poultry houses and greenhouses can become unsuitable for production. Similarly, the relative humidity varies from 40% to 90%. Because of the opposing relationship between temperature and relative humidity, when temperature is at a maximum between 8:00AM and 7:00PM, humidity falls well below its saturation point. Both these factors can have a negative effect for growing animals and plants. Therefore, in order to reduce the interior temperatures, evaporative cooling systems are utilised to mitigate heat stress. As a result, over the last decade, there has been a marked increase in the use of evaporative pad
* Corresponding author. E-mail address: [email protected] (C. Karaca). 1537-5110/$ – see front matter ª 2009 IAgrE. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biosystemseng.2009.02.011
101
biosystems engineering 103 (2009) 100–104
Nomenclature h tkd tki
Cooling efficiency (%) Dry bulb temperature of the air entering the pad ( C) Dry bulb temperature of the air leaving the pad ( C)
cooling systems Dag˘tekin and Yıldız (1997), evaluated alternative cooling methods for poultry houses in the Mediterranean region and determined 3 C–7 C temperature decrease inside poultry by using pad-based evaporative cooling system. Ug˘urlu and Kara (1998), measured between 77% and 90% efficiency in a pad system and between 4.2 C and 16.2 C temperature drops inside the poultry in Konya (Central Anatolia). However, there is insufficient research on pad cooling that relates to the Mediterranean region of Turkey. Thus, the efficiency of a pad evaporative cooling system installed in a commercial broiler house in a Mediterranean climate is reported in this paper.
2.
Materials and methods
2.1.
Materials
Wet bulb temperature of the air entering the pad ( C) Temperature of the air entering the pad ( C) Humidity of the air entering the pad (%) Temperature of the air leaving the pad ( C) Humidity of the air leaving the pad (%) Temperature decrease ( C)
ti 4i to 4o Dt
the floor of the facility, thus the water temperature did not vary significantly (18 C–19 C). The cooling system included 6 exhaust fans, each 1.27 m in diameter with maximum air capacities of 42,000 m3 h1. The fans were activated by slip hoop. Four fans exhausted through the north wall; the other two were positioned on the east and west walls, close to the north wall (Fig. 1). The measurement and data logging system used in the study was a DL2e (Delta-T Devices Ltd., Cambridge, UK).
2.2.
Methods
During the study, manual temperature control, which was preferred by the owner instead of automatic thermostatic control, was used. The study area was selected by the staff in charge of the facility. Airflow measurements were taken at selected diagonal locations across each pad and the average velocity of air passing through the pads was calculated. Eq. (1) below was utilised to determine the cooling efficiency of system (Ashrae, 1983; Koca et al., 1991; Simmons and Lott, 1996; Ug˘urlu and Kara, 1998) h¼
tkd tki 100 tkd tyd
(1)
where h is cooling efficiency (%) and tkd, tki, tyd are the dry bulb temperature of the air entering the pad, the dry bulb temperature of the air exiting the pad and the wet bulb temperature of the air entering the pad ( C), respectively. The dry bulb temperature and relative humidity measurements were taken at the east facing wall on centrally located pad. Therefore, sensors were placed in close proximity
Air temperature (°C)
18 July 2006 50
100
45
90
40
80
35
70
30
60
25
50 40
20 15 10 09:00
ti φi
to φo
30 20
10:30
12:00
13:30
15:00
16:30
18:00
Time (h)
Fig. 1 – A schematic diagram of the fans, pads and measurement points in the poultry house.
Fig. 2 – Temperature (t) and relative humidity (4) measurements for air entering (i) and leaving (o) the pads at minimum speed on the first test day.
Air relative humidity (%)
The poultry house examined in this study was located near Adana and was 50 m above sea level (latitude 37 090 N; longitude 35 270 E). The 85 12 m poultry house had a capacity of 15,000 hens and was orientated in north-south direction. The foundations and plastered walls of the poultry were 150 mm thick and made from concrete. The ceiling was covered with 80 mm thick aluminium coated polystyrene foam. The building had a controlled airflow. In this study, 100 mm thick pads (CELdek R 7060-15, Munters AB, Kista, Sweden) made from cellulose were used. The pads were inclined at an angle of 45 above and 15 below horizontal and had been in use in the building since 2001. The pads were positioned along the long east and west walls of the building (Fig. 1). On each wall, there were 5 pads each 2.6 1.9 m in size. The pads were wetted from the pipes that were positioned above them. A concrete water sump had been placed under
tyd
102
biosystems engineering 103 (2009) 100–104
Air temperature (°C)
90
40
80
35
70
30
60
25
50
20 15 10 09:00
40
ti φi
to φo
30 20
10:30
12:00
13:30
15:00
16:30
18:00
12:00
13:30
Cooling efficiency (%)
11 10 9 8 7 6 5 4 3 2
15:00
16:30
Temp. decreasing (°C)
10:30
80
35
70
30
60
25
50
20 15
40 30 20
to the surfaces of the pads at which air was entering (A) and exiting (B) (Fig. 1). Dry bulb temperature and relative humidity were measured, by OMEGA-HHF710, Digital Hygro-Thermometer Anemometer (0.01 m s1). The evaporative cooling efficiency, determined by wet bulb temperature, was measured by psychrometric diagram related to dry bulb temperature and relative humidity of an outer surface of pads (Eq. 1).
3.
Results and discussion
18:00
Time (h) Fig. 4 – Evaporative cooling efficiency (h) and temperature decrease (Dt) of air passing through the pads at minimum speed on the first test day.
Measurements were made between 18 July and 3 August 2006. As some fans were in a neglected state, the shutters of some fans did not open fully. Thus, the highest air velocity recorded passing through the fans was less than 1.41 m s1 with lowest of 1.28 m s1. On the first test day (July 18), the fans of the cooling system ran at their lowest speed but on the following days, when temperature and relative humidity measurements were taken, air speed was at a maximum. Temperature and humidity measurements were taken as air entered the pads (o) and as it left the pads (i) (Figs. 2 and 3).
19 July 2006
25 July 2006 100
11
90
9
90
10
80
8
80
9
70
7
8
60
6
70
50
5
60
7
50
6
40
5
40
4
30
3 η
20 10 09:00
Δt
2 1
10:30
12:00
13:30
15:00
16:30
18:00
Time (h) Fig. 5 – Evaporative cooling efficiency (h) and temperature decrease (Dt) of air passing through the pads at maximum speed on the second test day.
Cooling efficiency (%)
10
4
30 20
η
Δt
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
Tempr. decreasing (°C)
100
Tempr. decreasing (°C)
Cooling efficiency (%)
ti φi
to φo
Fig. 6 – Temperature (t) and relative humidity (4) of air entering (i) and leaving (o) the pad on the third test day.
18 July 2006
Δt
90
40
Time (h)
Fig. 3 – Temperature (t) and relative humidity (4) measurements of air entering (i) and leaving (o) the pads at maximum speed on the second test day.
η
100
45
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
Time (h)
100 90 80 70 60 50 40 30 20 10 09:00
25 July 2006
Air relative humidity (%)
45
50
Air relative humidity (%)
100
Air temperature (°C)
19 July 2006
50
3 2
Time (h) Fig. 7 – Evaporative cooling efficiency (h) and temperature decrease (Dt) for the third test day.
103
biosystems engineering 103 (2009) 100–104
45
90
40
80
35
70
30
60
25
50
20 15
ti φi
to φo
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
40 30
3 August 2006
Air temperature (°C)
100
20
Fig. 8 – Temperature (t) and relative humidity (4) of air entering (i) and leaving (o) the pad for the fourth test day.
From 9:00AM to 7:30PM, temperature and humidity of air entering pads (from the outside) and leaving showed similarities according to the time of day. However, the humidity on the July 18 was approximately 5% higher than the July 19, and temperatures were approximately 1 C lower. This can be seen more clearly in Figs. 2 and 3 between 11:30AM and 5:00PM. On each of the two days of the test, the air velocities recorded were similar close. Therefore, air temperature and relative humidity did not show any significant difference. The evaporative efficiency and temperature changes of the air passing trough the pad can be seen in Figs. 4 and 5 for the dates of July 18 and 19. The evaporative cooling efficiency for both days was fairly similar and on average, was around the 70%. As stated above, in each of the two tests, the flow speeds of air passing through the pads were quite similar. However, the evaporative cooling efficiency of the air was significantly different (P < 0.05). The changes of temperature and relative humidity values entering and leaving the pad on the July 25, were given in Fig. 6. While the temperature entering pad varied from 27 C to 33 C, it varied from 25 C to 27 C when leaving, inlet and outlet relative humidity fluctuated from 54% to 80% and 86%– 92%, respectively. The evaporative cooling efficiency varied from 60% to 79% and the decrease in temperature due to passing air through the pads varied between 2 C and 6 C (Fig. 7).
9 8 7 6
40
5
30 20
4 η
t
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
80
35
70
30
60
25
50
20
40
15
30
3 2
Time (h) Fig. 9 – Evaporative cooling efficiency (h) and temperature decrease (Dt) for the fourth test day.
20
Time (h) Fig. 10 – Temperature (t) and relative humidity (4) of air entering (i) and leaving (o) the pad for the fifth test day.
The changes in temperature and relative humidity values entering and leaving the pad for July 29 are shown in Fig. 8. While temperatures entering the pad varied from 26 C to 34 C they varied from 25 C to 27 C on exit; inlet and outlet relative humidity varied from 48% to 86% and 53%–96%, respectively. The evaporative cooling efficiency was 57%–82% and the decrease in temperature was 2 C–7 C (Fig. 9). The changes of temperature and relative humidity values entering and leaving the pad on the August 3 are shown in Fig. 10. The temperature entering the pad varied from 22 C to 35 C and 22–27 C on exit; relative humidity entering and leaving the pad was 39%–85% and 82%–93%, respectively. The calculated evaporative cooling efficiency and temperature decrease values for the August 3 are shown in Fig. 11. The evaporative cooling efficiency was 47%–84% during the measurement period and the temperature decrease was 2 C–9 C. Between 1:30PMand 4:00PM when the external temperature was high and relative humidity was low, pads provided approximately a 9 C drop. The evaporative cooling efficiencies were 69.2% on July 18, 70.1% on July 19, 69.4% on July 25, 70.8% on July 29 and 72.0% on August 3 while the temperature drops at pad exit were 6.1 C, 7.3 C, 4.4 C, 5.0 C and 5.9 C, respectively (Table 1).
Cooling efficiency (%)
70
Tempr. decreasing (°C)
Cooling efficiency (%)
11 10
50
40
100
80 60
90
3 August 2006
11
90
10
80
9
70
8
60
7
50
6
40
5
30 20
4 η
t
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
3
Tempr. decreasing (°C)
90
100
45
φi φd ti to 10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
Time (h)
29 July 2006
50
Air relative humidity (%)
Air temperature (°C)
29 July 2006
Air relative humidity (%)
50
2
Time (h) Fig. 11 – Evaporative cooling efficiency (h) and temperature decrease (Dt) for the fifth test day.
104
biosystems engineering 103 (2009) 100–104
Table 1 – Average values of evaporative cooling efficiency and temperature Days
Drop in temperature ( C)
Cooling efficiency (%)
18 July, 2006 19 July, 2006 25 July, 2006 29 July, 2006 3 August, 2006
Minimum
Maximum
Average
Minimum
Maximum
Average
31.8 67.3 59.1 58.0 47.7
83.7 75.5 75.6 79.6 81.7
69.2 70.1 69.4 70.8 72.0
3.6 3.3 2.0 1.7 1.3
7.3 8.9 5.8 7.0 8.9
6.1 7.3 4.4 5.0 5.9
The live weight per unit area of the poultry house when cooling system was operating was 18.84 kg m2 on July 18, and 31.67 kg m2 on August 3. Heat emissions (both sensible and latent heat) into by the hens were changing on their weight increase. Therefore, evaporative cooling systems should not be expected to be as effective as in preventing heat stress with low weight gain hens than with high weight gain hens.
reduce the negative effects of heat stress on the efficiency of feed conversion, weight gain rate and mortality. Therefore, evaporative cooling systems can be recommended for sustainable poultry production in the Mediterranean region as a supportive component for lowering the temperature during hot summer months.
references
4.
Conclusions
Results obtained on the July 18 and 19, between 9:00AM and 7:00PM, temperature and humidity entering the pad from outside displayed marked similarities according to the time of day. Therefore, on both days the evaporative cooling efficiency was approximately 70% with similar variations of temperature and humidity. During the tests, the velocity of the air passing through the pads was quite similar (1.28 m s1–1.41 m s1). But, statistically the effect air speed on the evaporative cooling efficiency and temperature were significant (P < 0.05). The averages of evaporative cooling efficiency varied from 70% to 72% and temperature decrease varied from 4.4 C to 7.3 C. The summer daytime temperatures in the Mediterranean region vary from 25 C to 42 C while relative humidity in early morning and evening exceeds 80%. Evaporative cooling may be considered as being ineffective at high relative humidity. However, when relative humidity falls below 50% during the day as temperatures increase, evaporative cooling systems can be used to lower the temperature of buildings. In previous studies Kocatu¨rk and Yildiz (2007) and Koc¸ and Yildiz (2007) showed 3 C to 12 C reductions in temperatures. This study showed that in the Mediterranean region temperatures inside poultry houses could be lowered by 9 C with pad cooling systems. Although it is impossible to reach the optimal temperature requirements of hens in the poultry houses with these temperature values, evaporative cooling may help
Anonymous (1983). Ventilation of agricultural structures. In: ASAE Monograph, Number: 6 (Mylo A; Hellickson.; Walker John N eds). St. Joseph, Michigan. Ashrae (1983). Equipment Handbook. American Society of Heating, Refrigerating and Air-Conditioning Engineering, New York. Dag˘tekin M; Yıldız Y (1997). Alternative Cooling Systems on Broiler Houses in Turkey Conditions. In: Livestock Environment V, Volume I, Proceeding of the Fifth International Symposium, Bloomington, Minnesota, 386–392. Koca R W; Hughes W C; Christianson L L (1991). Evaporative cooling pads: test procedure and evaluation. Transactions of the ASAE, 7(4), 485–490. ¨ ; Yildiz Y (2007). Some performance characteristics of Kocatu¨rk U evaporative cooling pad at three air velocities in c¸ukurova regions. J. Agric. Fac. C¸ukurova Univ, 21(4), 101–108, Adana/ Tu¨rkiye. Koc¸ N; Yildiz Y (2007). Some Performance Characteristics of Evaporative Cooling Pad at Three Water Flow Rates Through the Pad in C¸ukurova Regions. Agricultural Mechanization 24th National Congress, Proceeding Book, pp. 337–334, Kahramanmarasx /Tu¨rkiye. McNeill S G; Fehr R L; Walker J N; Parker G R (1983). Performance of evaporative coolers for mid-south gestation housing. Transactions of the ASAE, 26(1), 219–222. Simmons J D; Lott B D (1996). Evaporative cooling performance resulting from changes in water temperature. Applied Engineering in Agriculture, 12(4), 497–500. Ug˘urlu N; Kara M (1998). The cooling performance of wet pads and their effect on reduction of the inside temperature a cage house. Turkish Journal of Agriculture and Forestry, 24(2000), 79–86.
Available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/issn/15375110
Research Paper: SEdStructures and Environment
Performance characteristics of a pad evaporative cooling system in a broiler house in a Mediterranean climate Metin Dag˘tekina, Cengiz Karacab,*, Yılmaz Yıldızb a
C¸ukurova University, Ceyhan Vocation High Scholl, Ceyhan, Adana, Turkey C¸ukurova University, Faculty of Agriculture, Dept of Agric. Machinery, 01330 Adana, Turkey
b
article info Temperatures in Mediterranean regions frequently exceed 30 C for long periods during Article history:
summers. Pad evaporative cooling systems may provide a solution for controlling the high
Received 14 November 2007
temperatures that can negatively affect poultry houses. This research, aiming to investi-
Received in revised form
gate the performance characteristics of evaporative pad cooling systems for the Mediter-
15 January 2009
ranean region of Turkey, was carried out in a typical poultry house from18 July to 3 August
Accepted 16 February 2009
2006. Average evaporative cooling efficiency was determined as 69.2% on July 18, 70.1% on July 19, 69.4% on July 25, 70.8% on July 29 and 72.0% on August 3. The temperature decrease in pad exit during the experiment was determined as 6.1 C, 7.3 C, 4.4 C, 5.0 C and 5.9 C, respectively. ª 2009 IAgrE. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
Animals and plants raised in enclosed spaces in hot climatic conditions are susceptible to heat stress. As a result, agricultural and horticultural businesses in these environments can experience serious economic losses. A number of methods are available to protect animals and plants from heat stress due to increases in temperature and to provide optimal growing conditions. Of these methods the evaporative pad cooling system is the most common. In pad-based evaporative cooling systems, warm air extracted from the surrounding, passed through a wet pad and then released into the interior of the building. An amount of water on the surface of the pad is vaporised and enters into the area to be cooled with the expelled air. Depending on the temperature of the air being pulled through the pad as the water vaporises, the dry bulb temperature of the air entering the area drops. The efficiency of evaporative pad systems is affected by number of factors including the type of material used in the
pad, its thickness and surface area, and the size of the perforations. Efficiency is also affected by the volume of water used, the relative humidity and the flow rate of air passing through the pad (Anonymous, 1983; McNeill et al., 1983; Koca et al., 1991; Simmons and Lott, 1996). The Mediterranean region of Turkey is an important area for agricultural production with high daytime temperatures regularly rising above 30 C for long periods between June and September. During this period, the temperature of the interior of buildings used for poultry houses and greenhouses can become unsuitable for production. Similarly, the relative humidity varies from 40% to 90%. Because of the opposing relationship between temperature and relative humidity, when temperature is at a maximum between 8:00AM and 7:00PM, humidity falls well below its saturation point. Both these factors can have a negative effect for growing animals and plants. Therefore, in order to reduce the interior temperatures, evaporative cooling systems are utilised to mitigate heat stress. As a result, over the last decade, there has been a marked increase in the use of evaporative pad
* Corresponding author. E-mail address: [email protected] (C. Karaca). 1537-5110/$ – see front matter ª 2009 IAgrE. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biosystemseng.2009.02.011
101
biosystems engineering 103 (2009) 100–104
Nomenclature h tkd tki
Cooling efficiency (%) Dry bulb temperature of the air entering the pad ( C) Dry bulb temperature of the air leaving the pad ( C)
cooling systems Dag˘tekin and Yıldız (1997), evaluated alternative cooling methods for poultry houses in the Mediterranean region and determined 3 C–7 C temperature decrease inside poultry by using pad-based evaporative cooling system. Ug˘urlu and Kara (1998), measured between 77% and 90% efficiency in a pad system and between 4.2 C and 16.2 C temperature drops inside the poultry in Konya (Central Anatolia). However, there is insufficient research on pad cooling that relates to the Mediterranean region of Turkey. Thus, the efficiency of a pad evaporative cooling system installed in a commercial broiler house in a Mediterranean climate is reported in this paper.
2.
Materials and methods
2.1.
Materials
Wet bulb temperature of the air entering the pad ( C) Temperature of the air entering the pad ( C) Humidity of the air entering the pad (%) Temperature of the air leaving the pad ( C) Humidity of the air leaving the pad (%) Temperature decrease ( C)
ti 4i to 4o Dt
the floor of the facility, thus the water temperature did not vary significantly (18 C–19 C). The cooling system included 6 exhaust fans, each 1.27 m in diameter with maximum air capacities of 42,000 m3 h1. The fans were activated by slip hoop. Four fans exhausted through the north wall; the other two were positioned on the east and west walls, close to the north wall (Fig. 1). The measurement and data logging system used in the study was a DL2e (Delta-T Devices Ltd., Cambridge, UK).
2.2.
Methods
During the study, manual temperature control, which was preferred by the owner instead of automatic thermostatic control, was used. The study area was selected by the staff in charge of the facility. Airflow measurements were taken at selected diagonal locations across each pad and the average velocity of air passing through the pads was calculated. Eq. (1) below was utilised to determine the cooling efficiency of system (Ashrae, 1983; Koca et al., 1991; Simmons and Lott, 1996; Ug˘urlu and Kara, 1998) h¼
tkd tki 100 tkd tyd
(1)
where h is cooling efficiency (%) and tkd, tki, tyd are the dry bulb temperature of the air entering the pad, the dry bulb temperature of the air exiting the pad and the wet bulb temperature of the air entering the pad ( C), respectively. The dry bulb temperature and relative humidity measurements were taken at the east facing wall on centrally located pad. Therefore, sensors were placed in close proximity
Air temperature (°C)
18 July 2006 50
100
45
90
40
80
35
70
30
60
25
50 40
20 15 10 09:00
ti φi
to φo
30 20
10:30
12:00
13:30
15:00
16:30
18:00
Time (h)
Fig. 1 – A schematic diagram of the fans, pads and measurement points in the poultry house.
Fig. 2 – Temperature (t) and relative humidity (4) measurements for air entering (i) and leaving (o) the pads at minimum speed on the first test day.
Air relative humidity (%)
The poultry house examined in this study was located near Adana and was 50 m above sea level (latitude 37 090 N; longitude 35 270 E). The 85 12 m poultry house had a capacity of 15,000 hens and was orientated in north-south direction. The foundations and plastered walls of the poultry were 150 mm thick and made from concrete. The ceiling was covered with 80 mm thick aluminium coated polystyrene foam. The building had a controlled airflow. In this study, 100 mm thick pads (CELdek R 7060-15, Munters AB, Kista, Sweden) made from cellulose were used. The pads were inclined at an angle of 45 above and 15 below horizontal and had been in use in the building since 2001. The pads were positioned along the long east and west walls of the building (Fig. 1). On each wall, there were 5 pads each 2.6 1.9 m in size. The pads were wetted from the pipes that were positioned above them. A concrete water sump had been placed under
tyd
102
biosystems engineering 103 (2009) 100–104
Air temperature (°C)
90
40
80
35
70
30
60
25
50
20 15 10 09:00
40
ti φi
to φo
30 20
10:30
12:00
13:30
15:00
16:30
18:00
12:00
13:30
Cooling efficiency (%)
11 10 9 8 7 6 5 4 3 2
15:00
16:30
Temp. decreasing (°C)
10:30
80
35
70
30
60
25
50
20 15
40 30 20
to the surfaces of the pads at which air was entering (A) and exiting (B) (Fig. 1). Dry bulb temperature and relative humidity were measured, by OMEGA-HHF710, Digital Hygro-Thermometer Anemometer (0.01 m s1). The evaporative cooling efficiency, determined by wet bulb temperature, was measured by psychrometric diagram related to dry bulb temperature and relative humidity of an outer surface of pads (Eq. 1).
3.
Results and discussion
18:00
Time (h) Fig. 4 – Evaporative cooling efficiency (h) and temperature decrease (Dt) of air passing through the pads at minimum speed on the first test day.
Measurements were made between 18 July and 3 August 2006. As some fans were in a neglected state, the shutters of some fans did not open fully. Thus, the highest air velocity recorded passing through the fans was less than 1.41 m s1 with lowest of 1.28 m s1. On the first test day (July 18), the fans of the cooling system ran at their lowest speed but on the following days, when temperature and relative humidity measurements were taken, air speed was at a maximum. Temperature and humidity measurements were taken as air entered the pads (o) and as it left the pads (i) (Figs. 2 and 3).
19 July 2006
25 July 2006 100
11
90
9
90
10
80
8
80
9
70
7
8
60
6
70
50
5
60
7
50
6
40
5
40
4
30
3 η
20 10 09:00
Δt
2 1
10:30
12:00
13:30
15:00
16:30
18:00
Time (h) Fig. 5 – Evaporative cooling efficiency (h) and temperature decrease (Dt) of air passing through the pads at maximum speed on the second test day.
Cooling efficiency (%)
10
4
30 20
η
Δt
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
Tempr. decreasing (°C)
100
Tempr. decreasing (°C)
Cooling efficiency (%)
ti φi
to φo
Fig. 6 – Temperature (t) and relative humidity (4) of air entering (i) and leaving (o) the pad on the third test day.
18 July 2006
Δt
90
40
Time (h)
Fig. 3 – Temperature (t) and relative humidity (4) measurements of air entering (i) and leaving (o) the pads at maximum speed on the second test day.
η
100
45
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
Time (h)
100 90 80 70 60 50 40 30 20 10 09:00
25 July 2006
Air relative humidity (%)
45
50
Air relative humidity (%)
100
Air temperature (°C)
19 July 2006
50
3 2
Time (h) Fig. 7 – Evaporative cooling efficiency (h) and temperature decrease (Dt) for the third test day.
103
biosystems engineering 103 (2009) 100–104
45
90
40
80
35
70
30
60
25
50
20 15
ti φi
to φo
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
40 30
3 August 2006
Air temperature (°C)
100
20
Fig. 8 – Temperature (t) and relative humidity (4) of air entering (i) and leaving (o) the pad for the fourth test day.
From 9:00AM to 7:30PM, temperature and humidity of air entering pads (from the outside) and leaving showed similarities according to the time of day. However, the humidity on the July 18 was approximately 5% higher than the July 19, and temperatures were approximately 1 C lower. This can be seen more clearly in Figs. 2 and 3 between 11:30AM and 5:00PM. On each of the two days of the test, the air velocities recorded were similar close. Therefore, air temperature and relative humidity did not show any significant difference. The evaporative efficiency and temperature changes of the air passing trough the pad can be seen in Figs. 4 and 5 for the dates of July 18 and 19. The evaporative cooling efficiency for both days was fairly similar and on average, was around the 70%. As stated above, in each of the two tests, the flow speeds of air passing through the pads were quite similar. However, the evaporative cooling efficiency of the air was significantly different (P < 0.05). The changes of temperature and relative humidity values entering and leaving the pad on the July 25, were given in Fig. 6. While the temperature entering pad varied from 27 C to 33 C, it varied from 25 C to 27 C when leaving, inlet and outlet relative humidity fluctuated from 54% to 80% and 86%– 92%, respectively. The evaporative cooling efficiency varied from 60% to 79% and the decrease in temperature due to passing air through the pads varied between 2 C and 6 C (Fig. 7).
9 8 7 6
40
5
30 20
4 η
t
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
80
35
70
30
60
25
50
20
40
15
30
3 2
Time (h) Fig. 9 – Evaporative cooling efficiency (h) and temperature decrease (Dt) for the fourth test day.
20
Time (h) Fig. 10 – Temperature (t) and relative humidity (4) of air entering (i) and leaving (o) the pad for the fifth test day.
The changes in temperature and relative humidity values entering and leaving the pad for July 29 are shown in Fig. 8. While temperatures entering the pad varied from 26 C to 34 C they varied from 25 C to 27 C on exit; inlet and outlet relative humidity varied from 48% to 86% and 53%–96%, respectively. The evaporative cooling efficiency was 57%–82% and the decrease in temperature was 2 C–7 C (Fig. 9). The changes of temperature and relative humidity values entering and leaving the pad on the August 3 are shown in Fig. 10. The temperature entering the pad varied from 22 C to 35 C and 22–27 C on exit; relative humidity entering and leaving the pad was 39%–85% and 82%–93%, respectively. The calculated evaporative cooling efficiency and temperature decrease values for the August 3 are shown in Fig. 11. The evaporative cooling efficiency was 47%–84% during the measurement period and the temperature decrease was 2 C–9 C. Between 1:30PMand 4:00PM when the external temperature was high and relative humidity was low, pads provided approximately a 9 C drop. The evaporative cooling efficiencies were 69.2% on July 18, 70.1% on July 19, 69.4% on July 25, 70.8% on July 29 and 72.0% on August 3 while the temperature drops at pad exit were 6.1 C, 7.3 C, 4.4 C, 5.0 C and 5.9 C, respectively (Table 1).
Cooling efficiency (%)
70
Tempr. decreasing (°C)
Cooling efficiency (%)
11 10
50
40
100
80 60
90
3 August 2006
11
90
10
80
9
70
8
60
7
50
6
40
5
30 20
4 η
t
10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
3
Tempr. decreasing (°C)
90
100
45
φi φd ti to 10 08:00 09:30 11:00 12:30 14:00 15:30 17:00 18:30
Time (h)
29 July 2006
50
Air relative humidity (%)
Air temperature (°C)
29 July 2006
Air relative humidity (%)
50
2
Time (h) Fig. 11 – Evaporative cooling efficiency (h) and temperature decrease (Dt) for the fifth test day.
104
biosystems engineering 103 (2009) 100–104
Table 1 – Average values of evaporative cooling efficiency and temperature Days
Drop in temperature ( C)
Cooling efficiency (%)
18 July, 2006 19 July, 2006 25 July, 2006 29 July, 2006 3 August, 2006
Minimum
Maximum
Average
Minimum
Maximum
Average
31.8 67.3 59.1 58.0 47.7
83.7 75.5 75.6 79.6 81.7
69.2 70.1 69.4 70.8 72.0
3.6 3.3 2.0 1.7 1.3
7.3 8.9 5.8 7.0 8.9
6.1 7.3 4.4 5.0 5.9
The live weight per unit area of the poultry house when cooling system was operating was 18.84 kg m2 on July 18, and 31.67 kg m2 on August 3. Heat emissions (both sensible and latent heat) into by the hens were changing on their weight increase. Therefore, evaporative cooling systems should not be expected to be as effective as in preventing heat stress with low weight gain hens than with high weight gain hens.
reduce the negative effects of heat stress on the efficiency of feed conversion, weight gain rate and mortality. Therefore, evaporative cooling systems can be recommended for sustainable poultry production in the Mediterranean region as a supportive component for lowering the temperature during hot summer months.
references
4.
Conclusions
Results obtained on the July 18 and 19, between 9:00AM and 7:00PM, temperature and humidity entering the pad from outside displayed marked similarities according to the time of day. Therefore, on both days the evaporative cooling efficiency was approximately 70% with similar variations of temperature and humidity. During the tests, the velocity of the air passing through the pads was quite similar (1.28 m s1–1.41 m s1). But, statistically the effect air speed on the evaporative cooling efficiency and temperature were significant (P < 0.05). The averages of evaporative cooling efficiency varied from 70% to 72% and temperature decrease varied from 4.4 C to 7.3 C. The summer daytime temperatures in the Mediterranean region vary from 25 C to 42 C while relative humidity in early morning and evening exceeds 80%. Evaporative cooling may be considered as being ineffective at high relative humidity. However, when relative humidity falls below 50% during the day as temperatures increase, evaporative cooling systems can be used to lower the temperature of buildings. In previous studies Kocatu¨rk and Yildiz (2007) and Koc¸ and Yildiz (2007) showed 3 C to 12 C reductions in temperatures. This study showed that in the Mediterranean region temperatures inside poultry houses could be lowered by 9 C with pad cooling systems. Although it is impossible to reach the optimal temperature requirements of hens in the poultry houses with these temperature values, evaporative cooling may help
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