Using an air cycle heat pump system with a turbocharger to supply heating for full electric vehicles

Accepted Manuscript Title: Using an air cycle heat pump system with a turbocharger to supply heating for full electric vehicles Author: Shuangshuang Li, Shugang Wang, Zhenjun Ma, Shuang Jiang, Tengfei Zhang PII: DOI: Reference:

S0140-7007(17)30099-3 http://dx.doi.org/doi: 10.1016/j.ijrefrig.2017.03.004 JIJR 3579

To appear in:

International Journal of Refrigeration

Received date: Revised date: Accepted date:

21-11-2016 13-2-2017 4-3-2017

Please cite this article as: Shuangshuang Li, Shugang Wang, Zhenjun Ma, Shuang Jiang, Tengfei Zhang, Using an air cycle heat pump system with a turbocharger to supply heating for full electric vehicles, International Journal of Refrigeration (2017), http://dx.doi.org/doi: 10.1016/j.ijrefrig.2017.03.004. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Using an air cycle heat pump system with a turbocharger to supply heating for full electric vehicles Shuangshuang Lia, Shugang Wanga,*, Zhenjun Mab, Shuang Jiang a, Tengfei Zhanga a Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, China b Sustainable Buildings Research Centre, University of Wollongong, Wollongong 2500, Australia

Comment [MGP1]: AUTHOR: There are two

Highlights:

version of Highlights section and one in the



A new air cycle heat pump system integrated with a turbocharger, a blower and a regenerated heat exchanger is developed.  A thermodynamic model for this system is first represented and the relationships between the system performance and the operating parameters are illustrated.  The performance of this system is numerically simulated and it can save more power than the PTC system under the same conditions for full electric vehicles.

manuscript has been used. Please confirm that this is correct.

Abstract Air cycle heat pump has large potentials in heating applications. However, a key challenge faced nowadays is the matching problem between its expander and compressor. This paper presents the performance evaluation of an air cycle heat pump system integrated with a turbocharger, a blower and a regenerated heat exchanger. A thermodynamic model for this system is first developed and the relationships between the system performance and the operating parameters are developed. Then, the performance of three different air cycle heat pumps with a blower installed before the compressor, and a blower installed before the turbine, and with an expander, are numerically simulated. The results indicated that the blower installed before the compressor can achieve a higher heating capacity and thus a higher COP. Finally, the heating power consumption of air cycle heat pump was compared with the PTC and the vapor compression heat pump of the full electric vehicle. Keywords: Air cycle; Heat pump; Turbocharger; Heating

Nomenclature Nomenclature specific heat at constant pressure (J kg-1K-1) h enthalpy (J kg-1) m massive flow rate (kg s-1) p pressure (Pa) R gas constant (J K-1mol-1) wf power consumption of blower (W)

COP qH pr T v wc

Greek symbols effectiveness

Subscripts c compressor

*

coefficient of performance heating capacity (W) pressure ratio temperature (oC/K) specific volume (m3 kg-1) power consumption of compressor (W)

Corresponding author: Tel./fax.: +86-411-84706407; E-mail address: [email protected],

[email protected] 1

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temperature ratio defined in Equation (14) effectiveness of regenerator

f

blower

e L H S o

expander; turbine low-temperature side; cold side high-temperature side; hot side; heating isentropic outside

1. Introduction Global warming and environmental protection are among the major concerns for all governments. Due to the proven detrimental to the ozone layer, hydrochlorofluorocarbon (HCFC) refrigerants are confronted with increasingly strict legislative pressures. HCFC refrigerants have been banned in European Union and will be phased out in China before 2030. Over the last decade, electric vehicles have been attracted increasing attention because of their lower tailpipe emissions. However, a key challenge restricted their widespread application in cold regions is the heating supply. For electric vehicles using conventional vapor compression heat pump systems, the mismatch between the heating capacity of the heat pumps and the heating demand of the vehicles in cold climates is a main issue, which should be carefully considered in system design and operation. As air is an environmentally friendly refrigerant, the reverse Brayton cycle using air as the working fluid is therefore a potential alternative for conventional vapor compression systems. Many studies on the reverse Brayton air cycles are now available in the public domain (Chen et al., 2011; Hou et al., 2008, 2006; Spence et al., 2005; Tu et al., 2006; Yang et al., 2006). Compared to other refrigerants, air refrigerant is uncompetitive (Williamson and Bansal, 2003). However, an air cycle heat pump is a potential substitute for the conventional vapor compression cycle (Angelino and Invernizzi, 1995; Braun et al., 2002). The air cycle heat pump using air as the working medium and the heat carrier was first suggested by Lord Kelvin around 100 years ago, and this system has shown some economic advantages in applications such as hospitals, hotels, and restaurants where there is a high requirement on air change rate (Thomas et al., 1948). As its heating capacity under different operating conditions is in line with the heating load (Zhang and Yuan, 2014), air cycle heat pumps can provide a new solution to the mismatch problem commonly encountered in conventional vapor compression heat pump systems. Compared with conventional vapor compression heat pumps, energy efficiency of a basic air cycle heat pump is less attractive in normal temperature ranges. A regenerated air cycle heat pump was therefore proposed by Fleming et al. (1998) in order to improve the overall system performance. It is expected that the performance of an air cycle heat pump could be improved significantly by adding a regenerator, which can greatly promote its wide deployment (White et al., 2009). There are many theoretical studies on the regenerated air cycle heat pump. On the basis of finite-time thermodynamics, Chen and his coworkers (Bi et al., 2009a, 2009b, 2010, 2012; Chen et al., 1999) investigated the optimal conditions of the regenerated air cycle heat pump with a fixed or variable temperature thermal reservoir based on the key performance indicators such as the heating capacity, COP, and heating capacity density. White (2009) proposed an air cycle heat pump for domestic heating applications and it was found that a better COP could be achieved with 2

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a well-designed regenerator. Zhang et al. (2014) proposed a thermodynamic model for the air cycle heat pump with a compressor and an expander to determine the highest COP that the system can achieve and the corresponding pressure ratio. This thermodynamic model was further developed by Yuan and Zhang (2015) through adding a regenerator into the air cycle heat pump. A simulation model of an air cycle heat pump water heater (ACHPWH) was developed by Yang et al. (2015) and the performance of this model was validated against with the experimental data from the literature. Dieckmann et al. (1979) designed and tested an air cycle heat pump water heater prototype, in which the piston compressor and expander were integrated into one device. It was found that the system performance could reach 1.26 when the cold side temperature was 21ºC. However, how to effectively integrate the expander and the compressor in an air cycle heat pump is still not an easy task and it is therefore important to find a new solution to substitute the existing expander. Over the last decade or so, the turbocharger has been used in air cycle heat pumps. A comprehensive report on an air cycle heat pump research project was released by TNO in 2003, in which a pilot plant for freezing application processes air in open and recuperated cycle, a two stage intercooled compression produces slightly pressurized air which is refrigerated by the recuperator and then expanded in the turbocharger turbine. Spence et al. (2005) established a demonstrator with almost the same layout as that of the TNO pilot plant but capable of fitting the envelope of existing trailer refrigeration units for road transport. Catalano et al. (2010, 2011) designed an air cycle heat pump using a turbocharger for the refrigeration purpose. It was shown that its COP could be higher than 0.6 when the turbine exit temperature is -42.0ºC. In summary, the turbocharger is a potential substitute for the compressor and expander in air cycle heat pump systems which could also be applicable to supply heating for full electric vehicles in cold regions. To date, electric compression refrigeration plus electric heating are mature applications for air conditioning systems in full electric vehicles. However, the consumption of battery is quite high which reduces the automobile mileage (Umezu and Noyama, 2010). The versatility of the heat pump air conditioning system with electrically driven compressor is higher than mechanically driven compressor for different types of electric vehicles, but it is still difficult to solve the efficiency drop, the heating capacity reduction under low temperature conditions and defrosting problems (Takahisa and Katsuya, 1996). This paper presents a new air cycle heat pump system using a turbocharger and a blower, which can solve the existing problem in the air conditioning system of full electric vehicles. A thermodynamic model of this air cycle heat pump is also developed. The performance of this new air cycle heat pump is numerically evaluated and the effects of key influencing factors on the system performance are examined.

2. Description of the air cycle heat pump with a turbocharger The schematic of the proposed air cycle heat pump system is illustrated in Fig. 1, in which a turbocharger and a blower are integrated based on the principles of the regenerated air cycle heat pump. The turbocharger consists of two parts, including a compressor and a turbine to substitute the compressor and the expander of the regenerated air cycle heat pump. A blower is used as the drive equipment to start the system. Since the system employs air as the working fluid, it can be open to the ambient. However, there are two different heating schemes for two different blower locations, e.g. a blower installed before the compressor (Fig. 1(a)) and the blower installed before the turbine as shown in Fig. 1(b). The heating water from the heat exchanger flows through a 3

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blower coil unit. Fig. 2 illustrates the thermodynamic process of the air cycle heat pump with a turbocharger and air as the working medium. The curve 1-2 in Fig. 2 (a) demonstrates the blower compression process while the curves 5-6 and 2-3 show the expansion and compression processes of the turbocharger, respectively. The curve 3-4 represents the heat rejection process and the curves 4-5 and 0-1 show the hot and cold sides of the regenerator, respectively. In Fig. 2 (b), the curve 3-4 shows the blower compression and the curves 5-6 and 1-2 represent the expansion and compression processes of the turbocharger, respectively. The curve 2-3 presents the heat rejection process and the curves 4-5 and 0-1 respectively represent the hot and cold sides of the regenerator.

3. Theoretical analysis 3.1. Thermodynamic modelling In this study, only the air cycle heat pump with a turbocharger and the blower installed before the compressor (named as the air cycle heat pump with the turbocharger hereafter) is investigated as the overall performance of this cycle is better than the other (see Section 4.2). The assumptions used in the model development are presented below.  Isentropic efficiencies of the compressor, expander and blower are constant;  The effectiveness of the regenerator is given;  The air is an ideal gas;  Both the heat absorption and rejection processes are considered as isobaric;  Ambient temperature and outlet temperature of the heat exchanger are given; and  The pressure lines are approximately in parallel in T-s diagram within the certain ranges of the entropy difference. Based on the above assumptions, the heating capacity of the air cycle heat pump with a turbocharger can be determined by Eq. (1). The blower power consumption can be calculated using Eq. (2). The heating COPH of the air cycle heat pump with a turbocharger can therefore be easily determined by Eq. (3). The ideal gas law is described by Eq. (4). (1) (2) (3) (4) The isentropic compression process is described as Eq. (5), in which the subscript 3s-1 represents the corresponding isentropic compression process of point 1 to point 3. (5) The isentropic expansion process can be expressed as below, in which the subscripts 5 to 6s indicate the isentropic throttling process of point 5 to point 6 as illustrated in Fig 2(a). (6) The balance equation of the turbocharger was derived as Eqs. (7)-(9) (Liu et al., 2011). Here, the subscript 3s-2 means the corresponding isentropic compression process from point 2 to point 3 as shown in Fig 2(a). (7) (8) 4

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(9) Based on the assumptions presented above, below equations can be easily derived, in which the subscript 2s-1 represents the corresponding isentropic compression process from point 1 to point 2 as shown in Fig 2(a). (10) (11) The regenerating heat transfer process is described below. (12) In addition, two dimensionless variables γ and are defined below and the values of both are larger than 1. γ is similar to the pressure ratio but is simpler for the cycle analysis in this case. Hereafter, γ will be named as the pressure ratio. is defined as the ratio of the lowest temperature at the hot side to the highest temperature at the cold side of the cycle. Accordingly, the unspecified temperatures and can be expressed by γ and as in Eqs. (15) and (16), respectively. (13) (14) (15) (16) The temperatures of and can be calculated as in Eqs. (17) and (18) respectively, according to the above equations. Therefore, Eq. (3) can be further re-written as in Eq. (19). (17) =

(18) =

=

(19)

where ; . 3.2. Cycle performance variation with the pressure ratio Similar to the regenerated air cycle heat pump, there is an optimal heating COP in the air cycle heat pump with a turbocharger, which is determined by the pressure ratio γ. To analyze how the heating COP changes with the variation of γ, the partial derivatives are taken with the respect to the pressure ratio. The optimal pressure ratio should satisfy is re-arranged as

and the numerator polynomial of . (20)

where, A= B=

(21) (22)

C=

(23) 5

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The discriminant of the quadratic polynomial of Eq. (20) is expressed as below. (24) Therefore, it has two different real roots, namely, (25) Since

is larger than 1, thus, (26)

At the optimal pressure ratio, the heating COP reaches its maximum value and the optimal heating COP of the air cycle heat pump can be determined as follows. =

=

(27)

4. Results and Discussions 4.1. Model validation Currently, there are no experimental data to verify the derived expression (27), so the EES (Engineering Equation Solver) software was chosen to build the thermodynamic models of main parts of the air cycle heat pump with a turbocharger, and the corresponding results by iteration were used to validate the expression (27). Before attempting to validate the expression (27), the literature data of the regenerated air cycle heat pump with an expander from Yuan et al. (2015) are first used to verify whether the EES could be directly applied to calculation of the performance of an air cycle heat pump. The cycle process presented in Yuan et al. (2015) was reprogrammed using the EES. The computation flowchart of the regenerated air cycle heat pump with an expander implemented in the EES is shown in Fig. 3. A comparison between the literature data from Yuan et al. (2015) and the simulation data from the EES software is shown in Fig. 4. It can be seen that the system performance predicted by the EES software matched well with the literature data with the relatively deviations within 1.0% , which showed the EES software can be used to calculate well the performance of the air cycle heat pump. It is worthwhile to note that during this comparison, the isentropic efficiencies of the compressor and the expander were assumed as 85% and 90%, respectively. In general, the compressor efficiency and the turbine efficiency can easily reach above 80% and 70% respectively, when a large turbocharger is used (Honeywell, 2005). The regenerated air cycle heat pump was simulated again with the compressor efficiency of 80% and the expander efficiency of 70% while the efficiency of the regenerator varied from 80% to 90%. The results are presented in Fig. 5. A dramatic drop of the heating COP can be observed under the low efficiencies of the expander and the compressor. In other words, the efficiency of a turbocharger has a significant influence on the COP of the air cycle heat pump.

6

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Fig. 6 shows the flowchart to calculate the optimal heating COP of the air cycle heat pump with the turbocharger in EES and Fig. 7 presents a comparison between the simulated data using the EES and the calculated data using Eq. (27). It can be found that the system COP predicted by the thermodynamic model of the air cycle heat pump with the turbocharger matched well with the simulated data using EES with the largest error of less than 1.3%. 4.2. Performance investigation In this section, the performance of the air cycle heat pump with the turbocharger is analyzed. In order to facilitate the performance comparison, the compressor efficiency was fixed as 80% while the turbine efficiency and blower efficiency were fixed as 70% and 50%, respectively. The water temperature at the heat exchanger outlet was maintained at 5.0ºC lower than the air, and the outlet air temperature of the heat exchange is fixed. Fig. 8 shows how the optimal COP changes at two different blower locations. The efficiencies used in the two cycles were the same. It can be seen that there is no much difference between the two curves. For the cycle with the blower installed before the compressor, the optimal heating COP at different working temperatures was relatively higher than that of the other because of the power of the blower directly provide into the compressor instead of inputting into the turbine, thus reducing the energy loss of the turbine. Therefore, the performance of the regenerated air cycle heat pump with the turbocharger and blower installed before the compressor is better than that before the expander. Fig. 9 illustrates how the optimal heating COP of the system with the blower installed before the compressor changes with the variation of the efficiencies of the expander and compressor under different ambient air conditions. In general, the system heating COP increased with the increase of the ambient temperature. Under the same ambient temperature condition, the system heating COP decreased with the decrease of the efficiencies of the expander and compressor. For the cycle with the blower installed before the compressor, the efficiency of the compressor/turbine was changed when turbine/compressor was fixed. The heating COP increased from 1.33 to 1.47 when the expander (turbine) efficiency increased from 0.65 to 0.75 under the ambient temperature of 20oC. However, the increase of the heating COP was relatively small when increasing the compressor efficiency (see Fig. 9 (b)). In general, the heating COP of an air cycle heat pump with a turbocharger seems more sensitive to the expander (turbine) efficiency than the compressor efficiency of the turbocharger. The heat capacities of the regenerated air cycle heat pump with the expander, the air cycle heat pump with the turbocharger and the blower installed before the compressor (named as Cycle 1) and the air cycle heat pump with the turbocharger and the blower installed before the turbine (named as Cycle 2) are also simulated and the results are presented in Fig. 10. It is worthwhile to note that the values presented in Fig. 10 were normalized based on the results obtained at -20ºC. It can be seen that the trends of the heating capacities of the three systems are similar when the ambient air temperature varied from -20ºC to 15ºC. In comparison, the volumetric heating capacity of Cycle 1 has an obvious advantage over the other two cycles and the heating load of the three systems almost linearly increased with the decrease of the ambient air temperature. The trend of the heating capacity curve plotted in Fig. 10 is an agreement with the expression (53) in the literature Zhang and Yuan (2014), which indicates that the heating capacity increases when the heat source temperature goes down. This is very different from conventional vapor-compression cycles but in line with the change of the heating load with the ambient air temperature. 7

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4.3. Application Full electric vehicle uses energy from the energy storage systems to provide tractive and auxiliary power to the vehicle. Due to its limited specific energy, the energy requirement of heating, ventilation, and air conditioning (HVAC) systems for the vehicle cabin can significantly reduce the charge cycles (Kambly et al., 2014). At present, the power consumption of the HVAC system accounts for about 60-75% of the total power consumption of electric vehicles (Chen et al., 2002). In this study, the new air cycle system with the turbocharger can be applied as air conditioning system in full electric vehicles, and the cycle can meet different requirements of heating in winter and cooling in summer. The air conditioning systems used in most of full electric vehicles adopt the compressor for cooling in summer while using the positive temperature coefficient (PTC) thermistor for heating in winter which has a lower efficiency. According to the design conditions of the full electric vehicles in Laurikko et al. (2013), duty cycles used included the European type approval cycle (NEDC) and a realistic cycles in Helsinki City, and a commonly known real-world cycle in Artemis Urban. The test on a Citroën C-Zero electric vehicle was carried out under the ambient of -20ºC and their power consumptions for heating with PTC are presented in Table 1. Because of low efficiency of heating with PTC, an air source heat pump (ASHP) could be employed to meet both the heating and cooling demand with a sole system. Qin et al. (2015) tested the heating performance of a vapor compression heat pump for electric vehicles on a test bench. The power consumption of their test bench of ASHP with COP of about 1.5 (see Fig.4 in Qin et al. (2015)) is shown in Table 1 under the ambient temperature of -20ºC, and the heating capacity was approximately taken from the power consumption of PTC heater in Table 1. For the new air cycle system with the turbocharger, the heating performance was calculated based on the EES and the calculation flow chart in Fig.6 under the same conditions, and the corresponding COP could reach 1.3 with the supply air temperature of 35ºC (i.e., the comfort temperature given by Dauvergne (1994)). The power consumption of the new air cycle system is also shown in Table 1. It can be found that the energy saving ratio is about 23% using the air cycle heat pump with the turbocharger, as compared to that of using PTC. Comparing with the ASHP, although the power consumption of the new air cycle heat pump is a little higher, it could be applied under a lower ambient temperature. Furthermore, this new air cycle could offer more heating capacity to meet the higher heating load under lower outdoor temperature conditions, which is better than the ASHP. Although the COP of the air cycle heat pump with the turbocharger is lower, its working temperature range is wider in cold climates. It is believed that the energy saving potential will enhance with the continuous increase of the turbocharger efficiency.

5. Conclusions In this paper, a new air cycle heat pump with a turbocharger and a blower was proposed and a thermodynamic model for this cycle was developed. The impact of the turbocharger on the performance of the air cycle heat pump was analyzed. A comparison of the performance between the regenerated air cycle heat pump with/without a turbocharger and a blower were also numerically investigated. The two air cycle processes, both using the turbocharger, with different locations of a blower were designed. It was found that the impact of the compressor efficiency of the turbocharger on the system COP was smaller than its turbine efficiency. The heating COP of the new air cycle heat pump 8

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using the turbocharger and the blower installed before the compressor is better than that with the blower installed before the turbine. The volumetric heating capacity of the former is also higher than the latter and the regenerated air cycle heat pump without using a turbocharger. The results also showed that the air cycle with the turbocharger saved about 23% power than the PTC system under the same conditions for full electric vehicles and its working temperature range is wider in cold climates than the traditional vapor compression heat pump, which demonstrated that this cycle has a great potential for heating of full electric vehicles in cold climates. Acknowledgments This research was supported by the Research Fund for the Doctoral Program of Higher Education of China (No. 20120041110006). References Angelino, G., Invernizzi, C., 1995. Prospects for real-gas reversed Brayton cycle heat pumps. Int. J. Refrigeration 18, 272-280. Bi, Y.H., Chen, L.-G., Sun, F.R., 2009a. Exergy-based ecological optimization for an endoreversible variable-temperature heat reservoir air heat pump cycle. Rev. Mex. Fis. 55, 112-119. Bi, Y.-H., Chen, L.-G., Sun, F.-R., 2009b. Heating load, heating load density and COP optimisations for an endoreversible variable temperature heat reservoir air heat pump. J. Energy Inst. 82, 43-47. Bi, Y.H., Chen, L.G., Sun, F.R., 2010. Exergetic efficiency optimization for an irreversible heat pump working on reversed Brayton cycle. Pramana 74, 351-363. Bi, Y.H., Chen, L.G., Sun, F.R., 2012. Heating load density optimization of an irreversible simple Brayton cycle heat pump coupled to counter-flow heat exchangers. Appl. Math. Model. 36, 1854-1863. Braun, J., Bansal, P., Groll, E., 2002. Energy efficiency analysis of air cycle heat pump dryers. Int. J. Refrigeration 25, 954-965. Catalano,L. A., Bellis, F. D., Amirante, R.,2010. Improved inverse Joule Brayton air cycle using turbocharger units. Conference on Thermal and Environmental Issues in Energy Systems: 16-19. Catalano, L. A., Bellis, F. D., Amirante, R.,2011. Development and testing of sustainable refrigeration plants. Proceedings of ASME Turbo Expo: 1-8. Chen, L.-G., Ni, N., Sun, F., Wu, C., 1999. Performance of real regenerated air heat pumps. Int. J. Power Energy Syst. 19,231-238. Chen, L.G., Tu, Y.M., Sun, F.R., 2011. Exergetic efficiency optimization for real regenerated air refrigerators. Appl. Therm. Eng. 31, 3161-3167. Chen, Q.Q., Sun, F.C., Zhu, J.G., 2002. Modern electric vehicle technology. Beijing: Beijing Institute Technology Press: 5-6. Dauvergne, J.L., 1994. Thermal Comfort of Electric Vehicles. Advancements in Electric & Hybrid Electric Vehicle Technology, 13-17. Dieckmann, J., Erickson, A., Harvey, A., Toscano, W., 1979. Research and Development of an Air-cycle Heat-pump Water Heater. Foster-Miller Associates, Inc, Waltham, MA, pp. 1-341. Fleming, J., Li, L., Vander W. B., 1998. Air cycle cooling and heating, part 2: a mathematical model for the transient behaviour of fixed matrix regenerators. Int J Energy Res: 22. 9

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Honeywell, 2005. Turbocharger guide volume 5: 66-78. Hou, S.B., Li, H.C., Zhang, H.F., 2008. An open air-vapor compression refrigeration system for air-conditioning and desalination on ship. Desalination 222, 646-655. Hou, Y., Zhao, H.L., Chen, C.Z., Xiong, L.Y., 2006. Developments in reverse Brayton cycle cryocooler in China. Cryogenics 46, 403-407. Kambly, K., Thomas, H., 2014. Estimating the HVAC energy consumption of plug-in electric vehicles. Int. J. Power Sources 259: 117-124. Laurikko, J., Granström, R., Haakana A., 2013. Realistic estimates of EV range based on extensive laboratory and field tests in Nordic climate conditions. World Electric Vehicle Journal 6, 129-203. Liu, J.P., Fu, J.Q., Feng, K., Zhao, Z.C., Wang, S.Q., 2011. A study on the energy flow of diesel engine turbocharged system. J. Hunan University (Natural Sciences) 38, 48-53. (in Chinese) Qin, F., Xue, Q.F., Velez, G., Zhang, G.Z., 2015. Experimental investigation on heating performance of heat pump for electric vehicles at -20ºC ambient temperature. Energy Conversion and Management 102, 39-49. Spence, S.W.T., Doran, W.J., Artt, D.W., McCullough, G., 2005. Performance analysis of a feasible air-cycle refrigeration system for road transport. Int. J. Refrigeration 28, 381-388. Thomas, T.F., 1948. The Air Cycle Heat Pump. Proceedings of the Institution of Mechanical Engineers 158.1, 30-51. TNO, Cooling, Freezing and Heating with the Air Cycle, Documentation Sheet, TNO Environment, Energy and Process Innovation, Department of Refrigeration and Heat Pump Technology, 2003, Available at: www.mep.tno.nl/Informatiebladen_eng/002e.pdf/. Umezu, K., Noyama, H., 2010. Air -Conditioning system For Electric Vehicles (i - MiEV). SAE Automotive Refrigerant& System Efficiency Symposium. Takahisa, S., Katsuya, I., 1996. Air Conditioning System for Electric Vehicle. SAE. Tu, Y., Chen, L., Sun, F., Wu, C., 2006. Cooling load and coefficient of performance optimizations for real air-refrigerators. Appl. Energy 83, 1289-1306. White, A.J., 2009. Thermodynamic analysis of the reverse Joule- Brayton cycle heat pump for domestic heating. Appl. Energy 86, 2443-2450. Williamson, N., Bansal, P., 2003. Feasibility of air cycle systems for low-temperature refrigeration applications with heat recovery. Proc. Inst. Mech. Eng. Part E J. Process Mech. Eng.217, 267-273. Yang, Y., Lin, B., Chen, J., 2006. Influence of regeneration on the performance of a Brayton refrigeration-cycle working with an ideal Bose-gas. Appl. Energy 83, 99-112. Yuan, H., Zhang, C.L., 2015. Regenerated air cycle potentials in heat pump Applications. Int. J. Refrigeration 51, 1-11. Yang, Y., Yuan H., Peng, J.W., Zhang, C.-L., 2015.Performance modeling of air cycle heat pump water heater in cold Climate. Renewable Energy 87, 1067-1075. Zhang, C.L., Yuan, H., 2014. An important feature of air heat pump cycle: heating capacity in line with heating load. Energy 72, 405-413.

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(a)

(b)

1-compressor; 2-heat exchanger; 3-blower; 4-regenerator; 5-turbine; 6-blower coil; 7-oil pump; 8-oil tank

Fig. 1. Schematic of an air cycle heat pump with a turbocharger.

(a) (b) Fig. 2. T-s diagram of the air cycle heat pump with a turbocharger.

Fig. 3. Flow chart of the calculation model using EES.

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Fig. 4. Validation of the calculation model using EES.

Fig. 5. Performance of the regenerated air cycle heat pump under different efficiencies.

Fig. 6. Flow chart of the calculation model using EES.

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Fig. 7. Validation of the thermodynamic model.

Fig. 8. Comparison of the heating COP of the two air cycle heat pumps with turbocharger.

(a) (b) Fig. 9. Comparison of heating COP at different turbocharger efficiencies.

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Fig. 10. Comparison of heating capacity at different environment temperatures.

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Table 1. Power consumption of full electric vehicles Cycle PTC Heater ASHP type energy per km energy kWh kWh NEDC Helsinki City Aremis Urban

0.134 0.236 0.256

0.089 0.157 0.171

Air cycle heat pump energy kWh 0.102 0.180 0.196

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