Abstract
Due to the concern on global warming, the demand for a system using natural refrigerant is increasing and many researches have been devoted to develop systems with natural refrigerants. Among natural refrigerant systems, an air cycle system has emerged as one of alternatives of Freon gas system due to environmentally friendly feature in spite of the inherent low efficiency. To overcome the technical barrier, this study proposed combination of multiple systems as a hybrid cycle to achieve higher efficiency of an air cycle system. The hybrid air cycle adopts a humidity control units such as an adsorber and a desorber to obtain the cooling effect from latent heat as well as sensible heat. To investigate the efficacy of the hybrid air cycle, the cooling performance of a hybrid air cycle is investigated analytically and experimentally. From the simulation result, it is found that COP of the hybrid air cycle is two times higher than that of the conventional air cycle. The experiments are conducted on the performance of the desiccant system according to the rotation speed in the system and displayed the feasibility of the key element in the hybrid air cycle system. From the results, it is shown that the system efficiency can be enhanced by utilization of the exhausted heat through the ambient heat exchanger with advantage of controlling the humidity by the desiccant rotor.
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Abbreviations
- c p :
-
Specific heat, kJ/kg K
- G :
-
Mass flow rate, kg/s
- G air :
-
Mass flow rate of dry air, kg dry air/s
- G w :
-
Mass flow rate of water vapor, kg/s
- h :
-
Specific enthalpy of the dry air, kJ/kg dry air
- Q :
-
Heat transfer rate, kW
- Q room :
-
Cooling capacity in room, kW
- T :
-
Temperature, °C
- W :
-
Power, kW
- x :
-
Humidity ratio, kg/kg dry air
- ε:
-
Temperature effectiveness
- η :
-
Adiabatic efficiency
- a, b, c :
-
State points of ambient air defined in Fig. 2
- act :
-
Actual
- air :
-
Air
- amb :
-
Ambient air, ambient heat exchanger
- cool :
-
Cooling water
- 1~8:
-
State points of working air defined in Fig. 2
- i, ii:
-
State points of cooling water defined in Fig. 2
- com :
-
Compressor
- DA :
-
Dry air
- exp :
-
Expander
- id :
-
Ideal
- rej :
-
Rejection heat
- room :
-
Room
- spl :
-
Supply water
- sub :
-
Sub heat exchanger
- w :
-
Water
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Acknowledgments
This work was supported by a grant from the Research Project for Environmentally Friendly Air-Conditioning and Refrigeration System of Mayekawa MFG Co., Ltd., Japan.
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Hwang, K., Song, C.H., Kim, S.K. et al. Thermodynamic performance of a hybrid air cycle refrigeration system using a desiccant rotor. Heat Mass Transfer 49, 359–367 (2013). https://doi.org/10.1007/s00231-012-1079-6
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DOI: https://doi.org/10.1007/s00231-012-1079-6