Abstract
Frost layer on the outdoor air heat exchanger surface in an air-source heat pump (ASHP) can decrease the system coefficient of performance (COP). Although the common defrosting and anti-frosting methods can improve the COP, the periodic defrosting not only reduces the system energy efficiency but also deteriorates the indoor environment. To solve these problems, it is necessary to clearly understand the frosting phenomenon and to achieve the system frost-free operation. This paper focused firstly on the analyses of frosting pathways and frosting maps. Followed by summarizing the characteristics of frost-free technologies. And then the performances of two types of frost-free ASHP (FFASHP) systems were reviewed, and the exergy and economic analysis of a FFASHP heating system were carried out. Finally, the existing problems related to the FFASHP technologies were proposed. Results show that the existing frosting maps need to be further improved. The FFASHP systems can not only achieve continuous frost-free operation but reduce operating cost. And the total COP of the FFASHP heating system is approximately 30–64% higher than that of the conventional ASHP system under the same frosting conditions. However, the investment cost of the FFASHP system increases, and its reliability also needs further field test in a wider frosting environment. In the future, combined with a new frosting map, the control strategy for the FFASHP system should be optimized.
Highlights
With increasing promotion of energy-saving and emission-reduction policies in China, space heating and hot water supply modes are gradually being transformed from the ways for traditional small coal-fired boiler and scattered coal burning to a clean heat supply system, and that is so-calledCoal to Clean Energy or Coal to Electricity
Thevalve, structural parameters dehumidification technology mainly of a exchanger compressor, a four-way a water tank, an of ESD, and the main characteristics of the measuring instrumentation are listed in energy storage device (ESD), three electronic expansion valves (EEVs), an extra heat exchanger water heater system, the operation conditions in coated by a solid desiccant (EHECSD) and an outdoor air heat exchanger [10,80,85]
To improve the coefficient of performance (COP) of the frost-free ASHP (FFASHP) system, the dehumidification capacity of desiccant, the crystallization and the viscosity with temperature should be taken in account in selecting solution desiccant, the crystallization and the viscosity with temperature should be taken in account the concentration of solution desiccant
Summary
With increasing promotion of energy-saving and emission-reduction policies in China, space heating and hot water supply modes are gradually being transformed from the ways for traditional small coal-fired boiler and scattered coal burning to a clean heat supply system, and that is so-called. Coal to Clean Energy or Coal to Electricity. The popularization of the ASHP system will contribute to the development of the clean heating industry in China. The commercial space heating accounts for 12.5% of the heating market
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