Research on frost formation in air source heat pump at cold-moist conditions in central-south China

A dynamic evaporator model of air source heat pump (ASHP), considering the ratio of the latent heat to sensible heat of wet air, is presented to analyze the performance of ASHP under frosting. The performance parameters, such as the heating capacity, COP and the outlet temperature of compressor, are simulated with CYCLEPAD. Then a semi-empirical correlation that predicts frost accumulation on the air-side of fin-tube heat exchanger is developed with dimensionless analysis and also modified by a test conducted under cold-moist conditions in winter. In addition, eight influence factors are considered involving the ambient conditions and structures of heat exchanger, whose effects are analyzed as well. Among them, the equivalent diameter of air flow cross-section in fin-tube deq is especially proposed. Lastly, the relationships between the ratio, the performance parameters and the frost accumulation are discussed in this paper, followed by an evaluation of an optimal defrosting time interval to improve the ASHP’s energy efficiency and operational reliability at cold-moist conditions in central-south China.

[1]  Shiming Deng,et al.  A study on the performance of the airside heat exchanger under frosting in an air source heat pump water heater/chiller unit , 2004 .

[2]  Yi Jiang,et al.  Experiment investigation of reverse cycle defrosting methods on air source heat pump with TXV as the throttle regulator , 2004 .

[3]  L. A. Wenzel,et al.  Measurement and Correlation of Water Frost Thermal Conductivity and Density , 1970 .

[4]  Ju-Suk Byun,et al.  The application of photo-coupler for frost detecting in an air-source heat pump , 2006 .

[5]  S. M. Sami,et al.  Mass and heat transfer during frost growth , 1989 .

[6]  Nilufer Egrican,et al.  Frost formation on fin-and-tube heat exchangers. Part I—Modeling of frost formation on fin-and-tube heat exchangers , 2004 .

[7]  Hakan Karatas,et al.  Frost formation on fin- and- tube heat exchangers. Part II—Experimental investigation of frost formation on fin- and- tube heat exchangers , 2004 .

[8]  Minglu Qu,et al.  An experimental investigation on reverse-cycle defrosting performance for an air source heat pump using an electronic expansion valve , 2012 .

[9]  Empirical heat transfer and frost thickness correlations during frost deposition on a cylinder in cross-flow in the transient regime , 1998 .

[10]  D. R. Tree,et al.  A review of frost formation in simple geometries , 1985 .

[11]  Ni Long,et al.  An experimental study on the operating performance of a novel reverse-cycle hot gas defrosting method for air source heat pumps , 2011 .

[12]  Shiming Deng,et al.  Improved indoor thermal comfort during defrost with a novel reverse-cycle defrosting method for air source heat pumps , 2010 .

[13]  Correlations of Frost Properties Considering the Environmental Parameters over a Cold Flat Plate , 2001 .

[14]  C. J. Cremers,et al.  Frost Formation on Vertical Cylinders in Free Convection , 1982 .

[15]  Wen-Ruey Chang,et al.  Performance of finned tube heat exchangers operating under frosting conditions , 2003 .

[16]  R. W. Besant,et al.  Frost characteristics and heat transfer on a flat plate under freezer operating conditions: Part I, Experimentation and correlations , 1999 .

[17]  Dennis L. O'Neal,et al.  Performance of finned-tube heat exchangers under frosting conditions: I. Simulation model , 1993 .

[18]  K. Kishinami,et al.  Study on Properties and Growth Rate of Frost Layers on Cold Surfaces , 1983 .

[19]  Kenneth D. Forbus.  CyclePad: An Articulate Virtual Laboratory for Engineering Thermodynamics , 1999, Artif. Intell..

[20]  H. W. Schneider,et al.  Equation of the growth rate of frost forming on cooled surfaces , 1978 .

[21]  J. D. Parker,et al.  Frost Formation With Varying Environmental Parameters , 1975 .