Refrigerant flow characteristics of electronic expansion valve based on thermodynamic analysis and experiment

Abstract A mass flow correlation for R134a through an EEV (electronic expansion valve) is developed from extensive experimental data. The refrigerant mass flow characteristics of the EEV are an important issue in heat pump/refrigeration system operation because the valve regulates the refrigerant flow to match various operating conditions. Based on the throttling mechanism and thermodynamic analysis, the mass flow rate is a function of various parameters. The selected decision parameters include the valve’s geometric parameters, the inlet refrigerant pressure and temperature, the outlet refrigerant pressure, and the refrigerant thermophysical properties represented by the dynamic viscosity and the surface tension, which are sufficient and irredundant for determining the flow coefficient. Because these parameters have very complex and coupled effects on the mass flow characteristics, two combined non-dimensional parameters are defined to describe the coupled effects based on the influence and uncertainty analysis of parameters. The experimental results illustrate that the defined non-dimensional parameters can reveal the EEV flow characteristics correctly. Then, the semi-theoretical flow coefficient correlation with respect to the defined non-dimensional parameters is proposed and identified from several hundred sets of experimental samples using multivariable regression analysis. The proposed correlation agrees well with experimental data for R134a within a wide range of operating conditions. The investigation method in this paper can be adopted by the flow characteristics studies for other types of the EEVs and refrigerants.

[1]  S. Klein,et al.  NIST Standard Reference Database 23: NIST Thermodynamic and Transport Properties of Refrigerants and Refrigerant Mixtures-REFPROP, Version 6.0 | NIST , 1998 .

[2]  H. Harry Asada,et al.  Modeling of Vapor Compression Cycles for Multivariable Feedback Control of HVAC Systems , 1997 .

[3]  Yong Chan Kim,et al.  The effects of improper refrigerant charge on the performance of a heat pump with an electronic expansion valve and capillary tube , 2002 .

[4]  D. O’Neal,et al.  A comparison of critical flow models for estimating two-phase flow of HCFC22 and HFC134a through short tube orifices , 1995 .

[5]  Zhijiu Chen,et al.  A new method for controlling refrigerant flow in automobile air conditioning , 2004 .

[6]  Chen Wu,et al.  Development of control method and dynamic model for multi-evaporator air conditioners (MEAC) , 2005 .

[7]  P. Hrnjak,et al.  Flow of Refrigerant 134a Through Orifice Tubes , 2001 .

[8]  D. Oneal,et al.  Two-phase flow of HFC-134a and CFC-12 through short-tube orifices , 1994 .

[9]  Chen Jiangping,et al.  Experimental research on refrigerant mass flow coefficient of electronic expansion valve , 2005 .

[10]  Jong Min Choi,et al.  A generalized correlation for two-phase flow of alternative refrigerants through short tube orifices. , 2004 .

[11]  Dennis L. O'Neal,et al.  Two-phase flow of R-22 through short-tube orifices , 1994 .

[12]  Rita Mastrullo,et al.  Experimental evaluation of electronic and thermostatic expansion valves performances using R22 and R407C , 2002 .