1 Copyright © 20xx by ASME Proceedings of the ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems and ASME 2015 12th International Conference on Nanochannels, Microchannels, and Minichannels InterPACKICNMM2015 July 6-9, 2015, San Francisco, California, USA InterPACKICNMM2015-48048 NUMERICAL-BASED COMPARISON AMONG CRITICAL FLOW PROPERTIES OF HFC-134A AND ITS NEW ALTERNATIVES HFO-1234YF AND HFO-1234ZE THROUGH SHORT-TUBE ORIFICES Puya Javidmand Wichita State University Wichita, Kansas, USA Klaus A. Hoffmann Wichita State University Wichita, Kansas, USA ABSTRACT Although HFC-134a is a common refrigerant for residential and mobile refrigeration systems, investigators are dealing with replacing it with new alternatives because of its harmful environmental and global warming effects. Recently HFO- 1234yf and HFO-1234ze have been introduced as suitable alternative refrigerants because they have zero ozone depletion potential (ODP) and low global warming potential (GWP) and possess thermophysical properties similar to those of HFC-134a. Because there is no experimental data on the performance of these new refrigerants in capillary tubes and short-tube orifices, a recently developed numerical model for analysis of critical two-phase flow through these tubes is used to predict the critical mass flow rate and pressure distribution of HFO-1234yf and HFO-1234ze under various operating conditions. The applied numerical model is based on a comprehensive two-fluid model including the effects of two-phase flow patterns and liquid-phase metastability. The numerical method has been validated by comparing numerical results of the critical flows of HFC-134a, R-410A, and HCFC-22 with available experimental data. The developed numerical simulation is applied in order to develop comparison and selection charts for short-tube orifices based on the common refrigerant HFC-134a and the alternative new refrigerants HFO-1234yf and HFO-1234ze. INTRODUCTION Due to their safety properties, CFCs (chlorofluorocarbon) and HCFCs (hydro chlorofluorocarbon) have been used as the most common chemical refrigerants from 1930 until the early 1990s. These refrigerants are non-flammable, non-toxic, and stable. However, through the Montreal protocols in 1987 and 1992, they were phased out as a result of their harmful impact on the ozone layer because they contain chlorine atoms and consequently a high ozone depletion potential ODP number [1]. Subsequently, these refrigerants were replaced by HFC refrigerants with an ODP number of 0, such as HFC-134a. Currently, the most serious environmental problem is global warming. This effect is defined in refrigerants as the global warming potential GWP number. This number for HFC-134a, the current refrigerant for mobile air conditioning systems, is 1430 and for R-410A is 1730 [2]. In 2006, the European Union (EU) banned the use of refrigerants with GWP numbers higher than 150 and this rule has been enforced beginning in January 2011. Accordingly, it is expected that these refrigerants will be completely phased out by 2017 [3]. Previously, carbon dioxide, with a GWP number of 1, was the leading candidate to replace HFC-134a in the automotive industry. However, it contributes to major problems. Because of its high vapor pressure at the typical operating temperature of air conditioning systems, the replacement of current refrigerants with carbon dioxide not only