Evaluating alternative refrigerants for the room air conditioner market

• Main Authors: Back, Izabelle, Dunberger, Lars
• Format: Others
• Language: English
• Published: KTH, Tillämpad termodynamik och kylteknik 2015
• Subjects: Refrigerant; air conditioner; market; trends; alternative refrigerant; test rig; GWP; R32; R290; Energy Engineering; Energiteknik
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173880

This study aimed to facilitate evaluation of alternative refrigerants for the air conditioner market. In order to achieve this target, two objectives were set. The first being the identification of alternative refrigerant with regard to regulations and trends. The second being enabling of thermodynamic evaluation of refrigerants for single components in air conditioners via design and installation of a test rig. A literature review was conducted to investigate the regulations, standards and trends for nine regions with high market shares. Furthermore, refrigerant substitutes for R410A and R22 where identified. The literature showed strong indications that a global HFC phase down is on the horizon, but that the approach and urge for such a phase down varies between regions where three main priorities could be seen; efficiency, GWP values and safety. Comparing these priorities with simulated refrigerant characteristics such as Carnot efficiency, GWP values, volumetric capacity and the liquid density using RefProp, identified alternatives. Further the literature showed that the lower flammability limit (LFL) and the amount of charge allowed were limiting factors for flammable refrigerant. There are many new refrigerants that could have less charge for the same capacity the LFL however restricts the refrigerants like R290, R441A and R443A only to be used in small systems. A test rig was designed and constructed in order to enable testing of single components in air conditioners. To verify the test rig, tests conducted with an evaporator using two refrigerants: R410A and R32. The reliability and validity of the tests was studied by comparing the results from the air side and refrigerant side, via uncertainty calculations using the GUM method and by a thermodynamic evaluation. The results of the repetition tests showed an expanded uncertainty, with a confidence interval of 95%, of 26 W for a cooling capacity of 2190W for R410A (Q̇evap,R410A=2190±26W). For R32 the expanded uncertainty was 27W for a cooling capacity of 2795W (Q̇evap,R32=2795±27W). Also the test rig was verified to be used for analyzing detailed evaluation of evaporators such as looking at heat transfer and the differential pressure drop. Further the study presented six conclusions: When evaluating refrigerants regional priorities between efficiency, safety and GWP values, refrigerant characteristics and type of unit need to be considered. Safety standards need to be more acceptable towards flammable refrigerants in order to meet low GWP targets. The change in market trends leads to new roles for the refrigerant and compressor suppliers and put higher demand on air conditioner manufacturers to consider refrigerant characteristics in product development. The importance of experimental thermodynamic evaluation on refrigerants effect on single components is increasing. Performance of different refrigerant for single components can be evaluated for optimizing cycle performance. Leapfrogging in the developing world can lead to a faster introduction of low GWP refrigerants.