Development Closed-loop Oscillating Heat Pipe with Check Valves (CLOHP/CV) to Enhance Heat Removal from Automobile Air-conditioner

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The paper presented the application of the Closed-loop oscillating heat pipe with check valves (CLOHP/CV) to enhance heat extraction from the condenser of the automobile air-conditioner (AAC). The CLOHP/CV used R-134a as working fluid, filling 50% by volume. There were 3 designs having 4, 6 and 8 loops, and tested by varying tilted angle; 0º, 30º, 45º and 60º. The surface temperature of evaporator and condenser sections increased with the tilted angle and number of CLOHP/CV loops. The 8 loops CLOHP/CV tilted by 60 degrees provided maximum heat transfer rate 3,789 W, convection heat transfer coefficient 4,028 W/m2·ºC, and minimum thermal resistance 0.63 ºC/kW. The CLOHP/CV was tested with a demonstration unit of automobile air-conditioner at TNI. The COP and EER of the AAC using CLOHP/CV for enhancing heat removal from the condensing coil were 6.50 and 22.16 Btu/h/W, respectively. The maximum effectiveness of CLOHP/CV was nearly 0.5 when implementing to enhance heat releasing at AAC. Therefore, the 8-loops tilted by 60-degree CLOPH/CV was effectively enhancing performance of the automobile air-conditioner.