Experimental and Computational Study on Helical Coil and Straight Type Sub-Cooled Condenser for Air Conditioner in Automobile Vehicle 2020-01-1246

This paper provides the importance of helical coil sub-cooled condenser which has a compact structure, large heat transfer area, and high heat transfer capability in comparison to the straight sub-cooled condenser in the automobile vehicle. The HVAC unit has the largest parasitic load on the engine. Hence, by improving the coefficient of performance of the air-conditioning (A/C) system, the reduction in vehicule emissions is possible. Previous studies explain that there is generation of secondary flow inside the fluid in the circular cross-section of the helical coil. By using the effect of the secondary flow generation, authors tried to enhance the heat transfer rate as it leads to heterogeneous temperature distribution across the periphery of the tube and causes a higher heat transfer. For the purpose of the study, a prototype with a square cross-sectional 2.7 mm × 2.7 mm channel with flat fins towards the outer side has been constructed. Heat transfer characteristics for the square channel helical coil cub-cooled condenser (HCSCC) has been evaluated experimentally and then compared with CFD analysis. During the bench test, a calorimeter was used to obtain the desired ambient temperature along with the humidity level inside a control volume. It has been found that the helical coil sub-cooled condenser provides enhanced heat transfer as well as higher turbulent kinetic energy characteristics on the refrigerant side. Additionally, the results from the CFD analysis revealed that the heat transfer coefficient for the helical coil sub-cooled condenser on the refrigerant side was 1.35 times greater than the conventional type of sub-cooled condenser. This is because the turbulent kinetic energy, which is the essential factor for enhancing the heat transfer coefficient, shows a higher value for helical condenser as compared to a straight sub-cooled condenser.