Air side performance of tube bank of an evaporator in a window air-conditioner by CFD simulation with different circular tubes with uniform transverse pitch variation

Abstract

This paper summarises a two dimensional numerical study of the performance of an evaporator of a window type air conditioner. The analysis of the performance of the heat exchanger is done using software ANSYS CFD with finite volume discretization. For the study a couple of commercially available sizes of copper pipes were considered. Six transverse pitch sizes with identical variation between them with an inlet velocity range of 1.5 to 4.0 m/s, the prevalent conditions for Indian window air conditioners were considered as the input data. The objective of the investigation is to understand the effects of transverse pitch variation on Nusselt number, heat transfer, pressure drop and friction factor in a tube bank of an evaporator with seven rows of tubes. The above study provides better understanding of the effect on heat transfer due to variation of transverse tube pitch and velocity of fluid flow under constant surface temperature of the tubes through simulation study. The outcome of the simulation revealed that for lower transverse pitch values heat transfer was lower and as the pitch increased the Nusselt number increased so also was the heat transfer. With the increase in tube size there was corresponding increase in Nusselt number and heat transfer. In the airflow direction, the larger diameter tube performed better as compared to inline smaller diameter tube. For the verification and validation of the outcome from this study were compared with the values derived from existing correlations of the earlier published literature. The simulation values of Nusselt number showed a deviation of 8% with the correlated values which are well within the acceptable range. The information from the study can be used to improve the design and operation of heat exchanger units in window air conditioners.

Keywords

• Heat transfer
• Transverse pitch
• Evaporator
• CFD
• Numerical modeling
• Refrigeration