Multi-passage concept applied to water-air cross flow tubes-and-fins heat exchangers – Thermal modelling and feasibility study

Abstract

In this paper, a contemporary concept that is based on dividing, by means of multi-passages, the water flow rate of water-air cross flow heat exchangers (HXs) is proposed. The thermal performance of water-air cross flow heat exchangers varies through a rationale function when the water flow rate changes. The new concept is based on dividing high flow rates of water entering a water-flow heat exchanger into several passages. This fragmentation prevents keeping the thermal performance from being nearly constant at high flow rates which lead to increasing the thermal performance globally. The feasibility of this concept was examined and had been proven through calculations on a double passage heat exchanger using an in-house two-dimensional computational code that had been developed and validated to evaluate the thermal performance of Heat Exchangers (HX) using a prescribed set of parameters. It was observed that the thermal performance increases rapidly with the water flow rates at low flow rates and become nearly constant at high flow rates. Furthermore, results revealed that the implementation of the novel concept can increase the thermal performance of a standard water-air cross flow heat exchanger by up to 25.7 %. The enhancement is more significant at high mean air velocities and low water flow rates.