Development of a new method for estimating the overall heat transfer coefficient of heat exchangers – Validation in automotive applications

Abstract

Prediction of heat exchangers performance is primordial in the world of machine design especially when the industrial environment becomes demanding in terms of size reducing or price lowering. The most common adopted procedure for this kind of investigation is defining the exchanger's overall heat transfer coefficient with a purely empiric way using interpolations and mathematical operations missing physical senses in the modeling. The present work offers a first step in theoretically modeling the heat transfer coefficient and presents a semi-empirical method which allows expressing the latter in function of the Reynolds' numbers of the fluids' flows when the variations of the Prandtl numbers of the two fluids are small. The method consists in an iterative technique based on a single test approach and allows the prediction of the heat exchanger performance for a large range of flowrates. Experimental validation of the method is performed for a cross-flow heat exchanger with water and air as working fluids, showing a relative error less than 1.6%. The relative error of the mathematical methods applied is less than 1.7%.

Keywords

• New method
• Heat exchangers
• Overall heat transfer coefficient
• Extrapolation
• Automotive applications