A novel technique for computationally efficient consideration of cross-fin conduction in fin-and-tube heat exchanger models

Abstract

Accurate predictive tools for fin-and-tube heat exchangers operating under part-load conditions are critical for cost effective design of modern unitary equipment. Traditional attempts to increase model part-load performance employ thermal resistance networks to calculate conduction between neighboring tubes to increase accuracy. This often leads to prohibitive computational cost.This paper presents a fin discretized model (FD model), a novel segment-by-segment model of a fin-tube heat exchanger that eliminates the need to calculate the conduction between the adjacent tube segments through the fins (e.g. “cross-fin conduction”) by reassigning the fin surface areas. This fin area reassignment decreases the simulation time considerably because it reduces the number of variables a heat exchanger model has to iterate for (i.e. wall temperatures of all the tube segments), greatly reducing computational cost.The model's predictions are compared against the detailed segment-by-segment model with cross-fin conduction functionality previously presented by Sarfraz et al. (2019). The experimental results for an air-to-water heat exchanger are used for performance comparison purposes. A preliminary set of results confirm that the FD model works well and captures the cross-fin conduction effect in overall capacity prediction even when the contribution of cross-fin conduction to the overall capacity is significant. The model predicted coil capacity agreed within 1% with the model described in Sarfraz et al. (2019) with the cross-fin conduction functionality under the part load condition.