Performance Evaluation of a Compartmented Cooling Coil Using the Monte Carlo Simulation Approach

Abstract

A compartmented cooling coil is a single undivided coil section located in an intermediate point between the upstream and downstream sections of the air handling unit. A thermally insulated metal barrier is provided for the separation of two different air streams that are conditioned through the coil. The coolant flow through the heat exchanger is such that both the air streams encounter each pass of the coolant feed. This paper aims to address the performance of a compartmented coil through the concept of fin efficiency. The compartmented coil geometry involves two distinct sets of air-side characteristics coupled with one set of coolant-side characteristics and it is practically difficult to obtain the values of fin efficiency through empirical measurements alone over a wide range of operating conditions. Hence, the conventional methods of evaluation resort to numerical models for predicting fin performance. The paper questions the validity of certain fundamental assumptions based on which conventional models have been formulated to obtain the local heat transfer coefficient values. A simplified numerical model is formulated and evaluated using a Monte Carlo simulation approach. Performance curves across all ranges of input values are presented and empirical results are used to validate these curves at intermediate values. Results show that air face velocity and surface temperature at a given point on the fin has significant impact on the heat transfer coefficient. It is also shown that for a given fin height of 9.5mm, the assumption of an average heat transfer coefficient as calculated from the LMTD method could vary significantly up to 10% from the predicted results.