TRANSIENT-RESPONSE OF A SERPENTINE FINNED-TUBE CROSS-FLOW HEAT-EXCHANGER TO A STEP CHANGE IN INLET TEMPERATURE

An analysis of the thermal response of a finned-tube, liquid-to-gas cr oss-flow heat exchanger due to a step change in the liquid inlet tempe rature is performed Closed-form solutions for the liquid and gas tempe ratures as functions of space and time are obtained via the Laplace tr ansform technique for both small and large arguments of the modified B essel function of the first kind. Using four physically important dime nsionless parameters, the response of the liquid and average gas outle t temperatures are studied and presented in the time domain. The analy sis is extended to a single-row serpentine coil geometry by accounting for U-tube bends. Using a typical heat exchanger geometry, the effect s of the tube bends are shown to be significant. Relevant applications include automotive and HVAC heat exchangers and systems.