| In the development of the steady state sensible performance model, a multi-row multi-pass complex crossflow gas-to-liquid heat exchanger was considered. Several circuiting configurations such as overall counter crossflow, overall parallel crossflow, and fluids in parallel in one of the streams were considered. A new concept termed the "matrix approach" was introduced to study the overall performance of the heat exchanger. The matrix approach was validated by comparing the results from the model with performance predictions from previous studies for several complex heat exchanger geometries available in the literature. Additionally, the matrix approach was also validated by comparing the results from the performance model with limited actual data from a chilled water coil used in a chemical facility in Chattanooga, TN. The advantages of using the matrix approach were finally presented.;The transient finite difference sensible performance model considered a single pass crossflow heat exchanger, and accounted for variations of inlet temperature and mass flow rate as a function of time. The model developed a numerical scheme to determine the transient behavior of a single pass crossflow heat exchanger using the implicit finite difference method. The dynamic response of a heat exchanger in response to perturbations in temperature and flow rates was addressed. In addition, the transient finite difference performance model was further extended to address multi-pass counter crossflow heat exchangers, where the fluids were unmixed in a pass and were mixed between the passes. To validate the transient performance model, the steady state results from the transient performance model were compared with the results from the steady performance model. |
