Simulation modeling for analysis of effectiveness and prime movers electrical energy demand of liquid coupled energy recovery systems

Realization of anticipated energy efficiency from recuperative liquid coupled run-around energy recovery (LER) systems requires identification of the system components influential parameters and accounting for the prime movers energy requirements. Because simulation modeling is considered as an integral part of the design and economic evaluation of LER systems, it is essential to calibrate the developed models and validate the performance predictions by means of comparison with data from experimental measurements. The objective of this study is to develop a simulation model for a typical LER system that accounts for (a) energy loss from the interconnecting piping, (b) temperature dependency of thermophysical properties, (c) hydraulic pressure drop as a function of liquid Reynolds number and other related physical parameters, such as bends and bypass flow, (d) heat exchangers air side convective transfer coefficients based on recent correlations reported for wavy fins and (e) varying efficiency for prime movers. To achieve the objective, several simplifying assumptions used in previous studies have been relaxed; the interactions between all system components are mathematically modeled; and the latest correlations are utilized. The results from the simulation modeling of this study are found to be within 4% of the experimental data reported in the literature. Because of the dynamics introduced by the operation of the three way valve, controlling the pump and fan motors based on the bypass ratio is recommended, as it would result in better management of the electrical energy demand.