Optimization Analysis of Printed Circuit Heat Exchanger Used for Humid Air Turbine Cycle by Economy and Irreversible Loss Evaluation

Abstract

The printed circuit heat exchanger (PCHE) is a prospective candidate with great application potential in humid air turbine cycles due to its high efficiency and compactness. In the present study, a one-dimensional heat transfer and flow resistance model of both straight and zigzag channels was established based on segmental thermal design. The impact of moisture content on thermal hydraulic characteristics, entropy generation, and entransy dissipation of PCHE was evaluated. A two-objective optimization of PCHE for the heat exchange process between flue gas and compressed air was performed. The cost, thermal effectiveness, entropy generation number, and entransy dissipation number were selected as the optimization objectives. The results indicate that as moisture content increases from 0 to 0.15 kg/ kg(d), the j factor decreases by 3%, the effectiveness reduces by 1.6% (straight channel) and 0.9% (zigzag channel), and the entropy generation number and the entransy dissipation number increase by 1.4% and 3.2%, respectively. Therefore, the heat recovery margin in the recuperator design should be amplified to meet the operation conditions of the variable moisture content. The entransy dissipation number of zigzag channels is 1.2 times greater than that of straight channels, which effectively distinguishes the irreversible loss of air in PCHE channels. The criteria to evaluate the optimization of entransy dissipation number is more comprehensive, as the coverage of effectiveness based on entransy dissipation number is broader than that of the entropy generation number, which changes from 0.716-0.788 to 0.769-0.788. The trade-off of cost and irreversible loss needs to be considered in application optimization.