Investigation into Operation of Energy-Intensive Heat Exchangers with Many Plates

Heat exchangers in a gas turbine circuit for advanced space power facilities are innovative developments in the field of elaboration of heat exchangers meeting a set of technical and operating requirements. A design of a heat-transfer matrix consisting of a set of biconvex stamped plates with a specific surface relief is proposed. It enables construction of heat exchangers meeting the requirements for strength, stiffness, weight, and size under the specified operating conditions. The results of testing of heat exchangers made of 288 and 450 plates are presented. A nonuniformity of the coolant distribution among heat-transfer panels was found. Under the same operating conditions, it makes the thermal efficiency of a heat exchanger made of 450 plates lower than that of a heat exchanger made of 288 plates. Based on the analysis of test results, a mathematical model has been developed for the thermal and gas-dynamic design calculation of a heat exchanger with an arbitrary number of plates, which takes into account the effect of nonuniformity of the coolant flow through the channels between the plates. The calculation calls for determination of a temperature distribution along the length of each channel considering variable thermophysical properties of the coolant. For the mathematical model, a dimensionless dependence of the resistance coefficient and the Nusselt number on the Reynolds number was found in the Reynolds number range from 500 to 2000. Universal dependences enable simulation in both hot coolant paths consisting of identical interplate channels and cold coolant paths consisting of the same complete and half channels. The correlations for the hydraulic resistance coefficient and the Nusselt number versus the Reynolds number agree well with the known dependences obtained for corrugated heat-transfer surfaces of the same class. The mathematical model has been verified against experimental data. The effect of the scheme of connection of heat exchangers with different number of plates to a gas circuit is examined. The connection schemes are analyzed, and one of them is recommended as the most suitable for practice.