Mathematical model of a loop heat pipe with cylindrical evaporator and integrated reservoir

Abstract

This paper presents a mathematical model of a loop heat pipe (LHP), which has been validated with experimental results. The LHP behavior was then predicted as a thermal control component of a satellite under different scenarios of orbital heat fluxes impression on the condenser–radiator. The mathematical model features the monitoring of the vapor–liquid front in the condenser, as well as the rate of flooding in the compensation chamber. The features of eventual entering of vapor phase in the liquid line and partial condensing of vapor in the vapor line is also embedded in the model. In the LHP condenser, the condensate film thickness in the tube is determined by the solution of the conjugate equations of energy, momentum and mass balance in the control volume, considering shear stress at the interface. Evaporator and compensation chamber are both described by a few transient nodes with generalized thermal and mass links, where the key parameters were adjusted by experimental test results. The evaporator, integrated with compensation chamber, consists of cylindrical stainless steel case with inserted an ultra-high molecular weight (UHMW) polyethylene primary wick and the secondary wick is made with stainless steel mesh. The condenser is a coiled tube thermally connected to an aluminum plate, having a radiator function; acetone was used as the working fluid. The tests conditions have been reproduced in the mathematical model and its parameters were adjusted in order to improve the model capacity to represent the real LHP operation.