Авіаційно-космічна техніка та технологія (Aug 2020)
TWO-TEMPERATURE MATHEMATICAL MODEL OF HEAT CONTROLLED ACCUMULATOR WITH THERMAL REGULATION FOR ZERO GRAVITY CONDITIONS
Abstract
It is advisable to use two-phase heat transfer circuits (TPC) on spacecraft with high heat release in thermal control systems (TCS). TPC has many advantages over single-phase heat transfer loops. In such circuits, heat is accumulated and transferred in the form of latent heat of vaporization. TPC can transfer a much larger amount of heat per unit mass flow rate, the temperature of objects can be maintained almost constant throughout the heat supply area and close to the saturation temperature. Besides, all heat transfer processes occurring during boiling are more intense than with conventional convective heat transfer. Therefore, the mass and dimensions of the TCS based on the TPC will be less than based on single-phase circuits. The thermally regulated pressure accumulator (HCA) is the most important element of the TPC. The article proposes a simplified two-temperature mathematical model for describing nonequilibrium heat-mass transfer processes in HCA under zero gravity. The mathematical model of the HCA is formed using the method of idealized elements. The authors detail the energy conservation equations for control volumes and thermal units, mass conservation equations, equations for heat fluxes and mass sweats. It allows you to quickly carry out the calculation and analyze an acceptable result for preliminary estimates. Previously, the authors published the work, which describes a detailed multi-temperature model that allows us to estimate the nonequilibrium in the liquid phase. A detailed model allows you to calculate almost any process in the HCA with fairly high accuracy, but the program is quite voluminous and the calculation takes a lot of time. Therefore, on the recommendation of the developers of the AMESim software package, the authors formed a simplified two-temperature nonequilibrium HCA model. The model is implemented in Fortran software and tested to establish a quasistationary regime and tested for thermal balance. Based on the data of a space experiment on heating HCA with ammonia, the estimated value of the convective component of heat transfer under zero gravity is estimated. This concept and model can be refined based on the actual design of the accumulator. For example, equations can be written for a cylindrical HCA, placing the heater on the surface of the housing or in the center, etc.
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