Numerical simulation of boiling temperature dynamics in two-phase refrigerant flow in horizontal pipes

摘要

The transient dynamic characteristics of shell-and-tube multi-pass heat exchanger-evaporator of vapor compression cooling system are studied. Based on the balance of thermal power and the criterial heat transfer equations the mathematical model of the physical processes taking place in the heat exchanger-evaporator is compiled. The change in the coefficient of heat transfer due to a change in the two-phase regime of the working refrigerant flow is taken into account, as well as the change in time of the mass and vapor content of the working refrigerant in the evaporator over time. The change in time of the mass flow of the working refrigerant at the start of the cooling system from the standby mode is determined using the specified function of changing shaft speed of the compressor in time. The simplifying assumptions accepted for compilation of the mathematical model are listed. The differential equation of evaporation temperature dynamics is solved by the fourth-order Runge-Kutta method with a fixed step. The change in evaporation temperature in time at two values of the ambient temperature is studied. The existence of abrupt drop zone of evaporation temperature on the transient characteristics within 0.1 seconds after the system start from standby is revealed and explained.