风冷热泵冷热水机组动态过程仿真

DYNAMIC SIMULATION OF AIR-TO-WATER DUAL-MODE HEAT PUMPS

本文给出了风冷热泵冷热水机组动态过程模型。系统的高、低压段被分成制冷剂侧、管壁、以及水或空气侧三个控制容积。针对每个控制容积建立了质量和能量平衡的微分方程。由于压缩机、热力膨胀阀阀体、以及四通换向阀具有较小的热惯性,因而采用稳态模型描述压缩过程、膨胀过程、以及内泄露过程。膨胀阀感温包中的制冷剂温度对于蒸发器出口温度的延迟用一阶惯性环节来描述。通过“预测-校正”和“自适应步长”方法实现系统仿真。仿真结果与测试数据吻合良好。

A dynamic model of air-to-water dual-mode heat pump is presented here. The high-pressure and low-pressure segments are divided into three control volumes, including the refrigerant inside tube, the tube wall and the fluid outside tube that is water or air. Time dependent ordinary differential equations are obtained from the mass and energy balances for each control volume. As the compressor, thermostatic expansion valve (TEV) body and reversing valve have very small thermal inertias, steady-state models are applied for the compression, throttling and leakage processes. The relationship between the temperature of the saturated liquid-vapor mixture in TEV's bulb and the temperature of the refrigerant vapor at the evaporator exit is described with a time dependent ordinary differential equation. System simulation is finally carried out with 'predictor-corrector' and 'adaptive integration step' methods. Simulated results are in good agreement with the measured data.