Based on the refrigerant state, divides a heat exchanger into three zones with zoned lump method, i. e. superheat, two-p采用分区参数法将换热器按制冷剂状态分为过热、两相、过冷三区，分别计算了各区的换热温差、传热系数等。
The absence of both high and low side service valves precluded measurement of superheat and subcooling correctly.在上面和下面都应该安装检修阀,以便温度过高和过低时能够准确的测量.