空调器用换热器的换热量衰减率测试方法

为了快速评估空调器用换热器长期运行后的换热量衰减情况,本文提出一套通过测试换热器加速积尘前后的换热量来预测其换热量衰减率的测试方法。该测试方法中,采用负反馈模式精确调节换热器迎风面的粉尘浓度,能够在加速积尘时间内维持换热器迎风面粉尘浓度的稳定性;通过对加速积尘循环空间与换热量测试风道进行一体化设计,能够在不需要移机时实现加速积尘与换热量测试之间的切换。在入口空气温度为45℃、流速为1. 5 m/s,入口水温为21℃、流速为0. 5 m/s的工况下对该测试方法的可靠性和一致性进行了验证,结果表明:换热器迎风面粉尘浓度能够稳定维持在目标浓度120 mg/m3,波动范围在±20%内;对4种具有不同结构的换热器样件进行了多次换热量衰减率测试,其换热量衰减率相对偏差均在±10%之内,表明该测试方法具有较好的一致性。

Measurement Method of Heat Transfer Capacity Attenuation Rate of Heat Exchangers for Air Conditioners

In order to quickly evaluate the attenuation rate of the heat transfer capacity of heat exchangers used in air-conditioners after long-term operation, a method for predicting this attenuation rate is established by measuring the heat transfer capacity of a heat exchanger before and after dust-accelerating tests. In this test method, the dust concentration on the windward side of the heat exchanger is accurately adjusted by using the negative feedback mode, which can maintain the stability of the dust concentration on the windward side of the heat exchanger during the dust-accelerating testing period. The placement of the heat exchanger sample can be fixed during the dust-accelerating and heat transfer capacity tests by combining the dust box and air duct. The reliability and repeatability of the test method are verified under the condition of inlet air temperature of 45 °C, air flow rate 1.5 m/s, inlet water temperature 21 °C, and water flow rate 0.5 m/s. The results show that the dust concentration on the windward side of the heat exchanger can be maintained at the target value of 120 mg/m3 and the fluctuation range is within ±20%. The heat transfer capacity attenuation rates of four types of heat exchanger samples with different structures are measured several times, and the relative deviations of the attenuation rates are within ±10%, implying that our test method has good repeatability.