Abstract:

Pointing at the unfavorable conditions and improving the reliability of the drying system, a coupled application scheme of low-temperature heat pump(LTHP) and dry heat pump(DHP) is proposed, according to the principle of two stage compression refrigeration cycle. By using the exergy analysis model, the exergy loss of the heat, the mass diffusion of the drying medium and the dehumidification process were analyzed respectively to the drying system. With the LTHP at 20, 22, 24, 26, 28, 30℃ and closed, the experiment tests and calculates the exhaust temperature and energy consumption of the compressor of DHP, coefficient of performance and the thermodynamic perfect degrees. The drying time and energy consumption of the system were measured when the water content of wood was decreased by 1%, at different heating temperatures. The results show that:compared with shutting down the LTHP, the exhaust temperature of the drying heat pump is reduced by 16℃ at most, and all the performance coefficient of the heat pump is improved. By the increase of the temperature of the machine hall, the irreversibility of the system cycle increases, and the thermodynamic perfect degrees decreases gradually. After opening the LTHP, the maximum amount of heating load and the drying time of the DHP increases by 44% and decreases by 46%, respectively.

Key words: drying, heat pump, exergy, model, COP, thermodynamic perfect degrees, heating load

摘要：

针对木材干燥中的不利工况，提高干燥系统的可靠性，根据两级压缩制冷循环原理，提出了低温热泵和干燥热泵的耦合应用方案。使用能量的（火用）损失模型，分别对干燥系统进行热量、干燥介质的质扩散和除湿过程的（火用）损失进行分析。在低温热泵20、22、24、26、28、30℃以及关闭低温热泵的供热情况下分别测试计算了干燥热泵压缩机的排气温度与能耗、热泵性能系数（COP）以及热力完善度，同时测得木材含水率下降1%，系统的干燥用时和能耗。结果表明：相比于关闭低温热泵，开启低温热泵后干燥热泵的排气温度最多减少了16℃，COP皆有所提高。由于主机室温度升高后，系统循环的不可逆程度增加，热力完善度随着供热温度增加逐渐降低。开启低温热泵后干燥热泵的供热量和用时比关闭低温热泵最大分别增加44%，减少46%。

关键词: 干燥, 热泵, (火用), 模型, COP, 热力完善度, 供热量