Study on dehumidification performance of closed-loop heat pump drying system with evaporator bypass
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摘要: 针对闭式热泵干燥系统在处理高含水率物料时除湿能力不足的问题，提出一种带蒸发器旁通的闭式热泵干燥系统。建立热泵系统与干燥过程数学模型，利用工程方程求解器(engineering equation solver, EES)进行仿真计算，分析系统除湿特性并筛选工质。结果表明：在旁通比为0.8时，单位能耗除湿量(specific moisture extraction rate, SMER)提高20.1%~28.7%，平均提升23.9%，系统性能系数(coefficient of performance, COP)仅降低7.53%~7.66%，增加旁通可提高系统除湿性能和干燥效率。以COP、SMER等参数为指标，对比4种工质在不同工况下的性能，确定R1234ze(E)为最优工质。实验验证显示，模型模拟值与实测值的相对误差均不超过10%，研究结果可为闭式热泵干燥系统的优化设计提供参考。Abstract: Closed-loop heat pump drying system face the issues of insufficient dehumidification capacity when processing high moisture materials. To enhance the dehumidification capacity and improve the drying efficiency, a closed-loop heat pump drying system with an evaporator bypass was proposed. Mathematical models of the heat pump system and drying process were established. The drying system was simulated using engineering equation solver (EES) to analyzed dehumidification performance and select suitable refrigerants. The results demonstrate that at a bypass ratio of 0.8, the specific moisture extraction rate (SMER) increases by 20.1% to 28.7% (averaging 23.9%), while the coefficient of performance (COP) decreases by only 7.53% to 7.66%. Incorporating a bypass significantly improves the system's dehumidification performance and drying efficiency. Using COP and SMER as indicators, the performance of four refrigerants under different working conditions was compared, identifying R1234ze(E) as the optimal refrigerant. The system model was validated experimentally, with relative errors between simulated and measured values remaining within 10%. These findings provide a reference for the optimal design of closed-loop heat pump drying systems.
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Key words:
- heat pump drying /
- air bypass /
- dehumidification rate /
- performance optimization.
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图 5 冷凝温度对工质冷凝压力的影响
Figure 5. Effect of condensing temperature on condensing pressure of refrigerants
图 6 冷凝温度对压缩比与排气温度的影响
Figure 6. Effect of condensing temperature on compression ratio and exhaust gas temperature
图 8 蒸发温度对单位容积制热量及压缩比的影响
Figure 8. Effect of evaporation temperature on heat production per unit volume and compression ratio
表 1 实测数据与模拟值对比
Table 1. Comparison of test data and simulation
参数 10 ℃/50 ℃ 20 ℃/70 ℃ 测试 模拟 相对误差/% 测试 模拟 相对误差/% 吸气温度/℃ 5.80 5.00 13.79 21.60 20.00 7.41 排气温度/℃ 64.10 66.40 −3.59 85.80 86.50 −0.82 蒸发出风温度/℃ 21.40 19.10 10.75 26.40 26.70 −1.14 吸气压力/MPa 0.28 0.29 −3.57 0.40 0.41 −2.50 排气压力/MPa 1.30 1.32 −1.54 2.14 2.11 1.40 除湿量/kg 10.52 9.66 8.17 15.9 16.3 −2.52 总耗功/kW 4.60 4.50 2.17 5.92 6.13 −3.55 SMER 2.28 2.14 6.14 2.69 2.67 0.74 
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