高萌, 李明, 王云峰, 余琼粉, 李坤, 孙伟, 罗熙. 低温环境下热泵热风干燥藏药性能试验[J]. 农业工程学报, 2020, 36(21): 316-322. DOI: 10.11975/j.issn.1002-6819.2020.21.038
    引用本文: 高萌, 李明, 王云峰, 余琼粉, 李坤, 孙伟, 罗熙. 低温环境下热泵热风干燥藏药性能试验[J]. 农业工程学报, 2020, 36(21): 316-322. DOI: 10.11975/j.issn.1002-6819.2020.21.038
    Gao Meng, Li Ming, Wang Yunfeng, Yu Qiongfen, Li Kun, Sun Wei, Luo Xi. Experimental study on the performance for heat pump hot air drying of Tibetan medicine at low-temperature[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2020, 36(21): 316-322. DOI: 10.11975/j.issn.1002-6819.2020.21.038
    Citation: Gao Meng, Li Ming, Wang Yunfeng, Yu Qiongfen, Li Kun, Sun Wei, Luo Xi. Experimental study on the performance for heat pump hot air drying of Tibetan medicine at low-temperature[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2020, 36(21): 316-322. DOI: 10.11975/j.issn.1002-6819.2020.21.038

    低温环境下热泵热风干燥藏药性能试验

    Experimental study on the performance for heat pump hot air drying of Tibetan medicine at low-temperature

    • 摘要: 为提升低温环境下藏药干燥特性,该研究提出回热、喷焓热泵干燥系统模式,并通过试验探究所设计系统持续运行的稳定性及能效特性,获取低温条件不同方式载物模式下热泵连续运行的特性及变化规律。研究结果表明:在冬季高原严寒大温差(30 ℃)下,回热型热泵系统换热器换热效率平均为13.58%。喷气增焓热泵系统(−13.39~16.69 ℃)最低制热系数COP(Coefficient of Performance, COP)比普通涡旋热泵系统(−11.4~18.3 ℃)提升了51.5%,COP平均提高16.9%,有效提高了低温下系统制热能效。物料摆放方式以及铺料厚度对干燥效果影响显著,当装载量为100%,码放高度20 cm时,物料成品表皮色泽金亮,干燥度均匀,单位能耗除湿量SMER(Specific Moisture Extraction Rate,SMER)大。与传统方式相比,对同等数量的物料,热泵干燥耗时仅为传统阴干方式的1/9,且成本降低1 160元/t,同时避免了环境的二次污染。研究结果表明回热、喷焓型热泵系统能满足低温工况下藏药材干燥所需的能量供给且能够稳定运行。

       

      Abstract: Tibetan medicine has a long history to serveas a national medicine second only to Chinese medicine. Fresh Tibetan medicine cannot be directly used as medicine. Drying process is essential as a preliminary processing step. The heat pump drying method can be suitable for this case, due to its energy saving, environmental protection, and low cost. In this study, a noveldrying system mode of heat recovery andair-jet enthalpy heat pump was proposed to improve the drying characteristics of Tibetan medicine under low-temperature environments. A systematic experiment was conducted to explore the stability and energy efficiency for the continuous operation of system, thereby to obtain the changing characteristics of continuous operation onthe heat pump in different load modes at low temperature conditions. In order to explore the performance characteristics of heat pump drying for the Tibetan medicine at low temperature environment in winter, a drying oven was built with the size of 3.9m ×2.1m ×2.3m (length ×width ×height)and a volume of about 15m3, as well asa rated load of 1.5 t. An ordinary ring scroll compressor,and anair jet enthalpy compressor in a heat pump system were selected to carry out the load experiment test at the ambient temperature of -11.4−18.3 and -13.39−16.69 ℃. The ordinary scroll compressor in a heat pump system workedin the segmented drying mode, and the continuous drying operation mode was used to dry Tibetan medicine. The air-jet enthalpy-increasing heat pump system performedday and night for the continuous drying. Results were as follows: Under the severe cold and large temperature difference (30 ℃) in the winter plateau, the averageefficiencyof heat transfer in the air-jet enthalpy-increasing heat pump system (-13.39−16.69 ℃) was 9.56%, and that in the ordinary scroll compressor heat pump system (-11.88−18.29 ℃) was 13.58%. It infers that the efficiency of heat transferin a heat exchanger was relatively low, asthe ambient temperature decreased.The compressor selection has no significant effect on the heat exchange efficiency of heat exchanger. The minimum coefficient of performance (COP) of air-jet enthalpy-increasing heat pump system(-13.39−16.69 ℃) increased by 51.5%, compared with the ordinary scroll heat pump system (-11.4−18.3 ℃). The average value of COP increased by 16.9% during the whole progress, indicating effectively improved the heating energy efficiency of a system at low temperatures. The placement and thickness of amaterial presenteda significant influence on the drying effect. When the loading capacity of drying box was about 100% and stacking thickness was 20 cm, the finalproduct behavedbright color, uniform drying, and the high specific moisture extraction rates (SMER). Compared with the traditional air-drying method, the drying time of a heat pump was only 1/9 of conventional dry method for the same amount of materials, while,the drying cost was reduced by 1 160 yuan/t. The recoveryandair-jet enthalpy heat pump system can meet the energy supply that required for the drying of Tibetan medicinal materials under the low-temperature conditions.

       

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