鲍恩财, 张勇, 曹晏飞, 王昭, 张欣, 曹凯, 杨俊伟, 邹志荣. 不同材质传热风道性能及蓄热土壤温度场CFD模拟[J]. 农业工程学报, 2018, 34(4): 232-238. DOI: 10.11975/j.issn.1002-6819.2018.04.028
    引用本文: 鲍恩财, 张勇, 曹晏飞, 王昭, 张欣, 曹凯, 杨俊伟, 邹志荣. 不同材质传热风道性能及蓄热土壤温度场CFD模拟[J]. 农业工程学报, 2018, 34(4): 232-238. DOI: 10.11975/j.issn.1002-6819.2018.04.028
    Bao Encai, Zhang Yong, Cao Yanfei, Wang Zhao, Zhang Xin, Cao Kai, Yang Junwei, Zou Zhirong. Performance of different material heat transfer pipes and CFD simulation of thermal storage soil temperature distribution[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(4): 232-238. DOI: 10.11975/j.issn.1002-6819.2018.04.028
    Citation: Bao Encai, Zhang Yong, Cao Yanfei, Wang Zhao, Zhang Xin, Cao Kai, Yang Junwei, Zou Zhirong. Performance of different material heat transfer pipes and CFD simulation of thermal storage soil temperature distribution[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(4): 232-238. DOI: 10.11975/j.issn.1002-6819.2018.04.028

    不同材质传热风道性能及蓄热土壤温度场CFD模拟

    Performance of different material heat transfer pipes and CFD simulation of thermal storage soil temperature distribution

    • 摘要: 风道在园艺设施中应用较为广泛,通常作为土壤及墙体热量传递的载体。该文搭建了风道传热试验台,以聚氯乙烯管道(polyvinyl chloride pipe,PVC)、镀锌铁皮管道(galvanized iron pipe,GI)及钢筋网外缠绕土工布管道(steel mesh skeleton-geotextile composite pipe,SFG)3种管材作为传热风道,以土壤为蓄热体进行试验,结合计算流体力学(computational fluid dynamics,CFD)对蓄热土壤温度场进行分析。结果表明,SFG的传热效果最好,测试期间的换热量达到299.44 kJ,约是GI的4倍、PVC的3倍;SFG进、出口上、下、左、右4个方向的有效蓄热范围均远大于240 mm,PVC与GI的有效蓄热范围相似;通过CFD所建立的3个传热风道计算模型的最大相对误差为4.4%,模拟发现蓄热土壤截面温度从进风口到出风口具有一定的"坡降"。因此,SFG的传热效果明显优于PVC与GI,具有较高的应用潜力和一定的推广价值。

       

      Abstract: Abstract: Heat transfer pipe has been widely adopted in horticultural facilities, such as Chinese solar greenhouses, which serves as a media to transfer heat between hot air and soil or north wall, and has many advantages such as easier operation, lower cost and better effect. Many scholars have studied the pipe heat transfer performance from piping materials and air flow, and they found the piping material has little influence on heat transfer, but air flow rate has a big influence on heat transfer. However, whether the holes on the heat transfer pipe wall have positive roles in heat transfer is still elusive. Therefore, we compared the heat transfer ability between closed type pipe and breathable type pipe. To study the temperature distribution of thermal storage soil, a typical heat transfer pipe experimental platform with 3 different kinds of pipe material, including polyvinyl chloride (PVC), galvanized iron (GI), and steel mesh skeleton - geotextile composite (SFG), was established in this research. Combined with computational fluid dynamics (CFD) technique, the heat storage experiment on soil was performed. Results showed that there was no temperature and humidity difference at the inlet of heat transfer pipe among 3 kinds of different material, however, the temperature difference was significant at outlet: PVC > GI > SFG; in addition, the humidity level also showed a clear trend of GI > PVC > SFG. This can be attributed to the physical characteristics of SFG such as the high permeability for air and moisture, from which the soil had a chance to absorb both heat energy and moisture from the hot air. Additionally, SFG resulted in the most effective heat transfer activity with a heat exchange amount of 299.44 kJ during the whole test, which was at least 4 times that of GI, and 3 times that of PVC. The location with soil temperature fluctuation more than 1 ℃ is in effective heat range, and that with soil temperature fluctuation more than 5 ℃ is in efficient heat range. The effective heat storage ranges at inlet of SFG were much greater than 240 mm in all 4 directions, i.e. up, down, left, and right direction; the effective heat storage ranges at outlet of SFG were more than 240 mm; the efficient heat storage ranges at inlet of SFG were also more than 240 mm; and the efficient heat storage ranges at outlet of SFG were higher than 240, 180-240, 180-240, and 180-240 mm respectively in the 4 directions. Our results showed that the heat transfer ability of SFG was the best in our experiment, and PVC was slightly better than GI. Therefore, the heat transfer ability of breathable type pipe was better than closed type pipe. Moreover, each CFD simulation model was established individually based on 3 different pipes, with the maximum relative error between measurement and simulation value of 4.4%. Simulated results showed that the temperature was distributed unevenly at the end surface of the soil: a higher temperature at the upper layer, a lower temperature at the lower layer, and a symmetrical distribution between left and right sides. There was also a distinguishable decrement of section temperature between the air inlet and outlet. Therefore, we conclude that SFG performs significantly better than both PVC and GI, which can be potentially applied in Chinese solar greenhouses or other similar agricultural facilities, and/or popularized to the construction market.

       

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