用于冬季葡萄根系土壤增温的混合重力热管温度响应及热性能分析

    Analysis of temperature response and thermal performance of hybrid gravity heat pipes for winter soil warming of grapevine root systems

    • 摘要: 重力热管是一种高效的传热设备,在浅层地热能的开发方面具有巨大潜力。为提高冬季葡萄根系土壤的温度,该文设计并测试了一种新型混合重力热管(hybrid gravity heat pipe,HGHP)。HGHP由铜和聚丙烯无规共聚物(polypropylene random,PPR)材料组成,其中铜用于蒸发段和冷凝段,PPR用于绝热段。研究比较了HGHP与传统铜重力热管(copper gravity heat pipe,CGHP)的性能。结果显示,与对照组相比,CGHP和HGHP分别使土壤温度提高了4.94 和3.08 ℃,增温效果显著;另外2种热管均表现出良好的等温特性。由于使用了低成本的PPR材料替代昂贵的铜材料,HGHP成本较CGHP降低48.39%,降幅明显。尽管HGHP的热传递性能略低于CGHP,其经济性和可行性使其在地热能开发中具有应用潜力。该研究为降低地热能开发成本提供了可行的解决方案,并为重力热管在农业领域的应用提供了理论依据和实践指导。

       

      Abstract: This research investigates the thermal response and performance of a newly developed Hybrid Gravity Heat Pipe (HGHP), intended to provide soil warming during winter months for grapevine root systems in cold agricultural regions. Utilizing shallow geothermal energy, HGHP technology aims to address the need for an efficient yet economically feasible solution to sustain root temperatures and promote plant growth during colder seasons. The HGHP combines copper in the evaporative and condensative sections with Polypropylene Random Copolymer (PPR) in the adiabatic section, presenting a cost-efficient alternative to traditional all-copper heat pipes. The study was conducted in a vineyard region in Ningxia, China, where harsh winter temperatures have a significant impact on grapevine productivity and survival. The primary objective of this study was to evaluate the HGHP’s efficacy in increasing soil temperatures at grapevine root zones and to compare its thermal efficiency and economic benefits against the conventional Copper Gravity Heat Pipe (CGHP). This comparative analysis investigates the feasibility of HGHP in agricultural applications, focusing on its performance under varying environmental conditions and its ability to maintain a stable thermal environment conducive to grapevine growth. A field experiment was established at a vineyard in the Helan Mountain area of Ningxia, with both HGHP and CGHP installed under similar conditions to ensure an accurate comparison. The design and configuration of both systems were identical except for the materials used in the adiabatic sections. Each pipe’s evaporator was positioned in groundwater to absorb heat, while the adiabatic sections were embedded in soil with insulative covering to minimize external thermal influence. Temperature sensors were placed along each heat pipe’s evaporative, adiabatic, and condensative sections, as well as in surrounding soil, to capture temperature fluctuations. Observations were conducted across 121 days, covering distinct meteorological conditions including cloudy, snowy, extremely low-temperature, typical winter, and high-temperature scenarios to analyze the thermal response, heat transfer efficiency, and stability of both HGHP and CGHP under real field conditions. The results indicate that both HGHP and CGHP effectively increased soil temperatures compared to the control group without heat pipes, contributing to an enhanced thermal environment for the grapevine root systems. The HGHP raised the soil temperature by an average of 3.08 ℃, whereas the CGHP achieved a more substantial increase of 4.94 ℃. Thermal profiles demonstrated that HGHP retained satisfactory isothermal performance, despite being constructed with PPR in the adiabatic section. Notably, CGHP outperformed HGHP in terms of heat transfer capacity due to copper’s superior thermal conductivity, with the CGHP condenser section showing an average temperature increase of 1.21 ℃ over that of the HGHP. However, in high-temperature conditions, the HGHP’s performance declined, with the condenser section reaching equilibrium with the evaporator, indicating cessation of heat transfer. Economically, the HGHP presented a substantial advantage, reducing costs by 48.39% compared to the CGHP. This cost reduction is attributed to the replacement of copper with PPR in the adiabatic section, which significantly lowered material and manufacturing expenses without severely compromising thermal efficiency. This study confirms that HGHP offers a cost-effective and operationally viable alternative to CGHP for agricultural soil warming applications, particularly in low-temperature settings where high thermal efficiency may not be as critical as affordability. The HGHP effectively leverages PPR’s cost benefits while maintaining functional heat transfer characteristics, making it suitable for geothermal applications where budgetary considerations are paramount. Although HGHP’s thermal performance was marginally lower than that of CGHP, the significant cost savings suggest its potential as a scalable solution for sustainable agriculture. Future research could explore improvements in HGHP’s design, especially in enhancing its adiabatic section to improve thermal stability across a broader range of weather conditions. Additional studies may also investigate HGHP’s application in other fields of geothermal energy, extending its utility beyond agriculture and into areas where soil temperature management is crucial.

       

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