重力热管供热对葡萄越冬根区的增温效应

葡萄是宁夏特色优势产业，越冬冻害是制约贺兰山东麓葡萄产业可持续发展的关键问题之一。为解决葡萄越冬根部冻害问题，该研究设计了利用浅层地下水地热能进行葡萄根区土壤增温的重力热管系统；通过数值模拟解析不同间距条件下重力热管温度场影响范围及分布规律，通过现场试验研究重力热管的工作特性及对土壤的增温特性。结果表明：土壤温度场以重力热管为中心向四周扩散，热管中温影响区水平方向直径为30.8 cm，竖直方向直径为32.8 cm；在埋深10 cm，相邻热管间距15 cm条件下热管周围温度场部分区域重合，温度场分布均匀；试验期间试验组土壤温度较对照组平均升高7.0 ℃，增温效果明显；重力热管正常运行期间蒸发段凝结段之间最大温差为3.7 ℃，蒸发段内最大温差为1.0 ℃，绝热段内最大温差为0.2 ℃，表现出了良好的等温性；热管平均启动温差为5.4 ℃，平均运行温差为2.9 ℃；研究结果将为解决葡萄根区冻害问题以及探索浅层地热能利用新途径提供理论依据和技术支撑。

Warming effect of grape overwintering root zone using gravity heat pipe heating

The Eastern Helan Mountain can be the largest concentrated and contiguous producing areas for the wine grape in China. Specifically, the wine grape planting area reached 388.7 square kilometers in Ningxia by the end of 2022, accounting for nearly 1/3 of the nation, and the comprehensive output value exceeded 30 billion Yuan. However, the extremely low temperatures (down to -30.0℃) in winter in the eastern part of the Helan Mountains can lead to the occurrence of overwintering frost damage, which greatly limits the sustainable development of Ningxia's grape industry. In this study, a gravity heat pipe system was designed using shallow groundwater geothermal energy for the soil warming in the root zone of grapes. Numerical simulation was also carried out to analyze the influence range and distribution of the gravity heat pipe temperature field under different spacing. A series of field experiments were used to verify the working performance of the gravity heat pipe and the warming characteristics of the soil. The results show that the soil temperature field was evenly spread around the gravity heat pipe. The temperature field around the heat pipe was divided into four regions, according to the temperature level: the temperature range was 5.0-8.50℃ high-temperature affected region Ⅰ, the temperature range was 0-5.0℃ medium-temperature affected region Ⅱ, the temperature range was -2.57-0 ℃ low-temperature affected region Ⅲ, and the temperature field was not affected region Ⅳ. The highest temperature (8.50 ℃) appeared in the temperature field area Ⅰ condensation section pipe wall, whereas, the lowest temperature (-2.57 ℃) was in the temperature field unaffected area Ⅳ. In addition, the diameter of the medium temperature affected area of the heat pipe in the soil was 30.8 cm horizontally and 32.8 cm vertically, where the grape roots were not affected by frost. There were evenly distributed temperature fields around the heat pipes partially overlapped and the temperature fields under the conditions of 10 cm burial depth and 15 cm spacing between adjacent heat pipes. The soil temperature increased by 7.0 ℃ on average in the experimental group during the test period, compared with the control group, indicating the outstanding increase in temperature. The maximum temperature difference was 3.70 ℃ between the evaporation and condensation sections during the normal operation of the gravity heat pipe. The maximum temperature differences were 1.0 and 0.2 ℃ within the evaporation section, and within the adiabatic section, respectively, indicating the excellent isothermal distribution. The average start-up and operating temperature difference of the heat pipe were 5.4 and 2.9 ℃, respectively. The clean and renewable shallow geothermal energy was taken as a source of heating energy in the root zone of grapes, which was in line with the current green development concept. The finding can provide the theoretical basis and technical support to treat the frost damage in the root zone of grapes. In addition, a new way was proposed to realize the development and utilization of shallow geothermal energy using gravity heat pipes.