严寒地区设施牛舍太阳能聚光集热土壤供热过程热特性分析

    Thermal characteristics analysis of solar concentrating soil heating process for facility cowshed in severe cold areas

    • 摘要: 严寒地区设施牛舍在冬季养殖过程中温度低、湿度大、空气质量差,舍内乳肉牛易出现冷应激反应,而传统供热方式能耗高、风险大、效果差,阻碍了设施养殖的规模化发展。鉴于此,该研究提出一种可为设施牛舍供热的太阳能聚光集热牛床土壤供热系统,首先介绍了系统与设施牛舍集成后的结构和运行原理,并对位于呼伦贝尔市的系统热特性展开了测试分析,在此基础上,对比研究了供热系统在非供热和连续供热时的牛床土壤温度,分析了土壤温度沿竖直方向、水平方向的分布特性。结果表明,系统在1月份运行时,其供热温度、集热温差和换热效率分别为50.3 ℃、30.4 ℃和71.81%。连续供热时,0.7 m深处的土壤温度可达2.7 ℃左右,当系统停止供热后,土壤温度呈现明显降低的趋势;在系统连续供热的条件下,牛床不同位置处土壤的温度均呈现持续升高的变化趋势,且沿土壤竖直深度的增加而升高,深度为0.7 m处土壤的平均温度分别比0.1 、0.3 和0.5 m处高11.1 、9.2 和5.8 ℃,在与换热管路平行的水平方向,换热管路高温端和低温端处土壤的温度升高值分别为6.8 ℃和4.0 ℃;在垂直换热管路的方向,换热管路正上方土壤的温度升高值和升温速率分别比偏离换热管路0.8 m处的高3.9 ℃和0.3 ℃/d。研究结果可为严寒地区设施牛舍绿色低碳供热技术的应用提供参考。

       

      Abstract: Cattle are prone to cold stress in a facility cowshed during winter breeding in severe cold regions, due mainly to the low temperature, high humidity, and poor air quality. There are some symptoms, such as loss of weight, reduced immunity, high incidence of diseases, and limited growth and development. However, the conventional heat preservation of the facility cowshed can hinder the scale of the aquaculture, such as the large energy consumption, high risk, high cost of facilities, uneven heating, difficult operation and maintenance, as well as the contradiction between ventilation and heating. In this study, a solar concentrating soil heating system was proposed for the cattle bed of the facility's cowshed. Solar energy was adopted as the heat source, the air as the heat transfer medium, and the soil under the facility cowshed as the heat storage and supply carrier. The low-carbon, low-cost cost and convenient maintenance were obtained to introduce the structure of the heating facility cowshed. The heating performance in Hulunbuir was evaluated to calculate the heating temperature, temperature difference, and heat transfer efficiency of the whole system. The soil temperature data of the cattle bed were tested and collected in the continuous heating and non-heating periods of the system. Furthermore, a systematic investigation was then made on the multi-dimensional distribution of the soil temperature on the cattle bed along the vertical, horizontal, and the direction vertical to the heat exchange pipeline. The results indicate that there was a periodic variation in the heating temperature and temperature difference of the system in the effective heating period of 5 h per day, which reached 50.4 and 30.4 °C, respectively. In addition, the highest and average heat transfer efficiency of the heat exchange unit were 71.81 % and 56.10 %, respectively. When the system is continuously heated, the soil temperature at a depth of 0.7 m is stable at about 2.7 °C. There was a significant decrease in the soil temperature as the system stopped the heating. There was an increasing trend in the soil temperature at the different positions of the cattle bed during continuous heating. While there was an increase in the soil temperature, with an increase in the soil vertical depth. The average temperature of the soil at 0.7 m was 11.1, 9.2, and 5.8°C higher than that at 0.1, 0.3, and 0.5 m, respectively. In the horizontal direction parallel to the heat exchange pipe, the soil temperature and temperature increment at the high temperature end of the heat exchange pipeline were higher than those at the low temperature end. Among them, the soil temperature increment and temperature rising speed at the high- and the low-temperature end were 6.8 ℃, 0.6 ℃/d and 4.0 ℃, 0.4 ℃/d, respectively. In the direction of the vertical heat exchange pipeline, there was the highest value in the soil temperature increment and temperature rising speed above the heat exchange pipeline, which were 3.9 ℃ and 0.3 ℃/d higher than those of the soil at 0.8 m away from the heat exchange pipeline. The finding can also provide a strong reference for the green low-carbon heating of facility cowsheds in severe cold areas.

       

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