鲍恩财, 邹志荣, 张勇. 日光温室墙体用相变固化土性能测试及固化机理[J]. 农业工程学报, 2017, 33(16): 203-210. DOI: 10.11975/j.issn.1002-6819.2017.16.027
    引用本文: 鲍恩财, 邹志荣, 张勇. 日光温室墙体用相变固化土性能测试及固化机理[J]. 农业工程学报, 2017, 33(16): 203-210. DOI: 10.11975/j.issn.1002-6819.2017.16.027
    Bao Encai, Zou Zhirong, Zhang Yong. Performance test and curing mechanism of phase change cured soil for solar greenhouse walls[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(16): 203-210. DOI: 10.11975/j.issn.1002-6819.2017.16.027
    Citation: Bao Encai, Zou Zhirong, Zhang Yong. Performance test and curing mechanism of phase change cured soil for solar greenhouse walls[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(16): 203-210. DOI: 10.11975/j.issn.1002-6819.2017.16.027

    日光温室墙体用相变固化土性能测试及固化机理

    Performance test and curing mechanism of phase change cured soil for solar greenhouse walls

    • 摘要: 中国西北非耕地地区面积辽阔,日光温室的应用可以增加耕地面积,对于保障国家粮食安全、缓解经济作物与粮食作物争地矛盾具有重大的战略意义。该文提出一种在西北非耕地地区建造日光温室用的相变固化剂,研究其添加进土壤后相变固化土的力学及热性能,并结合微观结构揭示其固化机理。研究设计2种相变固化剂掺量(5%和10%),分析不同掺量处理风沙土和戈壁土后的力学性能、热性能以及固化机理。抗压强度试验结果表明,5%和10%相变固化剂掺量的风沙土和戈壁土的抗压强度均有较大幅度的提高,10%相变固化剂掺量的风沙土试块平均抗压强度为3.208 MPa,约为5%掺量试块强度的2倍(P<0.01)。10%相变固化剂掺量的戈壁土试块平均抗压强度为3.671 MPa,约为5%掺量试块强度的1.5倍(P<0.01)。差示扫描量热法测试结果表明,考虑墙体温度>0 ℃的实际状况,5%相变固化剂掺量风沙土吸热量和放热量分别为28.16和29.89 J/g,5%相变固化剂掺量戈壁土吸热量和放热量分别为13.55和12.69 J/g。10%相变固化剂掺量的风沙土与戈壁土吸、放热量均与5%掺量同一类型土壤的吸、放热量相差甚微。扫描电子显微镜观察结果从微观方面解释了相变固化土强度提高和高效蓄放热的机理。该文从试验角度证明5%掺量相变固化剂的风沙土或戈壁土具有作为日光温室墙体的建筑结构和储能主体材料的潜力,在西北非耕地地区将会有较好的应用前景。

       

      Abstract: Abstract: Building solar greenhouse in these non-cultivated lands cannot only make full use of the land resources in the northwest of China, but also has great significance in ensuring national food security. However, traditional solar greenhouses with soil or brick walls often suffer from a huge energy imbalance. In In this study, we designed a phase change materials additive as a soil curing agent (PCC) and used it in sand soil (SS) and Gobi soil (GS) widely distributed in the northwest of China. The new phase change cured soil greenhouse wall materials were designed and their mechanical and thermal properties were evaluated and the curing mechanism was also studied. The main composition of phase change curing agent included phase change material, silicate cement (PO32.5) and powdered Ca(OH)2 at a ratio of 3: 25: 5. The raw phase material was Na2SO4·10H2O : Na2HPO4·12H2O : CaCl2·6H2O : Na2B4O7·10H2O : CMC = 20 : 70 : 8 : 1: 1. All the materials were stored at room temperature before use. The sand soil had the optimal water content of 12% and the dry density of 1.92 g/cm3 of density. The sample Gobi soil had the water content and dry density of 15% and 2.12 g/cm3, respectively. The phase changed cured soil with 5% PCC in SS, 10% PCC in SS, 5% PCC in GS and 10% PCC in GS was prepared with 3 replicates for each treatment. The compressive strength was tested at room temperature. The thermal property was studied by differential scanning calorimetry method. The structure of soil was measured by an electron microscope. The results showed that the average compressive strength of 5% PCC + SS was 1.667 MPa, higher than the international standard for curing sand (1 MPa) and the non-additive SS (0.045 MPa). The average compressive strength of 10% PCC + SS was 3.208 MPa, which almost doubled that of 5% PCC + SS. The compressive strength for 5% PCC+ GS and 10% PCC+ GS was 2.454 and 3.671 MPa, respectively, which were both higher than the average compressive strength of GS (1-1.5 MPa). Both endothermic and exothermic processes appeared in the greenhouse. For the 5% PCC + SS, the endothermic process was from 6.54 ℃ to 42.68 ℃. The maximum endothermic temperature was 33.59 ℃, with the heat absorption of 28.16 J/g. The exothermic process started at 17.12 ℃ and ended at 1.59 ℃. The maximum exothermic temperature was 16.42 ℃ and the overall exothermic volume was 29.89 J/g. In contrast, the heat flow change of the 10% PCC + SS was relatively small. For 5% PCC + GS, an overall similar endothermic and exothermic process was also observed. The endothermic process started at 13.20 ℃ and ended at 37.79 ℃. The maximum endothermic temperature was 31.04 ℃, and the heat absorption was 13.55 J/g. The exothermic started at 15.50 ℃ and ended at 0.05 ℃. The maximum exothermic temperature was 13.73 ℃ and the heat absorption was 12.69 J/g. The heat flow change of the 10% PCC + GS was also very small. These results indicated that 5% PCC and 10% PCC both met the requirement of the greenhouse energy storage. Adding of PCC enhanced the poor connection of original particleS into cementation connection, thereby reducing the holes, enhancing mechanical strength and heat storage. This paper provided valuable suggestions for the utility of SS and GS as fundamental structural materials of solar greenhouses, especially in the wild northwest regions.

       

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