Construction and Study on Property of Brick with Inorganic Phaze Change Material for Solor Greenhouse
|School||Northwest University of Science and Technology|
|Keywords||solar greenhouse solar energy phase change material calcium chloridehexahydrate phase change brick|
In the past tens of years, facility agriculture in China has developed rapidly, and thedevelopment of solar greenhouses is much more rapid. Compared with the other agriculturalbuildings, the technical content of construction of solar greenhouse is relatively low,systematic standard and guidance of construction technology are deficient, special standard ofconstruction of solar greenhouse and supervision system are more deficient. In the long-termconstruction of solar greenhouse, wall materials are usually clay brick or soil which pollutesenvironment, occupies land, increases cost, so a proper kind of wall material which isenvironmentally-friendly, energy-saving, low-costing is urgently developed. In order to solvethe problem of the solar greenhouse that the temperature of solar greenhouse is low in night,we prepared a kind of shape-stabilized phase change material using a kind of phase changematerial calcium chloride hexahydrate, and prepared a kind of inorganic phase change brickwhich is tested through thermal property and mechanical property.The latent heat which could not be released because of the undercooling of calciumchloride hexahydrate was high, so this experiment aimed at resolving the phenomenon inorder to apply it to the greenhouse. The self-made calcium chloride hexahydrate added withdifferent types and weights of the nucleating/thickening agents was tested and analyzed bysolidification experiments and differential scanning calorimetry (DSC). The experimentshowed that the three kinds of nucleating agents and CMC were excellent, so the problem ofundercooling and phase separation was solved by adding1%borax+1%CMC or1%aluminum+4%CMC or1%sodium silicate+2%CMC to calcium chloride hexahydrate.A kind of CCH/HD shape-stabilized PCM is prepared through the method that hayditeabsorb PCM by vacuum absorption and the thermal storage system calcium chloridehexahydrate+1%aluminum+4%CMC, and tested with properties or analysis. Test resultsindicate that the first and the2000thermal cycle of CCH/HD shape-stabilized PCM arefamiliar, and the chemical stability of phase change material is good after multi-cycles, andthe range of temperature is low too. In the temperature-time test, the change of temperature ofCCH/HD shape-stabilized PCM is small, calcium chloride hexahydrate that haydite absorbshas better thermal storage which indicates that the nucleating and thickening agents still have good nucleation. The results of infrared scan of CCH/HD shape-stabilized PCM indicate thatthe absorption of haydite is good, and the chemical stability of PCM is stable. Thetemperature-time curves of CCH/HD shape-stabilized PCM indicate that calcium chloridehexahydrate which haydite absorbs still have good thermal storage.After preparing bricks, the suitable haydite is weighed according to the ratio of thematerials and encapsulated after absorbed and mixed with other materials to prepare bricks.The results of experiment indicate that haydite does not effect the compressive strength ofconcrete after absorbing PCM. The prepared bricks still have higher compressive strength andcan satisfy the5Mpa of compressive strength of insulating and light bricks, and reaches the5Mpa～15Mpa of compressive strength of structural insulating and light bricks. From thedry apparent density, and in the case of a certain mass fraction of haydite, PCM bricks ishigher than the control group150kg/m3, equivalent to150kg of phase change materials areadded in units of cubic meters of concrete brick, which have a very great help to improve theheat preservation performance of bricks. The water absorption of inorganic PCM bricks isunder2%and the range of the softening coefficient is0.85～0.95that can satisfy therequirements of solar greenhouses. The heat storage coefficient of the inorganic PCM bricksrange from11.850W/㎡·K to13.183W/㎡·K which is suitable for solar greenhouses.