Research And Development Of Novel Heat Preservation Quilts And The Application Effects

The heat loss through the front roof accounts for mort than 70% of the total heat loss of sunlight greenhouse. At present, outside covering materials for heat preservation of sunlight greenhouse include traditional materials, such as straws, and heat preservation quilts. But there are problems of quality unevenness, poor waterproof and pollution to the film, or high price and difficulty in popularization. So the research and development of novel heat preservation quilts (HPQ) of good performance and low cost becomes a necessity.In this study, various materials were selected to make HPQs, and their performances were tested in laboratory. After getting the test results in laboratory, HPQs were remade and their heat preservation performance was tested by field experiment. In the lab test, six HPQs were made, adopting felt, spray-bonded unwoven fabric, coarse wool and Puffed PE as thermal insulation materials, using oxford and waterproof cloth with coat as covering materials, and using aluminum foil as reflecting material. The heat preservation of six HPQs was tested with static hot-box experiment to compare with that of straws and felt quilt with a flat density of 2kg/m2. The waterproof, mechanical strength and resistance to aging of the first three HPQs were tested with weighing method, strength tester and artificial aging. The results were listed as following:(1) HPQ 1 and HPQ 3 whose structure was"outside material + plastic film + core + inside material"showed a better waterproof with water absorption of 3.88% and 6.75%, less than that of HPQ 2, 17.66%. The structure had a perfect property of waterproof.(2) The mechanical strength of HPQ 1, HPQ 2 and HPQ 3 was 324.8, 216.4 and 172.7 N/cm, respectively. The mechanical strength of HPQ depended on the mechanical property of its inside and outside materials (defending layer). Oxford and waterproof cloth with coat had good performance in mechanical strength.(3) The mechanical strength of the first three HPQs declined by 10.2%, 7.0% and 11.3% in turn after the artificial aging. Oxford and waterproof cloth had nicer resistance to aging.(4) The heat-transfer coefficients of the HPQ made of spray-bonded unwoven fabric with a flat density of 400 g/m2 were 3.10 and 3.26 W/(m2·K), less than those of straws (3.52 and 3.61 W/(m2·K)) and those of contrasting HPQ (3.22 and 3.28 W/(m2·K)), under the heating power of 21 and 37 W. The heat-transfer coefficients of the HPQ made of wool with a flat density of 600 g/m2 were 3.42 and 3.49 W/(m2·K), also less than those of straws (3.69 and 3.60 W/(m2·K)) and those of contrasting HPQ (3.64 and 3.53 W/(m2·K)). The HPQ made of spray-bonded unwoven fabric with a flat density of 400 g/m2 or wool with a flat density of 600 g/m2 exceeded straws and the contrasting HPQ in heat preservation.Choosing oxford as inside and outside materials and adopting the structure of"outside material + plastic film + core + inside material", wool HPQ including wool with a flat density of 600 g/m2 and felt wool HPQ including wool interlayer with a flat density of 600 g/m2 were made. Their heat preservation was tested by field small arch greenhouse experiment, compared with felt HPQ with a flat density of 1 kg/m2 and felt HPQ with a flat density of 2 kg/m2, and following results were obtained:(1) The small arch greenhouses covered with the wool HPQ got an average air temperature of 23.1℃and an average soil temperature of 27.7℃, and average heat flow through the wool HPQ was -11.53 W/m2 while its average heat-transfer coefficient was 1.45 W/(m2·K). The ones covered with the felt HPQ with a flat density of 1kg/m2 got the air temperature of 22.4℃and the soil temperature of 27.6℃, and the heat flow through the HPQ was -15.91 W/m2 while its heat-transfer coefficient was 2.43 W/(m2·K). The wool HPQ had a better heat preservation than the felt HPQ with a flat density of 1 kg/m2.(2) The ones covered with the felt wool HPQ got the air temperature of 24.3℃and the soil temperature of 27.6℃, and the heat-transfer coefficient of the HPQ was 1.35 W/(m2·K). The ones covered with the felt HPQ with a flat density of 2 kg/m2 got the air temperature of 23.9℃and the soil temperature of 27.5℃, and the heat-transfer coefficient of the HPQ was 1.39 W/(m2·K). Therefore the felt wool HPQ had a better heat preservation than the felt HPQ with a flat density of 2 kg/m2.Cost analysis indicated that, the cost of wool HPQ and felt wool HPQ was 11.7 $/m2 and 14.3 $/m2, lower than that of felt HPQ with a flat density of 1 kg/m2 and felt HPQ with a flat density of 2 kg/m2, 12.2 $/m2 and 16 $/m2, respectively. HPQs with wool core can act as substitutes to the current felt HPQs.