装配式配种妊娠猪舍冬季保温与能耗特征

Thermal insulation and energy consumption characteristics of an assembled piggery for breeding and gestation in winter

为了解规模化猪场装配式配种妊娠猪舍冬季保温以及能源消耗情况,通过对试验猪舍围护结构传热系数、墙体内表面温度以及耗热量理论计算与现场试验监测相结合的方法,对猪舍围护结构热工性能与猪舍能耗特征进行分析。结果表明:试验猪舍复合保温墙体主体部位和外保温砖墙墙体的理论计算值分别为0.31和0.23 W/(m^(2)·K),实测传热系数分别为0.39和0.69W/(m^(2)·K),复合保温墙体钢梁部位传热系数的实测值为0.97W/(m^(2)·K)。在试验期间舍外平均温度下,墙体各部位不会产生结露现象,而围护结构彼此的连接处、屋架下弦和钢柱与天棚连接部位则易发生冷凝情况。试验期间,猪舍理论总耗热量和理论+实测总耗热量的平均值分别为10.73和11.84 W/m^(2),该类猪舍围护结构耗热量平均值小于通风耗热量平均值的20%。所需供热量和实际天然气供热量的每日平均值分别为0.28和0.39 kW·h/m^(2)。该研究可为猪舍设计的节能保温方案提供理论依据。

Heat loss can normally occur from the building envelope(wall,roof,glass)and ventilation system of a piggery in winter,due primarily to the large temperature difference between the inside and outside.A heating system can be widely used to recover the heat loss,inevitably leading to a higher energy demand during large-scale pig farming.Alternatively,it is highly required to meet the specific performance of thermal insulation for the envelope,in order to reduce the energy consumption for the better efficiency of environmental control in the piggery.A large number of pig farms have been built to rapidly resume pig production in China at present.Among them,a newly-developed assembled structure was normally adopted,where the ceiling and upper half wall are mostly made of the composite insulation with the profiled steel plates on both inside and outside,and with the stuffed thermal insulation materials in the middle,whereas,the lower half wall is in brick with the outer insulation board.However,there is little research on the thermal insulation effect of such assembled structure so far.This study aims to clarify the heat preservation,thermal performance,and energy consumption characteristics of an assembled piggery for the breeding and gestation in large-scale pig farms in winter.A field test was also conducted in a pig farm in Chengde City,Hebei Province,China.Some environmental parameters were measured in the piggery,including the inner and outer temperature,relative humidity,carbon dioxide concentration,and ventilation rate.As such,the thermal performance of the envelope was evaluated by the theoretical calculation and in situ test.Meanwhile,the heat transfer coefficients were determined for each part of the building envelope,according to the thermal conductivity of the materials and structure design of assembled piggery.The temperature and heat flux were measured at each measuring point on the inner and outer surfaces of the wall.The measured values were then used to calculate the heat transfer coefficient for each part of the wall.Furthermore,the condensation was estimated for the inner surface of the wall,further to compare the dew point temperature from the enthalpy diagram and the inner surface temperature of each part of the wall at the average outer temperature during the test.The thermal bridge was also be identified to measure the inner surface temperature of the envelope using an infrared thermal imager.The total heat consumption was calculated to balance the sensible heat production of pigs,and the heat loss from the ventilation system and the envelope of the piggery.The result showed that the average temperature and relative humidity were 18.7℃and 65.7%,respectively,inside the piggery under an environmental control system,indicating the comfortable range.By contrast,the average temperature and relative humidity were-9.1℃and 55.8%,respectively,outside the piggery during the test period.The ventilation rates were 0.12 and 0.15 m^(2)/(h·kg)in Units 1 and 2,respectively,and the average carbon dioxide concentration was 5939 mg/m^(3)in Unit 1.The measured heat transfer coefficients for the main part of the upper composite insulation half wall and the lower brick half wall with outer insulation board were 0.39 and 0.69 W/(m^(2)·K),respectively,which were 25.8%and 81.6%higher than the theoretically calculated values,respectively.The measured heat transfer coefficient was 0.97 W/(m^(2)·K)for the steel girder part of the upper wall.Moreover,there was no condensation at each part of the wall within the range of temperature and relative humidity inside the piggery under the average temperature outside,indicating better thermal comfort.However,the condensation was easy to occur at the installation joints of doors,windows,fans,cooling pads,and walls,the joints between the upper and lower walls,the joints between the lower chord of the roof frame and the ceiling,as well as the connecting part of the steel columns and the ceiling.In addition,the theoretical total heat consumption of the piggery was 10.73 W/m^(2)on average,and the average theoretical and measured value was 11.84 W/m^(2).Correspondingly,the average heat consumption of the envelope was less than 20%of that of the ventilation in this type of piggery.The daily required heating supply was 0.28 kW·h/m^(2)in theory,where the actual was 0.39 kW·h/m^(2),according to the use of natural gas.This finding can also provide a strong technical reference for the energy saving and insulation of assembled piggery.