| Thermal bridges between exterior wall panels of prefabricated building and that between wall panels and main structural components such as beams and columns have an important influence on the thermal performance of enclosure structure.Reasonable consideration of the influence of thermal bridges is important for building energy-saving analysis,accurate calculation of Heating Ventilation Air Conditioning(HVAC)load,and reasonable selection of HVAC equipment.Combined with theoretical analysis,physical experiment and numerical simulation,the influence of thermal bridges on the thermal performance of the reinforced concrete frame structure prefabricated building modular wall panel connection part is studied.The correction method and the treatment measures considering the influence of thermal bridges are proposed.The main conclusions are as follows:(1)The structural form of the thermal bridge at the connection part of the ALC modular wall panel and the main structure is analyzed,the spatial distribution characteristics of temperature field at the connection part of wall panel is determined.The 3-D model of heat transfer of thermal bridge at the connection part of wall panel is established,then the model is solved by the method of numerical simulation.Meanwhile,a related physical experiment has been carried out to verify the reliability of the solution,the results show that both results are consistent.(2)The inter surface temperature fields of thermal bridges of 8 types of connection structure in ALC modular wall panel in reinforced concrete frame structure in the form of prefabricated building wall panels and beams,columns are numerically simulated.A method for determining the influence area of thermal bridge is proposed.(3)The heating load of the influence area of thermal bridge is calculated with the unsteady method under different premises which includes no solar radiation and solar radiation in different directions.The total energy consumption of a wall unit with a certain width and height under 4 connection forms including outsourcing horizontal wall panel,outsourcing vertical wall panel,embedded transverse wall panel and embedded vertical wall panel is obtained.The effective thermal conductivity of wall panels in 5 different bay sizes including 2.4m,3.0m,3.6m,4.2m and 4.8m is modified by isothermal method,and the related correction factors are obtained.(4)The effect law of heat bridge on heating energy consumption of a 6-story 4-unit prefabricated residential building under the preconditions of no solar radiation and solar radiation in different directions is studied.The results show that when there is no solar radiation,the energy consumption for building heating increases the most with embedded vertical wall panel,followed by embedded horizontal wall panel,outsourced vertical wall panel,and outsourced horizontal wall panel,the proportion of energy consumption increase is 9.37%,8.64%,7.30% and 6.28%.To achieve the same indoor heat consumption,the thickness of the ALC module wall panel needs to be increased respectively 50 mm,50mm,40 mm and 35 mm.When considering solar radiation,the proportion of energy consumption increase is 7.40%,6.17%,5.35% and 4.32%.To achieve the same indoor heat consumption,the thickness of the ALC module wall panel needs to be increased respectively 40 mm,40mm,30 mm and 25 mm.(5)A measurement using external thermal insulation to avoid the harm of thermal bridge is proposed.The effect of thermal bridges on the thermal performance of ALC modular wall panel in the connection part under the form of external thermal insulation is studied.The results show that compared with the form of internal thermal insulation,the affect area of heat bridge and the influence of heat bridge energy consumption for building heating and design thickness of wall panel are lower with the form of external thermal insulation.There are 64 figures,31 tables and 89 references. |
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