Numerical Study For Applying Insulation Material To Holes In Hollow Birck Walls

Hollow bricks are widely used in China to build facades as theirgood thermal performance and light weight. Since the availability offossil-based energy is falling by the day, energy saving has become acommon view for every country around the world. Thus, it is of greatimportance to take measures to improve the insulation performance of theexternal walls of buildings.This paper is aimed at numerically investigating the possibility ofimproving the thermal performance of building external walls (the24wall and the37wall) by self-programming3-D software, which is writtenwith FORTRAN on the base of the finite volume method and caneffectively deal with the complicated heat transfer caused by conduction,convection and surface radiation that happen simultaneously in hollowbricks, through pasting four kinds of different insulation materialsrespectively (0.01、0.02、0.03and0.04W/(m·K)) around the holes in thehollow brick walls. Meanwhile, we have ulteriorly studied the effect of changing the thickness of insulation layer, choosing different mortars andhollow brick materials with different thermal conductivity on theinsulation performance of the24wall. In addiction, this paper makes aprimary study on the inorganic insulation mortar thermal insulationsystem on inner or outer building walls. The numerical results show that:(1) Pasting10mm-thick insulation materials around holes in thehollow bricks can improve the insulation performance of buildingexternal wall obviously. For the case of the24wall built by differenthollow brick, the percentage of improvement varies between19.1%and59.3%; for the case of the37wall, the percentage of improvement rangesfrom16.9%to58.3%. Especially, the optimum insulation effects can bedone when hollow bricks have smaller hole number and larger voidfraction.(2) Except the L1W1H1and L2W1H1, the insulation performance ofthe37wall is superior to the24wall when the hole number is fixed onein the width direction. But the circumstance is contrary when the holenumber is fixed two in the width direction.(3) Higher thermal resistance of the hollow brick wall can beobtained by choosing insulation materials of lower thermal conductivity.Nevertheless, with the hole number increasing, the effect of energysaving is not obvious because of the wall heat transfer is manlyconduction and the insulation material play a smaller role. For the case of L6W2H1hollow brick, the relative increase rate of the24wall and the37wall is just5.5%difference when the thermal conductivity varies from0.04W/(m·K) to0.01W/(m·K).(4) Increasing the thickness of the insulation layer can obtain betterinsulation performance for the hollow bricks owe higher void fraction.(5) For fixed thermal conductivities of hollow brick material andinsulation, the equivalent thermal conductivity of the24wall range withchoosing different mortars. Nevertheless, the optimum configuration ofthe hollow brick is basically unchanged with different mortars within thegiven range (0.125W/(m·K) to0.930W/(m·K)).(6) Even for high-thermal conductivity building materials, pastinginsulation materials around the holes can also achieve good results forhollow brick with high-void fraction. Higher thermal resistance of thehollow brick wall can be obtained by choosing building materials withlower thermal conductivity.(7) For fixed thermal conductivities of hollow brick material, mortarand, the insulation performance of the inorganic insulation on innerbuilding wall is superior to the outer one.