Abstract
The article presents the solution of heat balance equation system, describing heat exchange processes in ventilated envelopes, which was applied to derive formulas for the calculation of temperatures in the ventilated layers of the envelopes. The accurateness of the formulas was assessed by experimental research and analysis of the calculation results. During the process of heat exchange balance equation solution, the equations were simplified by introducing the following restriction into the derived formulas: they may only be applied for the ventilated envelopes with steel or similar coatings as their external layers, i.e. coatings having small heat capacity and minor difference between the external and internal surface temperatures. The derived formulas enable the calculation of the temperatures of the ventilated envelopes in the distance which does not exceed a half of the ventilated air gap length measuring from the air entrance into the gap. However, this restriction does not impede the estimation of the average thermal indicators of the ventilated envelopes.
Highlights
In the European Union, considerable attention is directed towards reducing the use of energy in buildings; in the future, only low energy buildings are going to be constructed (Directive 2010/31/EU 2010)
The article presents the solution of heat balance equation system, describing heat exchange processes in ventilated envelopes, which was applied to derive formulas for the calculation of temperatures in the ventilated layers of the envelopes
During the process of heat exchange balance equation solution, the equations were simplified by introducing the following restriction into the formulas for the calculation of temperatures θa.g.air, θins.se and θec.se: the equations may only be applied for the ventilated envelopes with steel or similar coatings as their external layers, i.e. coatings having small heat capacity and minor difference between the external and internal surface temperatures
Summary
In the European Union, considerable attention is directed towards reducing the use of energy in buildings; in the future, only low energy buildings are going to be constructed (Directive 2010/31/EU 2010). HGL through roofs and other non-transparent envelopes are mostly influenced by the following climatic impacts: outdoor temperature, wind speed, solar radiation and long-wave radiation from sky (Filho et al 2011). These climatic impacts are differently absorbed by the envelopes of the same type, because other factors, such as specific construction and surface qualities of envelopes, are influential. The surface temperature poses the main problem in the calculation process because its value depends on both heat transmittance of the envelope and climatic impacts (outdoor temperature, wind speed, solar radiation and long-wave radiation from sky). Monstvilas et al On the solution of energy balance equation system to predict temperature distribution
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