Analytical expression of indoor temperature distribution in generally ventilated room with arbitrary boundary conditions

Abstract

The indoor temperature of a ventilated room is influenced by the airflow pattern, convective heat, and indoor heat sources. The influences of the thermal factors on indoor temperature are different, and vary with location. Though the influence of supply air and heat source can be estimated previously, the influence of convective heat is coupled with indoor temperature thus it has not been clearly investigated. However, the convective heat plays an important role in total building heat transfer. To determine the explicit influence of each thermal factor (especially the heat convection), the theoretical expression of the indoor temperature distribution of steady-state cases is established based on previous research. Three indices: the modified accessibilities of the supply air, ambient temperature, and heat source are used to reflect the explicit influence of different types. The distributions and influencing factors of the three modified indices are analyzed through case studies. The results indicate the following: (1) The influence from the convective boundary is of significance, e.g., the contribution of the water temperature of convective terminals exceeds 0.4 in most studied cases thus it is more reasonable and accurate to reflect the influence by the corresponding ambient temperature; (2) The influence degree of each thermal factor is determined by the flow field and heat transfer coefficient of the convective boundary, e.g., the contribution degree of the supply air is reduced from 0.43 to 0.35 when ventilation rate is reduced by half; and (3) Because the energy grades of the supply air and convective boundary are different, more low grade energy can be used to control the temperature in the target zone to save energy in a non-uniform indoor environment. Succinctly, the established expression can reveal the mechanism of the temperature distribution and provide guidance for the establishment of an energy-efficient non-uniform indoor environment.