The impact of exterior surface convective heat transfer coefficients on the building energy consumption in urban neighborhoods with different plan area densities

Abstract

In the urban micro-climate environment, the exterior surfaces’ convective heat transfer coefficients (CHTCs) influence simulated building's energy consumption and exterior surface temperatures. This study first investigated the CHTCs at the external windward, leeward, and roof surfaces of a building located in an urban neighborhood with different plan area densities. New CHTC correlations were defined using the plan area density (λp), local velocity (Uloc), and temperature difference (ΔT), and then evaluated in the EnergyPlus simulation program. These new correlations and other commonly used correlations were employed to quantify the impact of CHTCs on the simulation results. The results show that the total cooling energy consumption increased by 4%, and the total heating energy consumption decreased by 1.3% when the plan area density increased from λp=0.04 (almost isolated building) to λp=0.44 (denser cities) due to the convective heat transfer from exterior building surfaces. With variable exterior surface CHTCs, the exterior surface temperature comparisons resulted in maximum temperature differences of 9.1K and 3.6K for the exterior south and north walls, respectively. Overall, this study quantified the impact of exterior surface CHTC correlations on the simulations results that directly impact the urban micro-climate.