Effect of urban neighborhoods on the performance of building cooling systems

Abstract

This paper quantified the influence of the urban neighborhood on the degradation of Coefficient of Performance (COP) for the building cooling systems. Urban microclimate usually creates higher air temperatures in dense urban areas compared to surrounding rural and suburban regions. Computational Fluid Dynamics (CFD) combined with building energy simulations can predict local hourly temperatures in urban environments. This study uses open source software packages, including OpenFOAM and EnergyPlus, to calculate local air temperatures and heat fluxes on the building surfaces as well as resultant operational COP values. First, the simulated temperature calculations of local airflow temperatures are indirectly validated using on-site field measurements in an actual urban neighborhood. Further, the validated CFD simulations predicted local air temperatures in uniform neighborhoods of varying density. This study identified four types of COP equations to quantify performance of cooling systems as a function of outdoor air temperatures. The study findings indicate that for the present study's climate and flow conditions, rooftop air conditioners in urban areas can have a reduction in COP up to 17%, compared to COP in a corresponding rural area. Window air conditioners can have reductions in COP of over 16%, if located on the windward walls. However, this average COP degradation for the cooling systems installed on the leeward walls is not significant. Overall, the effect of neighborhoods on the performance of cooling systems is significant and quantifiable, and this quantification requires consideration of the common local design practices for the installation of building cooling systems.