Thermal performance prediction of office buildings using direct evaporative cooling systems in the composite climate of India

Abstract

This study predicts the thermal performance of office buildings using Direct Evaporative Cooling (DEC) systems for thermal comfort during the summer season of Indian composite climate. For this purpose, thermal monitoring of office buildings using DEC systems was carried out for peak summer months (April to July 2016) in Jaipur city. Experimental results were utilized to calibrate the thermal simulation models, developed using EnergyPlus. Taguchi design was further applied to develop L16 Orthogonal array of control factors and their respective levels for performing simulation runs. Simulation run outputs were then used for predicting supply air temperature and indoor air temperature as a function of independent variables (control factors) using Multiple Linear Regression technique. Statistical significance of temperature correlations was established using Analysis of Variance. Field validation from two other buildings (of similar characteristics) found a reasonably good agreement (R2 > 0.90) between the onsite measurements and the computed values of indoor temperature. The same methodology was also repeated to suggest mathematical correlations for specific humidity prediction of supply air and then indoor air. Finally, the potential of DEC to offset thermal discomfort was assessed using the proposed mathematical correlations. This was accomplished by plotting the predicted indoor conditions on Composite Climate-specific Adaptive Thermal Comfort Zone (CCATCZ) developed by the authors particularly for office buildings of Indian composite climate. Comfort prediction with ASHRAE Standard 55–2013 thermal comfort zone and CCATCZ revealed that approximately 42% and 52% of the thermal discomfort hours could be evaded with the use of DEC during the summer season.