Evaporative cooling; Exposed roof; Summer of Delhi
In this study, diurnal hourly values of temperature and humidity in a room, with its roof exposed to the solar radiation in the summer months of April, May and June in Delhi, and having a direct evaporative cooler, have been computed and compared with the values obtained if the roof is unexposed. It is seen that additional heat load due to exposure of the roof to the solar radiation can be taken care of by slightly increasing the flow rate of the evaporatively cooled supply air. For April and May, the resulting conditions of the room air can be brought within an extended comfort zone (ECZ) by selecting an appropriate air change rate (ACH) giving due consideration to the bypass factor (BPF) of the cooler. During the month of June, the ambient air is very hot and its humidity rises; the conditions of the room are not within the ECZ, although the discomfort is mitigated. The levels of thermal sensation, which may be obtained with a direct evaporative cooler, have been computed on a numerical scale (S) which is pertinent to hot-dry and warm-humid climatic zones in India.