What are the limitations in controlling RH with central air-conditioning plants/window air conditioners?
In tropical areas like India, with normal central air conditioning plants, lowest relative humidity of 50%-60%, at best, are attainable economically, at room temperatures between 20°C to 24°C. This again is only possible with special design of the cooling coil and appropriate selection of the apparatus dew point and provision of sufficient reheat. With window air-conditioners or split A/c units, in the absence of specially designed cooling coils and reheat provision, typical relative humidity of 60-70% are commonly experienced at times of high outside moisture ambient conditions like monsoon. Removal of large water vapour/moisture through cooling requires after cooling to apparatus dew point close to freezing and substantial subsequent reheating, thus requiring both over sizing of the cooling equipment, as also increasing the operating cost with higher BHP per ton consumed, and reheat energy.
