Mist-cooling systems ineffective in hot, humid weather
The suggestion in “Mist-cooling systems may spur public transport use” (July 6) will not be effective exactly because of our weather.
When air is hot and humid, it is laden with gaseous water. Adding moisture will make it more humid and more unbearable.
Mist-cooling is effective if the weather is hot and arid, that is, low relative humidity. Then moisture will turn from the liquid phase to gaseous phase and, in the process, absorb from the surroundings the latent heat required for the conversion.
If the air is humid, it has less capacity to absorb more water. When relative humidity rises to 100 per cent, water will begin to condense. Hence, mist-cooling systems are ineffective when it is hot and humid.
Furthermore, water, a precious resource, is required. Water supply, storage and treatment add to the complexity of such a system and its maintenance. It may be better and simpler to install solar panels to power fans with the electricity generated.
