An air conditioning system for conditioning the space within an enclosure having at least one inlet and one outlet, the system comprising first and second liquid/air heat exchangers; the first heat exchanger having an opening for receiving fresh air from the environment and for propelling the fresh air through the first heat exchanger to exchange heat with the liquid before it is entered into the enclosure, and the second heat exchanger having an opening for receiving air from the enclosure and for propelling it through the second heat exchanger to exchange heat with the liquid before it is expelled into the atmosphere. There are also provided methods for air-conditioning an enclosed space and for evaporation of industrial wastes.