Indoor air quality and energy saving in air-conditioning systems have been taken seriously. Suitable temperature and relative humidity of supply air are important aspects of good indoor air quality. Thermal Power Loop (TPL) heat exchanger is very effective device for transmitting heat at high rates over considerable distances with extremely small temperature drops, reversibility used in air-conditioning systems, not only for heat recovery, but also for thermal control. This paper presents the application of TPL heat recovery, but also for thermal control. This paper presents the application of TPL heat exchangers to heat recovery, temperature and humidity control in air conditioning systems . The study involves analytical modeling , thermal control and simulation of heat recovery system. TPL heat transfer principles and capillary limitation are analyzed . System model of heat recovery is established by analyzing the heat flow and using energy conservation principle. A typical single -zone air-conditioning system with heat flow and using energy conservation principle. A typical single-zone air-conditioning system with heat exchanger is simulated. The temperature and relative humidity control of supply air by thermal control of TPL heat exchanger is conceptual designed . It is observed that this type of heat exchanger used in heat recovery system has more advantages than the conventional reheat coils , and can result in energy saving and enhancing the cooling capability of cooling coils.