Importance

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Abstract

The ventilator system and method use a heat exchanger to selectively transfer heat between fresh outside air entering and exhaust air leaving an enclosed space whenever energy can be recovered from the exhaust air by doing so. The system uses a microprocessor-based controller which stores one or more profiles indicating the time-varying needs of the enclosed space for heating and cooling. The transfer of heat between the exhaust and fresh air is reduced or eliminated simply by reducing the speed of or stopping the exhaust air handler while the fresh air handler continues to run. Evaporative cooling for the exhaust air can be provided, and an all-plastic plate type heat exchanger preferably is used, together with an air handler at the exhaust outlet of the heat exchanger to pull exhaust air through the heat exchanger. If cold water is used in evaporative cooling, another heat exchanger can be used to heat the water by extracting heat from the fresh air. Rotary heat wheels and other types of heat exchangers also can be used. Desiccants or refrigeration can be used for dehumidification, in combination with heat exchangers for energy recovery. Plural heat exchangers can be connected to carry fresh air in series and exhaust air in parallel to increase energy recovery. In one embodiment, the fan of a central air conditioning system is used as the air handler for the heat exchanger by connecting the exhaust conduit of the heat exchanger to the positive pressure side of the fan and extracting a minor fraction of the air for use as exhaust air, and similarly adding fresh air to the negative pressure side of the fan to form a minor fraction of the return air to the central system. In one embodiment, evaporative cooling is used to cool the exhaust air before passing through the heat exchanger. A variable-reheat refrigeration type dehumidification system cools the fresh air by contacting the evaporator coils, and the hot refrigerant gas flows either through a first condenser positioned to reheat the fresh air, or a second condenser cooled by the exhaust air from the enclosed space.

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First Claim