Abstract: 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 another embodiment, evaporative cooling is used to cool the exhaust air before passing through the heat exchanger.

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.

Abstract: The heat exchanger is made economically by using thermoplastic sheets with hollow tubes and spacers between the sheets and fusing the edges of the sheets together to form an integral housing. Preferably, the heat exchanger is an opposed-flow heat-exchanger giving improved heat-transfer efficiency.

Abstract: The ventilating system includes evaporative cooling of the exhaust air before it enters a heat exchanger to cool incoming fresh outside air. A suction fan pulls exhaust air through the heat exchanger and, in combination with a flow restrictor, reduces the pressure on the exhaust air and augments the evaporative cooling. The use of a pusher fan to force outside air through the heat exchanger ensures that any leakage in the heat-exchanger results in outside air entering exhaust air and minimizing the chances of contamination by leaking exhaust air into the incoming fresh air.

Abstract: The heat exchanger is made economically by using thermoplastic sheets with hollow tubes and spacers between the sheets and fusing the edges of the sheets together to form an integral housing. Preferably, the heat exchanger is an opposed-flow heat-exchanger giving improved heat-transfer efficiency.

Abstract: The ventilating system includes evaporative cooling of the exhaust air before it enters a heat exchanger to cool incoming fresh outside air. A suction fan pulls exhaust air through the heat exchanger and, in combination with a flow restrictor, reduces the pressure on the exhaust air and augments the evaporative cooling. The use of a pusher fan to force outside air through the heat exchanger ensures that any leakage in the heat-exchanger results in outside air entering exhaust air and minimizing the chances of contamination by leaking exhaust air into the incoming fresh air. The heat exchanger is made economically by heat-forming cavities in relatively thick thermo-plastic sheets, interleaving them with other thermo-plastic sheets having separate gas flow conduit structures, and securing the sheets together. Preferably, the heat-exchanger is an opposed-flow heat-exchanger giving improved heat-transfer efficiency.