High Efficiency Heat Exchanger for Drain-Water Heat Recovery

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The average Canadian uses 75 L of hot water per day, over half of which is used for bathing, laundry, and dishwashing. When the waste water produced flows into drains it carries a significant amount of thermal energy with it. One way of recovering some of this energy is to use a drain water heat recovery (DWHR) system, which is a heat exchanger that transfers heat from wastewater to incoming cold city water before it flows into the water heater. Current DWHR systems that are commercially available have a relatively low heat exchange effectiveness. They also have no method of detecting leaks, which could potentially lead to contamination of potable water. Drain water heat recovery systems need a leak detection system that will sound an alert if the wall between the two water streams is ruptured. The proposed project is a collaboration between the University of Toronto and Lancaster Homes, which is based in Richmond Hill and is one of Ontario's leading residential builders. We will design and build high-efficiency heat exchangers to recover and use the thermal energy from waste hot water, while also developing a safety system to detect when mixing of grey and fresh water lines. The chief objectives of the proposed project are: - Optimise the design of a high-efficiency shell-and-tube heat exchanger. - Design a novel falling-film heat exchanger for waste heat recovery - Build both heat exchangers and test them according to ANSI standards. - Develop an active leak detection system, to immediately alert the user once mixing of the grey and fresh water lines occurs.