Heat exchanger water heating system for commercial dishwasher

摘要

A multi-chamber conveyor type dishwasher uses a heat recovery unit (HRU) to heat water for a final rinse chamber during a preheat and/or dishwashing phase. The HRU heats water supplied by a low temperature water source using the dishwasher's hot vapor exhaust. An input supply of water for a downstream booster heater is varied based on a sensed temperature of the HRU's output water. If the temperature is acceptable, the HRU supplies input water to the booster heater for the rinse chamber. When the temperature drops below a threshold, the controller temporarily bypasses the HRU and supplies water to the booster heater from a high temperature water source. The HRU may be primed during a preheat phase using water from the high temperature water source. An amount of fan force used to pull the hot exhaust vapors through the HRU may vary based on the status of the dishwasher.

主权项

1. A method of heating water for a dishwasher, the method comprising:
supplying water from a low temperature external water source to a heat recovery unit having a heat exchanger; priming the heat recovery unit during a preheat phase by activating a first number of fans to pull hot vapors exhausted by the dishwasher across the heat exchanger; heating the water flowing through the heat recovery unit using heat recovered from hot vapors exhausted by the dishwasher routed into the heat recovery unit; selecting an input water supply for a booster heater downstream from the heat recovery unit based on a sensed temperature of the water at the output of the heat recovery unit;
wherein the heat recovery unit supplies the input water to the booster heater in response to the sensed temperature meeting or exceeding a threshold; andwherein a high temperature external water source that meets or exceeds the threshold bypasses the heat recovery unit and supplies the input water to the booster heater in response to the sensed temperature being less than the threshold; wherein heating the water flowing through the heat recovery unit comprises activating a second number of fans greater than the first number of fans upon completion of the preheat phase to pull the hot vapors exhausted by the dishwasher across the heat exchanger while flowing the water supplied by the low temperature external water source through the heat exchanger.