Method of and apparatus for recovery of waste energy

An apparatus for energy recovery for a dishwasher using heated water from a hot water heater, said dishwasher having separate rinse and wash cycles with said rinse cycle receiving heated water from said hot water heater and said wash cycle producing waste water, comprising:

• a holding tank for collecting and releasing said waste water, said holding tank having a capacity generally equal to the amount of waste water received from said wash cycle;
• means for transferring waste water from said holding tank to a heat exchanger to preheat incoming water for use in said dishwasher;
• means including pump means for transferring said preheated water directly to said hot water heater for heating said preheated water to a temperature sufficient for use in said dishwasher;
• means for controlling the transfer of waste water to said heat exchanger at a time corresponding to the flow of heated water from said hot water heater to said dishwasher, said control means being responsive to the level of waste water in said holding tank reaching a predetermined level for starting said pump and a predetermined lower level for stopping said pump when said waste water has been drawn down to said lower level;
• and
• means for transferring waste water from said heat exchanger to an outlet.

Apparatus for energy recovery for a device using heated liquid from a liquid heater intermittently and producing waste liquid at a lower temperature than said heated liquid, including a holding tank for collecting and releasing said waste liquid, means for controlling the release of said waste liquid to effect release thereof during a selected period, a pump transferring said waste liquid to a countercurrent heat exchanger from said holding tank, means for passing cool feed liquid to said heater through said heat exchanger in countercurrent heat exchange relationship with said waste liquid and then to said liquid heater and means for discharging said waste liquid from said heat exchanger after said heat exchange, comprising:

• housing means enclosing said heat exchanger and said holding tank, with said holding tank and a laterally adjacent elongated outlet area below said heat exchanger, said outlet area having an outlet for discharge of waste liquid;
• inlet means for said pump extending to a lower portion of said holding tank;
• elongated upright baffle means separating said holding tank from said outlet area, whereby said holding tank may overflow into said outlet area;
• said heat exchanger having upright spiral coils for waste liquid and feed liquid in adjacent relationship;
• first conduit means connecting said pump with the upper ends of said waste liquid coils;
• second conduit means for transferring waste liquid from the lower end of said waste liquid coils to said outlet area;
• third conduit means for supplying the lower ends of said feed liquid coils with cool feed liquid;
• fourth conduit means for transferring preheated feed liquid from the upper ends of said feed liquid coils to said heater;
• and
• means for controlling the operation of said pump to start said pump at a time corresponding generally to the flow of heated liquid from said heater to said device.