Method of and unit for recovery of waste energy

An energy recovery unit for a dishwasher and the like, comprising:

• a heat exchanger having coils surrounding a central space, said coils including first and second tubes respectively adapted to carry warm waste water from said dishwasher and the like and cooler feed water for a hot water heater;
• said heat exchanger having a waste water inlet and outlet for said tubes adapted to carry warm waste water, a feed water inlet for said tubes adapted to carry cooler feed water and a feed water outlet for feed water heated or warmed by heat exchange with said warm waste water;
• means for supplying said waste water from said dishwasher and the like to said waste water inlet of said heat exchanger;
• a hot water heater including a tank containing water to be heated disposed in said central space and provided with inlet means connected to the feed water outlet of said heat exchanger and outlet means adapted to supply heated water to said dishwasher and the like;
• at least one generally upright electric immersion heater in said tank;
• and
• closed conduit means independent of the supply of heated water to said dishwasher for recirculating a portion of the water from the outlet to the inlet of said hot water heater while said heaters are heating.

An energy recovery unit for a dishwasher and the like, comprising:

• a heat exchanger having coils surrounding a central space, said coils including first and second tubes respectively adapted to carry warm waste water from said dishwasher and the like and cooler feed water for a hot water heater;
• said heat exchanger having a waste water inlet and outlet for said tubes adapted to carry warm waste water, a feed water inlet for said tubes adapted to carry cooler feed water and a feed water outlet for feed water heated or warmed by heat exchange with said warm waste water;
• a hot water heater disposed in said central space and provided with inlet means connected to the feed water outlet of said heat exchanger and outlet means adapted to supply heated water to said dishwasher and the like;
• means for supplying said waste water from said dishwasher and the like to said waste water inlet of said heat exchanger;
• a relief valve connected to the upper portion of said heater to relieve excessive pressure produced by heat;
• said unit including a tank beneath said heat exchanger for receiving waste dishwater;
• and
• a pipe extending from said relief valve to said tank.

A method of recovering waste energy from a dishwasher having wash and rinse cycles and the like, comprising:

• transferring waste wash water from said dishwasher to a collection tank disposed in a lower position;
• transferring such waste water from said collection tank to a heat exchanger surrounding a hollow central space and having coils formed by juxtaposed sets of tubing which carry such waste water in one set of tubing and cold feed water for a hot water heater in another set of tubing;
• passing said waste water and feed water in countercurrent relationship through said heat exchanger;
• passing said preheated feed water to a hot water heater including a tank located in the central space of said heat exchanger;
• heating the water in said hot water heater;
• and
• supplying hot water from said hot water heater to said dishwasher at selected times.

A method of recovering waste energy from a dishwasher having wash and rinse cycles and the like, comprising:

• transferring waste wash water from said dishwasher to a collection tank disposed in a lower position;
• transferring such waste water from said collection tank to a heat exchanger surrounding a hollow central space and having coils formed by juxtaposed sets of tubing which carry such waste water in one set of tubing and cold feed water for a hot water heater in another set of tubing;
• passing said waste water and feed water in countercurrent relationship through said heat exchanger;
• passing said preheated feed water to a hot water heater located in the central space of said heat exchanger;
• heating the water in said hot water heater;
• removing fluid at excess temperature and/or pressure from said hot water heater;
• transferring said removed fluid to said waste water collection tank;
• and
• supplying hot water from said hot water heater to said dishwasher at selected times.