| 摘要 |
A fluid-to-fluid heat exchanger for use where two fluid streams may be of indeterminate composition, temperature, and flow rate, and, where the two fluid streams may flow at different rates and at different times. Such conditions are found, for example, in the flow patterns of a building's hotwater, cold feed water for a water heater, and drainwater. As defined for heat recovery from drainwater, the present invention comprises a first, central, straight-through heat exchanger tube for cooling flowing drainwater, a second heat exchanger to heat cold water encircling and spaced from the first, and a non-pressurized reservoir between first and second heat exchangers permanently filled with water in thermal contact with first and second heat exchangers. Submerged in the reservoir water there is at least one insulated convection chamber, of small volume, enclosing first heat exchanger with a convection opening uppermost. Opening allows upward convection and therefore heat transfer when drainwater heats convection chamber water making it lighter. Convection and heat transfer ceases when drainwater cools convection chamber water making it heavier, blanketing drainwater heat exchanger in a small volume of cold water. This one-way heat transfer prevents heat loss from remaining reservoir water to cold drainwater. With convection chambers inverted to have convection opening bottommost, the device serves to make coldwater, for drinking, as cold as possible by transferring unwanted heat to colder drainwater. Used in series, heat recovery and fresh water cooling can both be accomplished. Units for horizontal and vertical installation are disclosed.
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