Drain back water heater

摘要

A drain back water heater includes a hot water storage tank (100) with an internal heat exchanger (102). The heat exchanger (102) is in the form of a cylinder closed at the top by a cap .(104) and also closed at the base. A pump (110) draws off water from the bottom of the heat exchanger (102) circulates the heat transfer fluid back to the top of the heat exchanger at (112) when required. Attached to, or incorporated in the cap 104 is a falling film distributor (118) which serves to distribute the heat transfer fluid in a thin film around the inner wall of the heat exchanger (102). The heat transfer fluid can be heated in solar water heating panels. When the pump is turned off, the heat transfer fluid drains into the heat exchanger to at least partially fill the heat exchanger.