| 摘要 |
A water heater (10) including a tank (12) adapted for mounting with its longitudinal axis substantially vertical and a duct (32) adapted for mounting with its longitudinal axis substantially vertical. The duct (32) is positioned within the tank (12) and extends through at least most of the height of the tank (12). The duct (32) defines a first volume (34) within the duct interior and a second volume (36) between the duct exterior and the tank interior. The first volume (34) being smaller than the second volume (36). The duct (32) has at least one upper opening (38) at or near the top of the duct (32) and at least one lower opening (40) at or near the bottom of the duct (32). The heater (10) also has a heating element (44) within, or forming all or part of, the duct (32). The element (44) extends at least substantially through the upper half of the duct (32). The heater (10) also has an inlet (24) at or near the bottom of the tank (12) and an outlet (22) at or near the top of the tank (12). In use, energising the heater element (44) causes water to flow from the first volume (34) to the second volume (36) through the upper opening(s) (38) and water to flow the second volume (36) to the first volume (34) through the lower opening(s) (40).
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