| 摘要 |
PURPOSE:To make it possible to set the temperature of a tube to be heated to a value above a predetermined value for positively preventing a drain from generating by controlling the flow rate ratio between a circuit to be heated and a bypass circuit for keeping the tube to be heated at a temperature enough for preventing the generation of the drain by means of a flow quantity adjusting valve in accordance with an output from detection means. CONSTITUTION:A fluid supplied from the upstream side of a heat exchanger flows on the downstream side through a bypass circuit 2 and a circuit 1 to be heated. The fluid 1 flowing through the circuit 1 to be heated is heat-exchanged in a heat exchanger, and a heating fluid and a fluid to be heated are mixed with each other at the downstream side of a joined point to prepare a fluid having a desired temperature. When, by the interlinking operation of a flow quantity ratio adjusting valve 3 and detection means 4, the side of a tube 11 to be heated is shifted to the low temperature side, the flow rate on the side of the tube to be heated is turned down, and the flow rate on the side of the bypass circuit 2 increases. Thus, the temperature on the side of the tube 11 to be heated rises up and is maintained in such a degree that no drain is produced. Further, conversely when the temperature of the circuit 1 to be heated is shifted to the high temperature side, it acts reversely to hold the temperature on the side of the circuit 1 at a predetermined value.
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