| 摘要 |
PURPOSE:To prevent freezing of water in a hot water pipe during cooling and to reduce the size of a heat exchanger, by a method wherein a heating pipe is disposed on the upstream side of an air supply passage and a cooling pipe on the downstream side thereof. CONSTITUTION:During heating, hot water heated to approximate 80 deg.C is fed to a heating pipe 6 to perform heating. Cooling is effected at a freezing cycle using no coolant, the temperature of a coolant in a cooling pipe 7 is approximately 0 deg.C in a standard condition, and on the assumption that an indoor temperature is 20-25 deg.C, a heat transfer area ratio between cooling and heating is approximately 2-3 times. During cooling operation, when an indoor temperature is lowered, the temperature of a coolant in a cooling pipe is reduced to approximately -10--5 deg.C. Thereby, motion is effected such that water in a heating pipe 6 is cooled through the medium of a fin 5 through heat transfer of the fin. However, since a heating pipe 6 is disposed on the upstream side of an air supply passage, and since water is heated through heat transfer by means of high temperature indoor air fed to a heat exchanger 1 with the air of a blower 2, water in the heating pipe 6 is insusceptible to freezing, and water in the heating pipe is prevented from freezing under a low temperature working condition, e.g. a room temperature of 15 deg.C.
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