| 摘要 |
PROBLEM TO BE SOLVED: To detect frost-formation exactly in a heat exchanger. SOLUTION: Heat exchanging quantity Q of an outdoor heat-exchanger (22) is calculated from characteristics of compressors (41, 42). Outside temperature Ta and refrigerant evaporation temperature Te are detected, and valueκA=Q/(Ta-Te) is calculated by multiplying an overall heat-transfer coefficientκof the outdoor heat exchanger (22) by the heat transfer area A. When theκA becomes at most 80% of the initial valueκ0A (value ofκA at unfrosted time), a defrosting operation is started.
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