| 摘要 |
PURPOSE: To improve the radiating performance of the low flow rate area of a warm water in a heat exchanger for space heating for an automotive air conditioner. CONSTITUTION: The height Hf of the corrugated fin 2b of a heating heat exchanger 2 is set to 3 to 6mm, the inner thickness of a flat tube 2a is set to 0.6 to 1.2mm, and the ratio (St/W×D) of the sectional area (W×D) represented by the product of the width W to the thickness D of a core 2c to the channel total sectional area St of the tube 2a is set to the range of 0.07 to 0.24 in response to the height Hf of the fin 2b and the inside thickness of the tube 2a. Thus, the Raynolds number of the channel is reduced, a laminar flow area is always formed despite the change of warm water flow rate, the changer of a water side heat transfer ratio is reduced, a water side heat transfer ratio itself is increased, and hence the radiating performance of the low flow rate area is improved.
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