| 摘要 |
PURPOSE:To extend an operating time when frost is adhered by a method wherein a group of thermal conducting pipes is made independent for each of rows with respect to an air flow direction, a pipe pitch in each of rows is decreased in sequence from an air inlet side to an air outlet side, and a diameter of thermal conducting pipe in each of the rows is gradually increased from the air inlet side to the air outlet side. CONSTITUTION:A heat exchanger is comprised of a group of thermal conducting pipes 7a, 7b, 7c and 7d arranged in a grid pattern in parallel with an air flow direction 6 and a group of fins 8, and a pipe diameter of each of the group of thermal conducting pipes 7a, 7b, 7c and 7d is Da, Db, Dc and Dd, resulting in that the pipe diameters Da, Db, Dc and Dd are set at a relation of Da<Db<Dc<Dd and a pitch of each of the pipe pitches in the row S1, S2 and S3 is set to have a relation of S1<S2<S3. Therefore, fin temperatures t10, t11, t12 are set to have a relation of t10<t11<t12. Due to this fact, an absolute humidity difference between flowing air influencing a frost forming shape and a saturated wet air corresponding to a thermal conducting temperature of the heat exchanger is made uniform over an air flowing direction to form a uniform frost layer 13. Therefore, a thicker frost layer is not locally present at the air inlet thermal conducting surface, resulting in that the long air passage is assured and then an operating time can be remarkably extended.
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