| 摘要 |
PURPOSE:To raise the heat exchange ratio and decrease noises on a heat transfer surface, by placing a heat exchanger symmetrically as to an intake and an exhaust passages so that the product of the acoustic impedances of the upstream parts of the intake and the exhaust passages at the heat exchanger is almost equal to that of acoustic impedances of the downstream parts of the intake and the exhaust passages. CONSTITUTION:An outside intake port 16 and an outside exhaust port are opened through an outside wall 15. An inside exhaust port 19 and an inside intake port 20 are opened through an inside wall 18. The heat exchanger 21 is provided near the central part of the inside wall 18 symmetrically as to the intake passage 27 and the exhaust passage 28, which are symmetrically formed. As a result, the acoustic impedances Z1, Z3, Z4, Z2 of the upstream and downstream parts 27a, 28a, 27b, 28b of the intake and the exhaust passages 27, 28 at the heat exchanger are related to one another as Z1.Z4 Z3.Z2. The invasion of noises through the heat exchanger is thus almost eliminated. |
