Abstract
An air conditioner is constructed with a fan and a heat exchanger around it. The heat exchanger tends to be close to the tips of the fan so as to miniaturize the product and allow a large capacity. However, it sometimes generates a noise like a weak whistling. The noise sources clearly seem to be from the part of the heat exchanger which is close to the fan tips. This noise is considered as a kind of a cavity tone and has been studied by many researchers over a long period. However the cavities between the heat exchanger fins are not enclosed and arranged continuously. It is considered that the difference in the static pressures between the inlet and outlet sides of the heat exchanger effects this noise. To reduce the noise of the air conditioner, it is important to clarify the relation between the noise and differential pressure between the inlet and outlet sides of the heat exchanger. To this end, a wind tunnel was used for a fundamental study of this phenomenon. The heat exchanger was let into the side of the wind tunnel wall with its main face parallel to the main flow.
