Experimental and numerical studies on the noise emissions from heat pumps, with respect to the heat exchanger - Fan interaction

Aeroacoustic noise from fans contributes significantly to the overall noise emissions from heat pumps. The noise emitted from the fan is affected by the characteristics of the flow on the suction side, which may vary depending on the type of heat exchanger and the distance between the heat exchanger and the fan. To investigate these effects, experimental studies have been conducted using a model of a heat pump outdoor unit with an adjustable casing. Acoustic measurements were performed with two different heat exchangers: one with classical round tubes and fins and another with microchannels. It was found that the round tube heat exchanger produces larger tonal components in the sound power spectra than the microchannel heat exchanger. The results also show that the levels of the tonal components become larger as the distance between the heat exchanger and the fan increases. The scenarios were also modelled numerically in OpenFOAM®. Experimental and numerical results ex hibit similar tendencies with respect to the flow characteristics. Reproducing the spectral characteristics of the noise emissions for different heat exchanger types and relative heat exchanger - fan placements in numerical simulations remains a challenge and is subject of ongoing research.