Thermal field measurements of heat sinks through a novel three-dimensional method based on acoustic waves

Natural convection heat sinks are still important in many industrial applications thanks to their simple design, effectiveness and noise-free operation. In this paper we present some case studies of experimental determination of the thermal characteristics of such devices, carried out using an innovative three-dimensional method of position detection for the temperature transducer (thermocouple). The three-dimensional position detection system uses acoustic waves emitted by a small grid of four loudspeakers, which simultaneously emit pseudo-random noise sequences orthogonal to one another. A small microphone samples the sounds coming from the four loudspeakers and its position in the three-dimensional space is obtained through trilateration calculations and signal analysis. Microphone and thermocouple are mounted on the same movable support, so that by measuring the position of the microphone, the position of the thermocouple is also detected. In this way it is possible to measure the temperature in a cloud of points of known position in space and obtain the three-dimensional thermal field around the heat sink. From these measurements it is possible to evaluate the thermal field around the heat sink and to easily compare different construction geometries. The position detection system has good precision and is inexpensive, allowing this type of measurement to be carried out even in low-budget situations. It also differs from thermal imaging systems such as IR cameras, in that it allows measurement of the temperature in the fluid surrounding the heat sink and not on its surface only.