Measurements of instantaneous heat transfer in a two-dimensional T-junction using a multi-thermocouple probe

Abstract

A minimally intrusive multi-thermocouple probe for the measurement of instantaneous wall heat fluxes in a boundary layer was developed. It was based on a phenomenological model involving the temperature equation in the flow and a Taylor series development of the conductive heat flux at the wall. The flux-meter was applied to a non-isothermal T-junction operating at a low value of the momentum flux ratio, exhibiting Kelvin–Helmholtz rolls in the interface between the hot and cold fluid. The results demonstrated that instantaneous wall heat fluxes presented large fluctuations due to fluid flow events. In addition, a narrow region was found where film cooling occurs. Such results could not be obtained by using correlations based on a reference temperature or employing embedded measuring devices.

Measuring system with a dual needle probe for testing the parameters of heat-insulating materials

“…This methodology is based on the application of a heat pulse to a line source and the analysis of the temperature response at the line source or at some distance from the line source. The design theory, operation and error analyses of THW are well documented [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. This technique is simple, fast and requires relatively small samples.…”

“…Using a thermal probe offers an alternative transient method to laboratory-based thermal measurement techniques that has good prospects for measuring the thermal conductivity and, potentially, the thermal diffusivity of building materials on site [22][23][24]. This method is also used advantageously in the case of fluids due to the difficulties in eliminating the effects of natural convection on the heat flux [20,21]. Thermal probes are currently commercially available from companies like Decagon and Hukseflux.…”

Design and development of resistive temperature detector arrays on aluminium substrates. Measurements in mixing experiments

“…Optical methods are mostly used for time averaged measurements and it sometimes becomes difficult or even impossible to have a straight optical path to the areas under observation. Thermocouples are obviously intrusive from the fluid side [17]; therefore it is preferred to place them at back side of the wall [18]. Still, the positioning is often connected with some uncertainty due to the finite size of the thermocouples.…”