BOUNDARY-CONDITION INFLUENCES ON THE EFFECTIVE AREA OF A LOCAL HEAT-FLUX PROBE

Active heat flux probes are used to quantify the convection boundary c ondition in heat transfer environments. In previous studies, the probe response has been documented under ideal conditions, namely an isothe rmal sensor surface mounted in an isothermal body of equal temperature . In this paper, the influence of the thermal boundary conditions arou nd the perimeter of an active isothermal heat flux probe is examined d uring steady state operation while one surface of the sensor is expose d to an imposed convection boundary condition. A two-dimensional numer ical model is developed and used to simulate the behaviour of the loca l thermal field. The results show that the influence of the perimeter boundary conditions alters the static calibration of the probe. These effects decrease as convection heat transfer is increased and are pred ictable and linear. However, design geometry changes known to increase the sensitivity of the probe to the convection boundary conditions al so are found to increase the sensitivity to the perimeter boundary con ditions. This sets up a design trade-off. Under high-convection condit ions, such influences are negligible and the probe calibration remains essentially constant.