INFLUENCE OF GRAVITATION ON HEAT TRANSFER BY NATURAL CONVECTION

The objective is to separate natural convection and radiation experimentally. Therefore a heat source is placed inside a closed cavity and the acceleration inside the cavity can be changed. A centrifuge is used to change the acceleration. A flat resistor etched on a printed circuit board of 25.5mm x 25.5mm, is placed in a hermetically sealed cylinder, which hangs under the arm of the centrifuge. The resistor is powered by batteries, dissipates 1.63W and has a surface temperature of 82°C at 1g. Natural convection is maintained inside the cylinder. Convection and radiation are the main modes of heat transfer, but there’s also an amount of conduction through the wires that connect the batteries with the resistor. The rotational speed of the centrifuge determines the centrifugal force in the cylinder. When the centrifugal force increases, the temperature of the resistor decreases due to the increase of natural convection. The amount of radiation, conduction and total heat transfer can be determined from the experiment, so the amount of natural convection can also be determined. The experimental results are compared with the governing equations to validate the experiment. The reproducibility of the experiment is also checked