An experimental investigation of unsteady thermal processes on a pre-cooled circular cylinder of porous material in the wind

This paper presents a simple and reliable method for determining the phenomenon of unsteady thermal transfer mainly for elements of porous materials. The method is demonstrated on a concrete circular cylinder subjected to air cross-flow at a constant temperature. Based on the technique of specific volume heat capacity of the system, thermal processes for various Reynolds numbers up to Re = 111,000 are monitored and measured using embedded thermal probes and multi-point surface thermometry. By identifying the fitting approximation functions over the measurement points, the time evolutions of the temperature distribution over the cross-section are estimated, which form the basis for determining the total heat energy transferred from the free-stream to the cylinder. The overall heat transfer coefficient is evaluated at various temporal stages of the testing. The paper also shows transient conductive processes in the cylinder arising due to the forced heat transfer at various flow velocities.