Experimental investigation of the thermal fluctuations in hot and cold fluids mixing in a T-junction filled with spherical particles

The turbulent mixing of hot and cold fluids in a T-junction filled with a porous medium composed of stainless steel spherical particles has been experimentally investigated in order to determine the influence of the ratio of the flow in the main duct to that in the branch duct, and the temperature difference between the mixing fluids, on the thermal fluctuations. The temperature of the cold water in the branch duct was fixed at 22.5 °C, and the temperature differences between the cold water and the hot water in the main duct were 7.5 °C, 15 °C or 20 °C. The ratios of the flow in the main duct to that in the branch duct were 2, 4, or 8. The experimental results indicated that the largest fluctuations of instantaneous temperatures were in the middle and upper part of the mixing zone. On increasing the flow ratio, the region of strong temperature fluctuations became smaller. The distribution of hot and cold water in the mixing zone was found to depend on the flow ratio, which had a significant effect on the distribution of normalized mean and root mean square temperatures. The temperature difference had a limited effect on the temperature fluctuations.