Experimental Investigation on Mist Flow and Heat Transfer in a Uniformly Heated Vertical Cylinder

Abstract

The steady, internal, and ultrasonic-generated water mist cooling in a uniformly heated vertical cylinder with evaporating subcooled water film has been investigated experimentally. The goal is to elucidate the effects of different operating parameters, viz. water mist concentration, carrier gas velocity, loaded heat flux, and flow orientation on the heat transfer rate and pressure drop characteristics. The experiments were performed in a turbulent flow regime over a range of Reynolds number (from 6000 to 18000) using air as the carrier fluid. Compared with the cylinder without water mist, the results showed that using water mist as a coolant increases the Nusselt numbers along the cylinder, high Nusselt numbers are obtained by suspending the high-water mist and it was about 224% for heat flux q=1.56 kW/m2. The results also showed that the local Nusselt number rapidly decreases as the heat flux increases, this decreasing in the Nusselt number was the most at high heat flux q=4.81 kW/m2, in which the water film early breakdown and the breakdown point gets closer to the entrance region. In addition, a new empirical correlation of the heat transfer rate was proposed to estimate the real benefits in using water mist of the enhanced cylinder.