Experimental investigation on convective heat transfer of inclined jets impinging on the rotating cylindrical surface in the confined space

Abstract

This paper presents an experimental study on the convective heat transfer characteristics of a circumferentially arranged oblique jet array impinging on the rotating cylindrical surface in the confined space. This cooling structure can be used for the cooling of rotating equipment, such as the cooling of rotating shafts of steam turbines, the quenching of metal materials, and the cooling of cement rotary kilns. The heat transfer coefficient on the rotating cylindrical surface is obtained with the transient thermochromic liquid crystal (TLC) method. Local and circumferential average heat transfer characteristics, overall heat transfer uniformity, and heat transfer capacity are analyzed comprehensively. The effects of rotational Reynolds number (Rer), jet Reynolds number (Rej), and jet angle (θ) on the heat transfer behaviors are investigated where the rotational Reynolds number is varied from 105,115 to 420,460 and the jet Reynolds number is varied from 20,000 to 35,000 at three different jet angles (θ=20∘,30∘,45∘). The experimental results show that with the increase of the rotational Reynolds number, the overall circumferential average Nusselt number presents a trend of first decreasing and then increasing, mainly depending on the relative velocity of the circumferential velocity of the main flow and the tangential velocity of the rotating cylindrical surface. The average Nusselt number of the cylindrical surface decreases first and then increases gradually with the increase of the rotational Reynolds number and jet Reynolds number. As the jet angle increases from 20∘ to 45∘, the average Nusselt number increases gradually.