An Experimental Study of Heat Transfer From Small Horizontal Cylinders at Near-Critical Pressures

An experimental study of the free convection heat transfer from horizontally held wires to carbon dioxide at near-critical pressures has been performed. In the experiments, platinum wires of 25.4 μm, 76.2 μm and 100 μm, as well as a 101.6 μm diameter nichrome 60/20 wire were used. The pressure (P) and bulk temperature (T_b) of the fluid were varied in the range: 6.34 MPa ≤ P ≤ 9.60 MPa and 10 °C ≤ T_b ≤ 33.3 °C, respectively. Visual observation of the flow was realized using a high speed camera. The bulk fluid temperature is introduced as a new reference temperature for the calculation of fluid properties. Correlations were developed to predict the natural convection heat transfer rate at both subcritical and supercritical pressures. The correlations developed predict almost all the experimental data from the current study and those reported in the literature to within ± 15%. No bubble-like flow pattern was observed for both platinum and nichrome wires.