Zhuqiang Yang

Convective heat transfer characteristics of supercritical hydrocarbon fuel in small non-circular cross-section channels

Convective heat transfer characteristics of supercritical pressure hydrocarbon fuel were experimentally investigated in electrically heated small non-circular channels with hydraulic diameter ranging from 2.00 to 3.00 mm. In this research, the system pressure and fuel mass velocity were maintained at supercritical (3.0 MPa) and 840.0 kg/(m 2 ∙s), while fuel inlet temperature varied from 200.0 ~ 450.0 °C. Heat transfer characteristics of various cross-section channels were obtained in view of the temperature profiles on the channel outside surface. Experimental results were compared among different non-circular channels. The effects of inlet fuel temperature, heat flux, aspect ratio or length to diameter ratio on the convective heat transfer characteristics were discussed. Due to the varieties of length to diameter ratio, the unique heat transfer characteristics of non-circular cross-section channels seemed to make them suitable for the application of hypersonic vehicle. However, this study did not consider the pyrolytic reaction in the high temperature range. The coking characteristics of small non-circular channels under high temperature may trade off the benefits acquired in the heat transfer characteristics.

Visualization and flow boiling heat transfer of hydrocarbons in a horizontal tube

Visualizations of a specific hydrocarbon fuel in a horizontal tube with 2.0 mm inside diameter were investigated. The experiments were conducted at mass velocity of 213.4, 426.5 and 640.2 kg/ (m2⋅s), diabatic lengths of 140, 240 and 420 mm under the pressure from 2.0-2.7 MPa. In the sub-pressure conditions, bubbly, intermittent, stratified-wave, churn and annular flow patterns were observed. The frictional pressure drops were also measured to distinguish the patterns. The development of flow patterns and frictional pressure drop were positively related to the mass velocity and the heat flux. However, the diabatic length of the tube takes an important part in the process. The residence time of the fluid does not only affect the transition of the patterns but influence the composition of the fuel manifested by the fuel color and carbon deposit. The special observational phenomenon was obtained for the supercritical pressure fluid. The flow in the tube became fuzzier and pressure drop changed sharply near th...