Numerical and experimental study of a multiphase flow inside a self-contained drum motor drive system

Abstract

The multiphase Taylor-Couette flow of air and oil enclosed within the annular space between two concentric cylinders has been studied experimentally and numerically. The outer cylinder rotates at a constant speed and exchanges heat by convection and radiation with ambient air. The inner cylinder is stationary and subjected to a constant uniform heat flux. Such flow can be found in a self-contained drum motor drive system (SCDMDS). The heat flux imposed on the inner cylinder mimics the amount of heat generated due to several thermal losses within the SCDMDS. A layer of lagging material is sometimes added to the outer cylinder to enhance belt traction.The effect of the inner-to-outer cylinder radius ratio (RR), Reynolds number (Re), oil volume (OV), outer cylinder surface emissivity (ε), and lagging material thickness (δ) on the flow and heat transfer between the two cylinders and the ambient has been investigated considering a quasi-steady state analysis. The current investigation considered the following ranges found in a typical SCDMDS: RR = 0.35–0.85, Re = 200–3000, OV = 50–100 %, ε = 0–0.95, and δ = 0–100 mm. The numerical part of the present study has been carried out using ANSYS-CFX software package. The numerical results have been validated using experimental data. Resultsindicated that increasing RR, Re and ε enhanced the heat transfer within the SCDMDS. The rate of heat transfer within the annular space reached its highest value at OV = 65 % above which the rate of heat transfer is deteriorated. Because the lagging material is acting as an insulation over the outer cylinder, a critical thickness of δ = 35 mm resulted in the minimum overall resistance above which the rate of heat transfer is deteriorated.The parametric study revealed that the best overall thermal performance was attained at RR = 0.85, Reynolds number = 3000, OV = 65 %, ε = 0.95 and δ = 35 mm. In this case, the heat transfer coefficient between the inner cylinder and the oil reached its highest value of 410 W/m2 °C, giving the lowest possible inner cylinder temperature. A correlation of Nusselt number in terms of the geometrical and operating parameters of a SCDMDS considered in the current study has been developed and validated. The developed correlation gave a maximum deviation of ±8 %.