Takehiko Yanagida

Heat transfer characteristics of fluid flow in an annulus with an inner rotating cylinder having a labyrinth structure

The convective heat transfer coefficient was experimentally investigated in an annulus with an inner rotating cylinder to estimate the thermal fatigue of the inner and outer cylinders on the rotating machine. The following three conclusions were obtained: (1) Within the range of the experimental conditions, the heat transfer coefficient did not depend on the axial flow rate; rather, it showed a larger dependence on the inner cylinder rotating speed. (2) The heat transfer coefficient at the top of the labyrinth was about three times as large as that at the bottom. (3) An empirical correlation equation considering the gap between the inner and outer cylinders is proposed, which predicts the heat transfer coefficient on the rotating machine within ±30 percent.

HEAT TRANSFER CHARACTERISTICS OF FLUID FLOW IN AN ANNULUS WITH AN INNER ROTATING CYLINDER HAVING A LABYRINTH STRUCTURE

The heat transfer coefficient of fluid flow was experimentally investigated in an annulus with an inner rotating cylinder to estimate thermal fatigue of the inner and outer cylinders on the rotating machine. Following three points were found in the study. (1) Within the range of the experimental conditions, the heat transfer coefficient did not depend on the axial flow rate, rather it had a large dependence on the inner cylinder rotating speed. (2) The heat transfer coefficient at the top of the labyrinth was about three times as larger as that at the bottom. (3) An empirical correlation equation considering the gap between the inner and outer cylinders was proposed, which predicted the heat transfer coefficient on the rotating machine within ±30%.

Thermal analysis by the finite-element method considering the temperature change of a fluid along a path.

As a convective boundary condition in thermal analysis by a finite-element method, heat transfer coefficients and circumferential fluid temperatures are generally specified. However, when fluid temperature varies greatly along a flow path, it is difficult to specify fluid temperature distribution in advance. In the case of a combined analysis of flow and heat transfer, a large-scale computer is needed. Furthermore, it takes much time to solve the flow equation. In designing machines, a simple method for predicting cooling performance is often more desirable than precise flow analysis. This paper shows a simple thermal analysis method considering the temperature change of a fluid along a path without flow analysis by specifying heat transfer coefficients. An example of the thermal analysis of a general-purpose inverter is shown.