Modelling of the mass flow distribution around an array of rectangular blocks in-line arranged and simulating the cross-section of a winding disc-type transformer

Experimental and numerical studies have both depicted the distribution of mass flow around an array of rectangular blocks due to buoyancy driven flows. The geometric configuration (array of rectangular blocks in-line arranged) simulates the cross-section of a disc-type transformer. It is a two-dimensional model. Transversal flows through horizontal channels (space between blocks) have been observed on an experimental set-up. Laser Doppler velocimeter is used to measure the velocity held. Numerical simulations of the flow in the same configuration have proved the influence of buoyancy forces, the pitch ratio and the asymmetric heating on the distribution of mass flow rate around the blocks. To have a better insight of this phenomenon, a physical model characterised by half heated blocks in-line arranged with alternating asymmetry of heat dissipation per block in the stream wise direction is used. It is meant to point out the conjugate effect of asymmetric heating and block spacing on the mass flow distribution around the blocks. The model establishes conditions to allow transversal flow and a correlation between the Rayleigh number and the maximum mass flow rate through horizontal channel. It is also possible to modify deliberately the heat dissipation rate asymmetry to get all the fluid streams through horizontal channels and this without any block-washers to direct the flow. A configuration is proposed to apply to power transformers. In short this study brings a major solution - cheap and non-intrusive (without physical bodies)- to the cooling of horizontal channels in a configuration featuring rectangular blocks in-line arranged. (C) 2001 Elsevier Science Ltd. All rights reserved.