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International Heat Transfer Conference 7

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

COOLANT DISTRIBUTION IN DISC TYPE TRANSFORMER WINDING HORIZONTAL DUCTS AMD ITS INFLUENCE ON COIL TEMPERATURES

O. Szpiro
Imperial College, London S.W.7. England

P. H. G. Allen
School of Engineering Systems and Design, South Bank University, London, SE1 OAA, UK; The City University, London, EC1V OHB, England

C. W. Richards
Thames Polytechnic, London SE18 6PF, England

Abstract

Power transformer size, rating and insulation life expectancy are all influenced by winding heat transfer. The fluid flow distribution and winding copper "hottest spot" are closely related. In a disc winding, the flow is in horizontal ducts where buoyancy forces have imperceptible equalising effect.
Flow distributions have been measured and predicted by a Navier equation algorithm for a perspex model representing winding sections of five and eight ducts. It was concluded that the hottest spot would be in the coils above and below the centre duct, contrary to the "Norris" thesis which implies that the uppermost coil is the hottest one.
Changes in the geometry of the inlet and outlet manifolds were investigated with the aim of equalising the flow distribution and reducing the hottest spot temperature. Equalisation will greatly simplify thermal calculations and could increase power to weight ratio or lengthen life.

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