Coolant flow distribution and pressure loss in ONAN transformer windings. Part II: Optimization of design parameters

For pt.1, see ibid., vol.19, no.1, p.186-93, January 2004. The effects of total mass flow rate, flow arrangement, and geometrical parameters in ONAN transformer windings are investigated. It is found that the conventional minor losses are predominant in determining the mass flow distribution and pressure losses for the present flows. The sizes of the cooling ducts and the number of disks per pass have strong influence on both the mass flow distribution and the pressure loss. Flow arrangement in the horizontal ducts can have significant influence on the flow distribution, hence on the hot spot formation. Since the rate of heat generation increases in the vertical direction, a corresponding increase in the cooling oil flow rate vertically will optimize winding performance.