MODELING OF STEADY-STATE HEAT TRANSFER IN A WATER SPRAY IMPINGEMENT ONTO A HEATED WALL

摘要

The application of the work presented in this paper is that of the cooling by water spray impingement of hot surfaces as used,for example,in steel manufacture.A new spray impingement heat transfer model has been developed on the basis of the engineering superposition principle.The heat transfer and drop hydrodynamic phenomena occurring during spray cooling are intimately related but uncoupled in the model.To make these phenomena independent,impaction-behavior data were extracted from experimental data based on steady-state conditions in the literature [S.Chandra and C.T.Avedisian,Proc.R.Soc.London,Ser.A,vol.432,pp.13-41,1991;J.D.Bernardin,C.J.Stebbins,and I.Mudawar,Int.J.Heat Mass Transfer,vol.40,no.2,pp.247-267,1997],and transient heat transfer data were obtained by means of an in-house computational code.The model is used here to predict the heat flux from a constant-temperature hot surface to the spray for the three heat transfer boiling regimes under the following droplet impingement Weber number and wall temperature ranges:0 < We < 1000 and 373 K < TW < 573 K,under normal pressure conditions.The model performance is tested against one major set of steady-state experimental heat transfer data taken from the literature [R.A.Sharief,G.G.Nasr,A.J.Yule,J.R.Jeong,and D.D.James,Proc.of 1CLASS-2000,Pasadena,CA (on CD-ROM),2000] to assess the accuracy of the computer model.The data were obtained from four full-cone water atomizers,which were used to experimentally extract heat from a heated test piece.The spray experiment used different impaction distances,injection pressures,and wall temperatures.The heat transfer model predictions are compared to 18 different experimental conditions and reasonable agreement is obtained in many cases.The discrepancies in the other cases are partly attributed to assumptions made in the spray model.Deficiencies in the heat transfer model are identified in the conclusions.