The Effect of Dissolving Salts in Water Sprays Used for Quenching a Hot Surface: Part 2—Spray Cooling
Author:
Cui Qiang1, Chandra Sanjeev1, McCahan Susan1
Affiliation:
1. Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada
Abstract
The effect of adding one of three salts (NaCl, Na2SO4 or MgSO4) to water sprayed on a hot surface was studied experimentally. A copper test surface was heated to 240°C and quenched with a water spray. The variation of surface temperature during cooling was recorded, and the surface heat flux calculated from these measurements. Surface heat flux during cooling with pure water sprays was compared with that obtained using salt solutions. Dissolved NaCl or Na2SO4 increased nucleate boiling heat transfer, but had little effect on transition boiling during spray cooling. MgSO4 increased both nucleate and transition boiling heat flux. Enhanced nucleate boiling was attributed to foaming in the liquid film generated by the dissolved salts. MgSO4 produced the largest increase in nucleate boiling heat transfer, Na2SO4 somewhat less and NaCl the least. A concentration of 0.2 mol/l of MgSO4 produced the greatest heat flux enhancement; higher salt concentrations did not result in further improvements. During transition boiling particles of MgSO4 adhered to the heated surface, raising surface roughness and increasing heat transfer. Addition of MgSO4 reduced the time required to cool a hot surface from 240°C to 120°C by an order of magnitude.
Publisher
ASME International
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics,General Materials Science
Reference12 articles.
1. Qiao, Y. M., and Chandra, S., 1998, “Spray Cooling Enhancement by Addition of a Surfactant,” ASME J. Heat Transfer, 120, pp. 92–98. 2. Jia, W., and Qiu, H. H., 2001, “Experimental Investigation of Droplet Dynamics and Heat Transfer in Spray Cooling,” Proceedings of the 35th National Heat Transfer Conference, Paper NHTC2001-20109. 3. Cui, Q., Chandra, S., and McCahan, S., 2001, “The Effect of Dissolving Gases or Solids in Water Droplets Boiling on a Hot Surface,” ASME J. Heat Transfer, 123, pp. 719–728. 4. Cui, Q., Chandra, S., and McCahan, S., 2002, “The Effect of Dissolving Salts in Water Sprays Used for Quenching a Hot Surface. Part 1: Boiling of Single Droplets,” ASME J. Heat Transfer, submitted. 5. Cui, Q., 2001, “The Effect of Dissolving Salts or Gases in Water Sprayed on a Hot Surface,” Ph.D. thesis, University of Toronto, Toronto, ON, Canada.
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