Spray transfer efficiency (TE) is defined as the mass fraction of sprayed paint which is deposited on the intended target, the remainder of the sprayed paint becomes undesirable overspray. The relationship between TE and gun supply pressure (or paint mass flow rate), gun-to-target distance, gun traverse speed, the angle of the spray gun relative to the target (gun-to-target angle), plus spray cone angle is reported herein for a typical fan spray system. Experimental results indicate that spray momentum rate (SMR) and droplet size dictate the TE for the various combinations of parameters considered here. The key finding is that TE correlates with SMR and spray mean drop size (Sauter mean diameter, or D32) via an expression of the form TE=a+b SMR − c (SMR)2+d D32, where a, b, c, and d are coefficients, determined by fitting the experimental data, and SMR is estimated via SMR=m2/ρA, where the paint mass flow rate m, the paint density is ρ, and the gun exit orifice effective tip cross sectional area is A. This expression accounts for physical phenomena that govern sprayed droplet deposition characteristics, such as entrainment, bounce-back, and drop size.
Experimental results also show that, for the range of parameters studied, gun traverse speed has no effect on TE, but increasing the angle of the spray gun relative to the target (gun-to-target angle), increasing the spray cone angle, or increasing the gun-to-target distance will decrease TE.
KeywordsApplication methods latex pollution spray application transfer efficiency
Unable to display preview. Download preview PDF.
- (1).Walberg, A.C., “Boost Overall Transfer Efficiency,” Industrial Finishing, 66, No. 5, 20–30 (1990).Google Scholar
- (2).Snowden-Swan, L. and Worner, P., “Determining Transfer Efficiency and VOC Emissions,” Metal Finishing, 91, No. 6, 73–78 (1993).Google Scholar
- (3).Ehrenhofer, K.R., “Selecting Automatic Spray Guns,” Industrial Finishing, 63, No. 11, 31–35 (1987).Google Scholar
- (4).Lamancusa, J.P., “Pollution Prevention Steps for Plastic Coaters—A Simplified Approach. Part II,” Plating & Surface Finishing, 81, No. 3, 25–32 (1994).Google Scholar
- (5).Hicks, P.G., Senser, D.W., Kwok, K.C., and Liu, B.Y.H., “Drop Transfer Efficiency in Air Paint Sprays,” presented at the Engineering Society of Detroit Advanced Coatings Technology Conference, November 9–11, Dearborn, MI (1993).Google Scholar
- (6).Muir, G.L., “Improving Liquid Spray Transfer Efficiency,” Product Finishing, 59, No. 6, 62–66 (1995).Google Scholar
- (7).Ewert, S.A., Felstein, S.R., and Martinez, T., “Low-Cost-Transfer-Efficient Paint Spray Equipment,” Metal Finishing, 91, No. 8, 59–64 (1993).Google Scholar
- (8).Hicks, P.G., and Senser, D.W., “Simulation of Paint Transfer in an Air Spray Process,” J. Fluids Eng.—Transactions of the ASME, 117, No. 4, 713–719 (1995).Google Scholar
- (9).Bunnell, M., “The Case for Turbine Sprays,” Product Finishing, Vol. 53, No. 2, pp. 72–74 (1988).Google Scholar
- (10).Zhou, Y., Lee, S.W., McDonell, V.G., Samuelsen, G.S., Kozarek, R.L., and Lavernia, E.J., “Characterization of Linear Spray Atomization and Deposition for Continuous Production of Aluminum Alloys,” J. Mat. Synthesis and Processing, 5, No. 1, 111–116 (1997).Google Scholar
- (11).Shaffer, P.D., “Realities of Paint Transfer Efficiency,” Industrial Finishing, 63, No. 1, 32 (1987).Google Scholar
- (12).Xing, L., Glass, J.E., and Fernando, R.H., “Parameters Influencing the Spray Behavior of Waterborne Coatings,” Journal of Coatings Technology, 71, No. 890, 37 (1999).Google Scholar
- (13).Settles, G.S., “A Flow Visualization Study of Airless Spray Painting,” Proc. of the 10th Annual Conference on Liquid Atomization and Spray Systems ILASS-Americas 97, Ottawa, Canada, 145–149 (May 1997).Google Scholar
- (14).Snyder, H.E., “Drop Size Investigation of an Electrostatically-Assisted Fan-Spray Atomizer,” M.S.M.E. Thesis, Purdue University (August 1988).Google Scholar
- (15).Fox, R.W. and McDonald, A.T., Introduction to Fluid Mechanics, 5th ed. Wiley, 1998.Google Scholar
- (16).McCarthy, J.E., “Basic Studies on Spray Coating Drop Rebound from a Small Workpiece with a Conventional Air Applicator,” M.S.M.E. Thesis, Purdue University (December 1991).Google Scholar