G. Aguilar et al., Theoretical and experimental analysis of droplet diameter, temperature, and evaporation rate evolution in cryogenic sprays, INT J HEAT, 44(17), 2001, pp. 3201-3211
Cryogenic sprays are used for cooling human skin during selected laser trea
tments in dermatology. In order to optimize their cooling efficiency, a det
ailed characterization and understanding of cryogen spray formation is requ
ired. Various instruments and procedures are used to obtain mean size (D),
velocity (V), and temperature (T) of tetra-fluoroethane spray droplets from
straight-tube nozzles. A single-droplet evaporation model is used to predi
ct droplet diameter and temperature as a function of distance from the nozz
le, D(z) and T(z), from the values of D, V, and T at the ;nozzle exit, i.e.
, D-0, V-0, and T-0. In the model, it is assumed that D and V decrease in a
ccordance with the D-2-law, and due to drag force, respectively. To compute
T(z), the instantaneous D and V are incorporated into a phase-change heat
transfer balance, which includes a heat convection term. The predicted evol
utions of T(z) and D(z) are in reasonable agreement with experimental data.
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