Handbook of Solvents - George Wypych - ChemTech - Ventech!

390 Seung Su Kim, Jae Chun Hyun
The Antoine equation coefficients A, B, C for various organic solvents can be found
elsewhere. 19 The UNIFAC group contribution method was used to calculate the activity coefficient
of each solvent. 49
7.3.2.3 Heat and mass transfer coefficient
The rate of heat transfer to the coating depends on the two factors as shown in Equation
7.3.2: the difference between the temperature of coating and ambient air (the driving force)
and the geometry where the heat transfer occurs (heat transfer coefficient). The heat transfer
coefficient is a function of the nozzle geometry and blowing air properties. Many variables
affect the heat transfer coefficient of nozzles, such as nozzle geometry and size, nozzle to
coating surface distance, nozzle to nozzle spacing, velocity of air at the nozzle exit and air
motion above the coating surface. 37,45
Therefore the average heat transfer coefficient of a zone can be expressed as follows,
where:
( ) ( )
h = f Geometry of nozzle,Pro perties of air × f w
[7.3.5]
h average heat transfer coefficient of a zone
w velocity of air at the nozzle exit.
Figure 7.3.3. Schematic diagram of modeled drying of coated film. [After reference 28].
The accuracy of drying rate calculation greatly depends on the proper estimation of the
heat and mass transfer coefficient of nozzles. Many researches have been done to find out
the heat transfer coefficient of nozzles, among them the Martin’s correlation is the notable
one which correlates the geometry of impinging jet nozzle and air velocity to the heat and
mass transfer coefficients. 37 For a multiple slot jet nozzles, which is depicted in Figure
7.3.4, Martin suggested following empirical correlation,