Chapter 12, Problem 12.146P

Our students perform a laboratory experiment to determine mass transfer from a wet paper towel experiencing forced convection and irradiation from radiant lamps. For the values of $T_{\infty }$ and $T_{wb}$ prescribed on the sketch, the towel temperature was found to be $T_s=310K$ . In addition, flat-plate correlations yielded average heat and mass transfer convection coefficients of $\bar{h}=28.7{\text{ W/m}}^2\cdot K\text{ and }{\bar{h}}_m=0.027\text{ m/s}$ , respectively. The towel has dimensions of $92.5\text{mm x 92}\text{.5mm}$ and is diffuse and gray with an emissivity of 0.96.

(a From the foregoing results, determine the vapor densities, ${\rho }_{A,s}\text{ and }{\rho }_{A,\infty }$ , the evaporation rate, $n_A\left(kg/s\right)$ , and the net rate of radiation transfer to the towel, $q_{rad}\left(W\right)$ .

(b) Using results from part (a) and assuming that the irradiation $G$ is uniform over the towel, deter- mine the emissive power $E$ , the irradiation $G$ , and the radiosity $J$ .