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clc();
clear;
// To calculate the amount of water evaporated in per hour for a square foot of water surface
u=3.82*10^-7; // Viscosity in lb-sec/ft^2
rho=2.3*10^-3; // Density in lbsec^2/ft^4
A=1; // Area in ft^2
Cp=0.24; // Specific heat capacity in abtu/lbm-degF
v=4*3600; // Velocity in ft/sec
k=0.015; // Thermal conductivity in Btu/hr-ft-degF
p=14.7; // Atmospheric pressure in psi
M=29; // Avg. molecular weight of air
T1=70+460; // Temperature of still air in degF
T2=90+460; // temperature of surface of water in degF
L=1; // For characteristic of 1 ft
D=0.992; // Diffusivity in ft^2/sec
// Heat transfer equation for laminar flow of a flat surface
Ngr=32.2*L^3*((T2/T1)-1)/(u/rho)^2; // Grasshops number
Npr=u*3600*Cp*32.2/k; // Prandtls number
Nnu=0.75*(Ngr*Npr)^.25; // Nusselt number
h=Nnu*k/L; // Heat transfer coefficient
Ns=u*3600/(rho*D); // Schimdt mumber
hmc=h*D*(Ns/Npr)^0.25/k; // Heat transfer coe
pv1=0.18; // Vapour pressure at 40% humidity
pv2=0.69; // Vapour pressure at saturation
pa1=p-pv1; // Absolute pressure of air at 40% rel. humidity in psi
pa2=p-pv2; // Absolute pressure of saturated air in psi
pbm=(pa1+pa2)/2; // Log mean pressure in psi
R=1544; // Universal gas constant in ft^3-psi/lbmol-degR
T=(T1+T2)/2; // Average temperature in degR
N=hmc*p*(pv2-pv1)*144/(R*T*pbm)*18; // mass transfer rate in lbmol/hr-ft^2
printf("The amount of water evaporated per hour is %.4f lb mol/hr-ft^2",N);
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