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clc();
clear;
// To find heat changes and temperature change on heating of a concrete wall
b=9; // Thickness of the wall in ft
A=5; // Area of wall
k=0.44; // Thermal conductivity in Btu/hr-ft-degF
Cp=.202; // Specific heat in Btu/lbm-degF
rho=136; // Density in lb/ft^3
function[t]=templength(x); // Temperature function in terms of length
t = 90 - 80*x +16*x^2 +32*x^3 -25.6*x^4;
funcprot(0);
endfunction
tgo = derivative(templength,0); // Temperature gradient at x=0ft
tgl = derivative(templength,9/12); // Temperature gradient at x=9/12ft
qo = -k*A*tgo; // Heat entering per unit time in Btu/hr
printf("Heat entering per unit time is %.2f Btu/hr \n",qo);
ql = -k*A*tgl; // Heat coming out per unit time in Btu/hr
printf(" Heat coming per unit time is %.2f Btu/hr \n",ql);
q3 = qo-ql; //Heat energy stored in Btu/hr
printf(" Heat energy stored in wall is %.2f Btu/hr \n",q3);
a=k/(rho*Cp); // Thermal diffusivity
function[t2]=doublederivative(y); // Derivative of tempearture with respect to length in degF/ft
t2= -80+32*y+96*y^2-102.4*y^3;
funcprot(0);
endfunction
timeder0=a*derivative(doublederivative,0); // derivative of temperature wrt time at x=0 in degF
printf(" Time derivative of temperature wrt time at x=0ft is %.2f degF/hr\n",timeder0);
timeder1=a*derivative(doublederivative,9/12); // derivative of temperature wrt time at x=9/12 in degF
printf(" Time derivative of temperature wrt time at x=9/12ft is %.2f degF/hr\n",timeder1);
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