Page 536 - Design and Operation of Heat Exchangers and their Networks

Appendix 519

end
while (ex > 350)
sy = sy ∗ CAS_EXP_350;
ex = ex - 350;
end
while (ex < -350)
sy = sy / CAS_EXP_350;
ex = ex + 350;
end
t_h_m = exp(ex) ∗ sy;
end
end

% dt_h/dx = t_c - t_h = - dt_c/dy, t_h(0,y) = 1, t_c(x,0) = 0
% t_h = exp(-x-y)∗sum < j = 0,inf >{y∗∗j/j!∗sum < k = 0,j >{x∗∗k/k!}}
% x = NTU_h, y = R_h∗NTU_h
function [t_h] = crossflow_t_h (x, y)
CAS_EXP_350 = 1.0070908870280796E152;
if (x == 0)
t_h = 1;
elseif (y == 0)
t_h = exp(- x);
else
j = 0;
sx = 1;
sy = 1;
ay = 1;
ex =-x-y;
while (abs(sx) > abs(sy) ∗ 1E-8)
j=j+ 1;
ay = ay ∗ y/j;
if (abs(ay) > CAS_EXP_350)
ay = ay / CAS_EXP_350;
sy = sy / CAS_EXP_350;
ex = ex + 350;
end
ax = ay;
sx = ay;