T_pond int1(z) Water temperature
Nu_pipe (nipfl.f/8)*Pr_pipe*nipfl.Re/(1.07+12.7*(nipfl.f/8)^0.5*(Pr_pipe^(2/3)-1)) Nusselt number turbulent flow
Pr_pipe nipfl.Cp*nipfl.mu/nipfl.k Prandtl number
h_inner Nu_pipe*nipfl.k/nipfl.dh Film heat transfer inside pipe
alpha 1.4e-7[m^2/s] Thermal diffusivity, water
beta 1.5e-4[1/K] Volumetric thermal expansion coefficient, water
Ra_pond g_const*beta*(T_pond-T)*nipfl.dh^3*(nipfl.rho/nipfl.mu)/alpha Rayleigh number
Pr_pond 8.81 Prandtl number
Nu_pond (0.6+0.387*Ra_pond^(1/6)/(1+(0.559/Pr_pond)^(9/16))^(8/27))^2 Nusselt number
h_outer Nu_pond*0.59[W/m/K]/nipfl.dh Film heat transfer coefficient outside pipe
U_tot 1/(1/h_inner+d_wall/k_wall+1/h_outer) Overall heat transfer coefficient
d_wall 2[mm] Thickness of pipe wall
k_wall 0.46[W/m/K] Thermal conductivity of high density polyethylene