DuctFlow_Laminar
Procedure DuctFlow_Laminar(Re,Pr,LoverD_h,Aspect: Nusselt_T, Nusselt_H, f) returns the average Nusselt number and friction factor for a rectangular duct characterized by Reynolds and Prandtl numbers, length/diameter, and aspect ratio. The Reynold's number is expected to be < 2300.
Inputs:
Re - Reynolds number based on properties evaluated at the bulk average temperature
Pr - Prandtl number of the fluid evaluated at the bulk average temperature
LoverD_h - ratio of tube length to hydraulic diameter.
Aspect - ratio of the minimum to the maximum dimensions of the channel (Aspect <=1)
Outputs:
Nusselt_T - average Nusselt number assuming a constant wall temperature
Nusselt_H - average Nusselt number assuming a constant wall heat flux
f - apparent Darcy friction factor [-] .
Notes:
The Darcy friction factor is calculated using a correlation recommended in Eqn 3.158, p. 3.46 of Kakaç et al. The correlation is strictly applicable in the fully-developed region, but is used here for the developing region as well by correcting it using the form provided by Shah and London.
The average Nusselt number for constant wall temperature and constant wall heat flux are based on interpolated data from Table 3.17 of Kakaç et al. The data in this table corresponding to the developing region of the thermal and hydrodynamic boundary layers are for a Prandtl number of 0.72. The values are adjusted for other Prandtl numbers using interpolated data in Table 3.18 of Kakaç et al which is for a square duct with a constant wall heat flux; however, the correction factor obtained for this situation is applied to all ducts, independent of aspect ratio or boundary condition.
Results for a thermally developing/hydrodynamically developed flow can be obtained by calling the procedure with a large Prandtl number.
Set Aspect to zero to obtain the Nusselt number for flow between parallel plates.