# Nusselt number

## Main Question or Discussion Point

Hello I need to calculate the nusselt number for natural gas in a buried pipeline. My question is how to calculate the convective heat transfer co efficient?
The data is 220000m3/h, pipe ID 35", gas temperature 100C and ground temperature is 4C, gas SG 0.65, k = 0.037 W/m-K, R= 441 J/kg-K, CP = 2016 J/Kg-K, gama = 1.28

Related Mechanical Engineering News on Phys.org
Mech_Engineer
Gold Member
Hello I need to calculate the nusselt number for natural gas in a buried pipeline. My question is how to calculate the convective heat transfer co efficient?
The data is 220000m3/h, pipe ID 35", gas temperature 100C and ground temperature is 4C, gas SG 0.65, k = 0.037 W/m-K, R= 441 J/kg-K, CP = 2016 J/Kg-K, gama = 1.28
Do you mean the convective coefficient for the outside of the pipeline? Or are you trying to find a temperature distribution inside the pipe?

I am trying to find temperature distribution inside the pipe. I guess nusselt number associate with the flow of the liquid and it take convective heat transfer co-efficient within the fluid and not between wall and fluid, please correct me if I am wrong.

Mech_Engineer
Gold Member
Nusselt number's general description: Dimensionless temperature gradient at the surface of a convection flow (not limited to internal flow).

There are several methods of dertermining or estimating the thermal distribution in a fluid travelling through a pipe of a different temperature. you will have to decide if the flow if fully developed or if you are within the hydrodynamic entrance region, and what sort of things you can assume about the flow such as incompressible, laminar/turbulent, constant pipe wall temperature, things like that.

One thing you might look into is the Momentum and Heat Transfer Analogy, a.k.a. the Reynolds Analogy. This analogy can give you an estimate of the fluid's temperature distribution based on its velocity distribution. Otherwise, The differential equation describing the heat flux in the fluid could get you to where you want to go.

well that is the problem I was not given any diffrential eq. all I was given is the above data

Mech_Engineer