In most of the simulations with liquid as a coolant (for example water), the value of mass flow rate or velocity is provided at the inlet condition considering velocity-inlet boundary condition. And the outlet boundary condition is pressure-outlet.
Suppose, there is a rectangular duct consist of heating tubes in series and a liquid is flowing through the duct, across the tubes. How to calculate the velocity or mass flow rate at the inlet?
Mr.Simply by multiplying velocity m /second of material in the duct(liquid or gas) by cross section area m*2 of the duct we get flow rate by m*3/second
Mass flow rate within a closed system is constant - mass flow in = mass flow out.
If you know density of the fluid, you can calculate volume flow rate from mass flow rate, if you know cross sectional area of the duct you can calculate velocity from volume flow rate.
Pranjali,
For heat transfer we´d like to have the best efficiency. So, lets consider that the flow is a turbulent one. In this case, it´s important to calculate the hydraulic diameter of the rectangular duct, which depends on the cross-sectional area and the wetted perimeter.
After that, we can use the Colebrook interpolation in order to find the dimensionless head loss vs dimensionless velocity. Finally, we can calculate the velocity and the flow mass.
The formulas are attached in the file and I printed them from the book Fluid Mechanics, from Frank M. White, fourth edition.
So,first of all we must determine the velocity ........by any method as i mentioned before
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