Heat Transfer/ Fluid Dynamics

[elmandilon11]

I need help, hope somebody can give me a hint

Determine the appropiate orifice sizes for uniform exit temperatures of 140F from the four units in 70F ambient/ sea level pressure? Components (50W, 500W, 1000W and 300W)

Thank you

 

[navier1120]

you are going to have to be a little more specific here. Internal flow, external flow, modes of heat transfer? you clearly must be confused, you need to learn how to ask the right questions

 

[elmandilon11]

Sorry,

I do have a problem. It is a cabinet, it has 4 components. Each component has has an inlet an an exit orifice where the air passes through. I would like to determine the orifice size for uniform exit temperatures of 140F from the four components in 70F ambient at sea level pressure.

 

[navier1120]

Am I correct in saying that the air is heated inside the compartment? I will assume that I am. for started let's make a control volume. Say we make a control volume around one compartment. We know by conservation of mass that mdotin=mdotout, and that Q=mdot*cp*dt, where dt=To-Ti. So if we say that Q is the power given off by the heater inside the compartment (which is given in the problem) then we have everything we need to solve the problem.

remember that mdot=(rho)(A)(V), you know rho given the 1 atm at 70
you know Ti=70
To=140
Given Q
Solve for mdot

But you need to know a flow rate to know a velocity at which the air is entering the compartment so you can solve for area and then diameter.

I may have miss understood your question but if you are given a flow rate or velocity then follow these steps.