What are the Appropriate Orifice Sizes for Uniform Exit Temperatures?

AI Thread Summary
The discussion focuses on determining the appropriate orifice sizes for achieving uniform exit temperatures of 140F from four components in a cabinet, given a 70F ambient temperature and sea level pressure. Key considerations include understanding internal flow, external flow, and modes of heat transfer. The conservation of mass and energy principles are emphasized, particularly the relationship between mass flow rate, heat transfer, and temperature change. To calculate the orifice size, a flow rate or velocity must be known to derive the necessary area and diameter. The conversation highlights the importance of clearly defining parameters and understanding the underlying physics to solve the problem effectively.
elmandilon11
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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
 
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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
 
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.
 
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.
 

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