What are the Appropriate Orifice Sizes for Uniform Exit Temperatures?

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Discussion Overview

The discussion revolves around determining appropriate orifice sizes for achieving uniform exit temperatures of 140°F from four components in a cabinet, with an ambient temperature of 70°F at sea level pressure. The context includes aspects of thermal management and fluid dynamics within a controlled environment.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant requests assistance in calculating orifice sizes for uniform exit temperatures from multiple components.
  • Another participant asks for clarification on the specifics of the flow, including whether it is internal or external, and suggests that the original poster needs to refine their question.
  • A later reply clarifies the scenario, indicating that air is heated inside the cabinet and proposes using conservation of mass and energy principles to approach the problem, while emphasizing the need for flow rate or velocity information to determine orifice area and diameter.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus, as there are differing levels of understanding regarding the specifics of the problem and the necessary parameters for calculation.

Contextual Notes

There are limitations in the information provided, including missing details on flow rates and velocities, which are essential for calculating orifice sizes. The discussion also depends on assumptions about the heating process and the properties of air at the specified conditions.

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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