1 Reply Latest reply on Aug 3, 2012 4:55 PM by Jerry Steiger

    Convection through air gap

    Danielle Little

      I am trying to run a thermal simulation of concentric cylinders where the inside cylinder is heated. A tube surrounds the heated cylinder with a small air gap in between (they are attached further down the cylinder with a small contact area, keeping the two concentric). The outside of the tube is at room temperature with natural convection. When I run the simulation with only conduction at the contacting surfaces, the air gap is considered insulation, so the inside cylinder does not heat up the tube at all where they are not contacting. In reality, this would not be the case. I would think there needs to be convection through the air gap, but to add a convective thermal load I have to specify the temperature of the air gap. This temperature is unknown because it depends on how much the inner cylinder heats up the air gap, versus the convection of the external air cooling down the outer tube. I seem to be able to specify radiation between the inside cylinder and outside tube, but this doesn't seem to have much of an affect- the thermal model shows the entire inside cylinder at it's original temperature (around 150 degrees C) and the entire outside cylinder as room temperature. Is there a better way to simulate the heat transfer through the air gap?

        • Re: Convection through air gap
          Jerry Steiger

          Danielle,

           

          I don't use SolidWorks Simulation much and have never used it for heat flow, but you don't seem to be getting any other answers, so I will chime in. The most correct way to analyze the heat flow through an air gap would be to run a CFD analysis.The next best would be to estimate a film coefficient for the convective heat transfer. It seems to me that this is pretty tricky for a cylindrical source and sink. You might want to use different film coefficients for different regions.If the gap is really thin, then you might need to allow conduction in the air.

           

          Jerry Steiger