Thermal simulations - radiation heat transfer

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Thermal analysis provide you with the insights into energy transfer.

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There are three ways that heat moves from one place of higher temperature

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to another place of lower temperature

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conduction where heat is transferred through

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solids in direct contact with each other

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convection where heat is transferred through fluids

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and radiation where heat is transmitted by electromagnetic

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waves without any physical contact between objects.

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Using a heated temperature probe model placed in liquid nitrogen.

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We discuss how to set up a thermal study to see

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the effect of radiant energy on temperature of the probe.

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This design is a single component with three bodies.

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One for the fluid, one for the probe

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and one for the probe heater

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also in this environment directly above the probe but not touching.

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It is another heat source

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to analyze the design.

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We switch to the simulation workspace and select thermal study.

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First, we'll review the materials in the model using the study materials. Command

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the material for the probe and heater design are

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steel and we'll stick with the design material.

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The liquid however, is nitrogen. So we'll change the study material to nitrogen

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and click. OK.

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Now we'll apply the thermal loads

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generally.

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In thermal studies, we apply thermal loads directly to a face or body in the design.

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In this example,

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we'll leverage the liquid nitrogen body surrounding the

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probe which is removing heat from the probe

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to help the thermal loading,

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select the applied temperature load,

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then pick the body that represents the liquid nitrogen in the vessel.

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Set the value for the temperature to minus 196

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°C,

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which is the temperature of liquid nitrogen.

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Next to represent the heat source directly above the probe,

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we'll apply a radiation load to the top base of the probe.

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Absorptivity is a measure of how much radiation is absorbed

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by a body with values ranging from 0 to 1.

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Although metals are generally poor at absorbing radiant heat

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for this study will set the absorption value to 0.9.

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And at the same time, set the local ambient temperature to 27

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°C.

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Lastly, we'll set the temperature of the probe heater.

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We want to apply an internal heat load of 0.9 bt

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per second per cubic inch

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to do this. Choose the internal heat load, then select the heater body,

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activate unit volume

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change the heat units,

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then apply an internal heat value of 0.9

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precheck shows there are no issues with the set up. So now we can solve the model.

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When the analysis is complete, we can check the results.

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You can see the extreme temperature difference in the probe

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at the bottom of the probe where it meets the liquid nitrogen.

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The liquid is still 196 degrees below zero °C

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at the top of the probe where it is heated

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both by the probe heater and the radiant heat from the external source.

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The temperature reaches over 42

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°C

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to see if the radiant heat is contributing to the 42

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°C,

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create a slice plane to check the temperature distribution inside the probe,

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select the front face of the liquid block and drag the plane into the model.

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Notice that the temperature of the probe increases above the pro heater

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indicating that the radiant heat is contributing to the temperature of the probe.

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It cools rapidly below the probe heater,

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but it still carries some heat down into the liquid nitrogen.

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You can hide the plane from the browser

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and turn it off when you no longer need it.