Learning Forum

[Marta R]

Hi! I am trying to do a thermal analysis in which I determine the temperature of a part placed near a hot part. They are not touching, but are close and the hot part is around 250 degrees F and the other is room temperature. The hot part is cast iron and the other is room temperature. I am new to Ansys and when I tried to do this, my temperature contour only showed my initial temperatures. How do I set up my analysis to show me the resulting temperature on the plastic part after a certain amount of time? Through this analysis I am just trying to see how much the hot part heats up the plastic and after how long.

[peteroznewman]

Hi Marta,

There are three ways heat can move from a hot iron part to a room temperature plastic part: convection, conduction, and radiation.

Convection means the air is heated and flows from the hot part to the plastic part.  Since hot air rises, if the plastic part is above the hot part, then a significant amount of heat can be transfered through convection, but if the plastic part is below the hot part, then no heat would be transferred by convection. If the two parts are sitting on a tabletop some amount of heat could be transferred. To simulate this, you need to build a Computational Fluid Dynamics simulation using Fluent. Transient Thermal can only predict the rate at which a hot object will lose heat to the room temperature air, it can't transfer that heat to the plastic part.

You say the two parts are close but not touching so there can't be any direct conduction, but if they are both sitting on another object like a metal tabletop, then heat can travel through the tabletop. But if the tabletop was wood, an insignificant amount of heat would be conducted. You can simulate this using a Transient Thermal analysis or in Fluent.

Radiation allows heat to leave the hot part into surrounding cooler space. Some of that radiation will fall on the cooler plastic part, raising its temperature. Transient Thermal can compute the radiation transfer and so can Fluent.

In Transient Thermal, ignore any conduction (wood tabletop), put a Convective Boundary Condition on the hot part to allow air to cool it, and put a Radiation Boundary Condition on the iron and plastic parts and allow some heat to transfer to the plastic cup, you will be able to make an estimate of the temperature on the surface of the plastic cup over time.