Thermal Radiation between Surfaces
Thermal Radiation between Surfaces
(OP)
Hi All,
I'm doing some FEA on heat transfer by radiation between surfaces of solid bodies(using ANSYS). A hollow cylinder in "VACUUM" is subjected to uniform heat fulx on it's outer surface. Two water cooled jackets, one on the outside and the other inside maintained at 26C are used to absorb the radiated heat. The model looks like 3 concetric hollow cylinders.
The problem that I'm runnin into is with the space temperature, i.e. the temperature between the cylinders. I guess the space/gap temperature depends on the temperatures of the cylinder surfaces. But, I need to specify the space/gap temperature in order to solve the problem. How can I pick a particular temperature for this gap? It is vacuum and nothing is really maintaining this temperature. I randomly used different numbers for this gap tamperature and the cylinder temperatures are different for different gap temperatures. Therefore, I concluded that the gap temperature is important to obtain sensible results.
can you guys please comment on this.
All the suggestions are appreciated
Thanks,
FEAVNIK
I'm doing some FEA on heat transfer by radiation between surfaces of solid bodies(using ANSYS). A hollow cylinder in "VACUUM" is subjected to uniform heat fulx on it's outer surface. Two water cooled jackets, one on the outside and the other inside maintained at 26C are used to absorb the radiated heat. The model looks like 3 concetric hollow cylinders.
The problem that I'm runnin into is with the space temperature, i.e. the temperature between the cylinders. I guess the space/gap temperature depends on the temperatures of the cylinder surfaces. But, I need to specify the space/gap temperature in order to solve the problem. How can I pick a particular temperature for this gap? It is vacuum and nothing is really maintaining this temperature. I randomly used different numbers for this gap tamperature and the cylinder temperatures are different for different gap temperatures. Therefore, I concluded that the gap temperature is important to obtain sensible results.
can you guys please comment on this.
All the suggestions are appreciated
Thanks,
FEAVNIK





RE: Thermal Radiation between Surfaces
i think the heat capacity of the coolant is dependent on the temperature in the middle of the cyclinder (amongst a host of other parameters). if the coolant can remove the radiant heat, then the temperature inside the cyclinder will be constant. if the coolant can't the the temperature in the cyclinder will increase; why wouldn't it run away ?
the problem would be trickier if you had a control valve on the quantity of coolant, so that if you detect a temperature increase inside the cyclinder, then the heat capacity of the coolant is increased (higher flow?) trying to stabilise the situation.
RE: Thermal Radiation between Surfaces
corus
RE: Thermal Radiation between Surfaces
I agree with corus. In fact, there is no temperature in a vacuum. http
There is no participating medium in a vacuum. There is only the radiating and recieving surfaces. You would, of course see variation in the results if you include a temperature in the vacuum space. That is not reality and the results you are seeing are false.
RE: Thermal Radiation between Surfaces
RE: Thermal Radiation between Surfaces
you got replies about 180deg apart. i agree that there is no temperature in a vaccuum, as there's nothing to absorb the heat. so is it a software "glitch" ?
you've got heat input and heat output ... how are these kept in equilibrium ?
RE: Thermal Radiation between Surfaces
corus