calc Tr of aluminum object?

Is there a way to calculate the thermal resistance of an aluminum object?

I have these cool bowls made from cast aluminum. they're about 1/8" thick material, and about 4" square and 1.5" deep.

i'd like to just get a rough ballpark to see if further testing is feasable (which may otherwise deface the bowl) or if it's a non starter

here's the object in question

https://projects.dimension-x.net/pictures/albowl/topdown.jpg

It is possible to estimate the thermal performance - estimate suggests a level of inaccuracy. It's also possible to more accurately calculate the thermal performance. The "estimate" takes some work - the calculation quite a bit more and/or some fairly expensive software.

It might be simpler to experiment to see how it performs. How much effort should be applied is likely determined by your specific needs.

the object in the bowl is a 9 watt rgb star, so thats how much heat I'm dealing with. Junction temp not to exceed 85C. Lumileds claims I need a Tr of 11 ... but my math says 7.