Heat transfer on concave and flat surfaces.

Unless the box is very thick the difference in thermal conductivity between Aluminum and Stainless Steel is not significant. More surface area means more heat transfer surface, but I'm not sure if you are saying your concave surface is facing your heat sink or your heat source (or both). Do you expect the stuff in the box to be hot and need to cool down?

Hello,

Thank you for replying. The box's concave surface will be facing the heat source...I think. The source of the heat would be the sun. Im asking because the box will be situated outside. The stuff inside the box will need to be relatively cooled (max 104 Fahrenheit). Besides I'm going to install two small cooling fans inside.

Without seeing more detail, here is how I see your problem. Your heat source is radiation from the sun. Your heat sink is conduction/convection to the air around the box. To reduce heat transfer from the sun, you could put the box in the shade (best), make a mirrored surface to reflect the energy or make a second layer to the box with an open air gap to break up the energy transfer to the inside of the box. To increase heat transfer from the box, you could put the box in a windy place or put a fan near it to circulate air. You could also increase the surface area for heat transfer by putting fins on the box. Note that the best you can possibly be is air temperature. If the air is >90F, you are going to be challenged to put a box in the sun.

This helped a lot. Thank you very much. One last question, how do you know all this? the reason I'm asking is if you wouldn't mind me quoting you on the project im working on, the reason for these questions.

Glad to help. I'm a chemical engineer with 30+ years of experience so I do a lot of heat transfer work, but this is basic thermodynamics. You would get the same from a thermo textbook.