Hello everyone, first of all, thank you very much for reading. I have to design a container (100 mm of height and 80 mm of interior radius of XPS) to keep a cryogenic mix (water and salt ice) at -15ºC at least for 40min. And my problem is to calculate the optimum thickness of XPS. I've been reviewing thermodynamic and heat transfer theory. I have conduction and convection so if I increase the thickness, I improve conduction but it's not good for convection. Also, I don't know how to connect the thermodynamics and heat transfer theory with warming the ice. I'm having some problems with the convection coefficient too. If somebody could help me I would be very grateful. Thanks!