Radiation in vacuum
 

Dear friends i m solving a radiation in vacuum problem using CFX monte carlo model. Details given below

one close box with vacuum inside is there which is kept on rectangula pipe through which fluid is flowing with inlet temperature is 200 K & wall opposite to common wall between pipe & box is at 400 K & all other four walls are adiabatic.
so common wall temp is governed by convection and conduction in rectangula pipe flow & radiation in closed box
so how to obtain vacuum in closed box so that it can solve only for radition in box & not for conduction & convection but will solve for conduction & convection in pipe

I know the vacuum pressure 0.01

Thanks in advance