Determine what thickness of insulation is required to ensure the external surface temperature of a shell and tube partia

[answerhappygod]

Determine what thickness of insulation is required to ensure the
external surface temperature of a shell and tube partial condenser
is at a safe temperature for personnel.
The inner diameter of the condenser is 5.4m and the shell is
0.3m thick. There are 4 tube-side passes and 39,500 tubes (which
seems like a high number now that I think about it but whatever
that's how I have designed it) each with an outer diameter of
0.016m, an inner diameter of 0.014m, and measuring 7.32m long.
The tube-side fluid is a water coolant entering at 23°C and
exiting at 40°C, the shell-side fluid is a crude styrene mixture
entering as a vapour at 568°C then separating into a condensed
stream and a vapour stream which exit at 33°C. The tubes and shell
of the condenser are made of steel, you may chose the most suitable
insulation material, justify your choice.