Pavan Kumar
Chemical
- Aug 27, 2019
- 393
Hi All,
I have a Heat Exchanger vessel which is 82.25" OD and 133.25" long shell. I want to calculate the acceptable insulation thickness. The shell side has Hot Boiler feed water at average of 130 Deg C. The worst ambient temperature can be -10 Deg C. Can I calculate the heat loss for this vessel just as we do for pipes as below, assuming no resistance to heat transfer from the vessel wall itself.
q= k. AL. (T1-T2)/(r2-r1)
where,
k is the thermal conductivity of the insulation. (k = 0.029 Btu/hr-ft Deg F for mineral wool at 100 Deg F)
AL is the log mean area = 2.PI()*(r2-2r1)/ln(r2/r1)
T1 is the temperature at the vessel outside surface T1 = 130 Deg C = 266 Deg F
T2 is the temperature at the outside surface of insulation. T2= -10 Deg C = 14 Deg F
r1 and r2 are the radius at the vessel outside and the outside of the insulation
Based on my calcs, I get heat loss as function of insulation thickness as follows:
I know there is a balance on insulation cost vs. cost of heat loss, but I learnt somewhere that there increasing thickness beyond a certain thickness would result in increase in heat loss. I know I have not taken in consideration the effect of air resistance.
My questions :
1. Can I calculate the optimum insulation thickness for a vessel just like a pipe?.
2. Can I ignore for simplicity sake the resistance of air in optimum insulation thickness calculation?.
Thanks and Regards,
Pavan Kumar
I have a Heat Exchanger vessel which is 82.25" OD and 133.25" long shell. I want to calculate the acceptable insulation thickness. The shell side has Hot Boiler feed water at average of 130 Deg C. The worst ambient temperature can be -10 Deg C. Can I calculate the heat loss for this vessel just as we do for pipes as below, assuming no resistance to heat transfer from the vessel wall itself.
q= k. AL. (T1-T2)/(r2-r1)
where,
k is the thermal conductivity of the insulation. (k = 0.029 Btu/hr-ft Deg F for mineral wool at 100 Deg F)
AL is the log mean area = 2.PI()*(r2-2r1)/ln(r2/r1)
T1 is the temperature at the vessel outside surface T1 = 130 Deg C = 266 Deg F
T2 is the temperature at the outside surface of insulation. T2= -10 Deg C = 14 Deg F
r1 and r2 are the radius at the vessel outside and the outside of the insulation
Based on my calcs, I get heat loss as function of insulation thickness as follows:

I know there is a balance on insulation cost vs. cost of heat loss, but I learnt somewhere that there increasing thickness beyond a certain thickness would result in increase in heat loss. I know I have not taken in consideration the effect of air resistance.
My questions :
1. Can I calculate the optimum insulation thickness for a vessel just like a pipe?.
2. Can I ignore for simplicity sake the resistance of air in optimum insulation thickness calculation?.
Thanks and Regards,
Pavan Kumar