Convective Coefficient Heating and Thermal Insulation

[EloyRD]

Good afternoon Comunity,

I'm designing a storage tank for Sodium Hydrosulfide (NaHS) 45% solution for a Mine in Peru. Due to the required storage temperature (as pointed in

http://www.genesisenergy.com/assets...hnical_Guide/Technical_Guide_10_31_11zip.pdf)

and the site conditions (Minimum registered temperature: -15 °C; Minimum average temperature: -5°C) we require to provide heating to the storage tanks.

I've been looking in the web and handbooks for some of the properties that are inputs in the determination of the convective heat transfer coefficient for the stored liquid.

The properties that I haven't found are:
- Specific Heat
- Thermal Conductivity
- Coefficient of Volumetric Expansion
- Molecular Mass of Liquid
- Boiling Point

I'd appreciate a link to some place where properties could be found.

Thanks for any commentary.

Kind regards.
Eloy Ruiz

 

[FredRosse]

I would be surprised if the properties you seek are relevant to the design problem. Generally tank insulation problems are dominated by the insulation properties, insulation thickness, and outside air convection. Try running your design assuming infinite (or very very high) convection coefficient on the contained fluid, you may find that this convection coefficient will have virtually no impact on the results.

For example, water would have a convection heat transfer coefficient on the tank wall of around 50 BTU/hr-ft2-F, but in the tank heat loss calculation, even with minimal insulation, the accuracy of this number is meaningless with respect to tank heat loss. Say you only have 1 inch of insulation, then the thermal resistance for the insulation is about 5 hr-ft2-F/btu, and the tank exposed to ambient has a convection coefficient of 5 BTU/hr-ft2-F, giving an R value of 0.2. Adding the two resistances in series, = 5.2 hr-ft2-F/BTU

Now consider the water convection coefficient inside the tank, say it is 25, or 250, or 2500 BTU/hr-ft2-F, then these resistances are 0.04, 0.004, 0.0004, and then the total resistance to heat flow is 5.24, 5.204, 5.2004 for the three assumptions, not a meaningful difference in overall resistance to heat flow. Note that if you assume infinite heat transfer coefficient for the liquid, the total resistance is 5.2, this answer is very slightly conservative with respect to your problem.