Modelling Liquid Hydrogen Boil-Off Rate

[JB312]

TL;DR

I am working on modelling the liquid hydrogen boil-off for a storage tank (30m3) over a period of 2.5 hours using three different insulation materials - polyurethane foam, aerogel, and MLI.

The relevant thermal conductivity, heat transfer coefficients, and thicknesses along with all other required parameters are known. I have attempted to use the online simulation tool boilFAST to simulate each scenario however, the results show a negative spike in boil-off rate which I don't see being possible as this would imply that there is an increase in the volume of liquid hydrogen. Does anyone have any experience in modelling similar scenarios or know another simulation tool that might be useful? Thanks in advance.

 

[Chestermiller]

Please provide the data on heat transfer coefficients, thicknesses, thermal conductivities, shape. Also, starting mass- or volume fraction of liquid and starting temperature or pressure.

 

[JB312]

Certainly. Shape = horizontal cylinder with hemispherical end caps, volume = 30.02 m^3, initial liquid volume = 29.44 m^3, inner diameter = 2.93 m, length = 2.5 m (cylinder), relief pressure = 0.25 MPa, liquid temp = 20 K, pressure = 0.092 MPa, ambient temp = 293.15 K, insulation (MLI) thermal conductivity k = 0.00009 W m^-2 K^-1, thickness = 42.7 mm, corresponding heat transfer coefficient (k/thickness) = 0.0021 W m^-2 K^-1. Thank you very much for any help.

 

[Chestermiller]

What is the tank made of, and what is its wall thickness?

 

[Chestermiller]

Thermodynamic data on H2 are given in this reference: https://nvlpubs.nist.gov/nistpubs/Legacy/MONO/nbsmonograph168.pdf
The surface area for heat transfer is about 50 M^2, so the rate of heating is on the order of $$\dot{Q}=50(0.0021)(293-22)=28.5 W=102\ kJ/hr$$
The specific volume of liquid H2 at 20 K is 0.01412 m^3/kg, so the mass of liquid H2 originally in the tank is 29.44/0.01412 = 2085 kg.. At these temperatures, the heat of vaporization is about 450 kJ/kg, So, in 2.5 hours, roughly 0.6 kg would boil off.