Examples

This page provides examples of common HydDown calculations.

Vessel Depressurization

Isentropic Depressurization

Calculate adiabatic depressurization of a hydrogen vessel through an orifice:

vessel:
  length: 2.0
  diameter: 0.5
  orientation: "vertical"
  type: "Flat-end"

initial:
  pressure: 15000000
  temperature: 293.15
  fluid: "Hydrogen"

calculation:
  type: "isentropic"
  time_step: 0.1
  end_time: 100

valve:
  flow: "discharge"
  type: "orifice"
  diameter: 0.01
  discharge_coef: 0.84
  back_pressure: 101325

Vessel Filling

Filling with Heat Transfer

Model vessel filling with heat transfer to surroundings:

vessel:
  length: 2.0
  diameter: 0.5
  thickness: 0.01
  heat_capacity: 500
  density: 7800
  orientation: "vertical"

initial:
  pressure: 100000
  temperature: 293.15
  fluid: "Hydrogen"

calculation:
  type: "energybalance"
  time_step: 0.1
  end_time: 300

valve:
  flow: "filling"
  type: "controlvalve"
  Cv: 0.1
  back_pressure: 20000000

heat_transfer:
  type: "specified_h"
  h_inner: 100
  h_outer: 10
  temp_ambient: 293.15

Fire Scenario

Pool Fire Heat Load

Simulate vessel response to a pool fire:

vessel:
  length: 5.0
  diameter: 1.0
  thickness: 0.02
  heat_capacity: 500
  density: 7800
  orientation: "horizontal"
  type: "ASME F&D"

initial:
  pressure: 10000000
  temperature: 293.15
  fluid: "Hydrogen"

calculation:
  type: "energybalance"
  time_step: 0.1
  end_time: 600

valve:
  flow: "discharge"
  type: "relief"
  set_pressure: 12000000
  back_pressure: 101325

heat_transfer:
  type: "s-b"
  fire: "api_pool"

Relief Valve Sizing

API 521 Relief Valve

Size a relief valve for fire scenario per API 521:

vessel:
  length: 10.0
  diameter: 2.0
  thickness: 0.03
  heat_capacity: 500
  density: 7800
  orientation: "horizontal"
  type: "Hemispherical"

initial:
  pressure: 8000000
  temperature: 293.15
  fluid: "Methane"

calculation:
  type: "energybalance"
  time_step: 0.5
  end_time: 1800

valve:
  flow: "discharge"
  type: "relief"
  set_pressure: 8500000
  back_pressure: 100000

heat_transfer:
  type: "s-b"
  fire: "api_jet"

Two-Phase Calculations

Liquid Hydrogen Storage

Model two-phase hydrogen storage with boiling:

vessel:
  length: 3.0
  diameter: 1.0
  thickness: 0.015
  heat_capacity: 900
  density: 2700
  thermal_conductivity: 200
  orientation: "vertical"
  type: "Flat-end"
  liquid_level: 0.5

initial:
  pressure: 200000
  temperature: 25.0
  fluid: "Hydrogen"

calculation:
  type: "energybalance"
  time_step: 1.0
  end_time: 3600

valve:
  flow: "discharge"
  type: "mdot"
  mdot: 0.01
  back_pressure: 101325

heat_transfer:
  type: "specified_h"
  h_inner: 50
  h_outer: 5
  temp_ambient: 293.15