Component 160: Storage for compressible fluids

Specifications

Line Connections
1	Main inlet
2	Main outlet
3	Steam outlet
4	Liquid phase extraction outlet
5	Averaged liquid volume fraction (liquid level) during the time step
6	Coupled thermal heat inlet

General User Input Values Physics Used Characteristic Lines Results Displays Example

General

This component uses identical physical algorithms as Component 119 (Indirect Storage). In contrast to Component 119, Component 160 enables an explicit specification of the modes of operation (see flag FOMOD):

simultaneous charging and discharging
charging
discharging
cooling down (no inflow or outflow of the fluid)

It is important that the fluid in the storage system has a correlation between the fluid pressure and the specific volume/density of the fluid and that this correlation can be described by the corresponding material table. Hence the name "Storage for compressible fluids".

Component 160 also enables a correct treatment of the two-phase state and the separate discharging of the liquid and the gaseous phase (Pins 3 and 4).

Thus it is possible to use Component 160 for e.g. the following applications:

Pressurized air storage system
Gas storage system (e.g. natural gas)
Ruths storage

The use of Pins 2, 3, and 4　depends on the type of fluid and on the respective material table respectively.　If the modelled fluid is only in the gaseous phase (e.g. air), only the use of Pin 2 makes sense. In this case, the fluid stored in Component 160 will exit via Pin 2 in unchanged state. If the modelled fluid is only in a two-phase state (e.g. water/steam),　the use of Pins 3 and 4 makes sense. In this case, the liquid and the gaseous phase are separated and can be extracted from the storage system via Pin 3 and 4 respectively. At Pin 5, the volume fraction of the liquid phase is displayed as mass flow and can thus be used for the closed-loop control.

If the flag FINST has the value 1 (steady-state solution), the component will set the enthalpy values and the pressure values at the outlet lines to be identical with the enthalpy at the inlet (PIN 1). In the case of FINST=1, the component CANNOT ensure adherence to the steady-state mass and energy balance because the mass flows at the pins have to be specified by the user. The mode FINST=1 only serves to topologically include the component into the model in the case of the steady-state simulation. The transient charging and discharging processes where the transient mass and energy balances are adhered to MUST NOT be calculated in the mode FINST=1.　

User Input Values

FINST	Flag: Determination of transient calculation modes Like in Parent Profile (Sub profile option only) Expression = 0: transient solution according to time series table = 1: Always steady state solution = 2: Transient solution as single calculation, time=TIMESING = 3: Transient solution as single calculation, use TIMEMAX from model options
FINIT	Flag: Initializing state =0: Global, which is controlled via global variable "Transient mode" under Model Options "Extras" ->"Model Options" -> "Simulation" -> "Transient" -> Combo Box "Transient mode" (See -> Used Physics / equations -> Global Initialization of Transient Components ) =1: First run -> Initializing while calculating steady state values =2: Continuation run -> Values from previous time step are input for the present ones
FALGINST	Flag: Determination of transient calculation algorithms = 1: Crank-Nicolson-Algorithm = 4: Combined numerical and analytical solution
FOMOD	Flag: Operation mode (not relevant for initialization) = 0: Inlet and outlet open = 1: Charging (inlet open only) = 2: Discharge (outlet open only) = 3: Inlet and outlet closed = 4: Automatic (component determines the operation mode depending on the inlet / outlet mass flow values)
FINPR	Flag: Inlet pressure handling (not relevant for FINST=1, FINIT=1) Like in Parent Profile (Sub profile option only) Expression =0: P1 set by component if inlet open =1: P1 given from outside
ASTO	Heat exchanging area of storage
MSTO	Mass of storage
VFLUID	Volume of fluid
THISO	Thickness of insulation
MRINPART	Ratio of internal parts to wall mass
FMAT	Flag: Storage wall material Material Properties of Steel =-1 : Properties calculated by Kernel expression ERHO, ELAM, ECP
ERHO	Function for material density
ELAM	Function for material heat conductivity
ECP	Function for material heat capacity
LAMISO	Heat conductivity of insulation
FTTI	Flag: Handling of temperature during time interval Like in Parent Profile (Sub profile option only) Expression =0: Actual temperature at the end of time step =1: Average temperature for time step interval =2: Linear interpolation at each time step
FTSTEPS	Flag: Specification of (sub-) time steps Like in Parent Profile (Sub profile option only) Expression =1: By specification value TISPEP =2: 0.2 of the stable theoretical time increment =3: 0.5 of the stable theoretical time increment =4: 1.0 of the stable theoretical time increment =5: 2.0 of the stable theoretical time increment =6: 5.0 of the stable theoretical time increment
ISUBMAX	Maximum number of time sub steps for initialization
IERRMAX	Maximum allowed error for initializing step
TISTEP	Time step
NRAD	Number of points in wall-normal direction (max. 30)
TIMESING	Integration time for single calculation when FINST=2
FFREQ	Flag: Frequency of transient calculations Like in Parent Profile (Sub profile option only) Expression =1: At each iteration step =2: At each 2nd iteration step =3: At each 4th iteration step =4: At each 8th iteration step
FALPHI	Flag: Determination of alpha inside Like in Parent Profile (Sub profile option only) Expression =0: internal formulas: VDI-WA-11 F3 =1: From constant value ALPHI =2: From function EALPHI
ALPHI	Heat transfer coefficient alpha inside (wall to fluid) when FALPHI=1;
EALPHI	Function for alpha inside
FALPHO	Flag: Determination of alpha outside Like in Parent Profile (Sub profile option only) Expression =0: From constant value ALPHO =1: From function EALPHO
ALPHO	Outer heat transfer coefficient (to ambient) when FALPHO=0
EALPHO	Function for alpha outside
PMIN	Min Allowed Pressure
PMAX	Max Allowed Pressure
TMIN	Lower limit for storage temperature
TMAX	Upper limit for storage temperature
FSTAMB	Flag: Definition of ambient temperature Like in Parent Profile (Sub profile option only) Expression =0: Definition specification value (TAMB) =1: Defined from superior model
TAMB	Ambient temperature
FSTARTFL	Flag: Initial fluid state in storage Like in Parent Profile (Sub profile option only) Expression =0: from PFLSTART, HFLSTART =1: from steady state flow solution (M1=M2)
HFLSTART	Initial fluid enthalpy
PFLSTART	Initial fluid pressure
FISTART	Flag: Specification of the storage start temperature Like in Parent Profile (Sub profile option only) Expression =1: equal initial fluid temperature (adiabatic conditions) =2: from steady state solution (non-adiabatic conditions)
TIMETOT0	Total time at start of calculation (Sum of previous time steps)

Results

TAVBEG	Averaged caloric temperature of the storage in the beginning of the time step
TAVEND	Averaged caloric temperature of the storage at the end of the time step
QSTO	Amount of heat stored during time step (storage wall and fluid)
QAV	Averaged stored heat flow during the time step (storage wall and fluid QSTO/TIMEINT)
QAVI	Averaged heat flow from fluid to storage
QAVO	Averaged heat flow from storage to ambient environment
RALPHI	Calculated heat transfer coefficient fluid-storage
RALPHO	Calculated heat transfer coefficient storage-ambient
RMSTO	Mass of the storage wall
RVFLUID	Overall fluid volume in the storage
MFLUID	Overall fluid mass in storage
PFLAV	Mean fluid pressure
HFLAV	Mean fluid enthalpy
TFLAV	Mean fluid temperature
RTAMB	Ambient temperature
TIMETOT	Total time at the end of calculation

Physics used / Equations

The calculation of Component 160 is based on the same algorithms like that of Component 119. It calculates in the mode FSPECM=4, in analogy to Component 119. However, Component 160 has no pipe geometry and thus there is no axial flow direction. Thus the numerical 2-D grid contains only one cell in X-direction. In the wall-normal Y-direction, Component 160 can contain several cells in the case of the Crank-Nicolson-Algorithm. The number of cells is controlled via the flag NRAD. In the case of the combined analytic and numeric method, the storage wall is solved only with one cell also in Y-direction.

The condition of the fluid in the storage system – mass, pressure, internal energy, chemical composition – is determined anew in each time step and is saved as input for the next time step. The new fluid condition results from the previous condition, from the parameters and quantities of the fluids flowing in and out in the current time step as well as from the time step length. The fluid volume of the storage system remains unchanged and thus the pressure in the storage system changes with the change of the specific volume of the fluid, which can e.g. be caused by differences between the mass flows flowing in and out or by the change of the parameters of the fluid flowing in.

The enthalpy at outlet 3, 4 does not equal the current mean enthalpy of the fluid in the storage system. By contrast, these enthalpies are determined from the respective phase states.

Regarding the mass flow specification, Component 160 remains passive and adopts the specified mass flows from Pins 1-4. Only at Pin 5, the volume fraction of the liquid phase is set as mass flow.

The enthalpy H1 is always expected externally. The enthalpies H2, H3, H4 are set to equal the fluid enthalpy or enthalpy of the gas and liquid phase respectively in the storage system.

The pressure P2 equals the fluid pressure in the storage system averaged over the time step. For the pressure P1, there are two modes that are controlled via the flag FINPR. At FINPR=0, Component 160 sets the pressure on the line connected to Pin 1 to equal the fluid pressure in the storage system averaged over the time step. At FINPR=1, Component 160 adopts the pressure from the line connected to Pin 1. In this case, however, the pressure on the line must be at least as great or greater than the fluid pressure in the storage system.

If a thermal heat is coupled from externally (e.g. electrical heating elements inside the storage) it can be modelled using the logical Pin 6 by specifying the corresponding power heat value.

Characteristic Lines and Matrices

All characteristic lines form a circular buffer. The user doesn´t have to take care of them.

CMFL: Mass of fluid1 in differential element of storage dV (not used in every case)
CUFL: Internal energy of the fluid in differential element of storage dV (not used in every case)
CDAT: Partial/heat flow between elements of fluid and wall
CHFL: Enthalpy of the fluids in differential element of storage dV
CTFL: Temperature of the fluid in differential element of storage dV
CSTAT: Thermodynamical state of the fluid at the lines
CQHIST: History of the heat flows
CTIHIST: History of the time steps

Corresponding to this there are also result curves.

RAMFL: Mass of fluid in differential element of storage dV (not used in every case)
RAUFL: Internal energy of the fluid in differential element of storage dV (not used in every case)
RADAT: Partial/heat flow between elements of fluid and wall
RAHFL: Enthalpy of the fluids in differential element of storage dV
RATFL: Temperature of the fluid in differential element of storage dV
RASTAT: Thermodynamical state of the fluid at the lines
RAQHIST: History of the heat flows
RATIHIST: History of the time steps

Specification matrix MXTSTO and result matrix RXTSTO

The matrix MXTSTO is linked to the output field RXTSTO in the same way as the characteristic curves and result curves mentioned above.

The distribution of the values in the storage and the fluids is stored in both matrices (default matrix MXTSTO for time step t-1 and result matrix RXTSTO for time step t).

For the structure of the matrices, see matrices of component 160.

Displays

Display option 1

Example

Click here>> Component 160 Demo << to load an example.

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