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EBSILON Professional Components / Components - General and Categories / Throttles and Valves / Component 13: Piping
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    Component 13: Piping
    In This Topic

    Component 13 : Piping

    Specifications

    Line connections

     

    1

    Inlet

    2

    Outlet

    3

    Control inlet for pressure drop (as P)

     

    General       User Input Values       Physics Used       Displays       Example

     

    General

    When two components are connected by a pipe in Ebsilon, this means that mass flow, pressure, and enthalpy at the outlet of the one component equal the values at the inlet
    of the other component. This corresponds to an ideal pipe without any losses.

    In a real pipe, however, there will be pressure and heat losses. This component “Piping” (13) has been developed to allow to consider these losses in the model. To do so,
    the connection between the two components has to be severed, and a Component 13 has to be inserted.

    By default, the pipe is designed phenomenologically, i.e. the amount of heat lost and the extent of the pressure drop are entered in the design case. The losses are then
    scaled accordingly in off-design calculations.

    Alternatively, however, Ebsilon can also calculate the pressure drop if the geometry of the pipe is specified.

    To define the heat loss of the pipe, a temperature drop or an enthalpy drop can be specified alternatively as well. There are different options with regard to the off-design behaviour too.
    Details are described along with the flag FDN.
    A flag FDP is used to switch between phenomenological and geometrical pressure drop calculation for the design of the pipe. As a third alternative, it is also possible here not to carry
    out a pressure drop calculation but to set the outlet pressure externally on the pipe.

    The following is to be specified for the geometrical pressure drop calculation:


    The corresponding algorithms are stored both for one-phase and for two-phase flows. The calculation process is described in detail for Component 113 (Line focusing solar collector)
    in the chapter “Pressure loss“.

    As the fluid speed is also determined (and output as a result value) in the geometric pressure drop calculation, the compliance with the maximum fluid speed defined in the specification value WMAX can be checked. A warning is output in the event of an exceedance.

    For the phenomenological pressure drop calculation, the specification value DP12RN has to be specified in the design case. Depending on the flag FDP12RN this is

    The variants FDP12RN=2, 3, or 4 only differ regarding their off-design behaviour. Details are described along with the flag FDP12RN.

    The flag FVALDP allows to use a pseudo measuring point on an auxiliary line (FVALDP=1) or the control inlet (Pin 3) of the component (FVALDP=2) instead of specification
    value DP12RN. In the case of FVALDP=2, a logic line is to be connected to Inlet 3, and the desired pressure drop has to be specified on it as pressure.

    For the off-design calculation, it is again possible to choose between geometrical and phenomenological calculation, i.e. also in the case of geometrical design, the phenomenological
    off-design laws can be used. The reverse (geometrical off-design calculation in the case of phenomenological design) is possible as well, but it should not be of practical significance.
    The off-design behaviour is controlled via the flag FVOL.

    If an adaptation polynomial or a Kernel expression is used as correction for the pressure drop (FADAPT=-2 or 2), the calculated pressure drop will again be multiplied with the result of the polynomial and the Kernel expression respectively in off-design.

    In order to consider a pressure difference due to a geodetic height difference, it is to be entered as specification value GH. The pressure difference determined from this is additionally considered in each load case and output as result value. 

    So far, the arithmetic mean of the specific volume V1 at the inlet and V2 at the outlet has always been used to calculate the pressure difference based on the geodetic height. There is now the option of using either V1 or V2. The changeover takes place with the new switch FVOLGH. If the mean value is used and the specific volume at the outlet differs by a factor of 2 or more from that at the inlet, a warning is now issued.

     

    Convergence tuning (DPDPNMAX):

    To improve convergence, the pressure drop at components 2 (throttle) and 13 (pipe) can be limited to double to ten times the nominal value - even during iteration. The partial load factor DPDPN (see below) is used for this purpose.

    If this limitation remains until the end of the iteration, the component has obviously been designed at the wrong load point. In this case a warning is given. To improve convergence, the pressure drop of component 13 (pipe) can be limited by DPDPNMAX to double to ten times the nominal value.

    If the calculated pressure drop exceeds DPDPNMAX times the nominal value, it is limited to this value and a warning is issued. To avoid this, a different design point should be chosen for the component.

     

    Flag FERRP :

    In Release 12 and before, it was possible to  specify a negative pressure drop in this component or - in the mode "P2 given from outside" - to specify the outlet pressure higher than the inlet pressure without an error message being generated.
    This way, these components could also be used in special logical constructions.

    As, however, this is physically impossible in the normal use of the components, a flag FERRP has been implemented that allows to define whether in this case an error message, a warning, a comment or nothing at all is to be output. The default setting for FERRP is “Warning“, so that old models continue to calculate without error message.
    The user can then decide on a case-by-case basis whether to remove this warning or whether there really is an error.

     

    Limitation of enthalpy

    This component allows to specify a minimum value H2MIN for the enthalpy in order to prevent the enthalpy from drifting off during the iteration. Especially when specifying a constant power loss, it happened frequently that in the case of small mass flows, at the beginning of the iteration the enthalpy was often decreased down into the range of negative values or also across the phase boundary. This can be prevented by specifying a minimum enthalpy.

    Setting options for the geometrical pressure drop calculation

    In the geometrical calculation of pressure drops (FDP=1), the calculation was activated with the values of mass flow, pressure, and enthalpy at the component inlet. However, the calculation becomes more accurate when using the mean value of inlet and outlet conditions.

    This can be set via a flag FDPBASE:

    • FDPBASE =0: Calculation with the mean value of inlet and outlet conditions This is the default setting when inserting a new component.

    • FDPBASE =1: Calculation only with the inlet conditions This setting is used when loading a model created before Release 13 so that the results remain the same. It can also be 
                            used if convergence problems occur with FDP2PH=0.

    Please note: The solar components (113-115) already used the calculation with the mean of the inlet and outlet conditions.


    Logic inlet (Connection point 3) for controlling component properties

    (see also : Editing components  --> Ports)

    To make component properties like efficiencies or heat transfer coefficients (variation quantity) accessible from the outside (for control or reconciliation) it is possible to place the respective value on an auxiliary line as an indexed measured value (specification value FIND). In the component, the same index must then be entered as specification value IPS.

    It is also possible to place this value on a logic line that is directly connected to the component (please see FVALDP=2, Variation variable: DP12RN, dimension: Pressure).
    The advantage is that the allocation is graphically visible, and errors (e.g. when copying) are thus avoided.

     

    The activation of this logic line can also be made conditional on the mode of calculation. This way, this feature can also be used for designs without having to switch manually all the time.
    For this, the flag FVALDP features the settings

    This option is available for Components 2, 6, 8, 13, 18, 19, 23, 24, and 94.


    Constant Temperature Loss

    The setting options for thermal losses have been expanded by a mode “Constant temperature loss” (FDN=7). In contrast to FDN=2, in off-design no scaling of the temperature loss
    is carried out here. A correction by adaptation polynomial / Kernel expression, however, is possible here too.

     

    Heat Loss from Geometry

    The setting FDN=8 allows to have the heat loss in the pipe calculated from geometrical data.
    The following details are required for this:

    There is no specification of the thermal conductivity of the pipe as it is assumed that it is so high that the heat flow to the outside is not influenced by it (for an uninsulated pipe,
    the heat loss is thus determined by the heat transfer coefficients alone).

    A specification of the ambient temperature is required as well. It can either

           or

    Calculation of the heat loss from the geometry (FDN = 8) with the default value ALPHO:

    As before, it is possible to calculate the heat loss from the geometry of the external heat coefficient with the default value Calculate ALPHO:

     

    DQ = (TAV-TAMB) /

                       ( 1/(ALPHI*A_IN) +

                         1/(ALPHO*A_OUT) +

                         (1/(2*PI* LENGTH * LAMISO)) * LN(D_TOT/D_OUT) )

    with TAV=0.5*(T1+T2) (average temperature),

    DOUT=DINNER+2*THPIPE (outside diameter of the pipe),

    A_IN=PI* LENGTH *DINNER (inside surface of the pipe),

    A_OUT=PI* LENGTH *DOUT (outside surface of the pipe),

    D_TOT=DINNER+2*(THPIPE+THISO) (total diameter (pipe and insulation))


    Here the heat loss is limited in such a way that the outlet temperature cannot fall below the ambient temperature. If the inlet temperature is already smaller than the ambient temperature,
    the heat loss will be set to 0.

     

    Calculation of the heat loss from the geometry (FDN = 8) with a value according to VDI 2055:

    For the calculation of the heat loss, from Release 15 there is also the possibility to have the external heat coefficient calculated with a value according to VDI 2055 depending on the ambient temperature and the wind speed.

    It must be pointed out that in this component (other than in Component 118) there is no calculation of the temperature gradient in the pipe wall. The outer wall temperature included in the formulae for VDI 2055 is therefore equated with the fluid temperature here.

    The external heat transfer coefficient αk results from the heat transfer coefficient αk,free of the free convection in still air and the heat transfer coefficient αk,forc  of the forced convection according to

                αk = (αk,free4 + αk,forc4)1/4

    For the free convection, the following applies at laminar air flow:

    αk,free = 1.22 * (ΔT / dout)1/4  (in W/(m²K))

    with the temperature difference

    ΔT = Tav – Tamb = 0.5 * (T2+T1) - Tamb  (in K)

    and the outer diameter of the insulation

    dout = DINNER + 2 * THPIPE + 2 * THISO (in m)

    In the case of turbulent air flow, the following applies:

    αk,free = 1.21 * (ΔT)1/3  (in W/(m²K))

    Turbulent air flow sets in under the following condition

    critfree = dout 3 * ΔT > 1 m³K

     

    The forced convection depends on the wind speed vwind. The following condition is considered to be the criterion for the change from laminar to turbulent here:

    critforc = dout 3 * vwind > 0.00855 m2/s

     

    In the case of laminar flow, the following applies to the forced convection:

    αk,forc = 0.0081 / dout + 3.14 * (vwind/ dout)1/2  (in W/(m²K))

    and in the case of turbulent flow:

    αk,forc = 2* vwind + 3 * (vwind/ dout)1/2  (in W/(m²K))

     

    The values for the criteria, the contributions of the free and the forced convection to the external heat transfer coefficient as well as the calculated heat transfer coefficient are displayed as result values.

    Here the ambient temperature and wind speed can optionally be specified in the component or read from a sun or wind data component with the corresponding index ISUN and IWDATA respectively. This is set via the flags FSTAMB and FSVWIND respectively.

     

    Component 13 can be used on mechanical shafts and electric pipes as well to consider mechanical or electrical losses. This is useful for the modeling of a gear, e.g. The loss can be
    specified as enthalpy or power loss. Pressure and temperature losses do not make any sense in this case and lead to error messages.

    Electrical Resistor (electric lines)

    On electric streams, this component can also be used as electrical resistor. FDN=9 has to be set to do so. Then it is possible to specify

           and

    From this a complex alternating current resistance (impedance) is determined for

    Z = R + j*(ω*L – 1/(ω*C))        (j=imaginary unit)

       = |Z| * e j*Δφ

    with the apparent impedance |Z| and the phase difference Δφ.

    Assuming that the current I(t)=I0*e jωt remains constant, the voltage downstream of the resistor results in

                U2(t) = U1(t) - Z * I(t) = U1*e j(ωt+φ1) -  Z * I0*e jωt

    where φ 1 is the phase on the inlet line with which the voltage runs ahead of the current. As on the other hand

                U2(t) = U2*e j(ωt+φ2)

    shall apply, it is possible to calculate from this the amplitude U2 and the phase φ2 of the voltage on the outlet line:

                U2 = sqrt ((U1*cos(φ1)-|Z|*I0*cos(Δφ))2 + (U1*sin(φ1)-|Z|*I0*sin(Δφ))2)

                φ2 = arctan ((U1*sin(φ1)-|Z|*I0*sin(Δφ))/ (U1*cos(φ1)-|Z|*I0*cos(Δφ)))

    The electrical output (active power) on the outlet line then results in

                Q2 = U2 * I * cos(φ2)

     

    Phase calculation (electric lines)

    When using this component as electrical resistor (FDN=9) on electric lines, this component is also used for collecting information along a leg: resistances are added up against the flow direction, the (complex) current is passed on along the flow direction.
    As the change of the phase shift between current and voltage is calculated as well, all phase information is available both for the current and for the voltage.

    Note:

    For reasons of compatibility, Component 13 can still be operated on electric streams with the modes FDN=1, 4, or 7 for modeling a power loss (according to specification value DN).
    Since there only the enthalpy is decreased, this will lead to implausible values for current, voltage, and phase. The calculated output, however, is still correct.

     


    Note on the conversion of old models:

    In earlier Ebsilon versions, there was already the possibility to switch off the pressure drop calculation (P2 specification). However, this mode was located at FDP12RN, although it did not really fit in there concerning the content (FDP12RN specifies whether DP12RN is to be interpreted as absolute or relative). Therefore the feature P2 specification has been shifted to the
    level of FDP.
    When loading old models one might basically switch FDP12RN=-1 automatically to FDP=-1 now. However, problems will arise then if FDP12RN is used in scripts to switch the
    pressure specification. Therefore an automatic conversion has been refrained from, and the calculation kernel has been implemented in such a way that one can calculate with
    FDP12RN=-1 , although this variant is no longer displayed in the combo box. However, the user’s attention is drawn to this by means of a comment, so the user
    can switch the flags if required.

     

     

     

    User Input Values

    FMODE

    Flag for local calculation mode

    Like in Parent Profile (Sub profile option only)

    Expression

    = 0: GLOBAL

    = 1: Off-design mode

    = -1: Local Design mode

    FDN

    Flag for defining the thermal losses:

    Like in Parent Profile (Sub profile option only)

    Expression

    = 1: Specification as a heat loss (FDN=1): 
           The heat loss in the pipe is given by the specification value DN for all load cases. There is no scaling as a function of the mass flow.
           For small mass flows, that may result in a large reduction of the temperature which may cause an error. The heat loss can be used in the wet
           steam region, too. In this case, it causes a reduction of the steam content.       

    = 2: Specification as a temperature loss without phase transition (FDN=2): 
           In design case, the temperature loss is specified as specification value DN. In off-design, this value is scaled quadratically with the flow:

           DT = (M1/M1N)^2 * DTN

           If there would be a phase transition due to this temperature decrease,
           the temperature decrease is cut-off. The resulting temperature will be the boiling temperature. When there was superheated steam at the inlet,
           the outlet state is wet steam.   

           As in the same component, it is possible to specify a pressure loss as well, there may be a temperature loss due to the throttling. In this case,
           the component uses the bigger value of both losses. If it is desired that both losses should be considered, the pressure loss has to be
           modelled separately in a different component before or after this component.   

    = 4: Specification as enthalpy loss (FDN=4):
           The enthalpy loss of the pipe is given by the specification value DN for all load cases. There is no scaling with the mass flow. This mode can 
           be used in wet steam as well.

    = 5: Saturated water at outlet (FDN=5): :
           It is assumed that the loss is as high that the saturation line is matched exactly at the outlet. In this case, DN has no meaning.

    = 6: Relative heat/power loss (FDN=6): 
           The flag FDN also allows for the specification of a relative loss of heat and output, respectively.

    = 7: DN=constant temperature loss (no off-design scaling)

    = 8: Thermal loss calculated by geometry

    = 9: Voltage drop calculated by R, C and L (electric lines only)

    = -2: Temperature specification at outlet, T2 given (FDN=-2): 
             It is assumed that the loss is as high that a specified temperature is reached at the outlet. This temperature has to be specified externally (by a measurement
             point, e.g.), not within the component. The specification value DN is not used in this case.


    The option of a temperature loss without considering a possibly existing phase change (FDN=3) offered in earlier Ebsilon versions, is no longer available as it
    involves a high risk of faulty modeling. Old models using that mode, however, will continue to calculate.  

     

    DN

    Thermal loss according FDN (nominal)

    FDP

    Flag for switching between phenomenological and geometrical interpretation

    Like in Parent Profile (Sub profile option only)

    Expression

    = 0: phenomenological setting of the pressure loss DP12RN

    = 1: geometric calculation of the pressure loss in design of LENGTH, DINNER, ZS and ZETA (off-design according to FVOL)

    = -1: No calculation of the pressure drop (P2 externally given)

    FDP12RN

    Flag for setting DP12RN as absolute or relative value

    Like in Parent Profile (Sub profile option only)

    Expression

    = 1: DP12RN is used as absolute pressure drop in the design case and as absolute reference pressure drop for off-design calculations:  
           DP12N=DP12RN.
           The off-design pressure drop results according to Bernoulli’s principle for
           DP12= DP12N*(M1/M1N)^2*V1/V1N=DP12RN*(M1/M1N)^2*V1/V1N .
           This is the physically most sensible variant

    = 2: DP12RN is used in all load cases as the factor by which the current inlet pressure is multiplied to receive the pressure drop in the design
           case and
           the reference pressure drop for off-design respectively.
           The reference pressure drop for off-design calculations is thus variable:

           DP12N=P1*DP12RN. 

           The off-design pressure drop results for

           DP12=P1*DP12RN*(M1/M1N)^2*V1/V1N .

    = 3: DP12RN is only used in the design case as the factor by which the current inlet pressure is multiplied to receive the pressure drop. This pressure
           is then stored as reference inlet pressure P1N. In off-design, this reference inlet pressure is then multiplied by DP12RN to receive the reference
           pressure drop for off-design.
           The  reference pressure drop for off-design calculations is thus constant:

           DP12N=P1N*DP12RN.

           The off-design pressure drop results for

           DP12=P1N*DP12RN*(M1/M1N)^2*V1/V1N .

    = 4: DP12RN is used in all load cases as the factor by which the current inlet pressure is multiplied to directly receive the pressure drop in
           the respective  load case:

           DP12=P1*DP12RN 

           In this mode, Bernoulli’s principle is not used.

    DP12RN

    Pressure loss (nominal) [absolute or relative to P1]

    FDPBASE

    Base for geometric calculation of pressure drop

    Like in Parent Profile (Sub profile option only)

    Expression

    = 0: Based on average of inlet and outlet conditions

    = 1: Based on inlet conditions only

    GH

    Geodesic height

    >0: Pressure decrease

    <0: Pressure increase

    =0: no pressure change due to altitude difference

    FVOLGH

    Base for geometric calculation of pressure drop

    Like in Parent Profile (Sub profile option only)

    Expression

    = 0: Specific volume (mean value between inlet and outlet)

    = 1: Specific volume at the inlet

    = 2: Specific volume at the outlet

    ZETA

    Additional pressure loss zeta

    KS

    Pipe wall roughness

    WMAX

    Maximum permissible speed in the pipes (optional)

    Normal values:

    60 m/s for main steam

    80 m/s for bypass steam

    5 m/s for water

    The input affects only the minimum permissible pipe diameter and the cross-sectional area.

    Other values are not affected.

    LENGTH

    Pipe length

    DINNER

    Pipe inner diameter

    THPIPE

    Thickness of pipe wall

    THISO

    Thickness of insulation, may also be 0

    ALPHI

    Inner heat transfer coefficient (from the fluid to the pipe wall)

    ALPHO

    Outer heat transfer coefficient (to ambient)

    LAMISO

    Heat conductivity of insulation

    FSTAMB

    Definition of ambient temperature

    TAMB

    Ambient temperature

    FSWIND

    Definition of wind speed

    WIND

    Wind speed

    ISUN

    Index of solar parameters

    IWDATA

    Index for wind parameters

    FVOL

    Flag for the off-design behaviour of the pressure dropLike in Parent ProfileLike in Parent Profile: Setting of the flag is taken over from the superordinate profile (this setting
    is only available in sub profiles)

    Like in Parent Profile: Setting of the flag is taken over from the superordinate profile (this setting is only available in sub profiles)

    Expression:

    A formula can be entered ( in EbsScript syntax ) that is evaluated before the start of the calculation. Depending on whether this formula yields the value 0, 1, 2 or 3, the corresponding setting of the flag will be used.

    = 0: The pressure drop only depends on the mass flow. This approximation applies to incompressible fluids (usually liquids) as for them, the specific 
            volume remains constant.

            Thus you spare yourself the call of the physical properties function for the specific volume.

            In this case, the off-design factor for the pressure drop is simply

            DPDPN = (M1/M1N)**2

    =1: The pressure drop is calculated according to Bernoulli’s principle and also considers the compressibility of the fluid. Therefore it is suitable for all 
          fluids (both gases and liquids). For this reason, it is the default setting. The off-design factor for the pressure drop is in this case

          DPDPN = (V1/V1N)*(M1/M1N)**2

    =2: The pressure drop is assumed to be constant, i.e. it does not depend on the load. This variant is only intended for special constructions. In this  
          case, the off-design factor for the pressure drop is simply

          DPDPN = 1

    =3: Also in off-design, the pressure drop is calculated directly from the pipe geometry, and not via a scaling of the design case. At this point, no off-  
          design factor is thus calculated. The result value DPDPN is only determined subsequently as quotient from the pressure drop calculated in off-
          design to the design pressure drop.

     

    FVALDP

    Flag for the off-design behaviour of the pressure drop

    Like in Parent Profile (Sub profile option only)

    Expression

    = 0: Default value used DP12RN, without validation

    = 1: (Deprecated) Instead DP12RN designated by IPS pseudo tag is used (validable)

    = 2: DP12RN given by pressure on control inlet 3 (pressure)

    = 4: Pressure on control inlet 3 used in design, specification value DP12RN in off-design

    = 5: Specification value DP12RN used in design, Pressure on control inlet 3 in off-design

    This switch is used in particular to enable a validation of the pressure drop (for FVALDP> 0), but also allows for control from the outside,
    in certain constructions.

    IPS

    Index for at FVALDP = 1 used pseudo measurement point

    R

    Ohmic resistance (electric lines)

    C

    Capacitance (electric lines)

    L

    Inductivity (electric lines)

    H2MIN

    Restriction of enthalpy on outlet to values higher than

    DPDPNMAX

    Suppress high off-design pressure losses

    Like in Parent Profile (Sub profile option only)

    Expression

    Strong limitation: 2
    Moderate limitation: 10

    (Restrict off-design factor for pressure loss to (input) Value> = 1: see above under "General"; (A value <1 will give a warning! A value <1 would mean that you can not reproduce the design data in off-design mode.))

    FADAPT

    Flag for adaption polynomial / adaption function

    Like in Parent Profile (Sub profile option only)

    Expression

    = 0: Polynomial is not used

    = 1: Correction of the heat or temperature loss:

                  for FDN = 1 : DQ12 = DN * polynomial (no partial-load factor!)

                  for FDN = 2 : DT12 = DN * (M1/M1N)^2 * polynomial

                  for FDN = 4 : DH12 = DN * polynomial

                  for FDN = 5 : the polynomial is not considered

                  for FDN = 6 : DH12 = DN * H1 * polynomial

    = 2: Correction of the pressure loss

                  for FDP12RN = 1 : DP12 = DP12RN * partial-load factor * polynomial

                  for FDP12RN = 2 : DP12 = DP12RN * P1 * partial-load factor * polynomial

                  for FDP12RN = 3 : DP12 = DP12RN * P1N * partial-load factor * polynomial

                  for FDP12RN = 4 : DP12 = DP12RN * P1 * polynomial

    = 3: Replace heat or temperature loss:

                  for FDN = 1 : DQ12 = DN * polynomial

                  for FDN = 2 : DT12 = DN * polynomial

                  for FDN = 4 : DH12 = DN * polynomial

                  for FDN = 5 : the polynomial is not considered

                  for FDN = 6 : DH12 = DN H1 * polynomial

    =4: Replace the pressure loss

                  for FDP12RN = 1 : DP12 = DP12RN * polynomial

                  for FDP12RN = 2 : DP12 = DP12RN * P1 * polynomial

                  for FDP12RN = 3 : DP12 = DP12RN * P1N * polynomial

                  for FDP12RN = 4 : DP12 = DP12RN * P1 * polynomial

    = 1000: Not used but ADAPT evaluated as RADAPT (Reduction of the computing time)

    = -1: Correction of the heat or temperature loss:

                   for FDN = 1 : DQ12 = DN * adaption function (no partial-load factor!)

                   for FDN = 2 : DT12 = DN * (M1/M1N)^2 * adaption function

                   for FDN = 4 : DH12 = DN * adaption function

                   for FDN = 5 : the adaption function n is not considered

                   for FDN = 6 : DH12 = DN * H1 * adaption function

    = -2: Correction of the pressure loss

                    for FDP12RN = 1 : DP12 = DP12RN * partial-load factor * adaption function

                    for FDP12RN = 2 : DP12 = DP12RN * P1 * partial-load factor * adaption function

                    for FDP12RN = 3 : DP12 = DP12RN P1N * partial-load factor * adaption function

                    for FDP12RN = 4 : DP12 = DP12RN * P1 * adaption function

    = -3: Replace heat or temperature loss:

                    for FDN = 1 : DQ12 = DN * adaption function

                    for FDN = 2 : DT12 = DN * adaption function

                   for FDN = 4 : DH12 = DN * adaption function

                   for FDN = 5 : the adaption function is not considered

                   for FDN = 6 : DH12 = DN * H1 * adaption function

    = -4: Replace the pressure loss

                   for FDP12RN = 1 : DP12 = DP12RN * adaption function

                   for FDP12RN = 2 : DP12 = DP12RN * P1 * adaption function

                   for FDP12RN = 3 : DP12 = DP12RN * P1N * adaption function

                   for FDP12RN = 4 : DP12 = DP12RN * P1 * adaption function

    = -1000: Not used but EADAPT evaluated as RADAPT (Reduction of the computing time)

     

    EADAPT

    Adaptation function (input)
    function evalexpr:REAL;
    begin
    evalexpr:=1.0;
    end;

    FERRP

    Notification if P2 > P1

    Like in Parent Profile (Sub profile option only)

    Expression

    =0: No notification
    =1: Comment
    =2: Warning
    =3: Error

    M1N        

    Mass flow (nominal)

    V1N         

    Specific volume at inlet  (nominal)

    H1N         

    Inlet enthalpy (nominal)

    H2N         

    Outlet enthalpy (nominal)

    T2N         

    Outlet temperature (nominal)

    P1N         

    Inlet pressure  (nominal)

    DP12N         

    Pressure drop  (nominal)

    The parameters marked in blue are reference quantities for the off-design mode. The actual off-design values refer to these quantities in the equations used.
             

    Generally, all inputs that are visible are required. But, often default values are provided.

    For more information on colour of the input fields and their descriptions see Edit Component\Specification values

    For more information on design vs. off-design and nominal values see General\Accept Nominal values 

     

    Result values:

    Heat loss:

    DQ

    Heat loss

    Pressure Drop:

    DP

    Total pressure loss DP= DPB +DPZETA + DPGEOD 

    DPB

    Basic pressure drop that results from the pipe friction. Depending on the setting of the flags FDP and FVOL, it will be calculated from the pipe geometry or from phenomenological design values, if necessary scaled with an off-design factorBasic pressure drop that results from the pipe friction. Depending on the setting of the flags FDP and FVOL, it will be calculated from the pipe geometry or from phenomenological design values, if necessary scaled with an off-design factor.Basic pressure drop that results from the pipe friction. Depending on the setting of the flags FDP and FVOL, it will be calculated from the pipe geometry or from phenomenological design values, if necessary scaled with an off-design factor.   Basic pressure drop that results from the pipe friction. Depending on the setting of the flags FDP and FVOL, it will be calculated from the pipe geometry or from phenomenological design values, if necessary scaled with an off-design factor Basic pressure drop that results from the pipe friction. Depending on the setting of the flags FDP and FVOL, it will be calculated from the pipe geometry or from phenomenological design values, if necessary scaled with an off-design factor

    DPZETA

    Additional pressure drop (from ZETA), e.g. due to installed equipment like fittings

    DPZETA=0.5 * 10-5 * ZETA * w**2 / v

    Here

    w is the flow rate and
    v is the specific volume 

    at a notional “mean“ point in the pipe whose condition results from the physical properties with the mean value between inlet and outlet pressure and the mean value between inlet and outlet enthalpy. The factor 10-5 arises from the unit conversion from Pascal to bar.

    DPGEOD

    Pressure difference resulting from the gravitational force due to the geodesic difference in altitude GH. This contribution can be positive or negative depending on whether the inlet or the outlet of the pipe is at a higher level.

    DP12NR

    Applied value for the nominal pressure drop

    DPREF

    Reference pressure drop

    DPPDN

    Off-design factor for pressure drop

    Other results:

    AMIN

    Minimum cross section of the pipe

    DIAMIN

    Minimum inner diameter of the pipe

    ACALC

    Calculated cross section

    WCALC

    Calculated flow rate

    RADAPT

    Result for ADAPT / EDAPT

    Electrical results:

    When using the component as an electrical resistor (FDN=9) on electric lines, there are the following result values:

    RR

    Calculated resistance (ohmic resistance) R

    RX

    Calculated reactive part of impedance (reactance) X

    RZ

    Calculated apparent resistance (impedance) Z

    RDPHI

    Electrical phase displacement

    Off-design:

    M1M1N

    Related mass flow (M1/M1N)

    V1V1N

    Relative specific volume (V1/V1N)

    P1P1N

    Related inlet pressure (P1/P1N)

     

    Physics used

    Equations

     
     

    if GLOBAL = Design and FMODE = Design, then {

        if FDP = 1, then DP12N = DP12RN

        if FDP = 2, then DP12N = DP12RN*P1

        }

    M1R = M1/M1N

    if GLOBAL = Design and FMODE = Design, then {

    M1R= 1.0     }

    if FVOL = without, then  F = (M1R ** 2)

    if FVOL = with, then F = (M1R ** 2) * (V1/V1N)

    if GLOBAL = Design and FMODE = Design, then {

    F= 1.0  }

    ZW  = 1./(.5*(V1+V2))*9.81*GH*1.E-5

    DP12  = DP12N * F + ZW

    P2  = P1 – DP12                                         

    M2  = M1                                             

    NCV2 = NCV1

    for FDN = heat loss:

    Q2 = Q1 - DN

    H2 = Q2/D2                                         

    T2 = f(P2,H2)

    for FDN = Enthalpy loss:

    H2 = H1 - DN                                        

    Q2 = H2*M2

    T2 = f(P2,H2)

    for FDN = Temperature loss:

    T2 = T1 - DN

    Q2 = H2 * M2

    H2 = f(P2,T2)                                      

    if H2 <= H"(P2), then H2=H"(P2)

    If FDN = Temperature loss (superheated steam -> saturated steam) {

    Design case:

    T2=T1-DN

    Q2=H2*M2

    H2=f(P2,T2)

    if H2 <= H"(P2), then H2=H"(P2)

    Off-design case:

    DH = T2/T2N * M1N/M1 * (H1N-H2N)

    H2=H1-DH

    if H2 <= H"(P2), then H2=H"(P2)

    T2 = f(P2,H2)

     }

    Vmax=MAXIMUM(V1,V2)

    AMIN=Vmax*M1/WMAX

    DIAMIN=2*SQRT(AMIN/PI)

    		  

    Component Displays

    Display Option 1

    Example

    Click here >> Component 13 Demo << to load an example.

    See Also
    Throttles and Valves

     

     

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