NusseltPipe2ph L2
Created Wednesday 05 June 2013
Heat transfer model based on Nusselt Number for two-phase and one-phase pipe flow. Takes Geometry data, flow data and media data into account
1. Purpose of Model
A detailed model that takes all relevant dependencies into account. This model is numerically less robust than other models, e.g. HeatTransport:Generic HT:CharLine L2 since it takes fluid states and flow regimes into account. Phase change is supported. It has to be defined via parameter which change mechanism (e.g. boiling in horizontal pipe) is taken into account.
2. Level of Detail and Physical Effects Considered
2.1 Level of Detail
Referring to Brunnemann et al. [1], this model refers to the level of detail L2 because the system is modeled with the use of balance equations, which are spatially averaged over the component.
2.2 Physical Effects Considered
- dependencies of the heat transfer coefficient on the Reynolds Number
- dependencies of the heat transfer coefficient on the Prandtl Number
- reverse flow
- flow regime change
- boiling in horizontal pipe, boiling in vertical pipe, condensation in horizontal pipe
- the convective and the nucleate boiling mechanism are considered
3. Limits of Validity
- see FluidDissipation documentation for limits of the used equations
4. Interfaces
The model communicates via outer models and records. Thus its expects to have:
- an outer model named geo as defined Fundamentals:Geometry:GenericGeometry
- an outer record named iCom as defined in Basics:Records:IComBase L2
- an inCon record required for communication with FluidDissipation functions
- an inVar record required for communication with FluidDissipation functions
5. Nomenclature
6. Governing Equations
The mean temperature difference is defined as follows, based on the user's choice in the boolean parameter temperatureDifference:
Please note that for the choice temperatureDifference="Logarithmic mean" a number of means is applied to make the equation regular also for zero heat flow and reversing heat flows. If an unsupported string for temperatureDifference is provided an assert would raise.
With equation (3) the FluidDissipation function FluidDissipation.HeatTransfer.StraightPipe.kc_overall is called. The necessary media, flow and geometric data is handed over via the records inCon and inVar.
With Eq. (4) the FluidDissipation function FluidDissipation.HeatTransfer.StraightPipe.kc_twoPhaseOverall_KC is called. See FluidDissipation for documentation of the used equations for calculation of the Nusselt number and the heat transfer coefficient 
. The Stepsmoother is used to smooth between 
and 
at the phase boundaries. Thus, the total heat transfer coefficient 
is received.
7. Remarks for Usage
If the computing efford has to be reduced or the model can be made responsible for numerical unstable behavior, use this model to tune simpler and numerically stable models, e.g. HeatTransport:Generic HT:CharLine L2.
8. Validation
see FluidDissipation documentation
9. References
[1] Johannes Brunnemann and Friedrich Gottelt, Kai Wellner, Ala Renz, André Thüring, Volker Röder, Christoph Hasenbein, Christian Schulze, Gerhard Schmitz, Jörg Eiden: "Status of ClaRaCCS: Modelling and Simulationof Coal-Fired Power Plants with CO2 capture", 9th Modelica Conference, Munich, Germany, 2012
10. Authorship and Copyright Statement for original (initial) Contribution
Author:
DYNCAP/DYNSTART development team, Copyright 2011 - 2022.
Remarks:
This component was developed during DYNCAP/DYNSTART projects.
Acknowledgements:
ClaRa originated from the collaborative research projects DYNCAP and DYNSTART. Both research projects were supported by the German Federal Ministry for Economic Affairs and Energy (FKZ 03ET2009 and FKZ 03ET7060).
CLA:
The author(s) have agreed to ClaRa CLA, version 1.0. See https://claralib.com/pdf/CLA.pdf
By agreeing to ClaRa CLA, version 1.0 the author has granted the ClaRa development team a permanent right to use and modify his initial contribution as well as to publish it or its modified versions under the 3-clause BSD License.
11. Version History
- 2012 - v 0.1 -initial implementation - Ala Renz, Friedrich Gottelt, XRG-Simulation
Backlinks: ClaRa:Components:HeatExchangers:HEXvle2gas L3 2ph BU simple ClaRa:Components:HeatExchangers:TubeBundle L2 ClaRa:Basics:ControlVolumes:FluidVolumes:VolumeVLE L2