HEXvle2vle L3 1ph BU ntu

Created Monday 10 June 2013

A block-shaped desuperheater model with an U-type tube bundle. Heat resistance is calculated by NTU-method.

1. Purpose of Model


This model is well suited to model slow transients of commonly designed desuperheaters where no phase change happens. If large-scale short-term transients occur, e.g. as can be found during start-up the model might give imprecise results since the basic assumptions of the NTU approach (applied for calculation of heat resistance) can be violated.

2. Level of Detail, Physical Effects Considered and Physical Insight


2.1 Level of Detail

Referring to Brunnemann et al. [1], this model refers to the level of detail L3 because the system is modelled with the use of balance equations applied to two different zones of the component: liquid condensate at tube side, vapour volume at shell side.

2.2 Physical Effects Considered

2.3 Level of Insight


Heat Transfer


shell side

tube side:

Pressure Loss


shell side


tubes side

Phase Separation


shell side

Basics:ControlVolumes:Fundamentals:SpatialDistributionAspects:IdeallyStirred : ideally mixed phases, no phase separation

tube side:

Basics:ControlVolumes:Fundamentals:SpatialDistributionAspects:IdeallyStirred : ideally mixed phases


Heat Exchanger Type



3. Limits of Validity

4. Interfaces


5. Nomenclature

- no model specific nomenclature -

6. Governing Equations


6.1 System Description and General model approach


This model is composed by instantiation of the following classes:

6.2 General Model Equations


Summary

A record summarising the most important variables is provided. Please be aware of the boolean showExpertSummary in the parameter dialog tab "Summary and Visualisation". Setting this parameter to true will give you more detailed information on the components behaviour. The summary consists of the outline:

and the summaries of the class instances named in section 6.1

7. Remarks for Usage


7.1 Naming

The naming of heat exchangers in this package follows some specific form that is defined as follows:

7.2 Heat Transfer Modelling

In most cases the heat transfer from one fluid to the other will be dominated by the heat transfer at one of fluid boundary layers. In that cases the heat transfer coefficient α at this side will be considerably smaller than on the other side. From a numerical point of view it is disadvantageous to have very high (close to infinite) heat transfer coefficients on either sides. If you want to take nearly ideal heat transfer at one of the sides into account please consider the corresponding replaceable model instead of defining arbitrary large heat transfer coefficients in the model.

7.3 Phase Change

Since the model has only one state on the tube side and the shell side respectively phase change is in principally possible but will result in low accuracy during the phase change transients. Furthermore, phase separation is not supported. To model phase change and separation on the shell side consider Components:HeatExchangers:HEXvle2vle L3 2ph BU ntu.

8. Validation


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 Simulation of 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

- propagated tube bundle vertical and horizontal spacing
- T.Hoppe, F.Gottelt, XRG Simulation
- bugfixed underlying NTU wall model
- introduced parameter tubeOrientation, models are parametrisable in a more flexible way - Timm Hoppe and Annika Kuhlmann, XRG Simulation GmbH, Lasse Nielsen TLK Thermo GmbH