HEXvle2gas L3 1ph BU ntu

Created Friday 01 November 2013


A block-shaped steam to air preheater model with flue gas at shell side and steam/water medium at the tube side, NTU-based heat transfer calculation. A block-geometry for low pressure air preheaters with U-type tube bundles is assumed.

1. Purpose of Model


This model is well suited to model slow transients of commonly designed low pressure air preheaters. 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

intrinsic ideally mixed gas flow.

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


Usage with finned heat transfer models:


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.

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 flowOrientation to geometry
- rename parameter mainOrientation in flowOrientation
- remove parameter verticalTubes which is without any effect
- quadruple port m_flow was taken from shell side instead of tube side
- propagated parameters staggeredAlignment, N_rows, Delta_z_par, Delta_z_ort
- corrected calculation of A_heat: previous versions used lateral shell surface instead of tube bundle lateral surface
- changed default values of z_in_shell and z_out_shell, to avoid newly introduced asserts (e.g. z_in_shell>max height). Furthermore, the new values are in consonance with the default flow orientation.
- T.Hoppe, F.Gottelt, XRG Simulation
- bugfixed underlying NTU wall model
- new heat transfer models can be chosen
- correct heat transfer area for finned tube heat transfer is used automatically
- introduced parameter tubeOrientation, models are parametrisable in a more flexible way - Timm Hoppe and Annika Kuhlmann, XRG Simulation GmbH, Lasse Nielsen TLK Thermo GmbH