Component 91: Steam Generator - Auxiliary Heating Surface

Specifications

 

General       User Input Values       Characteristic Lines       Physics Used       Displays       Example

 

General

Together with components 89 (steam generator, main heating surface) and 88 (steam generator, flue gas zone), component 91 allows the representation of membrane pipe walls or supporting tubes in the area of a bundle heating surface that are usually integrated into the water/steam model in another place than the bundle. Apart from water/steam, however, thermal oil, two-phase fluid, and universal fluid are supported as primary fluid as well.

Module 91 only represents the primary side of an auxiliary heating surface. Therefore, use of this component, without component 88 representing the flue gas side (at PIN 3, connected to PIN 4 or 5 of flue gas zone 88) or without a corresponding main heating surface 89 (at PIN 4, connected to PIN 6 or 7 of main heating surface 89) will lead to errors.

 

Pressure drop limitations in off-design (Extras --> Model Options--> Calculation -->Relative pressure-drop maximum) :
As the pressure drop rises quadratically with the mass flow, pressure drops that are significantly too high can quickly arise in the event of a transgression of the nominal mass flow. These will then cause phase transitions and convergence problems. For this reason, pressure drop limitations have been installed.

 

Pinch point violation :
In case of a pinch point violation KA is nowOne can now position it and change its name and description. This description also appears as text on the macro display. reduced automatically (like for other heat exchangers) to avoid the pinch point violation. A warning is issued in this case.

 

 

MODEL:

Like other heat exchanges, the calculation model is based on the fundamental equations for the mass flow, pressure and enthalpy

-  (1)      M1 =  M2

-  (2)      P1 = P2 + DP12

-  (3)     (k*A)*LMTD = M2*H2 - M1*H1

with the indices

- 1 for the primary inlet

- 2 for the primary outlet

For calculating the mean logarithmic temperature difference LMTD, the flue gas inlet and outlet temperatures of the components 88 or 90, connected via the logic line 3, are used. for this reason, component 89 is fully functional, only when line 3 is connected to component 88 (PIN 4 or 5).

It is assumed for mass flow and pressure, that M1 / M2  or P1 / P2 respectively are given at  the connected lines. In each case, the missing value is calculated.

CALCULATION RULES:

It is assumed that the heat transfer coefficient of an auxiliary heating surface is determined by the flow conditions and geometry of the main heating surface. Thus, the heat transfer coefficient is taken from the attached component 89,  whereby the k-value of the main heating surface is modified with a correction factor CORR

 -  (4)   kauxiliary= CORR * kmain

The calculation rules to evaluate the heat transfer coefficient are described  in detail in component 89.

COMPONENT IDENTIFICATION

The identification of component 91 is defined as the calculation of CORR from (3) and (4), whereby one temperature on the flue gas side as well as in- and outlet temperature on the water/steam side must be known.

Taking over CORR for the Auxiliary Heating Surface 

Like in many other components, when using the identification mode in the design case the result value is automatically transferred to the specification value too.
For this component it is the result value RED that is transferred to the specification value CORR.

 

A common identification of an auxiliary heating surface, component 91 in a group with other heating surfaces, as in the case of main heating surface, component 89, is currently not implemented.

User Input Values 

 

The identification value marked in blue is the reference value for the off-design mode. The actual off-design values refer to the values used in the equations.

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

 

It can be seen from the following table, whether CORR or T2 is to be specified:
 

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Characteristic Lines

No characteristic lines are used.

Physics Used

Equations

 

 

  

 

Component Displays

Display Option 1

Example

Click here >>Component_91 Demo<< to load an example.