Calculation of pure substance / multicomponent mixture condensers
with / without inert gases
– requires MS Access –
Types of construction
- Tube bundle construction with plain tubes
- vertical / horizontal
- Direct current / counter current
- Tube-side / Shell-side condensation
- superheated inflow / supercooled outflow
- Pure substance / multi-component mixtures with / without inert gases
Graphical output of the calculation results
- Temperature curve of steam, condensate and coolant
- Condensate mass flow
- Pressure curve on the condensation side
- Change of steam content and steam velocity
Example of a temperature curve
Construction
- Calculation of design-compatible tube sheets
- Tubesheet database
- CAD interface
Scientific basis
- Local description of condensation by cell method.
- Calculation of material and energy transport according to VDI Heat Atlas 10th edition chapter Jbb for multi-component mixtures or according to the “Resistance Proration” method based on the “Heat Curve”.
- Single-phase heat transfers according to VDI Heat Atlas
- LV properties generator PROPER with phase equilibrium calculation (DDB Flash) according to Prof. Gmehling
including PROPER and phase equilibrium calculation (DDB Flash)
You save 1380 EUR or even more if PROPER is already available. Ask for a special price.
Program structure of the MESK module
The program works according to the cell method, i.e. the apparatus is incrementally discretized into cells in such a way that the local description of the condensation process is sufficiently accurate. For each cell, the equations are solved iteratively.
They describe the relationships between the core flow of the vapour, the diffusion and equilibrium conditions in the diffusion boundary layer (including the heat and mass transfer), the condensate film and the heat transfer to the coolant as well as the mass and energy balance.
Partial results of a cell (balance data and thermal data) from MESK
| Vapor |
Film |
Alpha |
| T |
Mpkt |
P |
V |
Re |
T |
Mpkt |
Re |
Gas Film |
Total |
| 406,5 |
0,374 |
9982,9 |
1,372 |
-1 |
309,2 |
3,677 |
-1 |
0,0030 |
93,08 |
| 406,5 |
0,411 |
9982,9 |
1,502 |
4589,9 |
313,8 |
7,664 |
0,6 |
0,0043 |
100,27 |
| 406,5 |
0,451 |
9982,9 |
1,643 |
5034,1 |
315,9 |
0,119 |
1,3 |
0,0061 |
108,47 |
| 406,5 |
0,494 |
9982,9 |
1,794 |
5513,9 |
317,8 |
0,166 |
2,2 |
0,0083 |
117,46 |
| 406,5 |
0,540 |
9982,9 |
1,959 |
6032,5 |
319,6 |
0,216 |
3,1 |
0,0109 |
127,34 |
| 406,5 |
0,591 |
9983,0 |
2,136 |
6593,0 |
321,4 |
0,270 |
4,2 |
0,0141 |
138,19 |
| 406,5 |
0,645 |
9983,0 |
2,328 |
7199,0 |
323,2 |
0,329 |
5,4 |
0,0178 |
150,12 |
| 406,5 |
0,704 |
9983,0 |
2,535 |
7854,6 |
325,0 |
0,393 |
6,8 |
0,0200 |
163,33 |
| 406,5 |
0,768 |
9983,1 |
2,760 |
8564,1 |
326,7 |
0,462 |
8,3 |
0,0266 |
177,97 |
| 406,6 |
0,836 |
9983,1 |
3,003 |
9332,4 |
328,4 |
0,536 |
10,0 |
0,0318 |
194,27 |
| 406,6 |
0,911 |
9983,2 |
3,266 |
10164,0 |
330,1 |
0,617 |
11,8 |
0,0352 |
212,21 |
| 406,6 |
0,992 |
9983,3 |
3,551 |
11062,0 |
331,6 |
0,704 |
13,9 |
0,0356 |
231,72 |
| 406,6 |
1,079 |
9983,3 |
3,858 |
12032,0 |
333,1 |
0,798 |
16,2 |
0,0360 |
253,08 |
| 406,6 |
1,173 |
9983,4 |
4,189 |
13078,0 |
334,5 |
0,899 |
18,7 |
0,0363 |
276,55 |
| 406,6 |
1,274 |
9983,6 |
4,545 |
14205,0 |
335,9 |
1,009 |
21,5 |
0,0367 |
302,39 |
| 406,6 |
1,383 |
9983,7 |
4,929 |
15417,3 |
337,2 |
1,126 |
24,4 |
0,0370 |
330,89 |
| 406,6 |
1,501 |
9983,8 |
5,341 |
16720,7 |
338,5 |
1,253 |
27,7 |
0,0373 |
362,40 |
| 406,6 |
1,627 |
9984,0 |
5,784 |
18121,1 |
339,7 |
1,389 |
31,3 |
0,0375 |
397,31 |
The program MESK is used for thermal and hydraulic design and / or simulation of shell and tube condensers with plain tubes.
The condensing medium can be either a pure substance or a multi-component mixture with or without inert gas content. In addition to the condensation process (basis: VDI-Wärmeatlas10. Edition Chapter Jbb), the program also takes into account the heating of the steam up to the dew point temperature as well as a possible subcooling of the condensate. When using the “Resistance Proration” method on the basis of a heat curve, the calculation is limited to the condensation, the heating of the steam or the subcooling of the condensate is not taken into account.
The condensation can take place in the tubes or in the shell. In the design, a distinction is made between horizontal and vertical devices, whereby with vertical condensers the steam and the outflowing condensate can be guided in a direct current or in a counter current.
Design-compatible tube sheet
The program contains the SPIE module developed by LV, which automatically generates a design-compatible tube sheet for the calculation by specifying only a few boundary conditions. This tube sheet can be saved in a tube sheet library and passed on as a DXF file to various CAD programs.
Condensation
Condensation occurs when the temperature of the cooling wall is lower than the dew point temperature of the steam. In the case of a pure substance, condensation is controlled by heat transfer, i.e. the vapour flow from the core of the flow to the phase boundary is only determined by the thermal resistance in the condensate film. The driving force for the condensation process results from the difference between the dew point temperature of the steam and the wall temperature. In the case of mixtures, the facts are much more complex. If the temperature falls below the dew point temperature, the heavier volatile components on the cooling surface condense preferentially in a mixture. Therefore, the steam has a different composition at the phase boundary than at the core of the flow.
The more volatile components accumulate at the phase interface. This accumulation represents an additional material transport resistance for the material flows diffusing to the phase boundary (diffusion boundary layer) and lowers the temperature at the phase boundary. The phase boundary temperature also determines the heat transport through the condensate film and thus the entire condensation process.
Inert gases have a great influence on the condensation speed and thus on the condensation performance, as they permanently hinder the material flow of the condensing vapours during the condensation process and reduce the condensation performance (diffusion-controlled).
When calculating the condensation of vapour mixtures, the additional resistances for mass and energy transport must therefore be taken into account.
For this purpose, the program uses the approaches in chapter Jbb of the VDI Heat Atlas 10th Edition, which combines these diffusion processes and the local equilibrium conditions into a mathematical procedure and makes them accessible to an iterative solution.
In addition to the method described in the chapter, the MESK program also contains a further solution based on the “Resistance Proration” method. This method assumes that the steam temperature profile can be approximately represented by the equilibrium condition. The basis is the “heat curve”, with the help of which the condensation process can be described using empirical corrections.
The condenser can only be calculated within the temperature range specified in the heat curve, which is limited by the thawing and boiling temperature of the vapour mixture. A de-heating of the steam to dew temperature or a subcooling of the condensate is not considered.
The “heat curve” can either be entered by the user or calculated with the PROPER properties generator.
Single phase heat transfer
The single-phase heat transfer during the heating of the steam and subcooling of the condensate as well as for the coolant is calculated according to the approaches of the VDI Heat Atlas.
LV properties generator PROPER with DDB phase equilibrium calculation
The material values of steam and condensate, which are dependent on temperature, pressure and composition, are constantly recalculated and updated during the calculation by the PROPER material value generator integrated in the program. For the calculation of the phase equilibrium PROPER uses the phase equilibrium program of the Dortmunder Datenbank / Prof. Gmehling (DDB).
Comparative calculations for the multi-component mixture condenser:
see also:
Dieser Beitrag ist auch verfügbar auf:
Deutsch (German)