Multi-component condenser (MESK)
Design of CONDENSERS for pure-component and multi-component mixtures with and without inert gas
MESK is a program for the thermal and hydraulic design of tube bundle type condensers with either bare or finned tubes or plate type condensers. The condensing medium may be a pure component, or a mixture with or without inert components. The thermal design also covers vapor superheating of vapor and subcooling of condensate. The condensation may be tube or shell side, in horizontal or vertical units, and co-current or countercurrent.
Condensation is initiated by a temperature difference between the tube wall and the dew point of the condensing stream. In case of a pure component, the condensation process is controlled by the heat transfer process. In this regime the vapor flow at the phase boundary is controlled by the heat transfer resistance of the condensate film. The driving force is the temperature difference between the dew point of the vapor and the wall.
In case of mixtures, things are more complicated. When the dew point is reached, the less volatile components of the mixture will condense first, and so the vapor near the boundary layer (or film) will have a composition different from that of the vapor in midstream. Due to this process the concentrations of the more volatile components near the film will rise. This enrichment is an additional resistance for the mass transfer of the components diffusing to the boundary layer, and will drop the temperature of the boundary layer. This temperature controls the heat transfer of the condensate film and thus the total condensation process.
Inert or non-condensable components have a great impact on the condensation duty due to their permanent resistance for the condensing component stream.
For the condenser design, both heat and mass transfer must be considered. The MESK program is based on Chapter Jbb of the LV Heat Atlas. Here a mathematical procedure is given which covers the diffusion process and the local equilibrium conditions in one model.
In addition a second thermodynamic method, known as resistance proration is available in the program. This method is based on a linear approximation of the vapor-temperature profile by the phase equilibrium conditions. The condensation process is described by the "heat curve" and empirical corrections. The heat curve may be given by the user or generated by the LV property generator PROPER.
Single-phase heat transfer
The superheated and sub-cooled regions as well as the cooling medium are calculated by the LV Heat Atlas correlations.
The required stream properties for the specific temperature, pressure, and composition conditions during run time are calculated by the integrated PROPER program. The phase equilibrium calculation is based on the PSRK method developed by Prof. Gmehling and uses the DDBST (Dortmunder Datenbank).
MESK is a finite element program. The exchanger is divided into as many incremental cells as required for an accurate description of the heat transfer process. For each cell all thermodynamic correlations as well as the heat and material balance are applied. By an interactive process both the condensing stream and the cooling medium heat and material balances are solved.
The quality of a solution also depends on the geometric data which should be entered as built during the calculation step. The most important detail is the tube bundle which is defined in the tube sheet design. MESK has the capability to generate construction details such as tube sheets.
These tube sheets are stored in a special library accessible to all LV programs and commonly used CAD programs.
includes PROPER and Phase Equilibrium Generator (DDB-Flash)
Available in German only!
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