Development and evaluation of a calculation tool for prediction of condensation behaviour in vertical tubes in the presence of non-condensable components
Lopez Corzo, Edward Felipe (2020)
Diplomityö
Lopez Corzo, Edward Felipe
2020
School of Energy Systems, Energiatekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2020112795786
https://urn.fi/URN:NBN:fi-fe2020112795786
Tiivistelmä
Evaporation and condensation are central heat transfer processes in many applications of the process industry. In most cases, condensation takes place by indirect heat transfer, i.e. the vapour and the cooling medium are separated from each other by a wall. Horizontal shell and tube heat exchanger are often used as condensers, in which the vapour flows on the shell side and the cooling water on the tube side. In special applications, this can be reversed: the vapour is condensed in a vertical tube bundle, the coolant flows on the shell side. The latter setup is especially beneficial for corrosive or harmful chemicals due to better cleaning options in vertical tubes. Vacuum condensation is particularly suitable for temperature sensitive materials such as naturally occurring components where the condensation pressure and thus the process temperature are reduced to limit thermal stress to the product. However, these process conditions can lead to a loss in condenser performance. With a lower process pressure the leakage of non-condensable gases into the system increases considerably.
The presence of non-condensable gases influences the condensation performance of the product vapour in two respects: a) thermodynamic effect: at a given total pressure, the presence of inerts reduces the partial pressure of the condensable component, thus also reducing its condensation temperature, and b) mass transfer effect: the accumulation of non condensed components in the vicinity of the heat transfer surface reduces access of the condensable species to the condenser surface and triggers a diffusive flux of the inert components countercurrent to the condensable species. Overall, the increasing inert gas fraction in the gas phase along the heat transfer surface leads to a reduction of the heat exchanger performance.
Calculating the condenser performance in advance should help to evaluate the effects of the non- condensable component on the condensation. Various calculation models are available in the literature. These should be reviewed and evaluated in a critical literature revision. Subsequently, a too l shall be developed to incrementally simulate the condensation in a vertical tube with a suitable calculation model. The results of the calculation can be compared to experiments at the condensation plant at ICTV (Institut für Chemische und Thermische Ver fahrenstechnik). The following points need to be worked on in detail:
- Literature search regarding the state of knowledge on condensation in vertical tubes and corresponding calculation models,
- Comparison of the scope, assumptions and applications of the existing calculation methods,
- Development a tool for the condensation calculation based on suitable mechanistic models and
- Comparison and discussion of the results.
The work is conducted in cooperation with the Institute for Thermodynamics at the Leibniz Universität Hannover, supervised by Prof. Stephan Kabelac. The original and two copies of the Master thesis should be submitted and introduced in an oral presentation.
The presence of non-condensable gases influences the condensation performance of the product vapour in two respects: a) thermodynamic effect: at a given total pressure, the presence of inerts reduces the partial pressure of the condensable component, thus also reducing its condensation temperature, and b) mass transfer effect: the accumulation of non condensed components in the vicinity of the heat transfer surface reduces access of the condensable species to the condenser surface and triggers a diffusive flux of the inert components countercurrent to the condensable species. Overall, the increasing inert gas fraction in the gas phase along the heat transfer surface leads to a reduction of the heat exchanger performance.
Calculating the condenser performance in advance should help to evaluate the effects of the non- condensable component on the condensation. Various calculation models are available in the literature. These should be reviewed and evaluated in a critical literature revision. Subsequently, a too l shall be developed to incrementally simulate the condensation in a vertical tube with a suitable calculation model. The results of the calculation can be compared to experiments at the condensation plant at ICTV (Institut für Chemische und Thermische Ver fahrenstechnik). The following points need to be worked on in detail:
- Literature search regarding the state of knowledge on condensation in vertical tubes and corresponding calculation models,
- Comparison of the scope, assumptions and applications of the existing calculation methods,
- Development a tool for the condensation calculation based on suitable mechanistic models and
- Comparison and discussion of the results.
The work is conducted in cooperation with the Institute for Thermodynamics at the Leibniz Universität Hannover, supervised by Prof. Stephan Kabelac. The original and two copies of the Master thesis should be submitted and introduced in an oral presentation.