# Computational studies for the design of process equipment with complex geometries

##### Semyonov, Denis (2014-02-12)

Väitöskirja

Semyonov, Denis

12.02.2014

Lappeenranta University of Technology

Acta Universitatis Lappeenrantaensis

**Julkaisun pysyvä osoite on**

https://urn.fi/URN:ISBN:978-952-265-560-8

#### Tiivistelmä

This study combines several projects related to the flows in vessels with complex shapes

representing different chemical apparata. Three major cases were studied. The first

one is a two-phase plate reactor with a complex structure of intersecting micro channels

engraved on one plate which is covered by another plain plate. The second case is a

tubular microreactor, consisting of two subcases. The first subcase is a multi-channel

two-component commercial micromixer (slit interdigital) used to mix two liquid reagents

before they enter the reactor. The second subcase is a micro-tube, where the distribution

of the heat generated by the reaction was studied. The third case is a conventionally

packed column. However, flow, reactions or mass transfer were not modeled. Instead, the

research focused on how to describe mathematically the realistic geometry of the column

packing, which is rather random and can not be created using conventional computeraided

design or engineering (CAD/CAE) methods.

Several modeling approaches were used to describe the performance of the processes in the

considered vessels. Computational fluid dynamics (CFD) was used to describe the details

of the flow in the plate microreactor and micromixer. A space-averaged mass transfer

model based on Fick’s law was used to describe the exchange of the species through the

gas-liquid interface in the microreactor. This model utilized data, namely the values of

the interfacial area, obtained by the corresponding CFD model. A common heat transfer

model was used to find the heat distribution in the micro-tube. To generate the column

packing, an additional multibody dynamic model was implemented. Auxiliary simulation

was carried out to determine the position and orientation of every packing element in the

column. This data was then exported into a CAD system to generate desirable geometry,

which could further be used for CFD simulations.

The results demonstrated that the CFD model of the microreactor could predict the flow

pattern well enough and agreed with experiments. The mass transfer model allowed to

estimate the mass transfer coefficient. Modeling for the second case showed that the flow

in the micromixer and the heat transfer in the tube could be excluded from the larger model which describes the chemical kinetics in the reactor. Results of the third case

demonstrated that the auxiliary simulation could successfully generate complex random

packing not only for the column but also for other similar cases.

representing different chemical apparata. Three major cases were studied. The first

one is a two-phase plate reactor with a complex structure of intersecting micro channels

engraved on one plate which is covered by another plain plate. The second case is a

tubular microreactor, consisting of two subcases. The first subcase is a multi-channel

two-component commercial micromixer (slit interdigital) used to mix two liquid reagents

before they enter the reactor. The second subcase is a micro-tube, where the distribution

of the heat generated by the reaction was studied. The third case is a conventionally

packed column. However, flow, reactions or mass transfer were not modeled. Instead, the

research focused on how to describe mathematically the realistic geometry of the column

packing, which is rather random and can not be created using conventional computeraided

design or engineering (CAD/CAE) methods.

Several modeling approaches were used to describe the performance of the processes in the

considered vessels. Computational fluid dynamics (CFD) was used to describe the details

of the flow in the plate microreactor and micromixer. A space-averaged mass transfer

model based on Fick’s law was used to describe the exchange of the species through the

gas-liquid interface in the microreactor. This model utilized data, namely the values of

the interfacial area, obtained by the corresponding CFD model. A common heat transfer

model was used to find the heat distribution in the micro-tube. To generate the column

packing, an additional multibody dynamic model was implemented. Auxiliary simulation

was carried out to determine the position and orientation of every packing element in the

column. This data was then exported into a CAD system to generate desirable geometry,

which could further be used for CFD simulations.

The results demonstrated that the CFD model of the microreactor could predict the flow

pattern well enough and agreed with experiments. The mass transfer model allowed to

estimate the mass transfer coefficient. Modeling for the second case showed that the flow

in the micromixer and the heat transfer in the tube could be excluded from the larger model which describes the chemical kinetics in the reactor. Results of the third case

demonstrated that the auxiliary simulation could successfully generate complex random

packing not only for the column but also for other similar cases.

##### Kokoelmat

- Väitöskirjat [979]