H. NABATI

188

horizontal.

7. Conclusions

Simulating results have been presented for two conden-

sation models and two different geometries. The physics

of the problem and the heat transfer characteristics have

been discussed for these models. The aim was to evalu-

ate numerical modeling capabilities to predict water va-

pour condensation from a flue gas that contains high

concentration of CO2. The results are summarized as

followings:

e to experimen-

ture. However at higher inlet temperatures

nd velocities the sensitivity to these parameters de-

oefficient was estimated by calculat-

ppreciated

an

9.

1) Both models are capable to predict the trends i

condensation process. However, the model based on

oundary layer theory shows closer valu

n

b

tal correlation. The effect of the CO2 presence in the flue

gas as a non-condensable gas was predicted correctly by

both models.

2) Heat transfer coefficient decreases as a consequence

of the increase in CO2 mass fraction for constant wall

temperature as a result of the higher resistance to diffuse

from the flue gas bulk to the boundary layer.

3) The total heat transfer rate depends on inlet velocity

and tempera

a

creases.

4) Heat transfer c

ing the interface temperature. However, it was found that

it is possible to get approximately same results by as-

suming this temperature equal to wall temperature. This

assumption facilitates the numerical efforts.

5) A brief description of the technical approach that

was implemented for current study is:

Modeling surface contact condensers with Fluent© re-

quires the Eulerian model. This Eulerian multiphase

model is an advanced model of Fluent and requires quite

a bit of experience to handle. In addition, modification of

these model to suit condensation process, which itself is

a very complex process, would require both, good under-

standing of the physical process and good knowledge of

model inside the Fluent. The accurateness of the nu-

merical modeling results is determined by the empirical

correlations specified to model the condensation process.

In the industry, there is a practice to model the process

with some correlations available in the open literature

and then tweak various parameters to results which are

close to the experimental results. Such a tuning is neces-

sary in numerical modeling as well for most of the cases,

as the general correlations may not yield accurate results

for a specific set up. It is advisable that designing a con-

denser just based on Numerical results may be a difficult

and expensive task.

8. Acknowledgements

Fluent Inc.’S solver capabilities are highly a

d I hereby knowledge use of it in the current paper.

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