A numerical study of transient natural convection of water near its density extremum
This numerical (CFD) study investigates the transient natural convection of water near its density extremum in enclosed spaces. Two cases are considered: flows in rectangular cavities; flows within a vertical cylindrical geometry. A non-Boussinesq approach is employed for both cases and the resul...
Saved in:
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | English |
| Published: |
2005
|
| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/8761/1/24p%20SAFIAH%20OTHMAN.pdf http://eprints.uthm.edu.my/8761/ |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | This numerical (CFD) study investigates the transient natural convection of water
near its density extremum in enclosed spaces. Two cases are considered: flows in
rectangular cavities; flows within a vertical cylindrical geometry. A non-Boussinesq
approach is employed for both cases and the results are compared to previous
studies. For the first case of rectangular cell, the cavity was not filled completely full
of water, and a small gap is left at the top in order to have a free surface. Simulations
are carried out with water having initial temperatures of 8, 12, 16 and 20 °C, which is
equal to temperature of the opposing walls, while the entire cavity is insulated. The
fluid is initially still and the temperature of one vertical wall is suddenly lowered to 0
°C. Measurements of the temperature distributions in the cavity were made at three
different vertical positions: yl = 0.01785 m,y2 = 0.07545 m andy3 = 0.1353 m.
Comparison of both predicted flow patterns and calculated temperatures to the
previous study are presented, which confirms that good agreements are obtained. For
the second case of vertical cylinder, distilled water having initial temperature of 8 °C
is used as the medium, while the entire cavity is insulated. This experimental
chamber is enclosed within another glass cylinder, and coolant fluid at a fixed
temperature of 0 °C is pumped continuously through the annular region between the
cylinders. The comparisons of cooling curves with previous work are made at three
different vertical heights of 32, 64 and 96 mm. Results of cooling curve
measurements and the flow patterns present good agreement. From the resulting
numerical output of both cases, it is evident that the density inversion of water has a
significant influence on the natural convection in the cavity. |
|---|