A shroud and baffle configuration is used to passively increase heat transfer in a thermal store. The shroud and baffle are used to create a vena contracta near the surface of the heat exchanger, which will speed up the flow locally and thereby increasing heat transfer. The goal of this study is to investigate the geometry of the shroud in optimizing heat transfer by locally increasing the velocity near the surface of the heat exchanger. Two-dimensional transient simulations are conducted. The immersed heat exchanger is modeled as an isothermal cylinder, which is situated at the top of a solar thermal storage tank containing water (Pr = 3) with adiabatic walls. The shroud and baffle are modeled as adiabatic, and the geometry of the shroud and baffle are parametrically varied. Nusselt numbers and fractional energy discharge rates are obtained for a range of Rayleigh numbers, 105 ≤ RaD ≤ 107 in order to determine optimal shroud and baffle configurations. It was found that a baffle width of 75% of the width of the heat exchanger provided the best heat transfer performance.

References

References
1.
Wade
,
A.
,
Davidson
,
J.
, and
Haltiwanger
,
J.
,
2009
, “
What is the Best Solution to Improve Thermal Performance of Storage Tanks With Immersed Heat Exchangers—Baffles or a Partitioned Tank?
,”
ASME J. Sol. Energy Eng.
,
131
(3), p.
034503
.10.1115/1.3142823
2.
Mote
,
R.
,
Probert
,
S. D.
, and
Nevrala
,
D.
,
1991
, “
The Performance of a Coiled Finned-Tube Heat Exchanger Submerged in a Hot-Water Store: The Effect of the Exchanger's Orientation
,”
Appl. Energy
,
38
, pp.
1
19
.10.1016/0306-2619(91)90038-Y
3.
Mote
,
R.
,
Probert
,
S. D.
, and
Nevrala
,
D.
,
1991
, “
Free-Convective Flows Within a Hot-Water Store, Induced by a Submerged, Relatively Cold Heat Exchanger
,”
Appl. Energy
,
39
, pp.
207
234
.10.1016/0306-2619(91)90009-M
4.
Mote
,
R.
,
Probert
,
S. D.
, and
Nevrala
,
D.
,
1992
, “
Rate of Heat Recovery From a Hot-Water Store: Influence of the Aspect Ratio of a Vertical-Axis Open-Ended Cylinder Beneath a Submerged Heat-Exchanger
,”
Appl. Energy
,
41
, pp.
115
136
.10.1016/0306-2619(92)90040-I
5.
Chauvet
,
L. P.
,
Nevrala
,
D. J.
, and
Probert
,
S. D.
,
1993
, “
Influences of Baffles on the Rate of Heat Recovery Via a Finned-Tube Heat-Exchanger Immersed in a Hot-Water Store
,”
Appl. Energy
,
45
, pp.
191
217
.10.1016/0306-2619(93)90032-K
6.
Su
,
Y.
, and
Davidson
,
J.
,
2008
, “
Discharge of Thermal Storage Tanks Via Immersed Baffled Heat Exchangers: Numerical Model of Flow and Temperature Fields
,”
ASME J. Sol. Energy Eng.
,
130
, p.
021016
.10.1115/1.2856012
7.
Haltiwanger
,
J.
, and
Davidson
,
J.
,
2009
, “
Discharge of Thermal Storage Tank Using an Immersed Heat Exchanger With an Annular Baffle
,”
Sol. Energy
,
83
, pp.
193
201
.10.1016/j.solener.2008.07.017
8.
Kulacki
,
F. A.
,
Davidson
,
J. H.
, and
Herbert
,
M.
,
2007
, “
On the Effectiveness of Baffles in Indirect Solar Storage Systems
,”
ASME J. Sol. Energy Eng.
,
129
(4), pp.
494
498
.10.1115/1.2770757
9.
Boetcher
,
S.
,
Kulacki
,
F.
, and
Davidson
,
J.
,
2010
, “
Negatively Buoyant Plume Flow in a Baffled Heat Exchanger
,”
ASME J. Sol. Energy Eng.
,
132
(3), p.
034502
.10.1115/1.4001471
10.
Boetcher
,
S.
,
Kulacki
,
F.
, and
Davidson
,
J.
,
2012
, “
Use of a Shroud and Baffle to Improve Natural Convection to Immersed Heat Exchangers
,”
J. Sol. Energy Eng.
,
134
(1), p.
011010
.10.1115/1.4005089
11.
Su
,
Y.
, and
Davidson
,
J. H.
,
2005
, “
Natural Convection Heat Transfer in a Collector Storage With an Immersed Heat Exchanger: Numerical Study
,”
ASME J. Sol. Energy Eng.
,
127
(3), pp.
324
332
.10.1115/1.1934735
12.
Morgan
,
V. T.
,
1975
, “
The Overall Convective Heat Transfer From Smooth Circular Cylinders
,”
Adv. Heat Transfer
,
11
, pp.
199
264
.10.1016/S0065-2717(08)70075-3
13.
Churchill
,
S.
, and
Chu
,
H.
,
1975
, “
Correlating Equations for Laminar and Turbulent Free Convection From a Horizontal Cylinder
,”
Int. J. Heat Mass Transfer
,
18
, pp.
1049
1053
.10.1016/0017-9310(75)90222-7
14.
Reindl
,
D. T.
,
Beckman
,
W. A.
, and
Mitchell
,
J. W.
,
1992
, “
Transient Natural Convection in Enclosures With Application to Solar Thermal Storage Tanks
,”
J. Sol. Energy Eng.
,
114
(3), pp.
175
181
.10.1115/1.2930002
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