Abstract

The effect of the pitch of a copper coil heat exchanger immersed in a hot water storage tank on heat transfer from the storage tank to the heat exchanger working fluid is investigated. The storage tank is initially quiescent and full of hot water. The heat exchanger located at the top of the tank has a coil diameter just under the tank diameter and has a pitch of 2, 3, 4, 6, or 12 times the heat exchanger diameter, D. The effect of the pitch is explored both with and without a cylindrical baffle, which creates an annular region with the tank wall that has a width of 1.5D and within which the heat exchanger is located. In experiments without the baffle, increasing the heat exchanger pitch improves the rate of heat transfer to the working fluid. The improved heat transfer is attributed to the increased thermal stratification generated by the larger pitches. In experiments with the baffle, the results for experiments with pitches of 2D, 3D, 4D, and 6D are all very similar, with 3D slightly outperforming the others. Heat transfer to the heat exchanger with a 12D pitch was significantly lower than the others. In experiments both with and without the baffle, the larger pitches resulted in more variation in experimental results, despite strict standards for initial and operating conditions. As in the prior work, the presence of the baffle resulted in significantly higher heat transfer rates compared to respective experiments without the baffle.

References

1.
IPCC
,
2021
, “Summary for Policymakers,”
Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change
,
V.
Masson-Delmotte
,
P.
Zhai
,
A.
Pirani
,
S.L.
Connors
,
C.
Péan
,
S.
Berger
,
N.
Caud
,
Y.
Chen
,
L.
Goldfarb
,
M.I.
Gomis
,
M.
Huang
,
K.
Leitzell
,
E.
Lonnoy
,
J.B.R.
Matthews
,
T.K.
Maycock
,
T.
Waterfield
,
O.
Yelekçi
,
R.
Yu
, and
B.
Zhou
, eds.,
Cambridge University Press
,
Cambridge, UK and New York
, pp.
3
32
.
2.
Drück
,
H.
, and
Bachmann
,
S.
,
2002
, “
Hot Water Performance of Solar Combistores–Description of a Test Method and the Experience Gained With the Application of the Method on Three Different Types of Combistores
,” Internation Energy Agency SHC Task 26 Report, Combisystems, Technical Report, Paris, France.
3.
Drück
,
H.
,
2002
, “
Influence of Different Combistore Concepts on the Overall System Performance
,”
International Energy Agency SHC Task 26
,
Industry Workshop
,
Oslo, Norway
,
Apr. 8
, pp.
39
46
.
4.
Drück
,
H.
, and
Hahne
,
E.
,
1998
, “
Test and Comparison of Hot Water Stores for Solar Combistores
,”
Proceedings of EuroSun 1998, Portoroz, Slovenia
,
September
, pp.
14
17
.
5.
Li
,
S.
,
Zhang
,
Y.
,
Zhang
,
K.
,
Li
,
X.
,
Li
,
Y.
, and
Zhang
,
X.
,
2014
, “
Study on Performance of Storage Tanks in Solar Water Heater System in Charge and Discharge Progress
,”
Energy Procedia
,
48
, pp.
384
393
.
6.
Haltiwanger
,
J. F.
, and
Davidson
,
J. H.
,
2009
, “
Discharge of a Thermal Storage Tank Using an Immersed Heat Exchanger With an Annual Baffle
,”
Sol. Energy
,
83
(
2
), pp.
193
201
.
7.
Nicodemus
,
J. H.
,
Jeffrey
,
J.
,
Haase
,
J.
, and
Bedding
,
D.
,
2017
, “
Effect of Baffle and Shroud Designs on Discharge of a Thermal Storage Tank Using an Immersed Heat Exchanger
,”
Sol. Energy
,
157
, pp.
911
919
.
8.
Nicodemus
,
J. H.
,
Smith
,
J. H.
, and
Goldstein
,
H.
,
2019
, “
Numerical Simulations of Storage-Side Natural Convection to an Immersed Coiled Heat Exchanger With Baffle-Shrouds
,”
Sol. Energy
,
182
, pp.
304
315
.
9.
Nicodemus
,
J. H.
,
Huang
,
X.
,
Dentinger
,
E.
,
Petitt
,
K.
, and
Smith
,
J. H.
,
2020
, “
Effects of Baffle Width on Heat Transfer to an Immersed Coil Heat Exchanger: Experimental Optimization
,”
ASME J. Energy Resour. Technol.
,
142
(
5
), p.
050901
.
10.
Mote
,
R.
,
Probert
,
S.
, 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
(
2
), pp.
115
136
.
11.
Chauvet
,
L.
,
Nevrala
,
D.
, and
Probert
,
S.
,
1993
, “
Influences of Baffles on the Rate of Heat Recovery Via a Finned-Tubed Heat-Exchanger Immersed in a Hot-Water Store
,”
Appl. Energy
,
45
(
3
), pp.
191
217
.
12.
Su
,
Y.
, and
Davidson
,
J. H.
,
2008
, “
Discharge of Thermal Storage Tanks Via Immersed Baffled Heat Exchangers: Numerical Model of Flow and Temperature Fields
,”
ASME J. Sol. Energy Eng.
,
130
(
2
), p.
021016
.
13.
Boetcher
,
S. K.
,
Kulacki
,
F.
, and
Davidson
,
J. H.
,
2010
, “
Negatively Buoyant Plume Flow in a Baffled Heat Exchanger
,”
ASME J. Sol. Energy Eng.
,
132
(
3
), p.
034502
.
14.
Boetcher
,
S. K.
,
Kulacki
,
F.
, and
Davidson
,
J. H.
,
2012
, “
Use of a Shroud and Baffle to Improve Natural Convection to Immersed Heat Exchanger
,”
ASME J. Sol. Energy Eng.
,
134
(
1
), p.
011010
.
15.
Zemler
,
M. K.
, and
Boetcher
,
S. K.
,
2014
, “
Investigation of Shroud Geometry to Passively Improve Heat Transfer in a Solar Thermal Storage Tank
,”
ASME J. Sol. Energy Eng.
,
136
(
1
), p.
011017
.
16.
Zhao
,
Q.
,
Liu
,
F.
,
Liu
,
C.
,
Tian
,
M.
, and
Chen
,
B.
,
2017
, “
Influence of Spiral Pitch on the Thermal Behaviors of Energy Piles With Spiral-Tube Heat Exchanger
,”
Appl. Therm. Eng.
,
125
, pp.
1280
1290
.
17.
Ferng
,
Y.
,
Lin
,
W.
, and
Chieng
,
C.
,
2012
, “
Numerically Investigated Effects of Different Dean Number and Pitch Size on Flow and Heat Transfer Characteristics in a Helically Coil-Tube Heat Exchanger
,”
Appl. Therm. Eng.
,
36
, pp.
378
385
.
18.
Abu-Hamdeh
,
N. H.
,
Alsulami
,
R. A.
,
Rawa
,
M. J.
,
Aljinaidi
,
A. A.
,
Alazwari
,
M. A.
,
Eltaher
,
M. A.
,
Almitani
,
K. H.
, et al.,
2021
, “
A Detailed Hydrothermal Investigation of a Helical Micro Double-Tube Heat Exchanger for a Wide Range of Helix Pitch Length
,”
Case Stud. Therm. Eng.
,
28
, p.
101413
.
19.
Sparrow
,
E.
, and
Niethammer
,
J.
,
1981
, “
Effect of Vertical Separation Distance and Cylinder-to-Cylinder Temperature Imbalance on Natural Convection for a Pair of Horizontal Cylinders
,”
ASME J. Heat Transfer-Trans. ASME
,
103
(
4
), pp.
638
644
.
20.
Sparrow
,
E. M.
, and
Gregg
,
J. L.
,
1960
, “
Nearly Quasi-Steady Free Convection Heat Transfer in Gases
,”
ASME J. Heat. Transfer-Trans. ASME
,
82
(
3
), pp.
258
260
.
21.
Bergman
,
T. L.
,
Lavine
,
A. S.
,
Incropera
,
F. P.
, and
DeWitt
,
D. P.
,
2011
,
Introduction to Heat Transfer
,
John Wiley & Sons
,
Hoboken, NJ
.
22.
Morgan
,
V. T.
,
1975
, “
The Overall Convective Heat Transfer From Smooth Circular Cylinders
,”
Adv. Heat Transfer
,
11
, pp.
199
264
.
23.
Hilpert
,
R.
,
1933
, “
Heat Transfer From Cylinders
,”
Forsch. Geb. Ingenieurwes
,
4
(
5
), p.
215
.
You do not currently have access to this content.