The aim of this paper is to present a transient one-dimensional (1D) radial immersed coil heat exchanger model that accounts for the effect that geometry and operating conditions have on heat transfer performance. Insights gained through its use in both an analysis of experimental data and an implementation in the simulation environment TRNSYS are shown and discussed. While variation in the external convection coefficient of immersed coil heat exchangers has little effect on the annual solar fraction of a generic solar domestic hot water system, variation in collector side flow can influence the solar fraction as great as ±5%, in particular low collector side flow improves stratification inside the store.

References

References
1.
Farrington
,
R. B.
, and
Bingham
,
C. E.
,
1986
, “
Testing and Analysis of Immersed Heat Exchangers
,”
Tech. Rep. 254-2866
,
Solar Energy Research Institute, National Renewable Energy Laboratory
, Golden, CO.
2.
Mote
,
R.
, and
Probert
,
S. D.
,
1991
, “
The Performance of a Coiled Finned-Tube Heat Exchanger Submerged in a Hot Water Store: The Effect of the Exchangers Orientation
,”
Appl. Energy
,
38
, pp.
1
19
.10.1016/0306-2619(91)90038-Y
3.
Ali
,
M. E.
,
1994
, “
Experimental Investigation of Natural Convection From Vertical Helical Coiled Tubes
,”
Int. J. Heat Mass Transfer
,
37
(
4
), pp.
665
671
.10.1016/0017-9310(94)90138-4
4.
Xin
,
R. C.
, and
Ebadian
,
M. A.
,
1996
, “
Natural Convection Heat Transfer From Helicoidal Pipes
,”
J. Thermophys. Heat Transfer
,
10
(
2
), pp.
297
302
.10.2514/3.787
5.
Prabhanjan
,
D. G.
,
Rennie
,
T. J.
, and
Vijaya Raghavan
,
G. S.
,
2003
, “
Natural Convection Heat Transfer From Helical Coiled Tubes
,”
Int. J. Thermal Sciences
,
43
, pp.
359
365
.10.1016/j.ijthermalsci.2003.08.005
6.
Reindl
,
D. T.
,
Beckman
,
W. A.
, and
Mitchell
,
J. W.
,
1992
, “
Transient Natural Convection in Enclosures With Application to Solar Thermal Storages Tanks
,”
ASME J. Solar Energy Eng.
,
114
, pp.
175
181
.10.1115/1.2930002
7.
Su
,
Y.
,
2006
, “
Numerical Study of Natural Convection of Heat Exchangers Immersed in a Thermal Storage Vessel
,”
Ph.D. thesis
,
University of Minnesota
, Minneapolis, MN.
8.
Boetcher
,
S. K. S.
,
Kulacki
,
F. A.
, and
Davidson
,
J. H.
,
2010
, “
Negatively Buoyant Plume Flow in a Baffled Heat Exchanger
,”
ASME J. Solar Energy Eng.
,
132
(
3
), p. 034502.10.1115/1.4001471
9.
Shah
,
L. J.
, and
Furbo
,
S.
,
1998
, “
Correlation of Experimental and Theoretical Heat Transfer Mantle Tanks Used in Low Flow SDHW Systems
,”
Solar Energy
,
64
(
4–6
), pp.
245
256
.10.1016/S0038-092X(98)00093-0
10.
Drück
,
H.
,
2007
, “
Mathematische Modellierung und Experimentelle Prüfung von Warmwasserspeichern für Solaranlagen
,”
Ph.D. thesis
,
Universtität Stuttgart, Institut für Thermodynamik und Wärmetechnik
, Stuttgart, Germany.
11.
Davidson
,
J. H.
,
Mantell
,
S. C.
, and
Francis
,
L. F.
,
2007
, “
Thermal and Material Characterization of Immersed Heat Exchangers for Solar Domestic Hot Water
,”
Advances in Solar Energy
, Vol. 17, D. Y. Goswami, ed., Routledge, London, pp.
99
129
.
12.
Hahne
,
E.
,
Kübler
,
R.
, and
Kallweit
,
J.
,
1989
, “
The Evaluation of Thermal Stratification by Exergy
,”
Energy Storage Systems
,
Kluwer Academic
.
New York
, pp.
465
485
.
13.
Messerschmid
,
H.
,
2002
, “
Entwicklung und Validation Eines Numerischen Verfahrens zur Beurteilung von Trinkwasserspeichern
,”
Ph.D. thesis
,
Universtität Stuttgart, Lehrstuhl für Heiz- und Raumlufttechnik
, Stuttgart, Germany.
14.
van Koppen
,
C. W. J.
,
Thomas
,
J. P. S.
, and
Veltkamp
,
W. B.
,
1979
, “
The Actual Benefits of Thermally-Stratified Storage in a Small and Medium Size Solar System
,”
Proceedings of ISES Solar World Congress
, Atlanta, GA, May 28–June 1, pp.
579
580
.
15.
Scheuren
,
J.
,
Pujiula
,
F.
, and
Eisenmann
,
W.
,
2004
, “
Comparative Measurements of Two Identical Thermal Solar Systems With High-Flow and Low-Flow Rates
,”
Proceedings of ISES EuroSun
, Freiburg, Germany, June 20–24.
16.
Davidson
,
J. H.
,
Adams
,
D. A.
, and
Miller
,
J. A.
,
1994
, “
A Coefficient to Characterize Mixing in Solar Water Storage Tanks
,”
ASME J. Solar Energy Eng.
,
116
, pp.
94
99
.10.1115/1.2930504
17.
Rosengarten
,
G.
,
Morrison
,
G.
, and
Behnia
,
M.
,
1999
, “
A Second Law Approach to Characterising Thermally Stratified Hot Water Storage With Application to Solar Hot Water
,”
ASME J. Solar Energy Eng.
,
121
, pp.
194
200
.10.1115/1.2888166
18.
Rosen
,
M. A.
,
2001
, “
The Exergy of Stratified Thermal Energy Storages
,”
Solar Energy
,
71
(
3
), pp.
173
185
.10.1016/S0038-092X(01)00036-6
19.
Huhn
,
R.
,
2007
, “
Beitrag zur Thermodynamischen Analyse und Berwertung von Wasserwärmespeichern in Energieumwandlungsketten
,”
Ph.D. thesis
,
Technischen Universität Dresden
, Deresden, Germany.
20.
Hampel
,
M.
,
2008
, “
Rechnergestützte Entwicklung von Warmwasser Wärmespeichern für Solaranlagen
,”
Ph.D. thesis
,
Universität Stuttgart
, Stuttgart, Germany.
21.
Haller
,
M. Y.
,
Yazdanshenas
,
E.
,
Andersen
,
E.
,
Bales
,
C.
,
Streicher
,
W.
, and
Furbo
,
S.
,
2010
, “
A Method to Determine Stratification Efficiency of Thermal Energy Storage Processes Independently From Storage Heat Losses
,”
Solar Energy
,
84
, pp.
997
1007
.10.1016/j.solener.2010.03.009
22.
van Berkel
,
J.
,
Veltkamp
,
W. B.
, and
Shaap
,
A. B.
,
1991
, “
Thermal Behaviour of a Heat Exchanger Coil in a Stratified Storage
,”
Proceedings of ISES Solar World Congress
, Denver, CO, August 19–23.
23.
van Berkel
,
J.
,
Veltkamp
,
W. B.
, and
Shaap
,
A. B.
,
1993
, “
Heat Transfer Phenomena in a Stratified Storage With Integrated Heat Exchanger Coils
,”
Proceedings of ISES Solar World Congress
, Budapest, August 23–27.
24.
Eichhorn
,
R.
,
Lienhard
,
J. H.
, and
Chen
,
C. C.
,
1974
, “
Natural Convection From Isothermal Spheres and Cylinders Immersed in a Stratified Fluid
,”
5th International Heat Transfer Conference
, Tokyo, September 3–7, Vol.
3
, pp.
10
14
.
25.
Drück
,
H.
,
2006
,
MULTIPORT Store—Model for TRNSYS
,
1.99f ed.
,
Institut für Thermodynamik und Wärmetechnik, Universität Stuttgart, Pfaffenwaldring 6, 70550 Stuttgart
,
Germany
.
26.
Drück
,
H.
,
Bachmann
,
S.
, and
Müller-Steinhagen
,
H.
,
2006
, “
Testing of Solar Hot Water Stores by Means of Up- and Down-Scaling Algorithms
,”
Proceedings of ISES EuroSun
, Glasgow, UK, June 27–30.
27.
Haberl
,
R.
,
Frank
,
E.
, and
Vogelsanger
,
P.
,
2009
, “
Holistic System Testing—10 Years of Concise Cycle Testing
,”
Proceedings of ISES Solar World Congress
, Johannesburg, South Africa, October 11–14.
28.
Klein
,
S.
,
Newton
,
B. J.
,
Thornton
,
J. W.
,
Bradley
,
D. E.
,
Mitchell
,
J. W.
, and
Kummert
,
M.
,
2006
,
TRNSYS Reference Manual: Mathematical Reference
,
16.1 ed.
,
Solar Energy Laboratory, University of Wisconsin-Madison
, Madison, WI.
29.
Logie
,
W.
, and
Frank
,
E.
,
2011
, “
Experimental and Numerical Investigations on Thermal Energy Storages—Indirect Charging Via Immersed Coil Heat Exchangers
,”
Tech. Rep. BFE/102958
,
Institut für Solartechnik SPF
,
Rapperswil, Switzerland
.
30.
Duffie
,
J. A.
, and
Beckman
,
W. A.
,
2006
,
Solar Engineering of Thermal Processes
,
3rd ed.
John Wiley and Sons
,
New York
.
31.
Cadafalch
,
J.
,
2009
, “
A Detailed Numerical Model for Flat Plate Solar Thermal Devices
,”
Solar Energy
,
83
, pp.
2157
2164
.10.1016/j.solener.2009.08.013
32.
Carbonell
,
D.
,
Cadafalch
,
J.
, and
Consul
,
R.
,
2011
, “
A Transient Model for Radiant Heating and Cooling Terminal Heat Exchangers Applied to Radiant Floors and Ceiling Panels
,”
Proceedings of ISES Solar World Congress
, Kassel, Germany, August 28–September 2.
33.
Gnielinski
,
Y.
,
1986
, “
Heat Transfer and Pressure Drop in Helically Coiled Tubes
,”
Proceedings of the 8th International Heat Transfer Conference
, San Francisco, CA, August 17–22, pp.
2847
2854
.
34.
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
35.
Churchill
,
S. W.
, and
Chu
,
H. H. S.
,
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
36.
Henderson
,
J. B.
, and
Caolo
,
A. C.
,
1983
, “
Optimization of Radial Finned Tube Heat Exchangers for Use in Solar Thermal Storage Systems
,”
Tech. Rep. DOE/R1/25247-T1
,
Dept. of Mechanical Engineering and Applied Mechanics, Rhode Island University
,
Kingston, RI
.
37.
Heimrath
,
R.
, and
Haller
,
M. Y.
,
2007
, “
The Reference Heating System, the Template Solar System
,”
Tech. Rep., IEA SHC Task 32 Subtask A
.
38.
Crank
,
J.
, and
Nicolson
,
P.
,
1996
, “
A Practical Method for Numerical Evaluation of Solutions of Partial Differential Equations of the Heat-Conduction Type
,”
Adv. Comput. Math.
,
6
, pp.
207
226
.10.1007/BF02127704
You do not currently have access to this content.