A new, bi-directional thermodiode designed for energy-efficient buildings was constructed and tested. Experimental results are presented and discussed for solar-heating applications. The thermodiode system consisted of a number of rectangular loops filled with water. The tilting angle of the loops can be altered to reverse the direction of natural convection within the loops for bi-directional operations. The horizontal segments of the loops were attached to metallic panels facing indoors or outdoors. The amount of thermal radiation incident on the outdoor-facing surfaces can be adjusted by rotating the panels or by installing a removable shading device in front of the surfaces. Results of the indoor tests for winter use of the diode showed an onset time between 7 to 20 min for natural convection to be induced throughout the loops in the thermodiode. Before the throughflow started, the fluid in the heated copper tubes reached its maximum temperature. A sudden drop and rebound in this temperature was observed immediately after the onset of throughflow. After that, temperatures at different locations on the thermodiode rose at approximately the same rate until a steady state was reached. During the cool-down phase, the temperatures decreased at the same rate without humps, indicating only conduction took place in the rectangular loops when the thermodiode was reverse-biased. A simple analytical model was developed to estimate the temperature variations and heat transfer rates in the diode system. The diode under forward-biased condition increases the heat transfer rate by nearly 100 times for an incident radiation of 600 W/m2.

Issue Section:
Technical Papers
Keywords:
energy conservation, thermal analysis, solar heating, solar absorber-convertors, natural convection
Topics:
Copper, Fluids, Heat, Heat transfer, Natural convection, Radiation (Physics), Solar heating, Structures, Temperature, Design, Solar energy, Heating, Water, Flow (Dynamics), Steady state, Heat conduction
1.
Jasinsky, T., and Buckley, S., 1977, “Thermosyphon Analysis of a Thermic Diode Solar Heating System,” ASME Paper No. 77-WA/Sol-9.
2.
Damerell, P. S., and Schoenhals, R. J., 1978, “Flow in a Toroidal Thermosyphon with Angular Displacement of Heated and Cooled Sections,” ASME Paper No. 78-HT-44.
3.
Torrance
,
K. E.
,
1979
, “
Open-Loop Thermosyphon with Geological Applications
,”
ASME J. Heat Transfer
,
101
, pp.
677
–
683
.
4.
Mertol
,
A.
,
Greif
,
R.
, and
Zvirin
,
Y.
,
1981
, “
The Transient, Steady State and Stability Behavior of a Thermosyphon with Throughflow
,”
Int. J. Heat Mass Transf.
,
24
(
4
), pp.
621
–
633
.
5.
Mertol
,
A.
,
Place
,
W.
,
Webster
,
T.
, and
Grief
,
R.
,
1981
, “
Detailed Loop Model (DLM) Analysis of Liquid Solar Thermosyphons With Heat Exchangers
,”
Sol. Energy
,
27
, pp.
367
–
386
.
6.
Chen
,
K.
,
1985
, “
The Optimum Configuration of Natural Convection Loops
,”
Sol. Energy
,
34
(
4/5
), pp.
407
–
416
.
7.
Durig, B. R., and Shadday, M. A., Jr., 1986, “Flow in a Rectangular Closed Loop Thermosyphon with Vertical Heat Transfer Passages,” ASME Paper No. 86-WA/HT-78.
8.
Behnia, M., Morrison, G. L., and Paramasivam, S., 1987, “Heat Transfer and Flow in Inclined Open Thermosyphons,” Proceedings of the 1987 ASME/JSME Thermal Engineering Joint Conf., pp. 7–14.
9.
Keller
,
J. B.
,
1966
, “
Periodic Oscillations in a Model of Thermal Convection
,”
J. Fluid Mech.
,
26
, Part 3, pp.
599
–
606
.
10.
Welander
,
P.
,
1967
, “
On the Oscillatory Instability of Differentially Heated Fluid Loop
,”
J. Fluid Mech.
,
29
, Part 1, pp.
17
–
30
.
11.
Creveling
,
H. F.
,
dePaz
,
J. F.
,
Baladi
,
J. Y.
, and
Schoenhals
,
R. J.
,
1975
, “
Stability Characteristics of a Single Phase Free Convection Loop
,”
J. Fluid Mech.
,
67
, Part 1, pp.
65
–
84
.
12.
Zvirin
,
Y.
, and
Grief
,
R.
,
1979
, “
Transient Behavior of Natural Circulation Loops: Two Vertical Branches with Point Heat Source and Sink
,”
Int. J. Heat Mass Transf.
,
22
, pp.
499
–
504
.
13.
Chen
,
K.
,
1985
, “
On the Oscillatory Instability of Closed-Loop Thermosyphons
,”
ASME J. Heat Transfer
,
110
, pp.
299
–
305
.
14.
Duffie, J. A., and Beckman, W. A., 1991, Solar Engineering of Thermal Processes, John Wiley & Sons, New York, pp. 14–23.
15.
Jones
,
G. F.
, and
CIA
,
J.
,
1993
, “
Analysis of a Transient Asymmetrically Heated/Cooled Open Thermosyphon
,”
ASME J. Heat Transfer
,
115
, pp.
621
–
630
.
16.
Madejski
,
J.
, and
Mikielewicz
,
J.
,
1971
, “
Liquid Fin–A New Device for Heat Transfer Equipment
,”
Int. J. Heat Mass Transf.
,
14
, pp.
357
–
363
.
17.
Jones
,
G. F.
,
1986
, “
Heat Transfer in a Liquid Convective Diode
,”
ASME J. Sol. Energy Eng.
,
108
, pp.
163
–
171
.
18.
Chen
,
K.
,
Chailapo
,
P.
,
Chun
,
W. G.
,
Kim
,
S.
, and
Lee
,
K. J.
,
1998
, “
The Dynamic Behavior of a Bayonet-Type Thermal Diode
,”
Sol. Energy
,
64
(
4–6
), pp.
257
–
263
.
19.
Chen
,
K.
,
1988
, “
Design of a Plane-Type Bi-directional Thermal Diode
,”
ASME J. Sol. Energy Eng.
,
110
, pp.
299
–
305
.
20.
Chen, K., Shorthill, R. W., Chu, S. S., Chailapo, P., and Narasimhan, S., 1995, An Energy-Efficient Construction Module of Variable Direction of Heat Flow, Heat Capacity, and Surface Absorptivity, USAF Report WL-TR-95, 3046.
21.
Chun, W. G., Lee, Y. J., Lee, J. Y., Chen, K., Kim, H. T., and Lee, T. K., 1996, “Application of the Thermal Diode Concept for the Utilization of Solar Energy,” Proc. of 31st Intersociety Energy Conversion and Engineering Conf., 3, pp. 1709–1714.
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