Technical Brief

Elimination of Thermal Bridges in the Construction of a Flat Low-Pressure Solar Collector by Means of a Vacuum Thermal Insulation Bushing

[+] Author and Article Information
Radim Rybár

Faculty of Mining, Ecology,
Process Control and Geotechnologies,
Technical University of Košice,
Letná 9,
Košice 042 00, Slovakia
e-mail: radim.rybar@tuke.sk

Dušan Kudelas

Faculty of Mining, Ecology,
Process Control and Geotechnologies,
Technical University of Košice,
Letná 9,
Košice 042 00, Slovakia
e-mail: dusan.kudelas@tuke.sk

Martin Beer

Faculty of Mining, Ecology,
Process Control and Geotechnologies,
Technical University of Košice,
Letná 9,
Košice 042 00, Slovakia
e-mail: martin.beer@tuke.sk

Jana Horodníková

Faculty of Mining, Ecology,
Process Control and Geotechnologies,
Technical University of Košice,
Letná 9,
Košice 042 00, Slovakia
e-mail: jana.horodnikova@tuke.sk

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received September 11, 2012; final manuscript received March 23, 2015; published online June 18, 2015. Assoc. Editor: Gilles Flamant.

J. Sol. Energy Eng 137(5), 054501 (Jun 18, 2015) (4 pages) Paper No: SOL-12-1223; doi: 10.1115/1.4030230 History: Received September 11, 2012

The paper deals with the elimination of heat losses in a flat low-pressure solar collector caused by direct contact of outlet pipefitting and the Al–Mg collector box. This is manifested by reduced thermal efficiency of the solar collector, especially in cold season, which is in direct conflict with its application, i.e., high-temperature application and application in cold conditions. The solution lies in the proposed new structural element—the vacuum thermal insulation bushing, which is able to simultaneously provide vacuum tightness of the collector box and interrupt the existing thermal conductive connection. The design philosophy was to transfer the vacuum insulating function component from the original pipe—collector box connection to the thermally insulated place bushing—collector box. Two prototypes were constructed and built into experimental vacuum chamber. Significant increase in the temperature gradient was found in performed experiments. Thermal insulation function, vacuum tightness, and resistance to thermomechanical stress have been demonstrated. The thermal insulation function has also been described through the simulations on a computational model, using finite volume method. The proposed solution of bushing has also successfully become the subject of patent protection.

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Grahic Jump Location
Fig. 1

Two design option of vacuum thermal insulation bushing—with sealant (left) and O-rings (right)

Grahic Jump Location
Fig. 2

Unstructured computational mesh of the object model with the designed bushing—a view from the outside and the inside

Grahic Jump Location
Fig. 3

Heat distribution from copper pipes to Al–Mg collector box using (a) the original pipefitting and (b) the proposed thermal insulation bushing

Grahic Jump Location
Fig. 4

Temperature map in the longitudinal section view in the bushing, which is the result of the heat distribution simulation via the construction assemblies of the bushing at the stagnation state of the collector characterized by heat transfer fluid temperature of 306 °C




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