Technical Brief

Modeling and Optimization of Transparent Thermal Insulation Material

[+] Author and Article Information
Marek K. Lewkowicz

Faculty of Mechanical and Power Engineering,
Wroclaw University of Science and Technology,
Wroclaw 50370, Poland
e-mail: marek.lewkowicz@pwr.edu.pl

Sameh Alsaqoor, Ali Alahmer

Mechanical Engineering Department,
Tafila Technical University,
Tafila 66110, Jordan

Gabriel Borowski

Environmental Engineering Faculty,
Lublin University of Technology,
Lublin 20-618, Poland

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 November 13, 2017; final manuscript received April 30, 2018; published online May 29, 2018. Assoc. Editor: M. Keith Sharp.

J. Sol. Energy Eng 140(5), 054501 (May 29, 2018) (6 pages) Paper No: SOL-17-1453; doi: 10.1115/1.4040197 History: Received November 13, 2017; Revised April 30, 2018

Radiative properties of transparent insulations made of a layer of parallel, small-diameter, thin-walled, visible light transparent pipes placed perpendicularly to the surface of a flat solar absorber are investigated theoretically. A formula for the radiation heat losses through the insulation is derived based on two main assumptions: the system is in steady-state and the fourth power of the temperature along each pipe is linear. Arguments in favor of the assumptions are given. The formula, combined with standard formulas for the conductive heat flux, enables prediction that a 10 cm thick transparent insulation under insolation of 1000 W/m2, at ambient temperature 20 °C, could theoretically raise the absorber temperature to 429 °C and produce 410 W mechanical power under the ideal Carnot cycle. In order to reach that high energy conversion efficiency, the insulation pipes should have diameter less than 0.5 mm and walls about 5 μm thick, which may be technologically challenging.

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Grahic Jump Location
Fig. 1

A piece of the insulation layer consisting of pipes placed on the absorber's plate

Grahic Jump Location
Fig. 2

One pipe of the insulation layer

Grahic Jump Location
Fig. 3

Radiative absorber net heat loss versus aspect ratio along a pipe with 100 deg temperature drop

Grahic Jump Location
Fig. 4

Optimal temperature of absorber as a function of insulation layer thickness L for the absorbed insolation 1000 W/m2

Grahic Jump Location
Fig. 5

Mechanical power in function of the insulation layer thickness L for the absorbed insolation 1000 W/m2




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