Study to reduce heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium

Shigeki Hirasawa, Ryohei Tsubota, Tsuyoshi Kawanami, Katsuaki Shirai

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We studied the reduction of natural convection heat loss from a solar thermal collector by placing a high-porosity porous medium above the collector plate in a solar thermal collector system. It is known that natural convection can be diminished in a porous medium. In order to use a porous medium in a solar thermal collector, it is necessary to minimize the shading effect of solar radiation caused by the porous medium. In this work, we used a series of offset wire screens made of fine nylon fishing lines of 0.05 mm in diameter with 2-mm pitch and a porosity of 0.999. The experimental apparatus consisted of a copper 300 mm 300 mm collector plate with a selective absorption film on the surface. We measured the inlet solar radiation, the absorbed solar radiation on the collector plate and the collected heat to cooling water under actual sun radiation, and obtained the reduction rate of the convection heat loss from the collector plate and the shading effect. We changed the condition of the porous medium, the temperature of the collector plate, and the inclined angle of the collector plate. Experimental results of the Nusselt number of natural convection in the high-porosity porous medium agreed with the equation proposed by Gupta et al. [10]. The effect of the inclined angle on the Nusselt number was small. The net reduction rate of natural convection heat loss was 7% by placing the high-porosity porous medium above the collector plate when the temperature of the collector plate was 100°C.

Original languageEnglish
Title of host publicationHeat Transfer and Thermal Engineering
PublisherAmerican Society of Mechanical Engineers (ASME)
Volume8 B
ISBN (Print)9780791856352
DOIs
Publication statusPublished - 2013
Externally publishedYes
EventASME 2013 International Mechanical Engineering Congress and Exposition, IMECE 2013 - San Diego, CA, United States
Duration: 2013 Nov 152013 Nov 21

Other

OtherASME 2013 International Mechanical Engineering Congress and Exposition, IMECE 2013
CountryUnited States
CitySan Diego, CA
Period13/11/1513/11/21

Fingerprint

Heat losses
Natural convection
Porous materials
Porosity
Solar radiation
Nusselt number
Cooling water
Hot Temperature
Sun
Wire
Copper
Radiation
Temperature

Keywords

  • Collector efficiency
  • Natural convection
  • Porous media
  • Solar thermal collector

ASJC Scopus subject areas

  • Mechanical Engineering

Cite this

Hirasawa, S., Tsubota, R., Kawanami, T., & Shirai, K. (2013). Study to reduce heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium. In Heat Transfer and Thermal Engineering (Vol. 8 B). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/IMECE2013-62150

Study to reduce heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium. / Hirasawa, Shigeki; Tsubota, Ryohei; Kawanami, Tsuyoshi; Shirai, Katsuaki.

Heat Transfer and Thermal Engineering. Vol. 8 B American Society of Mechanical Engineers (ASME), 2013.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Hirasawa, S, Tsubota, R, Kawanami, T & Shirai, K 2013, Study to reduce heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium. in Heat Transfer and Thermal Engineering. vol. 8 B, American Society of Mechanical Engineers (ASME), ASME 2013 International Mechanical Engineering Congress and Exposition, IMECE 2013, San Diego, CA, United States, 13/11/15. https://doi.org/10.1115/IMECE2013-62150
Hirasawa S, Tsubota R, Kawanami T, Shirai K. Study to reduce heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium. In Heat Transfer and Thermal Engineering. Vol. 8 B. American Society of Mechanical Engineers (ASME). 2013 https://doi.org/10.1115/IMECE2013-62150
Hirasawa, Shigeki ; Tsubota, Ryohei ; Kawanami, Tsuyoshi ; Shirai, Katsuaki. / Study to reduce heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium. Heat Transfer and Thermal Engineering. Vol. 8 B American Society of Mechanical Engineers (ASME), 2013.
@inproceedings{e64ccdb4b6ee4facaef8983c1d516dda,
title = "Study to reduce heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium",
abstract = "We studied the reduction of natural convection heat loss from a solar thermal collector by placing a high-porosity porous medium above the collector plate in a solar thermal collector system. It is known that natural convection can be diminished in a porous medium. In order to use a porous medium in a solar thermal collector, it is necessary to minimize the shading effect of solar radiation caused by the porous medium. In this work, we used a series of offset wire screens made of fine nylon fishing lines of 0.05 mm in diameter with 2-mm pitch and a porosity of 0.999. The experimental apparatus consisted of a copper 300 mm 300 mm collector plate with a selective absorption film on the surface. We measured the inlet solar radiation, the absorbed solar radiation on the collector plate and the collected heat to cooling water under actual sun radiation, and obtained the reduction rate of the convection heat loss from the collector plate and the shading effect. We changed the condition of the porous medium, the temperature of the collector plate, and the inclined angle of the collector plate. Experimental results of the Nusselt number of natural convection in the high-porosity porous medium agreed with the equation proposed by Gupta et al. [10]. The effect of the inclined angle on the Nusselt number was small. The net reduction rate of natural convection heat loss was 7{\%} by placing the high-porosity porous medium above the collector plate when the temperature of the collector plate was 100°C.",
keywords = "Collector efficiency, Natural convection, Porous media, Solar thermal collector",
author = "Shigeki Hirasawa and Ryohei Tsubota and Tsuyoshi Kawanami and Katsuaki Shirai",
year = "2013",
doi = "10.1115/IMECE2013-62150",
language = "English",
isbn = "9780791856352",
volume = "8 B",
booktitle = "Heat Transfer and Thermal Engineering",
publisher = "American Society of Mechanical Engineers (ASME)",

}

TY - GEN

T1 - Study to reduce heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium

AU - Hirasawa, Shigeki

AU - Tsubota, Ryohei

AU - Kawanami, Tsuyoshi

AU - Shirai, Katsuaki

PY - 2013

Y1 - 2013

N2 - We studied the reduction of natural convection heat loss from a solar thermal collector by placing a high-porosity porous medium above the collector plate in a solar thermal collector system. It is known that natural convection can be diminished in a porous medium. In order to use a porous medium in a solar thermal collector, it is necessary to minimize the shading effect of solar radiation caused by the porous medium. In this work, we used a series of offset wire screens made of fine nylon fishing lines of 0.05 mm in diameter with 2-mm pitch and a porosity of 0.999. The experimental apparatus consisted of a copper 300 mm 300 mm collector plate with a selective absorption film on the surface. We measured the inlet solar radiation, the absorbed solar radiation on the collector plate and the collected heat to cooling water under actual sun radiation, and obtained the reduction rate of the convection heat loss from the collector plate and the shading effect. We changed the condition of the porous medium, the temperature of the collector plate, and the inclined angle of the collector plate. Experimental results of the Nusselt number of natural convection in the high-porosity porous medium agreed with the equation proposed by Gupta et al. [10]. The effect of the inclined angle on the Nusselt number was small. The net reduction rate of natural convection heat loss was 7% by placing the high-porosity porous medium above the collector plate when the temperature of the collector plate was 100°C.

AB - We studied the reduction of natural convection heat loss from a solar thermal collector by placing a high-porosity porous medium above the collector plate in a solar thermal collector system. It is known that natural convection can be diminished in a porous medium. In order to use a porous medium in a solar thermal collector, it is necessary to minimize the shading effect of solar radiation caused by the porous medium. In this work, we used a series of offset wire screens made of fine nylon fishing lines of 0.05 mm in diameter with 2-mm pitch and a porosity of 0.999. The experimental apparatus consisted of a copper 300 mm 300 mm collector plate with a selective absorption film on the surface. We measured the inlet solar radiation, the absorbed solar radiation on the collector plate and the collected heat to cooling water under actual sun radiation, and obtained the reduction rate of the convection heat loss from the collector plate and the shading effect. We changed the condition of the porous medium, the temperature of the collector plate, and the inclined angle of the collector plate. Experimental results of the Nusselt number of natural convection in the high-porosity porous medium agreed with the equation proposed by Gupta et al. [10]. The effect of the inclined angle on the Nusselt number was small. The net reduction rate of natural convection heat loss was 7% by placing the high-porosity porous medium above the collector plate when the temperature of the collector plate was 100°C.

KW - Collector efficiency

KW - Natural convection

KW - Porous media

KW - Solar thermal collector

UR - http://www.scopus.com/inward/record.url?scp=84903440574&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84903440574&partnerID=8YFLogxK

U2 - 10.1115/IMECE2013-62150

DO - 10.1115/IMECE2013-62150

M3 - Conference contribution

AN - SCOPUS:84903440574

SN - 9780791856352

VL - 8 B

BT - Heat Transfer and Thermal Engineering

PB - American Society of Mechanical Engineers (ASME)

ER -