• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_2
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• pp.467-474
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• 2021

The renewable energy is known as eco-friendly energy to reduce the use of fossil fuel and decrease the environmental pollution due to exhaust gas. Targets of solar collector in domestic are usually acquisitions of hot water and hot air. System of air-heating collector is one of the technologies for obtaining hot air in cases of especially heating room and drying agricultural product. The purpose of this study is to investigate the characteristics of thermal flow such as relative pressure, velocity, outlet temperature and buoyancy effect in air-heating collector using solar heat. The flow field of air-heating collector was simulated using ANSYS-CFX program and the behaviour of hot air was evaluated with SST turbulence model. As the results, The streamline in air-heating collector showed several circular shapes in case of condition of buoyancy. Temperature difference in cross section of outlet of air-heating collector did not almost show in cases of buoyancy and small inlet velocity. Furthermore merit of air-heating collector was not observed in cases of inlet velocities. Even though it was useful to select condition of buoyancy for obtaining high temperature, however, it was confirmed that the trade off between high temperature of room and rapid injection of hot air to room could be needed through this numerical analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.11
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• pp.458-465
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• 2016

The purpose of this research is to improve the thermal effiency of solar collector and to quantitatively analyze its performance. Solar thermal systems have been limited to water heating systems mainly using low-temperature range. However, through diverse developments, the application has been extended to medium- and high-temperature fields such as solar heating, solar air conditioning, and solar thermal industrial process. Among the diverse research, this research is specially focusing on enhancement of the thermal performance by minimizing the heat loss coefficient of flat plate solar collectors. In order to do it, a front-side glazing material and a back-side insulation material with high insulated structure is proposed and based on computational analysis, the performance of energy collecting volume of the proposed solar collector is analyzed. The research shows that the proposed structure has the excellent performance at medium- and high-temperature range. therefore, it is expected that the proposed structure can easily replace existing technologies.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.188-193
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• 2012

Recently, the nanofluid which is stably dispersing or suspending of nanoparticles in the conventional heat transfer fluids (HTF) such as water and ethylene glycol has attracted significant interests as a solar thermal energy absorbing medium because they have excellent absorption and thermophysical properties compared to the typical HTF. In the present study, the efficiency of nanofluid-based flat-plate solar collector is analytically evaluated using the theoretical model of energy balance equation. The theoretical model considers the incoming solar radiation as a volumetric heat generation and the water-based single wall carbon nanohorn(SWCNH) nanofluid is used as a solar energy absorbing medium. Finally, the efficiency of nanofluid-based collector is calculated according to the volume fraction of SWCNH using the analytical solution.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.994-1002
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• 2009

In this paper, effect of air gap thickness between absorber plate and glass cover on top heat loss of a closed loop oscillating heat pipe (CLOHP) solar collector was investigated. The CLOHP, which is made of copper with outer diameter of 3.2mm and inner diameter of 2.0mm, comprises 8 turns with heating, adiabatic and cooling section. The heating section of the heat pipe was attached to absorber plate which heated by solar simulator simulated by halogen lamps. The cooling section of the heat pipe was inserted into collector's cooling section that made of transparent acrylic. Temperatures of absorber plate, glass cover, and ambient air measured by K-type thermocouple and were recorded by MV2000-Yokogawa recorder. Top heat loss coefficients and top heat loss of the collector corresponding to some cases of air gap thickness were determined. The result of experiment shows the optimal air gap thickness for minimum top heat loss of this solar collector.

• Journal of the Korean Solar Energy Society
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• v.34 no.6
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• pp.57-65
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• 2014

Solar energy has attracted wide attention as a promising renewable energy source. The goal of this paper is to estimate the dynamic performance of solar flat plate collector system according to the weather conditions and the capacity of heat storage tank. This study provides a detailed description of the modeling methods and materials of the system. The effects of the daily clearness index and the volume of the heat storage tank on the hourly and daily performances of the system are numerically investigated. Special attention is focused on the important system variables including the solar insolation on the collector surface, useful energy, heat loss at the collector, and collector efficiency.

• Journal of Korean Association for Spatial Structures
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• v.13 no.2
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• pp.67-73
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• 2013

This paper attempted to bridge this gap by identifying the number of flat-plate solar collectors. The characteristics of wind pressure coefficients acting on flat-plate solar collectors which are most widely used were investigated for various wind direction. Findings from this study found that the location where the maximum wind pressure coefficient occurred in the solar collector was the edge of the collector. Regarding the characteristics according to the number of collectors, the paper found that downward wind pressure coefficient of the lower edge of the collector was higher than the upward wind pressure coefficient of the upper edge of the collector in the basic module (1 piece). However, as the number of collectors increases, the upward wind pressure coefficient of the upper edge become higher than the downward wind pressure coefficient of the lower edge. Finally yet important, it was found that the location of the maximum wind pressure coefficient was changed according to the number of solar collectors.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.149-156
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• 2013

The performances of solar collectors with single and double evacuated tube were experimentally compared. The solar collector with single evacuated tube using surface treatment in this study consists of radiation fin, heat pipe, absorber plate, glass tube, cap and regulating valve, and so on. Surface treatment was conducted for heat pipe and absorber plate with black chrome plating and copper black coating. As the results, the performance of solar collector with single evacuated tube using surface treatment showed good results compared that of double evacuated tube. Absorber plate played a positive role in performance and showed increase of about 28%. Further performance depends on vacuum degree and vacuum degree has to be considered economical efficiency in solar collector.

• Journal of the Korean Solar Energy Society
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• v.23 no.3
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• pp.15-22
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• 2003

This study deals with the collection of solar energy and its storage in evacuated tubular collector systems for different types of header design, flow passage and heat transfer devices. In order to elicit the most efficient combination of header design, flow passage, heat transfer hardware and operating conditions, a series of tests were done for the four different types of solar collectors utilizing vacuum tubes. The systems studied here either has the evacuated collector tubes with a metal cap on one end or the all-glass evacuated solar collector tubes These evacuated tubular collectors are known to be more efficient than the flat-plate ones in both direct and diffuse solar radiation. Test results show that the system comprised of the all-glass evacuated tubes with U-shaped copper pipes inside outperforms the other configurations. Especially, a rolled copper sheet tightly placed along the inner surface of each inner tube enhances heat transfer between the heated collector surface and the water contained in the U-shaped copper pipe.

• Journal of the Korean Solar Energy Society
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• v.28 no.4
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• pp.50-55
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• 2008

The Storage efficiency of concentric evacuated tube solar collector is tested for one year from January 1st to December 31st under the real sun condition. The testing equipment is operated continuously for three days without cooling the storage tank. Daily storage efficiency is obtained from dividing stored energy in the storage tank by solar insolation on the solar collector for each day. Daily averaged temperature of the storage tank is lowest in January and highest in August. Monthly averaged storage efficiency is also lowest in November and highest in June. Therefore, it can be said that the storage temperature and the storage efficiency are roughly proportional to outdoor temperature. Furthermore, the daily storage efficiency is reversely proportional to $(T_s-T_a)/I_c$ where $T_s$ and $T_a$ are daily averaged storage temperature and outdoor temperature from sunrise to sunset, and $I_c$ is total insolation on the solar collector for a day.

• New & Renewable Energy
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• v.10 no.4
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• pp.22-28
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• 2014

The thermoelectric generator using solar heat was applied to the device (heat-electricity conversion device) to produce small-scale electricity. The purpose of this study was to investigate the characteristics and performance of the device, which equipped with heat pipe as heat source. The experimental results showed that efficiency of circular single evacuated solar collector was higher 2.7 times than that of rectangular solar collector. Furthermore maximum power of 5 watt was obtained when 2 devices with series array were used and it could be more improved by increasing the number of device or measurement time.