• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.191-194
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• 2011

Low-grade waste heat has generally been discarded in industry due to lack of efficient recovery methods. In recent years, organic Rankine cycle(ORC) has become a field of intense research and appears as a promising technology for conversion of heat into useful work of electricity. In this work thermodynamic performance of ORC with superheating of vapor is comparatively assessed for various working fluids. Special attention is paid to the effects of system parameters such as the evaporating temperature on the characteristics of the system such as maximum possible work extraction from the given source, volumetric flow rate per 1 kW of net work and quality of the working fluid at turbine exit as well as thermal efficiency.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.3
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• pp.219-227
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• 1989

Performance analysis of an absorption heat pump system for solar energy recovery has been done by computer simulation to find improved working pairs. Based on the thermodynamic analysis, the coefficient of performance and mass flow ratio have been calculated to compare two aqueous solutions [LiCl-water, $LiCi-CaCl_2-Zn(NO_3)_2$-water] which were developed for cooling by others, with the conventional LiBr-water solution. As a result of this analysis, the performances of the new aqueous solutions were found to be better than that of LiBr-water solution not only in cooling systems, but also in heating and in heat transformer systems. Their theoretical thermodynamic performance data were given here with.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.79-86
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• 2009

This research performed to analyze surplus solar energy, which is generated from a greenhouse during daytime, and to make the basic materials for designing thermal energy storage system for surplus solar energy. For this goal, it analyzed the surplus solar energy coming from two types of greenhouse. The results of this research are as per the below: In the case of 1-2W-type greenhouse, this research gave the same temperature and ventilation condition regardless of regions, but it was judged that the quantity of surplus solar energy could be greatly changed, depending on the energy consumed for the photosynthesis and evapotranspiration of crops in the greenhouse, on the heating temperature during daytime and night, on the existence/non-existence of a curtain and its warming effect, and on the ventilation temperature suitable for the overcoming of high temperature troubles or for the optimum cultivation temperature. In the case of a single-span greenhouse, there was a big difference in energy incoming and outgoing by month, but throughout seasons, 85.0 % of the total energy put into the greenhouse was solar energy and the energy input by heating was just 15.0 % of the total. 26.4 % of the total energy input for the greenhouse was used for photosynthesis and evapotranspiration of crops, and 44.2 % of the remaining 73.6 % went out in the form of radiant heat through the surface of the greenhouse. That is, 25.2 % of the total energy loss was just the surplus solar energy. 67.6 % of the total heating energy was concentrically used for 3 months from December to February next year, but the surplus solar energy during the same period was just 19.4 % of the total annual quantity so it was found that the given condition was more restrictive in directly converting the surplus heat into greenhouse heating. Under the disadvantageous circumstance of 3 months from December to February next year, it was possible to supplement 28 % (December) $\sim$ 85 % (February) of heating energy with surplus solar energy.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1660-1668
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• 2017

The flow of liquids submerged with nanoparticles is of significance to industrial applications, specifically in nuclear reactors and the cooling of nuclear systems to improve energy efficiency. The application of nanofluids in water-cooled nuclear systems can result in a significant improvement of their economic performance and/or safety margins. Therefore, in this paper, Marangoni thermal convective boundary layer dusty nanoliquid flow across a flat surface in the presence of solar radiation is studied. A two phase dusty liquid model is considered. Unlike classical temperature-dependent heat source effects, an exponential space-dependent heat source aspect is considered. Stretching variables are utilized to transform the prevailing partial differential system into a nonlinear ordinary differential system, which is then solved numerically via the Runge-Kutta-Fehlberg approach coupled with a shooting technique. The roles of physical parameters are focused in momentum and heat transport distributions. Graphical illustrations are also used to consider local and average Nusselt numbers. We examined the results under both linear and quadratic variation of the surface temperature. Our simulations established that the impact of Marangoni flow is useful for an enhancement of the heat transfer rate.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.780-785
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• 2009

The photovoltaic/thermal collectors (PV/T collectors) combine the solar thermal collector and photovoltaic modules. They can produce thermal energy in the form of hot air or hot water, and converts solar radiation into electricity. The collecctors can improve the electrical performance of PV modules as the heat from the PV module carried away by the thermal part of the system keeping temperatures lower. The basic water cooled PVT collector has metallic water pipes attached to the back of a PV collector. There are main parameters affecting the performance (electrical and thermal) of PVT collectors. This paper analyzed the experimental performance of glazed water PVT module, considering the parameters of solar radiation, inlet water temperature and ambient temperature. It found that solar radiation is the dominant factor for the electrical performance of the collector, and for the thermal performance the inlet water temperature and ambient temperature appeared to be more related.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.304-313
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• 1987

The behaviors of layers developed in a solar pond were studied by experimental and analytical methods. An experimental solar pond heated from below was constructed and operated at the net heat fluxes of 110 and 160W/m$^{2}$ and at the initial salt concentration gradients of 18.2, 27.3 and 36.4%/m. The thicknesses, growth rates, temperature and salt concentration in the top and the bottom mixed layers, the diffusive layer and the upper and the lower interfacial boundary layers were measured. The shadowgraph technique was used in order to observe all layer formation and an electroconductivity-temperature probe consisting of four electrodes was fabricated and used in measuring the salt concentration. Based on the experimental results, a model for the solar pond was developed and the governing equation and the assumptions were established. The governing equations were solved by the numerical method. The calculated results obtained from the analysis were compared with the experimental results.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.563-566
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• 2006

An investigation has been carried for the thermal characteristics of the seasonal storage installation in Cheju. It features the solar collector area of $340m^2$ and the storage capacity of $600m^3$. Four different types of solar collector systems are compared for their performance of collecting solar energy throughout the year. Of these, two are made of tubular shaped vacuum collectors and the others are flat plate collectors. Results indicate that each system could play an important role in exploiting solar energy depending on the temperature range in its operation. Especially, the vacuum collectors outperformed the others when the inlet temperatures of the collector loop were raised beyond $40m^2$. This became more conspicuous as the return temperatures from the storage tank rose reflecting the seasonal variation. Due to the large heat capacity of the storage tank, temperature changes were rather small compared to those in the collecting loop regardless of seasonal fluctuations.

• Structural Engineering and Mechanics
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• v.88 no.6
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• pp.521-533
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• 2023

In the present study, the finite volume method is applied for the thermal performance prediction of the natural ventilation system using vertical solar chimney whereas, design parameters are optimized through the response surface methodology (RSM). The computational simulations are performed for various parameters of the solar chimney such as absorber temperature (40≤T_abs≤70℃), inlet temperature (20≤T₀≤30℃), inlet height of (0.1≤h≤0.2 m) and chimney width (0.1≤d≤0.2 m). Analysis of variance (ANOVA) was carried out to identify the design parameters that influence the average Nusselt number (Nu) and mass flow rate (ṁ). Then, quadratic polynomial regression models were developed to predict of all the response parameters. Consequently, numerical and graphical optimizations were performed to achieve multi-objective optimization for the desired criteria. According to the desirability function approach, it can be seen that the optimum objective functions are Nu=25.67 and ṁ=24.68 kg/h·m, corresponding to design parameters h=0.18 m, d=0.2 m, T_abs=46.81℃ and T₀=20℃. The optimal ventilation flow rate is enhanced by about 96.65% compared to the minimum ventilation rate, while solar energy consumption is reduced by 49.54% compared to the maximum ventilation rate.

• Journal of the Korean Solar Energy Society
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• v.30 no.2
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• pp.33-38
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• 2010

The perimeter zone is space which receives a significant effect of ambient condition, it is necessary to improve the thermal performance in order to building energy saving. For this reason, a lot of study about the active approach is being performed, such as perimeter-less air conditioning system. But the performance of the perimeter zone is necessary to improve, through the passive approach. Therefore, the purpose of this study is to provide basic materials of energy-saving design of perimeter zone, based of the PAL that simulation changing the thickness of insulation and the rate of windows.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.68-73
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• 2011

This study was performed numerical analysis in order to analyze liquid film flow of heat exchanger tube arrangement and configuration of evaporative multi effect distillation system using medium-temperature. Simulation was accomplished the two-dimensional calculations using commercial analyses program FLUENT based on the FVM(finite volume method). Fresh water generator of this study used Shell & Tubes heat exchanger with Cu_Ni tube, configuration of tube used bare tube and corrugated tube, and arrangement of tube used in-line array and staggered array. Performance of heat exchanger through the formation of liquid film was compared and analyzed. Liquid film flow occurred that falling on heat exchanger tube wall. Result of simulation showed that liquid film thickness of in-line arrangement was found 0.57mm with bare tube and 0.67mm with corrugated tube, respectively. And liquid film thickness of staggered arrangement was found 0.39mm with bare tubes and 0.62mm with corrugated tubes, respectively. Liquid film thickness of corrugated tube showed thicker than bare tube, but heat transfer rates of corrugated tube showed higher than bare tube. The reason was considered that surface area of corrugated tube was wider than bare tube. And liquid film thickness of staggered arrangement showed thinner than in-line arrangement, so thermal performance of staggered arrangement showed higher than in-line arrangement.