• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.30-35
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• 2021

The present study examined the effects of various guide fin structures and boundary parameters on the thermal performance of heat exchangers used in heat recovery thermoelectric generators. The heat transfer rate and pressure drop of the heat exchangers without fins, with circular fins, with triangular fins, and with combined circular and triangular fins were simulated numerically using ANSYS 19.1 commercial code to confirm the effect of the guide fin structures. The heat transfer rate of the heat exchanger with combined fins was 27.0%, 5.2%, and 1.5% higher than those without fins, with circular fins, and with triangular fins, respectively. The pressure drop characteristic of the heat exchanger with the combined fins was 28.3% higher than that without fins but 9.2% and 10.5% lower than those with circular fins and with triangular fins, respectively. The heat exchanger with combined fins as the optimal model showed the highest heat transfer rate of 5664.9 W and pressure drop of 1454.02 Pa for highest hot gas temperature, maximum flow rates of hot gas and coolant, and lowest coolant temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.569-575
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• 2020

Recently, research on renewable energy technologies has come into the spotlight due to rising concerns over the depletion of fossil fuels and greenhouse gas emissions. Demand for portable electronic and wearable devices is increasing, and electronic devices are becoming smaller. Energy harvesting is a technology for overcoming limitations such as battery size and usage time. In this paper, the V-I characteristic curve and internal resistance of thermal electric devices were analyzed, and MPPT control methods were compared. The Perturbation and Observation (P&O) control method is economically inefficient because two sensors are required to measure the voltage and current of a Thermoelectric Generator(TEG). Therefore, this paper proposes a new MPPT control method that tracks MPP using only one sensor for the regulation of the output voltage. The proposed MPPT control method uses the relationship between the output voltage of the load and the duty ratio. Control is done by periodically sampling the output voltage of the DC-DC converter to increase or decrease the duty ratio to find the optimal duty ratio and maintain the MPP. A DC-DC converter was designed using a cascaded boost-buck converter, which has a two-switch topology. The proposed MPPT control method was verified by simulations using PSIM, and the results show that a voltage, current, and power of V=4.2 V, I=2.5 A, and P=10.5 W were obtained at the MPP from the V-I characteristic curve of the TEG.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.3
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• pp.129-140
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• 2013

Bottom Ash is industrial by-product from a thermoelectric power plant. An immense quantities of bottom ash have increased each year, but most of them is reclaimed in ash landfill. In this study, in order to raise recycling rate of Bottom Ash, it is suggested to cure Bottom Ash (BA) mixtures mixed with cement, lime, Fly Ash (FA), and oyster shell (OS). Mixtures of 5~20 % mixing ratio had been cured for 1, 3, 7, 14, and 28 days using sealed curing and air-dry curing method. Unconfined compressive strength test was conducted to determine strength and deformation modulus ($E_{50}$) change for mixtures as mixing ratio and curing day, water contents of mixtures were measured after test. As a result, strength and $E_{50}$ were increased as mixing ratio and curing days, but values and tendencies of them appeared in different as kind of mixture, mixing ratio, curing method, and curing days. The results showed the addition of cement, lime, Fly Ash, and oyster soil in Bottom Ash could improved strength and $E_{50}$ and enlarge its field of being used.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.764-769
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• 2001

Recently, according to increase in the requirement of electric power, a thermoelectric power plant equipped with pulverized coal combustion system is highly valued, because coal has abundant deposits and a low price compared with others. For efficient use of coal fuel, most of plant makers are studying to improve combustion performance and flame stability, and reduce pollutant emission. One of these studies is how to control the profile of particle injection and velocity dependant on coal nozzle. Basically, a mixed flow of gas and particle in coal nozzle is required to have appropriate injection and concentration distribution at exit to achieve flame stability and low pollutant, but it is very difficult to obtain that without help of a coal separating device within nozzle. In this study, each distribution of air and coal flow rate is measured for the coal nozzle with coal separator developed by us. The coal concentration at exit is various according to inlet swirl values and positions of coal separator. Also pressure drop is measured for various operating conditions of this nozzle. From these results, we can find the separation characteristic of new developed coal separator, and select proper operation range of coal nozzle. When this coal nozzle is applied to actual plant, these investigations will be very useful to confirm the shape of coal separator to have efficient particle injection.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.645-649
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• 2013

In this study, we investigated the $NH_3$ oxidation reaction characteristic over $W/TiO_2$ catalyst in order to control $NH_3$ generated from a thermoelectric power plant or incinerator. As a result, it was found that the optimal content of tungsten in $W/TiO_2$ catalyst is 10 wt% and $NH_3$ removal efficiency decreased due to decreasing specific surface areas of catalyst with increasing tungsten contents. When $NH_3$ was injected more than 420 ppm, $NH_3$ conversion decreased at the middle temperature range. In addition, $NH_3$ conversion decreased due to the competitive adsorption of moisture and with increasing oxygen concentration, the $NH_3$ conversion increased while the $N_2$ selectivity decreased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.6
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• pp.521-537
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• 2012

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2011. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of fluid machinery and fluid flow, thermodynamic cycle, and new and renewable energy. Various topics were presented in the field of fluid machinery and fluid flow. Research issues mainly focused on the rankine cycle in the field of thermodynamic cycle. In the new and renewable energy area, researches were presented on geothermal energy, fuel cell, biogas, reformer, solar water heating system, and metane hydration. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer, nanofluids and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer above liquid helium surface in a cryostat, methane hydrate formation, heat and mass transfer in a liquid desiccant dehumidifier, thermoelectric air-cooling system, heat transfer in multiple slot impinging jet, and heat transfer enhancement by protrusion-in-dimples. In the area of pool boiling and condensing heat transfer, researches on pool boiling of water in low-fin and turbo-B surfaces, pool boiling of R245a, convective boiling two-phase flow in trapezoidal microchannels, condensing of FC-72 on pin-finned surfaces, and natural circulation vertical evaporator were actively performed. In the area of nanofluids, thermal characteristics of heat pipes using water-based MWCNT nanofluids and the thermal conductivity and viscosity were measured. In the area of industrial heat exchangers, researches on fin-tube heat exchangers for waste gas heat recovery and Chevron type plate heat exchanger were implemented. (3) Refrigeration systems with alternative refrigerants such as $CO_2$, hydrocarbons, and mixed refrigerants were studied. Heating performance improvement of heat pump systems were tried applying supplementary components such as a refrigerant heater or a solar collector. The effects of frost growth were studied on the operation characteristic of refrigeration systems and the energy performance of various defrost methods were evaluated. The current situation of the domestic cold storage facilities was analyzed and the future demand was predicted. (4) In building mechanical system fields, a variety of studies were conducted to achieve effective consumption of heat and maximize efficiency of heat in buildings. Various researches were performed to maximize performance of mechanical devices and optimize the operation of HVAC systems. (5) In the fields of architectural environment and energy, diverse purposes of studies were conducted such as indoor environment, building energy, and renewable energy. In particular, renewable energy and building energy-related researches have mainly been studied as reflecting the global interests. In addition, various researches have been performed for reducing cooling load in a building using spot exhaust air, natural ventilation and energy efficiency systems.