• The KSFM Journal of Fluid Machinery
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• v.17 no.3
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• pp.5-12
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• 2014

This paper presents a design optimization for meridional profile and blade angle ${\theta}$ of a centrifugal compressor with DOE (design of experiments) and RSM (response surface method). Control points of the $3^{rd}$ order Bezier curve are used for design parameters and specific overall efficiency is used as object function. The response surface function shows good agreement with the 3D computational results. Three different optimized designs are proposed and compared with reference design at design point and off-design point. Contours of relative Mach number, static entropy, and total pressure are analyzed for improvement of performance by optimization. Off-design performance analysis is conducted by total pressure and efficiency.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.7
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• pp.329-334
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• 2014

This study indicated the possibility of energy regeneration from waste coolant heat, by using thermoelectric generation integrated with heat pipe. The internal combustion engine rejects more than 60% wasteful energy to the atmosphere by heat. The thermoelectric generator has recently been studied, to convert the energy from engine waste heat into electricity. For coolant waste heat recovery, a thermoelectric generator was investigated, to find out the possibility of vehicular application. Performance characteristics were conducted with various test conditions of coolant temperature, coolant mass flow rate, air temperature, and air velocity, with the thermoelectric generator installed either horizontally or vertically. Experimental results show that the electric power and conversion efficiency increases according to the temperature difference between the hot and cold side of the thermoelectric generator, and the coolant flow rate of the hot side heat exchanger. Performance improvement can be expected by optimizing the heat pipe design.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1127-1136
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• 2017

This paper proposes a new soft switching dual input converter for renewable energy systems. Multi-input converters are produced by combining discrete converters. These converters reduce the number of circuit elements, cost, volume and weight of the converter and provide a constant output power in different weather conditions. Furthermore, soft switching techniques can be applied to increase efficiency. In this paper, a Zero Voltage Transition (ZVT) dual input boost converter is presented. Only one auxiliary circuit is used to provide the soft switching condition for all of the semiconductor elements. The proposed converter, which is simulated by ORCAD software, is theoretically analyzed. To confirm the validity of the theoretical analysis, a prototype of proposed converter was constructed. Simulation and experimental results confirm the theoretical analysis. An efficiency comparison shows a one percent improvement at nominal loads.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.728-730
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• 1993

This paper describes a simple but effective V/F control method for energy saving of a special-purpose Induction motor driven by PWM inverter. The proposed method is based on efficiency control with no speed sensor that the V/F patterns could be changed to load variations. The experimental results shows great improvement of both efficiency and power factor and usefulness of the method.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.2
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• pp.277-284
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• 2023

It is not easy to implement an energy management system in an industrial complex where small businesses are scattered, so the method of collecting and adjusting energy-related data is mainly used. FEMS is a system that responds to the demand for a paradigm shift from a passive energy management method to an active energy management method using IoT and ICT. In this study, a factory energy management system(FEMS) is designed for small and medium-sized enterprises located in chemical industrial complexes. Efficiency was confirmed by reviewing energy saving measures and efficiencies through FEMS for the electric energy of facilities built in each company. The cost effectiveness of FEMS is created when it is utilized by responsible and empowered personnel within the business processes of the host company. Therefore, it is necessary to utilize EMS that can be applied to the planning, support, operation and evaluation, and continuous improvement of the energy management system to achieve corporate organization and energy management goals.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.6
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• pp.409-415
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• 2016

In this study, we test the effects of the surface roughness on the hydro efficiency of double-suction centrifugal pumps ($Q=70.7m^3/min$, H = 87 m). The original surface of the impeller and inner casing were coated, resulting in surface-roughness reductions ranging from $100{\sim}110{\mu}m$ to $0{\sim}0.08{\mu}m$. We conducted experimental studies to measure the efficiency of the pumps and operating-pump electro energy variations with different surface roughness values. The experimental results showed that the efficiency of the pumps increased by about 0.8~1.79% and the electric energy of the operating pump was reduced by around 4.38 ~ 6.08%. These results indicate that the performance of the pumps depend largely on the surface roughness of the impeller and inner casing, and by reducing the surface roughness, we can improve the efficiency of the pump and reduce costs by reducing the electric energy consumption.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.30 no.2
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• pp.68-82
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• 2018

Radiant floor heating systems with capillary tubes are energy saving systems in which hot water is circulated into capillary tube with a small diameter. In this study, the heating performance of capillary tube system is investigated in an experimental study and a simulation model. The results of the study showed that, the capillary tube radiant floor heating system maintains a more stable floor surface temperature in comparison a PB pipe system. In terms of energy consumption, the capillary tube radiant floor heating system proved to be more efficient than the PB pipe heating system at $40^{\circ}C$ of low temperature hot water supply. The difference between water temperature and room temperature can be held low for heating which saves energy. Low temperature radiant floor heating system with capillary tubes have significant advantages such as health improvement, low energy cost, optimum use of heat source(boiler) and higher operational efficiency.

• Journal of Power System Engineering
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• v.15 no.5
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• pp.49-53
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• 2011

This study concerns about wireless power generation that uses the energy harvester with EAP actuator. The UWSN(Underwater Wireless Sensor Network) has been considered many times by many researches. Because the information of underwater is getting important to secure the resource or to predict the meteorological phenomena. But the sensor node in the UWSN is driven by the acoustic wave to communicate with other sensor node. And this acoustic wave usually spends a 100 times energy than the RF(Radio Frequency) wave due to transfermation medium(sea water). Therefore the power source of the sensor node is very important that is needed to improve in the UWSN. For this purpose, the energy harvester is made by the acrylic elastomer in this study. And the electrode is modified with an aluminum impurity to improve the efficiency of energy harvester. After that, the modified energy harvester is experimented to confirm the improvement of the energy efficiency.

• Journal of the Korean Wood Science and Technology
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• v.41 no.1
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• pp.77-86
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• 2013

This research was carried out to evaluate and raise the energy efficiency of wood frame house. The commercial solution program CE3 (Construction Energy Efficiency Evaluation) was used for simulating the energy consumption in the single-family wood frame house. The results showed that the annual heating energy demand of the house was 160 kWh per 1 $m^2$ floor area. In order to decrease the heating energy demand, the following energy efficiency methods were applied to the simulation : a) simplification of building shape, b) decrease of windows area, c) application of high performance windows (with low thermal transmittance) and d) application of heat recovery ventilator. In case of replacement of the windows with high performance one with thermal transmittance 1 $W/m^2{\cdot}K$, the lowest heating demand of 80 $kWh/m^2{\cdot}a$ was obtained. The best combination of methods, application of high performance windows and heat recovery ventilator, showed heating energy demand 34.5 $kWh/m^2{\cdot}a$.

• The KSFM Journal of Fluid Machinery
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• v.17 no.4
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• pp.30-39
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• 2014

The cross flow turbine is economical because of its simple structure. For remote rural region, there are needs for a more simple structure and very low head cross flow turbines. However, in this kind of locations, the water from upstream always flows into the turbine with some other materials such as sand and pebble. These materials will be damage to the runner blade and shorten the turbine lifespan. Therefore, there is a need to develop a new type of cross flow turbine for the remote rural region where there is availability of abundant resources. The new design of the cross flow turbine has an inlet open duct, without guide vane and nozzle to simplify the structure. However, the turbine with inlet open duct and very low head shows relatively low efficiency. Therefore, the purpose of this study is to optimize the shape of the turbine inlet to improve the efficiency, and investigate the internal flow of a very low head cross flow turbine. There are two steps to optimize the turbine inlet shape. Firstly, by changing the turbine open angle along with changing the turbine inlet open duct bottom line (IODBL) location to investigate the internal flow. Secondly, keeping the turbine IODBL location at the maximum efficiency achieved at the first step, and changing the turbine IODBL angle to improve the performance. The result shows that there is a 7.4% of efficiency improvement by optimizing turbine IODBL location (open angle), and there is 0.3% of efficiency improvement by optimizing the turbine IODBL angle.