• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.1
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• pp.57-64
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• 2008

Recently, regulation of ventilator installation and its details has been revised and the establishment of heat recovery ventilator in newly built apartments has been obligated. This study was done to offer the method of operation and design of heat recovery ventilator to save energy by measuring its efficiency and comparing with the results of experiment. This paper confirmed that it is desirable to operate heat recovery ventilator by using "by-pass mode" within $60{\sim}80%$ scope of the difference indoor absolute humidity in spring and autumn and outdoor absolute humidity and heat recovery ventilator of energy saving effect is better than constant air volume system.

• Journal of Wellbeing Management and Applied Psychology
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• v.7 no.3
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• pp.1-11
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• 2024

Purpose: The purpose of this study is to present an efficient emission reduction ratio of plastic to reduce carbon dioxide, the main cause of greenhouse gases. Research design, data and methodology: This study calculated the absolute value of carbon dioxide by setting an equation through the emission coefficient using the US EPA's WARM model. Results: In the recycling ratio of 70%, it was found that the energy recovery ratio was 15.6%, which was the energy recovery ratio without generating carbon dioxide. When carbon dioxide is generated by changing plastic waste emissions, optimal efficiency is achieved by reducing emissions by 10% to 30% of energy recovery ratio, 20% to 50% of energy recovery ratio, and 30% to 80% or more of energy recovery ratio. Conclusions: The recycling rate should be set at a minimum of 70%, so that a carbon dioxide-free energy recovery rate could be obtained during the recycling process, supporting an eco-friendly basis for environmental policies aimed at this rate. In addition, it was possible to suggest that it is essential to reduce emissions by at least 30% for eco-friendly recycling measures that can achieve both economic and environmental feasibility in the energy recovery process through incineration during recycling in Korea.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.30 no.1
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• pp.10-16
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• 2018

The climate of summer in Korea is quite hot and humid. Many studies have been carried out to reduce the energy required for operating a dehumidifier. The dehumidifier is mainly connected to the cooling system since it operates in the summer. Conventional dehumidification methods often require additional cooling and energy for dehumidification. In this study, a system for increasing the efficiency by applying a membrane was analyzed. Its energy saving effect was analyzed when it was applied to residential buildings. Economic efficiency was also evaluated. As a result of this study, 9.0% energy savings were achieved for residential buildings. The investment recovery period was 28.9 years. Such long investment recovery period was because the initial investment cost was excessive and annual energy saving only appeared in the summer.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.416-418
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• 2008

Cost effective and high efficiency energy recovery circuit (ERC) using an address voltage source is proposed. Different from prior ERC, the proposed circuit uses a voltage source to charge a panel and a current source to discharge the panel. As a result, it can be achieved zero voltage switching (ZVS) of switches in H-bridge inverter and zero current switching (ZCS) of switches of the ERC. Moreover, the proposed ERC can obtain high efficiency, high performance and the decrease of the cost and the size.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.419-422
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• 1998

This paper presents how to design speed control of wound rotor induction motors with slip energy recovery. The speed is limited at some range of sub-synchronous speed of the rotating magnetic field. The problem with speed control by adjusting resistance value in the rotor circuit reduces the efficiency of power, because of the slip energy is lost when it passes through the rotor resistance. The control system is designed to maintain efficiency of motor, where it recovers loss energy by returning it to the system to improve the efficiency. A new PI control method of adaptive control [1］,［13］is applied for the system with cascade type PI controller on the main loop to keep the speed constant and the internal loop to adjust the rotor appropriated current of the load provides the good transient response without overshoot.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.52-66
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• 2003

Generally we have difficulty in removing oil using mechanical devices because recovery rate and recovery efficiency decrease remarkably when operating in thin oil films or in oils of very high viscosity In the Present study a series of experiments were carried out to study the effect of operating conditions on the rate of recovery for the spilled oil using a drum type skimmer. For each set of experiments depth of immersion, oil film thickness and the circumferential speeds were varied systematically to find the effects on the recovery rate. The results shows that recovery rate is dependent on the contact angle for the depth of immersion and the highest rate of oil recovery shows in the case of a contact angle of 45°(h/d=0.15). For the removal of spilled oil the optimal circumferential speed can be found as the critical value to reach the saturated recovery rate for a given oil film thickness and depth of immersion. Even in thin oil thickness we have enough recovery rate and recovery efficiency within critical circumferential speed this way.

• 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.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.10
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• pp.501-507
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• 2001

In this paper, new high-efficiency zero voltage switching (ZVS) AC-DC boost converter is proposed to achieve power factor correction by simplifing energy recovery circuit. A lot of high power factor correction circuits have been proposed and applied to increase input power factor and efficiency. Most of these circuits may obtain unity power factor and achieve sinusoidal current waveform with zero voltage or/and zero current switching. However, it is difficult for them to obtain low cost, small size, low weight, and low noise. The topology proposed to improve these problems can compact the devices in circuit and can achieve high efficiency ZVS AC-DC boost converter. Simulation and experimental results show that this topology is capable of obtaining high power factor and increasing the efficiency of the system.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.4
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• pp.41-49
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• 2023

This study examined the effect of input substrate concentration on hydrogen production of microbial electrolysis cells. To compare the performance of MEC according to the input substrate concentration, six laboratory-scale MEC reactors were operated by sequentially increasing the input substrate concentration from 2 g/L of sodium acetate, to 4 g/L, and 6 g/L. The current density, hydrogen production, and SCOD removal rate were analyzed, and energy efficiency and cathodic hydrogen recovery were calculated to compare the performance of MEC. The maximum volumetric current density was obtained at 4 g/L condition (76.3 A/m³) and it decreased to 19.0 A/m³, when the input concentration was increased to 6 g/L, which was a 75% decrease compared to the 4 g/L input condition. Maximum hydrogen production was obtained also at 4 g/L condition (47.3 ± 16.8 mL), but maximum hydrogen yield was obtained at 2 g/L input condition (1.1 L H₂/g COD_in). Energy efficiencies were also highest in 2 g/L condition; the lowest result was observed at 6 g/L condition. Maximum electrical energy efficiency was 76.4%, and the maximum overall energy efficiency was 39.7% at 2 g/L condition. However, when the substrate concentration increased to 6 g/L, the performance was drastically decreased. Cathodic hydrogen recovery also showed a similar tendency with energy efficiency, with the lowest concentration condition showing the best performance. It can be concluded that operating at low input substrate concentration might be better when considering not only hydrogen yield but also energy efficiency.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.1
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• pp.1-10
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• 2018

Recently, interest in the development of alternative water resources has been increasing rapidly due to environmental pollution and depletion of water resources. In particular, seawater desalination has been attracting the most attention as alternative water resources. As seawater desalination consumes a large amount of energy due to high operating pressure, many researches have been conducted to improve energy efficiency such as energy recovery device (ERD). Consequently, this study aims to compare the energy efficiency of RO process according to ERD of isobaric type which is applied in scientific control pilot plant process of each $100m^3/day$ scale based on actual RO product water. As a result, it was confirmed that efficiency, mixing rate, and permeate conductivity were different depending on the size of the apparatus even though the same principle of the ERD was applied. It is believed that this is caused by the difference in cross-sectional area of the contacted portion for pressure transfer inside the ERD. Therefore, further study is needed to confirm the optimum conditions what is applicable to the actual process considering the correlation with other factors as well as the factors obtained from the previous experiments.