• Title/Summary/Keyword: Energy saving system

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Numerical Analysis on Heat Gain of Liquid from Ambient Air with Various Fin Heights and Pitches of Fin-and-Tube Heat Exchanger in Hybrid Solar Collector (핀-튜브 열교환 구조를 갖는 복합집열기에서 핀 높이 및 간격에 따른 공기열 이용 액체 가열 성능에 관한 수치해석 연구)

  • Choi, Hwi-Ung;Fatkhur, Rokhman;Lyu, Nam-Jin;Yoon, Jung-In;Son, Chang-Hyo;Choi, Kwang-Hwan
    • Journal of the Korean Solar Energy Society
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    • v.36 no.3
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    • pp.53-61
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    • 2016
  • Solar assisted heat pump system uses solar thermal energy as a heat source of evaporator of heat pump. So, COP can be enhanced as well as collector efficiency. For improving performance of this system, some research about hybrid solar collector that has fin-and-tube heat exchanger has been conducted. This collector can get a thermal energy from ambient air for liquid heating, so heated liquid can be used as a heat source of evaporator in heat pump even the solar radiation is not enough. In this study, numerical analysis was conducted for confirming heat gain of liquid according to fin height and pitch of fin-and-tube heat exchanger in collector. As a result, higher heat gain was obtained on lower fin height and narrow fin pitch, but the pressure drop also increased with increment of heat gain. Thus the JF factor considering both heat transfer enhancement and pressure drop was investigated and the maximum value was shown when the fin height and pitch were 40mm and 45mm. So it is considered that this installation condition has a highest heat transfer improvement when comparing with pressure drop. However heat gain of liquid at this condition was less than the other installation conditions of fin pitch on same height. Then, after establishing a proper minimum heat gain of liquid, actual production and experiment of collector will be conducted with fin height and pitch showing maximum JF factor and satisfying selected minimum heat gain of liquid on the basis of results of this study.

Buffer Cache Management for Low Power Consumption (저전력을 위한 버퍼 캐쉬 관리 기법)

  • Lee, Min;Seo, Eui-Seong;Lee, Joon-Won
    • Journal of KIISE:Computer Systems and Theory
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    • v.35 no.6
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    • pp.293-303
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    • 2008
  • As the computing environment moves to the wireless and handheld system, the power efficiency is getting more important. That is the case especially in the embedded hand-held system and the power consumed by the memory system takes the second largest portion in overall. To save energy consumed in the memory system we can utilize low power mode of SDRAM. In the case of RDRAM, nap mode consumes less than 5% of the power consumed in active or standby mode. However hardware controller itself can't use this facility efficiently unless the operating system cooperates. In this paper we focus on how to minimize the number of active units of SDRAM. The operating system allocates its physical pages so that only a few units of SDRAM need to be activated and the unnecessary SDRAM can be put into nap mode. This work can be considered as a generalized and system-wide version of PAVM(Power-Aware Virtual Memory) research. We take all the physical memory into account, especially buffer cache, which takes an half of total memory usage on average. Because of the portion of buffer cache and its importance, PAVM approach cannot be robust without taking the buffer cache into account. In this paper, we analyze the RAM usage and propose power-aware page allocation policy. Especially the pages mapped into the process' address space and the buffer cache pages are considered. The relationship and interactions of these two kinds of pages are analyzed and exploited for energy saving.

Acoustic Valve Leak Diagnosis and Monitoring System for Power Plant Valves (발전용 밸브누설 음향 진단 및 감시시스템)

  • Lee, Sang-Guk
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.425-430
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    • 2008
  • To verify the system performance of portable AE leak diagnosis system which can measure with moving conditions, AE activities such as RMS voltage level, AE signal trend, leak rate degree according to AE database, FFT spectrum were measured during operation on total 11 valves of the secondary system in nuclear power plant. AE activities were recorded and analyzed from various operating conditions including different temperature, type of valve, pressure difference, valve size and fluid. The results of this field study are utilized to select the type of sensors, the frequency band for filtering and thereby to improve the signal-to-noise ratio for diagnosis for diagnosis or monitoring of valves in operation. As the final result of application study above, portable type leak diagnosis system by AE was developed. The outcome of the study can be definitely applied as a means of the diagnosis or monitoring system for energy saving and prevention of accident for power plant valve. The purpose of this study is to verify availability of the acoustic emission in-situ monitoring method to the internal leak and operating conditions of the major valves at nuclear power plants. In this study, acoustic emission tests are performed when the pressurized temperature water and steam flowed through glove valve(main steam dump valve) and check valve(main steam outlet pump check valve) on the normal size of 12 and 18 ". The valve internal leak monitoring system for practical field was designed. The acoustic emission method was applied to the valves at the site, and the background noise was measured for the abnormal plant condition. To improve the reliability, a judgment of leak on the system was used various factors which are AE parameters, trend analysis, frequency analysis, voltage analysis and amplitude analysis of acoustic signal emitted from the valve operating condition internal leak.

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Development of a Power Management System for Efficient Power usage of Intelligent Ship (지능형 선박의 효울적인 전력사용을 위한 전력 관리 시스템 개발)

  • Park, Ji-Sang;Jeon, Min-Ho;Lee, Myung-Eui
    • Journal of Advanced Navigation Technology
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    • v.17 no.6
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    • pp.609-615
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    • 2013
  • As with any ships, adequate power provision is crucial, especially on the ocean navigating ships far from the land. In order to resolve the effective and economic power supply system of any ship in operation, in this paper, we propose a power management system that intelligently controls the power supply in ships. Power management systems in this design consist of a power load detection system, a generator configuration system, and a power monitoring system respectively. The CT / PT sensor is used to measure amount of current and power in the power detection system, and according to the collected information from various sensor, the generator configuration system will switch on and off the main / sub generator effectively. Finally, the power monitoring system will display all status information of this power management system at a glance for users. This power management systems implemented in this paper is evaluated via real-time experiments, which works well as designed, and certified by KSCIEC61892-1:2012 and KSCIEC60950-1:2008.

Comparison of System Performances of Hot-gas Bypass and Compressor Variable Speed Control of Water Coolers for Machine Tools (핫가스 바이패스 및 압축기 가변속 제어에 의한 공작기계용 수냉각기의 성능 비교)

  • Jeong, Seok-Kwon;Lee, Dan-Bi;Yoon, Jung-In
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.24 no.1
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    • pp.1-8
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    • 2012
  • Recently, the needs of system performances such as working speed and processing accuracy in machine tools have been increased. Especially, the speed increment generates harmful heat at both moving part of the machine tools and handicrafts. The heat is a main drawback to progress accuracy of the processing. Hence, a cooler system to control temperature is inevitable for the machine tools. In general, two representative control schemes, hot-gas bypass and variable speed control of a compressor, have been adopted in the water cooler system. In this paper, comparisons of system performances according to the control schemes in a cooler for machine tools were conducted in detail. Each proportional-integral feedback controller for the two different control systems is designed. The system performances, especially the temperature control accuracy and coefficient of performance which is a criterion of energy saving, were mainly analyzed through various experiments using 1RT water cooler system with different two types of control scheme. These evaluations will provide useful information to choose suitable water cooler system for the engineers who design controllers of the cooler system for machine tools.

Current Status of Lighting System and Illumination Distribution in the Greenhouse for Light Culture of Strawberries (딸기 전조재배 온실의 인공광 설치실태 및 조도분포 조사분석)

  • 김태한;장익주;이경진
    • Journal of Biosystems Engineering
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    • v.24 no.1
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    • pp.19-24
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    • 1999
  • Motivated by the need for developing the more efficient lighting system for light culture of strawberries in the greenhouse, this paper aims at acquiring and suggesting more concrete and scientific foundation of illuminating position, numbers of light source by investigating the types of lighting system and illumination distribution in the greenhouse for light culture of strawberries. The results of investigation and experiment are summarized as following below: 1. The types of lighting system used in the greenhouse producing strawberries were classified as 1 line and 2 lines lighting system. 2. As for the arranging types of artificial light, 2 lines lighting system, were classified as Z-type, N-type and W-type. (Refer Fig. 3) 3. The results of illumination distribution for Z-type, N-type and W-type of 2 lines illuminating system in the greenhouse with a small size tunnel measured at the height of 1.5m from the ground with 220V, 100W lamp in 6m light gap showed that maximum illuminance are 961x, 1211x, 1251x, minimum illuminance are 4.41x, 4.71x, average illuminance are 33.71x, 43.11x, 44.51x and standard deviations are 28.31x, 35.41x, 38.31x at each types. 4. Proportion of the area below optimal illuminance to floor area at the two lines illuminating system of Z-, N-, and W-type in greenhouse were appeared as 39.4%, 26.0% and 26.3%, respectively. Also proportion of the area over optimal illuminance to floor area at the two lines illuminating system of Z-, N-, W-type in greenhouse were appeared as 16.8%, 14% and 14.7%, respectively. Thus N-type was superior to the others from the view points of optimal illumination distribution and energy saving.

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Particle Swarm Optimization-Based Peak Shaving Scheme Using ESS for Reducing Electricity Tariff (전기요금 절감용 ESS를 활용한 Particle Swarm Optimization 기반 Peak Shaving 제어 방법)

  • Park, Myoung Woo;Kang, Moses;Yun, YongWoon;Hong, Seonri;BAE, KUK YEOL;Baek, Jongbok
    • Journal of IKEEE
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    • v.25 no.2
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    • pp.388-398
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    • 2021
  • This paper proposes a particle swarm optimization (PSO)-based peak shaving scheme using energy storage system (ESS) for electricity tariff reduction. The proposed scheme compares the actual load with the estimated load consumption, calculates the additional output power that the ESS needs to discharge additionally to reduce peak load, and adds the input. In addition, in order to compensate for the additional power, the process of allocating power to the determined point is performed, and an optimization that minimizes the average of the load expected at the active power allocations using PSO so that the allocated value does not affect the peak load. To investigated the performance of the proposed scheme, case study of small and large load prediction errors was conducted by reflecting actual load data and load prediction algorithm. As a result, when the proposed scheme is performed with the ESS charge and discharge control to reduce electricity tariff, even when the load prediction error is large, the peak load is successfully reduced, and the peak load reduction effect of 17.8% and electricity tariff reduction effect of 6.02% is shown.

Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013 (설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.12
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. 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) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

Analysis of Heat Exchanging Performance of Heat Recovering Device Attached to Exhaust Gas Duct (열회수장치에 의한 열회수성능 분석)

  • 서원명;윤용철;강종국
    • Journal of Bio-Environment Control
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    • v.9 no.4
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    • pp.212-222
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    • 2000
  • This study was performed to investigate the performance of heat recovery device attached to exhaust gas flue connected to combustion chamber of greenhouse heating system. The experimental heat recovery system is mainly consisted of LPG combustion chamber and two heat recovery units; unit-A is attached directly to the exhaust gas flue, and unit-B is connected with unit-A. Heat recovery performance was evaluated by estimating total energy amounts by using enthalpy difference between two measurement points together with mass flow rate of gas and/or air passing through each heat recovery unit depending on 5 different flow rates controlled by voltage meter. The results of this experimental study, such as heat exchange behavior of supply air tubes and exhaust air passages crossing the tubes, pressure drop between inlet and outlet, heat recovery performance of exchange unit, etc., will be used as fundamental data for designing optimum heat recovery device to be used for fuel saving purpose by reducing heat loss amounts mostly wasted outside of greenhouse through flue.

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An Analysis of Literature Trends in Green Library (녹색도서관 분야 연구 동향에 관한 분석)

  • Ahn, In-Ja;Kwak, Chul-Wan;Noh, Younghee
    • Journal of the Korean BIBLIA Society for library and Information Science
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    • v.24 no.1
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    • pp.189-205
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    • 2013
  • The purpose of this study is to describe the trends and contents of literature in green library and to suggest the research direction on green library. Earlier studies focus on the green library architecture and necessity, after then green library management studies have proliferated. Green library architecture studies have emphasized on 'energy and atmosphere' and 'indoor environmental quality' based upon 5 categories of LEED evaluation system. Green library management studies have focused on library resources recycling and utilizing energy through effective management of library collection. Based on the analysis of literature, five research directions are suggested, such as the number of libraries in an area, library shelf position and space, library space program, collection ratio for library storage, and user studies.