• Title/Summary/Keyword: Heat Exchanger Efficiency

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Performance analysis of a cooling system with refrigerant in a marine absorption refrigerator (선박용 흡수식 냉동기의 냉매적용 냉각 시스템 성능 분석)

  • Yun, Sang-Kook
    • Journal of Advanced Marine Engineering and Technology
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    • v.40 no.4
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    • pp.282-287
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    • 2016
  • Recently in order to protect the ocean environment and to reduce energy consumption, shipbuilders have been developing highly economized ships. This research analyzed the possibility of adopting the onshore absorption refrigerator to offshore ships having a cooling system with refrigerant by using the waiste heat of the engine jacket cooling water instead of compression refrigerators. The results showed that R236fa could be a suitable medium for absorbing the heat of the absorber and condenser in an absorption refrigerator. The cooling system using R236fa achieved a high COP of 0.798, which is 15% and 5% higher than an air cooling system with a cooling tower and a water cooling system with a heat exchanger, respectively. The cooling system with R236fa achieved high efficiency with a 25% reduction in flow rate of LiBr solution and only 15.7% flow rate of cooling medium as compared to the water cooling system. The heating of sea water by the engine jacket water flowing out from the generator can prevent the crystallization of LiBr solution due to the low temperature of sea water.

Development of Remote Field Eddy Current Pipeline Inspection System (원격장 와전류 배관 탐상 시스템 개발)

  • Jeong, Jin-Oh;Yi, Jae-Kyung;Kim, Hyoung-Jean
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.5
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    • pp.556-560
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    • 2001
  • Remote field eddy current testing (RFECT) with through-wall transmission characteristic is being applied to pipes ranging from small tubes of heat exchanger to natural gas supply pipelines. Cast iron pipes with nominal diameter of 100mm are used primarily as the waterline pipes. The leakage of water occurs due to defects in the pipes caused by vibration of automobiles and corrosion. But, the use of direct inspection methods such as insertion of inspection equipment inside the pipelines has been limited due to its lack of economical efficiency. Economical development of inspection equipments is possible since RFECT method can be easily employed for system integration and quantitative evaluation of both inside and outside defects. In this study, the development of underground pipeline inspection system was tarried out by using RFECT method in consideration of the characteristics of waterline network. This paper specifically describes the design and production of RFECT pipeline inspection pig using centralizer mechanism, development of remote field eddy current signal acquisition and processing software, and review of RFECT system operation procedures.

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Experimental Study of a Recuperator with Offset Strip Fins (오프셋 스트립 휜을 가지는 리큐퍼레이터에 대한 실험적 연구)

  • Kim, Taehoon;Do, Kyu Hyung;Han, Yong-Shik;Choi, Byung-Il;Kim, Myungbae
    • Journal of Energy Engineering
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    • v.24 no.2
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    • pp.72-78
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    • 2015
  • In the present study, a recuperator to improve the thermal efficiency of a micro gas turbine is considered. The counter flow plate-fin heat exchanger with offset strip fins is chosen as the type of the recuperator. From the optimization study as varying design parameters of the recuperator determined from the ideal cycle analysis, the internal structure of the recuperator is determined. The recuperator is made from stainless steel 304. In order to evaluate performance of the recuperator, experimental investigation is performed. The effects of inlet temperature of hot-side of the recuperator on the thermal performance of the recuperator are investigated. As a result, effectiveness of the recuperator obtained from the experiments is well consistent with that obtained from the correlations.

The Study on Performance Characteristics of $NH_3$ Refrigeration System for Various Degree of Superheat - Part II : The Change of Heat Exchanger Type - ($NH_3$ 냉동장치의 과열도 변화에 의한 성능 특성 연구 II -열교환기 타입 변경-)

  • Ha Ok-Nam;Kwon Il-Wook;Jeon Sang-Sin;Lee Seung-Jae;Jung Song-Tae;Ha Kyung-Soo;Yun Kab-Sig;Lee Jong-In;Hong Kyung-Han
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.4
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    • pp.297-302
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    • 2005
  • Since the use of CFC and HCFC refrigerants are to be restricted due to the depletion of ozone layer, this experiment applies the $NH_3$ gas to study the performance characteristics of $NH_3$ refrigeration system by the superheat control for improving the energy efficiency. The experiments are carried out for the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa and for degree of superheat from $0^{\circ}C\;to\;10^{\circ}C$ at each condensing pressure. As a result of experiment, when the degree of superheat is $0^{\circ}C$ at each condensing pressure, the refrigeration system has the highest performance.

Design and Exergy Analysis for a Combined Cycle using LNG Cold/Hot Energy (액화천연가스 냉온열을 이용한 복합사이클의 설계 및 엑서지 해석)

  • Lee Geun Sik
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.4
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    • pp.285-296
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    • 2005
  • In order to reduce the compression power and to use the overall energy contained in LNG effectively, a combined cycle is devised and simulated. The combined cycle is composed of two cycles; one is an open cycle of liquid/solid carbon dioxide production cycle utilizing LNG cold energy in $CO_2$ condenser and the other is a closed cycle gas turbine which supplies power to the $CO_2$ cycle, utilizes LNG cold energy for lowering the compressor inlet temperature, and uses the heating value of LNG at the burner. The power consumed for the $CO_2$ cycle is investigated in terms of a production ratio of solid $CO_2$. The present study shows that much reduction in both $CO_2$ compression power (only $35\%$ of power used in conventional dry ice production cycle) and $CO_2$ condenser pressure could be achieved by utilizing LNG cold energy and that high cycle efficiency ($55.3\%$ at maximum power condition) in the gas turbine could be accomplished with the adoption of compressor inlet cooling and regenerator. Exergy analysis shows that irreversibility in the combined cycle increases linearly as a production ratio of solid $CO_2$ increases and most of the irreversibility occurs in the condenser and the heat exchanger for compressor inlet cooling. Hence, incoming LNG cold energy to the above components should be used more effectively.

A Study of Closed OTEC Power Plants (폐쇄형 해양온도차발전 사이클에 관한 연구)

  • Shin, Sang-Ho;Jung, Dong-Soo;Kim, Chong-Bo;Seo, Tae-Beom;Chun, Won-Gee;Auh, P. Chung-Moo
    • Solar Energy
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    • v.17 no.4
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    • pp.23-33
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    • 1997
  • In this paper, performance of various working fluids is evaluated for the closed Ocean Thermal Energy Conversion(OTEC) power plant operating on Rankine cycle. The evaporator and condenser are modeled via UA and LMTD method while turbine and pump are modeled by specifying isentropic efficiencies. R22, Propane, Propylene, R134a, R125, R143a, R32, R410A and Ammonia are used as working fluids. Results show that newly developed fluids such as R410A and R32 that do not cause stratospheric ozone layer depletion perform as well as R22 and ammonia. The superheat at the evaporator exit and subcooling at the condenser exit do not affect the performance of the simple OTEC power cycle. Turbine efficiency and heat exchanger size influence greatly the performance of the Rankine cycle. Finally, it was shown that closed OTEC power plants can practically generate electricity when the difference in warm and cold sea water inlet temperatures is greater than $20^{\circ}C$.

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Process Improvement and Evaluation of 0.1 MW-scale Test Bed using Amine Solvent for Post-combustion CO2 Capture (0.1 MW급 연소후 습식아민 CO2 포집 Test Bed 공정개선효과 검증)

  • Park, Jong Min;Cho, Seong Pill;Lim, Ta Young;Lee, Young ill
    • KEPCO Journal on Electric Power and Energy
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    • v.2 no.1
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    • pp.103-108
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    • 2016
  • Carbon Capture and Storage technologies are recognized as key solution to meet greenhouse gas emission standards to avoid climate change. Although MEA (monoethanolamine) is an effective amine solvent in $CO_2$ capture process, the application is limited by high energy consumption, i.e., reduction of 10% of efficiency of coal-fired power plants. Therefore the development of new solvent and improvement of $CO_2$ capture process are positively necessary. In this study, improvement of $CO_2$ capture process was investigated and applied to Test Bed for reducing energy consumption. Previously reported technologies were examined and prospective methods were determined by simulation. Among the prospective methods, four applicable methods were selected for applying to 0.1 MW Test Bed, such as change of packing material in absorption column, installing the Intercooling System to absorption column, installing Rich Amine Heater and remodeling of Amines Heat Exchanger. After the improvement construction of 0.1 MW Test Bed, the effects of each suggested method were evaluated by experimental results.

Economic Evaluation of Glass Greenhouse Heating Solar Thermal System Applied with Seasonal Borehole Thermal Energy Storage System (BTES 방식의 계간축열 시스템을 적용한 유리온실의 난방용 태양열시스템의 경제성 평가)

  • Park, Sang-Mi;Seo, Tae-Beom
    • Journal of the Korean Solar Energy Society
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    • v.38 no.5
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    • pp.63-74
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    • 2018
  • The heating performance of a solar thermal seasonal storage system applied to a 1,320 m2 glass greenhouse was analyzed numerically, and the economic feasibility depending upon the number of boreholes was evaluated. For this study, the gardening 16th and 19th zucchini greenhouse of Jeollanam-do agricultural research & extension services was selected. And the heating load of the glass greenhouse selected was 1,147 GJ. BTES(Borehole Thermal Energy Storage) was considered as a seasonal storage, which is relatively economical. The number of boreholes was selected from 25 to 150. The TRNSYS was used to predict and analyze the dynamic performance of the solar thermal system. Numerical simulation was performed by modelling the solar thermal seasonal storage system consisting of flat plate solar collector, BTES system, short-term storage tank, boiler, heat exchanger, pump and controller. As a result of the analysis, when the number of boreholes was from 25 to 50, the thermal efficiency of BTES system and the solar fraction was the highest. When the number of boreholes was from 25 to 50, it was analyzed that the payback period was from 5.2 years to 6.2 years. Therefore it was judged to be the number of boreholes of the proposed system was from 25 to 50, which is the most efficient and economical.

Simultaneous Heating and Cooling Multi-Air Conditioning System for Agricultural Products Management (농수산물 관리를 위한 냉난방 동시형 멀티 에어컨 시스템)

  • Shin, Jin-Seob;Hong, Ji-Young
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.20 no.6
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    • pp.65-70
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    • 2020
  • In this paper, to establish a high-efficiency air-conditioning and heating system, we developed a simultaneous air-conditioning and heating system that can do both air-conditioning and heating at the same time. It was applied to hybrid plant plants to enable automation of complex farms. For this purpose, the heat exchanger, which functions as a condenser during heating, was required to function as an evaporator during cooling so that air conditioning and heating could be implemented simultaneously. For experiments, the simultaneous air conditioning system for heating and cooling was produced and applied to the plant factories in the farms so that plants could be grown, stored, and dried. As a result, a single system was able to control the temperature environment of agricultural products with an energy-saving system that simultaneously resolves heating and cooling. Therefore, efficient crop management was possible by implementing an air conditioning system that did not require installing air conditioners and boilers at the same time.

High-Temperature Corrosion Behavior of Alloy 617 in Helium Environment of Very High Temperature Gas Reactor (초고온가스로 헬륨 분위기에서 Alloy 617의 고온 부식 거동)

  • Lee, Gyeong-Geun;Jung, Sujin;Kim, Daejong;Jeong, Yong-Whan;Kim, Dong-Jin
    • Korean Journal of Metals and Materials
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    • v.50 no.9
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    • pp.659-667
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    • 2012
  • Alloy 617 is a Ni-base superalloy and a candidate material for the intermediate heat exchanger (IHX) of a very high temperature gas reactor (VHTR) which is one of the next generation nuclear reactors under development. The high operating temperature of VHTR enables various applications such as mass production of hydrogen with high energy efficiency. Alloy 617 has good creep resistance and phase stability at high temperatures in an air environment. However, it was reported that the mechanical properties decreased at a high temperature in an impure helium environment. In this study, high-temperature corrosion tests were carried out at $850^{\circ}C-950^{\circ}C$ in a helium environment containing the impurity gases $H_2$, CO, and $CH_4$, in order to examine the corrosion behavior of Alloy 617. Until 250 h, Alloy 617 specimens showed a parabolic oxidation behavior at all temperatures. The activation energy for oxidation in helium environment was 154 kJ/mol. The SEM and EDS results elucidated a Cr-rich surface oxide layer, Al-rich internal oxides and depletion of grain boundary carbides. The thickness and depths of degraded layers also showed a parabolic relationship with time. A normal grain growth was observed in the Cr-rich surface oxide layer. When corrosion tests were conducted in a pure helium environment, the oxidation was suppressed drastically. It was elucidated that minor impurity gases in the helium would have detrimental effects on the high-temperature corrosion behavior of Alloy 617 for the VHTR application.