• Title/Summary/Keyword: CopA3

Search Result 447, Processing Time 0.023 seconds

Basic Design and Performance Analysis of an Solar Absorption Chiller (태양열 구동 흡수식 냉동기의 기본설계 및 성능분석)

  • Baek, N.C.;Yoon, E.S.;Joo, M.C.;Jeong, S.
    • Solar Energy
    • /
    • v.18 no.3
    • /
    • pp.107-112
    • /
    • 1998
  • Basic design of a solar driven absorption cooling machine(SDACM) with a cooling capacity of 5 USRT was carried out. The SDACM is a single effect cycle driven by low temperature hot water from solar collectors. The SDACM design data were calculated by the steady state simulation program which was developed in this study The variation of COP and cooling capacity of the SDACM were investigated at different off-design conditions. Both the cooling capacity and the system COP were improved with decreasing cooling water temperature. If hot water temperature was increased, the cooling capacity was improved but the system COP was found to be decreased. The decrease of the system COP were basically caused by increased thermal loads in the system components.

  • PDF

Theoretical study on the performance improvement of refrigeration system installed with ejector entraining expansion gases after expansion process (이젝터를 적용한 팽창기체 흡입 냉동시스템의 성능향상 해석 연구)

  • Yun, Sangkook
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.38 no.7
    • /
    • pp.828-833
    • /
    • 2014
  • In this paper, the performance characteristics for newly developed ejector refrigeration system, which is that the part of saturated vapor from liquid-vapor separator after ejector expansion process is entrained in ejector, and the saturated liquid flows in the evaporator and compressed with the rest of vapor in separator, is studied. The reasons of the performance improvement of refrigeration system are that the refrigeration capacity is increased due to quality reduction after iso-entropic expansion process by ejector and the compression work is reduced because of the relatively high pressure of vapor refrigerant before compression process. The comparison results of the ejector system entraining expansion gases with the present residential freezer show that the COP increases to 27.8% maximum in case of the pressure drop to 65% of high pressure of freezer, and to 40.1% for 75% pressure drop of refrigerant R401A. The COP improvement rate with 20%~60% pressure lift in diffuser of ejector is only 2.6%~3%.

The Effect of Dual-Task on Standing Postural Control in Persons With Chronic Stroke (만성 뇌졸중 환자의 기립 자세조절에 이중 과제가 미치는 영향)

  • Jeon, Hye-Won;Chung, Yi-Jung
    • Physical Therapy Korea
    • /
    • v.17 no.3
    • /
    • pp.20-30
    • /
    • 2010
  • This study examined whether any changes by mental task types on postural control in chronic stroke persons. Sixteen chronic stroke persons (mean age=53.75 yr) and sixteen age-and gender-matched healthy controls (mean age=54.44 yr) took part in this study. Participants randomly performed three different tasks on the stable and unstable surfaces. The no mental task was to stand while holding a 100 g weight in each hand, the arithmetic task (mental task) was to perform a silent 1-backwards counting while standing and holding a 100 g weight in each hand, and the simple task (mental task) was to stand and hold with both hands a tray (200 g) on which a glass filled with water has been placed. Sway path and sway velocity of the center of pressure (COP) were measured to assess standing postural control by task performance using the force platform. According to the results, in stroke group, total sway path and total sway velocity of COP was significantly decreased during arithmetic and simple task compared to no mental task on the stable surface (p<.05), and sway path (anteroposterior AP, mediolateral ML) of COP, total and sway velocity (AP, ML, total) of COP was significantly decreased during arithmetic and simple task compared to no mental task on the unstable surface (p<.05). Especially, sway path (AP, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased under the simple task when compared to the arithmetic task on the unstable surface (p<.05). In healthy control group, sway path (AP, ML, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased during arithmetic and simple task compared to no mental task on the stable and unstable surface (p<.05), and sway path (AP, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased under the simple task when compared to the arithmetic task on the unstable surface (p<.05). In conclusion, the findings of this study showed that arithmetic and simple task improved standing postural control for chronic stroke patients and the type of arithmetic and simple tasks were critical factor that reduced standing postural sway in dual-task conditions. Future research should determine whether dual-task conditions, including simple task, would be effective as a training program for standing postural control of stroke patients.

Experimental Study on Cooling Characteristics of Multi - Air Conditioner using Inverter Scroll Compressor (인버터 스크롤 압축기를 사용한 멀티 에어컨의 냉방 특성에 대한 실험적 연구)

  • 권영철;고국원;진의선;허삼행;전용호;이영덕;박인규
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.16 no.4
    • /
    • pp.311-317
    • /
    • 2004
  • In the present study, the cooling characteristics of the multi-air conditioner (A/C) using an inverter scroll compressor are experimentally investigated for the number of the indoor units and the operating conditions (2$0^{\circ}C$, 24$^{\circ}C$, 26$^{\circ}C$) under the cooling standard conditions by KS C 9306. In the case of the simultaneous operation for 3 indoor units, the cooling capacity, the mass flow rate and the input power have a decreasing trend and COP has an increasing trend, with decreasing the difference in the operating temperature of the indoor unit and the room temperature. In the case of the simultaneous operation for 2 indoor units, the COP of the indoor unit with large cooling capacity is high when the operating temperature is high, but the COP of the indoor unit with low cooling capacity is high when the operating temperature is low. In the case of the single operation for one unit, when the large cooling capacity of the indoor unit is less than 50% the compressor operates at the minimum operation frequency region and the COP decreases.

Formability Evaluation of the Vacuum Resin Transfer Molding of a CFRP Composite Automobile Seat Cross Part (탄소섬유복합재료의 시트크로스 부품에서 진공수지주입성형에 의한 성형성 평가)

  • Kim, Kun-Young;Kwak, Sung-Hun;Han, Gyu-Dong;Park, Jin-Seok;Cho, Jun-Haeng;Lee, Chang-Hoon;Kang, Myung-Chang
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.16 no.3
    • /
    • pp.24-29
    • /
    • 2017
  • In this study, a seat cross member was fabricated by optimizing the resin transfer molding processing of CFRP (Carbon Fiber Reinforced Plastics) materials. This seat cross member is used in automotive underbody parts and provides side impact support. The seat cross was manufactured via vacuum resin transfer molding. The process included 1min of resin injection, 8 mins of heating, and 1 min of cooling, for a total molding time of 10mins. Tensile test results showed an average breaking load of 21.50kN, a tensile strength of 404 MPa, and an elastic modulus of 46.2 GPa. As a result, the CFRP seat cross provides the same strength as a similar steel part, but weighs 42% less.

Study of Pulse Generator used Inverter HV Power Supply (XFEL를 위한 기존의 펄스전원공급장치 개선 연구)

  • Park, S.S.;Kim, S.H.;Kim, S.C.;Hwang, J.Y.;Han, Y.J.;Chio, J.H.;Kim, H.G.
    • Proceedings of the KIEE Conference
    • /
    • 2005.07c
    • /
    • pp.2146-2148
    • /
    • 2005
  • The 2.5GeV linac of the Pohang Light Source(PLS) is planed to be converted to a XFEL. The PAL XFEL requires a new 1.2-GeV linac that will be combined to the existing linac to increase a beam energy upto 3.7GeV. This stability is mainly determined by a low level RF drive system and klystron-modulators. The stability level of the modulator has to be improved 10 times better to meet the pulse stability of 0.02 %. The regulation methods such as traditional de-Qing and precision inverter charging technology are reviewed to find out suitable upgrade scheme of the modulators. In order to obtain electron beam of the consequently stability for XFEL linac, the pulse-to-pulse beam voltage regulation is less than +/-0.5%. To get the reliable stability of the modulator which is less than +/-0.2%, a charging section is improved in a modulator which has been operated with inverter power supply and de-Q'ing.

  • PDF

The Influences of the Refrigerant Adulteration by an Absorbent on the Cooling Capacity and COP of the Absorption Chiller (흡수식 냉동기에서 흡수액이 증발기로 혼입시 냉각용량과 성능계수에 미치는 영향)

  • Park, Chan-Woo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.18 no.9
    • /
    • pp.753-760
    • /
    • 2006
  • The purpose of the present work is to investigate the influence of the refrigerant adulteration by LiBr solution on the cooling capacity and COP for three different types of abso게tion chillers: a single-effect type, a series-flow double-effect type and a parallel-flow with double-effect type. A simulation program has been prepared for the cyclic analysis of absorption chillers. With some assumptions, the calculations have been performed by solving the mass balance equation, energy balance equation and the state equation simultaneously. The range of the LiBr concentration of refrigerant was 0% to 20% in the present study. For the single-effect absorption chiller, the maximum decrease in the cooling capacity was 10% at the 20% of LiBr concentration. For the double-effect chiller, the capacity was decreased by 11.1% for the parallel-flow type and the series-flow type. Also, the COP was reduced by 3.0% in single-effect, 2.8% in series-flow type (SR=0.4) and 2.3% in parallel-flow type.

Effects of Vibratory Stimulus on Postural Balance Control during Standing on a Stable and an Unstable Support (안정판과 불안정판에서 자세 균형 조절에 대한 진동자극의 영향)

  • Yu, Mi;Eun, Hey-In;Kim, Dong-Wook;Kwon, Tae-Kyu;Kim, Nam-Gyun
    • Journal of Biomedical Engineering Research
    • /
    • v.28 no.5
    • /
    • pp.647-656
    • /
    • 2007
  • The purpose of this study was to analyze the effects of vibratory stimulus as somatosensory inputs on the postural control in human standing. To study these effects, the center of pressure(COP) was observed while subjects were standing on a stable and an unstable support with co-stimulated mechanical vibrations to flexor ankle muscles(tibialis anterior tendon, achilles tendon) and two plantar zones on both foot. The COP sway measurement was repeated twice in four conditions: (1) with visual cue and vibration, (2) without visual cue and vibration, (3) with visual cue and without vibration, (4) without visual cue and with vibration. The calculated parameters were the COP sway area and the distance, the median frequency and the spectral energy of COP sway in three intervals $0.1{\sim}0.3,\;0.3{\sim}1,\;1{\sim}3Hz$. The results showed that vibratory stimulus affect postural stability. The reduction rate of the COP sway with vibratory stimulus were higher on the unstable support because the effect of postural stability increases when afferent nervous flow is more activated by vibration on unstable support. If unclear visual or vibratory information is received, one type of information is compared with the other type of sensory information. Then the input balance between visual and vibratory information is corrected to maintain postural stability. These findings are important for the rehabilitation system of postural balance control and the use of vibratory information.

Performance Analysis of Simultaneous Heating & Cooling Water Making System(I)-Simulation (냉.온열 동시 제조시스템의 성능분석(I)-Simulation)

  • Park, Seong-Ryong;Park, Jun-Tack;An, Young-Hun
    • Proceedings of the KSME Conference
    • /
    • 2001.06d
    • /
    • pp.266-271
    • /
    • 2001
  • In this study, the performance of the simultaneous heating & cooling water making system using R134a was investigated by simulation. The most important effect upon heating COP was intermediate pressure depending on input water temperature. With the input water temperature of $10^{\circ}C\;and\;20^{\circ}C$, optimum intermediate pressure were 923 and 1040kPa, respectively. At that optimum intermediate pressure, the maximum heating COP of the system operated between $0^{\circ}C$ evaporating temperature and $70^{\circ}C$ condensing temperature were 4.15 and 3.83. With installation of the subcoolers in high or low pressure section, the system COP was increased by reducing the refrigerant mass flow rate. Under the optimum pressure and $10^{\circ}C$ input water temperature, it was found that heating COP was maximized when the low-subcooler and high-subcooler capacity rate were taken by 14% and 13%, respectively.

  • PDF

A Numerical Simulation of Air-Cooled Ammonia/Water GAX Absorption Cooling Cycle (공냉형 암모니아/물 GAX 흡수식 냉동 사이클의 수치 해석)

  • Jeong, S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.7 no.3
    • /
    • pp.488-500
    • /
    • 1995
  • An air-cooled ammonia/water GAX(Generator-Absorber heat eXchange) absorption cooling cycle is proposed and its performance is numerically evaluated. It is shown that the performance of the system is greatly dependent on the quality of the refrigerant leaving the evaporator. For any refrigerant concentration in the investigated range(99.1~99.9% ammonia), the cycle COP(coefficient of performance) reaches the highest value, when some amount(about 7%) of refrigerant evaporates in the refrigerant heat exchanger. Among temperature differences in various heat exchangers, the temperature difference between GAX-absorber and the GAX-generator shows the greatest effect on the system performance, whereas pressure losses cause no significant decrease in COP. The system COP increases almost linearly with increasing evaporator temperature, decreasing absorber temperature or decreasing condenser temperature. If both absorber and condenser temperature increase simultaneously, the decrease in the COP becomes larger.

  • PDF