• Title/Summary/Keyword: 성적 계수

Search Result 267, Processing Time 0.023 seconds

A Experimental Study for Horizontal Geothermal Heat Exchanger System Performance during Intermediate Season (중간기 수평형 지중열교환기의 성능 검토를 위한 실험적 연구)

  • Hwang, Yong Ho;Cho, Sung Woo
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
    • /
    • v.11 no.2
    • /
    • pp.1-6
    • /
    • 2015
  • The horizontal earth-to-air heat exchanger (HEAHES) thermal performance is excellent on cooling and heating season in hot arid regions was reported. But the HEAHES thermal performance results is difficult to find on intermediate season. This paper was performed full scaled experiment to investigate HEAHES thermal performance on intermediate season (Oct. 10th ~ 12th Nov. 12th). When the air entering to HEAHES is the lowest $2.3^{\circ}C$, outlet air temperature from HEAHES is $15.95^{\circ}C$ through PVC pipe that buried length 60m and depth 3m. When the air entering to HEAHES is the highest $24.8^{\circ}C$, outlet air temperature from HEAHES is $22.05^{\circ}C$. During intermediate season, the HEAHES COP is 2.71 in daytime and 6.53 in evening.

Experimental Study of Standalone Cooling and Heating System using Thermoelectric Element for Vehicles (열전소자를 이용한 차량용 독립 냉난방시스템에 대한 실험적 연구)

  • Lee, Dae-Woong
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.26 no.8
    • /
    • pp.375-380
    • /
    • 2014
  • The purpose of this paper is to investigate the cooling and heating performance of a standalone-type thermoelectric system equipped with a thermoelectric module. The system consists of a blower and two thermoelectric modules with a fin, which is soldered onto both sides of the thermoelectric module and a courtesy light. The thermoelectric system experiment is conducted with the intake voltage to find the optimum cooling and heating performance of each. The results showed that the cooling capacity and coefficient of performance (COP) were 22 W and 0.31, and the heating capacity and COP were 147 W and 1.1, respectively. In the vehicle cooling and heating performance test in a climate wind tunnel, the results showed that the standalone thermoelectric system's cooling performance was slightly better than the base system; and the heating performance of the standalone thermoelectric system was $54.1^{\circ}C$ and the COP was 1.3, compared to the base system.

Performance Analysis of Scroll Expander-Compressor Unit for $CO_2$ Transcritical Cycles ($CO_2$ 초임계 사이클을 위한 일체형 스크롤 팽창기-압축기 성능해석)

  • Kim Hyun-Jin;Nam Bo-Young;Ahn Jong-Min
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.18 no.5
    • /
    • pp.434-442
    • /
    • 2006
  • In a two-stage compression $CO_2$ transcritical cycle, application of a scroll expander-compressor unit has been considered in order to improve the cycle COP. For both expander and 1st stage compressor, scroll wrap profile which was originally designed for a R410A air-conditioning cycle mechanism was used with minor modifications: wrap height and involute end angle were adjusted for required displacement volume and built-in volume ratio. For pressure condition of 10 Mpa/3.5 MPa and expander inlet temperature of $35^{\circ}C$, 25% improvement in COP was obtained by using expander-compressor unit. As evaporator pressure increased, COP improvement was lowered mainly due to decreasing compressor peformance.

A study on the Characteristics of the High Efficiency absorption Chiller by Heat Recovering from Condenser (응축기 배열 회수에 의한 흡수식 냉동기의 고효율화에 관한 연구)

  • Park, Chan-Woo
    • Proceedings of the SAREK Conference
    • /
    • 2006.06a
    • /
    • pp.46-51
    • /
    • 2006
  • In order to utilize the refrigerants condensation heat of condenser on the absorption chiller system, the solution cooling condenser(SCC) were proposed, which weak solution of absorber outlet use as a cooling water. As the UA of the solution cooling condenser increased, increasement of COP is about maximum 0.09 in occasion of single effect and is about maximum 0.08 in occasion of double effect series flow. In the case of heat exchanger efficiency is about 0.85, it's increments are 0.08 and 0.072, each. And solution cooling condenser is a more effective device in the single effect absorption system more than double effect system for the principle of operation. In order to increases the heat of solution cooling condenser, if reduce the flow rate of cooling water or the value of UA, it makes COP increase a little, but it brought COP decrease because of increasing the pressure of system.

  • PDF

A Study on the Certified Ground Source Heat Pump and Performance Analysis (지열원 히트펌프 유닛 인증 현황 및 성능 분석에 관한 연구)

  • Chang Woo Yang;Hee Jeong Kang;Jong Min Choi
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
    • /
    • v.18 no.4
    • /
    • pp.22-32
    • /
    • 2022
  • To reduce energy consumption and CO2 emission in building sector, a ground source heat pump system has been highly adopted due to its high efficient by many regulation. A certification system has been operated to distribute reliable and high-efficient heat pump units. In this study, the performance status of the recently certified ground source heat pump unit with components was investigated. All heat pump units certified from 2015 to 2020 were water to water heat pump types. Compared to the past, higher capacity systems over 400 kW have been certificed. The cooling COP of the heat pump unit based on certification criteria showed higher value than the heating COP. It is highly recommended to revise the certified criteria values considering operating conditions individually. Most of ground source heat pump units have employed scroll type compressors and plate type heat exchangers with HFC refrigerant.

Mitral Valve Reconstruction in Mitral Insufficiency : Intermediate-Term Results (승모판 폐쇄부전증에서 승모판 재건술의 중기평가)

  • 김석기;김경화;김공수;조중구;신동근
    • Journal of Chest Surgery
    • /
    • v.35 no.10
    • /
    • pp.705-711
    • /
    • 2002
  • The advantages of mitral valve reconstruction have been well established and so mitral valve reconstruction is now considered as the procedure of choice to correct mitral valve disease. This is the report of intermediate-term results of 38 cases that performed mitral valve reconstruction for valve insufficiency(the total number of mitral valve reconstruction were 49 cases, but 11 cases that performed mitral valve replacement due to incomplete reconstruction were excluded). Material and Method : From March 1991 to March 2001, 38 patients underwent mitral valve repair due to mitral valve regurgitation with or without stenosis. Mean age was 47.6$\pm$14.7 years(range 15 to 70 years) : 11 were men and 27 were women. The causes of mitral valve regurgitation were degenerative in 14, rheumatic in 21, infective in 2 and the other was congenital. Result : According to the Carpentier's pathologic classification of mitral valve regurgitation, 3 were type 1 , 16 were type II and 19 were type III. Surgical procedures were annuloplasty 15, commissurotomy 19, leaflet resection and annular plication 9, chordae shortening 11, chordae transfer 5, new chordae formation 2, papillary muscle splitting 2 and vegetectomy 2. These procedures were combined in most patients. There were 2 early death and the causes of death were respiratory failure, renal failure and sepsis. There was no late death. Valve replacement was done in 6 patients after repair due to valve insufficiency or stenosis 3 weeks, 1, 3, 51, 69, 84months later respectively. These patients have been followed up from 1 to 116 months(mean 43.0 months). The mean functional class(NYHA) was 2.36 pre-operatively and improved to 1.70. Conclusion : In most cases of mitral valve regurgitation, mitral valve reconstruction when technically feasible is effective operation that can achieve stable functional results and low surgical and late mortality.

A Study on Neuroticism in College Students (신경증적 척도에 의한 대학생의 정신건강 평가)

  • Lee, Jung-Hoon;Park, Hyeong-Bae;Cheung, Sung-Douk
    • Journal of Yeungnam Medical Science
    • /
    • v.2 no.1
    • /
    • pp.135-147
    • /
    • 1985
  • The authors studied neuroticism, using Eysenck's Maudsley Personality Inventory (MPI), in 3,893 male college students and 1,976 female college students of Yeungnam University. There was significant difference in the mean averages of total neuroticism scores between male and female students, male students scored $13.45{\pm}7.44$, female students scored $16.89{\pm}7.19$. The items relating to (16) Do you sometimes feel happy, sometimes depressed, without any apparent reason? (38) Do you daydream a lot? (1) Do you have dizzy turns? (2) Do you get palpitations or thumping in your heart? and (35) Do you worry about your health? were scored highly in male, and the items relating to (16) Do you sometimes feel happy, sometimes depressed, without any apparent reason? (1) Do you have dizzy turns? (38) Do you daydream a lot? (8) Do you worry too long over humiliating experiences? (9) Do you consider yourself rather a nervous person? were scored highly in female. Three hundreds and ninety eight male students (10.3%) showed seriously high neuroticism scores of 24 or higher, while 256 female students (13.0%) showed high neuroticism scores of 26 or higher. In a comparison between male students in different school grades, freshman showed the highest level of neuroticism scores. Among the psychosocial factors, there were strong tendencies toward higher neuroticism scores in the students who were dissatisfied with their colleges or departments, and who had pessimistic views of self-image in the past, present, or future in both groups. The male students whose educational fees were paid by their parents, and whose spending money per month was under 10,000 won, showed higher neuroticism scores. The female students whose educational fees were paid by their brothers or sisters, and whose maturation locations were U-P, and who resided in dormitory or other residencies, showed higher neuroticism scores.

  • PDF

Risk Factors of Morbidity and Mortality after Coronary Artery Bypass Grafting (관상동맥우회로 이식술 후 이환과 사망의 위험요인)

  • 박창률;이응배;전상훈;장봉현;이종태;김규태
    • Journal of Chest Surgery
    • /
    • v.31 no.12
    • /
    • pp.1159-1164
    • /
    • 1998
  • Background: Although operative outcome is progressing due to the development of operative techniques and myocardial protection, some patients face an increased morbidity and mortality. Therefore, it has become increasingly important to predict the operative morbidity and mortality. Material and Method: This retrospective study reports the results of risk factor analysis of morbidity and mortality of 137 consecutive patients who were underwent coronary artery bypass graft surgery(CABG). Preoperative variables were age, sex, preoperative myocardial infarction, operative priority, left ventricular ejection fraction, obesity and triple vessel disease. Postoperative morbidities were arrhythmia, wound infection, cerebral infarction, prolonged postoperative hospitalization, pneumonia, acute renal failure, prolonged use of ventilator and operative death. Result: The mean age of total patients was 56.7 years, from 27 to 74. The overall mortality was 6.6%(9 of 137) with the mortality of 3.9%(5 of 128) for elective operation, and 44.4%(4 of 9) for emergent or urgent cases. The morbidity of patients over 65 years was stastistically higher than that of under 65 years. Sex distribution showed no difference in morbidity, however operative mortality rate was slightly higher in women (5/41, 12.19%) than in men(4/96, 4.17%). Morbidity of emergent or urgent operation was 100%, much higher than that of the elective operation. Mortality of the patients whose left ventricular ejection fraction was under 50% was higher than that of those over 50%. Conclusion: We concluded that the risk factors of morbidity after CABG were old age above 65 years and emergent or urgent operation, and that risk factors of mortality were low left venticular ejection fraction under 50% and emergent or urgent operation.

  • PDF

Relationship of Initial Chick Weight to Body Weight in Broiler (브로일러의 발생시 체중이 출하체중에 미치는 영향)

  • 오봉국;최연호;손시환;이문연
    • Korean Journal of Poultry Science
    • /
    • v.12 no.2
    • /
    • pp.59-64
    • /
    • 1985
  • The study was carried out to determine if a difference in initial chick weight was still evident in market body weight(6 or 8 week body weight) of broilers. The data of a total of 800 broiler commercial chick raised at Poultry Breeding Farm, Seoul National University from Aug. 6, 1981 to Oct. 1, 1981 were analysed. The results were summarized as follows: 1. Although the initial chick weight was about the same, male chick grew more rapidly than female and sex difference was the most striking factor in growth rate of broiler in this analysis. 2. The relationship between initial chick weight and body weight after hatching was decreased to the increase of weeks of age in both sexes. Though the correlation coefficients of the 6 week and 8 week body weight to the initial chick weight were 0.15 & 0.15 in female and 0.18 & 0.17 in male, the relationship was highly significant in both sexes. 3. Regressions of 6 and 8 week body weight on the initial chick weight in both sexes indicate that, for each increase of one gram in weight of chick at hatching, the average increase in body weight was 8.33 gram & 10.07 gram in female and 7.85 gram & 11.28 gram in male. Results show that the initial chick weight (1 day of age) influence average body weight of commercial broiler at 6 and 8 weeks of age.

  • PDF

The Comparison Study of Early and Midterm Clinical Outcome of Off-Pump versus On-Pump Coronary Artery Bypass Grafting in Patients with Severe Left Ventricular Dysfunction (LVEF${\le}35{\%}$) (심한 좌심실 부전을 갖는 환자에서 시행한 Off-Pump CABG와 On-Pump CABG의 중단기 성적비교)

  • Youn Young Nam;Lee Kyo Joon;Bae Mi Kyung;Shim Yeon Hee;Yoo Kyung-Jong
    • Journal of Chest Surgery
    • /
    • v.39 no.3 s.260
    • /
    • pp.184-193
    • /
    • 2006
  • Background: Off-pump coronary artery bypass grafting (OPCAB) has been proven to result in less morbidity. The patients who have left ventricular dysfunction may have benefits by avoiding the adverse effects of the cardiopulmonary bypass. The present study compared early and midterm outcomes of off-pump versus on-pump coronary artery bypass grafting (On pump CABG) in patients with severe left ventricular dysfunction. Material and Method: Ninety hundred forth six patients underwent isolated coronary artery bypass grafting by one surgeon between January 2001 and Febrary 2005.. Data were collected in 100 patients who had left ventricular ejection fraction (L VEF) less than $35\%$ (68 OPCAB; 32 On pump CABG). Mean age of patients were 62.9$\pm$9.0 years in OPCAS group and 63.8$\pm$8.0 years in On pump CABG group. We compared the preoperative risk factors and evaluated early and midterm outcomes. Result: In OPCAB and On pump CABG group, mean number of used grafts per patient were 2.75$\pm$0.72, 2.78$\pm$0.55 and mean number of distal anastomoses were 3.00$\pm$0.79, 3.16$\pm$0.72 respectively. There was one perioperative death in OPCAB group ($1.5\%$). The operation time, ventilation time, ICU stay time, CK-MB on the first postoperative day, and occurrence rate of complications were significantly low in OPCAB group. Mean follow-up time was 26.6$\pm$12.8 months (4${\~}$54 months). Mean LVEF of OPCAB and On pump CABG group improved significantly from $27.1\pm4.5\%$ to $40.7\pm13.0\%$ and $26.9\pm5.4\%$ to $33.3\pm13.7\%$. The 4-year actuarial survival rate of OPCAB and On pump CABG group were $92.2\%,\;88.3\%$ and the 4-year freedom rates from cardiac death were $97.7\%,\;96.4\%$ respectively. There were no significant differences between two groups in 4 year freedom rate from cardiac event and angina. Conclusion: OPCAS improves myocardial function and favors early and mid-term outcomes in patients with severe left ventricular dysfunction compared to On pump CABG group. Therefore, OPCAB is a preferable operative strategy even in patients with severe left ventricular dysfunction.