• Title/Summary/Keyword: Oil Circulation Ratio

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An Experimental Study on Correlation between Oil Discharge and Various Operating Conditions of a CO2 Compressor (CO2 압축기의 운전조건과 오일토출의 상관분석에 관한 실험적 연구)

  • Lee, Ik-Soo;Kang, Byung-Ha
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.1
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    • pp.73-79
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    • 2011
  • A portion of oil for lubrication of compressor flows together with refrigerant in the refrigeration system. If the oil discharge from a compressor is increased in the refrigeration system, not only pressure drop is increased in other components, such as evaporator and gas cooler, but also heat transfer coefficient in the heat exchangers is decreased. Oil discharge rate from a compressor may strongly depend on operating conditions of a compressor. In this study, one stage single rotary compressor is employed for measuring oil circulation ratio(OCR). Carbon dioxide and PAG oil are used as refrigerant and lubricant. Using a U-tube densimeter, mixture density is measured. Oil circulation ratio(OCR) can be estimated by measured mixture density. The results obtained indicate that the oil circulation ratio(OCR) is increased as the suction temperature or compressor operating frequency is increased. Oil circulation ratio(OCR) correlation of the compressor is also suggested.

Effect of Suction Temperature and Compressor Frequency on Oil Circulation Ratio in a $CO_2$ Refrigeration System ($CO_2$ 냉동시스템에서 압축기의 흡입온도와 운전주파수가 오일 순환량에 미치는 영향)

  • Kim, Kyung-Jae;Lee, Ik-Soo;Kang, Byung-Ha;Kim, Suk-Hyun
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.893-898
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    • 2009
  • The quantity of discharged oil from a compressor is one of the most important issues for proper operation of refrigeration system. If the oil is increased in the system not only pressure drop is increased in other components, such as evaporator and gas cooler but also heat transfer coefficient in the heat exchangers is decreased. In addition, the lack of oil in the compressor may cause a critical of the system failure. In this study, one stage single rotary compressor is used for measuring oil circulation ratio(OCR). Carbon dioxide and PAG oil are used as refrigerant and lubricant. Using a U-tube densimeter, mixture density is measured. Characteristics of oil circulation ratio have been investigated for $CO_2$ rotary compressor in the range of operation frequency 45 Hz to 63 Hz and the suction temperature range of $0^{\circ}C$ to $15^{\circ}C$. The results obtained indicate that the oil circulation ratio is increased as the suction temperature or compressor operating frequency is increased.

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Experimental study on Effects of POE oil on R134a Evaporation Heat Transfer in Plate Heat Exchanger (판형열교환기에서 POE오일이 R134a 증발 열전달에 미치는 영향에 대한 실험적 연구)

  • Chang, Young Soo;Jang, Jae Kyoo;Kang, Byung Ha;Kim, Sukhyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.3
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    • pp.255-262
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    • 2014
  • To investigate the effect of oil on evaporation heat transfer of plate heat exchanger, evaporation heat transfer experiment was carried out using experimental apparatus for micro gear pumped R134a-oil circulation. By varying oil circulation rate of POE oil from 0 to 5%, evaporation heat transfer performance of plate heat exchanger was investigated. As OCR(Oil Circulation Ratio) increases, the evaporation heat transfer coefficient of R134a decreases and pressure drop increases. When the evaporating temperature is $30^{\circ}C$ and the refrigerant mass flow rate is 80 g/s, evaporation heat transfer rate decreases by 10 % and pressure drop increases by 10% at 2% of OCR condition.

Development of a Cold Rolling Oil with Lubricity and Mill Cleanness Property (윤활성 및 압연기 청정성을 겸비한 냉간 압연유의 개발)

  • 한석영;송교봉;이준정
    • Tribology and Lubricants
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    • v.13 no.2
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    • pp.74-81
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    • 1997
  • The purpose of this study is to develop a cold rolling oil with lubricity and mill cleanness property under the rolling conditions of high reduction ratio and high rolling speed. Six kinds of oil samples were blended. Evaluation of lubricity and anti-seizuro property of the samples were carried out with a laboratory scale rolling mill, where the contact conditions between work roll and strip are very close to actual cold rolling mill. Laboratory evaluation for dispersion, contamination, anti-oil stain property and residual carbon, etc. were carried out with several testers such as longterm circulation tester, Coulter counter and Conradson tester. A new high speed cold rolling oil with good lubricity and mill cleanness property was developed compared with the previously developed rolling oil.

The Study of Drilling Technology and Field Cases for Preventing A Lost Circulation in Fractured Reservoirs (균열저류층에서 이수손실방지를 위한 시추기술 및 현장사례 연구)

  • Kim, Hyun Tae;Hong, Si Chan;Yoon, Jae Pil;Park, Yong Chan
    • Economic and Environmental Geology
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    • v.49 no.1
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    • pp.63-75
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    • 2016
  • The ratio of fractured reservoir is very high in oil & gas fields around the world. The demand of drilling technology for fractured reservoir is expected to increase continuously if oil and gas prices are economical. The purpose of the review study is to help operator or driller in selecting of proper drilling technology for preventing a lost circulation in the fractured formation. In order to achieve this goal, fractured reservoir(formation) they are classified into partial lost circulation formation and total lost circulation formation. In case of partial lost circulation formation, the drilling problem can be solved by using LCM(lost circulation material) mud additive and squeezing cement. For shallow depth, total lost circulation formation can be drilled safely and economically with casing drilling method. Also, for deeper depth, problems of total lost circulation in formation can be solved by applying mud cap, which is one of the drilling methods. This was confirmed through field application such as Italy's Medusa-1 field and Qatar's North field.

Injection Molding of High Aspect Ratio Nano Features Using Stamper Heating/Cooling Process (스탬퍼 가열/냉각을 이용한 고세장비 나노 구조물 성형)

  • Yoo, Y.E.;Choi, S.J.;Kim, S.K.;Choi, D.S.;Whang, K.H.
    • Transactions of Materials Processing
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    • v.16 no.1 s.91
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    • pp.20-24
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    • 2007
  • Polypropylene substrate with hair-like nano features(aspect $ratio{\sim}10$) on the surface is fabricated by injection molding process. Pure aluminum plate is anodized to have nano pore array on the surface and used as a stamper for molding nano features, The size and the thickness of the stamper is $30mm{\times}30mm$ and 1mm. The fabricated pore is about 120nm in diameter and 1.5 um deep. For molding of a substrate with nano-hair type of surface features, the stamper is heated up over $150^{\circ}C$ before the filling stage and cooled down below $70^{\circ}C$ after filling to release the molded part. For heating the stamper, stamper itself is used as a heating element by applying electrical power directly to each end of the stamper. The stamper becomes cooled down without circulation of coolant such as water or oil. With this new stamper heating method, nano hairs with aspect ratio of about 10 was successfully injection molded. We also found the heating & cooling process of the stamper is good for releasing of molded nano-hairs.

Effects of Foot Bath and Spray Application of Peppermint and Grapefruit Essential Oils on Lower Extremity Edema, Pain, and Fatigue (페퍼민트, 그레이프후룻 에센셜 오일을 이용한 족욕 또는 스프레이 적용이 하지부종, 통증 및 피로에 미치는 효과)

  • Han, Ari;Kim, Juri;Hur, Myung-Haeng
    • Journal of the Korea Convergence Society
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    • v.13 no.1
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    • pp.375-386
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    • 2022
  • Work involving standing or walking for a long time can cause swelling, pain, and fatigue in the lower extremities due to the effect of gravity on the circulation of the body. This study aimed to confirm the effects of aromatherapy essential oils, as a complementary and alternative therapy, on lower extremity edema, pain, and fatigue when applied as a foot bath or spray. The study was conducted after daytime work over two consecutive days on nurses who volunteered at the E University Hospital in D Metropolitan city between 15 August 2018 and 11 October 2018. This randomized controlled study. The foot bath group received a foot bath in 9 L of water containing 0.5 ml of essential oil blended with grapefruit and peppermint in a 1:1 ratio. The spray group received the same solution in 3% dilution in the form of a spray. Edema was assessed by measuring calf and ankle circumference, while pain and fatigue were evaluated using a numerical rating scale. Data were analyzed by ANOVA and repeated-measures ANOVA. The calf circumference in the foot bath and spray groups significantly reduced compared to that in the control group (F = 14.053, p <.001) after the interventions. Lower extremity pain (F = 42.497, p < .001) and fatigue (F = 20.641, p < .001) also significantly reduced in the foot bath and spray groups compared to those in the control group after the interventions. Foot bath is recommended to relieve swelling and pain in the lower extremities, and aroma spray is highly recommended considering the ease of application.