• Title/Summary/Keyword: R134A

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A Study on Forced Convective Boiling Heat Transfer of Non-Azeotropic Refrigerant Mixture R134a/R123 Inside Horizontal Smooth Tube (수평 전열관내 비공비 혼합냉매 R134a/R123의 강제대류비등 열전달에 관한 연구)

  • Lim, Tae-Woo;Han, Kyu-Il
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.3
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    • pp.381-388
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    • 2003
  • An experimental study was carried out to measure the heat transfer coefficient in flow boiling to mixtures of HFC-l34a and HCFC-123 in a uniformly heated horizontal tube. Tests were run at a pressure of 0.6 MPa and in the ranges of heat flux 1-50 kw/$m^2$, vapor quality 0-100 % and mass velocity 150-600 kg/$m^2$s. Heat transfer coefficients of mixture were less than the interpolated values between pure fluids both in the low quality region where the nucleate boiling is dominant and in the high quality region where the convective evaporation is dominant. Measured data of heat transfer are compared to a few available correlations proposed for mixtures. The correlation of Jung et. al. satisfactorily predicted the present data, but the data in lower quality was overpredicted and underpredicted the high quality data. The correlation of Kandlikar considerably underpredicted most of the data. and showed the mean deviation of 35.1%.

An experimental study on floor heating panel using a pulsating heat pipe (진동형 히트파이프를 이용한 바닥 난방패널 개발에 관한 연구)

  • Lim, Suk-Jin;Lee, Sung-Ho;Kim, Jeung-Hoon;Kim, Jong-Soo
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.352-356
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    • 2006
  • As a basic study to develop heating panel, the purpose of this study was to know possibility as a floor heating panel. We investigated working conditions and performance of pulsating heat pipe. Tests were conducted under the next conditions; Working fluid were R-22 and R-134a, charging ratio 40% and 50%, temperature of inlet water $60^{\circ}C$ and $70^{\circ}C$, flow rates $1{\sim}3kg/min$. The experimental results indicate that the pulsating heat pipe charged 50% showed better performance than 40%, R-22 is more suited to the working fluid than R-134a, and it has a possibility which can be applied to floor heating panel using a pulsating heat pipe.

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Exergy Analysis of Vapor Compression Cycle Driven by Organic Rankine Cycle (유기랭킨사이클로 구동되는 증기압축냉동사이클의 엑서지 해석)

  • Kim, Kyoung Hoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.12
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    • pp.1137-1145
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    • 2013
  • In this study, exergy analysis of a thermally activated refrigeration cycle, a combined organic Rankine cycle (ORC), and a vapor compression cycle (VCC) were conducted. It is considered that a system uses a low-temperature heat source in the form of sensible heat, such as various renewable energy sources or waste heat from industries, and one of eight working fluids: R143a, R22, R134a, propane, isobutane, butane, R245fa, or R123. The effects of turbine inlet pressure and the working fluid selected on the exergy destructions (anergies) at various system components as well as the COP and exergy efficiency of the system were analyzed and discussed. The results show that the component of the greatest exergy destruction in the system varies sensitively with the turbine inlet pressure and/or working fluid.

Feasibility of a Solar Thermal Organic Rankine Cycle Power Plant for an Apartment Complex with Aspen Plus® (ASPEN PLUS®를 이용한 태양열 유기랭킨사이클 열병합 발전시스템의 공동주택 적합도 분석)

  • Im, Seokyeon;Kim, Hyung-Geun;Yu, Sangseok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.4
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    • pp.317-324
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    • 2015
  • In this study, a solar thermal system is designed to provide hot water and electricity for improvement of solar thermal energy availability in an apartment complex. The electricity is generated with Organic Rankine Cycle (ORC) by the solar thermal energy. R134a, R141b and R245fa are selected for operating fluid of the solar thermal ORC system. ORC with R245fa shows the best performance based on the variation of pressure. The irreversibility of component showed that the technology advance of the evaporator ensures a performance improvement. The sensitivity study results indicate that the turbine performance is most effective way to improve the performance of ORC system. An economic analysis showed that approximately 50% more income could be achieved by a solar thermal ORC system with a hot water supply.

Effect of a Turbo-Expander for Regeneration in the Expansion Process (팽창과정에서의 터보엑스펜더 영향에 관한 연구)

  • Cho, Chong-Hyun;Cho, Bong-Soo;Kim, Chae-Sil;Cho, Soo-Yong
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.157-160
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    • 2006
  • A turbo-expander is developed for the regeneration in the expansion process. The turbo-expander operates in the partial admission and supersonic flow, and an axial-type single stage turbine is applied to the turbo-expander. Its outer diameter is 82mm and the operating gas is R134a. A 15kW reciprocating compressor is applied in this experiment and the turbo-expander is installed in the expansion process instead of the commonly using expansion valve. Two supersonic nozzles are applied for the expansion process. The high speed of R 134a after passing the supersonic nozzles gives the impulse force to the turbo-expander and some powers are generated on this process. A generator is installed at the end of the turbo-expander shaft. The generating output power from the turbo-expander is controlled by the power controller. Pressures and temperatures are measured on the lines for the performance investigation. More than 600W/(kg/sec) are generated in this experiment.

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A Study of Flow Condensation Inside Mini-Channels with Circular and Rectangular Cross Section (원형 및 사각단면의 미세채널내 흐름응축 열전달 연구)

  • Shin, Jeong-Seob;Kim, Moo-Hwan
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1458-1463
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    • 2004
  • By using unique experimental techniques and careful construction of the experimental apparatus, the characteristics of the local heat transfer were investigated using the condensing R134a two-phase flow, in horizontal single mini-channels. The circular channels ($D_h=0.493$, 0.691, and 1.067 mm) and rectangular channels ($D_h=0.494$, 0.658, and 0.972 mm) were tested and compared. Tests were performed for a mass flux of 100, 200, 400, and 600 $kg/m^2s$, a heat flux of 5 to 20 $kW/m^2$, and a saturation temperature of $40^{\circ}C$. In this study, effect of heat flux, mass flux, vapor qualities, hydraulic diameter, and channel geometry on flow condensation were investigated and the experimental local condensation heat transfer coefficients are shown. The experimental data of condensation Nusselt number are compared with existing correlations.

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Cloning of Autonomously Replicating Sequence from Phaffia rhodzyma

  • Chun, Soon Bai;Seung Hee Chun
    • Journal of Microbiology and Biotechnology
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    • v.5 no.6
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    • pp.370-372
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    • 1995
  • A Phaffia rhodozyma chromosomal fragment (approximately 3.8 kb) capable of functioning as an origin for the replication of a kanamycin resistance ($Km^r$) plasmid in S. cerevisiae was isolated by the use of origin search plasmid, pHN134. In S. cerevisiae, transformation frequencies using the plasmid pHN134 containing an autonomously replicating sequence of P. rhodozyma was 450-580 CFU/$\mu g$ DNA. The stability of the recombinant plasmid were 16-19$\%$.

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Pathways Regulating the pbgP Operon and Colistin Resistance in Klebsiella pneumoniae Strains

  • Choi, Myung-Jin;Kim, Sunju;Ko, Kwan Soo
    • Journal of Microbiology and Biotechnology
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    • v.26 no.9
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    • pp.1620-1628
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    • 2016
  • In this study, we investigated colistin resistance mechanisms associated with the regulation of the pbgP operon in Klebsiella pneumoniae, using four isogenic pairs of colistin-susceptible strains and their colistin-resistant derivatives and two colistin-resistant clinical isolates. Amino acid sequence alterations of PhoPQ, PmrAB, and MgrB were investigated, and mRNA expression levels of phoQ, pmrB, pmrD, and pbgP were measured using quantitative real-time PCR. The phoQ and pmrB genes were deleted from two colistin-resistant derivatives, 134R and 063R. We found that phoQ, pmrD, and pbgP were significantly upregulated in all colistin-resistant derivatives. However, pmrB was significantly upregulated in only two colistin-resistant derivatives and one clinical strain. pmrB was not overexpressed in the other strains. The minimum inhibitory concentration of colistin was drastically lower in both phoQ- and pmrB-deleted mutants from a colistin-resistant derivative (134R) that was overexpressing phoQ and pmrB. However, colistin susceptibility was restored only in a phoQ-deleted mutant from a colistin-resistant derivative (063R) without overexpression of pmrB. In conclusion, two different regulations of the pbgP operon may associate with the development of colistinresisant K. pneumoniae.

The Design and Performance Test of a Centrifugal Compressor for HFC-134a (대체냉매용 원심압축기의 설계 및 성능시험)

  • Sin, Jung-Kwan;Kim, Kyung-Hun
    • 유체기계공업학회:학술대회논문집
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    • 2002.12a
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    • pp.250-257
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    • 2002
  • A centrifugal compressor for HFC-l34a has been newly designed and developed. Flow analysis using commertial programs was used to evaluate performance and internal flow of the impeller, inlet guide vane and diffuser etc. and design software was developed. The compressor for HFC-l34a was also investigated experimentally to check compression performance. The calculated data coincide the test results of compressor. The data obtained in the present study are useful for design of HFC-l34a centrifugal compressors.

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