• Journal of the Korean Solar Energy Society
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• v.23 no.2
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• pp.71-79
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• 2003

The goal of this paper is to measure and compare the performance of solar heat pump for refrigerants. To accomplish the goal, solar heat pump with aluminum roll bond type evaporator and indoor heat exchanged(condenser) was built. The test results showed that the COP and heating capacity of HFC-32/125/134a(23/25/52 wt%, $CH_2F_2/CF_3CHF_2/CF_3CH_2F$) were higher than those of HCFC-22$(CHClF_2)$. A study proved that best conditions to use heating system that is about $40m^2$ and $80m^2$. The COP range of the whole system was from 4 to 6 according to the solar collector's area variation. Hydrochlo-rofluorocarbon HCFC-22$(CHClF_2)$ is included in the compound to be controlled. HFC-32/125/134a(23/25/52 wt%, $CH_2F_2/CF_3CHF_2/CF_3CH_2F$) is the most suitable replacement HCFC-22$(CHClF_2)$ in solar heat pump application. The solar heat pump system was designed to show the best efficiency that the room temperature make $18\sim20^{\circ}C$ and $23\sim25^{\circ}C$ in Seoul during the fall season.

• Journal of Life Science
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• v.22 no.5
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• pp.671-680
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• 2012

Three kinds of dietary composites-R+T, R+F, and R+TF-were combined in green tea (T), dietary fiber (F), and green tea dietary fiber mixture (TF) to red garlic extract (RG), respectively. The effects of their diets on anti-obesity were investigated $in$ $vitro$ and $in$ $vitro$ in obese rats induced high fat-cholesterol. In $in$ $vivo$ rats, the total phenolic content of the R+T and R+TF was 1.9~2.0 times higher, and their total cholesterol adsorption was 9.5~11.5 times higher than that of RG. $In$ $vivo$, male Sprague-Dawley rats were divided into 6 groups (Normal, HFC, HRG, HR+T, HR+F and HR+TF). Afterwards, the diets of the HRG, HR+T, HR+F, and HR+TF groups were supplemented with 1% of RG and its dietary composites (R+T, R+F, and R+TF) for 4 weeks, respectively. The final body weight of the HRG, HR+T, HR+F, and HR+TF groups decreased significantly compared to the group fed high fat-cholesterol (HFC), but the food efficiency ratio was not significantly different from the HFC group. The liver weight of the HFC group doubled compared to the normal group, whereas that of HR+T and HR+TF groups decreased significantly. The weight of visceral and epididymal fat decreased significantly in the groups fed the composites compared to the HFC group. The obesity index of HR+TF group decreased significantly only when compared to the HFC group. The serum lipid profile such as total lipids, cholesterol, triglyceride, LDL- and VLDL-cholesterol, as well as the atherogenic index and cardiac risk factors decreased drastically in all experimental groups compared to the HFC group, and the levels of HR+T, HR+F and HR+TF groups were a similar trend. GPT activity was not significantly different among the groups fed the composites, and it decreased significantly in the HRG group. The content of the lipid peroxide level decreased significantly in the HRG group and in the groups fed the composites, compared to the HFC group. Serum antioxidant activity was the highest in the HR+T group. We suggest that the hypolipidemic and anti-obesity effect of the RG composites, achieved by mixing green tea extract and/or dietary fiber, was due to their total phenolic content and total cholesterol adsorption effect.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.22-33
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• 2011

An induction motor operated with a conventional direct self controller(DSC) shows a sluggish response during startup and under changes of torque command. Fuzzy logic controller(FLC) is used in conjection with DSC to minimize these problems. A FLC chooses the switching states based on a set of fuzzy variables. Flux position, error in flux magnitude and error in torque are used as fuzzy state variables. Fuzzy rules are determinated by observing the vector diagram of flux and currents. This paper proposes hybrid fuzzy controller for direct torque control(DTC) of induction motor drives. The speed controller is based on adaptive fuzzy learning controller(AFLC), which provide high dynamics performances both in transient and steady state response. Flux position, error in flux magnitude and error in torque are used as FLC state variables. The speed is estimated with model reference adaptive system(MRAS) based on artificial neural network(ANN) trained on-line by a back-propagation algorithm. This paper is controlled speed using hybrid fuzzy controller(HFC) and estimation of speed using ANN. The performance of the proposed induction motor drive with HFC controller and ANN is verified by analysis results at various operation conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.472-483
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• 1999

The evaporation heat transfer and pressure drop characteristics for HFC-l34a in flat plate type heat exchangers with enhanced beads were experimentally investigated. Three plate type evaporators with different geometric condition of U-turn area were tested. Mass fluxes were tested over the range of 83kg/$m^2$s to 166kg/$m^2$s, and heat fluxes were varied from 4㎾/$m^2$ to 12㎾/$m^2$. Evaporation temperature was 5$^{\circ}C$ with inlet qualities of 0.1 to 1.0. There was no notable difference in the heat transfer coefficient by geometric variation of U-turn area, but the third plate with cross-ribbed channel at U-turn area was better than others in the evaluation using volume goodness factor comparison. Also, the mixtures of HFC-l34a and PAG oil was tested to determine oil effects on heat transfer and pressure drop. As oil concentration was increased, heat transfer coefficient was increased by 22~48% up to the 3wt.%, but decreased by 14~22% at the 4wt.%. The pressure drop was increased by the maximum of 100% as oil concentration was increased.

• Journal of Climate Change Research
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• v.7 no.3
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• pp.283-288
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• 2016

In this study, applicability of GHG ETS Offset Program in Korea for a refrigerant sector was analyzed by reviewing foreign management policy and project status in progress related to refrigerants in the disposal stage. In order to derive the implication of the domestic Offset Program, it was looked into approved offset projects and certified offset credits current state in Korea. Offset Program has approved 22 methodologies up to the present, so it is necessary to enhance the accessibility to GHG reduction in various industrial sector including the refrigerant sector by developing appropriate methodologies. In this study firstly, it was investigated that management regulation of countries are managing the refrigerants in the disposal stage such as United States, Japan, Australia. Secondly, of CDM methodologies there were two methodologies associated with the refrigerant reduction(treatment), which were decomposition HFC-23 and destruction of HFC-134a. Also there were a non-registered methodology about destruction of HFC-134a of end of life vehicles. Lastly, in California according to Compliance Offset Program, there was Compliance Offset Protocol in ODS Projects that provided eligible conditions. Based on the review, it was examined the possible conditions for domestic offset project for refrigerant sector

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.2
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• pp.210-218
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• 1998

Experimental results for forced convection condensationof Refrigerant-22 and ternary Refrigerant-407c(HFC-32/125/134a 23/25/52 wt%) considered as a substitute R-22 inside horizontal micor-fin tubes are presented. The test section was horizontal double-tubed counterflow condenser with a length 4000 mm micro-fin tube having 9.53 mm OD., 0.2 mm fin height and 60 fins. The refrigerants R-22 and R-407c were cooled by a coolant circulated in a surrounding annulus. The range of parameters of mass velocity was varied from 102.1 to 301.0kg/($\textrm{m}^{2}.s$) with inlet quality 1.0. Both refrigerant R-22 and its alternative refrigerant R-407c were tested within the same range of parameters. At the given experimental conditions for R-22 and R-407c the pressure drops for R-407c were considerably higher than those for R-22 at micro-fin tubes. Over the mass velocity range tested the PF(penalty factor)was lower than the increasing ratio of heat transfer area by fins. Based on the data correlation was proposed for predicting the frictional pressure drops for R-22 and R-407c for a duration of condensation inside a horizontal micro-fin tube.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.50-56
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• 2008

Experimental results for forced convection condensation of Refrigerant-22 and ternary Refrigerant-407C(HFC-32/125/134a 23/25/52 wt%) which is being considered as a substitute R-22 inside a horizontal micro-fin tube are presented. The test section was horizontal double-tube counterflow condenser with a length 4,000 mm micro-fin tube, having 8.53 mm ID, 0.2 mm fin height and 60 fins. The range of parameters of mass velocity were varied from 102.1 to 301.0 kg/(m2.s) and inlet quality 1.0. At the given experimental conditions. the average heat transfer coefficients for R-407C were lower than that for R-22 at a micro-fin tube. Over the mass velocity range tested. the PF(penalty factor) for R-22, R-407C were lower than the increasing ratio of heat transfer area by fins, and the EF(enhancement factor) for R-22, R-407C were higher than the increasing ratio of heat transfer area by fins.

• Clean Technology
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• v.22 no.3
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• pp.154-160
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• 2016

For any conceivable desalination process using the gas hydrate formation, the kinetics has to be one of the most important parameters from the economic point of view. We thus were to improve the kinetics of the R-134a (also known as HFC-134a) gas hydrate formation by using promoters and three different kinds of edible surfactants were selected for the desalination process targeted to produce potable water; κ-carrageenan, lecithin, and polysorbate 80 among anionic, amphoteric, and nonionic surfactants, respectively. Then, the kinetics change of the R-134a hydrate formation was monitored by varying the surfactant concentration. Experimental results demonstrated that the rate of R-134a hydrate formation increases with the addition of edible surfactants in general and the effect as a promotor has an order of polysorbate 80 > κ-carrageenan > lecithin. As a supportive measure, the atomic charges of each surfactant were calculated by using a DFT (density functional theory)-based molecular modeling and the results showed a positive relationship between the promotor effect of each surfactant and the number of oxygens available for hydrogen bonding and the negativity of their atomic charge values.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.715-722
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• 2007

Experiments were conducted for the investigation of pressure drop inside horizontal micro-fin tubes during the condensation of R-22 and ternary refrigerant. R-407C(HFC-32/125/134a 23/25/62 wt%) as a substitute of R-22. The condenser is a double-tube and counterflow type heat exchanger which is consisted with micro-fin tubes having 60 fins with a length of 4000mm, outer diameter of 9.53mm and fin height of 0.2mm. The mass velocity varied from 102.1 to $301.0kg/(m^2{\cdot}s)$ and inlet quality was fixed as 1.0. From the experimental results. the pressure drop for R-407C was considerably higher than that for R-22. The value of PF(penalty factor) for both of refrigerants was not bigger than the ratio of micro-fin tube area to smooth tube area. Based on the experimental data. correlation was Proposed for the prediction of frictional pressure drop during the condensation of R-22 and R-407C inside horizontal micro-fin tubes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.3
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• pp.315-324
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• 2000

R-410A, R-407C, and four refrigerant mixtures composed of R-32, R-l34a, R-l43a, R-l52a, R-600(butane), and R-600a(isobutane) were tested in an attempt to replace R-22 used in most of the residential air conditioners. The performance evaluation was carried out in a psychrometric calorimeter test facility using a residential spilt type air conditioner under the KS rating conditions. Except for the lubricant and hand-operated expansion valve, the other parts of the air conditioner were the same with the commercial system. Performance characteristics were measured; COP, capacity, compressor power, and VCR. R-410A was shown to have 5.5% higher COP and 3.5% lower capacity than R-22. R-32/134a/600a (42.8/ 46.0/11.2 wt%) mixture have the best performance among the four refrigerant mixtures composed of hydrofluorocarbon and hydrocarbon. This inixture have 3.0% lower COP and 1.6% lower capacity than R-22.