• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.2
• /
• pp.109-117
• /
• 2009

In this study, thermodynamic performance of R430A is examined both numerically and experimentally in an effort to replace HFC134a used in the refrigeration system of domestic water purifiers. Even though HFC134a is used predominantly in such a system these days, it needs to be phased out in the near future in Europe and most of the developed countries due to its high global warming potential. To solve this problem, cycle simulation and experimental measurements are carried out with a new refrigerant mixture of 76%R152a124% R600a using actual domestic water purifiers. This mixture is numbered and listed as R430A by ASHRAE recently. Test results show that the system performance with R430A is greatly influenced by the amount of charge due to the small internal volume of the refrigeration system of the domestic water purifiers. With the optimum amount of charge of 21 to 22 grams, about 50% of HFC134a, the energy consumption of R430A is 13.4% lower than that of HFC 134a. The compressor dome and discharge temperatures and condenser center temperature of R430A are very similar to those of HFC134a at the optimum charge. Overall, R430A, a new long term environmentally safe refrigerant, is a good alternative for HFC134a requiring little change in the refrigeration system of the domestic water purifiers.

• Korean Journal of Exercise Nutrition
• /
• v.16 no.2
• /
• pp.85-92
• /
• 2012

This study was conducted to examine the possibility of Salicornia herbacea L. powder as a functional food beneficially affecting carbohydrate metabolism and antioxidant capacity. Twenty-four, 6-week old, maleSprague-Dawleyrats were classified into three groups: normal diet control (CON), high-fat diet control (HFC) and high fat diet + Salicornia herbacea L. (SHF). Related feed was provided to each group for 4 weeks. Weight gain rate increased most in the HFC rats, and the concentration of glucose was significantly high in both the HFC and SHF groups, compared to the CON group. The SHF group showed a significantly high expression rate of Glut 4 (21.36%), compared to the CON and HFC groups. The glycogen content in muscle was significantly high in both the HFC and SHF groups, compared to the CON group. There were significant differences in the malondialdehydecontent in muscles between the groups, with the content in the CON and HFC groups being significantly higher than the SHF group. All the groups showed a similar tendency to each other in the liver tissue as well. Concerning the expression of Cu,Zn-super oxide dismutase andglutathione peroxidaseproteins, the SHF group was significantly higher than the CON and HFC groups. Overall, the experiment result above implies a possibility that an intake of Salicornia herbacea L. powder can regulate weight by decreasing the weight gain rate, further suggesting its effectiveness as a functional food before exercise by increasing the energy storage capacity and antioxidant capacity.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.46 no.9
• /
• pp.1035-1044
• /
• 2017

This study was carried out to investigate the effects of freeze-dried garlic powder (FDGP) on the lipid metabolism in rats fed a high fat-cholesterol (HFC) diet for 4 weeks to induce hyperlipidemia. The rats were divided into the following four experimental groups: normal diet group (NC), HFC diet group (HFC), HFC+FDGP 5 mg/100 g body weight (BW) group (FGT-1), and HFC+FDGP 15 mg/100 g BW group (FGT-2). Body weight gains and food efficiency ratios were significantly lower in the FGT groups compared to the HFC group, and the food intake was not significantly different in all experimental groups. Serum total lipid, triglyceride, and total cholesterol levels were significantly lower in the FGT groups compared to the HFC group. Total lipid content of the FGT-2 group was reduced by about 9% and 12% compared to the FGT-1 group and HFC group, respectively. The FGT groups also showed about 10% reductions low density lipoprotein (LDL)-cholesterol, atherogenic index (AI), and cardiac risk factor (CRF) compared to the HFC group. Liver function index (alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase) and lipid components were significantly lower in the FGT groups compared to the HFC group. Thiobarbituric acid reactive substances content of serum and liver tissue was reduced in the FGT groups compared to the HFC group, and was lower in the FGT-2 group compared to the FGT-1 group in serum. Antioxidant activities in serum and liver tissue were in the order of FGT-2> FGT-1> HFC group, significantly. In conclusion, FDGP effectively reduced the lipid components of serum and liver tissue. Feeding FDGP did not increase high density lipoprotein-cholesterol, but reduced LDL-cholesterol content, AI and CRF, especially. This shows that FDGP, will be effective in preventing and improving cardiovascular diseases such as arteriosclerosis and hyperlipidemia.

• Proceedings of the Korea Society of Information Technology Applications Conference
• /
• 2003.06a
• /
• pp.63-64
• /
• 2003

• 한국ITS학회:학술대회논문집
• /
• 2002.11a
• /
• pp.116-119
• /
• 2002

• The Monthly Technology and Standards
• /
• s.1
• /
• pp.64-68
• /
• 2002

• Journal of Broadcast Engineering
• /
• v.16 no.5
• /
• pp.834-845
• /
• 2011

Massive broadcasting contents such as UHD(Ultra High Definition) TV which requires multi-channel capacity for transmission has been introduced in recent years. A transmission scheme with channel bonding has been considered for transmission of massive broadcasting contents. In HFC(Hybrid Fiber Coaxial) networks, DOCSIS 3.0(Data Over Cable Service Interface Specification 3.0) has already applied channel bonding schemes for up/downstream of data service. A method unlike DOCSIS 3.0 is required to introduce a channel bonding scheme in the broadcasting service having unidirectional transmission with a downstream. Since a massive broadcasting content requires several channels for transmission, VBR(Variable Bit Rate) transmission has been emerging for the bandwidth efficiency. In addition, research on channel allocation and resource scheduling is required to guarantee QoS(Quality of Service) for the broadcasting service based on VBR. In this paper, we propose a transmission method for mass broadcasting service in HFC network and show the UHD transmission simulator developed to evaluate the performance. In order to evaluate the performance, we define various scenarios. Using the simulator, we assess the possibility of channel bonding and VBR transmission for UHD broadcasting system to provide mass broadcasting service efficiently. The developed simulator is expected to contribute to the efficient transmission system development of mass broadcasting service.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.8
• /
• pp.613-619
• /
• 2006

The objectives of this paper are to study the characteristics of heat transfer for enhanced tubes (19.05 mm) used in the condenser with high saturation temperatures and to provide a guideline for optimum design of a condenser using HFC134a. Three different enhanced tubes are tested at a high saturation temperature of $59.8^{\circ}C$ (16 bar); a low-fin and three turbo-C tubes.. The refrigerant, HFC134a is condensed on the outside of the tube while the cooling water flows inside the tube. The film Reynolds number varies from 130 to 330. The wall subcooling temperature ranges from $2.7^{\circ}C$ to $9.7^{\circ}C$. This study provides experimental heat transfer coefficients for condensation on the enhanced tubes. It is found that the turbo-C(2) tube provides the highest heat transfer coefficient.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.8 no.2
• /
• pp.177-186
• /
• 1996

The characteristics of the flow of pure HFC refrigerants(R32, R125, and R134a) and their mixtures through capillary tubes were investigated experimentally. Two capillary tubes with 1.2mm and 1.6mm inner diameter and 1.5m length were adopted as test sections. Mass flow rates and temperatures and pressures were measured for several condensing temperatures and degrees of subcooling at capillary tube inlet. The effects of the condensing temperature, inner diameter of capillary tube, and subcooling on the mass flow rate of refrigerants were discussed, and the mass flow rates of HFC refrigerants were compared with that of R22. The pressure and temperature distributions along the capillary tube compared with that of R22. The pressure and temperature distributions along the capillary tube show that there is a metastable equilibrium state in the flow through the tube. Underpressure for vaporization increases as refrigerant mass flux increases and inlet subcooling decreases. Empirical correlation was suggested to predict underpressure for vaporization of the HFC refrigerants.

• Fire Science and Engineering
• /
• v.16 no.3
• /
• pp.16-25
• /
• 2002

For Freon-23, a conventional extinguished agent regulated by Montreal Protocol and HFC-227ea, its alternative, the empirical equations were correlated in terms of saturated pressure, density, viscosity, enthalpy and surface tension. They were obtained by regression analysis from the experimental data in the literature. The empirical equations of saturated pressure were expressed as the second and third order function of temperature. The empirical equation of density was expressed as compressibility factor and saturated pressure by a function of temperature. The empirical equation of viscosity was formulated as a power function. Heat capacities as well as enthalpies were well fitted by empirical form of the second-order temperature. Finally, surface tension simply has linear function form in terms of temperature.