• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.829-835
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• 2013

This paper describes an analysis on exergy efficiency of proposed high-efficiency R717 OTEC power system to optimize the design for the operating parameters of this system. The operating parameters considered in this study include outlet pressure in an evaporator and high turbine, inlet pressure condenser and vapor quality at cooler outlet, respectively. The main results are summarized as follows : As the outlet pressure in an evaporator and vapor quality at cooler outlet of R717 OTEC power system increases, the exergy efficiency of this system increases, respectively. But outlet pressure in the high turbine, inlet pressure in the condenser of R717 OTEC power system increases, the exergy efficiency of this system decreases, respectively. And, incase of exergy efficiency of this OTEC system, the effect of inlet pressure in an evaporator and outlet pressure in the high turbine on R717 OTEC power system is the largest and the lowest among operation parameters, respectively.

• Food Science of Animal Resources
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• v.32 no.4
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• pp.396-403
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• 2012

This study was conducted in order to investigate the effect of storage temperature abuse on the freshness of refrigerated and frozen spent hen's meat. After a room temperature storage condition, two different storage temperature were followed: refrigeration and frozen storage. All parts of the spent hen's meats were thawed at 4 d intervals up to 3 times (2, 6, and 10 d) for 24 h. The level of bacteria on the different parts of the refrigerated and frozen meats was higher than 6 Log CFU/g under the following storage conditions: refrigerated - breast, 12 h; leg, 6 h; wing, 12 h at the $1^{st}$ analysis, frozen - breast, 12 h at the $2^{nd}$ analysis; leg, 24 h at the $1^{st}$ analysis; wing, 12 h at the $1^{st}$ analysis. The pH value for the leg meat was higher than breast and wing meats. In the color measurements, under the room temperature storage condition, lightness and redness values decreased but the yellowness increased in refrigerated meats (p<0.05). The K-value regarding refrigerated leg meats exceeded 60%, which is the threshold value to evaluate the degree of freshness, during the $1^{st}$ analysis (p<0.05). The VBN value of refrigerated leg meat was the highest and reached up to 96.93 mg%. Thus, studies regarding the possible decline in quality according to the change of storage temperature could be used in order to establish a basic database for the quality control of spent hen meat being traded with other countries.

• Korean Journal of Materials Research
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• v.28 no.8
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• pp.445-451
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• 2018

We report the structural, magnetic and magnetocaloric properties of $Sr_{1.8}Pr_{0.2}FeMo_{1-x}W_xO_6$($0.0{\leq}x{\leq}0.4$) samples prepared by the conventional solid state reaction method. The X-ray diffraction analysis confirms the formation of the tetragonal double perovskite structure with a I4/mmm space group in all the synthesized samples. The temperature dependent magnetization measurements reveal that all the samples go through a ferromagnetic to paramagnetic phase transition with an increasing temperature. The Arrott plot obtained for each synthesized sample demonstrates the second order nature of the magnetic phase transition. A magnetic entropy change is obtained from the magnetic isotherms. The values of maximum magnetic entropy change and relative cooling power at an applied field of 2.5 T are found to be $0.40Jkg^{-1}K^{-1}$ and $69Jkg^{-1}$ respectively for the $Sr_{1.8}Pr_{0.2}FeMoO_6$ sample. The tunability of magnetization and excellent magnetocaloric features at low applied magnetic field make these materials attractive for use in magnetic refrigeration technology.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.4
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• pp.463-473
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• 2006

The effect of tube diameter on heat and mass transfer characteristics of absorber in absorption chiller/heater using LiBr solution as a working fluid has been investigated by both of numerical and experimental study to develop a high performance and compact absorber. The diameter of the heat exchanger tube inside absorber was changed from 15.88mm to 12.70mm and 9.52mm. In numerical study a model of vapor pressure drop inside tube absorber based on a commercial 20RT absorption chiller/heater was performed. The effect of tube diameter, longitudinal pitch, vapor Reynolds number, longitudinal pitch to diameter ratio on vapor pressure drop across the heat exchanger tube banks inside absorber have been investigated and found that vapor pressure drop decreases as tube diameter increases, longitudinal pitch increases, vapor Reynolds number decreases and longitudinal pitch to diameter ratio increases. In experimental study, a system includes a tube absorber, a generator, solution distribution system and cooling water system was set up. The experimental results shown that the overall heat transfer coefficient, mass transfer coefficient. Nusselt number and Sherwood number increase as solution flow rate increases. In both of study cases, the heat and mass transfer performance increases as tube diameter decreases. Among three different tube diameters the smallest tube diameter 9.52mm has highest heat and mass transfer performance.

• International Journal of Air-Conditioning and Refrigeration
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• v.7
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• pp.1-10
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• 1999

In this study, a numerical analysis is made on the ice-formation for laminar water flow inside a stenotic tube. The study takes into account the interaction between the laminar flow and the stenotic port in the circular tube. The purpose of the present numerical investigation is to assess the effect of a stenotic shape on the instantaneous shape of the flow passage during freezing upstream/downstream of the stenotic channel. In the solution strategy, the present study is substantially distinguished from the existing works in that the complete set of governing equations in both the solid and liquid regions are resolved. In a channel flow between parallel plates, the agreement between the of predictions and the available experimental data is very good. Numerical analyses are performed for parametric variations of the position and heights of stenotic shape and flow rate. The results show that the stenotic shape has the great effect on the thickness of the solidification layer inside the tube. As the height of a stenosis grows and the length of a stenosis decreases, the ice layer thickness near the stenotic port is thinner, due to backward flow caused by the sudden expansion of a water tunnel. It is found that the flow passage has a slight uniform taper up to the stenotic channel, at which a sudden expansion is observed. It is also shown that the ice layer becomes more fat in accordance with its Reynolds number.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2003.10b
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• pp.2-3
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• 2003

A method for rapid propagation of mature Jack fruit was developed. Four types of explants (mature embryos, apical meristems of young seedlings, apices from mature plants and nodal segments) were used. It has been found 88% of young apical meristems produced shoots in Campbell and Durzan (CD) medium compared to 60% in Murashige and Skoog (MS) medium. Only 1/3 of them produced multiple shoots. Shoot initiation from nodal segments was very rare. Mature apices produced callus. Although removal of the sheathing cover around mature buds enhanced the shoot initiation but success rate was low in growth regulator free medium. Embryos respond to the CD medium but not to the MS medium. Embryos from seeds soaked in water for 24 hours produced shoots after 8 weeks of incubation and the success rate was 70% while embryos from dry seeds only produced roots. There was no significant effect of cold storage (refrigeration) for 7 days on shoot initiation from mature embryos (65%) but the ability for shoot induction declines with storage time (55% after 21 days of cold storage). Mature axillary buds were established in Modified Campbell and Durzan (CD) medium supplemented with 0.5mg/1 and IBA. There was a significant difference in the growth performance of shoots according to the period of the year in which explants were collected. Highest (60%) was observed in November-January period. It was only 30% when the explants were collected in February-April or May-July and decreased to 20% in August-October. The shoots produced in November-January showed a higher vigor than those produced in other months. Since Jak fruit show seasonal changes in fruit bearing and shedding of leaves, it can be suggested that the difference in growth performances of tissues cultured in artificial culture media would have been affected by endogenous rhythms.

• Food Science of Animal Resources
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• v.30 no.4
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• pp.597-602
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• 2010

In this study, pigs [n=117; (Landrace ${\times}$ Yorkshire) ${\times}$ Duroc; $64{\pm}0.5$ Kg initial body weight] were used to investigate the effect of feeding different levels of lacquer (Rhus verniciflua Stokes) meal on performance, carcass traits and quality of meat kept under refrigeration at $3{\pm}1^{\circ}C$. The pigs were randomly allotted to 3 treatments on the basis of body weight and sex and each treatment was replicated 3 times (13 pigs in each replicate). Lacquer meal in sawdust form obtained from the stem bark and heartwood of sun-dried lacquer trees was added to the grower and finisher diets at 0, 20 and 40 g/kg diet. The experimental diets were fed for 8 wk. Inclusion of lacquer meal had no influence (p>0.05) on growth performance of pigs. Improvement in carcass traits and decreased back fat thickness were noticed in pigs fed diets added with 20 and 40 g/kg lacquer meal. Longissimus muscle obtained from pigs fed lacquer meal had higher moisture and lower fat content, thiobarbituric acid reactive substances and water holding capacity. Meat from lacquer fed pigs was also darker and redder. The data indicates that lacquer meal can be incorporated up to 40 g/kg in the diet of fattening pigs without affecting growth performance. Also, lacquer meal increases carcass lean content and improves the oxidative stability of the meat.

• Journal of Mechanical Science and Technology
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• v.18 no.12
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• pp.2284-2293
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• 2004

The evaporation heat transfer coefficient h$\_$r/ and frictional pressure drop Δp$\_$f/ of refrigerant R-134a flowing in the oblong shell and plate heat exchanger were investigated experimentally in this study. Four vertical counterflow channels were formed in the oblong shell and plate heat exchanger by four plates of geometry with a corrugated sinusoid shape of a 45 chevron angle. Upflow of refrigerant R-134a boils in two channels receiving heat from downflow of hot water in other channels. The effects of the refrigerant mass flux, average heat flux, refrigerant saturation temperature and vapor quality of R-134a were explored in detail. Similar to the case of a plate heat exchanger, even at a very low Reynolds number, the flow in the oblong shell and plate heat exchanger remains turbulent. The results indicate that the evaporation heat transfer coefficient h$\_$r/ and pressure drop Δp$\_$f/ increase with the vapor quality. A rise in the refrigerant mass flux causes an increase in the h$\_$r/ and Δp$\_$f/. But the effect of the average heat flux does not show significant effect on the h$\_$r/ and Δp$\_$f/. Finally, at a higher saturation temperature, both the h$\_$r/ and Δp$\_$f/ are found to be lower. The empirical correlations are also provided for the measured heat transfer coefficient and pressure drop in terms of the Nusselt number and friction factor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.720-729
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• 1996

An analysis of convective boiling heat transfer for refrigerant mixtures is performed for an annular flow to investigate the degradation of the heat transfer rate. Annular flow is selected in this study because a great portion of the evaporator in the refrigeration and air conditioning system is known to be in the annular flow regime. Mass transfer effect due to composition difference between liquid and vapor is included in this analysis, which is considered to be one of driving forces for the mass transfer at the interface. Due to the concentration gradient at the interface the mass transfer is interfered, so is the evaporative heat transfer at the interface. The mass transfer resistance makes the interface temperature slightly higher and, as a result, the heat transfer coefficients decrease compared with those without mass transfer effects. The degradatioin of the heat transfer rate reaches its maximum at a certain composition. The composition difference between vapor core and vapor at the interface has a direct effect on the temperature difference between the vapor core and the interface and the degradation of the heat transfer rate. Correction factor $C_{F}$ for the mixture effects is added to the correlation for pure substances and the flow boiling heat transfer coefficients can be calculated using the modified equation.n.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.176-181
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• 2017

This study attempted to examine a method of anti-freezing on a plate-type heat exchanger in a low-temperature environment. Freezing condition was observed after ultrasonic waves were generated. Data were recorded to determine the optimal conditions for freezing. Ethylene glycol, which is commonly used in antifreeze formulations, was used as the brine, and the temperature was varied between -8 and $-16^{\circ}C$. The water for freezing provided by the thickness of 1-3 mm. In addition, experiments were conducted by adjusting the output to identify the changes that occurred due to the incidence of ultrasonic energy. The results of the anti-freezing effect were brine temperature, freezing thickness, and frequency band of ultrasonic waves.