• 설비공학논문집
• /
• 제5권4호
• /
• pp.306-317
• /
• 1993

In this study, a performance comparison of scroll compressor for various refrigerants(CFC-12, HCFC-22 and HFC-134a) has been numerically carried out. The thermodynamic properties have been calculated by using the recent experimental equations and the performance has been investigated qualitatively at the same geometric specifications and operating conditions of scroll compressor. The results are as follows; HFC-134a has the highest compression ratio of 5.40. The mass flow rate of HCFC-22, which affects the cooling capacity of refrigerant system, is higher than that of other refrigerants. HFC-134a has the highest adiabatic efficiency in comparison with CFC-12 and HCFC-22.

• Tribology and Lubricants
• /
• 제3권2호
• /
• pp.68-71
• /
• 1987

This paper deals with some thermal Characteristics of journal bearing such as the behaviour of the maximum bearing temperature, the lubricant's carry-over in the inlet region and so on. Temperatures of the bearing and the lubricants being supplied and discharged were measured along with shaft speed and bearing load. The results showed that with the increase of the Shaft speed, the maximum temperature rose at any shaft speed at a defferent rate of change defending on the flow regime of the lubricant film. And the lower eccentricity ratio is the more lubricant's carry-over occur. Additionally it was partially proved that the oil discharge temperature and the maximum temperature changed in quite different each other.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
• /
• pp.329-331
• /
• 2000

A marine bacterium, Pseudomonas aeruginosa BYK-2 KCTC 18012P was immobilized in modified polyvinyl alcohol for the continuous production of rhamnolipids. The stability of rhamnolipids production, the mechanical strength of beads and the scanning electron microscope of immobilized cell were determined in a repeated batch culture. The rhamnolipids production was maintained $80{\sim}90%$ stability of initial production, and the mechanical strength also was stable during the repeated batch culture more than 14 cycles. In the case of SEM studies, the internal distribution pattern of the cell entrapped in modified PVA beads was observed. On the basis of optimal conditions, the continuous culture was investigated in 1.8L air lift bioreactor. The result suggested 0.1g/h rhamnolipids was obtained from 1%(v/v) fish oil continuously in conditions of 1.2L working volume, 0.5vvm and 20ml/h flow rate.

• 한국수소및신에너지학회논문집
• /
• 제19권3호
• /
• pp.226-231
• /
• 2008

Cu/Fe/$Al_2O_3$ granules with various sizes have been prepared by a combination of sol-gel and oil drop method for the use in sulfur trioxide decomposition, a subcycle in thermochemical sulfur-iodine cycle to split water in the hydrogen and oxygen. The size of composite granules have been mainly changed by the flow-rate of the gel mixture before dropping in the synthesis. The structural properties of the samples were comparable with granule size. In the reaction, the catalytic activity was enhanced by decreasing size in the entire reaction temperature ranges.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문초록집
• /
• pp.399.1-399
• /
• 2002

This paper describes the fluttering characteristics of the upper pad in a tilting pad journal bearing(6-pad, LOP type) using a steam turbine. In order to investigate the phenomena of the pad fluttering experimentally, the absolute vibration of the upper pads, the relative vibration between the bearing and the shaft and the circumferential distribution of the film thickness are measured under the different values of oil supply flow rate, shaft speed and bearing load. (omitted)

• 유공압시스템학회논문집
• /
• 제1권3호
• /
• pp.14-19
• /
• 2004

The Direct Drive Valve used in this study contains a pressure-feedback-loop in itself, then it can eliminate nonlinearity such as the square-root-term in flow rate calculation and the change of bulk modulus of hydraulic oil. In this study, assuming that the dynamic characteristic of the DDV is modelled as a first order lag system, an parameter identification method using the input data and the output data is applied to obtain DDV's mathematical model. Then, a state feedback controller was designed to implement the force control of hydraulic system, and the control performance was evaluated.

• Journal of Advanced Marine Engineering and Technology
• /
• 제31권8호
• /
• pp.932-938
• /
• 2007

The interaction between adherent molecules and gas molecules was modeled in molecular scale and simulated by the molecular dynamics method in order to understand the evaporation and removal processes of adherent molecules on metallic surface using high temperature gas flow. Methanol molecules were chosen as adherent molecules to investigate effects of adhesion quantify and gas molecular collisions because the industrial oil has too complex structures of fatty acid. The effects of adherent quantify, gas temperature and surface temperature for the evaporation rate of adherent molecules and the molecular removal mechanism were investigated and discussed in the present study. Evaporation and removal rates of adherent molecules from metallic surface calculated by the molecular dynamics method showed the similar dependence on surface temperature shown in the experimental results.

• Applied Science and Convergence Technology
• /
• 제26권1호
• /
• pp.1-5
• /
• 2017

The spurt vacuum pump is widely used to transfer sludge and slurry, and to control flow rate in a variety of processing fields, such as the oil, chemical, and fiber industries. The efficiency of the pump depends on the design parameters of the impeller, such as the number of blades, and the blade angle. In this study, the effect of the configuration of the impeller discharge angle of a spurt vacuum pump, which influences total head, shaft power, and efficiency, was numerically investigated using the commercial code, ANSYS CFX ver. 16.1. In addition, the performance of the pump was evaluated on the basis of the correlations between the total head, pump efficiency, and pressure distribution.

• 동력기계공학회지
• /
• 제19권6호
• /
• pp.54-59
• /
• 2015

This paper is a numerical study on the correlation of leakage by the variation of operating temperature and orifice diameter applying to hydrostatic bearing in hydraulic actuator. Compared with Brackbill and Kandlikar experimental paper to verify the validity of the numerical analysis technique of the present study, we derive the result that the results of experiments and numerical analysis to match very well. CFD analysis program were analyzed using a commercial code FLUENT V14.5. Inlet and outlet, were applied pressure conditions, the main variables of the analysis is temperature and the orifice inner diameter. The analysis results, pressure value has decreased as the oil temperature and the orifice diameter increases.

• Tribology and Lubricants
• /
• 제18권1호
• /
• pp.55-60
• /
• 2002

In many dynamic systems, there are unwanted oscillation which may arise the reduction of performance. Especially in low sliding speed condition, the stick-slip is an important issue because it because unstable motion as well as inaccurate position control in the system. Most previous works on the stick-slip are, however, only concerned with simple modeling under the condition of constant normal force. The normal force and the amount of hydraulic oil are variable with a cylinder stroke in the telescopic boom. This paper presents the pressure variations during stick-slip with the cylinder of telescope boom. Pressure variations by stick-slip has a similar pattern to that of single mass-spring model. The stick-slip is gradually decreased by means of increased flow rate.