• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.321-326
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• 2004

The pressure and differential pressure(DP) transmitters are used for gas flow rate calculation on the orifice gas metering system. On site, the pressure and DP transmitters are installed in a shelter to diminish the affects of environmental change such as an ambient temperature. But there has been an argument about the effectiveness of the shelter and this brought up the necessity to verify the affects of ambient temperature. These experiments were performed to verify the ambient temperature effects as observing the output of transmitters when the ambient temperature were changed from $-30^{\circ}C$ to $50^{\circ}C$. The results showed that the most of transmitters were operated in the spec range of performance criteria presented by manufacturer but the rapid change of ambient temperature could cause the larger measurement error for the DP transmitter of low span than others. Therefore the pressure and DP transmitters need to be operated and controlled within the proper range of ambient temperature.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.143-148
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• 2003

This study was experimentally performed in order to estimate the errors due to the leakage of transmitter gaugelines in the orifice flow meter for natural gas. It would be a serious problem in safety if a large quantity of leak was occurred at the tubes or fittings like valve. But in most cases the safety problems might be rarely happened because the gas leak detectors could be operated in advance and the various kinds of inspection would be also fulfilled periodically. If the leakage was occurred continuously with an undetectable amount at the gaugelines for measuring the pressure or the differential pressure(DP), the amount of leakage might be an error or an unaccounted flow(UAE). In addition if the measuring value of pressure or DP were affected by the leakage, it might also be a measurement error. The experiments were performed to estimate the amount of leakage and to check the DP changes if it exited. First, through the measurement of the air pressure changes in the airtight container connected to a transmitter with gaugelines as the time passed, the amount of leakage causing from the fittings of gaugelines was roughly estimated. As changing the leak position of the gaugeline, the leak was intentionally made to break out. The variance of DP was checked as controlling the extent of leakage and compared to no leak conditions. Consequently, under the normal maintenance conditions, the result represented that the amount of leakage causing from the gaugelines was insignificant and also the DP changes on leakage conditions were too small to cause the errors of measurements.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.160-165
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• 2004

MPA (Multi-Point Averaging) flow element is a new type of differential pressure (DP) flow-sensing device that was developed by Seojin Instech to improve the operating characteristics of the conventional Averaging Pilot Tube (APT) flow elements. Operating characteristics of a flowmeter in general can be defined in terms of measurement accuracy and range. Improvement of accuracy and expanding the range of flow measurement were the two main objectives of the development. To achieve these dual objectives several upstream and downstream pressure-sensing holes were placed in MPA flow element. During the course of the development it was found that certain arrangements of the pressure-sensing holes improved measurement accuracy but did not expand operating flow range of Averaging Pilot Tubes. Development tests were performed with water between Reynolds number of 50,000 and 1,000,000 in the four-inch test line at the Alden Research Laboratory, U.S.A. Purpose of this paper is to present the relationship between the various locations of the pressure-sensing holes and the performance characteristics of MPA flow element. Furthermore, the operating characteristics of the best performing MPA are compared with those of typical orifice and APT.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.166-171
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• 2004

The Rate-of-Loading(ROL) effect of motor operated gate valves causes a decrease in the thrust delivered at a specific torque by the actuator under dynamic flow ${\Delta}$P conditions as compared to the no-flow, static conditions. This effect needs to be studied for the quantitative evaluation of motor operated gate valve operability. This study is performed to verify the validity for the application of ROL in the evaluation of operability of motor operated gate valves for the opening stroke. The ROL is assessed on the basis of in-situ test data for the opening and closing strokes. The results show that the distribution of the ROL for the operling sake has a tendency to the negative value when DP is higher than 150psid.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1808-1811
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• 2005

The prediction of AOV(air-operated valve) performance is normally evaluated by the allowable opening thrust margin for the opening and closing stroke. However, it is not easy to carry out the dynamic test measurement for all the valves in the nuclear power plant due to the safety and operating conditions. The analysis of the available and required thrust for the valve is simulated as an alternate method to turn around this obstacle. The required air pressures to the stem displacement are discussed for differential valve pressure obtained by experiment. The result of the simulation is compared with that of the experiment. SIMULINK in MATLAB was used for the simulation and the results show good agreement with the actual test carried out with Fisher globe valve.

• Korean Journal of Food Science and Technology
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• v.29 no.6
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• pp.1119-1124
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• 1997

This study was carried out for improvement and correction of the traditional pressure variation method (PVM) in the respiration rate measurements of fresh fruits and vegetables using a microcomputer system and a differential pressure sensor. Water vapor pressure in the container was calculated by equations for psychrometric calculations. At the beginning of experimental period water vapor pressure in the container was increased and maintained constantly in the most experimental period, but was decreased dramatically after $CO_2$ scrubbing. The percentages of water vapor pressure on total differential pressure were $33{\sim}46%$ at $1^{\circ}C$, $23{\sim}45%$ at $11^{circ}C$ and $35{\sim}53%$ at $21^{\circ}C$. The differences between the respiration rates determined by gas chromatography and corrected pressure variation method (CPVM) were $0.2{\sim}0.3\;mgCO_2kg^{-1}h^{-1}$ at $1^{\circ}C$, $0.2{\sim}2.9\;mgCO_2kg^{-1}h^{-1}$ at $11^{\circ}C$ and 1.0{\sim}9.0\;mgCO_2kg^{-1}h^{-1}$ at $21^{circ}C$, while those between gas chromatography and normal pressure variation method (PVM) were $0.8{\sim}1.2\;mgCO_2kg^{-1}h^{-1}$ at $1^{\circ}C$, $3.9{\sim}11.0\;mgCO_2kg^{-1}h^{-1}$ at $11^{\circ}C$ and $8.0{\sim}32.0\;mgCO_2kg^{-1}h^{-1}$ at $21^{circ}C$, respectively. The differences of the respiration rates with CPVM were smaller than those with PVM. CPVM, therefore, were more exact and convenient method than PVM in the measurement of respiration rate of fresh produce.

• Nuclear Engineering and Technology
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• v.28 no.2
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• pp.137-149
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• 1996

The present study is to analyze an integral test, BETHSY test 6.9c, which represent loss of RURS accident under mid-loop operation. Both the pressurizer manway and the steam generator outlet plenum manway are opened as vent paths in order to prevent the system from pressurization by removing the steam generated in the core. The main purposes are to gain insights into the physical phenomena and identify sensitive parameters. Assessment of capability of CATHARE2 prediction can be established the effective recovery procedures using the code in an actual plant. Most of important physical phenomena in the experiment could be predicted by the CATHARE2 code. The peak pressure in the upper plenum is predicted higher than experimental value by 7 kPa since the differential pressure between the pressurizer and the surge line is overestimated. The timing of core uncovery is delayed by 500 seconds mainly due to discrepancy in the core void distribution. It is demonstrated that openings of the pressurizer manwey and the steam generator manway can prevent the core uncovery using only gravity feed injection. Although some disagreements are found in the detailed phenomena, the code prediction is considered reasonable for the overall system behaviors.