• Nuclear Engineering and Technology
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• 제29권6호
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• pp.488-499
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• 1997

The measurements of the moderator temperature coefficient (MTC) are performed to demonstrate that the calculational model produces results that are consistent with the measurements. Since negative MTC is also a technical specification value that may limit the cycle length, it is important to measure it as accurately as possible. In this report, preferred choice of test method depending on the time in cycle, best power indication and temperature definition in MTC calculation were determined based on the MTC test results taken during initial startup testing and at 2/3 cycle burnup in the Yonggwang nuclear power plant. The results show that the ratio and rodded methods provided good agreement with the predictions during initial startup testing. However, near end-of-cycle the depletion method gives better results, and so is suggested to be used in the MTC measurements at 2/3 cycle burnup. The use of primary Delta T power as a power indicator in the MTC calculations is highly advisable since it responds with good consistent results very quickly to changes unlike secondary calorimetric power. For the appropriate temperature definitions used in the MTC calculations, it is considered that the arithmetic average temperature measured simply by inlet and outlet thermocouples is preferred. Although volumetric average temperature provides better results, the improvement is not sufficient to compensate for the simplicity of calculations by arithmetic average temperature.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.995-1000
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• 2000

Segmentally erected prestressed concrete box girder bridges have been widely used in Korean high speed railway. Segmental erection has been accomplished along the longitudinal direction and across the depth of cross section. The cross section is similar to a composite cross section, composed of old and new segments. Because these segments have different time-dependent creep and shrinkage properties, a stress redistribution takes place during the construction period. It is the main objective in this research to investigate this behavior. An actual bridge was instrumented with 96 vibrating wire embedded type strain gauges, 6 electronic type steel strain gauges, and 75 thermocouples. Two span continuous high speed railway bridge was selected. Two points of importance, such as the midpoint of the first span and the point of interior support, along the span of the girder were chosen to monitor the time dependent behaviors for an extended period of time. The data collection was starting just after concrete girder were cast and is still going on. According to the measured results, the strain distributions across the depth of the section at midspan and interior support were not continuous and the important redistribution of stresses takes place. Thus, rational design of prestressed concrete composite box girder bridges need.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제42권1호
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• pp.9-12
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• 2016

Objectives: In this study we evaluated heat generation during the low-speed drilling procedure without irrigation. Materials and Methods: Ten artificial bone blocks that were similar to human D1 bone were used in this study. The baseline temperature was $37.0^{\circ}C$. We drilled into 5 artificial bone blocks 60 times at the speed of 50 rpm without irrigation. As a control group, we drilled into an additional 5 artificial bone blocks 60 times at the speed of 1,500 rpm with irrigation. The temperature changes during diameter 2 mm drilling were measured using thermocouples. Results: The mean maximum temperatures during drilling were $40.9^{\circ}C$ in the test group and $39.7^{\circ}C$ in the control group. Even though a statistically significant difference existed between the two groups, the low-speed drilling did not produce overheating. Conclusion: These findings suggest that low-speed drilling without irrigation may not lead to overheating during drilling.

• 한국수소및신에너지학회논문집
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• 제29권5호
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• pp.466-472
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• 2018

The investigation of cryogenic liquid pool spreading is an essential procedure to assess the hazard of cryogenic liquid usage. In this experimental study, to measure the evaporation velocity when the pool is spreading, liquid nitrogen was continuously released onto unconfined concrete ground. Almost all of the reported results are based on a non-spreading pool in which cryogenic liquid is instantaneously poured onto bounded ground for a very short period of time. A simultaneous measurement of the pool location using thermocouples and of the pool mass using a digital balance was carried out to measure the evaporation velocity and the pool radius. A greater release flow rate was found to result in a greater average evaporation velocity, and the evaporation velocity decreased with the spreading time and the pool radius.

• 대한기계학회논문집B
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• 제25권3호
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• pp.381-388
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• 2001

Presented are heat data which describe the effect of interaction between bulk flow pulsations and a vortex embedded in a turbulent boundary layer. The pulsation frequencies are 3 Hz, 15 Hz and 30 Hz. A half delta wing with the same height as the boundary layer thickness is used to generate the vortex flow. The convection heat transfer coefficients on a constant heat-flux surface are measured by embedded 77 T-type thermocouples. Spanwise profiles of convection heat transfer coefficients show that upwash region of vortex flow is influenced by bulk flow pulsations. The local heat transfer coefficient increases approximately by 7 percent. The increase in the local change of convection heat transfer coefficient is attributed to the spanwise oscillatory motion of vortex flow especially at the low Strouhal number and to the periodic change of vortex size.

• Journal of Advanced Marine Engineering and Technology
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• 제26권2호
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• pp.209-218
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• 2002

The temperature field of a counterflow non-premixed flame is investigated using thermocouples of two sizes. A thermal balance is performed on the thermocouple in order to calculate the magnitude of the radiation corrections involved. Both the thermocouple wire and bead are separately considered to be the relevant thermal surface to which convective heat transfer takes place, and from which radiation lasses occur. The flame is also simulated by using a detailed chemical kinetic mechanism in a previously developed computer code. The local thermo-physical properties of the gas mixture, required to calculate the corrections, are determined both from the simulation, and by approximating the properties of the mixture as those of molecular nitrogen at the measured temperatures. It is concluded that the thermocouple wire is the appropriate thermal surface to which radiation corrections apply, in the absence of information about the gas mixture, its properties can be reasonably approximated by those of nitrogen rm ($N_2$), and the radiation corrections are very sensitive to misalignments in the temperature and velocity fields.

• 설비공학논문집
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• 제26권6호
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• pp.269-274
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• 2014

The experimental performance evaluation of a cylindrical steam reformer with various thermal conditions has been conducted. The bottom space of the cylindrical reactor was packed with Ruthenium (Ru) catalyst. A three-segment furnace was installed to create the axially variable boundary temperature distribution. Six K-type thermocouples were inserted into the catalyst layer, and three exhaust ports were fabricated on the side wall along the flow direction. The exhausted gases at each port were analyzed by using gas chromatograph (GC) system. The experimental results showed that the reforming reaction occurs intensively in the upstream region and more hydrogen is obtained when the intake gas is sufficiently heated up through the enhanced steam reforming (SR) reaction. The axially increasing boundary temperature setup provided the maximally accumulated reforming efficiency of 74.8%, when the reactor was placed at the 3rd section of the furnace.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.191-196
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• 2007

This paper presents the measuring technique for local heat transfer coefficients using a copper sensor in a rod bundle with mixing vanes. A copper sensor consists of a cartridge heater and four pieces of thermocouple. The Heater is located at the center of the copper sensor and thermocouples measure the surface temperature of the copper sensor. Unheated copper sensor and heated copper sensor are able to measure the local heat transfer coefficient at the position where the heated copper sensor is installed. However the entire region of a rod bundle is actually not heated, the decay of local heat transfer coefficients measured represents overestimated value rather than an actual value. The calibration curve for local heat transfer coefficients is presented using the correction factor calculated by CFD.

• 설비공학논문집
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• 제18권3호
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• pp.247-253
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• 2006

In this work, pool boiling heat transfer coefficients (HTCs) of hydrocarbon refrigerants are measured from a horizontal smooth tube of 19.0 mm outside diameter. Tested pure refrigerants are Propylene, Propane, Isobutane, Butane and Dimethylether (DME). The pool temperature was maintained at saturation temperature of $7^{\circ}C$ and heat flux was varied from $10kW/m^2$ to $80kW/m^2$ with an interval of $10kW/m^2$. Wall temperatures were measured directly by thermocouple hole of 0.5 mm out-diameter, 152 mm long and inserting ungrounded sheathed thermocouples from the side of the tube. Tested results show that HTCs of Propane, Propylene are 2.5%, 10.4% higher than those of R22 while those of Butane and Isobutane are 55.2%, 44.3% lower than those of R22 respectively. For pure refrigerants, new correlation can be applied to all of CFCs, HCFCS, HFCs, as well as hydrocarbons was developed. The mean deviation was 4.6%.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.155-165
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• 1998

The resistance coefficient and heat transfer performance are studied for the turbulent water flow in a smooth coiled tube having variable curvature ratios and a corrugated-coiled tube having a ratio of coil to tube diameter of 22. Experiments are carried out for the fully developed turbulent flow of water in tube coils on the uniform wall temperature condition. This work is limited to tube coils of R/a between 22 and 60 and Reynolds numbers from 13000 to 53000. The tube having a ratio of coil to tube diameter of 27 among the 3 smooth tube coils shows the best heat transfer performance. A corrugated-coiled tube(R/a=60) shows more excellent performance than a smooth coiled tub (R/a=60) at a similar curvature ratio. The friction factor f is sensitive to changes in the velocity profile caused by a temperature gradient. Allowance was made for the pressure loss in the short inlet and outlet lengths and due to the presence of the thermocouple inlet and outlet as a result of separate experimental on a straight tube. It is to be expected that the allowance at the exit will be somewhat too low because of secondary flow effects carried over from the coil.