• Nuclear Engineering and Technology
• /
• v.28 no.6
• /
• pp.532-541
• /
• 1996

Theoretical and numerical study on heat transfer and evaporation in the vertical channel has been carried out and basic correlations have been derived for the heat transfer evaluation of PCCS. Analysis program was developed with low-Reynolds-number k-$\varepsilon$ model and surface transfer rates were calculated for the turbulent natural convection in the vertical channel. In relation to dry cooling by buoyancy-driven air, first, the system parameters which govern overall heat transfer rate are determined through the adequate nondimensionalization procedure. After comparison with existing experimental data, numerical results are used to derive heat transfer correlation by sensitivity calculations. In relation to wet cooling by falling water film, numerical analysis are carried out for evaporation process with real film surface conditions and evaporation correlation is derived through analogy concept and correction factors.

• Fire Science and Engineering
• /
• v.7 no.1
• /
• pp.11-16
• /
• 1993

Fixed temperature heat detectors that respond to the heat generated in fire plume and alarm when the temperature reaches a specified point, give a great influences to the loss of life and property according to their reaction sensitivity. In this study, hot wind tunnel tests and compartment fire experiments were performed to investigate the response time and temperature of fixed temperature heat detector. As a result, simple equations were derived which can be predicted the response time and temperature of the fixed temperature heat detector for the ramp type fire. Also other useful data, such as the effective temperature, time constant, response time index(RTI) were obtained.

• Journal of Welding and Joining
• /
• v.11 no.3
• /
• pp.34-47
• /
• 1993

Finite element models were developed for thermal and residual stress analysis for the specific welding problems. They were used to evaluate the effectiveness of the various welding heat input models, such as ramp heat input function and lumped pass models. Through the parametric studies, thermal-mechanical modeling sensitivity to the ramp function and lumping techniques was determined by comparing the predicted results with experimental data. The kinetics for residual stress formation during welding can be developed by iteration of various proposed mechanisms in the parametric study. A ramp heat input function was developed to gradually apply the heat flux with variable amplitude to the model. This model was used to avoid numerical convergence problems due to an instantaneous increase in temperature near the fusion zone. Additionally, it enables the model to include the effect of a moving arc in a two-dimensional plane. The ramp function takes into account the variation in the out of plane energy flow in a 2-D model as the arc approaches, travels across, and departs from each plane under investigation. A lumped pass model was developed to reduce the computation cost in the analysis of multipass welds. Several weld passes were assumed as one lumped pass in this model. Recommendations were provided about ramp lumping techniques and the optimum number of weld passes that can be combined into a single thermal input.

• Journal of Sasang Constitutional Medicine
• /
• v.24 no.2
• /
• pp.19-30
• /
• 2012

1. Objectives : The aim of this study was to survey the Original symptoms of Soyangin's and to compare the tendency of their symptoms between Soyangin Gyolhyungjeung and Soyangin Heat-related diarrhea accompanied by headache in patients of indigestion. 2. Methods : We recruited 76 Soyangin subjects in the Korean Medicine clinic and researched their original symptoms. Subjects were diagnosed by the Sasang Constitutional specialists and Sasang Constitutional Medication. Subjects were two groups, confirmed to Soyangin Gyolhyungjeung and Soyangin Heat-related diarrhea accompanied by headache. All subjects answered the questionnaire about their Original symptoms. We found the differences between 2 groups using the Mann-Whitney U Test. Analysis was conducted using SPSS 18.0 for Korean. 3. Results : In Original symptoms, there was no difference between 2 groups in sleep, appetite, digestion, eating habits, water temperature, function of bowel movement, urination, sweating, sensitivity to coldness and sensitivity to warmness. But there was difference between 2 groups in frequency of defecation & hardness of feces(p=0.027). 4. Conclusions : We found the differences of heat and cold in symptoms between two Soyangin syndromes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.5
• /
• pp.321-326
• /
• 2011

Recently, ground source heat pump (GSHP) systems have been introduced in many modem buildings which use the annually stable characteristic of underground temperature as one of the renewable energy uses. However, all of GSHP systems cannot achieve high level of energy efficiency and energy-saving, because their performance significantly depends on thermal properties of soil, the condition of groundwater, building loads, etc. In this research, the effect of thermal properties of soil on the performance of GSHP systems has been estimated by a numerical simulation which is coupled with ground heat and water transfer model, ground heat exchanger model and surface heat balance model. The thermal conductivity of soil, the type of soil and the velocity of groundwater flow were used as the calculation parameter in the simulation. A numerical model with a ground heat exchanger was used in the calculation and, their effect on the system performance was estimated through the sensitivity analysis with the developed simulation tool. In the result of simulation, it founds that the faster groundwater flow and the higher heat conductivity the ground has, the more heat exchange rate the system in the site can achieve.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1991.11a
• /
• pp.80-86
• /
• 1991

In this study an the development of the heat flux sensor with thermocouple, the heat-treated adhesive type film nickel gauge(Ni-Gauge) for measuring temperature was used. and this Ni-Gauge is not only comparable for platinum gauge(Pt-Gauge) in linearity, but also economically cheap. And from this viewpoint. numerical analysis is essential to investigate charateristics of sensor, since this analysis is capable of simulating precise boudary condition and practical conditions and so on. By the way. there are many types of heat flux sensor. of which adhesive type flux sensor is common, in the study this type of heat flux sensor was chogen. and analysis of the sensor is considered as a kind of open cavity figure. performed by SIMPLER algorithm. As a result. through temperature distributial of the sensor by numerical analysis in steady and unsteady state, the dracteristics of the acdhesive type heat flux sensor(lst heat flux sensor) acooodinge to heat flux, that is, outvoltage, sensitivity. and responsibilty could be evaluated. in addition, time of improved heat flux sensor(2nd heat flux sensor) could be predicted fran the reflectian of proper operating temperature(l50 $^{\circ}C$)of theNi-Gauge.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.11
• /
• pp.138-145
• /
• 2009

A suspended membrane micro fluidic heat flux sensor that is able to measure the heat flow rate was designed and fabricated by a complementary-metal-oxide-semiconductor-compatible process. The combination of a thirty-junction gold and nickel thermoelectric sensor with an ultralow noise preamplifier, low pass filter, and lock-in amp has enabled the resolution of 50 nW power and provides the sensitivity of $11.4\;mV/{\mu}W$. The heater modulation method was used to eliminate low frequency noises from sensor output. It is measured with various heat flux fluid of DI-water to test as micro fluidic application. In order to estimate the heat generation of samples from the output measurement of a micro fluidic heat-flux sensor, a methodology for modeling and simulating electro-thermal behavior in the micro fluidic heat-flux sensor with integrated electronic circuit is presented and validated. The electro-thermal model was constructed by using system dynamics, particularly the bond graph. The electro-thermal system model in which the thermal and the electrical domain are coupled expresses the heat generation of samples converts thermal input to electrical output. The proposed electro-thermal system model shows good agreement with measured output voltage response in transient state and steady-state.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.570-576
• /
• 2002

Application of the aged Inconel 718 in hydrogen environment is seriously restraint by its high hydrogen embrittlement (HE) sensitivity. m previous researches, we have suggested the possibility and applicability of the laser surface annealing (LSA) process in improving the HE resistance of this alloy. Sequentially, a study on the effects of the precipitates in the Inconel 718 on its HE sensitivity was conducted in this research. Firstly, flat bar specimens were heat-treated to obtain various kinds of precipitation microstructures concerning the ${\gamma}$" phase and the 6 phase. Hydrogen was charged into the specimen by a cathodic charging process. The loss in reduction of area (RA) caused by hydrogen charging was used to assess the HE sensitivity. The HE sensitivity of the alloy was lowered with decreasing the volume fraction of ${\gamma}$". Moreover, it was possible to increase the HE resistance of the aged alloy by dissolving the $\delta$ phase, keeping the strength at the same level as that of the common aged alloy. Thus, we concluded that both the $\delta$ phase and the ${\gamma}$" phase affected the HE sensitivity of Inconel 718. Next, two kinds of notch tensile specimens were fabricated, one kind having $\delta$ phase and the other having no $\delta$ phase. All these specimens were aged via the same aging heat treatment process. The LSA process annealed a thin layer of the notch bottom of each specimen. One specimen of each kind was charged with hydrogen by the cathodic hydrogen charging process. Loss in the notch tensile strength (NTS) caused by hydrogen was used to evaluate the HE sensitivity. It was found that while the HE sensitivity of conventionally aged Inconel 718 was decreased by the LSA process, the HE sensitivity of the $\delta$-free aged Inconel 718 could further be decreased. Therefore, for applications in hydrogen environments, it is possible to fabricate alloys with both good HE resistance and high strength by controlling the precipitation conditions, and to improve HE resistance further via applying the LSA process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.04b
• /
• pp.93-93
• /
• 2009

In order to overcome the lack of reactivity with hydrogen gas ($H_2$) and utilize unique properties of Carbon Nano Tubes (CNTs) for the application to hydrogen sensors, there have been intensive works on the surface functionalization of CNTs with various types of nanoparticles including Pd. In the present work, we have investigated the effect of dendrimers and Pd nanoparticles to the hydrogen sensing properties of CNTs by comparing three types of samples: Pd/SWNTs (Sample I), Pd/dendrimer/SWNTs (Sample II) and heat-treated Pd/dendrimers/SWNTs (Sample III). As a result of IV measurement under the $H_2$ and air, sample I was found to have a high sensitivity (25%) to $H_2$, but to have a very slow response time (324 s) and recovery rate. On the other hand, Sample II was found to show much faster response time (3 s) and good recovery rate but lower sensitivity (8.6%) than Sample I which is due to induced dipole moments in the dendrimers. Interestingly, Sample III showed both fast response time (7 s) and high sensitivity (25%), indicating that the pyrolysis of the dendrimers during heat treatment which reduce the distance between the surface of the SWNTs and the functionalized Pd nanoparticles plays a key role in improving the sensitivity. The pyrolysis of the dendrimers in Pd nanoparticle-dendrimer-SWNTs was found to enable a significant electrical conductance modulation upon exposure to extremely low concentrations (10 ppm) of $H_2$ in air. Our results demonstrate that the Pd Nanoparticle-Grafted Single-Walled Carbon Nanotubes(SWNTs) with Dendrimers can be used to detect hydrogen, makingoutstanding properties such as fast response, and recovery time, high sensitivity, low detection limit at room temperature compared with other types of hydrogen sensors.

• Proceedings of the IEEK Conference
• /
• 1998.06a
• /
• pp.395-397
• /
• 1998

NH$_{3}$ gas sensitive ZnO:Al, In thin films were prepared by the heat treatment following continuous deposition of very thin In layer and ZnO:Al layer to obtain the modified surface morphology for good sensitivity. Dependence of the structural electrical and optical properties of them on heat treatment temperature was investigated by x-ray diffraction, SEM, 4-point probe method and spectrophotometer.