• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.433-437
• /
• 2005

This study was carried out the design and analysis of solar thermal system with preheating of returning district heating water for the Chung-ju district heating and cooling system. Two different types of solar collectors are used for this system. TRNSYS simulation program was used for the analysis. As a results, the solar system efficiency is $35.8\%$ for the plate type and $45.1\%$ for the evacuated type solar collector in the case of $50^{\circ}C$ for the returning district heating water temperature. The returning district heating water temperature is on of the very important factors that is influence on the system efficiency. So the effect of the returning district heating water temperature on the system efficiency is analyzed in this study.

• Korean Journal of Human Ecology
• /
• v.23 no.6
• /
• pp.1205-1215
• /
• 2014

The purpose of this study was to investigate the effect of local heating and cooling of various body parts on the skin temperature of the exposed extremities including neck. Hot pack was used to warm up the body of seven participants for 15 minutes and it was removed as the temperature of the hot pack decreased after 15minutes of warming. Thermograms of body surface with and without hot pack were analyzed intensively to observe the efficiency of the local heating of shoulder, abdomen, back waist, and foot on the skin temperature of ten area of the subjects' body. The results indicated that the absolute skin temperature of front upper arm and thigh was significantly higher depending on the area of heating, especially, in case of abdomen and foot heating, which was not observed at the back of the body. The rate of skin temperature of extremities such as finger, palm and foot was significantly different depending on the body area of local heating. Generally, it was found that back waist heating was not efficient to warm up and maintain the skin temperature of the body after removing the hot pack.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.48 no.6
• /
• pp.436-441
• /
• 1999

Joule heating effect in EM(Electromigration) test were performed on a bend test structure. EM test is done under high current densities(1.0-2.5MA/cm2), which leads to joule heating. Since joule heating is added to the controlled oven(stress) temperature, themetal line temperature is higher than the stress temperature. The increase in the stress temperature due to joule heating is important because EM phenomena and metal line failure are related to the stress temperature. In this paper, metal line was stressed with a current density of 1.0 MA/$cm^2$, 1.5MA/$cm^2$, 2.0MA/$cm^2$, 2.5MA/$cm^2$, for 1200 sec and temperature increase due to joule heating was less than $10^{\circ}C$. Also it took 30 minutes for the metal line to equalized with oven temperature. Recommendations are given for the EM test to determine the initial resistance of EM test structure under stress temperature and current density.

• Journal of the Korean Solar Energy Society
• /
• v.26 no.1
• /
• pp.99-104
• /
• 2006

This paper presents an analysis of heating energy for apartment houses in apartment building, paying special attention on the effect of pilotis which is increasing recently. A four-zone model composed of one conditioned and three unconditioned space is developed in this study. IES VE is adopted to estimate heating energy. Especially, we used Apache module for a heating energy calculated. The predicted result shows fairly good agreements with the available measured data and simulation data. Heating energy needed for an apartment located on the pilotis floors is far greater compared with the case of intermediate floors. Insulation thickness of walls, floors and underground structure appears to be a dominant factor affecting heating energy, which leads to needs of revision of the related regulation. It is finally concluded that the location dependent, severe imbalance in heating energy should be improved and reflected in the policy making process and the design standards.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.28 no.2
• /
• pp.69-74
• /
• 2016

Most hot water heating valves for apartments are constant-flow types, which limit the flow rate through an individual household for even distribution of heating water to other households. The constant-flow type is implemented by an on-off control. As a result, heating water is supplied intermittently and hence, indoor air temperature also fluctuates. Returning water temperature is also high, which reduces energy efficiency. To implement continuous feedback control, the indoor temperature dynamics was simulated to fit a measured temperature history by a state-of-the-art physical model. From the model, it was found that the most important disturbance is outdoor temperature and its effect on indoor temperature lasts about an hour. To cope with the slow response and the significant disturbance, a prediction control with proportional feedback is proposed. The control was found to be successful in implementing continuous heating water flow and improved indoor temperature control.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.8
• /
• pp.56-61
• /
• 2005

The induction heating is widely used not only in the industrial fields but also in the home appliances. But the conventional induction heating systems have shortcoming that it use only magnetic utensil, in this paper, heating of Aluminum sheet by full-bridge series resonant high-frequency inverter is proposed. Also, the principle of induction heating and operations of full-bridge inverter equivalent circuit are explained. The proposed inverter controls the output voltage using phase-shift irrespective of the switching frequency using phase-shift. As a result the proposed induction heating system by full-bridge resonant inverter shows the possibility that make up for the shortcoming of the conventional existing induction heating systems.

• Journal of the Korean Society of Industry Convergence
• /
• v.25 no.2_2
• /
• pp.271-278
• /
• 2022

The solar energy has been widely used to reduce the fossil fuel and prevent the environmental pollution. The renewable energy including solar heat tends to spread due to carbon neutrality for main country of the world. Targets of solar collector are usually acquisitions of hot water or hot air. Especially, air-heating collector using solar heat is known as the technology for obtaining hot air. This study aims to investigate of characteristics of thermal flow when the hot air by air-heating collector using solar heat flows inside of indoor space. The thermal flow of heating indoor space was simulated using ANSYS-CFX program and thus the behaviors of hot air in indoor space were evaluated with standard k-𝜀 turbulence model. As the results, as the inlet velocity was increased, the behaviors of hot air became simple, and temperature range of 25~75℃ had almost no effect on behavior of flow. As the inlet temperature was increased, the temperature curve of indoor space from bottom to top was changed from linear to quadratic. Furthermore, it was confirmed that inlet velocity as well as inlet temperature also should be considered to heat indoor space equally by air-heating collector using solar heat.

• Korean Journal of Food Science and Technology
• /
• v.25 no.6
• /
• pp.698-702
• /
• 1993

Effect of heating temperature on elution patterns of soluble carbohydrate of legume starches and the texture of starch gels was investigated. The elution profiles of soluble carbohydrate obtained by Sepharose 2B-CL showed that the larger molecules were leached as the heating temperature increased. The elution profiles of soluble carbohydrate of cow pea and mung bean starches were similar, but those of kidney bean starch were different. The gel structures of cow pea and mung bean were stable with showing high values in hardness and cohesiveness. But red bean and kidney bean gels were weak in hardness and cohesiveness. As the heating temperature rised, hardness and cohesiveness were increased in gels prepared by heating for 15 min. However, the gels made by heating for 1 hour showed that less hard and more cohesive gels from cow pea and mung bean, while harder and more cohesive gels from red bean and kidney bean were obtained as the heating temperature increased from $85^{\circ}C\;to\;95^{\circ}C$.

• Journal of Welding and Joining
• /
• v.34 no.2
• /
• pp.46-53
• /
• 2016

Effect of heating rate on microstructure of brazed joints with STS 304 Printed Circuit Heat Exchanger (PCHE),which was manufactured as large-scale($1170(L){\times}520(W)){\times}100(T)$, mm), have been studied to compare bonding phenomenon. The specimens using MBF 20 was bonded at $1080^{\circ}C$ for 1hr with $0.38^{\circ}C/min$ and $20^{\circ}C/min$ heating rate, respectively. In case of a heating rate of $20^{\circ}C/min$, overflow of filler metal was observed at the edge of a brazed joints showing the height of filler metal was decreased from $100{\mu}m$ to $68{\mu}m$. At the center of the joints, CrB and high Ni contents of ${\gamma}$-Ni was existed. For the joints brazed at a heating rate of $0.38^{\circ}C/min$, the height of filler was decreased from $100{\mu}m$ to $86{\mu}m$ showing the overflow of filler was not appeared. At the center of the joints, only ${\gamma}$-Ni was detected gradating the Ni contents from center. This phenomenon was driven from a diffusion amount of Boron in filler metal. With a fast heating rate $20^{\circ}C/min$, diffusion amount of B was so small that liquid state of filler metal and base metal were reacted. But, for a slow heating rate $0.38^{\circ}C/min$, solid state of filler metal due to low diffusion amount of B reacted with base metal as a solid diffusion bonding.

• The Journal of Advanced Prosthodontics
• /
• v.11 no.4
• /
• pp.202-208
• /
• 2019

PURPOSE. Fabrication of zirconia restorations with ideal mechanical properties in a short period is a great challenge for clinicians. The purpose of the study was to investigate the effect of heating rate on the mechanical and microstructural properties of monolithic zirconia. MATERIALS AND METHODS. Forty monolithic zirconia specimens were prepared from presintered monolithic zirconia blanks. All specimens were then assigned to 4 groups according to heating rate as Control, Group $15^{\circ}C$, Group $20^{\circ}C$, and Group $40^{\circ}C$. All groups were sintered according to heating rates with the sintering temperature of $1500^{\circ}C$, a holding time of 90 minutes and natural cooling. The phase composition was examined by XRD analysis, three-point bending test was conducted to examine the flexural strength, and Weibull analysis was conducted to determine weibull modulus and characteristic strength. Average grain sizes were determined by SEM analysis. One-way ANOVA test was performed at a significance level of 0.05. RESULTS. Only tetragonal phase characteristic peaks were determined on the surface of analyzed specimens. Differences among the average grain sizes of the groups were not statistically significant. The results of the three-point bending test revealed no significant differences among the flexural strength of the groups (P>.05). Weibull modulus of groups was ranging from 3.50 to 4.74. The highest and the lowest characteristic strength values were obtained in Group $20^{\circ}C$ and Control Group, respectively. CONCLUSION. Heating rate has no significant effect on the flexural strength of monolithic zirconia. Monolithic zirconia restorations can be produced in shorter sintering periods without affecting the flexural strength by modifying the heating rate.