• Journal of the Korean Society of Visualization
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• v.21 no.3
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• pp.23-32
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• 2023

This study aims to explore the heat transfer and flow phenomena inside an instant water heater and the influence of the design parameters of the water heater on the heating performance was investigated by 3-D numerical simulations considering heat convection. The design parameters are the heating ceramic dimension, the power of the heating device, and the water flow rate. The results show that a reasonable space for the heating device is required to optimize the heating performance. It is desirable to design higher heating device as possible for a given electric power. There exists a critical water flow rate that best meets the heating performance. The change in electric power has no impact on the flow phenomena and heating performance.

• The KSFM Journal of Fluid Machinery
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• v.15 no.3
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• pp.57-63
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• 2012

Effects of coolant pre-cooling and fuel pre-heating on the performance of a combined cycle using a F-class gas turbine were investigated. Coolant pre-cooling results in an increase of power output but a decrease in efficiency. Performance variation due to the fuel pre-heating depends on the location of the heat source for the pre-heating in the bottoming cycle (heat recovery steam generator). It was demonstrated that a careful selection of the heat source location would enhance efficiency with a minimal power penalty. The effect of combining the coolant pre-cooling and fuel pre-heating was also investigated. It was found that a favorable combination would yield power augmentation, while efficiency remains close to the reference value.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.4
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• pp.355-361
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• 2011

The power control of the existing heating element has been using the On-Off control, phase control, and PWM control. In case of controlling power PTC heating element developed recently with the existing method, the temperature is unable to be precisely controlled or the harmful electromagnetic wave to human body is generated. In this paper, We suggest the power control of PTC heating cable using variable AC Cycles. This regards the AC cycle of N as the unit of the power control. It determines On-Off for each cycle. It is the AC power control method in which it arranges the on-cycle in N cycles in the random and it supplies the current continuously. At this time. the minimal electric power amount becomes 1/N. The maximum current amount becomes 1 and sets up the number of on cycles according to the set value and can control the electric power with the step of N consistently. In the PTC heating system, we show that proposed power control method is superior in the EMI and temperature control property using MATLAB simulation, experiments and measurements.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.6
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• pp.288-291
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• 2002

We developed a new RF indirect-heating LPE furnace. The thermal gradient of our newly developed furnace is less than that of direct heating, and is as gentle as that of the resistance-heating LPE furnace. With this new furnace, the heating and/or cooling is faster than that of the resistance-heating furnace. Impurity-doped YIG film was grown from a $PbO-B_{2}O_{3}$, based flux on a (111) GGG substrate. To study the effect of the impurities on the MSSW threshold power and the saturation response time, we used two microstrip lines to excite and propagate the MSSW at 1.9 GHz. The MSSW threshold power and saturation response time was found to be related to the $\Delta$H.

• Journal of Power Electronics
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• v.5 no.4
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• pp.272-281
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• 2005

In this paper, a simple power control scheme for a constant frequency Class-D inverter with a variable duty cycle is proposed. It is more suitable and acceptable for high- frequency induction heating (IH) jar applications. The proposed control scheme has the advantages of not only wide power regulation range but also ease of control output power. Also it can achieve a stable and efficient Zero-Voltage-Switching (ZVS) in a whole load range. The control principles of the proposed method are described in detail and its validity is verified through simulated and experimental results on 42.8kHz IGBT for induction heating rated on 1.6kW with constant frequency variable power.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.379-382
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• 2008

This paper gives the support method of DSM program(power load leveling for heating and cooling facilities on building). As the national power peak load increases recently, the peak load reduction is needed. So we studied about remote controlling of power load from heating/cooling facilities on building during peak times. To adopt new DSM program, it is very important to design DSM customer supporting system. So in this paper, we dealt with the result of customer survey, and the DSM potential regarding heating/cooling facilities on building. In conclusion, the peak reduction program of heating/cooling facilities is very important and the incentive of customer should be consist of two incentive types as an installation and power reduction.

• Journal of Biosystems Engineering
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• v.28 no.3
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• pp.217-224
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• 2003

To find out heating load and to determine the power of heat pump compressor for the Ondol room heating the COP of heat pump, the variation of Ondol room air temperature, the variation of ambient temperature and power consumption of heat pump are analyzed. The results from this study were summarized as follows: 1. The COP of the heat pump in close loop decreased as the ambient air temperature. The COP was 2.26 when the temperature difference of condenser was $20\pm3^{\circ}C$. 2. The Ondol surface temperature was $25\pm3^{\circ}C$ when the hot water of $40^{\circ}C$ was supplied from hot water storage tank to the Ondol and the temperature difference between the Ondol surface and the room air temperature was $7~8^{\circ}C$. 3. The ratio of thermal conduction heating load to total heating load in Ondol heating space was found to be 83% and ratio of ventilation heating load was 17%. Therefore, the thermal conduction heating load was confirmod to be a major heating load in Ondol heating space. 4. In case of the ambient temperature of $3.2^{\circ}C$, the efficiency of heat exchange of Ondol heating system was 85%. 5. The heating load per Ondol heating surface area and volume of Ondol room space were theoretically analyzed. In case of the room temperature of $20^{\circ}C$ and the ambient temperature of $-3.2~3.8^{\circ}C$, the heating load per Ondol surface area was 115.8~167.6kJ/h ㆍ㎥ and per Ondol mom space volume was 50.2~72.7kJ/h ㆍ㎥. 6. The compressor power of heat pump fur the Ondol room heating could be determined with the heating load analyzed in this study In case of the Ondol room air temperature of 17~2$0^{\circ}C$ and the ambient temperature of -5~3.8$^{\circ}C$, the compressor power of heat pump per Ondol surface area was analyzed to be $2.3\times10^{-2}psm^2$, and per volume of Ondol room space $1.0\times10^{-2}1.4\times10^{-2}ps/m^2$ps.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.526-533
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• 2001

Induction heating of float metal products has an increasing importance in many applications, because it generates the heat within workpiece itself and provides high power densities and productivity. In this study, the induction heating of a steel plate to simulate the line heating is investigated by means of the Finite Element Analysis of the magnetic field and temperature distribution. A numerical model is used to calculate temperature distribution within the steel plate during the induction heating with a specially designed inductor. The effects of materital properties depending on the temperature and magnetic field are taken into consideration in an iterative manner. The simulation results show good magnetic field with experimental data and provide good understanding of the process. Since the numerical model demonstrates to be suitable for analysis of induction heating process, the effects of air gap and frequency on magnetic-flux and power-density distribution are also investigated. It is revealed that these process parameters have an important roles on the electro-magnetic field and power-density distribution governing the temperature distribution of the plate.

• Journal of Biosystems Engineering
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• v.40 no.3
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• pp.250-260
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• 2015

Purpose: Dual cylindrical microwave chambers equipped with an ohmic heating tube were designed and fabricated to maximize the electric field strength for expeditious heat treatment of particulate foods. Methods: The efficacy of the combination heater was investigated by simulating the electric field distribution by using COMSOL Multiphysics software. Results: All components of the designed microwave heating unit were suitable for transmitting maximal microwave power to the load. The simulated electric field distribution implied that single-mode microwave heating would be sufficient for the steady generation of a highly localized heating zone in the cavity. During impedance matching, the calculated reflection coefficient ($S_{11}$) was small, possibly implying minimal power loss and wave reflection in the designed microwave heating chamber. Conclusions: This study demonstrates the possibility of concentrating the microwave power at the centerline for a single-frequency microwave, for thermal treatment of multiphase foods without attenuating the microwave power.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.408-411
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• 2008

As to this research is new structure of the semiconductor substrate heating apparatus. The fast thermoresponsive according to the direct heating structure of the heating plate layer adhering closely to the floor side of a substrate and the fast heat loss minimization can be accomplished. Moreover, the contact area of the sheath heater, which is the heating plate layer built-in heating apparatus, is increased, so that it has more heating valid area. For this, it adheres closely to the substrate, in which the photosensitive film is coated and the heating plate layer, adhering closely to the floor side of a substrate the mica layer which adheres closely to the floor side of the upper heating plate layer in order to minimize an insulation and heat loss, and the lower part of the mica layer and it is comprised of the floor plate layer. The heating plate layer forms the continued groove portion over the floor side whole. The sheath heater for heating a substrate is inserted with the groove portion and the heating plate layer is comprised. It is confirmed that by using the new substrate heating structure, the temperature change of the heating plate against the time is observed. Then, there is the electric power saving effect of about 40% in comparison with the existing method.