The sheath heaters have a features with low price and stability for electricity, but these heaters don't have good conditions under high temperature exceeding 800℃. The main purpose of this research is for the replacing of the sheath heater, and to investigate the thermal and fluid flow characterist...
The sheath heaters have a features with low price and stability for electricity, but these heaters don't have good conditions under high temperature exceeding 800℃. The main purpose of this research is for the replacing of the sheath heater, and to investigate the thermal and fluid flow characteristics of the carbon heater. This paper is composed of five sections. The first section has the contents of the heat generation characteristics of the particle type carbon heating source with high temperature. The main variables of this study are the input current and the amount of carbon heating source because the input current is very important to the carbon heating capacity. As the input current and the temperature are increased, the resistance values of carbon heating source were large, and the Joule heat was represented the large value as the amount of heating source decrease. In the second section, the carbon heating source of particle type is applied to a warm air circulator of industrial parts to compare the heat efficiency with the sheath heater. In the carbon heating source, the input and output values are 28.28 kW and 28.23 kW, respectively, and the efficiency is indicated with 97.7 %. The other hand, the input and output in the sheath heater are 21.59 kW and 18.80 kW, the efficiency is showed with 87. 1%. Therefore, the efficiency of the carbon heating source is estimated a high value over 10 % than the sheath heater. In the third section, the flow and thermal characteristics in a three- dimensional warm air circulator with rectangular heating source have been investigated by the standard k-ε two equations turbulence model. The air circulator model has a circular inlet on the ceiling and rectangular exhaust on the bottom. The maximum heat transfer was represented at the top of heating source, and the heat transfer at the bottom wall of heating source was the smallest values. In the fourth section, the carbon heating source with rod type was manufactured and rested. This research aims for replacing a general sheath heater and manufactured two kinds of a carbon heater with rod type. We compared a thermal characteristics between the carbon heating bar and sheath heater. Between the two kinds of carbon heating bar, the carbon rod with 27 wt. % of graphite showed a more high temperature with 30 % than a sheath heater, and the reached time for maximum temperature was very short by comparing to sheath heater. In the last section, the numerical analysis was carried out to observe the properties of temperature distributions inside the material of the carbon heating bar which was manufactured through this research. Before the simulation, the numerical algorithm is compared to the experimental results, and the numerical results are matched very good within ±5 %. In case of same heat generation, the temperature difference between inside and surface is occurred about 8℃, and the temperature at surface is decreased about 50 % by effect of the initial environmental velocity. The correlation equations with several parameters that diameter of heating element, environmental velocity and heat generation is obtained.
The sheath heaters have a features with low price and stability for electricity, but these heaters don't have good conditions under high temperature exceeding 800℃. The main purpose of this research is for the replacing of the sheath heater, and to investigate the thermal and fluid flow characteristics of the carbon heater. This paper is composed of five sections. The first section has the contents of the heat generation characteristics of the particle type carbon heating source with high temperature. The main variables of this study are the input current and the amount of carbon heating source because the input current is very important to the carbon heating capacity. As the input current and the temperature are increased, the resistance values of carbon heating source were large, and the Joule heat was represented the large value as the amount of heating source decrease. In the second section, the carbon heating source of particle type is applied to a warm air circulator of industrial parts to compare the heat efficiency with the sheath heater. In the carbon heating source, the input and output values are 28.28 kW and 28.23 kW, respectively, and the efficiency is indicated with 97.7 %. The other hand, the input and output in the sheath heater are 21.59 kW and 18.80 kW, the efficiency is showed with 87. 1%. Therefore, the efficiency of the carbon heating source is estimated a high value over 10 % than the sheath heater. In the third section, the flow and thermal characteristics in a three- dimensional warm air circulator with rectangular heating source have been investigated by the standard k-ε two equations turbulence model. The air circulator model has a circular inlet on the ceiling and rectangular exhaust on the bottom. The maximum heat transfer was represented at the top of heating source, and the heat transfer at the bottom wall of heating source was the smallest values. In the fourth section, the carbon heating source with rod type was manufactured and rested. This research aims for replacing a general sheath heater and manufactured two kinds of a carbon heater with rod type. We compared a thermal characteristics between the carbon heating bar and sheath heater. Between the two kinds of carbon heating bar, the carbon rod with 27 wt. % of graphite showed a more high temperature with 30 % than a sheath heater, and the reached time for maximum temperature was very short by comparing to sheath heater. In the last section, the numerical analysis was carried out to observe the properties of temperature distributions inside the material of the carbon heating bar which was manufactured through this research. Before the simulation, the numerical algorithm is compared to the experimental results, and the numerical results are matched very good within ±5 %. In case of same heat generation, the temperature difference between inside and surface is occurred about 8℃, and the temperature at surface is decreased about 50 % by effect of the initial environmental velocity. The correlation equations with several parameters that diameter of heating element, environmental velocity and heat generation is obtained.
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