• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.601-608
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• 2003

Thermal analyses have been carried out for a spent fuel dry storage cask under normal and off-normal conditions. Environmental temperature is assumed to be $15^{\circ}C$ under the normal condition. The off-normal condition has an environmental temperature of $38^{\circ}C$. An additional off-normal condition is considered as a partial blockage of the air inlet ducts. Two of the four air inlet ducts are assumed to be completely blocked. The maximum temperatures of the fuel rod and concrete overpack were lower than the allowable values under the normal condition. Temperature distributions for the off-normal conditions were slightly higher than the normal conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.400-405
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• 2011

This paper presents the heating performance characteristics of the air source heat pump with air to water type. The heating capacity, COP, P-h diagram were measured at various operating conditions, air-side temperatures, relative humidities, and inlet/outlet water temperature under the standard heating condition of KS B 6275. The experimental data for the heat pump were measured using the air-enthalpy calorimeter and the constant temperature water bath. As the air-side temperature increases, the heating capacity and COP increase. The effect of the air-side relative humidities on the heat pump performance is insignificant. The heat pump performance on inlet and outlet water temperatures and air-side temperatures(-7, -11, $-15^{\circ}C$) were studied. Heating capacity and COP increased about 27~39% with the air-side temperature increasing. Enthalpy between the front and the rear of condenser decreased about 6% by increasing of the inlet water temperature. These results can be utilized in the design of the air source heat pump system with air to water type.

• International Journal of Automotive Technology
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• v.8 no.1
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• pp.27-31
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• 2007

The number of vehicles employing diesel engines is rapidly rising. Accompanying this trend, application of an after-treatment system is strictly required as a result of reinforced exhaust regulations. The Diesel Particulate Filter (DPF) system is considered as the most efficient method to reduce particulate matter (PM), but the improvement of a regeneration performance at any engine operation point presents a considerable challenge by itself. Therefore, the present study evaluates the effect of fuel injection characteristics on regeneration performance in a DOC and a catalyzed CR-DPF system. The temperature distribution on the rear surface of the DOC and the exhaust gas emission were analyzed in accordance with fuel injection strategies and engine operating conditions. A temperature increase more than BPT of DPF system was obtained with a small amount fuel injection although the exhaust gas temperature was low and flow rate was high. This increase of temperature at the DPF inlet cause PM to oxidize completely by oxygen. In the case of multi-step injection, the abrupt temperature changes of DOC inlet didn't occur and THC slip also could not be observed. However, in the case of pulse type injection, the abrupt injection of much fuel results in the decrease of DOC inlet temperatures and the instantaneous slip of THC was observed.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.63-72
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• 2003

In order to reduce NOx emissions in the 20kW class microturbine under development, the low NOx characteristics, as being an application to the lean premixed combustion technology, have been investigated. The study has been conducted at the conditions of high temperature and high pressure. Theair from a compressor with the pressure of 2.5bar, 3.0bar, 3.5bar was supplied to the combustor with the temperature 560K through the air preheat-treatment. The sampling exhaust gas was measured at the immediate exit of the combustor. For the effect of temperature on NO and CO emissions, though NOx were increased, CO was decreased with increasing inlet air temperature. With increasing inlet air pressure, NOx were increased and CO was decreased also. NOx were decreased, but CO was increased with increasing inlet air mass flow rate. The test has been performed on the equivalent ratio of 0.10 to 0.16 in the lean region. NOx were increased with increasing equivalent ratio, but CO was decreased as an influence of flame temperature. CFD work with an appropriate combustion model predicated a complicated swirling flow pattern in the combustor, and also produced a numerical value of NOx and CO emissions which was to be compared with the experimental one. As the results of this study, NOx are expected to be reduced to less than 42ppm at 15% O2 when operated at the design condition of the 20kW class microturbine.

• Journal of the Korean Solar Energy Society
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• v.35 no.3
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• pp.73-79
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• 2015

In this study, a thermal storage performance and characteristics of daily operation were investigated when the air and the liquid were heated simultaneously by a hybrid solar air-water heater that can make hot water as well as heated air. The hybrid solar air-water heater is kind of a flat plate solar collector that can make hot water and heated air by installing air channel beneath absorber plate of traditional flat plate solar collector for hot water. As a result of daily operation, maximum water temperature reached in a thermal storage was shown $44^{\circ}C$ on 73kg/h of air mass flow rate and about $40^{\circ}C$ on 176kg/h of air mass flow rate. Thus, the necessity of heating water in thermal storage by operating only liquid side was confirmed when the temperature of liquid in thermal storage is lower than we need. In case of efficiency investigated on daily operation, the thermal efficiency of the liquid side was decreased with increment of the inlet liquid temperature and decrement of the solar radiation, but efficiency of the air side was increased with increment of inlet liquid temperature difference as the traditional solar air heater. Total thermal efficiency of the collector was shown from 65.85% to 78.23% and it was decreased with increment of the inlet liquid temperature and decrement of solar radiation same as the traditional system.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_2
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• pp.1093-1101
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• 2020

This study was carried out numerically to investigate the air flow and thermal performance around single and parallel fin-tube heat exchangers and the cooling performance of the fluid inside the heat exchangers. In this study, the air velocity(1~7m/s), the pitch of fin(4, 6.1, 8, 11.3, 18.3, 44mm) and the diameter of fin(31, 33, 35, 37, 39mm) were varied. The flow rate of the water at the fin-tube heat exchanger inlet is 89cc/min and the water temperature is 353K. The air temperature at the upstream region of the heat exchanger is 300K. flow rate of the water at the fin-tube heat exchanger inlet is 80cc/min and the water temperature is 353K. It was found that the air pressure drop around single and parallel fin-tube heat exchangers was highly dependent on the air velocity and the fin pitch, but was independent of the fin diameter. Also, it was shown that pressure drop increased more the parallel arrangements than in single heat exchanger. The temperature difference of water at the inlet and outlet of the heat exchanger depended on the air velocity, the fin pitch and the fin diameter, and it was found that the parallel arrangement method further reduced the temperature of water. It was shown that the Nusselt number increased as the Reynolds number and the fin pitch increased, and decreased as the fin diameter increased.

• Journal of Biosystems Engineering
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• v.24 no.6
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• pp.513-522
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• 1999

This study was performed to get the optimal operating conditions of an water-air compact heat pump system using R-134a. The experiments was done for three elvels of the air mass flow rate and the compressor driving speed during air-heating process. The temperature of the air at the condenser inlet and outlet was 17~23$^{\circ}C$, 36~44$^{\circ}C$, respectively. The average temperature of the refrigerant at the evaporator and condenser was 1$0^{\circ}C$, 6$0^{\circ}C$, respectively. The temperature of the refrigerant was not depending on the air mass flow rate and the compressor driving speed. The pressure of the refrigerant at the condenser inlet and outlet was ranged of 10~18.5kg/$\textrm{cm}^2$ and that at the evaporator was ranged of 3.1~3.3kg/$\textrm{cm}^2$. The pressure drop at the condenser and evaporator was about 1.5, 1.2 kg/$\textrm{cm}^2$, respectively. The performance of coefficient for air heating was about 3.3~4.0.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.155-160
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• 2001

The low NOx characteristics have been investigated to develop the combustor for micro turbine. The lean premixed combustion technology was applied to reduce the NOx emission. The test was conducted at the condition of high temperature and ambient pressure. The combustion air which has the temperature of $450\sim650K$ were supplied to the combustor through the air preheater. The temperature and emissions of NOx and CO were measured at the exit of combustor, The exit temperature and NOx were increased and CO was decreased with increasing inlet air temperature. The premixing chamber can be operated very lean condition of equivalence ratio around 0.35. The NOx was decreased with decreasing the equivalence ratio. The CO was decreased with decreasing the equivalence ratio, but the CO was increased with decreasing the equivalence ratio below 0.4. But, at the very lean condition of equivalence ratio below 0.35 both NOx and CO were increased because of the flame unstability. The NOx was decreased and CO was increased with increasing inlet air flowrate. This results can be used to determine the size of combustor. Consequently the performance of combustor shows the possibility of the application to the gas turbine system.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.314-319
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• 2003

The concept of lean-premixed combustion in gas turbine combustor operation has become a standard in recent years as an effective means to meet stringent enviromental standards on NOx emissions. The combustion characteristics of 75 kW class lean premixed combustor were investigated at the conditions of high temperature and ambient pressure. The exit temperature and emissions of CO and NOx were measured at the center of exit plane. The high temperature air of $550K{\sim}650K$ was supplied through air preheater. As expected, experimental results indicate that NOx emission was increased and CO emission was decreased by increasing inlet air temperature. But CO emission measured at the center of exit plane was increased because of the non-uniform radial direction profiles. The Semi-Empirical Correlation method was applied to obtain the design point emissions of NOx and CO. Also the flame temperature, CO and NOx emissions were measured along the centerline of liner at 650K inlet air temperature to determine the position of dilution holes.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.448-453
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• 2005

Temperature Control Valve (TCV) is one of the useful temperature control devices, which is used to control constant temperature of working fluid in power and chemical plants and domestic water supply systems. TCV is composed of body, cylinder and piston, and the body shape has a symmetrical H-type. In general, it has several inlet and outlet holes, and its shape is like as tubular sleeve. The piston has three rings two rings of the end of piston have the function of controlling inlet flow rate with hot and cold working fluids, the center ring has the function of preventing hot and cold water from intermixing. Consequently, the shapes of piston and cylinder are the main design parameters in the performance of TCV. In this study, numerical analyses were carried out with two different piston and cylinder shapes to investigate the functions as a temperature control valve and the flow characteristics according to piston opening grade in TCV. Using a commercial code, FLUENT, velocity and pressure fields in TCV are obtained under steady, standard $k -{\epsilon}$ turbulence model and no-slip condition.