• Proceedings of the KSME Conference
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• 2000.04b
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• pp.7-12
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• 2000

The purpose of this study is to develop heat transfer analysis program of heat pipe elements and design a revolving heat pipe exchanger by the performance experiment of hot air production by means of middle-temperature waste heat. Experimental variables are the revolution per minute, normal velocity of inlet air and the temperature of waste heat. The revolving heat exchanger has designed as $2^{\circ}$ in inclination angle of heat pipe bundle and as 20% in working fluid quantity and as water in working fluid. Experimental value of the total heat transfer coefficient was $20w/m^2-^{\circ}C$

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.5
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• pp.431-436
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• 2014

Conductance is a concept contrary to flow resistance and is extensively used as a flow index on how easily fluid is transported through a pneumatic pipe or fluid device. However, research on flow conductance is very rare to date, and a systematic investigation is needed for the standardization of pneumatic devices. In the present study, a computational fluid dynamics method was applied to solve the compressible Navier-Stokes equations with two-equation turbulence models. The present CFD results were validated with existing experimental data. The conductance values and friction factors at the inlet and outlet of a pneumatic pipe were used to assess the flow rates. The present results showed that the conductance depends on the pressure ratio at the inlet and outlet of a pipe.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.596-600
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• 2011

In this numerical analysis, the distortion of flow measurement by inlet velocity profile of orifice flowmeter was investigated. To validate the numerical method, the convergence was monitored and the grid dependency was also checked. realizable k-e model was selected and y+ was about 50 in this calculation. the results shows that the pressure at the pressure tab near pipe wall was changed by inclined inlet velocity profile and it leads to distorted a measurement values of flow through the orifice plate from -3.8% to 9%. Therefore, the fully developed inlet flow was required for accurate flow measurement by orifice flowmeter. If not, the orifice plate installed at wrong location should be re-installed or additional actions should be taken.

• Transactions of the Korean Society of Mechanical Engineers
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• v.3 no.1
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• pp.1-9
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• 1979

Methanol was examined as supplemental fuel for open chamber type and pre-combustion chamber type diesel engine. Pre-determined quantities of diesel oil were injected as ordinary diesel engines and methanol was added at inlet pipe using venturi, nozzel and and float chamber for the rest of the charge. In this mode of operation, addition of methanol reduced inlet and exhaust temperature. Inlet air quantities were essentially unchanged in spite of lower inlet temperature. Exhaust smoke was significantly reduced At light load when both diesel oil and methanol were introduced with small quantities, specific heat consumption was considerably increased. However, with the increase of the quantity of methanol or diesel oil, specific heat consumption was improved. With sufficient quantities of diesel oil enough to produce the power above 3/4 load, addition of methanol showed better thermal economy.

• Journal of Biosystems Engineering
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• v.36 no.5
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• pp.319-325
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• 2011

This study was conducted to figure out the diagnosis basis of cooling performance depending on water amount in the refrigerant of air conditioner, which can be estimated by the temperatures and pressures along the refrigerant circulation line. A car air conditioner of SONATA III (Hyundai motor Co., Korea) was tested at maximum cooling condition at the engine speed of 1500 rpm in the room controlled at 33~$35^{\circ}C$ air temperature and 55~57% relative humidity conditionally. Measured variables were temperature differences between inlet and outlet pipe surfaces of the compressor, condenser, receive drier and evaporator; and high pressure and low pressure in the refrigerant circulation line; and temperature difference between inlet and outlet air of the cooling vent of evaporator. In this study, changes of the water amount in the refrigerant were correlated to the temperatures and pressure changes and also water amount caused poor cooling performance. As water amount increased in the refrigerant in the air conditioner, the performance of the cooling or the heat transfer became worse. Temporal variations of the surface temperature of the evaporator outlet pipe and the low-side pressure showed various patterns that could estimate the water amount. When the water amount caused bad cooling performance, the patterns of the temperature of the evaporator outlet pipe indicated irregular fluctuation greater than $5^{\circ}C$. When the diagnosis system is using just external sensors of the low-side pressure and the temperatures of inlet and outlet air of cooling vent of the evaporator, the precise pattern of bad cooling performance caused by excess water amount in the cooling line was irregular pressure fluctuation, 25 kPa under 120 kPa, and temperature, $12^{\circ}C$ and less.

• Journal of computational fluids engineering
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• v.9 no.2
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• pp.11-17
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• 2004

CFD analysis was performed to figure out flow behavior in the inlet plenum of new research reactor where coolant is injected to the flow tubes with the fuel assembly. The computation results showed that large-scale vortices are generated in the inlet plenum by flow stream injected from inlet pipe. These vortices are divided into small vortices and reversed their revolution. They may lead to flow-induced vibration of fuel assembly, moreover, which has been regarded as a cause of fretting wear of fuel assembly. Also there is an another important thing that average velocity of each flow-tube is uneven showing difference in maximum 18%. So it has been suggested that perforated baffle will be installed to prevent the formation of vortex in the inlet plenum. Two perforated baffles, one is flow skirt and the other is muffler type flow straightener, were proposed and their effect was evaluated using commercial CFD code, Fluent. According to CFD analysis for two perforated baffles, it was confirmed that both of them can prevent or reduce vortex formation in the inlet plenum and make average velocity of each flow tube more even.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.63.1-63.1
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• 2008

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.1
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• pp.19-30
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• 2002

This paper addresses characteristics of compressible flow dynamics inside a pipe with an accumulator and an inlet orifice. It also presents a simple but stable numerical method associated with the accumulator-orifice calculation. In particular, a focus is given to developing a method of finding an optimum design of the accumulator-orifice system (i.e., the accumulator size and the throttle resistance) that gives the most effective dissipation of the water-hammering problem. It is found that there exists indeed an optimum set of parameter values for the most effective dissipation of the wave energy.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.191-200
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• 1997

This paper discusses prediction of the sound pressure level produced by simple engine exhaust systems(plain pipe, plain expansion chamber pipe, plain expansion chamber with internally extended inlet and outlet pipe, perforated pipe enclosed in a plain expansion chamber) and a computer program has been developed which predicts the sound pressure level and the frequency spectrum. The program utilizes unsteady flow gas dynamic theory and acoustic theory to predict the pressure-time history in the exhaust system and the mass flow rate-time history at the open end of the system and the sound pressure levels(1/3 Octave band levels) and the frequency spectrum in semi-anechoic room. The predictions are compared with measured levels and show a high degree of correlation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.1
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• pp.78-85
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• 1991

An experimental result for heat transfer of pulsating turbulent pipe flow was presented under the condition of fully developed dynamic regime and uniform wall heat flux. Experiments were performed at following conditions ; Inlet time-averaged Reynolds number varied from 5000 to 11000; The peak pressure fluctuation were 1.3, 2.3 and 3.5 percent of the mean pressure; Pulsating frequency ranged from 53 Hz to 320 Hz The measurements showed that the effect of pulsation on local heat transfer is greater at downstream, in which pulsating source exists, than upstream and the heat transfer rate, averaged over the pipe length, was higher or lower than in an equivalent non-pulsating flow according to the pulsating conditions. In addition, the significant change of heat transfer rate was observed in acoustically resonant conditions, when the pulsating frequency of the flow corresponded to the pipe natural frequency.