• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2675-2685
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• 1994

A study has been conducted to provide the experimental information for the velocity and temperature profiles of steam-air mixutre and to investigate their roles on the film condensation with wavy interface. Saturated gas mixture of steam-air was made to flow through the nearly horizontal$(4.1^{\circ})$ square duct of 0.1m width and 1.56m length at atmospheric pressure, and was condensated on the bottom cold plate. The air mass fraction in the gas mixture was changed from zero(W =0, pure steam) to one(W =1, pure air), and the bulk velocity was varied from 2 to 4 m/s. Water film was injected concurrently to investigate the effect of wavy interface on the condensation. The velocity and temperature profiles were measured by LDA system and thermocouples along the three parameters ; air mass fraction, mixture velocity and film flow rate. The profiles moved toward the interface with increasing steam mass fraction, mixture velocity and film flow rate. The Prandtl and Schmidt numbers were near one in the present experimental range, however there was no complete similarity between the velocity and temperature profiles of gas mixture. And the heat transfer characteristics and interfacial structure were coupled with each other.

• The KSFM Journal of Fluid Machinery
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• v.19 no.4
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• pp.29-34
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• 2016

In this study, the experimental investigation of air-cooled condensation in slightly inclined circular tubes with and without fins has been conducted. In order to assess the effects of the essential parameters, variable air velocities and steam mass flow rates were given to the test section. The heat transfer performance of air-cooled condensation were dominantly affected by the air velocity, however, the increase of the steam mass flow rate gave relatively weaker effects to total heat transfer capability. And in the experimental cases with the finned tube, the total heat transfer rate of the finned tube was significantly larger than that of the flat tube. From those results, it can be confirmed that the most important parameter for air-cooled condensation heat transfer is the convective heat transfer characteristics of air. Therefore, for the well-designed long-term cooling passive safety system, the consideration of the optimal design of the fin geometry is needed, and the experimental and numerical validations of the heat transfer capability of the finned tube would be required.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.5
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• pp.397-407
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• 2004

It is well known that some key parameters, such as evaporating temperature, refrigerant mass flow rate, face velocity and inlet air temperature, have significant influence on the evaporator performance. However performance studies related to a humid environment have been very scarce. It is demonstrated that the refrigerant mass flow rate, heat flux, water condensing rate and air outlet temperature of the evaporator significantly increase with air inlet relative humidity. As the air inlet relative humidity increases, the latent and total heat transfer rates increase, but the sensible heat transfer rate decreases. The purpose of this study is to provide experimental data on the effect of air inlet relative humidity on the air and refrigerant side pressure drop characteristics for a slit fin-tube heat exchanger. Experiments were carried out under the conditions of inlet refrigerant saturation temperature of 7 $^{\circ}C$ and mass flux varied from 150 to 250 kg/$m^2$s. The condition of air was dry bulb temperature of 27$^{\circ}C$, air Velocity Varied from 0.38 to 1.6 m/s. Experiments Showed that air Velocity decreased 8.7% on 50% of relative humidity 40% of that at degree of superheat of 5$^{\circ}C$, which resulted that pressure drop of air and refrigerant was decreased 20.8 and 8.3% for 50% of relative humidity as compared to 40%, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.11
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• pp.943-956
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• 2003

A numerical program has been developed for the simulation of automotive engine cooling system. The program determines the mass flow rate of engine coolant circulating the engine cooling system and radiator cooling air when the engine speed is adopted by appropriate empirical correlation. The program used the method of thermal balance at individual element through the model for radiator component in radiator analysis. This study has developed the program that predicts the coolant mass flow rate, inlet and outlet temperatures of each component in the engine cooling system (engine, transmission, radiator and oil cooler) in its state of thermal equilibrium. This study also combined the individual programs and united into the total performance analysis program of the engine cooling system operating at a constant vehicle speed. An air conditioner system is also included in this engine cooling system so that the condenser of the air conditioner faces the radiator. The effect of air conditioner to the cooling performance, e.g., radiator inlet temperature, of the radiator and engine system was examined. This study could make standards of design of radiator capacity using heat rejection with respect to the mass flow rate of cooling air. This study is intended to predict the performance of each component at design step or to simulate the system when specification of the component is modified, and to analyze the performance of the total vehicle engine cooling system.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1191-1196
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• 2009

The T-s chart of air displays graphically the thermophysical properties, so it is very conveniently used in various thermal systems. In previous study, the software analyzing 31 kinds of values in water system and 32 kinds of values in air-conditioning system were developed. In this study, the software drawing 13 kinds of quantity of state on air properties as ideal gas and analyzing 25 kinds of values in any air system was developed. The 13 kinds of quantity of state on air properties are temperature, pressure, specific volume, specific internal energy, specific enthalpy, specific entropy, specific exergy, exergy ratio, density, isobaric specific heat, isochoric specific heat, ratio of specific heat, and velocity of sound, and the 25 kinds of values including 13 kinds are mass flow rate, volume flow rate, internal energy flow rate, enthalpy flow rate, entropy flow rate, exergy flow rate, heat flow rate, power output, power efficiency, reversible work, lost work, and relative humidity. The developed software can draw any range of chart and analysis any state or process on air system. Also, this supports various document-editing functions such as power point. We wish to this chart is a help to design, analysis, and education in air system field.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.84-93
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• 2001

The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial temperature distribution and the radial temperature distribution in internal space of a tube. From the study, following conclusive remarks can be made. Average flow rate that flows into a tube is in proportion to square root of inlet pressure. As inlet pressure increases axial and radial temperature distribution in the inner space of vortex-tube increase. As mass flow rate ratio change, separation point moves.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.9-17
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• 2021

Six shear coaxial injectors with different recess length and taper angle were manufactured. Cold-flow tests on the injectors were performed at room temperature and pressure using water and air as simulants. By changing the water mass flow rate and air mass flow rate, spray images were taken under single-injection and bi-injection. Breakup length and spray angle were analyzed from instantaneous and averaged spray images using image processing techniques. For all the injectors, the breakup length generally decreased as the momentum flux ratio increased at the same gas mass flow rate. The injectors with 7.5° taper angle usually had the longest breakup length and the smallest spray angle. When the taper angle was 15° or more, it hardly affected breakup length and spray angle. The recess length did not influence breakup length but its effect on spray angle depended on the taper angle.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.239-244
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• 2006

As an effective means to convey crushed materials from seabed to onboard ship, air-lift pump provides a reliable mechanism due to its simple configuration and easy-to-operate principle. The present study is focused on fundamental investigation of related performance through analysis program based on the gas-liquid two-phase flow in circular pipes. It is summarized as important result that an optimum air mass flow rate exists for the maximum lifted liquid mass flow rate in terms of a given submergence rates.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.10
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• pp.895-900
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• 2004

With the phaseout of CFC and HCFC refrigerants, refrigeration and heat pump systems must be redesigned to match and improve system performance with alternative refrigerants. A generalized flow model for predicting mass flow rate through short tube orifices is derived from a power law form of dimensionless parameters generated by Pi-theorem. The database for developing the correlation includes extensive experimental data for R12, R22, R134a, R407C, R410A, and R502 from the open literature. The correlation yields an average deviation of $0.3\%$ and a standard deviation of $6.1\%$ based on the present database. In addition, rating charts for predicting refrigerant flow rate through short tube orifices are generated for R12, R22, R134a, R407C, R410A, and R502.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.947-954
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• 2015

The homogeneous coating of a flexible film that is applied to dye-sensitized solar cells is related to the performance and durability of the product. The applied coating is obtained from the uniform temperature distribution and the mass flow rate in the nozzle of the hot air dryer. In this study, we determine the uniform temperature distribution and mass flow rate of each nozzle by performing numerical simulations to understand how various factors affect the performance of the hot air dryer. The numerical model is composed of the momentum equation for flow motion and the energy equation for temperature. In addition, we compare the numerical results to the experimental results to validate the model. Based on the results, the round-hole plate inside the hot air dryer significantly affects the uniform temperature and the mass flow rate.