• 설비공학논문집
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• 제12권6호
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• pp.533-540
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• 2000

Condensation heat transfer characteristics have been investigated experimentally when a water vapor is condensed on the outside of a horizontal copper tube in a condenser. This problem is of particular interest in the design of a LiBr-water absorption system. Hydrophilic surface modification was performed to increase the wettability on the copper tube. The optimum hydrophilic treatment condition using acethylene and nitrogen as reaction gas is also studied in detail. The results obtained indicate that the optimum reaction gas ratio of acethylene to nitrogen for hydrophilic surface modification was found to be 7 : 3 for the best condensation heat transfer. In the wide ranges of coolant inlet temperatures, and coolant mass flow rates, both the condensation heat transfer rate and the condensation heat transfer coefficient of a hydrophilic copper tube are increased substantially, compared with those of a conventional copper tube used in a condenser. It is also found that the condensation heat transfer enhancement by the hydrophilic surface modification still emains even after a hundred cycles of wet/dry processes.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2488-2498
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• 2021

The wall film-wise condensation plays an important role in the heat transfer processes of heat exchangers, refrigerators, and air conditioner. In the field of nuclear engineering, steam condensation is often utilized in safety systems to remove the core decay heat under both transient and accident conditions. In particular, passive containment cooling system (PCCS), are designed to ensure containment safety under severe accident conditions. A computational fluid dynamics (CFD) scale analysis has been conducted to calculate the heat transfer rate of the PCCS. However, despite the increase in computing power, there are challenges in the long-term transient simulation of containment using CFD scale codes. In this study, a heat structure coupling between the CFD and system analysis codes was performed to efficiently analyze PCCS. In addition, the component unstructured program for interfacial dynamics (CUPID) was improved to analyze the condensation behavior of ternary gas mixtures. Thereafter, the condensation heat transfer on the primary side was calculated using the improved CUPID and CFD code, whereas that on the secondary side was simulated using MARS. Both the coupled codes were validated against the CONAN facility database. Finally, conjugate heat transfer simulations with wall condensation in the presence of non-condensable gases were appropriately performed.

• Journal of Korean Society for Atmospheric Environment
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• 제12권E호
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• pp.19-28
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• 1996

A pore concensation-based separation technique was studied experimentally using toluene and xylene in a nitrogen stream. The removal rate of toluene and xylene on a microporous ceramic membrane was enhanced by increasing the partial pressure difference across the membrane, but the selectivity was reduced with increasing flux of nitrogen. This was found both in vacuum and pressure modes of operation. The experimental results from this study suggest that the pores mear the inlet portion of the module were filled with the organic solvent while the pores near the exit section of the module were slightly opened as the solvent concentration was depleted along the module. In the case of xylene, the rate of N$_{2}$ permeation was reduced considerably relative to toluene, resulting in a much higher separation gactor. Condensibility of xylene appeared to be higher than that of toluene, the potential for pore condensation-based separation of xylene was also found to be higher than that for toluene.

• 연구논문집
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• 통권30호
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• pp.15-23
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• 2000

In this study, develop the thermal pump using water evaporation and condensation. Vapor from heating room moves up to pumping room and press the water of pumping room. Consequently water is pumped out to water tank. Then hot vapor direct contact with cold water in condensing room after pumping process. At this time, pressure of condensing room is down to-5kPa and suck in water of tank. This pump executes self ping and good durability because of no mechanical moving parts. Thermal pump is pumped cyclic so that, this pump is not used single. Therefore thermal pump of hot water boiler used to multi-stage for stable pumping rate. As the result of performance test, the developed thermal pump proves pumping action of water evaporation/condensation. And total volume flow rate is 500liter during one hour. If three thermal pump is installed parallel, this pump can use to the hot water boiler in the 300,000kcal/h class.

• Journal of Advanced Marine Engineering and Technology
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• 제20권4호
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• pp.70-80
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• 1996

Experimental results for forced convection condensation of R-22 and R-407C inside 7.5mm ID and 4000mm length of horizontal tubes are presented. The experimental data covered total flow rate from 114.3 to 267.1kg/($m^2$.s) and quality from 0 to 1. The vapor temperature and pressure drop along the tube were measured. The pressure drop for R-407C increased with flow rate similar to that of R-22. The experimental data compared with the available perdictions for pressure drop. Based on the data a prediction method was presented for the calculation of pressure drop of R-22 alternative refrigerants.

• Transactions on Electrical and Electronic Materials
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• 제1권2호
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• pp.18-22
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• 2000

An ozone condensation system is evaluated from the viewpoint of an ozone supplier fro oxide thin film growth. Ozone is condensed by the adsorption method and its concentration is analyzed using the thermal decomposition method, The concentration of ozone exceeds 90mol% and ozone is supplied for a sufficiently long time to grow oxide thin films. Investigation of the ozone decomposition rate demonstrates that ozone can be transferred into the film growth chamber without marked decomposition. The ozone concentration is also evaluated using a quardrupole mass analyzer and the accuracy of this method is compared with the results of the thermal decomposition method.

• 설비공학논문집
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• 제17권12호
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• pp.1177-1184
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• 2005

A numerical analysis was carried out on the heat and mass transfer, and pressure drop characteristics of the modular tube bundle heat exchanger. The finite volume method with a $k-\varepsilon$ turbulence model was used for the analysis. Due to condensation, the total heat transfer rate is observed about $4\~8\%$ higher than that on dry surfaces. Total heat transfer rate increases with increase in the velocity, temperature and relative humidity of incoming air. It also increases with decreasing the aspect ratio of heat exchanger tube. The inlet velocity of cooling water has little effect on the total heat transfer when the other conditions are fixed.

• 대한기계학회논문집
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• 제18권10호
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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.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.407-418
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• 2004

Prandtl-Meyer expansion flow with homogeneous condensation is investigated experimentally and by numerical computations. The steady and unsteady periodic behaviors of the diabatic shock wave due to the latent heat released by condensation are considered with a view of technical application to the condensing flow through steam turbine blade passages. A passive control method using a porous wall and cavity underneath is applied to control the diabatic shock wave. Two-dimensional, compressible Navier-Stokes with the nucleation rate equation are numerically solved using a third-order TVD (Total Variation Diminishing) finite difference scheme. The computational results reproduce the measured static pressure distributions in passive and no passive Prandtl-Meyer expansion flows with condensation. From both the experimental and computational results, it is found that the magnitude of steady diabatic shock wave can be considerably reduced by the present passive control method. For no passive control, it is found that the diabatic shock wave due to the heat released by condensation oscillates periodically with a frequency of 2.40㎑. This unsteady periodic motion of the diabatic shock wave can be completely suppressed using the present passive control method.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1125-1139
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• 2023

The system-integrated modular advanced reactor 100 (SMART100), an integral-type pressurized water small modular reactor, is based on a novel design concept for containment cooling and radioactive material reduction; it is known as the containment pressure and radioactivity suppression system (CPRSS). There is a passive cooling system using a condensation with non-condensable gas in the SMART CPRSS. When a design basis accident such as a small break loss of coolant accident (SBLOCA) occurs, the pressurized low containment area (LCA) of the SMART CPRSS leads to steam condensation in an incontainment refuelling water storage tank (IRWST). Additionally, the steam and non-condensable gas mixture passes through the CPRSS heat exchanger (CHX) submerged in the emergency cooldown tank (ECT) that can partially remove the residual heat. When the steam and non-condensable gas mixture passes through the CHX, the non-condensable gas can interrupt the condensation heat transfer in the CHX and it degrades CHX performance. In this study, condensation heat transfer experiments of steam and non-condensable gas mixture in the natural circulation loop were conducted. The pressure, temperature, and effects of the non-condensable gas were investigated according to the constant inlet steam flow rate with non-condensable gas injections in the loop.