• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.68-78
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• 1999

Heat transfer performance is studied for boiling and condensation of R-11 on integral-fin tubes. Nine tubes with trapezoidal integral-fins having fin densities from 748 to 1654fpm and 10,30 grooves and finned tubes with caves of 0.55 and 0.64 mm height respectively are tested. in case of condensation CFC-11 condensates at saturation stat of 32$^{\circ}C$ on the outside surface cooled by inside cooling water flows. And in case of boiling the refrigerant evaporates at a saturation state of 1 bar on the outside tube surface and heat is supplied by hot water which circulates inside of the tube,. The tube having fin transfer coefficient concerns fin tubes with caves show higher valve than low fin tube having find density of 1299fpm and 30grooves. The overall heat transfer coefficient of fin tube with caves is about 5155 W/mK at 2.8m/s of water velocity, The value is abuot 2.7 times higher than plain tube and 1.3 times higher than low fin tube having fin density of 1299fpm and 30 grooves.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.65-65
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• 1999

Heat transfer performance is studied for boiling and condensation of R-11 on integral-fin tubes. Nine tubes with trapezoidal integral-fins having fin densities from 748 to 1654fpm and 10,30 grooves and finned tubes with caves of 0.55 and 0.64 mm height respectively are tested. in case of condensation CFC-11 condensates at saturation stat of 32℃ on the outside surface cooled by inside cooling water flows. And in case of boiling the refrigerant evaporates at a saturation state of 1 bar on the outside tube surface and heat is supplied by hot water which circulates inside of the tube,. The tube having fin transfer coefficient concerns fin tubes with caves show higher valve than low fin tube having find density of 1299fpm and 30grooves. The overall heat transfer coefficient of fin tube with caves is about 5155 W/mK at 2.8m/s of water velocity, The value is abuot 2.7 times higher than plain tube and 1.3 times higher than low fin tube having fin density of 1299fpm and 30 grooves.

• Journal of the Korean housing association
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• v.15 no.2
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• pp.107-115
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• 2004

The objective of this study is to show the system Integrations and control method for operation of the Radiant Floor Cooling. The systems for radiant floor cooling system consist of only using the radiant floor cooling and the radiant floor cooling integrated with a dehumidification system. And the study is suggested control method with composed radiant floor cooling system through simulations. Radiant floor cooling systems compose of four main parts: an existing radiant heating panel, manifold, cooling source and controller, and sensors. If dehumidifying or supplementary cooling is needed, additional equipments such as PAC and AHU are needed. Simulation results show that control method only using radiant floor cooling system can prevent condensation and set room air temperature with the exception of hot and humid periods and control method using the radiant floor cooling integrated with a dehumidification system is comfort thermal environments and can reduce the cooling load quickly, moreover, show comfort control method to meet various cooling operation situations.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.567-578
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• 2015

In a nuclear reactor containment, wall condensation forms with noncondensable gases and their accumulation near the condensate film leads to a significant reduction in heat transfer. In the framework of nuclear reactor safety, the film condensation in the presence of noncondensable gases is of high relevance with regards to safety concerns as it is closely associated with peak pressure predictions for containment integrity and the performance of components installed for containment cooling in accident conditions. In the present study, CUPID code, which has been developed by KAERI for the analysis of transient two-phase flows in nuclear reactor components, is improved for simulating film condensation in the presence of noncondensable gases. In order to evaluate the condensate heat transfer accurately in a large system using the two-fluid model, a mass diffusion model, a liquid film model, and a wall film condensation model were implemented into CUPID. For the condensation simulation, a wall function approach with a heat/mass transfer analogy was applied in order to save computational time without considerable refinement for the boundary layer. This paper presents the implemented wall film condensation model, and then introduces the simulation result using the improved CUPID for a conceptual condensation problem in a large system.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.56-68
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• 2016

Extensive researches have been carried out for enhancing the safety of nuclear power plants and, especially, the development of passive cooling systems, such as passive containment cooling system (PCCS) and passive residual heat removal system, is increasingly important, where condensation is a crucial heat transfer mechanism. Recently, Ahn & Yun et al. developed a horizontal in-tube condensation heat transfer model as one of the activities for the PCCS development. In this work, we implemented the Ahn & Yun 's condensation heat transfer model into the MARS code and assessed it using the PASCAL experimental data. Based on the results of the assessment, we identified the limitations of the Ahn & Yun 's model and suggested a modified Ahn & Yun 's model, and assessed the model using various experimental data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.1
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• pp.21-28
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• 2017

Curtain-wall systems have been widely applied to buildings because of their lightweight and constructability characteristics. However, as curtain-wall systems include many building materials, vapor barriers can become damaged and condensation can occur. Due to the material properties of stone curtain-walls, the external appearance and structure of a building could be damaged and the insulating performance of the curtain-wall could be worse. Natural ventilation using an air cavity in a curtain-wall is expected to be effective for the prevention of condensation in inner walls and for the reduction of building cooling energy use in the summer. The purpose of this experimental study is to analyze the influence of a ventilated cavity on the insulating performance of a curtain-wall and the ventilated cavity depth and ratio of top opening needed to prevent condensation in a curtain-wall.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1081-1086
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• 2006

Curtainwall systems has been applied to buildings widely for constructability. However, as cutainwall system include many building materials, they become to damaged vapor barrier and incur condensation. Natural ventilation of an air cavity in a curtainwall is expected to be an prevention of condensation in inner wall and reduce cooling energy in summer. The objective of this experimental study is to evaluating the insulation and condensation Performance of ventilated curtainwall with ventilated cavity depth and ratio of opening area.

• Nuclear Engineering and Technology
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• v.41 no.8
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• pp.1015-1024
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• 2009

The presence of a non-condensable gas can considerably reduce the level of condensation heat transfer. The non-condensable gas effect is a primary concern in some passive systems used in advanced design concepts, such as the Passive Residual Heat Removal System (PRHRS) of the System-integrated Modular Advanced ReacTor (SMART) and the Passive Containment Cooling System (PCCS) of the Simplified Boiling Water Reactor (SBWR). This study examined the capability of the Multi-dimensional Analysis of Reactor Safety (MARS) code to predict condensation heat transfer in a vertical tube containing a non-condensable gas. Five experiments were simulated to evaluate the MARS code. The results of the simulations showed that the MARS code overestimated the condensation heat transfer coefficient compared to the experimental data. In particular, in small-diameter cases, the MARS predictions showed significant differences from the measured data, and the condensation heat transfer coefficient behavior along the tube did not match the experimental data. A new method for calculating condensation heat transfer coefficient was incorporated in MARS that considers the interfacial shear stress as well as flow condition determination criterion. The predictions were improved by using the new condensation model.

• Journal of Power System Engineering
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• v.21 no.2
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• pp.64-69
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• 2017

The purpose of this study is to investigate the performance characteristics of seawater cooling system for a fishing vessel. The circulation amount of refrigerant, condensation capacity, evaporation capacity, compression work and coefficient of performance(COP) were analyzed as the heat source temperature changed. The experimental setup consisted of an open-type compressor, a shell&tube type condenser, an evaporator and an expansion valve. The heat source was controlled by a constant temperature chamber. The main results of this study are summarized as follows. The condensation capacity increased with increasing heat source temperature, and it was confirmed that the effect of circulating amount of refrigerant was dominant. The amount of heat for vaporization was almost constant even though the temperature of the heat source increased. On the other hand, the compression power was increased. This is because the compression ratio increases as the condensation pressure, the enthalpy difference between inlet and outlet, the amount of circulating refrigerant increases. The performance coefficient of this system showed a tendency decreasing with increasing heat source temperature. Therefore, the basic data of the seawater cooling system for the maintenance of the catch line of the shore fishing boats was acquired through this study, and it is considered that it will be sufficient for the actual design.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.164-169
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• 2001

There is a chilled ceiling panel which carries out the air conditioning by radiation and convection between the room and cold ceiling panel surface. In order to verify heat transfer characteristics between them in cooling system with radiant chilled ceiling panel, analytical and experimental studies were performed for various design and operating parameters such as tube space and diameter, inlet water temperature, mass flow rate, cooling load, and so on. In this study, we found that the tube space and inlet water temperature were more important elements than the tube diameter and water flow rate for the performance of radiant chilled ceiling panel. The cooling capacity of the radiant chilled ceiling panel had the maximum value of $65W/m^{2}$ because the highest cooling capacity was limited by the condensation on the panel surface. The results of comparison between numerical analysis and experiment showed a resonable agreement qualitatively, especially for low cooling capacity.