• Proceedings of the KSME Conference
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• 2003.11a
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• pp.25-30
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• 2003

Several desiccant cooling systems have been developed in terms of cost and performance. In this study a fin-tube exchanger has been used for liquid desiccant dehumidification system. This dehumidifier has been designed to study the absorption characteristic of the aqueous triethylene glycol(TEG) solution which has the flow range from 20 to 50 LPM. The dehumidifier performance characteristic of working factor variables such as inlet solution flow rate, air flow rate, solution concentration, solution temperature, brine temperature, air temperature and inlet air relative humidity has been analyzed. The result of this experiment can provide useful data for hybrid air conditioning system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.8
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• pp.1077-1086
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• 2001

An experimental study is performed to investigate the characteristics of vortex shedding behind a circular cylinder with serrated fins using hot-wire anemometer. Strouhal numbers which are calculated using outer diameter of a circular cylinder with serrated fins are higher than that of a circular cylinder. Fin thickness and pitch are closely related with vortex shedding frequency and play increasing or decreasing vortex shedding after transient Reynolds number. Strouhal numbers using effective diameters which are proposed in this paper agree with that of a circular cylinder. After transient Reynolds number, a trend of Strouhal number can be estimated by checking the ratio of effective diameter to inner diameter.

• Korean Journal of Materials Research
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• v.16 no.2
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• pp.111-115
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• 2006

High-finned tubes have good thermal conductivity and have better cooling efficiency than plain tubes or low-fined tubes due to bigger air contact area. During high-fined tubes are manufactured by roll forming, the main technique is illustrated to optimizing primary material(copper pipe), optimized die matrix designing technique for roll forming, control manufacturing speed to develop productivity etc. In this study, a roll forming system was developed in oder to produce high-finned tube. Also a multi-step roll forming die was designed & built to produce high-finned tube that has over 10 mm fin height. And then, roll forming test using copper pipe was performed to produce high-finned tube. Roll forming process for producing highfinned tube was optimized by analyzing and adjusting misrostructure, hardness, and surface roughness of roll formed high-fined tube.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.282-284
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• 2011

Based on graphene oxide and multi-walled carbon nanotube layers, a wireless bi-layer actuator that can be remotely controlled with an electromagnetic induction system has been developed. The graphene-based bi-layer actuator exhibits a large one-way bending deformation under eddy current stimuli due to asymmetrical responses originating from the temperature difference of the two different carbon layers. In order to validate one-way bending actuation, the coefficients of thermal expansion of carbon nanotube and graphene oxide are mathematically formulated in this study based on the atomic bonding energy related to the bonding length. The newly designed graphene-based bi-layer actuator is highly sensitive to electromagnetic wave irradiation thus it can trigger a new actuation mode for the realization of remotely controllable actuators and is expected to have potential applications in various wireless systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.2
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• pp.87-93
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• 2009

Slim telecommunication cabinet cooler, equipped with parallel flow heat exchangers and operating with R-22, is developed. The performance is compared with imported one, equipped with fin-tube heat exchangers and operating with R-134a. Test results show that the newly-developed cooler increases the cooling capacity by 6% and EER by 33%. The refrigerant charge for the developed cooler is 500g compared with 1250g for the imported one. The adoption of parallel flow heat exchanger appears to have reduced the refrigerant charge. In addition, it is shown that the reduced air flow rates through parallel heat exchangers as compared with those through fin-tube heat exchangers are beneficial to the reduction of the equipment noise.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.8
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• pp.588-595
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• 2014

Carbon nanomaterials such as fullerene, carbon nanotube and graphene are representative nanomaterials and widely used in various fields. Carbon nanomaterials can be exposed to environments during their production, usage and disposal, spreading to different systems and posing a great threat to various ecological receptors. Researches are conducted in order to determine the possibility of groundwater exposure to carbon nanomaterials due to their release and passage through soils. If soils can play a significant role in limiting the transport of carbon nanomaterials, the possibility of groundwater exposure to carbon nanomaterials can be reduced greatly. This review paper presented the research works performed for the mobility of carbon nanomaterials in soil media. Also, the paper provided the factors affecting the transport of carbon nanomaterials in soil media along with the DLVO theory/colloid filtration theory/transport model, which are used to describe the transport of carbon nanomaterials in soil media. Recently, production of carbon nanomaterials and their commercial and environmental applications increase rapidly in Korea. Therefore, researches regarding the fate and transport of domestic carbon nanomaterials in soil environments should be performed in various environmental conditions.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1025-1030
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• 2008

We develop heat exchanger modules for a multi-burner boiler. The heat exchanger module is kind of a heat recovery steam generator (HRSG). This heat recovery system has 4 heat exchanger modules. The 1st module consists of 27 bare tubes due to high temperature exhaust gas and the others consist of 27 finned tubes. The maximum steam pressure of each module is 10 bar and tested steam pressure is 4 bar. In order to test these heat exchanger modules, we make a 0.5t/h flue tube boiler (LNG, $40\;Nm^3/h$). The test results of 100% boiler load show that heat transfer rate of 1st module is 49.7 Mcal/h which is 34% of total heat transfer rate and that of 2nd module is 82.6 Mcal/h which is 57% of total heat transfer rate. The reason of higher the heat transfer rate of 2nd module than that of 1st module is that the 2nd heat exchanger module has finned tubes instead of bare tube. The boiler load 50% results show that only 2 heat exchanger modules are needed to extract the heat from the flue gas to water. From this result, it is very important of optimum design of the first finned tube among all water tubes.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.1
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• pp.33-44
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• 1994

This work studies for boiling and condensation heat transfer performance of trapezoidally shaped integral-fin tubes having fin densities from 748fpm to 1654fpm. For comparison, tests are made using a plain tube having the same inside and outside diameter as that of the root of fins of finned tubes. Hahne's theoretical model and Webb's theoretical model are used to predict the R-11 boiling heat transfer coefficient and condensing heat transfer coefficient respectively for plain tube and all integral-fin tubes. Experiments are carried out using R-11 as working fluid. This work is limited to film-wise condensation and pool boiling on the outside surface of plain tube and 4 low integral-fin tubes. In case of condensation, the refrigerant condenses at saturation state of 32$^{\circ}C$ on the outside tube surface cooled by coolant and in case of boiling. the refrigerant evaporates at saturation state of 1bar on the outside tube surface. The amount of non-con-densable gases in the test loop is reduced to a negligible value by repeated purging. The actual boiling and condensing processes occur on the outside tube surfaces. Hence the nature of this surface geometry affects the heat transfer performances of condenser and evaporator in refrigerating system. The condensation heat transfer coefficient of integral-fin tube is enhanced by both extended tube surface area and surface tension. The ratio of the condensation heat transfer coefficients of finned to plain tubes is greater than that of surface area of finned to plain tubes, while ratio of the boiling heat transfer coefficient of finned to plain tubes shows reverse result. As a result, low integral-fin tube can be used in condenser more effectively than used in evaporator.

• Journal of the Korean Society of Food Science and Nutrition
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• v.15 no.4
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• pp.51-55
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• 1986

The general bag for powder materials such as sugar, salt and detergent used at present is a simple rectangular bag. In the practical uses, it has a lot of faults: it is difficult to reseal after partial usages, occurrence of loss in the case of sharing or adding, difficult for measured uses. Author made a new type of the measuring bag for powder materials in order to improve the problems. The new type of the bag for powder materials consists of a body, fall-induced tube with length scale line, and a pin to open and reseal. It shows various effectiveness: measured use$({\pm}0.6g)$ of powder materials, eatings don't occur during long period after opening, and no skin contamination during use of detergent. Consequently, the new one Is suitable for the measured use of powder materials such as sugar, salt, detergent, MSG and so on.

• Corrosion Science and Technology
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• v.22 no.6
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• pp.435-446
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• 2023

Corrosion behaviors of laser-welded super duplex stainless steel (SDSS) tubes after exposure to an actual power plant environment for one year and those of fin-tube welded SDSS were evaluated. Results showed that corrosion damage on the back side of the SDSS tube in the direction of hot air was higher than that on the front side regardless of weldment location. However, corrosion damage showed no difference between weldment and base metal due to recovery of phase fraction in the weldment through post weld heat treatment (PWHT). Nevertheless, the SDSS tube showed severe corrosion damage along grain boundary due to surface phase transformation (δ → γ) and Cr₂N precipitation caused by PWHT with a high N₂ atmosphere. Corrosion resistance of the SDSS tube was recovered when degraded surface was removed. Corrosion sensitivity of a fin-tube increased significantly due to pre-existing crevice, unbalanced phase fraction, and σ phase precipitation adjacent to the fusion line. Although corrosion resistance was improved by recovered phase fraction and sufficient dissolution of σ phase during PWHT, corrosion reaction was concentrated at the pre-existing crevice. These results suggest that welding conditions for fin-tube steel should be optimized to improve corrosion resistance by removing pre-existing crevice in the weldment.