• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.11
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• pp.428-433
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• 2016

The fin and tube heat exchanger using a two-port tube has in air-conditioner heat exchanger because heat transfer performance. This study investigates the feasibility of a fin and tube heat exchanger using two-port copper tube by mechanical expansion. The optimum size of the tube-expanding bullet for the heat exchanger using two-port tube was through numerical calculation. The heat exchanger using a two-port tube was fabricated by mechanical expansion, and the heat exchanger performance was evaluated condensation and evaporation experiments. Compared to the heat exchanger of a conventional circular tube, the pressure drop per unit length of the heat exchanger with a two-port tube decreased. Compared to the heat exchanger using a conventional circular tube, the overall heat transfer coefficient of heat exchanger with a two-port tube increased up to 13% in the case of condensation, and up to 25% in the case of evaporation. The two-port tube heat exchanger outperforms conventional heat exchanger for air conditioner with a inner grooved circular tube.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1107-1112
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• 2006

The purpose of this study is a heat transfer coefficient test of evaporator tube in shell and tube heat exchanger by shapes, using R-404A. The experimental apparatus is designed to simulate the real heat transfer rate in one shell and tube heat exchanger. The test section is formed four type tubes that are Inner ridged tube, Corrugated tube, Turbo-C tube, Inner fin tube and shell type is formed by electrical heater. All tests were performed at a fixed refrigerant evaporator temperature at $1.5^{\circ}C,\;-3^{\circ}C$ and with mass fluxes of 29, 25 kg/hr. Heat transfer rate is calculated a enthalpy difference in test section. In experiment, heat transfer coefficient measured one by one and electrical heaters are supplemented by evaporator.

• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.247-252
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• 2008

By using the transmission anode x-ray tube developed to apply to the hand-held XRF equipment, we carried out XRF experiment and evaluated the influences of the x-ray tube on XRF spectra. XRF data, which is measured using the W-target and Rh-target tube, were good agreements with the known results. FWHM of Fe $K_{\alpha}$-line measured by W-target tube with the 35 kV-tube voltage and the $40{\mu}A$-tube current was 180 eV. This result reveals that our XRF equipment using the transmission anode x-ray tube is enough for a qualitative analysis of materials. By comparison XRF data with the integrated intensity of x-ray tube, it was confirmed that Rh-target tube is better than W-target tube for application to the hand-held XRF equipment.

• Magazine of the Korean Society of Agricultural Engineers
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• v.16 no.2
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• pp.3410-3419
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• 1974

The purpose of this study is to find out the correlation between pumping rates and influential factors in the tube wells for irrigation through the analysis of various statistical data of the existing tube wells for irrigation and pumping tests. Statistical data of the existing tube wells for irrigation were collected from the authorities concerned, and pumping tests were carried out for twelve tube wells. The results of this study are summarized as follows: 1. The drilled tube wells are the most useful among various tube wells in securing pumping rates. 2. The enlargement of well diameter or the improvement of pumping equipments is necessary in drilled tube wells with pumping rates more than 806 ㎥/day, and the adjustment of foot valves or the special control of pumping equipments is necessary in tube wells with pumping rates less than 300 ㎥/day. 3. The choking of aquifer and slits can be prevented by removing earth and sand piled in tube wells. 4. The increase of well loss and the destruction of aquifer can be prevented by determining the optimum pumping rates through the step draw down tests. 5. The thickness of gravel packing is rather thin in drilled tube tube wells. 6. High pamping rates can be gained by deepening the depth of tube wells in the place the ground water storage is abundant, the thickness of aquifer is thick. and the depth of tube wells is deep. 7. Higher pumping rates can be obtained by constructing tube wells in the place where the drawdown is little and the coefficient of transmissibility is large.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.165-168
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• 2011

In this paper, the hybrid tube expander unit for fin and tube type heat exchanger are developed by means of enlarging and inserting the smooth tube with a small diameter to a finned tube having larger diameter. In other word, the tube expander tool that is easy to attach and remove from tube is developed. The hybrid tube expander unit developed in this study can move easily and enlarge the tube without fixing at tube sheet. Also, this unit has a function removing scales inside tube by replacing a tube expander ball.

• International Journal of Railway
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• v.2 no.4
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• pp.170-174
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• 2009

Super speed tube train is introduced to increase the speed of ground transportation. The super speed tube train levitates magnetically and runs in a partial vacuum tube, which can reduce the air resistance significantly. However, the strong magnetic force enough to propel the massive train can affect to the tube infrastructure. In this paper, authors have analyzed the leakage flux patterns and induced eddy current on the tube by using 3-dimensional Finite Element Method. These effects are investigated, especially by varying the materials and diameters of the tube. From the simulation results, the aluminum tube with the diameter of 3[m] is needed to be concerned because the induced eddy current produces joule heat, raises the inside temperature of the tube, and might be able to lead to electro-chemical corrosion on the tube, consequently reduce the durability.

• Journal of Fisheries and Marine Sciences Education
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• v.4 no.1
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• pp.47-61
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• 1992

An experimental study was carried out to investigate the condensation performance for the horizontal cylindrical heat transfer tube with various fin attached using R-11 vapor. The heat transfer tube used in this study was supplied by SUNG HYUNG METAL CO., LTD. Four different types of heat transfer tubes (plain tube, SH-CYR tube, thermocor tube and thermoexcel tube) were used. Each tube was surrounded by circular acrylate tube, and R-11 gas heated by boiler flows into the acrylate tube. Cooling water counter-flows in heat transfer tubes. Heat transfer coefficient of the plain tube from measured data was compared with those of three other tubes. The results are summarized as follows: 1. As the cooling water temperature decreased, the liquid film of R-11 turned to droplet drop on the top surface of the horizontal tube. 2. Heat transfer coefficient calculated theoretically was higher than that obtained from the experimental data. 3. As far as the condensation concerns the thermocor tube is the highest, the SH-CYR tube is the second, and the thermoexcel tube is the third excluding the plain tube.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.359-362
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• 2008

In this study, friction test was proposed to obtain coefficient of friction between tube and die in expansion zone of tube hydroforming and friction coefficients were evaluated at different materials, viscosity of lubricants and internal pressures. For this study, STKM11A and SUS tubes were prepared. The tube was expanded by an internal pressure against the tool wall. The tube was expanded by an internal pressure against the tool wall. By pushing the tube through the tool, a friction force at the contact surface between the tube and the tool occurs. From the measured geometries and FE analysis, the friction coefficients between tube and die at the expansion zone in tubular hydroforming can be estimated. The effects of the various internal pressures, viscosity of lubricants, tube materials and tube thickness on friction coefficients are discussed.

• Transactions of Materials Processing
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• v.19 no.7
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• pp.405-410
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• 2010

Double layered tube that has been used for transportation and oil piping system is occasionally exposed to elevated temperature. The change in stress state at elevated temperature is important for the safe design of double layered tube. In this study, the variation of stress state for hydroformed double layered tube of which inner tube is stainless steel and outer tube is mild steel has been analytically analyzed. To characterize the thermal stress at elevated temperature, analytical model to provide thermal stresses between outer tube and inner tube was developed by using theories of elasticity and Lame equation. The feasibility of analytical model is verified by finite element analysis using ANSYS $CLASSIC^{TM}$, commercially available code. The variation of thermal stress at various thickness combination of inner and outer tube has also been investigated by proposed analytical model.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.7
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• pp.553-559
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• 2012

A plate-fin heat exchanger is a type of heat exchanger widely used in air conditioners, and tubes and fins are tightly assembled by the mechanical expansion process of tubes. The tube expansion process deforms the grooves inside the tube, and the groove shapes also affect the adhesion between tubes and fins. In this study, the adhesion and heat transfer performance affected by the tube expansion of the non-uniform groove shape tube with different heights are investigated by both analysis and experiments. From the analysis method, it was shown that the contact pressure of non-uniform groove tube is higher than that of the uniform groove tube, and the most appropriate high groove number of the non-uniform groove tube is designed for the maximum contact pressure. From the experimental results, the decreasing rate of the condensation heat transfer coefficient is smaller in the non-uniform groove tube with different heights, compared to the conventional uniform groove tube. Also, the air-side heat transfer coefficient of the non-uniform groove tube with different heights is higher than that of the uniform groove tubes.