Jeong-Tae Kwon

A modeling of in-tube condensation heat transfer for a turbulent annular film flow with liquid entrainment

Abstract An analytical model is developed for condensation heat transfer coefficients for a turbulent annular film flow in tubes. This calculation model not only incorporates a new turbulent eddy viscosity profile modified from the Blangetti and Schlunder model but also liquid entrainment effect. In order to assess the prediction capability of the calculation model, an experiment was performed for measurement of condensation heat transfer coefficients of R22 in horizontal smooth tubes. The calculated condensation heat transfer coefficients of R22 were compared with present experimental data and some existing correlations. From the present analysis and experiment it is found that incorporating the effect of liquid entrainment into the calculation model gives better prediction capability for in-tube condensation heat transfer coefficients. Also, the proposed turbulent eddy viscosity model gives better prediction capability for the condensation heat transfer coefficients than that of the Blangetti and Schlunder model.

Study on the Immersion Corrosion Characteristics of Thermal Spray Coating for Sea Water Heat Exchanger

Abstract In the present study, immersion corrosion characteristics of Zn and Al thermal spray coating with sealer for the seawater heat exchanger are experimentally investigated. Total 8 coating types of Zn and Al thermal spray coating with silicone and epoxy sealer were tested with immersion corrosion testing in 80℃3.5%w NaCl solution and compared the corrosion characteristics between each coatings. To investigate the corrosion characteristics of the specimens, AC impedance, SEM, and thermal diffusivity were acquired and analyzed. As a result, on the surface of the specimens with silicone and epoxy sealer, blister did not occurred, so the sealers might be effective at increasing the corrosion resistance of the specimens immersed in the NaCl solution. Key Words : Thermal spray coating, Impedance, Resistance, Sea water, SEM 본 연구는 2013년 해양수산부의 재원으로 한국해양과학기술진흥원의 지원을 받아 수행된 “CO2 해양지중저장 기술개발” 및 “해양심층수의 에너지 이용기술개발”의 연구결과로 연구비 지원에 감사드립니다. * Corresponding Author : Young-Chul Kwon(Sunmoon Univ.)Tel: +82-10-8523-0923 email: yckweon1@sunmoon.ac.krReceived November 25, 2013 Revised (1st December 19, 2013, 2nd January 3, 2014) Accepted January 9, 2014

Experimental Study on Corrosion and Thermal Conductivity Characteristics of Thermal Spray Coating for Sea Water Heat Exchanger

In the present study, the characteristics of corrosion and thermal conductivity of thermal spray coatings for seawater heat exchangers were examined experimentally. The coating types of theZn and Al thermal spray coatings with additional epoxy and silicone sealers were tested. To examine the corrosion characteristics of the thermal spray coating, the cyclic voltamogram curve was measured followed by SEM imaging for surface characterization. The laser flash method was usedto measure the thermal conductivity of the specimen. The conductivity test results showed that thermal conductivity decreased by3 ~ 4% with the silicone sealer and decreased by 70 ~ 75% with the epoxy sealer

Experimental Study on Heat Transfer and Pressure Drop of Heat Exchangers for Cooling Fan Coil Unit

An experimental study has been performed to investigate the air-side capacity and pressure drop of the fin-tube heat exchanger for a fan coil unit under a cooling condition. The experimental data of five kinds of slit fin-tube heat exchangers were measured using an air-enthalpy calorimeter and a constant temperature water bath. Cooling capacities at the air and water rating flow rates were larger at the lower inlet water temperature. With increasing the water flow rate, the cooling capacity increased at the constant rate. Under the lower inlet water temperature, since the condensate was generated more on the fin-tube surface, the air-side pressure drop of the heat exchanger was larger.

Experimental Study on Coating Corrosion Characteristics of Heat Exchanger for Sea Water

Abstract In the present study, coating corrosion characteristics of the heat exchanger for sea water are experimentally investigated. Coating types by a teflon, an electrodeposition and a ceramic+silicon were tested and compared with the corrosion characteristics of an aluminum. For the acceleration of corrosion by sea water, the temperature of sea water 70℃ and the concentration of salt 3.5% were considered. And the specimens were immersed in sea water during 9 weeks. Coating corrosion characteristics were measured by using the impedance method and SEM. Experimental results showed that polarization resistances obtained from Bode plot were related to the corrosion resistance of coating types, and the corrosion resistance of double coating were maintained during 4 weeks. From SEM photograph, we saw that blisters was generated on the interface between metal and coating. Key Words : Coating, Impedance, Immersion, Resistance, Sea water, SEM 본 연구는 해양수산부에서 지원하는 “해양심층수의 에너지 이용기술개발” 결과로 연구비 지원에 감사드린다.

The Analysis of Flow Characteristics of Conductive Liquid Metal Using TLIM Electromagnetic Pump

This paper presents the flow characteristics in the fluid circulation loop using the tubular type linear induction motor(TLIM) electromagnetic pump. A TLIM of thrust 40[N] is analyzed using the equivalent and genetic algorithm for the system The flow characteristics are analyzed by coupling the Maxwell equations with the Navier-Stokes equation with the thrust. The analysis algorithm is developed for analyzing the liquid metal flow in the system for laminar and turbulent flow. And the effect of thrust is analyzed for the flow characteristics.