• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.14 no.1
• /
• pp.31-38
• /
• 1985

By using the hollow shaft with $0.5^{\circ}$ internal taper, ball valve and rubber packing, charging the working fluid at engineering vacuum degree (vacuum pressure higher than 1 torr) and carrying out experiments, it was investigated the performance of rotating heat pipe with variant operating conditions. In this experiment, it was shown that it is impossible the internal liquid flow was laminar film flow which agree with the assumption of present theoretical analyses, but the internal vorticity makes the heat transfer increase and for the maximum heat transfer there is optimal mass loading for the given heat pipe geometry and operational conditions.

• Solar Energy
• /
• v.18 no.4
• /
• pp.101-110
• /
• 1998

The purpose of this research is to study the charateristics and manufacture of a composite heat pipe system with rotational and static pipe. A composite heat pipe system were tested to obtain the relationship between the expansion injector and auxiliary expansion for the motion of the working fluid by the experimental results. In addition the heat transport characteristics were found based on wall temperature of rotor, expansion injector, storage tank and vapor temperature. Water is used as working fluid of heat pipes. As the results of experiments, the composite heat pipe was operated for long times, 10 hour above with various rotational speed in performance. There were a few unexpected data by the capillary pumped loop at small working fluid, but as a whole the testing was successful.

• Solar Energy
• /
• v.12 no.3
• /
• pp.116-125
• /
• 1992

By using the heat pipe with a dished evaporator and a screwed groove condenser, the heat transfer characteristics have been investigated by measuring temperature distributions of wall and vapor for various thermal inputs at rotative and stationary cases. The results show that the heat transfer characteristics of this pipe have better than those of simple heat pipe. The heat transfer of the heat pipe is increased by increasing thermal input and revolutions per minute.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 2000.04a
• /
• pp.189-196
• /
• 2000

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1630-1633
• /
• 2003

Hair pin bending machine is pipe forming machine consisting of heat exchanger product system. Hair pin produced by these machine is pathway of refrigerant and play a important role improving the performance and productivity of heat exchanger. The core technology of hair pin bending machine is forming the straight pipe into U-type without any defaults. Therefore, this paper study the relation between the pipe bending forming and the shape and position of mandrel using the elastic-plastic finite element analysis and provide a foundation technology for which developing the hair pin bending machine. The results are followed 1. Mandrel located in front of rotating center of bending die minimized the circular shape variation of copper pipe. 2. Diameter change of mandrel hardly effect the pipe shape.

• Journal of Energy Engineering
• /
• v.8 no.2
• /
• pp.325-332
• /
• 1999

When a rotating heat pipe is in operation, liquid condensate returns from the condenser to the evaporator along the inside surface by both components of gravitational and centrifugal forces. It was known that its performance was largely dependent on how to increase the flow rates of condensate and keep the condensate film thickness as thin as possible. Most of research works were focussed on this goal, and various inner wall structures such as tapered wall, stepped wall or coil inserted pipe etc. were developed. In the present study, a stepped wall structure with 3 internal grooves in the condenser and adiabatic zone was examined. For this system, the condensate would flow down to the evaporator through the grooves, resulting a reduced film thickness over the condenser surface. Experimental data showed an enhancement of heat transfer coefficient in the condenser zone. An analytical solution to the condensate film thickness showed that the analytically calculated values of heat transfer coefficient were considerably higher than the experimental data.

• Solar Energy
• /
• v.13 no.2_3
• /
• pp.120-132
• /
• 1993

The purpose of this research is to study the characteristics of heat transfer in composite rotary heat pipe as modeled turbine rotating by a finite element analysis and experiment. Nu number, Re number, Pr number and dimensionless condensate layer thickness by thermal input and revolutions per minute were given as analysis factors. The comparison between calculated and experimental data showed similar tendency. Therefore the analysis method may be useful to predict the performance of composite heat pipe. The resistance on heat pipe showed the best effect of heat transfer by film condensation, by decreasing film condensation, the heat transfer rate from condenser was increased rapidly. The dimensionless condensate layer thickness according to Re number at given Pr number showed constant values, the dimensionless condensate layer thickness is proportionate to the square root of inverse of revolution number per minute. In this study Nu=A$({\delta}({\omega}/v)^{-1/2}Re^B)$ is used to the convection heat transfer coefficient and A=0.963, B=0.5025 were obtained as analysis predicts.

• Journal of the Korean Magnetics Society
• /
• v.23 no.2
• /
• pp.77-81
• /
• 2013

The objective of this study is experimentally to investigate natural convective heat transfer characteristics of the ferrofluid for a concentric annuli under rotating magnetic field with variations of the revolution and the magnetic field strength. The rotating magnetic field was provided by induction motor with 6 poles and 3 phases and the revolution and the magnetic field strength were controlled by an inverter driver and a voltage meter, respectively. Temperatures of the inner pipe and the outer pipe in the tested concentric annuli were maintained at $30^{\circ}C$ and $25^{\circ}C$, respectively, during the test and the direction of the rotating magnetic field was a counterclockwise. As a result, the natural convective heat transfer characteristics of the ferrofluid for a concentric annuli were increased with the rise of the revolution and magnetic field strength due to the increased heat dissipation between hot side and cold side of the concentric annuli.

• Journal of Welding and Joining
• /
• v.19 no.3
• /
• pp.334-341
• /
• 2001

The chemical and geometric effects of weld on flow-accelerated corrosion (FAC) of SA106 Gr.C low alloy steel pipe in 3.5wt% NaCl and simulated feedwater of nuclear power plant have been investigated by using rotating cylinder electrode. Polarization test and weight loss test were conducted and compared at rotating speed of 2000rpm (3.14m/s) with the variables of chemical and geometric parameters. The results showed that the chemical effects were relatively larger than the geometric effects, and the welded parts were the local anode and preferentially corroded, which could be explained by the differences between microstructural and compositional parameters. On the other hand, under active corrosion conditions, the heat affected zone were severely corroded and microstructural effects became the important role in the whole process.

• Journal of Welding and Joining
• /
• v.19 no.4
• /
• pp.391-398
• /
• 2001

MIAB welding method uses a rotating arc as its heat source and is known to be efficient in pipe butt welding. The arc is rotated around the weld line by the electro-magnetic force resulting from the interaction of arc current and magnetic field. This paper is concerned with the experiment of initial stage for process control, monitoring for weld quality, and the design of coil system which is efficient of flux generation and concentration. A coil system for the generation of magnetic flux was designed and constructed. Magnetic flux density and arc rotating behavior are important factors in MIAB welding, so the relations between these factors and process parameters were investigated. Various experiments were performed for the steel pipes(48.1mm O.D and 2.0mm thickness). The magnetic flux density is increased by increasing exciting current and decreasing gap size. The maximum of arc rotating frequency is affected by exciting current and gap size. However, the variations of arc rotating frequency during welding and then the melting process are mainly influenced by welding current. Thus, it is considered that the results of this study can be used as important data on the monitoring for weld quality and the design of efficient coil system.