• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.2
• /
• pp.9-15
• /
• 2013

An effect of a spiral turbulent ring, so-called Shchelkin spiral, on a detonation performance was studied experimentally for acetylene and oxygen mixture. A couple of dynamic pressure transducers were used to calculate a detonation wave velocity by a time difference between two pressure peaks. In addition, impulse was measured by a load cell and the impulse was used to analyze the spiral effect on the detonation performance. A CFD analysis was adopted to calculate mass flow rates of the propellants and the minimum filling time. The maximum velocity and pressure were measured at the equivalence ratio of 2.4, and the measured values showed similar trend to C-J conditions calculated from CEA. For the shorter chamber with the short spiral, the maximum detonation velocity was appeared. In contrast, the longer chamber without the spiral showed the maximum thrust performance.

• Journal of the Korean Society of Visualization
• /
• v.7 no.2
• /
• pp.72-72
• /
• 2010

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1002-1007
• /
• 2009

The research are performed to check the characteristics of the ice slurry transport system for the district cooling. The system are installed at the 1st floored building which is as large as the $1204\;m^2$ ($86\;m{\times}14\;m$). Three kinds of heat exchanger are selected, such as, plate, spiral and shell & tube type, to apply to the ice slurry systems. Experiment was done in the two cases. The first case, circulation water flow fixed at the design conditions for the state to change the flow of the supply of ice slurry. The second case, Ice slurry flow fixed at the design conditions for the state to change the flow of circulation water. Both side of Energy balance was calculated. The performance of plate heat exchanger is higher than others and it's enthalpy effectiveness is higher too.

• Proceedings of the KIEE Conference
• /
• 1999.07e
• /
• pp.2143-2145
• /
• 1999

Measurements of wind noise, generated by High-voltage overhead transmission lines placed in a uniform flow are carried out in the Anechoic windtunnel. High-voltage overhead transmission lines generates audible wind noise, which cause a serious environment problem. Accordingly, wind noise has become one of major concerns for design engineers and operations personnel. In the present research, tests were mainly performed with various configuration of transmission line with spiral wires. Remarkable noise reduction was observed for some of the spiral transmission lines, compared with the noise generated without the spiral wire.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.4
• /
• pp.336-342
• /
• 2012

Large-scale active solar heat systems are generally using heat exchanger between collector and storage tank loops to prevent damage by freezing. It is difficult to maintain stratification in a storage tank in the system owing to greater flow rate enhancing heat transfer. In the previous study, we introduced a spiral-jacketed storage tank and obtained good results to keep system performance of general level without better stratification. We added a scroll-shaped heat exchanger coil on the upper part in the spiral-jacketed storage tank. As a result of the experiment, it was verified that degree of stratification of the new type storage tank is higher than that of the previous one with a possibility of better collector efficiency and solar fraction.

• Proceedings of the SAREK Conference
• /
• 2004.06a
• /
• pp.170-170
• /
• 2004

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.3
• /
• pp.239-247
• /
• 2009

Sewage pumps are designed with a wide flow channel by, for example, sacrificing some efficiency and reducing the number of blades, in order to prevent plugging with foreign bodies. However, the behavior of foreign bodies which actually flow into a pump is extremely complex, and there are questions about whether the presumed foreign bodies will actually pass through. This paper proposes a new type of sewage pump impeller designed to further improve pump efficiency and performance in passing foreign bodies. This sewage pump impeller has a structure in which the suction flow channel of a closed type non-clog pump is wound in a helical spiral. The focus of this research was to investigate pump performance and internal flow in this single blade sewage pump impeller. The results clearly indicated the following facts: The developed sewage pump impeller exhibits high efficiency over a wide range of flow rates; internal flow of the pump is very complicated; and the internal flow state varies greatly when the flow rate changes.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.583-589
• /
• 2004

One of noticeable features in the cross flow fan is that a working fluid passes through impeller blade twice without distinction between the inlet and exit angles. Also, it does produce higher circumferential velocity than other types of blade at the same flow rate in accordance with the application of the forward curved shape. However, a design theory for the cross-flow fan has not yet been formed owing to an eccentric vortex, which is the remarkable characteristics, occurred in a cross-flow fan. Furthermore, the eccentric vortex, which is difficult to control of the size and position, is the important cause of performance decrease. In this study, experiments are carried out to estimate the similarity of the cross-flow fan with various scales and rotational velocity changes. Pressure coefficients to flow coefficients with various scales of the cross-flow fan are plotted to research the application of the general similarity law of the turbomachinery in the cross-flow fan with Archimedes spital, which is the important factor haying an effect on it.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.3
• /
• pp.269-278
• /
• 2011

We investigate the heat-transfer and pressure-drop characteristics of fin-and-tube heat exchangers with a copper plate or copper spiral fins. Twenty-four samples with different fin pitches and tube rows were tested. For both configurations, the effect of the fin pitch on the j factor is negligible, and the f factor increases with the fin pitch. The effect of the tube row depends on the configuration. For plate fin-and-tube heat exchangers, the j factor decreases as the row number increases; the reverse is true for spiral exchangers. We explain this by considering the flow pattern. The j factor for plate fin-and-tube heat exchangers is larger than that for spiral exchangers, and the difference decreases as the row number increases. The f factor of the plate fin-and-tube heat exchanger is also larger. We compare our results with existing predictions of correlations.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.16 no.1
• /
• pp.118-123
• /
• 2017

It is well known that water jetting is now widely used in the advanced cutting processes of polymers, metals, glass, ceramics, and composite materials because of some advantages, such as heatless and non-contacting cutting different from the laser beam machining. In this paper, we proposed the simulation model of waterjet by lengths and the inner spiral structure of the nozzle. The simulation results show that the outlet velocity of the nozzle is faster than the inlet. Furthermore, we found rapid velocity reduction after passing through the outlet. The nozzle of diameter ${\phi}500$ and length 70mm, shows the optimal fluid width and velocity distribution. Also, the nozzle with inner spiral structure shows a Gaussian distribution of velocity and this model is almost twice as fast as the model without spiral structure, within the effective standoff distance (2.5 mm). In the future, when inserting abrasive material into the waterjet, we plan to analyze the fluid flow and the particle behavior through a simulation model.