• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.157-164
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• 2016

The performance of convective heat transfer in rod bundle flow was experimentally evaluated using a twist-vane spacer grid. A $4{\times}4$ square-arrayed rod bundle was prepared as the test section, with a pitch-to-diameter ratio(P/D) of ~1.35. To check the convective heat transfer performance, the circumferential and longitudinal variations in rod-wall temperatures were measured downstream of the twist-vane spacer grid. In the circumferential measurements, the rod-wall temperature toward the twist-vane tip showed the lowest value, which might be due to the deflected water flow caused by the twist-vane. On the other hand, the wall temperature of the longitudinal measurements near the twist-vane spacer grid decreased dramatically, which implies that the convective heat transfer performance was enhanced. A heat transfer enhancement of ~35 % was achieved near downstream of the twist-vane spacer grid, as compared with the upstream value. Based on the present experimental data, a correlation for predicting the heat transfer performance of a twist-vane spacer grid was proposed.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.3
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• pp.240-245
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• 2004

Torsional characteristics of nonuniform circular waveguides were studied experimentally by using an in-plane laser vibrometer. The circumferential displacement along the axis of a rod was measured as a response of the torsional oscillation excited at one end of the rod. The experimental results obtained for a stepped circular rod and a conically-tapered rod were compared with theoretical predictions. The results of this paper show the possibility of using the in-plane laser vibrometer for the measurement of torsional vibrations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.53-62
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• 2017

The forced convection heat transfer performance of a twist-vane spacer grid for a dual-cooled annular fuel assembly was examined experimentally. The twist-vane spacer grid was uniquely designed to enhance mixing inside subchannels and mixing between adjacent subchannels. For testing, a $4{\times}4$ square-arrayed rod bundle with narrow gaps between rods was prepared as the dual-cooled annular fuel assembly to be simulated. The pitch-to-rod diameter ratio of simulated dual-cooled annular fuel assembly was 1.08. The experiments were performed under the following conditions: axial bulk velocity, 1.5 m/s and heat flux, $26kW/m^2$. With regard to the circumferential temperature distribution, the lowest rod-wall temperatures upstream and downstream were measured at the subchannel center and the position toward the tip of twist-vane, respectively. With regard to the axial temperature distribution, behind the twist-vane spacer grid, the rod-wall temperature decreased drastically, and the Nusselt number was enhanced by up to 56 %. The present measured data indicate that the twist-vane spacer grid can effectively improve the forced convection heat transfer in the dual-cooled annular fuel assembly with narrow gaps.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.434-438
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• 2001

Piezoelectric torsional transducers have been fabricated to generate torsional waves in a rod. The principle of generating torsional wane is based on the use of the circumferential shear motion derived by axial voltage exerted on the piezoelectric disk poled in the circumferential direction. The natural frequency or the piezoelctric torsional dish has been reduced by fabricating Langevin-type torsional transducers. The natural frequecies of the fabricated transducers have been measured and have shown good agreement with the characteristics predicted by analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.609-616
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• 2001

The vibrational characteristics of nonuniform circular rods have been studied theoretically and experimentally in this paper. The differential equation of torsional motion expressed in terms of the angular displacement has been solved exactly and approximately for a stepped circular rod and for a conically-tapered rod. Solutions of the boundary-value problem have yielded the natural frequencies, mode shapes and forced responses of the rods. The theoretical solutions of forced response have been verified by comparing them with experimental ones.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.3
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• pp.411-419
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• 2017

Stress concentration is one of the causes of the damage due to the large stress than the mean stress acting on the bar. This paper presents the results for stress of a stepped bar with a hole under torsional loading. The analysis for stress concentration and shearing stress was done by ANSYS Workbench which is a commercial finite element analysis software. The analysis results on fillet and hole are increased as the distance between them are become close. In addition, the distribution of the maximum equivalent stress developed in the fillet and hole in the outside range of the specific distance L (-100 mm ~ 300 mm) was almost constant in the models used in the analysis. On the other hand, the distribution of the maximum equivalent stress developed in the fillet and hole in the inside range of the specific distance L (-100 mm ~ 300 mm) was rapidly increasing and decreasing the change in the models used in the analysis. In addition, it was also possible to identify the location where the differences between equivalent stresses of hole and fillet occurred within a specific distance L (-100 mm ~ 300 mm). The analysis results of paper can used when selecting a hole location in a stepped bar under torsional loading.

• Journal of KSNVE
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• v.10 no.1
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• pp.168-173
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• 2000

This paper deals with the theoretical study on the effect of the viscosity of an adjacent viscous fluid on the characteristics of the torsional vibration of a rod with fixed-free boundary conditions. Expressions for the natural frequency and damping factor have been obtained as functions of the viscosity of the fluid by exact and asymptotic analyses. The results provide quantitative information of the natural frequency reduction and damping rate affected by the fluid viscosity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.353-354
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• 2009

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1016-1025
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• 2002

This paper deals with the measurement of the fluid viscosity by using the torsional vibration of a circular rod excited by a torsional vibrator at one end. The effect of an adjacent viscous fluid on the torsional vibration of the rod has been studied theoretically and expressed in terms of the mechanical impedance. The theoretically-obtained trend that the mechanical impedance is proportional to the square root of the viscosity times the density of the fluid has been confirmed by the impedance measurement. The paper demonstrates that a torsionally-vibrating rod can be used as a sensor to measure the viscosity of a fluid.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.153-159
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• 2002

This paper deals with the measurement of the fluid viscosity by using the torsional vibration of a circular red excited by a torsional vibrator at one end. The effect of an adjacent viscous fluid on the torsional vibration of the rod has been studied theoretically and expressed in terms of the mechanical impedance. The theoretically-obtained trend that the mechanical impedance is proportional to the square root of the viscosity times the density of the fluid has been confirmed by the impedance measurement. The paper demonstrates that a torsionally-vibrating rod can be used as a sensor to measure the viscosity of a fluid.