• Korean Chemical Engineering Research
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• v.62 no.2
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• pp.191-199
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• 2024

A study was conducted on a tubular heat exchanger to improve its heat transfer rate by using a novel baffle plate design with discontinuous swirling patterns. The design consisted of perforated baffle plates with rectangular air deflectors positioned at varying angles. The tubes in the heat exchanger were arranged in a consistent alignment with the airflow direction and exposed to a uniform heat flux on their surfaces. Each baffle plate included sixteen deflectors inclined at the same angle and arranged in a clockwise pattern. This arrangement induced a swirling motion of the air inside a circular duct where the heated tubes were located, leading to increased turbulence and improved heat transfer on the tube surfaces. The spacing between the baffle plates was adjusted at different pitch ratios, and the Reynolds number was controlled within a range of 16,000 to 29,000. The effects of pitch ratios and inclination angles on the heat exchanger's performance were analyzed. The results indicated that using a baffle plate with rectangular deflectors inclined at 30° and a pitch ratio of 1.2 resulted in an average increase of 1.29 in the thermal enhancement factor.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1618-1620
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• 1997

A GaAs schottky diode with taper field plate is proposed to increase breakdown voltage. Breakdown voltage is calculated by device simulator MEDICI. The GaAs schottky diode with taper gate which has $5.7^{\circ}$ taper angle have shown 45% increase in the breakdown voltage compared with conventional field plate GaAs schottky diode.

• Journal of Korean Neurosurgical Society
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• v.48 no.4
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• pp.342-346
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• 2010

Objective : This study assessed the efficacy of anterior cervical discectomy and fusion (ACDF) with cage alone compared with ACDF with plate instrumentation for radiologic and clinical outcomes in two-level cervical degenerative disease. Methods : Patients with cervical degenerative disc disease from September 2004 to December 2009 were assessed retrospectively. A total of 42 patients received all ACDF at two-level cervical lesion. Twenty-two patients who underwent ACDF with cage alone were compared with 20 patients who underwent ACDF with plate fixation in consideration of radiologic and clinical outcomes. Clinical outcomes were assessed using Robinson's criteria and posterior neck pain, arm pain described by a 10 point-visual analog scale. Fusion rate, subsidence, kyphotic angle, instrument failure and the degenerative changes in adjacent segments were examined during each follow-up examination. Results : VAS was checked during each follow-up and Robinson's criteria were compared in both groups. Both groups showed no significant difference. Fusion rates were 90.9% (20/22) in ACDF with the cage alone group, 95% (19/20) in ACDF with the plate fixation group (p = 0.966). Subsidence rates of ACDF with cage alone were 31.81% (7/22) and ACDF with plate fixation were 30% (6/20) (p = 0.928). Local and regional kyphotic angle difference showed no significant difference. At the final follow-up, adjacent level disease developed in 4.54% (1/22) of ACDF with cage alone and 10% (2/20) of ACDF with plate fixation (p= 0.654). Conclusion : In two-level ACDF, ACDF with cage alone would be comparable with ACDF with plate fixation with regard to clinical outcome and radiologic result with no significant difference. We suggest that the routine use of plate and screw in 2-level surgery may not be beneficial.

• Wind and Structures
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• v.13 no.2
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• pp.127-144
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• 2010

Pressure measurements on static and autorotating flat plates have been recently reported by Lin et al. (2006), Holmes, et al. (2006), and Richards, et al. (2008), amongst others. In general, the variation of the normal force with respect to the angle of attack appears to stall in the mid attack angle range with a large scale separation in the wake. To date however, no surface pressures have been measured on auto-rotating plates that are typical of a certain class of debris. This paper presents the results of an experiment to measure the aerodynamic forces on a flat plate held stationary at different angles to the flow and allowing the plate to auto-rotate. The forces were determined through the measurement of differential pressures on either side of the plate with internally mounted pressure transducers and data logging systems. Results are presented for surface pressure distributions and overall integrated forces and moments on the plates in coefficient form. Computed static force coefficients show the stall effect at the mid range angle of attack and some variation for different Reynolds numbers. Normal forces determined from autorotational experiments are higher than the static values at most pitch angles over a cycle. The resulting moment coefficient does not compare well with current analytical formulations which suggest the existence of a flow mechanism that cannot be completely described through static tests.

• Journal of the Optical Society of Korea
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• v.9 no.1
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• pp.32-35
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• 2005

In light microscopy, spatial resolution is limited by diffraction effect. Confocal microscopy has improved resolutions in both lateral and axial directions, but these are still limited by diffraction effect. Confocal self-interference microscopy (CSIM) uses interference between two perpendicularly polarized beams to enhance lateral resolution. In previous research, we proposed a calcite plate with its optic-axis perpendicular to the propagation angle and one of the boundary surfaces of the plate. This type of plate is not widely used to our knowledge. In this paper, we change the calcite plate to more common one, which is commercially available. This calcite plate has its optic axis in the plane of incidence. We analyze the characteristics of this calcite plate and numerically compare the performances of CSIM in previous research and CSIM with the commercial calcite plate. Numerical results show improved performance when using the commercial calcite plate

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.11
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• pp.965-973
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• 2010

Numerical analysis has been carried out to investigate the heat transfer characteristics of a plate heat exchanger. The multi-cell models with inlet part and outlet part are used for performing numerical simulation. The plate heat exchanger is characterized by chevron angle of $15^{\circ}$, corrugation pitch of 24mm and corrugation height 6~12mm. The length of the inlet-part considered in the analysis ranges from 24.8 to 124mm and Reynolds numbers range from 1,000 to 10,000. The correlations such as friction factor and Colburn factor are compared with previous experimental data. The results can be utilized for designing the plate heat exchanger.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.3
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• pp.21-28
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• 1989

The optimun laminated composition of the stiffened composite plates is studied from the view point of buckling strength. The finite element method is applied to the buckling analysis of the composite plates taking into account the effect of shear deformation through the plate thickness. The stiffened plate model is discretized using plate thickness and symmetrically stacked. Parametric study is carried out for the selection of the optimum laminate structure; optimum fiber angle sequence through the thickness. Laminate structure of $[-45^{\circ}/45^{\circ}/90^{\circ}/0^{\circ}]$, is found to give the best buckling strength. For the case of that layer number is more than eight, best result is obtained when layers of the same fiber angle are put together, leaving the laminate has the same fiber angle sequence as a whole.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.12
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• pp.1335-1340
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• 2013

Herein the water film was introduced to the hydrophilic area on the line patterned surface to solve the contradiction caused by surface roughness (high different wettability has advantage to control the droplet but high roughness for that high wettability difference causes obstruction of droplet moving). Thus the droplet on the water film could not be hindered to line direction but restricted to orthogonal direction, effectively. In addition, droplet behaviors according to droplet volume and line thickness were studied. Droplet fell off the line with narrowing the interface between the droplet and the water film on the line. When the droplet fell off the line, the plate angle was designated as a critical plate angle and it used as an indicator of surface capability to control the droplet. As a result critical plate angle increases as droplet volume decreases and line thickness increases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.199-205
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• 2002

In this paper, the optimum shape and arrangement of ribs in the channel of a plate heat exchanger are studied. The following dimensionless geometric parameters of ribs are selected as design variables: rib height ($H_R$), angle of attack ($\beta$), rib pitch ($P_R$), rib distance (L) and aspect ratio of rib (AR). The optimization is performed by minimizing the objective function consisting of the Nusselt number and the friction factor. The optimal values of design variables are as follows: $H_R$=0.263, $\beta$=0.290, $P_R$=3.142, L: 3.954, AR=0.342. The pressure drop and the heat transfer of the optimum model, compared to those of the reference model, are increased by 15.1% and 41.6%, respectively.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1512-1517
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• 2003

Augmentation of CHF by ultrasonic is experimentally studied under subcooling pool boiling condition. Experiment is carried out for downward-facing plate with and without the ultrasonic. The working fluid is distilled water. Experimental apparatus is composed of a bath, power supply, test section, ultrasonic generator, DAQ system. Experiment is performed with the subcooling temperature of $5^{\circ}C$, $20^{\circ}C$, $40^{\circ}C$ and the inclined angle of $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $45^{\circ}$, 90. From the experimental results, it is found that ultrasonic effect enhances CHF of the downward-facing plate. As increasing the degree of subcooling, the rate of CHF increase is enhanced. As increasing the inclined angle, the rate of CHF increase decreases. Also, we can see that the heat transfer mechanism of CHF augmentation is closely connected with the dynamic behavior of bubble generation and departure.