• Fire Science and Engineering
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• v.32 no.2
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• pp.17-23
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• 2018

In this study, the relations of the wall thermal conductivity and surface temperature in a compartment fire are investigated using Buckingham Pi theorem. The dimensionless parameters of the previous study are analyzed in order to correlate the dimensionless groups of the heat release rate, the thermal conductivity, the volume of compartment and the convective heat transfer coefficient. In addition the reduced scale of compartment, which has 1/6 size of ISO 9705 Room Corner Tester, is manufactured and the oxygen concentration and the maximum temperature in the space are measured for the gasoline pool fire ($10cm{\times}10cm$, $15cm{\times}15cm$ and $20cm{\times}20cm$). Finally, the criterion of the wall temperature increase are suggested in accordance with the thermal conductivity and the convective heat transfer coefficient. In addition, the dimensionless empirical equation using Buckingham Pi theorem considering the heat release rate are presented suggested. The results of this study will be useful especially for the fire phenomenon investigation of the wall thermal conductivity coefficient and shape in the compartment space.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.827-837
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• 2005

In this study, we derived a new non-dimensional variable including bubble size and air diffusing area by Buckingham's theorem for making a practical correlation with experimental results. Firstly, we drew a relationship between a non-dimensional variable, $NH/u_s$, which has a form of Froude number and destratification efficiency with a simple theoretical consideration. Then we derived two non-dimensional variables by Buckingham's ${\pi}$-theorem and equating them with a form of $Fr_N$ for making single parameter to correlate overall destratification efficiency. As the result, the single parameter Be number shows a correlations with destratification efficiencies obtained from laboratory and pilot experiments. Also, for the practical applications, we conducted multiple regression analysis using Be and tank area to make predictive equations about destratification efficiency. The result also shows a successful correlations with destratification efficiency ($R^2$>0.9, p<0.001). Using this equation, we proposed a new design methodology with respect to bubble diffusing area.

• Journal of the Korean Society for Marine Environment & Energy
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• v.2 no.1
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• pp.34-39
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• 1999

Removal of spilled oil over the sea and the river has become one of the urgent problems in these days. Removing oil using mechanical devices by adhesion method is known to be closely related with the problem of estimating the thickness of film remaining on the surface of solid withdrawn from a quiescent liquid. In the present study a series of experimental results are compared with the analytic estimation for the thickness of film remaining on the solid surface using non-dimensional analysis. For the case of pure water both results show the remarkable agreement. However, discrepancy has been found for the case of Bunker C oil and diesel oil. The analytic estimation over-predicts the experimental value for the case of Bunker C oil and under-predicts it for the case of diesel oil. Further study is required to investigate the real situation including a contact angle and the property difference between oil and water.

• Smart Structures and Systems
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• v.6 no.1
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• pp.57-72
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• 2010

This paper presents the most significant results obtained within a broad-ranging experimental program aiming to evaluate both the effectiveness and the robustness of a Base Isolation (BIS) and a Tuned Mass Damper (TMD) combined control strategy (BI & TMD). Following a brief description of the experimental model set-up and the adopted kinematic scaling technique, this paper describes the identification procedures carried out to characterize the system''s model. The dynamic response of a small-scale model to recorded earthquake excitations, which has been scaled by using the Buckingham pi-theorem, are later presented and discussed. Finally, the effectiveness and robustness of the combined control strategy is evaluated by comparing the model's dynamic response. In particular, reduction in relative displacements and absolute accelerations due to the application of different mass damping systems is investigated.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.4
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• pp.192-197
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• 2004

A capillary tube, which is a common expansion device in small sized refrig-eration and air-conditioning systems, should be redesigned properly to establish an optimum operation cycle of a refrigerating system with alternative refrigerants. Based on experimental data for R-22, R-290, and R-407C, an empirical correlation is developed to predict mass flow rate through capillary tubes. Dimensionless parameters are derived from the Buckingham Pi theorem, considering the effects of operating conditions and capillary tube geometry on mass flow rate. Approximately $97\%$ of the present data are correlated within a relative deviation of $\pm\;10\%.$ The present correlation also predicts the data obtained from open literature within $\pm\;15\%.$ In addition, rating charts of refrigerant flow rate for R-12, R-22, R-134a, R-152a, R-407C, R-410A, R-290, and R-600a are developed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.4
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• pp.251-258
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• 2011

The objective of this study is to propose two empirical correlations to predict the mass flow rate through an automotive block type thermostatic expansion valve and then to evaluate the correlations. The first correlation is deduced by modifying the basic equation of the orifice meter for the mass flow rate and the second correlation is deduced by using the Buckingham's ${\pi}$ theorem. The first correlation showed very good agreement on the measured data for R134a, given by Monforte. Average relative deviation and standard deviation of it are 2.5% and 1.6%, respectively. The second correlation agreed on the same measured data with a little greater deviations. The two correlations may apply to common expansion valves which have different geometrical sizes of the same shape.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.1
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• pp.33-44
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• 1982

In Order to study for the aeration characteristics which is one of the most important unit processes for the activated sludge process, a pitched blade type aeration model of octagonal shape with a draft tube in it was made as a pilot plant. Oxygen transfer rates, power consumptions and fluid velocities and behaviers were measured and evaluated with the various turbine shapes. And with these results, the dimensionless model analysis using the Buckingham ${\pi}$ theorem was discussed for a proper turbine shape determination.

• International Journal of Railway
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• v.4 no.2
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• pp.42-49
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• 2011

Today, rolling stock has become a fast and convenient mode of transportation and has witnessed increased demand. But the speed improvement has resulted in increased aerodynamic noise and therefore residential districts near the railroad tracks are exposed to ever increasing noise level. A study on methodologies for measuring and appraising rolling stock's environmental noise has therefore become an important area of endeavor. In the case of the environmental noise, there are no changes in tone so prediction can be made by reducing areas around the railway. The present study explores estimation of the noise around the railway using scale model, and the source of the noise has been investigated as well. The scale model of rolling stock will have to be able to measure high frequency noise and it is required to be generated in a short amount of time. Since popping a balloon or firing a gun fits this requirement the present study analyzed the characteristics of these two different noise sources. Measurement was made in a large vacant lot and the reflection due to the ground was also examined. The method proposed here can be used in the future for predicting the environmental noise of railway vehicles.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1106-1112
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• 2005

An experimental investigation was performed to develop an empirical correlation of R-410A flowing through short tube orifices working near the critical region. Tests were executed by varying upstream pressure from 2,619 kPa to 4,551 kPa, and upstream subcooling from 2.8 and $11.1^{\circ}C$. The experimental data were represented as a function of major operating parameters and short tube diameter. As compared to mass flow trends at normal upstream pressures, flow dependency on upstream subcooling became more significant at high upstream pressures due to a higher density change. Based on the database obtained from this study and literature, an empirical correlation was developed from a power law form of dimensionless parameters generated by the Buckingham Pi theorem. The correlation yielded good agreement with the data. Approximately $92\%$ of the data were correlated within a relative deviation of $5\%$.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.50-58
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• 2000

Burning rate of the matrix propellant($r_{sb}$) and burning rate along the metal wire($r_w$) were measured and analyzed for the HTPB/AP/Al propellant embedded with Ag wire($\phi$0.15mm) according to weight % of RDX(0~20%). Variation of burning rate increment ratio($r_w$/$r_{sb}$) and pressure exponent(n) was studied for the nitramine propellant having 10% RDX embedded with three kinds of metal(Ag, Cu, and Ni-Cr) of which diameter range is between 0.1~0.6mm. Maximum burning rate increment ratio of the nitramine propellant embedded with Ag wire($\phi$0.1mm) was 5.94 at $20^{\cire}C$, 1000 psia, 16.4% faster than that of HTPB/AP propellant, it is because that autoignition temperature of the nitramine propellant was higher than that of HTPB/AP propellant. Standard deviation of absolute ($r_{wc}$/$r_{we}$)/$r_{we}$ calculated by using new empiracal equation composed of four dimensionless groups, is 6.11% less than that calculated by using original empirical equation composed of three dimensionless group. The new empiracal equation is derived from Buckingham pi theorem using the parameters such as thermal diffusivity, melting temperature. wire diameter, propellant sample diameter, frame temperature, autoignition temperature and matrix burning rate which influence on $r_w$.