• Journal of Korean Society of Disaster and Security
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• v.14 no.1
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• pp.1-8
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• 2021

A corrugated pipe is widely used in firefighting equipment and sprinkler pipes because of its elasticity, which is less damaged by deformation and convenient facilities. However, the corrugated shape of the wall results in complex internal turbulent flow, and it is difficult to predict the pressure drop, which is an important design factor for pipe flow. The pressure drop in the corrugated tube is a function of the shape factors of the pipe wall, such as groove height, length, and pitch. Existing studies have only shown a study of pressure drop due to length changes in the case of D-shaped tubes with less than 5 pitch (P) and height (K) of the rectangular grooves in the tube. In this work, we conduct a numerical study of pressure drop for P/Ks with length and height changes of 2.8, 3.5 and 4.67 with Re Numbers of 55,000, 70,000 and 85,000. The pressure drop in the corrugated tube was interpreted to decrease with smaller P/K. We show that the pressure drop is affected by the change in the groove aspect ratio, and the increase in the height of the groove increases the recirculation area, and the larger the Reynolds number, the greater the pressure drop.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.37-45
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• 2017

Extinguishment of a burning solid propellant is difficult, however, dynamic extinction can be induced by fast depressurization in combustion chamber. This paper describes experimental results for the characteristics of extinguishment for composite solid propellants by rapid depressurization. For various composition of solid propellants, depressurization ratio which can induce extinguishment of combustion was obtained using experimental apparatus with rupture disk. Experimental results showed that particle size of oxidizer, mixing ratio of oxidizers with different particle size and contents of metal fuel can affect on the characteristics extinguishement for solid propellant.

• Clean Technology
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• v.24 no.4
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• pp.301-306
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• 2018

Recently, due to the increase in the fine dust, regulations on PM generated from diesel cars are strengthened. There is a growing interest in diesel particulate filters (DPFs), a post-treatment device that removes exhaust gases from diesel vehicles. Therefore, one of the enhancements of the DPF efficiency is to reduce the pressure drop in the DPF, thereby increasing the efficiency of the filter and regeneration. In this study, the effect of cell density, channel shape, wall thickness, and inlet channel ratio of 5.66" SiC and Cordierite DPF on the pressure drop in DPF was investigated using ANSYS FLUENT simulator. As a result of the experiment, the pressure drop was smaller at 300 CPSI than 200 CPSI, and the anisotropy and O / S cell showed less than Isotropy by pressure drop of about 1,000 Pa. As the porosity increased by 10% the pressure drop was reduced by about 300 Pa and as the wall thickness increased by 0.05 mm, the pressure drop was increased by about 500 Pa.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.8
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• pp.759-765
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• 2013

This study proposes the characteristics of the pressure drop in a compressible fluid through porous media for application to a porous injector in a liquid rocket engine in order to improve the uniformity of the drop size distribution and the mixing performance of shear coaxial injectors. The fluid through the porous media is a Non-Darcy flow that shows a Nonlinear relation between the pressure drop and the velocity at high speed and high mass flow rate. The pressure drop of the Non-Darcy flow can be derived using the Forchheimer equation that includes the losses of viscous and inertia resistance. The permeability and Ergun coefficient represented as a function of the pressure drop and pore size can be applied to the porous injector, where the fluid through the porous media is compressible. A generalized correlation between the pressure drop in relation to the pore size was derived.

• Nuclear Engineering and Technology
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• v.21 no.2
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• pp.123-133
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• 1989

The pressure drops through contractions in horizontal single and two-phase flow were investigated. A total of 167 measurements were made for four different entrance shapes to study the effects of the entrance shape on the pressure drop through a contraction in horizontal single and two-phase flow. From this data, pressure drops were calculated and compared with the pressure drops predicted by analytical models for single and two-phase flow. For single phase How the agreement between the data and predictions is within $\pm$25%, whereas for two-phase flow Hoopes model, which gives a better agreement than the homogeneous model, underpredicts the data as much as 45% In addition, the effects of void fraction and liquid phase mass velocity on the pressure drop through the sudden How channel contraction were investigated for two-phase flow.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.120-127
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• 2013

This study investigated the characteristics of heat transfer and pressure drop for cross-flow heat exchanger of premixed combustion system. The premixed burner was in front of a heat exchanger, and the number of heat exchanger modules was changed to investigate the characteristics of NOx and CO emissions with various equivalence ratios. In addition, the effectiveness, entropy generation and pressure drop were calculated by various number of heat exchanger modules and the performance of heat exchanger was analyzed by the exergy loss.

• Journal of Energy Engineering
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• v.14 no.4 s.44
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• pp.241-247
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• 2005

Heat transfer enhancement and pressure loss penalty caused by three-row winglets built in three-row tube-bundles in an in-line arrangement, are compared between 'common flow up' and 'common flow down' winglet configurations. The 'common flow down' winglet-pairs recommended by the previous researchers bring about $10\%$ to $25\%$ increase in heat transfer enhancement and $20\%$ to $35\%$ increase in pressure loss penalty, in comparison with fin-tube bundles without winglets. For the 'common flow up' winglet-pairs, the spanwise distance between the trailing edges (${\Delta}y$) of winglet pairs was changed and investigated. Two types ot winglet are applied for triangular and rectangular shapes. In the triangular winglets with ${\Delta}y$=5 mm in in-line tube bundles, the heat transfer increased up to $10\%$, and simultaneously the pressure loss decreased by $8\%$ to $15\%$ for the Reynolds number (based on two times channel height) ranging from 300 to 2700, when the 'common flow up' winglets were built in. The performance of fin-tube bundles with triangular winglets is much superior to the rectangular one, because of the smaller pressure-loss penalty.

• Journal of Energy Engineering
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• v.16 no.3
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• pp.149-154
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• 2007

An experimental study on the air-side pressure drop of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side pressure drop in the literature is not based on a consistent approach. This paper focuses on method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry and wet surface pressure drop estimation in fin-tube heat exchanger. A comparison was made between the predictions of previously proposed empirical correlations and experimental data for the air-side pressure drop on design conditions of condenser and evaporator. Results are pre-sented as plots of friction f-factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of $150{\sim}250\;kg/m^2s$ with air flows at velocity ranges from 0.38 m/s to 1.6 m/s.

• Fire Science and Engineering
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• v.30 no.1
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• pp.1-5
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• 2016

Cases of cardiac arrests due to cardiovascular ailments have increased recently., portable Current portable resuscitators which can be automatically supply oxygen operated by the pressure of supplied oxygen without manual or electronic actuators are now widely used in emergency worldwide. However, reductions in Pressure drop characteristics through the extended use of this type of resuscitator, however, is are not well-known described. This paper describes the reduction in pressure loss drop performance of the various holes in within the flow control disc of with various hole size of the portable resuscitators using on breathing resistance through the CFD simulation, and suggests the an optimum optimal design of the hole shapes for the minimization of alteration in order to minimize this pressure drops.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.316-323
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• 2013

The use of artificial roughness in various forms of shapes and sizes is the most common and effective way to improve the performance of a flat-plate solar collector. In the present study, numerical analysis on heat transfer and pressure drop was performed in a rectangular channel with various rib arrays. The uniform heat flux is applied to the channel from the upper side. The forms of ribs considered in this study were rib $90^{\circ}$, groove $90^{\circ}$, groove $60^{\circ}$, baffle $90^{\circ}$, baffle $60^{\circ}$, wave $90^{\circ}$ and wave $60^{\circ}$. Air is the working fluid, and the Reynolds number ranges from 3200 to 17800. Nusselt number and friction factor were investigated to predict the performance of the system with various type of ribs. The average Nusselt number and pressure drop were increased with the increase of velocity in all types of ribs. The highest heat transfer and pressure drop occurred for the baffle $90^{\circ}$, but highest performance factor considering heat transfer and pressure drop together occurred for the groove $60^{\circ}$. Therefore, heat transfer and pressure drop should be considered together when a flat plate solar collector is designed.