Analysis Of Pressure Drop Research Articles

Heat Transfer and Pressure Drop in Wavy-Walled Tubes: A Parameter-BASED CFD Study

Co-relations of friction factor and Nusselt number for plain tubes have been widely developed, but less analysis has been done for tubes with wavy surfaces. This paper uses the Computational Fluid Dynamics (CFD) tool for the analysis of heat transfer and pressure drop in wavy-walled tubes, which can be utilized as a heating element for fluids. An investigation was done for the effect of Reynolds number (Re) and wavy-walled tube geometry on friction factor and Nusselt number of laminar and turbulent flow inside wavy-walled tubes. The numerical results and experimental comparison indicate that heat transfer and pressure drop for water are significantly affected by wavy-walled tube parameters and flow Reynolds number. These wavy-walled tubes are capable of increasing the heat transfer to or from a fluid by an order of magnitude but at an expense of higher pumping power. This ratio was found to remain at the minimum at a wave factor of 0.83 for 34 < Re < 3500 and maximum at a wave factor of 0.15 for 200 < Re < 17,000. New correlations of friction factor and Nusselt number based on wavy-walled tube parameters are proposed in this paper, which can serve as design equations for predicting the friction factor and heat transfer in wavy-walled tubes under a laminar and turbulent regime with less than 10% error. The quantitative simulation results match the experimental results with less than 15% error. The qualitative comparison with the experiments indicates that the simulations are well capable of accurately predicting the circulation zones within the bulgy part of the tubes.

Analysis of Flow Boiling Frictional Pressure Drop in Plate Heat Exchangers

Abstract Plate heat exchangers are widely used in various industries for many years. The corrugated channels on the plates effectively enhance the turbulence of flow boiling and complicate the prediction of pressure drop. This article presents a brief review about effects of various operating and geometrical factors on frictional pressure drop during flow boiling in plate heat exchangers. Experimental data points of frictional pressure drop were collected from the previous literature to develop a general correlation. The database contained 591 data points, covering six different refrigerants, mass flux range 5.5–130 kg/m2/s1, heat flux 0–15 kW/m2, vapor quality 0.04–0.96, saturation temperature −25 to 61 C°, chevron angle 20 deg–65 deg, and hydraulic diameter 1.7–5.35 mm. In this study, several existing correlations were compared with the database, and most of them seem fail to give an acceptable prediction. A new correlation was proposed with multiple regression analysis in terms of two-phase Fanning friction factor. The new method showed a good agreement with the present database and predicted 70.2% and 91.7% of data points within ±30% and ±50% errors, respectively.

Three Dimensional Analysis Method and Application of Pressure Drop after Coal Seam Pressure

The analysis of pressure drop after compression is very important for obtaining coalbed gas reservoir parameters and optimizing coalbed gas fracturing design. However, there are some problems such as closed pressure analysis, inaccurate calculation of fracture geometry and effective permeability. In this paper, a three-dimensional analysis model of post-pressure pressure drop is established based on the principle of fluid volume balance during injection and closure. Based on the quasi-three-dimensional fracture model, the geometric size, fitting pressure and filtration coefficient of fracturing fluid are explained, and the practicability and accuracy of this method in the analysis of pressure drop after coal seam pressure are verified by field construction examples.

Pressure drop analysis and aerodynamic design of compressor L-inlet duct

Pressure drop inside the compressor L-inlet duct (CLID) has a great impact on the intake loss, which directly affects the operating cost of the power plant. Generally, every 500 Pa inlet pressure drop is equivalent to 0.5% intake loss at standard conditions, which can contribute to higher than 1% of gas turbine power loss in terms of fuel flow. Hence, the pressure drop should be kept as low as possible. Pressure drop that occurs within the CLID mainly depends on the structural parameters, however, no general design guidelines were found in open literature. Moreover, a reasonable intake duct aerodynamic design is the fundamental solution to the problem of compressor inlet distortion. Therefore, in this paper, the fluid dynamics of CLID are revealed by using both the experimental and numerical methods. Then, the effects of typical parameters on the pressure drop and total pressure loss coefficient are investigated. Furthermore, the conceptual design of CLID is proposed on the basis of distortion flow analysis and 1D intake volute design. The results show that larger CLID width (a/D4) and depth (b/D4) result in larger flow separation at the contraction, thereby leading to smaller total pressure drop and total pressure loss coefficient. However, the opposite change occurs at the cone diameter (D0/D4). Besides, the conceptual design of CLID is proposed by indirectly establishing the relationship between the outlet flow angle and inlet structural parameters.

On a possible mechanism for the water build-up formation in mine ventilation shafts

A one-dimensional mathematical model of water droplet accumulation in ventilation shafts is proposed. Model parameters are determined using the results of a ventilation survey of deep hard rock mines of Norilsk Nickel Company. The formation of drip water in the shaft is simulated not only due to excess moisture condensation, but also due to groundwater inflows through fissures in the shaft lining. A formula is obtained for calculating the pressure drop due to the water build-up. The pressure drop analysis showed that the water build-up has a significant impact on the fan operation only if there are additional groundwater inflows.

Computational modelling of plate-fin and tube heat exchanger for heat transfer and pressure drop analysis

The plate-fin and tube heat exchanger are a cross-flow type heat exchanger, which uses plates as fins as indicated...

Pressure drop analysis for the droplet break-up flow in a locally constrictive microchannel

Locally constrictive microchannels are effective components to implement droplet break-up in microfluidic processes. We herein report an experimental study of droplet break-up flow based on pressure drop analysis. The time varying pressure drops were recorded by a self-assembled experimental platform with measurement accuracy of 1 Pa, and the variations of those pressure drops were in accord with the fluctuations of capillary pressure. Fourier transform was then employed to analyze the droplet break-up behaviors and confirm the numbers of daughter droplets instead of traditional microscopic imaging method. With the guidance of the pressure drop analysis, the effects of crucial factors such as surfactant concentration, fluid flow rate, and fluid viscosity on droplet break-up were investigated. The additional hydrostatic energy cost for droplet stretching and deformation in the constriction was finally discussed in contrast to the increase of interfacial energy, which were both confirmed on the level of 10−8 J/droplet.

Experimental and numerical analysis of thermal flow in open-cell porous metal during Darcy-Forchheimer transition regime

A numerical analysis of pressure drop and heat transfer for open-cell porous media is performed using a three-dimensional conjugate heat transfer model. Porous metal with a pore density of 20 pores per inch (PPI) and porosity of 95.7% is used in the present numerical simulation. Real microstructure of the open-cell porous metal is constructed using stacked images obtained by X-ray computed tomography method. Computed thermal-fluid characteristics are compared directly with the experimental pressure drop and unit overall thermal resistance values. The flow through porous metal can be divided into the Darcy regime and the Forchheimer regime. The thermo-fluidic characteristics in the Darcy regime and the Forchheimer regime are investigated numerically. The flow separation is not observed in the Darcy regime, but the wake region occurs in the Forchheimer regime because of the flow separation on the ligament surface. The contribution of the total drag acting on the walls (top & bottom) is very small, namely, less than 5% compared to the total drag on ligaments. The total drag force coefficient of ligaments tends to converge at high Reynolds number. This is because the pressure drag force is dominant due to the wake effect in the Forchheimer regime. Local Nusselt number is large near the upstream side of the ligament and very low in the wake region. Average Nusselt number increases with Reynolds number. In the Forchheimer regime, wakes developed behind ligaments increase the pressure loss and decrease the heat transfer performance.

Separation Characteristics in a Novel Gas–Liquid Vortex Separator

Fischer–Tropsch (FT) synthesis is an essential way to achieve the cleanliness of oil products. A novel gas–liquid vortex separator (GLVS) was put forward to use in the FT synthesis. GLVS has four symmetry vortex arms set inside the separator body. The characteristics of pressure drop and separation efficiency of the GLVS were investigated through a large-scale cold model. The influences of the inlet gas velocity and the inlet liquid concentration on the separator were analyzed. An improved weighting method to calculate the droplet separation efficiency was proposed. The experimental results indicated that the GLVS fits the aerodynamic design and can be operated stably. The dimensionless standard deviation of the pressure drop is maintained within 2%. The “roof skimmers” is not suitable for the GLVS based on visual observation and analysis of the segmental pressure drop, which exacerbates the entrainment. The improved GLVS-2 removes the roof skimmers and increases the diameter of the outlet pipe (vertical) by 0.1 m. These changes reduced the total pressure drop by about 50% compared with the GLVS-1. A model was proposed to predict the pressure drop, wherein the Eu number is 8.08. The pressure drop of the GLVS is mainly affected by the gas velocity, and the liquid concentration has less effect on the pressure drop. The Sauter mean diameter of the droplets initially entering the GLVS is 15.27 μm. It is found that the separation efficiency of the GLVS-2 is about 10% higher than that of the GLVS-1. The liquid critical concentration of the GLVS-2 is related to the gas velocity. Although the entrainment above the vortex arms formed the water bath at a high gas velocity in GLVS-2, it has a positive effect on the separation. The combination of the empirical droplet size model and equilibrium-orbit model can be used to predict the separation efficiency of GLVS-2 with an average deviation of 1.95%.

Numerical analysis of pressure drop and temperature in a hairpin heat exchanger with different shell and tube bank arrangements

Numerical analysis of pressure drop and temperature in a hairpin heat exchanger with different shell and tube bank arrangements

The Analysis of Pressure Drop on RL 014 for Condensate Disposal on Geothermal Pipe Line

Geothermal energy from the Earth's magma is manufactured in the form of hot steam. On the process of transmission of steam in the Pipe Line, there are various problems such as condensation in the steam. Condensation can cause problems such as pressure drop. The formation of condensate gives a negative impact on production activities both in the pipeline or power plant, thus condensate formed in pipelines should be disposed of via the blow down or steam trap. Due to a large number of steam pipelines in the DW area then to do an analysis of pipelines in order to prioritize the disposal of condensate in the pipe more prone formed condensate. DW Area special analysis was not done against condensation and the number of condensates that are formed so as to indicate the occurrence of condensation done with regular analysis pressure drop in the pipeline. The results of the analysis of the pipeline must first and more frequently carried out disposal of condensate on the RL 014 based on pressure drop highest is line DW 14 a and DW 67, next line DW 18 and 17, and the last is the line 11 and 14 b DW. The condition of the steam trap is also noteworthy if the steam trap leak then it can lower the temperature in the pipe. The drop in temperature in the pipeline will accelerate the condensation, the results of the analysis there is a steam trap leaked is 401.00.17.ST19 and 401.00.05.ST14 . Steam trap leaked that needs to be done to combat the most. The production of steam RL 014 per day was able to donate a 52.52% or about 73.5 MW of the total needs of PLTP (geothermal power plant) 140 MW per day.

Pressure drop analysis on the positive half-cell of a cerium redox flow battery using computational fluid dynamics: Mathematical and modelling aspects of porous media

Description of electrolyte fluid dynamics in the electrode compartments by mathematical models can be a powerful tool in the development of redox flow batteries (RFBs) and other electrochemical reactors. In order to determine their predictive capability, turbulent Reynolds-averaged Navier-Stokes (RANS) and free flow plus porous media (Brinkman) models were applied to compute local fluid velocities taking place in a rectangular channel electrochemical flow cell used as the positive half-cell of a cerium-based RFB for laboratory studies. Two different platinized titanium electrodes were considered, a plate plus a turbulence promoter and an expanded metal mesh. Calculated pressure drop was validated against experimental data obtained with typical cerium electrolytes. It was found that the pressure drop values were better described by the RANS approach, whereas the validity of Brinkman equations was strongly dependent on porosity and permeability values of the porous media.

Study on fracturing fluid filtration fracturing technology

The filtration of fracturing fluid is one of the important factors that affect the effect of fracturing construction. Therefore, it is of great significance to study fracturing fluid loss for fracturing technology. Based on the fracturing fluid filtration theory, the fluid loss coefficient is used to describe the loss of the fracturing fluid in the formation. At the same time, according to the different formation conditions, the corresponding pressure drop analysis model is used to describe the pressure falling process. According to a target area, the filter loss parameter is calculated by combining the filtration mechanism and the pressure drop pressure drop analysis model. It is necessary to study the fracturing fluid technology and optimize the fracturing fluid with the concentration of 4% of the filtrate reducer, which is compared with the original formula with the concentration of 1% of the original filtrate loss agent. The loss coefficient is reduced by 44.13% on average, which can better meet the actual demand.

An Elongational and Shear Evaluation of Polymer Viscoelasticity during Flow in Porous Media

This paper uses a combination of approaches to evaluate the viscoelastic phenomenon in high-molecular-weight polymers (24–28 M Daltons) used for enhanced oil recovery (EOR) applications. Rheological data were cross-analyzed with single- and two-phase polymer flooding experiments in outcrop cores and micromodels, respectively. First, the impact of semi-harsh conditions (salinity, hardness, and temperature) was evaluated. Second, the impact of polymer degradation (sand face flow), focusing on the viscoelastic properties, was investigated. Finally, polymer viscoelastic properties were characterized, proposing a threefold rheological approach of rotational, oscillatory, and elongational behavior. Data from the rheological approaches were cross-analyzed with core flooding experiments and performed at a room temperature of 22 °C and at a higher temperature of 55 °C. The change in polymer viscoelastic properties were analyzed by investigating the effluents from core flooding experiments. Oil recovery experiments in micromodel helped our understanding of whether salinity or hardness has a dominating impact on in situ viscoelastic polymer response. These approaches were used to study the impact of mechanical degradation on polymer viscoelasticity. The brines showed notable loss in polymer viscoelastic properties, specifically with the hard brine and at higher temperature. However, the same polymer solution diluted in deionized water exhibited stronger viscoelastic properties. Multiple flow-behaviors, such as Newtonian, shear thinning, and thickening dominated flow, were confirmed through pressure drop analysis against interstitial velocity as already reported by other peer researchers. Turbulence-dominated excessive pressure drop in porous media was calculated by comparing core flood pressure drop data against pressure data in extensional viscometer–rheometer on a chip (eVROC®). In addition, a significant reduction in elastic-dominated flow was confirmed through the mechanical degradation that happened during core flood experiments, using various approaches. Finally, reservoir harsh conditions (high temperature, hardness, and salinity) resulted in a significant reduction in polymer viscoelastic behavior for all approaches.

Effect of polyHIPE porosity on its hydrodynamic properties

Several polymerized high internal phase emulsions (polyHIPE) of various porosity but the same pore diameter were prepared. It was demonstrated that the pore size distribution of void pores and interconnecting pores is similar and it can be described by a log-normal distribution. Flow-through porosity matches closely static porosity and the non-polymerizable fraction of initial emulsion, demonstrating an open structure of polyHIPE that allows flow through the entire porous polymer. Pulse response experiments demonstrated flow uniformity. Pressure drop analysis allowed estimation of porosity effect on permeability. Fitting of experimental data with different pressure drop models revealed that interconnecting pore diameter should be used as a characteristic dimension to describe pressure drop on polyHIPE accurately. Linear correlation between permeability and flow-through porosity demonstrated that the effect of the porous polymer structure on the flow properties is independent of porosity. This finding suggests that polyHIPE hydrodynamics does not change with porosity, facilitating prediction of their performance for various applications where flow-through mode is important.

Pressure Drop Analysis and Prediction of Wind Power Stations Lubrication System Based on CFD and GRNN

Pressure Drop Analysis and Prediction of Wind Power Stations Lubrication System Based on CFD and GRNN

Transforming pool boiling into self-sustained flow boiling through bubble squeezing mechanism in tapered microgaps

We demonstrate a mechanism to transform a pool boiling system into a self-sustained flow boiling system through bubble-induced two-phase flow in a tapered microgap over the heater surface. The nucleating bubbles in the gap are squeezed and expand preferentially in the increasing taper direction. The expanding flow cross section decelerates the two-phase flow and converts the momentum loss into pressure buildup. The bubble squeezing and the pressure recovery effects overcome the frictional and acceleration pressure drops to provide a net pumping head. We hypothesize that the resulting self-sustained flow eliminates the need for an external pump and transforms a pool boiling system into a pumpless flow boiling system with significantly higher heat transfer potential. Experiments were carried out with water in 10° and 15° tapered gaps over a 10 mm square heater surface with an inlet gap height of 1.27 mm. The plain heater surface with a 15° tapered gap reached a critical heat flux of 288 W/cm2 with a heat transfer coefficient of 119 kW/m2 °C as compared to 127 W/cm2 and 52.5 kW/m2 °C with only a plain surface. High-speed imaging revealed that the bubbles nucleating at the entrance in the gap are squeezed and expand in the increasing cross section direction. A homogeneous flow model was used for pressure drop analysis in the expanding gap. The results indicate that the pressure recovery mechanism alone cannot sustain the flow and the bubble squeezing action plays a critical role in establishing the self-sustained flow.

Modeling of double-layer triangular microchannel heat sink based on thermal resistance network and multivariate structural optimization using firefly algorithm

The micro-channel heat dissipation system has minor specifications and good thermal conductivity per unit, which is the best choice for heat dissipation of micro-chips. By optimizing the cross section of microchannel, the heat exchange efficiency and temperature uniformity can be effectively improved. In this article, a double-layer triangular microchannel heat sink is proposed, which uniquely combines triangular cross section and double-layer structure to obtain a better heat dissipation performance. A new thermal resistance network model is established. At the same time, the model of pressure drop in microchannel heat sink is obtained by use of fluid theory. Taking thermal resistance and pressure drop as optimization objectives, the thermal resistance of double-layer triangular microchannel heat sink is 0.284 K/W and the pressure drop is 1386.89 Pa by using the firefly algorithm based on the Pareto optimal solution set, obtaining the optimal structural parameters. The thermal-flow-solid coupling simulation analysis shows that the thermal resistance and theoretical analysis error is 5.19%, and the pressure drop and theoretical analysis error is 9.49%, which can verify the accuracy of the thermal resistance network model. This article has a guiding significance for the thermal resistance analysis and heat dissipation improvement of non-rectangular cross section microchannel heat sinks.

Numerical analysis of pressure drop of HEPA filter in fuel cycle facility under Fire

Numerical analysis of pressure drop of HEPA filter in fuel cycle facility under Fire

Studying the Effect of Perforation Parameters on Vertical Well Performance

This paper presents a pressure drop analysis in perforated vertical wellbores for different perforation parameters. The effect of the density of the perforations (number of perforation), the phase angle of the perforations, the diameter of the perforation and the flow rate of the crude oil from the perforations on the pressure drop and the productivity index of the perforated vertical wellbores were studied. The analysis of the vertical wellbore was performed numerically using ANSYS FLUENT 15.0 software. Three dimensional, steady-states, turbulent and incompressible fluid flow is assumed during the numerical solution of the governing equations. The results of this study show that, increased perforation density of the perforated vertical wellbore caused an increase in pressure drop, and also, decreased productivity index due to increasing the friction losses. Friction pressure drop has a significant effect on crude oil flow into the wellbore. When the main velocity is 1.5 m/s and the inlet velocity from the perforations is 2 m/s, the friction pressure drop is about 66 % and the acceleration pressure is approximately 34 % of the total pressure drop.