Pressure Drop in Solar Power Plant Chimneys

2003 ◽  
Vol 125 (2) ◽  
pp. 165-169 ◽  
Author(s):  
Theodor W. von Backstro¨m ◽  
Andreas Bernhardt ◽  
Anthony J. Gannon
Keyword(s):  
Pressure Drop ◽  
Kinetic Energy ◽  
Separated Flow ◽  
Wall Friction ◽  
Solar Chimney ◽  
Rectangular Section ◽  
Frictional Pressure Drop ◽  
Internal Bracing ◽  
Flow Through ◽  
Kinetic Energy Loss

The paper investigates flow through a representative tall solar chimney with internal bracing wheels. It presents experimental data measured in a 0.63-m-dia model chimney with and without seven bracing wheels. The bracing wheels each had a rim protruding into the chimney and 12 spokes, each spoke consisting of a pair of rectangular section bars. The investigation determined coefficients of wall friction, bracing wheel loss, and exit kinetic energy in a model chimney, for both ideal non-swirling uniform flow and for swirling distorted flow. A fan at one end of the chimney model either sucked or blew the flow through it. The flow entering the chimney through the fan and its diffuser simulated the flow leaving the turbine at the bottom of the chimney. The swirling distorted flow increased the total pressure drop by about 28%, representing 4.7% of the turbine pressure drop. The pressure drop across the bracing wheels exceeded the frictional pressure drop by far. Designers of tall, thin-walled chimneys should take care to minimize the number of bracing wheels, reduce their rim width as much as possible, and investigate the feasibility of streamlining their spoke sections. If at all structurally possible, the top bracing wheel should be far enough from the chimney exit to allow the spoke wakes to decay and the separated flow to re-attach to the chimney wall downstream of the rims before the flow leaves the chimney, to reduce the exit kinetic energy loss.

Pressure Drop in Solar Power Plant Chimneys

Solar Energy ◽  
2002 ◽  
Author(s):  
Theodore W. von Backstro¨m ◽  
Andreas Bernhardt ◽  
Anthony J. Gannon
Keyword(s):  
Pressure Drop ◽  
Wall Friction ◽  
Rectangular Section ◽  
Pressure Drops ◽  
Through Flow ◽  
Radial Spokes ◽  
Friction Pressure Drop ◽  
Internal Bracing ◽  
Order Of Magnitude ◽  
Flow Through

The paper investigates the flow through a representative tall solar chimney with seven sets of internal bracing wheels with radial spokes. The paper presents experimental data measured in a 0.63 m diameter laboratory scale chimney model with and without bracing wheels. A fan at one end of the chimney model either sucked or blew the flow through it. The measured friction pressure drop was higher than theoretical values for smooth walls, and swirling, blown flow increased it by another 12%. The seven bracing wheels, each had twelve spokes, each spoke consisting of a pair of rectangular section bars, caused order of magnitude larger pressure drops than wall friction. For the sucked-through flow the forced, swirling, disturbed flow increased the pressure drop by up to 36%. Bracing wheels also increased the exit kinetic energy coefficient to 1.26 with the last wheel at the chimney exit. This effect could in combination with the bracing wheel drag reduce flow through the chimney. Designers of large chimneys should take care to minimise the number of bracing wheels, and possibly to streamline spoke sections. If possible, the top bracing wheel should be far enough from the exit for the flow to reattach to the wall after passing over the spoke attachment rim at the wall.

Two-Phase Flow Through Square and Circular Microchannels—Effects of Channel Geometry

2004 ◽  
Vol 126 (4) ◽  
pp. 546-552 ◽  
Author(s):  
Peter M.-Y. Chung ◽  
Masahiro Kawaji ◽  
Akimaro Kawahara ◽  
Yuichi Shibata
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Separated Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Channel Geometry ◽  
Frictional Pressure Drop ◽  
Channel Shape

An adiabatic experiment was conducted to investigate the effect of channel geometry on gas-liquid two-phase flow characteristics in horizontal microchannels. A water-nitrogen gas mixture was pumped through a 96 μm square microchannel and the resulting flow pattern, void fraction and frictional pressure drop data were compared with those previously reported by the authors for a 100 μm circular microchannel. The pressure drop data were best estimated using a separated-flow model and the void fraction increased non-linearly with volumetric quality, regardless of the channel shape. However, the flow maps exhibited transition boundaries that were shifted depending on the channel shape.

Evaluation of Two-Phase Frictional Pressure Drop Correlations Against Experimental Data

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Wei Li ◽  
Kunrong Shen ◽  
Boren Zheng ◽  
Xiang Ma ◽  
S. A. Sherif ◽  
...  
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Mass Flow ◽  
Flow Model ◽  
Saturation Temperature ◽  
Separated Flow ◽  
Outer Diameter ◽  
Two Phase ◽  
Homogeneous Flow ◽  
Frictional Pressure Drop

Abstract Results are presented here from an experimental investigation on tube side two-phase characteristics that took place in four tested tubes—the 1EHT-1, 1EHT-2, 4LB, and smooth tubes. The equivalent outer diameter of the tube was 9.52 mm and the inner diameter was 8.32 mm. Condensation tests were conducted using refrigerant R410A at a saturation temperature of 318 K, over a mass flow range of 150–450 kg m−2 s−1, with inlet and outlet vapor qualities of 0.8 and 0.2, respectively. Evaporation tests were performed at a saturation temperature of 279 K, over a mass flow range of 150–380 kg m−2 s−1, with inlet and outlet vapor qualities of 0.2 and 0.8, respectively. Pressure drop data of the four tested tubes were collected to evaluate five identified prediction correlations based on the separated flow model and the homogeneous flow model. The separated flow approaches presented predictions with average MAEs of 24.9% and 16.4% for condensation and evaporation data, respectively, while the average MAEs of the homogeneous flow model were 31.6% and 43.4%, respectively. Almost all the identified correlations underestimated the frictional pressure drop of the 4LB tube with MAEs exceeding 30%. An earlier transition of different flow patterns was expected to occur in the EHT tubes while developing a new diabatic flow pattern map is needed for the 4LB tube. A new correlation was presented based on the two-phase multiplier Φ and the Martinelli parameter Xtt, which exhibited excellent predictive results for the experimental data.

Evaluation of Existing Frictional Pressure Drop Correlations During Condensation of R410A in Four Horizontal Tubes

2019 ◽  
Author(s):  
Kunrong Shen ◽  
Zhichuan Sun ◽  
Wei Li ◽  
Xiang Ma ◽  
Yan He ◽  
...  
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Flow Model ◽  
Saturation Temperature ◽  
Separated Flow ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Homogeneous Flow ◽  
Frictional Pressure Drop ◽  
Horizontal Tubes

Abstract Results are presented here from an experimental investigation on tube side condensation characteristics that took place in four tested tubes — 1EHT-1, 1EHT-2, 4LB and a smooth tube. The equivalent outer diameter of the tubes was 9.52 mm and the inner diameter was 8.32 mm. Condensation tests were conducted using refrigerant R410A at a saturation temperature of 318K, over a mass flow range of 150–450 kgm−2s−1, with inlet and outlet vapor quality of 0.8 and 0.2, respectively. Pressure drop data of the four tested tubes were collected to evaluate five identified prediction correlations based on the separated flow model and the homogeneous flow model. For 1EHT-2 and the smooth tube, all the listed correlations manage to present predictions with the Mean Absolute Relative Deviation (MARD) less than 30%, while they underestimate the frictional pressure drop of the 4LB tube with MARD exceeding 40% averagely. Regarding the experimental data, it is found that the Muller-Steinhagen and Heck correlation presents the most accurate and stable prediction for the 4 tested tubes. The listed homogeneous flow correlations can provide acceptable predictions with MARD ranging from 25% to 40% under a few conditions, but their average predictive accuracies are inferior to that of the separated flow correlations. Consequently, the separated flow approach performs better than the homogeneous flow model in the prediction of frictional pressure drop for our experimental data.

Calculation of Pressure and Density in Solar Power Plant Chimneys

2003 ◽  
Vol 125 (1) ◽  
pp. 127-129 ◽  
Author(s):  
Theodor W. von Backstro¨m
Keyword(s):  
Power Plants ◽  
Average Density ◽  
Wall Friction ◽  
Solar Power Plant ◽  
Calculation Methods ◽  
Solar Chimney ◽  
Flow Area ◽  
Density Distributions ◽  
Internal Bracing ◽  
Mach Numbers

This technical brief develops calculation methods for the pressure drop in very tall chimneys, as in solar chimney power plants. The methods allow for density and flow area change with height, for wall friction and internal bracing drag. It presents equations for the vertical pressure and density distributions in terms of Mach number. One of these is a generalization of the adiabatic pressure lapse ratio equation to include flow at small Mach numbers. The other is analogous to the hydrostatic relationship between pressure, density, and height, but extends it to small Mach numbers. Its integration leads to an accurate value of the average density in the chimney.

Frictional Pressure Drop in Micro-Channel

2004 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Hiroki Takahashi ◽  
Yoshiaki Ohno
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Frictional Pressure Drop ◽  
Turbulent Transition ◽  
Friction Factors ◽  
Turbulent Flow Regime ◽  
Form Pressure ◽  
Laminar And Turbulent Flow ◽  
Flow Through

The friction characteristics of water in a sub-millimeter scale channel were investigated experimentally. The friction factors and the critical Reynolds number were measured using water flow through circular tubes with diameters of 0.5, 0.25 and 0.17 mm. The experimental results show that the measured friction factor for water agreed well with the conventional Poiseuille (λ = 64/Re) and Blasius (λ = 0.316 Re−0.25) equations in laminar and turbulent flow regime; the laminar-turbulent transition Reynolds number was approximately 2300 for diameter 0.5 mm. For diameter 0.25 mm, the friction factor evaluated by the form pressure drop also agreed well with the Poiseuille equation. For diameter 0.17 mm, the measured total friction factor was close to the Poiseuille prediction.

Pressure Drop Analysis for Liquid-Liquid Downflow Through Vertical Pipe

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
S. Ghosh ◽  
G. Das ◽  
P. K. Das
Keyword(s):  
Pressure Drop ◽  
Fluid Model ◽  
Flow Distribution ◽  
Separated Flow ◽  
High Viscosity ◽  
Flow Patterns ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Low Viscosity ◽  
Two Fluid Model

In the present paper, the pressure drop characteristics and flow patterns during downward vertical flow of lube oil-water as well as kerosene-water through a circular glass conduit have been studied. Core-annular flow has been observed to be the dominant flow pattern and it gives rise to slug flow with increase of water and/or decrease of oil velocity. However, there are subtle differences in the flow distribution observed for high viscosity and low viscosity oils. The two-phase frictional pressure drop for separated flow patterns of both the liquid pairs is predicted using two-fluid model. Since the model predictions have a large mismatch with experimental data, an empirical correlation is also proposed for improved predictions. The homogeneous and drift flux models are used for slug and dispersed flow patterns.

CFD and Optimization Study of Frictional Pressure Drop Through Bends

2019 ◽  
Vol 13 (1) ◽  
pp. 74-86 ◽  
Author(s):  
Suman Debnath ◽  
Anirban Banik ◽  
Tarun Kanti Bandyopadhyay ◽  
Apu Kumar Saha
Keyword(s):  
Pressure Drop ◽  
Gene Expression Programming ◽  
Methyl Cellulose ◽  
Blood Rheology ◽  
Bend Angle ◽  
Pseudoplastic Fluid ◽  
Frictional Pressure Drop ◽  
Different Types ◽  
Flow Through ◽  
Pipe Geometry

Background: The non-Newtonian pseudoplastic liquid flow through different types of the bend is more complicated compared to the simple straight pipe as the bends are associated with various curve geometry. Bends have wide application in bioengineering, biotechnology and biomedical such as study biofluids, blood rheology study, the design of medical equipment like equipment measuring the cholesterol etc. </P><P> Method: The papers deal with the estimation of loss coefficient and frictional pressure drop of Newtonian and non-Newtonian pseudoplastic fluid flow through the different bend of 0.0127 m diameter pipe geometry using commercially available CFD software fluent 6.3. We revised all patents relating to the pipe flow through different types of bend. The present study also deals with the efficient application of Genetic Algorithm (GA) for optimization of frictional pressure drop. Laminar Non-Newtonian Power law model is used for Sodium Carboxy Methyl Cellulose (SCMC) solution to solve the continuity and the momentum equations numerically. Generalized input-output correlation has been developed by Gene Expression Programming (GEP) using Matlab. </P><P> Results: The above-mentioned algorithm is used to predict and optimize the pressure drop. It has been found that, the process exhibit the minimum pressure drop across the bend under optimum condition (Angle = 133.160, Concentration = 0.2 Kg/m3 and velocity = 0.53 m/s). The effect of flow rate, bend angle, fluid behaviour on static pressure and pressure drop has also been investigated. </P><P> Conclusion: From the study, it can be concluded that the developed GA model has a good agreement with the CFD model. The software predicted data might be used to solve various industrial problems and also to design different equipment.

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