Change In Pressure Drop Research Articles

Effect of Flow-pattern Reconstruction on Combustion Efficiency and Pollutant Emission in CFB Boiler

The effect of flow-pattern reconstruction on combustion efficiency and pollutant emission in CFB boilers was investigated with a 1-D CFB combustion model. The results from the 1-D model agree well with the field test data. It was found that, the mass fraction of fine coal particles should be increased at lower bed pressure drop to achieve flow-pattern optimization. As the bed pressure drop decreases, the carbon content decreases first and then increases, both in fly and bottom ash. The change of bed pressure drop is the main factor in the influence of flow-pattern optimization on SO2 emission. The higher the bed pressure drop is, the lower the SO2 emission concentration is. Bed pressure drop and coal size distribution are the chief factors of NOx emission concentration in flow-pattern optimization. With the decrease in bed pressure drop and increase in mass fraction of fine particles, NOx emission concentration decreases first and then increases. SO2 emission concentration can be decreased below 100 mg/m3 by increasing Ca/S, while the original emission concentration of NOx increases. Therefore, other assistant adjustments are also needed to achieve flow pattern optimization, such as the secondary air proportion and CaO particle size distribution.

Methodology of using the Adjoint solver optimization tool during flow in the intercooler filling line to minimize pressure drop

The paper deals with numerical modelling of the flow in the intercooler filling line by Adjoint solver to minimize pressure loss. The ANSYS Fluent software was used for the calculations. The basic flow calculation was performed in the first phase. Then the mathematical model with Adjoint solver optimization tool was defined. The numerical calculation was unstable and did not lead to a convergent solution, because of creation of vortexes. The mathematical model was simplified in the second phase. To suppress instabilities and vortices a dynamic viscosity of coolant was adjusted. The pressure gradients between inlet and outlet for unmodified geometry and for modified geometry were evaluated. The final evaluations of pressure drop changes were implemented for modified geometry with original dynamic viscosity of the coolant.

Effect of Coal-Dust Fuel and Compensating Measures on Blast Furnace Charge Softening Zone Gas Permeability

The effect of coal-dust fuel and the main compensating measures on the change in gas pressure drop in a blast furnace charge softening zone (Δpsz ) is estimated by calculation. The change in gas permeability in the charge softening zone is evaluated using a mathematical model based on contemporary concepts of the softening zone structure. Calculations show that an increase in coal-dust fuel consumption from 100 to 160 kg/ton of pig iron is accompanied by an increase in Δpsz . In order to reduce the Δpsz with injection of this fuel, compensating measures are used in the mathematical model. An increase in iron content in the charge from 56 to 60% provides a reduction in the Δpsz by 1.1–1.5%. An increase in coke strength from 40 to 50% makes it possible to reduce Δpsz by 20–25%. Use of iron-ore materials with a lower softening temperature range makes it possible to reduce Δpsz by 25%. In addition, formation of developed axial gas flow makes it possible to reduce Δpsz by a factor of 2.6.

Numerical Estimation of Heat Recovery within a Distributed Incinerator Using Water and Hydrocarbons as Working Fluids

The potential of a cogeneration system combined with a small combustion furnace was investigated in this study. The heat transfer between the exhaust gas and working fluid flowing in a spiral tube heat exchanger was estimated numerically and the amount of vapor generated was predicted. The combustion chamber had a 0.49 m3 inside volume with a chimney height of 2.5 m and an inner diameter of 0.28 m. A uniform gas side temperature condition that was referenced from the results of a preliminary experiment and a computational fluid dynamics simulation were adopted to simplify calculations and clarify the effects of working fluids. The amounts of heat recovery when utilizing water and other types of working fluids (Pentane, Butane) were compared. The most effective tube length considering pressure drop and phase change was also predicted. Isentropic theoretical thermal efficiency and T-s diagrams are analyzed to evaluate the vapor-power conversion rate using waste heat. As a result, a potential the heat recovery rate of approximately 100 kW at a 150 kg/h mass flow rate is expected.

Wettability alteration in carbonate and sandstone rocks due to low salinity surfactant flooding

Commonly, desorption of crude oil from rock surfaces accomplished by the exposure to the decreasing salt concentrations of NaCl, Na2SO4, MgCl2 and CaCl2 solutions. However, adsorption and desorption of crude oil are the functions of several attributing factors at undoubtedly low salinity brine solutions. For silica surfaces, both rock and oil possess negative charges during low salinity injection that leads to the electrical double layer expansion and electrostatic repulsion between them. For carbonate rocks, rock dissolution and negatively charged surface at higher pH could be regarded as the driving forces for oil desorption. Thus, adsorption/desorption studies of different oils over silica and carbonate rocks while considering salinity, ion composition and aging of the rocks would be sufficient to alter the wettability of the rocks. In the present paper, the effect of saline water containing surfactant has been discussed on the performance of enhanced oil recovery (EOR). Wettability alteration triggered by the change in interfacial tension (IFT) between crude oil and low salinity surfactant (LSS) is known to be the main factor regarding EOR processes. However, wettability depends on several factors, namely, multiple ion exchange (MIE), interfacial elasticity modulus, cation bridging, acid/base numbers of oil, rock composition and structure, ratio of divalent/monovalent (M2+/M+) cations in the formation brine, aging time, the status of zeta potential, surfactant structure and concentration, pH of the medium, T & P of reservoir, permeability and pressure drop change. Therefore, we thoroughly examine the microscopic mechanisms of LSS flooding via studying individual aforementioned factors that influence the contact angle change in sandstone and carbonate rocks.

Managing the power grid: how myoglobin can regulate PO2 and energy distribution in skeletal muscle.

Managing the power grid: how myoglobin can regulate PO2 and energy distribution in skeletal muscle.

Experimental investigation on pressure drop of a laboratory‐scale random packing column under roll and heave motion

AbstractThe effects of tilt, roll, and heave ship motion on pressure drop were investigated in a laboratory‐scale random packing, which was located at a six degree of freedom (6DoF) motion parallel platform. The water‐air system was adopted, and various operating condition (liquid load and F‐factor) as well as sea states were tested. In tilted states, the pressure drop was decreased as the tilted angle increased, which was associated with the reduction in liquid hold‐up. Under a roll and heave motion, it was found that the pressure drop fluctuated around the value of vertical state. Subsequently, the relative change in pressure drop was introduced to reflect the influence of sea state. It was found that the relative change in pressure drop monotonously decreased as the heave motion frequency decreased, but it could inversely increase under a low‐frequency roll motion, particularly under high liquid load with a large size Pall ring.

Investigation of Pressure Drop of Trapped Oil in Capillaries with Circular Cross-Sections

An investigation is performed to determine the cause of the pressure drop for mobilizing a trapped oil slug in capillaries with circular cross-sections. This research is focused on pressure drop across the tube at different stages of oil mobilization and the physics behind the rapid decrease during slug separation. Pressure drop decease in the hold-up stage, which is too small to be observed experimentally, and the severe change of pressure drop during the slug detachment process are observed and quantitatively analyzed using computational fluid dynamics. The method used for the analysis is the equivalent viscosity model. For different slug lengths and multislug cases, the role of the capillary pressure difference in the process of trapped oil migration is well-recognized. The influence of oil dispersion in porous media on pressure drop when saturation is constant is also discussed. Compared with multislug pressure drops, the relative error of the equivalent viscosity model and computational fluid dynamic...

Influence of heating surface characteristics on flow boiling in a copper microchannel: Experimental investigation and assessment of correlations

Experiments were carried out to investigate the effect of surface characteristics on flow boiling heat transfer and pressure drop in a microchannel using degasified and deionized water as the working fluid. Test section consists of a 40 mm long, 0.5 mm wide and 0.24 mm deep microchannel machined in copper. Experimental results are reported for three different surface characteristics – fresh machined surface (case-1), the same channel surface when aged after repeated experimentation (case-2) and the surface obtained after cleaning the same aged surface with 0.1 M hydrochloric acid (case-3). Parameters considered include inlet temperature 95 °C, mass flux from 1000 to 2220 kg/m2 s and heat flux from 400 to 1200 kW/m2. Single-phase experiments have been performed to estimate the heat loss from microchannel and also to validate the experimental setup. The results indicate that the boiling heat transfer performance of case-2 is lower than that of case-1 and the performance of case-3 is higher than that of case-1. The main reason behind the reduction of two-phase heat transfer coefficient for case-2 as compared to case-1 is attributed to the increased wettability due to the thermal oxidation of the heating surface caused by the repeated experimentation. The enhanced boiling performance of case-3 is attributed to the increased nucleation site density. However, the change in the two-phase pressure drop is relatively small. The experimental results were compared with the available correlations in the literature to check the predictability of the correlations for the three cases. The degree of agreement (or disagreement) varies depending on the correlation and the surface characteristic. The reasons for the deviations are discussed.

Effects of different roughness elements on friction and pressure drop of laminar flow in microchannels

PurposeAccording to very small dimensions of the microchannels, producing a microchannel with smooth surfaces is approximately impossible. The surface roughness can have a specific effect on microchannel performances. This paper aims to investigate the changes in friction and pressure drop in the microchannels by considering the different roughness elements on microchannel wall and changes in elementary geometry and flow conditions. Results show a significant effect of roughness on the pressure drop and friction.Design/methodology/approachTwo-dimensional fluid flow in the rough microchannels is analyzed using FLUENT. Microchannels have a height of 50 µm. Water at room temperature (25°C) has been used as working fluid. The Reynolds numbers are considered in laminar flow range and from 50 to 300.FindingsThe results show that the value of friction factor reduces nonlinearly with an increase in Reynolds number. But, the pressure drops and the Poiseuille number in the microchannels increase with an increase in Reynolds number. The values of the pressure drop and the friction factor increase by increasing the height and size of the roughness elements, but these values reduce with an increase in the distance of roughness elements.Originality/valueThe roughness elements types in this research are rectangular, trapezoidal, elliptical, triangular and complex (composed of multiple types of roughness elements). The effects of the Reynolds number, roughness height, roughness distance and roughness size on the pressure drop and friction in the rough microchannels are investigated and discussed. Furthermore, differences between the effects of five types of roughness elements are identified.

Separation of Gas Mixtures in a Fixed-Bed Adsorbent

Pressure drop changes in a fixed bed of synthetic zeolite NaA and natural clinoptilolite from Ai-Dag field (Azerbaijan) are studied as functions of the incoming gas flow rate. Conditions for attaining the maximum adsorbent capacity during adsorptive separation of a CH4/CO/CO2/N2 gas mixture are created in the zeolite fixed bed if the pressure drop is maintained in a certain range. A system of equations describing the relationships of the pressure drop during gas-phase adsorption in a clinoptilolite fixed bed and the incoming gas flow rate that ensure the most complete utilization of the adsorbent capacity is proposed.

Numerical Simulation of the Separation Flow Field in a Gravitational Oil-water Separator

The RNG k-ε model and Euler model are used to simulate the internal flow field of the corrugated plate separator. By comparing the pressure drop and the interfacial distribution of oil and water at different opening ratios, we obtain the coalescence characteristics of corrugated plates. The results show that the corrugated plate pressure drop decrease with the increase of the opening ratio. The higher the opening ratio is, the slower change of pressure drop along the flow channel is. The interfacial area of oil and water decreases first and then slowly increases with the increase of opening ratio, and reaches the maximum after the corrugated plate with opening ratio of 0%, and gets the minimum after the corrugated plate with opening ratio of 10%, which means the best opening ratio is about 10%. The hole in the corrugated plate can eliminate the barrier of the corrugated plate to the oil phase and promote the floating rise of the oil phase which means the corrugated plate with holes has good separation effect.

A pressure drop study for packed bed adsorption thermal energy storage

Adsorption thermal energy storage has received considerable attention as it can overcome the mismatch between supply and demand of renewables, providing high energy storage per volume. In the packed bed adsorption thermal energy storage, pressure drop is of key concern since higher pressure drop leads into lower energy storage efficiency. In this paper, an experimental and modeling investigation on the pressure drop inside the adsorption packed beds is performed. An accurate semi-analytical closed-form relationship is proposed to calculate the pressure drop inside a column of adsorbent materials, taking into account the Laplacian friction, as well as the inertial effects. The model covers a wide range of porosity, between low-permeability medium, a dense packed bed of spherical particles, and high-permeability media, a pure viscous fluid. A modified permeability is defined to consider the inertial effect for a moderate range of the particle Reynolds number (0 < Rep < 300). An experimental apparatus is designed for measuring the pressure drop for different bed sizes and inlet air velocities. The proposed model shows good agreement with the experimental data with the relative difference of 7.6% at 0.73 m/s for silica gel and 15.3% at 0.84 m/s for zeolite 4A packed beds. The experiment reveals that the effect of water uptake on the pressure drop of packed bed with wet adsorbent is negligible in the tested particle Reynolds number range, with a relative difference of less than 1.0% compared to dry adsorbent for 18–30 cm long columns. The proposed formula for pressure drop, consequently, can be applicable for wet adsorbents regardless of the water uptake amount, with a good level of accuracy. Moreover, the analytical model shows up to ±2% change in pressure drop due to heat of adsorption of the tested adsorber columns.

Experimental analysis for heat transfer of nanofluid with wire coil turbulators in a concentric tube heat exchanger

Abstract Nanofluids are a novel class of heat transfer suspensions of metallic or nonmetallic nanopowders with a size of less than 100 nm in base fluids and they can increase heat transfer potential of the base fluids in various applications. In the last decade, nanofluids have become an intensive research topic because of their improved thermal properties and possible heat transfer applications. For comparison, an experiment using water as the working fluid in the heat exchanger without wire coils was also performed. Turbulent forced convection heat transfer and pressure drop characteristics of Al2O3-water nanofluids in a concentric tube heat exchanger with and without wire coil turbulators were experimentally investigated in this research. Experiments effected particle volume concentrations of 0.4–0.8 to 1.2–1.6 vol% in the Reynolds number range from 4000 to 20,000. Two turbulators with the pitches of 25 mm and 39 mm were used. The average Nusselt number increased with increasing the Reynolds number and particle concentrations. Moreover, the pressure drop of the Al2O3-water nanofluid showed nearly equal to that of pure water at the same Reynolds number range. As a result, nanofluids with lower particle concentrations did not show an important influence on pressure drop change. Nonetheless, when the wire coils used in the heat exchanger, it increased pressure drop as well as the heat transfer coefficient.

Characteristics on condensation heat transfer and pressure drop for a low GWP refrigerant in brazed plate heat exchanger

Refrigerants have been continuously developed to improve their thermal performances and to deal with relevant environmental issues. Recently, regulations on refrigerants are being intensified due to the global warming. To meet the enhanced environmental standards, low global warming potential (GWP) refrigerants have been developed. In this study, experimental studies are conducted to investigate the characteristics of condensation heat transfer and frictional pressure drop for R-1233zd(E). The experiments are carried out under partial condensation conditions in a plate heat exchanger to measure temperature, pressure and mass flow rate. Heat transfer coefficients and frictional pressure drops with respect to mean vapor qualities are yielded. During the partial condensation process, the heat transfer coefficients increases as the mass and heat fluxes increase. However, no significant change in frictional pressure drop is observed when the heat flux changes. It is concluded that other correlations for Nusselt number and pressure drop from the literature cannot be applied for the low GWP refrigerant, R-1233zd(E), and the present experimental correlations agree well with the experimental results with the error bands of ±20%.

Facile Fabrication of Nanostructured Microchannels for Flow Boiling Heat Transfer Enhancement

ABSTRACTFlow boiling in microchannels promises high heat transfer due to the combined effect of latent heat of vaporization and forced convection in confined spaces. However, flow boiling based miniaturized thermal management devices are limited due to instability induced dryout. While several efforts have been made to delay instabilities via advanced surface modification techniques, there is a need to expand the scope of applications by developing low-cost and scalable fabrication technologies for commonly used heat exchanger materials. In this paper, we use a facile and self-limiting chemical oxidation technique for fabricating sharp needle-like superhydrophilic CuO nanostructures within six parallel 500 × 250 µm2 microchannels spread uniformly over a 1 × 1 cm2 area in a copper heat sink. We demonstrate heat transfer enhancement with nanostructured microchannels (NSM) without any appreciable change either in the average pressure drop or the fluctuations in comparison to baseline plain wall microchannels (PWM). Analysis of the high-speed images was performed to attribute the enhancement with NSM to the presence of a capillarity-fed thin-film evaporation regime, which otherwise was absent in PWM. We believe that these results are encouraging and suggest that the heat sink geometry can be optimized to investigate the true potential of nanostructured microchannels.

Pressure drop and velocity changes in MHD pipe flows due to a local interruption of the insulation

In liquid metal blanket concepts, such as the dual coolant lead lithium (DCLL) blanket, in which the PbLi serves to cool the breeding zone, the liquid metal has to flow with sufficiently large velocity to guarantee a suitable removal of the volumetric heat generated in the fluid. Large velocities lead to a high pressure drop caused by magnetohydrodynamic (MHD) interactions of the liquid metal with the plasma confining magnetic field. In order to reduce MHD pressure losses in DCLL blankets, it is foreseen to decouple electrically the PbLi from the conducting wall of the ducts. This can be achieved by inserting insulating layers inside pipes and channels. In this paper we investigate MHD flows in well-conducting pipes with flow channel inserts (FCI). The influence on the pressure drop of the finite electric conductance of the layer and of the presence of an interruption in the insulation is analyzed. Numerical results show that under realistic operating conditions, i.e. for sufficiently small electric conductance of the insert and large magnetic fields, the ensuing additional MHD pressure losses are still acceptable. However, the discontinuity of the insulation causes significant modifications of the velocity distribution in the pipe, which have to be taken into account, since they can affect heat and mass transfer phenomena.

Numerical analysis of a gas turbine combustor fueled by hydrogen in comparison with jet-A fuel

The interest in alternative fuels has increased in recent years. Because, the conventional fuels have the danger of extinction in the near future and these fuels harm the environment. Therefore, in this study, the availability of hydrogen as an alternative fuel has been investigated in the tubular combustion chamber of a gas turbine engine fueled by jet-A fuel. For this purpose, the combustion characteristics in the combustor of a Rolls-Royce Nene turbojet engine fueled by gas jet-A and hydrogen have been numerically studied at different excess air ratios (EAR) for a given thermal power values. Temperature distributions in the combustor, combustion efficiency, pressure drop and velocity change have been numerically analyzed at 1480 kW (10000 rpm), 2290 kW (11000 rpm) and 2980 kW (12000 rpm) thermal power in the combustion chamber. The RNG k- turbulence and eddy-dissipation combustion models have been used for 2D axisymmetric geometry with swirling flow.The combustion efficiency and the pressure drop values are increasing with an increase in the EAR values. But, the outlet temperature values of the combustion chamber, the CO2 emissions and unburned HC emissions are decreasing by increasing of the EAR values. Moreover, it is observed that the NOx emission values are increasing and then are decreasing with the EAR values. The combustion of hydrogen is seen as advantageous in terms of pressure drop, temperature values at the combustion chamber outlet and CO2 and unburned HC emissions. In addition, it can be seen that as advantageous in terms of the NOx emission values at low EAR values but as disadvantageous at high EAR values.

The Influence of Flooding Phenomenon to Pressure Drop on Hotleg Simulator with L/D=25

Cooling system in nuclear reactor is much influenced by counter-current flow. When a leakage is occured, coolant in primary circuit of hotleg and hot steam from reactor will flows in counter-current condition. An experimental investigation has been performed to examine the effect of flooding phenomenon on the pressure drop. It was observed using acrylic complex pipe as hotleg simulator consisting of three parts: horizontal, bend and inclined pipe. Geometrical sizes of pipes was in scale of 1/30 of the actual hotleg geometrical size in the PWR with inner diameter=25.4 mm, the horizontal pipe length L=635 mm, and inclined pipe length was 20 mm with an angle of 50o. Pressure drop was meassured by using differential pressure sensor installed in the lower-tank (RPV simulator) dan upper-tank (SG simulator). Pressure drop was observed before, during and after flooding. Based on the observation, it was found that the change of flow pattern is followed by the change of pressure drop. The results of this study were also compared with some correlations using the dimensionless superficial velocity parameter by Wallis correlation. Wallis correlation can be written as JG*1/2 + 0,3974 JL*1/2 = 0,4832 .

Field measurement and modeling of UVC cooling coil irradiation for heating, ventilating, and air conditioning energy use reduction (RP-1738)—Part 1: Field measurements

Wet cooling coil surfaces can provide opportunities for microorganism growth. This biological fouling (biofouling) increases airside pressure drop and decreases airside heat transfer coefficient. Ultraviolet germicidal irradiation is one method to eliminate biofouling. The current article reports field measurements of changes in pressure drop and heat-transfer characteristics of fouled coils treated with ultraviolet germicidal irradiation designed for surface disinfection. Ultraviolet germicidal irradiation systems were installed in operating air-handling units with visibly fouled cooling coils at sites in Tampa, Florida and University Park, Pennsylvania. Pressure drop data were controlled for airflow and latent load, and overall heat-transfer coefficient data were controlled for heat exchanger entering conditions. Analysis of Tampa site data showed an initial mean 22.70% to 22.72% decrease (µ ± 2σ) in airside pressure drop and a mean 13.2% to 13.6% (µ ± 2σ) increase in overall heat-transfer coefficient. Longer-term improvement was 14.6% for the airside pressure drop and 15.7% for overall heat-transfer coefficient, though the decrease in pressure drop improvement was not able to be explained. The University Park, Pennsylvania site, cleaned by unaware maintenance personnel before data collection, had an initial mean 10.3% pressure drop improvement and 57.7% overall heat-transfer coefficient improvement, followed by a long-term 0% pressure drop improvement and 36.7% overall heat-transfer coefficient improvement.