Inlet Pipe Research Articles

Numerical Simulation Study on the Flow and Heat Transfer Characteristics of Subcooled N-Heptane Flow Boiling in a Vertical Pipe under External Radiation

In the top submerged lance (TSL) smelting process, flow boiling may occur in the lance’s inner pipe due to the heat coming from the furnace when liquid fuel is adopted. In the current study, a numerical simulation was carried out by coupling the Eulerian two-fluid model with the improved RPI wall boiling model to investigate the subcooled n-heptane flow boiling in the inner pipe. The effects of inlet velocity and pipe wall emissivity on two-phase flow and heat transfer are elucidated. The results show that, for pipes with inlet velocity ranging from 0.3 m·s−1 to 1.0 m·s−1, an increase in inlet velocity leads to a lower void fraction near the outlet, as well as a lower average velocity and a lower average temperature of each phase. Meanwhile, the Onset of Nucleate Boiling (ONB) position approaches to the outlet, and the total pressure drop of the entire pipe reduces when the inlet velocity increases. However, the opposite trends appear when increasing the pipe wall emissivity. The maximum wall temperature corresponding to the critical heat flux (CHF) point is slightly affected by inlet velocity but significantly affected by pipe wall emissivity. The non-equilibrium effect and the specific components of pressure drop are also further investigated.

Effects of flow regime and geometric parameters on the performance of a parabolic trough solar collector using nanofluid

The present paper investigates the optimum results on the performance of a parabolic trough solar collector using (3%) CuO-water nanofluid. The single-phase model based on a three-dimensional CFD method is used to model and numerically study the heat transfer behavior and fluid flow under a turbulent regime. Effects of various parameters, including different inlet Reynolds numbers (50000 ≤ Re ≤ 250000), pipe length (0,25 m ≤ L ≤ 8 m) and pipe inner diameter (di = 60 mm, 66 mm, 72 mm, 78 mm, 82 mm, 86 mm) on the thermal and hydraulic efficiency of a parabolic trough solar collector are studied and discussed.

Thermodynamic Investigation of a Modified Compression Ignition Engine Fueled by Diesel Biodiesel Ethanol Blends

The present study contrasts the thermodynamics analysis of modified diesel engines with traditional diesel engines. Thermodynamics study is done by the use of energy and exergy analysis for diesel, B20 (blend of 80 per cent diesel by volume with 20 per cent mahua biodiesel) and LHR modification and LTC 15 per cent EGR fuelled with B20 blend and 5 per cent ethanol with various loads ranging from no load to full load. Implemented two technologies for increasing engine efficiency. One of the primary techniques is the Low Heat Rejection (LHR) concept (or the so-called “Adiabatic” engine) applied. In the engine cylinder, a ceramic layer of Alumina (Al2O3) was used to modify the Low Heat Rejection (LHR). Another technique is Low-temperature combustion (LTC) modes are added by joining the inlet and exhaust pipes through valves to control the exhaust gas at an optimal rate of 15 per cent. The findings of energy and exergy distribution in the engine were compared using optimum alterations with fuel blends such as 20 per cent mahua biodiesel and 5 per cent ethanol. From energy distribution, best shaft power (QBP) (2.8kW) is transformed from heat input observed in the optimum altered engine at full load conditions compared to others. Due to modifications employed in the engine and fuels. Maximum unaccounted energy (QUN) loss in diesel (44 %). And highest thermal efficiency (31.2 %) is revealed in B20E5 (LHR+15 % LTC). From exergy distribution, it noticed that the same trend of energy distribution and at 100 per cent load condition, maximum (12.54kW) in diesel and minimum (8.45 kW) in B20E5 (LHR+15 % LTC) has obtained input availability (Ain).The maximum conversion rate of availability in brake power (Abp) (0.61 kW) in B20 (LHR). Compared to diesel, second law or exergetic efficiency more in B20E5 (LHR+15 % LTC).

Intake Manifold Flow Study using Numerical Method with all Runners Opened

Intake manifolds have to be designed to improve engine performance by avoiding the phenomena like inter-cylinder robbery of charge, inertia of the flow in the individual branch pipes, resonance of the air masses in the pipes and the Helmholtz effect. The objective of work is to predict and analyze the flow through intake manifold of four cylinder spark ignition engine. One of the important factors is air flow inside the intake manifold; the ideal intake manifold distributes flow evenly to the piston valves. The structural analysis has been conducted to decide the thickness and material that is suitable for intake manifold to withstand bursting pressure. Three-dimensional inlet manifold was modeled in ANSYS workbench and numerically analyzed by using the commercially available FLUENT software to study the pressure, velocity and flow characteristics inside the runner. The steady state analysis has been carried out for three for All runners open, The predicted results of total pressure loss and total outlet mass flow were discussed. Inlet pipe and plenum connection creates a back step geometry which causes more total pressure loss due to flow recirculation in conventional model. Tapering the geometry is causing more inlet mass flow due to reduction in total pressure loss in the plenum chamber.

Transmission Loss analysis of a simple expansion chamber muffler with extended inlet and outlet combined with inhomogeneous micro-perforated panel (iMPP)

This paper studies the acoustic performance of a simple expansion chamber muffler combined with an inhomogeneous microperforated panel (iMPP). Three different shaped mufflers, i.e., circular, rectangular, and elliptical, with extended inlet and outlet pipes, have been studied. The thermo-acoustic module of COMSOL Multiphysics 5.5a software is used for finite element method (FEM) simulation. Then the 3D printing (stereolithography) technology is used to manufacture the samples. The transmission loss (TL) of the muffler given by the FEM simulation model is verified and measured by the Two-load method experiment, and the muffler with and without iMPP is tested. Different configurations have been tested to detect the effect of resonator absorbers based on iMPP in the expansion chambers. To observe the effectiveness of using iMPP, it is compared with other homogeneous MPPs. The results show that the TL of the low to medium frequency region increases by 25∼30 dB after adding iMPPs into the expansion chamber. Finally, the air-cavity depth behind the iMPP and the length of the expansion chamber is varied to study its effect on TL performance. The results show that the larger the cavity depth, the lower the TL peak. At the same time, with the decrease of the expansion chamber length, the TL peak gradually decreases and narrows. By carefully controlling and selecting the iMPP and expansion chamber parameters, we can obtain the required TL. Therefore, when the reactive effect of the muffler becomes invalid, iMPP can be used as an alternative further to improve the TL from low frequency to medium frequency.

Research on hydrodynamic characteristics of circular aquaculture tank based on PIV technology

The diameter-depth ratio of the water inlet pipe in the aquaculture tank (the ratio of the diameter of the aquaculture tank to the water depth, D/H) and the setting angle of the water inlet pipe (the acute angle formed by the water outlet direction and the tangent to the tank wall, α) are important factors that affect the hydrodynamic characteristics of the tank and directly affect the circulation. The comprehensive performance of the aquaculture system, in order to study the influence of the diameter-depth ratio of the aquaculture tank and the setting angle of the inlet pipe on the flow field of the aquaculture tank, this paper uses the particle image velocimetry (PIV) to measure the effect of different diameter-depth ratios and the setting angle of the inlet pipe on the circular shape. Hydrodynamic characteristics of circulating water aquaculture tanks. The test selects the single-pipe water intake mode commonly used in actual production for the circular aquaculture tank as the research object, and selects three groups of commonly used D/H conditions (3:1, 4:1, 5:1), Set up 8 groups of inlet pipe setting angles for each group of D/H conditions. In the experiment, the PIV technology was used to measure the flow field of the water layer 1 cm from the bottom of the tank under different working conditions, and the hydrodynamic characteristics of the culture tank were quantitatively analyzed through 2 aspects: the average flow velocity v avg and the velocity uniformity coefficient DU 50.The comprehensive test results show that the D/H and the setting angle of the inlet pipe obviously affect the flow field and hydrodynamic characteristics of the aquaculture tank. With the increase of the D/H, the v avg in the aquaculture tank gradually decreases, and the DU 50 gradually decreases. The changing trends of the hydrodynamic characteristics of the aquaculture tank with the setting angle of the inlet pipe under different D/H conditions are similar. When the water inlet pipe is set at an angle of 50°∼60°, the sewage collection and hydrodynamic characteristics in the aquaculture tank are optimal. The research results in this paper can provide a reference for the setting method of the inlet pipe of the circular aquaculture tank for industrial circulating water.

Influence of Axial Position of Self-Circulating Casing Treatment on the Performances of a Centrifugal Pump at Low Mass Flow Conditions

Centrifugal pumps often deviate from its design condi-tion during its operation and work at low mass flow conditions. Under such circumstances, unstable flow phenomena may be generated, affecting the efficient and stable operation of pumps. In this paper, a self-circulating casing treatment in U-tube shape is employed on a centrifugal pump to study its effects on the pump’s performance by computational and experi-mental studies. CFD results show that as the flow rate decreases, the back-flow in the inlet pipe of the studied pump without casing treatment increases in intensity and spreads over an growing distance, interfering with the main flow. CFD results also reveal that the casing treatment has a sucking function to the back-flow due to the blade loading of the pump, and when the inlet bleed of the U-tube is placed above (in front of) the leading edge of the blades, the sucking is the strongest, and the control of the back-flow and the improvement to the head coefficient under low mass flow conditions is the best, as the vortex blockage caused by the sucked back-flow in the U-tube is the smallest; when the bleed is under (after) the leading edge of the blades, the effect of the casing treatment is the second best; and when the bleed is across the leading edge of the blades, the blockage in the U-tube is most severe, and the sucking function is the weakest, so there is little improvement to the back-flow and head coefficient. Finally, the relia-bility of this study was demonstrated employing an open pump experimental system with the original pump and the same pump with the casing treatment whose bleed is located above the leading edge of the impeller.

Numerical study on heat transfer efficiency for borehole heat exchangers in Linqu County, Shandong Province, China

Developing shallow geothermal energy with borehole heat exchangers helps energy supply and CO2 emission reduction. This paper comprehensively investigates the influencing factors on heat transfer efficiency of a single borehole heat exchanger based on the field investigations in Linqu County, Shandong Province, China. We built a three-dimensional numerical model validated by a thermal response test. We systemically investigated the influence of groundwater seepage, circulating water flow rate, pipes spacing and length, the operation interval, and the annual operation mode on the heat transfer efficiency. The results show that the heat transfer efficiency decreases with long-term operation due to surrounding soil’s cold/heat accumulation. The groundwater seepage increases the heat transfer efficiency. The heat transfer efficiency increases with the pipe length, inlet and outlet pipes spacing, and operation interval. It decreases with the circulating water flow rate. The annual operation mode is of greatest importance in the heat transfer efficiency among the studied influencing factors. Compared to working only in winter, the average heat transfer efficiency coefficient increased by 0.152 when working in winter and summer. The results provide a reference for the practical installation and optimization of the borehole heat exchanger for sustainable utilization of shallow geothermal energy.

Analysis of Cylindrical Damper Effects on Turbine Meters Accuracy in a Pulsating CNG Suction Line: An Optimal Design through CFD Simulations

Turbine meters are used in compressed natural gas (CNG) stations in abundance to measure the volumetric flow rate of the inlet gas. These types of meters are very sensitive to oscillating and pulsating flows. When the station’s reciprocating compressor starts to work, due to the piston and valve performance, pulsating flow will create in the suction line and downstream of turbine meter. This pulsation makes false pulses in the meter and finally makes difference between the measured gas flow from the metering of the gas company and the amount of gas that has been sold at the station. In this study, numerical simulation of dampeners has been investigated after turbine meter and before entering gas to compressor. The goal is eliminating or reducing the effects of operating compressor in CNG station on turbine meter and reducing measurement errors. Numerical simulation of dampener was investigated by Ansys-Fluent CFD software for a CNG station with the gas inlet pressure 250 psi, inlet and outlet pipe diameter of 2 inches. In this study, several parameters such as (1) height-to-diameter ratio in the cylinder, (2) distance between dampener and compressor, and (3) volume-to-minimum volume ratio according to API 618, have been checked. The numerical results show that by increasing height-to-diameter ratio up to 3, the pulsating amplitude on Plane 1 will be reduced, and this is the best ratio according to the present results. Also, by increasing the outlet pipe length, the pressure pulsation amplitude decreases from 3.4% of pressure line in 2 m length to 0.7% in 5 m length. Moreover, the results showed 2.4% increase and 1.9% decrease in the maximum and minimum pressure for CV = 1 and CV = 16.7, respectively. Comparing fluent numerical method with previous studies shows less than 2% difference that demonstrates the validity and reliability of present investigation.

The Design and Technical Performance of Two Aeroponic Systems in Ghana

Climate change and its associated variabilities is having major impacts on agricultural production across the globe. Sustainable production options that reduce the vulnerability of the food system to climate change impacts are being advocated for, with a lot of ongoing research in that direction. Aeroponics production, a soilless production system has been identified as a sustainable system that can produce food with less input (land per unit area, water, nutrient and energy). It also makes for an environmentally friendly production system. In areas of extreme soil degradation and limited land area and water, aeroponics have shown great advantages over geoponics and sustained production, thus improving on food security. The central and northern parts of Ghana where yams are predominantly grown, is challenged with access to fertile lands, rainfall variabilities and other associated threat such as pest and disease outbreaks and seasonal bush fires. The production of seed yam, which form about 25% of the production cost for yam cultivation is hampered by all these challenges. To abate these challenges and improve on the adaptation measures taken by farmers around the region, two aeroponic systems were developed in this research, to be used for the production of seed yams propagated from vine cuttings. Two designs were made: one power independent (the gravity-fed open loop system) and the other power dependent (pressurised close loop system). In the systems design, the following aspects were taken into consideration: selection of head control and emitter; design of laterals and pipe sizes (inlet and outlet pipes); and the selection of growth chamber and feed tank. Apart from the selection of the growth chamber and the design of laterals and outlet pipe, different design considerations were also taken into account for the gravity fed system. This included the selection of drip lines and emitter flow rate. Technical evaluation of the aeroponics systems were done to ascertain its effectiveness as a fertigation system based on the performance indicators for a sprinkler and drip irrigation system. Results from the technical evaluation gave a mister discharge for the power dependent system ranging from 59.00-60.5 kPa. The emitter flow rate, the equivalent evaluation parameter for the power independent system also ranges from 0.10-0.12 L/h. There was a linear correlation between the mister operating pressure, mister discharge and swath diameter for the power-dependent system. For a Christensen’s Coefficient of Uniformity (CU) and Distribution Uniformity (DU) values of 97.52% and 96.16% respectively, the power dependent system can be said to be very efficient in its operations. The same could be said for the power independent system having a CU and DU of 94.49% and 90.80% respectively. These two developed systems have shown their capability to be adopted for u se in seed yam production to reduce some of the associated challenges, especially, access to land, water, seasonal bush fires and pest and disease outbreaks.

Study on the Influence of the Construction of Inlet and Outlet Pipe Jacking Channel Close to the Existing Pipeline

Study on the Influence of the Construction of Inlet and Outlet Pipe Jacking Channel Close to the Existing Pipeline

Numerical study on the influence of pre-swirl angle on internal flow characteristics of centrifugal pumps

The effect of inlet pre-swirl on the performance of a centrifugal pump is studied by numerical simulation. The governing equations are Navier–Stokes equations and the shear stress transport k–ω turbulence model. The numerical results show that the optimal operating point moves from the low flow region to the high flow region as the pre-swirl angle shifts from positive to negative. It is found by contours of Omega–Liutex that the positive pre-swirl angle is able to weaken the vortex on the blade suction and reduce the energy dissipation. On both the 0.5Q0 and 1.2Q0 operating conditions, the proportion of entropy production loss in the impeller and volute is about 60% and 30%, respectively. As the pre-swirl angle changes from negative to positive, the entropy production loss in the inlet and outlet pipes increases slowly, and the entropy production loss in the volute and impeller shows a decreasing trend and the peak area of entropy loss moves toward the outlet. Under the four pre-swirl angles, the main frequency is always the passing frequency of the blade. The pre-swirl angle affects the pressure fluctuation at the main frequency but has little effect at the secondary frequency. The change in velocity pulsation amplitude in the impeller in the positive pre-swirl angle is smaller than that in the negative pre-swirl angle. As a result, for the positive pre-swirl angle, the turbulent kinetic energy density in the impeller is low, and the energy loss is low, compared with negative pre-swirl. Under the low flow condition (0.5Q0), the change in velocity pulsation amplitude in the inertial range of the energy spectrum under negative pre-swirl is greater than that under positive pre-swirl.

증기터빈 습분유입에 의한 전기출력 변화 고찰

증기터빈 발전소에서 부분분사로 운전되는 고압터빈 제어계통의 터빈 조절밸브 후단 배수밸브의 고장은 터빈 입구로 유입되는 습분 입자량과 밸브 후단 파이프 내 계통증기의 응축을 발생시킬 수 있다. 최근 증기터빈 발전소에서 부분분사 조절밸브에 따라 마지막 밸브가 열릴 때 약 36 ㎿e의 전기출력이 감소하였는데, 이는 응축수가 유입되며 터빈 입구의 습분을 증가시키고 계통증기의 엔탈피를 낮춘 것이 주요 원인으로 추정되었다. 본 논문에서는 배수밸브 고장에 따른 습분증가와 전기출력 감소 간 연관성 및 전기출력 감소량에 상응하는 유입 응축수 체적에 대해 연구하였다.

Ansys fluent; CFD; PCRD; simulation; sago starch

The mini-scale pneumatic conveying ring dryer (PCRD) type sago starch dryer with a capacity of 80 kg / day has been applied to the processing of sago starch to produce dry sago starch. To increase the production capacity of the PCRD dryer, a recirculation pipe was modified. The modified pipe section is the venturi pipe diameter and the upriser vertical pipe increased. The diameter of the vertical upriser pipe is 2.5 times larger than that of the ubend pipe and the downcomer vertical pipe so that a buffer is formed. In addition, the difference in the diameter of the recirculation pipe can increase the residence time of the material. The purpose of this study was to simulate using ansys fluent to determine the temperature profile, air flow velocity, and pressure in the pneumatic conveying ring dryer (PCRD) type sago starch dryer pipe with a capacity of 1 ton per day. Simulations were carried out using the Computational Fluid Dynamics (CFD) technique using ansys fluent software package. The simulation results show that the temperature along the pipe has decreased by about 2oC at various variations of the input air velocity and variations in the outlet at the boundary conditions. Likewise, the air velocity at the end of the outlet pipe (vertical downcomer pipe) increases due to the difference in diameter with the inlet pipe. The pressure on the vertical upriser pipe is higher than the pressure on the ubend pipe and downcomer vertical pipe. The simulation results show that the recirculation pipe design is very well used so that it can be continued for the manufacture of PCRD-type sago starch dryer on a scale of 1 ton per day.

Numerical Simulation on the Structural Design of a Multi-Pore Water Diffuser during the External Ice Melting Process of an Ice Storage System

A water diffuser is a critical auxiliary equipment for an ice storage system during the external ice melting process. This paper proposes a linear multi-pore water diffuser for an ice storage system with 500 t of refrigeration capacity to enhance the performance of external ice melting. By establishing a three-dimensional two-phase volume of fluid (VOF) model, different structural designs of water diffusers for the ice storage device are numerically examined regarding the degree of turbulence, flow velocity, and pressure drop. The results show that the optimal water diffuser with five rows of trunk pipe and six perforated pores arranged in per row of branch pipe with a 4 mm diameter of perforated pores exhibiting a relatively lower degree of turbulence with a lower pressure drop compared with the other designs in this study. Meanwhile, the influence of the flow velocity on the ice melting process is also investigated by a numerical model of ice melting. It is found that the fed flow velocity from the main pipe inlet exhibits a great impact on the external ice melting process. Compared with the external ice melting process without the water diffuser, the external ice melting process with optimal water diffuser design under flow velocity of 1.0 m s−1 could shorten the overall ice-melting time by 16 h. Additionally, through adjusting the water flow velocity, different output cooling can be realized to provide a fast response speed to the cooling variations in demand of the terminal users with a reduced cost.

Optimization Simulation of Ultrafine Dry Powder Blow-Assisted Pipe Based on CFD

With the increase of fire in high-rise buildings in recent years, the demand for high-performance Water Tower Fire Truck (WTFT) is increasing day by day. In order to improve the injection capacity of ultrafine dry powder of the WTFT, this article adopts the way of adding blow-assisted pipe to realize nitrogen-assisted blowing, and the internal flow field of existing blow-assisted pipe was analyzed and optimized by CFD simulation. The influence law of size parameters on the mass flow rate and velocity of ultrafine dry powder and nitrogen was analyzed and summarized under different inlet pressure conditions. The optimization result is that the diameter of the nitrogen-assisted blowing pipe is increased between 10 mm and 20 mm, the diameter of the outlet pipe is 32 mm, and the diameter of the inlet of the mixing pipe is 90 mm.

Multiphase Flows in Plate and Shell Heat Exchangers

Abstract Air–water and air–water–oil flows were analyzed in a complex channel prototype of a plate and shell heat exchanger (PSHE) with the aid of a fast camera. Air–water flows were characterized before the PSHE inlet port by electrical capacitance tomography (ECT). The effects of inlet pipe flow pattern (bubbly, stratified, or slug) and flow direction (upward or downward) on PSHE air–water flows were investigated. The resultant phase distribution within the PSHE channel was determined by imaging analysis. Instantaneous velocity fields projected on the channel frontal plane were obtained with particle image velocimetry (PIV) for the dispersed phase of bubbly flows. Stratified pipe flow pattern results in PSHE channel segregated flow. The thermal analysis of segregated flow patterns occurring in the hot and cold sides of a PSHE reveals that the countercurrent configuration may present worse heat transfer performance than the parallel one. PSHE multiphase flows are characterized by breakup phenomenon: the mixture among phases is intensified even if stratification occurs at the inlet port. Oil–water–air downward flows are characterized by oil–water emulsion at the channel center and by water and air–water streams at the channel external part. Oil–water–air upward flows are characterized by air–water and oil–water emulsions at the channel center and by the water stream at the channel external part.

Comparative Study of Inlet Structure and Obstacle Plate Designs Affecting the Temperature Stratification Characteristics

Temperature stratification between outgoing hot water and incoming cold water is a key factor in diminishing energy loss during the discharging process and maximizing the useful hot water delivered from the tank or enhancing the thermal efficiency of the heating device during the heating process. In this study, the inlet structure and the obstacle plate were designed and modified based on two main factors, the reduction of inlet water velocity and the stipulation of the water recirculation area, to develop temperature stratification through the computational fluid dynamics method. The simulation model’s accuracy was validated against the experimental results. The results showed that using the equalizer as an inlet pipe’s auxiliary device was the best approach for decreasing the inlet water velocity, which resulted in enhancing temperature stratification. The discharging efficiency improved from 77.3% for the original tank model to 86.1% for the tank with equalizer IV model, which meant an additional 45 L of useful hot water was gained from the good temperature stratification storage tank. The installation of the obstacle plate for controlling the turbulence zone could not improve temperature stratification significantly, which resulted in an increase in discharging efficiency by only 4% more than the original tank model.

Stress and Pressure Pulsation Analysis of Low Temperature Compressor Piping System in LNG Vaporizing Station

LNG (Liquefied Natural Gas) vaporizing stations are usually built in the cities and towns, and the BOG (Boiled Off Gas) pressurizing system is a very important element. In the pressurizing system, the severe vibration of the low-temperature reciprocating compressor may lead to a failure of the pipeline system and the equipment. Therefore, this paper analyzes the stress and pressure pulsation of the BOG compressor piping system in the LNG vaporizing station. The beam model was used to establish the pipe model. The static, harmonic and modal analysis were carried out based on the plane-wave theory and the pressure-fluctuation theory, and the influence factors of support spacing, the settlement of the fulcrum foundation, pipe pressure and elbow angle were analyzed. The main conclusions are as follows: (1) the unbalanced excited force caused by pressure pulsation greatly affects the stress of the exhaust pipe and compressor outlet pipe, and has less influence on the stress of the suction pipe and compressor inlet pipe; (2) although unbalanced excited force is generated in the elbow, it also has an impact on the straight pipe stress; (3) adding an expansion joint to the pipe of the BOG compressor can effectively reduce the stress of the pipe its the displacement, and can increase the flexibility of the pipe.

Operational performance characteristics of an axial double baffles three channels classifier for coarse pulverized coal

In order to obtain the working principle of the axial direction classifier and raise its separation efficiency, the flow field and classification performance of the classifier was investigated by numerical simulation and experimental measurement. The particle size distribution at inlet, outlet and return pipe was measured by laser particle size analyzer and coupled with Rosin-Rammler model. The particle trajectory was analyzed using the discrete phase model. The tangential velocities played a dominant role in particles radial distribution mainly in the form of Rankine vortex. The axial velocities determine the vertical distribution of particles. The velocity distributions and turbulence influence the cutting particle size and separation efficiency mostly. The most suitable condition is baffles angle of 20° and inlet velocity of 19.3 m/s considering the load of the mill and the fineness of the pulverized coal at the inlet of the classifier.