Steam Flow Rate Research Articles

Simultaneous Condensation-Evaporation Heat Transfer on A Vertical Tube, II-Theoretical Study.(Dept.M)

In the present work, simultaneous condensation-evaporation heat transfer in thin films on a vertical tube is, experimentally, investigated. Condensation takes place on the outer surface of the vertical tube and the evaporation occurs inside it. The condensed steam outside the tested tube imparts its later heat to evaporate the thin liquid film, which flows inside the tube. Throughout this work, the range of Reynolds number for water film flow is from 50 to 800, while that of condensate outside the tube, takes values less than 100. The studied operating parameters, which affect the condensation-evaporation processes are water flow rate, its degree of subcool, the flow rate of the dry saturated heating steam and its pressure. The flow rate of the falling heated water is 3-50 kg/hr at constant pressure of 1.1 bar, while the heating steam flow rate is up to 5 kg/hr at a pressure which varies from 1.2 to 2 bar. The results show that, decreasing the Reynolds number of the falling water film, up to dry out a the end of the venical tube, causes an increase of heat transfer coefficient for different operating parameters. In addition, the Nusselt number for different values of Reynolds number are calculated and in accordance, an empirical correlation for the condensation - evap oration Nusselt number as a function of the studied operating parameters is proposed.

Simultaneous Condensation-Evaporation Heat Transfer on A Vertical Tube, I- Experimental Study.(Dept.M)

In the present work, simultaneous condensation-evaporation heat transfer in thin films on a vertical tube is, experimentally, investigated. Condensation takes place on the outer surface of the vertical tube and the evaporation occurs inside it. The condensed steam outside the tested tube imparts its later heat to evaporate the thin liquid film, which flows inside the tube. Throughout this work, the range of Reynolds number for water film flow is from 50 to 800, while that of condensate outside the tube, takes values less than 100. The studied operating parameters, which affect the condensation-evaporation processes are water flow rate, its degree of subcool, the flow rate of the dry saturated heating steam and its pressure. The flow rate of the falling heated water is 3-50 kg/hr at constant pressure of 1.1 bar, while the heating steam flow rate is up to 5 kg/hr at a pressure which varies from 1.2 to 2 bar. The results show that, decreasing the Reynolds number of the falling water film, up to dry out a the end of the vertical tube, causes an increase of heat transfer coefficient for different operating parameters. In addition, the Nusselt number for different values of Reynolds number are calculated and in accordance, an empirical correlation for the condensation - evaporation Nusselt number as a function of the studied operating parameters is proposed.

Potential to retrofit existing small-scale gasifiers through steam gasification of biomass residues for hydrogen and biofuels production

This work investigates the opportunity of retrofitting existing small-scale gasifiers shifting from combined heat and power (CHP) to hydrogen and biofuels production, using steam and biomass residues (woodchips, vineyard pruning and bark). The experiments were carried out in a batch reactor at 700 °C and 800 °C and at different steam flow (SF) rates (0.04 g/min and 0.20 g/min). The composition of the producer gas is in the range of 46–70 % H2, 9–29 % CO, 12–27 % CO2, and 2–6 % CH4. A producer gas specific production factor of approx. 10 NLpg/gchar can be achieved when the lower SFs are used, which allows to provide 80 % of the hydrogen concentration required for biomethanation and MeOH synthesis. As for FT synthesis, an optimal H2/CO ratio of approx. 2 can be achieved. The results of this work provide further evidence towards the feasibility of hydrogen and biofuels generation from residual biomass through steam gasification.

Managing the energy of the air conditioning systems using a modified multi-variable control technique

This research is a continuation of our previous work [19], in which, I’ve investigated many control techniques for the multi-input multi-output (MIMO) control systems for air conditioners. In the present work, I’ve suggested another control technique which exhibited better performance in the cases where permanent disturbances are present. I’ve applied the technique to a model room that simulates a computer room and is conditioned by a simple, less expensive, and energy-saver HVAC system. The two control inputs are; the opening angle of a fresh air gate and the steam flow rate from a humidifier. The two controlled outputs are the temperature and humidity. The control technique and the in-door conditions are simulated using a written program that works along with a commercial code. The sampling interval for each controlled variable is modified to allow more accuracy for measured data. When applying accidental and permanent disturbances in both controlled variables, the suggested technique exhibited accepted performance. The controlled variables that are affected with permanent disturbances achieved their set-point values after longer time intervals than those of the cases where only accidental disturbances are present. Two comparisons were made between the controlled and uncontrolled system by operating the system for a certain period, and fixing the fresh air opening at 25% and 50% of the full opening area. The consumed energy in the two cases was compared with that of the case when applying the control technique for the same period. An energy-saving of about 15.3% was recorded in the first case and about 37.6% for the second case. The present technique is a case-independent and may be applied to any MIMO control system with little modifications.

Magnetic bio-activated carbons production using different process parameters for phosphorus removal from artificially prepared phosphorus-rich and domestic wastewater

A series of magnetic bio-activated carbon (MBAC) has been produced from lignin and ferrous salts following to the process including impregnation, carbonization, and steam activation. The influence of the impregnation methods and the steam flow rate on the quality and the maximum phosphorus adsorption capacity of the produced MBACs has been investigated. The phosphorus adsorption performance in real domestic wastewater of the MBAC with the highest maximum phosphorus adsorption capacity has been investigated. The results show that all of the produced MBACs have a relatively rich porous structure, and all surface iron species exist as magnetite (Fe3O4). Compared with the MBACs that are produced via the dry impregnation method using a lower steam flow rate, the MBACs that are produced via the wet impregnation method using a higher steam flow rate are believed to have a higher iron content and better iron species dispersion. The highest maximum phosphorus adsorption capacity of all the produced MBACs is estimated to be as high as 69.80 mg-P/g according to the best-fitting Langmuir model. The MBAC that shows the highest maximum phosphorus adsorption capacity could also remove 84.65% and 96.97% of the total phosphorus from the filtered raw domestic wastewater (FRDW) and treated domestic wastewater (TDW), respectively, which indicates a good potential for using MBACs for domestic wastewater treatment.

An integrated simulation–optimisation approach for free fatty acid removal in palm oil deodorisation process

AbstractDeodorisation is the key process to produce high‐quality refined, bleached and deodorised palm oil (RBDPO) in a palm oil refinery. In this work, an integrated simulation–optimisation approach was adopted for the analysis of a deodorisation process in an operating palm oil refinery. The process includes a deodoriser unit that removes free fatty acids (FFA) from bleached palm oil (BPO), and a vacuum scrubber utilising palm fatty acid distillate (PFAD) to reduce the FFA content entering the vacuum system. Being a proprietary technology, deodoriser is not found in the standard models of commercial simulation software. Approximation was made in simulation, with results compared to plant data. Detailed analyses showed that the reduction of FFA content relies on deodorisation temperature and pressure, stripping steam flowrate, as well as the temperature and flowrate of PFAD entering the vacuum scrubber. An optimisation model was solved to maximise profit from the deodorisation. Results showed that the FFA content entering the vacuum system is reduced significantly by 49.7%, leading to higher recovery of FFA in PFAD and lower loss into the condenser section. Applying the optimum values to the refinery has resulted in FFA levels greater than 91.2% in PFAD and RBDPO yield improvement of 0.5%.

Автоколебания и субгармонические вибрации. Часть 1. Причины возникновения низкочастотной вибрации

A brief overview, terminology and basic concepts in the field of low-frequency vibration (LFV) are given, various reasons for the loss of stability are discussed, including: - aerohydrodynamic excitation of self-oscillations of rotors from the action of aerodynamic disturbing forces in the stages and seals of turbines, - hydrodynamic excitation in an oil film of various types bearings in conditions of technological deviations, loss of stability under the action of forces of internal friction and structural damping. In comparison with previous works, significant, previously unaccounted factors affecting the LFV were introduced, including the angular coefficients of stiffness and damping of the oil film, stability parameters were introduced as functions of steam consumption. A zone of stability loss is introduced in the lower part of the ascent curve at high loads, etc. An assessment and comparison of the most important parameters affecting the occurrence of LFV are given. The features of the emergence and action of aerostatic and aerodynamic forces in the control stage of turbines with nozzle steam distribution are shown. It is noted that the disturbing aerodynamic forces in the control stage first increase with a decrease in the steam flow rate, and the total disturbing forces in the HPC are not proportional to the steam flow rate. Some other reasons for the occurrence of subharmonic LFVs are considered. The article has three objectives or goals: 1) help to understand why and how it is necessary to ensure stability of rotor systems at the design and operation stage and to prevent low-frequency vibration of various types. It is shown that for this, first of all, it is necessary to perform calculations of the complex frequencies and modes of vibration of the shafting, ensure detuning of the shafting from hazardous zones and, while varying a number of parameters, determine and ensure the stability margins in terms of the frequency of rotation and in terms of the flow rate of the working fluid; 2) for the effective creation of a subsystem for diagnostics of LFV, it is necessary to disassemble in detail the reasons for its appearance and provide for the installation of a complete system of shaft sensors. Moreover, only part of the technology is presented here; 3) to propose effective and short ways to solve the problem of low frequency energy in case of its occurrence and elimination on a specific turbine unit.

Systematic Mass and Energy Evaluation of Biomass Staged Gasification System Based on Thermodynamic and Kinetic Equilibrium Approaches

In this work, a typical three-staged gasification system was studied using Aspen Plus. Two models, namely thermodynamic and kinetic equilibrium models were built and compared. Results show that the kinetic equilibrium model could predict the syngas yield quite accurately than thermodynamic equilibrium model. Pyrolysis stage and reduction stage were endothermic, while the partial oxidation stage was exothermic. The heat load of pyrolysis and reduction stage was -17.632kW and -14.368kW. The oxidation of volatiles released large amount of heat and formed high temperature zone around 1100°C. The hot flue gas contained large amount of sensible heat that provide the heat for pyrolsis and reduction stage. Based on the energy balance calcualtion, autothermal operation could be achieved for this three-staged gasification. And extra heat in hot flue gas could be used for household heat supply. Based on the model, the influence of operation parameters, including reduction temperature, air equivalence ratio, steam flow rate and oxygen concentration on gasification performance was investigated.

Efficiency and Effectiveness Thermal Analysis of the Shell and Helical Coil Tube Heat Exchanger Used in an Aqueous Solution of Ammonium Nitrate Solubility (<i>ANSOL</i>) with 20% H <sub>2</sub>O and 80% <i>AN</i>

The case study is about obtaining the flow rate and saturation temperature of steam that makes it possible to heat a solution of water and ammonia nitrate (ANSOL) in a shell and helical coil tube heat exchanger, within a time interval, without that the crystallization of the ANSOL solution occurs. The desired production per batch of the solution is 5750 kg in 80 minutes. The analysis uses the concepts of efficiency and effectiveness to determine the heat transfer rate and temperature profiles that satisfy the imposed condition within a certain degree of safety and with the lowest possible cost in steam generation. Intermediate quantities necessary to reach the objective are the Reynolds number, Nusselt number, and global heat transfer coefficient for the shell and helical coil tube heat exchanger. Initially, the water is heated for a specified period and, subsequently, the ammonium nitrate is added to a given flow in a fixed mass flow rate.

On the rational form of rotary control diaphragms for steam turbines with industrial and cogeneration steam extraction

The Russian park of power steam turbines contains a large number of turbines with adjustable steam extraction from the flow path where rotary control diaphragms are used as flow controllers, which structurally easily fit into the flow path of these turbines. This method of regulating the steam flow rate is accompanied by a decrease in the efficiency of the subsequent stages of the turbine and causes the appearance, at reduced loads, of additional disturbing forces acting on the rotor blades. In the presented materials, a variant of a post-sampling stage with a radial rotary control diaphragm is considered. The performed mathematical modeling of the working fluid flows in such a stage showed that in this case, at all turbine loads, a relatively uniform velocity field is provided when steam enters the nozzle apparatus, which naturally entails the elimination of the noted drawbacks.

IMPROVING THE RELIABILITY OF THE FUEL OIL HEATING SYSTEM AT THE TYUMEN TETS-2

This article describes an engineering solution that allows a significant reduction in the material costs of heating reserve fuel (fuel oil) at the energy facility of the Tyumen Thermal Power Plant No. 2 (TETs 2), as well as make the heating system more reliable and less energy-intensive. Using the methods for calculating the input and output parameters of the supply pipeline and finding the surface area of the heat exchange of the coil, the authors describe the means for finding the thickness of the thermal insulation of the pipe and tank. The main equations for creating calculation methods are the heat balance equation. Using the criterion dependencies has helped in calculating the process of convective heat transfer. In addition, the authors provide the graphs for determining the steam flow rate depending on the ambient air temperature and wind speed and nomograms for determining the temperature inside the thermal insulation of the tank.

Performance research of lanthanum-loaded dolomite catalyst for pine catalytic gasification

To enhance the catalytic effect of dolomite, La/Dol catalyst was prepared by impregnation modification of dolomite with La (NO3)3 as additive. The catalyst was characterized by BET, SEM and XRD. With pine rods as raw materials and La/Dolas reforming catalysts, the effects of gasification temperature and La amount of catalysts on the catalytic gasification of pine were compared and analyzed in a self-made two-stage biomass gasification reforming experimental furnace. The results show that a small amount of La (2%) can obviously promote the forward progress of water gas reaction and perfect the catalytic reforming effect. Under the working condition of steam flow rate of 10 g/min, 2-La/Dol catalyst and reforming temperature of 750°C, with the increase of gasification temperature, the amount of H2 increases significantly, and the highest volume fraction of H2 increases from 28.51% (0-La/Dol) to 41.72% (2-La/Dol). La2O3 in the catalyst promotes the secondary cracking of tar. As a result, the tar content of liquid phase product is obviously reduced, and the number of functional groups is also reduced. La2O3 on dolomite surface occupies active sites, so carbon filaments are not suitable for accumulation and carbon deposition is inhibited. Carbonate (La2O2CO3) in the catalyst can react with carbon to slow down the carbon deposition on the surface and improve the activity and service life of the catalyst.

Fabrication of Iron-based Oxygen Carriers on Various Supports for Chemical Looping Hydrogen Generation

Fe2O3/Al2O3 and Fe2O3/TiO2/Al2O3 oxygen carriers were fabricated and evaluated for chemical looping hydrogen generation (CLHG) using a TGA system and a fixed-bed reactor. Oxygen carriers were converted to around 33% in a fixed-bed reactor to ensure uniform reduction. The reduced oxygen carrier was tested for steam generation, where in all cases Fe2O3/Al2O3 displayed a better conversion than Fe2O3/TiO2/Al2O3. It was found that increasing the reaction temperature from 800 to 850 °C had little effect for either oxygen carrier, but a further increase to 900°C resulted in an increased steam conversion. A higher steam flow rate caused a lower overall steam conversion but a higher H2 production. A higher feed rate of reduced oxygen carrier let to a higher steam conversion up to a rate of 18.4 and 14.9 g min–1 for Fe2O3/Al2O3 and Fe2O3/TiO2/Al2O3, respectively. A final comparison was performed with up to 50 redox cycles, where Fe2O3/Al2O3 showed superior reactivity in the first cycles but ended at a conversion of 54.6% with Fe2O3/TiO2/Al2O3 ending at a conversion of 64.6%.

Optimization and Experimentation of Modified Throttling Calorimeter

Steam plays a vital role in the industrial revolution and is a major source of power generation in steam engines or steam turbine. Thus, it becomes necessary to maintain steam as dry as possible and it is necessary to monitor steam quality on a regular basis. The most commonly used method in determining steam quality is Throttling calorimeter. Here existing throttling calorimeter is designed for determining steam quality within a pressure range of 20 – 25 bar. This existing calorimeter is optimized for monitoring steam quality within a range of 4 – 12 bar gauge pressure. Pipe and orifice dimension of the calorimeter is calculated for a given flow rate of steam by using ISO norms and Bernoulli’s principle. After conducting multiple trials on newly designed model test rig it is found that the 4 mm orifice diameter model gives the greater consistency of results and it is considered to be an optimized model.

Investigation of the equalization capability of submerged perforated sheets forWWER-1500 horizontal steam generator

Non-uniform heat transfer occurs at the steam generator secondary side, thus inducing a non-uniform steam generation and a non-uniform steam flow rate along the evaporation surface. In order to equalize the steam flow rate, submerged perforated sheet is installed in the horizontal SGs An analysis of the equalization of the non-uniform steam load in the WWER-1500 horizontal steam generator is performed using the STEG calculation code. Variant calculations of various options for the perforation of sheets allowed us to determine the design of submerged perforated sheet, which very well equalizes the initially non-uniform steam load.

Steam Pressure’s Influence in the Condenser on the Efficiency Indicators of the T-100-12.8 Turbine When Operating with a Fully Closed Diaphragm According to the Thermal Diagram

On the example of the T-100-12.8 turbine, it is shown that its efficiency in winter (with a fully closed diaphragm) is significantly influenced by the state of the vacuum system and ejectors. An analysis of the effect of the vacuum in the condenser on the efficiency of the cogeneration turbine with a completely closed cogeneration diaphragm and the operation of the turbine according to the thermal schedule when the steam flow rate in the low-pressure part does not exceed 60 t/h is presented. In this case, the pressure in the condenser depends on the tightness of the turbine vacuum system, the state of the ejectors, and the water temperature at the inlet to the condenser and is determined by the characteristics of the ejector. With a completely closed cogeneration diaphragm, the pressure in the condenser does not depend on the steam and circulating water consumption nor, within certain limits, on the state of the heat exchange surface (tube fouling). The change in the turbine capacity in modes with a fully closed diaphragm depends on the deviation of the condenser vacuum from the standard value nonlinearly. At low steam pressure (low temperature of the circulating water at the inlet to the condenser), the power change is more significant than at increased pressure. Power losses increase with an increase in the steam pressure in the lower heating extraction, a decrease in the temperature of the circulating water, and an increase in air inleakage into the condenser. With the diaphragm fully closed, the standard pressure in the condenser is maintained by one ejector if the air inleakage does not exceed the standard value of 15 kg/h. When two ejectors are switched on, the standard vacuum in the condenser in this case can be maintained if the air inleakage is less than 25 kg/h. When the steam consumption in the LPP is more than 80 t/h, the change in the turbine power becomes proportional to the change in the steam pressure in the condenser.

The research on the dynamics of the three-impulse system of automatic control of water supply to the steam generator when the load changes

The paper analyses an operation of the typical three-impulse automatic control system (ACS) of the steam generator water supply. A mathematical model has been developed to test its operability for load shedding, allowing you to set maximum deviations of the water level without full-scale tests, without adjusting the operation settings technological protections by the level of water in the drum. Reasons identified static regulation errors when working out internal and external disturbances in the flow rate of superheated steam in a typical ACS. The relevance of modernization of a typical ACS power supply to the steam generator water. Altogether, under all influences, a significant improvement in the quality of regulation was obtained compared to a typical three-impulse automatic power control system. The relevance of modernization of a typical system of automatic control of water supply of a steam generator to eliminate static regulation errors in a wide range of changes loads.

An experimental study of the integral characteristics of the intrachannel liquid film suction in a turbine stator blades cascade

This paper presents the results of an experimental study of the integral characteristics of the intrachannel liquid film suction in a flat cascade of turbine stator blades. Two slots for removing the liquid film from the interblade channel were arranged on the pressure surface of the stator blade. The experiments were carried out with initial steam wetness y 0 = 3 ÷ 9.5 % and theoretical Mach number downstream the cascade M lt = 0.6 ÷ 0.78. The operation mode of the moisture removal system was determined by the relative pressure drop on the moisture-removing slots and varied over a wide range. The investigations were carried out for both the operation of the moisture-removing slots one at a time and the combined suction of the liquid film simultaneously through both slots. The measurement system used in the experiments allowed separately determining the mass flow rates of steam and liquid removed from the interblade channel. The obtained integral characteristics served to evaluate the influence of various factors on the efficiency of the intrachannel moisture removal system. Based on the analysis of the research results, recommendations on the design and operation of intrachannel moisture removal systems have been formulated.

Effects of superheated steam on combustion instability and NOx emissions in a model lean premixed gas turbine combustor

This study experimentally explored the effects of preheated steam on combustion instabilities and NOx emissions in a lean-premixed model gas turbine combustor. Three variables were investigated to confirm the effectiveness of preheated steam injection on combustion instability and NOx emissions—the steam flow rate, the injection heights and the inner diameter of injectors. Experimental results denote that optimal the damping ratio of sound pressure can reach 91.73% with preheated steam dilution, the amplitude of sound pressure reduced from 46 Pa to 3.8 Pa. The optimal damping ratio of NOx emissions can reach 83.74% with preheated steam dilution, concentration of NOx emissions reduced from 24.6 ppm to 4.0 ppm. Mode shifting of thermoacoustic instability is appeared as the inner diameter of the injector varied from 1.5 mm to 4.0 mm. The oscillation frequency of the flame CH* chemiluminescence suddenly drops from 256 Hz to 74 Hz as the inner diameter changes from 2.0 mm to 2.5 mm. The lower the relative height of the superheated steam injectors, the better the control effect of combustion instability and NOx emission. However, unreasonable design of the steam injector will trigger thermoacoustic instability. The flame roots, fronts and recirculation zones are all changed under preheated steam, the whole flame become short and compact. The flame length reduced from 75 mm to 37 mm while the preheated steam flow increases. This study explored the dilution effects of preheated steam on lean premixed combustion instability and NOx emissions, the results could be conducive to the design of clean, safe and high-efficient gas turbine combustors.

Effect of water level on performance of swirl-vane separator and steam dryer in PWR SG

Swirl-vane separator and steam dryer work as primary and secondary separator in PWR SG to supply the dry-saturation steam for the turbines to generate electricity. In this paper, steam-water two-phase experiment is conducted to investigate the effect of water level on the separation efficiency, moisture carryover (MCO) and pressure drop of swirl-vane separator and steam dryer, respectively. The operation pressure is 6 MPa and the mass flowrate of steam and water are 3.81–11.73 kg/s and 7.62–70.40 kg/s, corresponding to 50–154% full power and 3–7 circulation ratio under prototypical conditions. For swirl-vane separator, the results indicate that the separation efficiency decreases (or MCO increases) with power load and circulation ratio at normal-water level, while it decreases more significantly with power load and the dependence on circulation ratio becomes complex at high-water level. The separator pressure drop increases with power load and circulation ratio increasing, but the influence of water level is minor. In terms of steam dryer, at both normal and high-water level, the separation efficiency and MCO exhibit minor change with power load and circulation ratio below the critical load (e.g. 120%–140%). Otherwise, MCO increases (or separation efficiency decreases) rapidly with power load and circulation ratio, and its value changes from 0.1% to 1.9% at normal-water level and from 1.0% to 22.4% at high-water level. The dryer pressure drop increases with power load while the influence of circulation ratio and water level is minor. Overall, the high-water level deteriorates the separation efficiency but has little influence on pressure drop of steam separator package in nuclear SG.