Wet Steam Research Articles

A visual mass transfer study in the ejector considering phase change for multi-effect distillation with thermal vapour compression (MED-TVC) desalination system

The multi-effect distillation with thermal vapour compression (TVC) seawater desalination system provides an excellent energy-saving scheme by escalating the low-level energy. The internal mass and heat transfer in ejectors is an important element to improve efficiency. In this study, a visual mass transfer simulation model considering real thermodynamic properties is used to observe the inner-mixing process. The assessment is from the perspective of visible mixing layer growth and the effect on entrainment ratio. As shown in the mass percentage distribution graph, there is an inescapable phase change on mixing layer boundary, where the wetness of wet steam can reach to 16.0%. Meanwhile, the mixing layer length predicted by dry model is 25.1% higher than wet model. The condensation weakens the mixing process and leads to shorter length. Under subcritical mode, the cross-sectional area of the entrained flow is deducted and the mixing layer cannot develop completely. The critical pressure range predicted without condensation is 18.5% lower, which causes a misjudgment in entrainment ratio because overvaluing the influence of outlet pressure on entrained flow. Thus, mass transfer during development of the two-phase mixing layer has great impact for MED-TVC system.

Numerical investigation of roughness effect on wet steam ejector performance in the refrigeration cycle

Numerical investigation of roughness effect on wet steam ejector performance in the refrigeration cycle

Desain dan Pabrikasi Alat Ukur Suhu dan Kelembaban Berbasis Modul Mikrokontroler ATMega 16A-PU

Research on design and fabrication of temperature and humidity measuring devices based on the ATMega 16A-PU microcontroller module can be realized directly on the FFB heating system. Temperature and humidity measuring devices consist of DC power supply, voltage follower, SHT11 sensor module, LM35 Waterproof sensor, 20x4 character LCD and ATMega 16A-PU microcontroller module. Whereas the FFB heating system consists of steam, boiler, air control room, and chamber. The system can be realized by placing the LM35 Waterproof sensor inside the air control room and the SHT11 sensor module inside the chamber. This system is also equipped with data acquisition software using the Delphi 7.0 program to display measured data in real-time and save it to Excel and the database. Tests carried out by flowing using wet steam generated from the boiler into the air control room and chamber. The average error value of reading the standard gauge with a gauge that has been made for the LM35 Waterproof sensor with a measurement range of 20-90ºC is 1.22ºC. As for the SHT11 sensor module, the average error value of readings with a measurement range of 20-90ºC and 40-90% is 1.04°C and 4.04%

Experimental validation of sonic speed theory for wet steam

In order to obtain the sonic speed of the wet steam under different thermal conditions, and verify the accuracy and the precision of Petr’s wet steam sonic theory, experimental measurements were carried out. Also, the effects of acoustic frequency, pressure, wetness, and droplet size on the sonic speed of wet steam were studied based on Petr’s wet steam sonic theory. Results indicate that deviations between the experimental results and Petr’s wet steam sonic theory is in the range of −4%–4%, which is within the experimental measurement error of ±5%. The variation range of the ratio of the actual sonic speed a to the frozen speed af is 0.89–1. When the sonic speed ratio ( a/ af) is close to 1, it means that the sonic speed of wet steam is close to the frozen speed, and the faster the sound wave propagates in the wet steam. In the acoustic frequency range of 102–105 Hz, the sonic speed of wet steam increases with increase of acoustic frequency, pressure, and water droplet size, and decreases with increasing wetness.

Optimization of the Trailing Edge Inclination of Wet Steam Turbine Stator Blade Towards the Losses Reduction

Optimization of the Trailing Edge Inclination of Wet Steam Turbine Stator Blade Towards the Losses Reduction

Numerical modeling of droplets injection in the secondary flow of the wet steam ejector in the refrigeration cycle

Steam ejector plays a key role in the refrigeration system. The water has been used as a working fluid because water is more economical and non-toxic. The operating fluid often enters the evaporator as a water liquid and droplets evaporate by absorbing heat. Cooling load changing causes the vapor in the outlet of the evaporator to be accompanied by droplets. Therefore, there are droplets at the inlet of secondary nozzle and flow should be simulated as a wet steam flow with injection droplets at the secondary flow. In this paper, the effects of droplets injection at secondary flow have been investigated on the performance of the refrigeration cycle. For this purpose, the Eulerian-Eulerian method has been used and the results have been validated with experimental data. Six cases are considered with different wetness and number of droplets in the secondary flow. The results of case 6 show COP, T¯outlet, and ER decrease about 22.93%, 15.66%, and 22.93%, respectively. In addition, the steam accompanies by droplets at the outlet of ejector. Therefore, it is essential for designers and operators to model and consider the effects of the droplets on the wall erosion to optimize the wet steam ejector and refrigeration cycle performance.

Perbandingan Efisiensi Penggunaan Bahan Bakar Antara Arang Kayu dan Gas LPG Pada PLTU Tekanan Rendah

Sources of electrical energy is a basic need in life, both in industry and the necessities of life. Along with the depletion of fossil energy, it is necessary to develop a biomass energy source as a fuel for electrical energy. For this reason, this study aims to create innovative power plants using biomass energy as fuel. The steam turbine is a prime mover that converts the potential energy of steam into kinetic energy and then converts it into mechanical energy in the form of a turbine shaft rotation, directly or with the help of a reduction gear, connected to the mechanism to be driven. In a study to analyze the performance of a steam turbine with gas fuel and wood charcoal. Wood charcoal is activated carbon from combustion, which in this study uses wet steam to drive the shaft with variations in pressure (7Bar, 6Bar, 5Bar and 4Bar). From the results of the study, the maximum power produced by a laboratory-scale steam turbine is 20.84 Watt at a given pressure of 7 Bar and the maximum efficiency of a laboratory-scale steam turbine with wood charcoal fuel is 70.02% with a pressure of 7 Bar and Generator efficiency is 21.87%. or 17.5 Watts, the electrical power generated from the speaker power generator is 80 Watts. For the results of the comparison of the performance of the steam turbine with wood charcoal fuel media with LPG gas, it can be proven from the turbine efficiency it is better to use gas fuel with a different ratio (at a pressure of 7 bar Wood Charcoal / LPG): 70.02%/78, 12%), while the efficiency of the generator is at a pressure of 7.Bar (21.87, 25%), so LPG fuel is more effective than wood charcoal but from local fuel Wood charcoal is more readily available and cheaper.

Handling of Correction of Indicated Value of Wet Steam Flow Measurement and Its Relation to Standards

In general, it is practically difficult to separate the gas and liquid phases of a steam flowmeter for simultaneous measurement, given its measurement principle. Therefore, based on our past research activities and results, we have reorganized the steam flow rate value for the gas phase, which contributes to understanding the amount of useful heat energy, by making useful corrections to the flow rate indication value when measuring wet steam in which the gas and liquid phases are mixed. In addition, the relationship with related international standards is discussed, and future prospects are discussed.

Relationship between mass flow rate and enthalpy in wet steam flow for various steam flowmeters

In industrial fields, as the steam is commonly utilized for heat supply, drying process and so on, it is important to be aware of the steam flow rate in the view point of energy management. However, the steam utilized in the factory is usually wet steam condition. Though it is well known that the wetness affects the flowmeter reading, it is difficult to clarify the effects of the wetness in the steam flow quantitatively in actual plants and factories, and thus far, there has been no established method for estimating the error caused by the wetness of steam flow. Therefore, we have started to investigate the effect of the wetness to the steam flow meters.

Flow Pattern Recognition Based on the Received Waveforms of a Clamp-on Ultrasonic Flowmeter for Wet Steam Flows

Clamp-on ultrasonic flowmeter is a powerful tool for measuring flow rate in an existing pipe. However, measuring flow rate of wet steam flow has not been established yet. It is important to investigate the various error factors caused by the wetness fraction. Based on our previous investigations, it was clarified that the error of the flow rates tends to increase with the wetness fraction because of the changes in the velocity distribution in the wet steam and the effect of the liquid holdup. Therefore, it is important to estimate the flow regime of the wet-steam flow in the pipe. This study proposed a flow pattern recognition method using a machine learning based on the guided wave that is the propagated ultrasound through the pipe wall. The guided wave changes depending on the flow regime due to the fluctuations at the liquid-gas interface. Using the received ultrasonic signals of the guided wave in stratified flow, annular mist flow, and transition between them were used as the teaching data, and the other conditions were tested for the flow pattern recognition. Flow patterns were accurately predicted in adiabatic air-liquid two-phase and wet-steam flows in horizontal pipes. Furthermore, it was shown that the selection of the guided wave region is important to predict the flow pattern in various pressure conditions using the same teaching data.

The comprehensive analysis of the relationship between the latent heat, entrainment ratio, and ejector performance under different superheating degree conditions considering the non-equilibrium condensation

• Main difference between wet steam & ideal gas models is two phase heat transfer. • The relationship of two phase heat transfer with ejector performance is studied. • The total two-phase heat transfer & entrainment ratio have an inverse relationship. • On-design and off-design regions became smaller by increasing superheating. Low-grade thermal energy can be used for superheating the working fluid in the steam ejector. The purpose of the present study is to investigate the relationship of two-phase heat transfer with the ejector performance in the condensing flow regime under the condition of primary steam superheating. The condensation and evaporation phenomena occur in two-phase ejectors. The heat and mass transfer between the liquid and vapor phases change the flow pattern inside the ejector. The results show that the wet steam model has better fitting with experimental data than the ideal gas model. The primary steam superheating influences on the intensity of shock-wave patterns of supersonic flow, liquid mass fraction and two-phase heat transfer in the ejector. By increasing the superheating level, the two-phase heat transfer and exergy destruction are decreased, entrainment ratio in the wet steam model gets closer to entrainment ratio in ideal gas model, critical and limiting pressure are decreased and on-design and off-design regions become smaller. Also the effects of primary steam superheating in the ejector are investigated on the performance of a renewable refrigeration cycle. Superheating the working fluid reduces the generator energy consumption and increases exergy destruction in a refrigeration cycle. At degree of superheating 100 K, two-phase latent heat, energy consumption, and ejector exergy destruction decrease by 40%, 3.9%, and 11.7%, respectively, and entrainment ratio and total exergy destruction increase by 10% and 50%, respectively.

Анализ влияния факторов неопределенности на математическое моделирование процесса обратного расширения аммиака в тихоходной поршневой компрессорной ступени. Часть 1

The paper presents an analysis of the influence on the mathematical modeling of the process of reverse expansion of ammonia in the area of wet steam, implemented in the working chamber of the reciprocating compressor stage, of such uncertainty factors as the method for calculating the heat transfer coefficient, the surface temperature of the wall of the working chamber and the degree of dryness at the beginning of the process of reverse expansion. The mathematical model is based on the equations of the first law of thermodynamics for a body of variable mass, the equation of state of a real gas, the Clausius– Clausius and Newton–Richmann equations. The results of the calculation showed that the instantaneous values of the pressure and temperature of ammonia, as well as its degree of dryness during reverse expansion in the wet steam region, significantly depend on the chosen method for calculating the heat transfer coefficient. The process under consideration is also significantly influenced by the temperature of the walls of the compressor working chamber, in which the compression process is implemented, and the degree of dryness of ammonia at the beginning of the expansion process.

Final activity report of the “Workshop of Advanced Studies for Steam Flow Measurement”

The "Workshop of Advancement of Steam Flow Measurement" started its activities in April 2017 within the Power and Energy Systems Division of the JSME and finished as planned in March 2022. The industrial sector has a steam demand of 1.12 million TJ/year, which is the second largest energy source after electricity, and steam accounts for about 80% of the heat energy use in the industrial sector and is widely used in large quantities in the main production processes: sterilization, drying, cleaning and distillation. Steam is thus a major heat source in the industrial sector and there is a strong need for flow measurement from the perspective of energy conservation. However, flow measurement of steam is very difficult due to its high temperature and susceptibility to wetness. In addition, there are very few measurement standards. Therefore, the study group has made efforts to clarify the condition of application and accuracy of each measurement method with regard to the flow measurement method of steam. The number of committee members is 30 (chief: Shuichi Umezawa (Tokyo Electric Power Company Holdings, Inc.), vice-chair: Ryo Morita (Central Research Institute of Electric Power Industry), secretary: Tatsuya Funaki (National Institute of Advanced Industrial Science and Technology)), who come from universities, companies, research institutes and others. The frequency of its activities is as follows: it holds study groups once or twice a year, summarizes its results and publishes a report. The predecessor of this study group, the "Workshop of Wet Steam Flow Measurement" (April 2012 - March 2017), also published a report summarizing its overall activities. On the basis of these results, an academic standards development committee has been set up this year and is preparing guidelines for the correction of wet steam flow rate indications from the perspective of thermal energy utilization.

Теоретический анализ процесса расширения влажного водяного пара в рабочей камере поршневого длинноходового линейного привода компрессорного агрегата

In this paper, the process of expansion of wet water vapor in a piston long-stroke low-speed drive of a low-flow compressor unit is considered. The study is carried out on the basis of the developed mathematical model, which includes both the basic thermodynamic equations and the equations describing the process of heat exchange of the working substance with the walls of the working chamber during the expansion process. The results of the calculations carried out reflect the dependences of pressure, temperature and degree of dryness on changes in the volume of the working cavity at various values of the initial degree of dryness in the process of expansion and the duration of the process. An analysis of the results obtained shows that an increase in the cycle time and a decrease in the initial degree of dryness lead to an intensification of the process of condensation of wet steam in the process of expansion and the possibility of obtaining complete condensation of the working fluid.

Анализ влияния быстроходности аммиачной тихоходной компрессорной ступени на процессы обратного расширения и всасывания в области влажного пара

The paper presents a mathematical model of combined processes of reverse expansion and suction in the wet steam region, implemented in an ammonia low-speed long-stroke reciprocating compressor stage. The mathematical model is based on the equations of the first law of thermodynamics for a body of variable mass, the equation of state of a real gas, the Clapeyron–Clausius and Newton–Richman equations; various options for implementing the methodology for calculating the heat exchange process in the working chamber of the stage are also considered. A computational and parametric analysis of the effect of the piston speed on the performance losses of the compressor stage and on the degree of dryness of ammonia at the end of the suction process is performed, taking into account the existing uncertainty factors both in terms of the choice of methods for calculating heat exchange processes and in terms of the choice of initial and initial conditions.

Анализ влияния факторов неопределенности на математическое моделирование процесса обратного расширения аммиака в тихоходной поршневой компрессорной ступени. Часть 2

The paper presents the analysis of influence of the method of calculating the heat transfer coefficient on mathematical modeling of the process of reverse expansion of ammonia in the working chamber of the reciprocating compressor stage (in the area of wet steam). Alternative variants of film and drip schematization of the heat exchange process are considered. The mathematical model is based on the equations of the first law of thermodynamics for a body of variable mass, the equation of state of a real gas, the Clapeyron–Clausius and Newton–Richman equations. Based on the results of the computational and parametric analysis, the applicability of known methods for calculating the heat transfer coefficient to the object under consideration is evaluated.

Flow Pattern Recognition Based on the Received Waveforms of a Clamp-on Ultrasonic Flowmeter for Wet Steam Flow in a Horizontal Pipe

Flow Pattern Recognition Based on the Received Waveforms of a Clamp-on Ultrasonic Flowmeter for Wet Steam Flow in a Horizontal Pipe

Shape modification of the optical probe for wetness measurement using CFD calculations

An optical extinction probe is usually used for measurements of liquid phase parameters of wet steam in steam turbines. Since the probe is relatively large, its interaction with the flow field negatively affects the accuracy of the measurements. A shape modification of the optical probe has been proposed to reduce this negative impact of the probe-flow field interaction. The benefit of the proposed shape modification of the probe has been verified using numerical (CFD) calculations. In these CFD calculations, a non-equilibrium steam condensation which enables to simulate a formation and development (growth) of fine droplets has been considered.

Computational study of combined effects of tip leakage jets and wetness on the performance of steam turbine exhaust system using actuator disc model

A numerical model to study the individual and combined effects of the tip clearance jets and the presence of wetness on the performance of the steam turbine exhaust hood has been developed. The Eulerian-Eulerian wet steam flow equations along with mass, momentum, energy, and k- ε model equations are solved in the present study. An increase in inlet wetness level improves the pressure recovery capacity of the steam turbine exhaust hood by reducing the total pressure loss. The presence of moisture causes a turbulence attenuation which in turn reduces the vortex strength. The combined effect of the tip leakage jets and the presence of inlet wetness improve the performance of the exhaust system further. However, the presence of a non-uniform condenser pressure gradient caused by the temperature variation of the cooling water flow increases the level of complexity of the flow in the exhaust system deteriorating the performance.

The application of modified thermodynamic system correction method to secondary reheat steam turbine

In order to calculation the enthalpy of wet steam in the secondary reheat turbine thermal system the thermodynamic system of the secondary reheat steam turbine based on the isentropic ideal expansion process line was corrected, This method simplifies the correction calculation step and increases the accuracy of the correction result. Analysis of the rationality of the improved method shows that: Compared with the existing secondary reheat steam turbine thermal system correction method, the maximum error of the improved thermal system correction method is 0.14%. Therefore, this method can better meet the test accuracy requirements.