Flash Chamber Research Articles

Flash evaporation in a superheated liquid pool using water as medium

This paper proposes a fast cooling technology called flash evaporation or flashing to overcome cooling problems. Flashing is a pressure-driven phase change phenomenon widely studied because of its complex physics and numerous applications. An experimental system is fabricated to study the efficiency of the proposed process by considering water as a working fluid. A transparent acrylic column is used as the flash chamber, enabled with a high-speed camera to visualize and capture this fast and complex process. Experiments have been carried out with various initial temperatures from 65 °C to 80 °C, initial vacuum tank pressure ranging from 11.32 kPa to 41.32 kPa, and initial water heights of 80 mm and 140 mm. The flashing phenomenon is divided into two stages based on its effectiveness. From the present study, it becomes apparent that the drop in the temperature increases with the initial temperature and decreases with increasing vacuum tank pressure. The cooling rate is improved by 49.1% by increasing the initial pool temperature by 23%. The present study demonstrates an effective application of the flashing process in areas requiring high cooling rates and rapid vapour generation, such as refrigeration and drying.

Analysis and Optimization of a s-CO2 Cycle Coupled to Solar, Biomass, and Geothermal Energy Technologies

This paper presents an analysis and optimization of a polygeneration power-production system that integrates a concentrating solar tower, a supercritical CO2 Brayton cycle, a double-flash geothermal Rankine cycle, and an internal combustion engine. The concentrating solar tower is analyzed under the weather conditions of the Mexicali Valley, Mexico, optimizing the incident radiation on the receiver and its size, the tower height, and the number of heliostats and their distribution. The integrated polygeneration system is studied by first and second law analyses, and its optimization is also developed. Results show that the optimal parameters for the solar field are a solar flux of 549.2 kW/m2, a height tower of 73.71 m, an external receiver of 1.86 m height with a 6.91 m diameter, and a total of 1116 heliostats of 6 m × 6 m. For the integrated polygeneration system, the optimal values of the variables considered are 1437 kPa and 351.2 kPa for the separation pressures of both flash chambers, 753 °C for the gasification temperature, 741.1 °C for the inlet temperature to the turbine, 2.5 and 1.503 for the turbine pressure ratios, 0.5964 for the air–biomass equivalence ratio, and 0.5881 for the CO2 mass flow splitting fraction. Finally, for the optimal system, the thermal efficiency is 38.8%, and the exergetic efficiency is 30.9%.

Experimental and numerical simulation study on the mass transfer characteristics of static flash evaporation

Due to the short duration and intense nature of static flash evaporation, and limited by the measurement methods, there is still limited understanding of the inhomogeneous characteristics of mass transfer within the waterfilm. This paper studies the spatiotemporal variation of mass transfer characteristics during static flash using experimental and numerical simulation methods. The formation and evolution mechanism of the bubble layer is analyzed, and its impact on the spatial distribution of temperature within the waterfilm is explained. Firstly, it was found that during the flash process, the temperature difference at different heights of the waterfilm first increases and then decreases. Secondly, during the flash process, there is a maximum value of the vapor generation rate within the waterfilm along the height direction of the flash chamber, and there is a spatial inconsistency between the vapor generation rate and the superheat distribution. Thirdly, reducing the initial waterfilm height can improve the consistency between the maximum superheat and the maximum volume fraction, resulting in a higher vapor generation rate per unit mass and an earlier peak appearance. This study contributes to a deeper understanding of flash mass transfer and provides ideas for the future enhancement of flash evaporation.

Development and modeling of power, hydrogen and freshwater production based on a novel double-flash geothermal power plant

In this article, a novel geothermal energy-assisted multigeneration plant is proposed and analyzed from the thermodynamic, economic, and environmental perspectives. In the design of the geothermal power system, a transcritical Rankine cycle, which employs CO2 as the working fluid (tCO2-RC), a Kalina cycle (KC), a hydrogen generation sub-plant, and a desalination unit are considered. The reverse osmosis (RO) desalination process is used for freshwater production, while the proton exchanger membrane (PEM) electrolyzer is utilized for hydrogen generation. In addition, parametric analyses are conducted to ascertain the impacts of the temperature of the geothermal source, mass flow rate, and flash chamber pressure on system performance. According to the results, the plant's overall energetic and exergetic efficiencies are determined to be 8.6 % and 34.9 %, respectively where the net power production is calculated as 3317.94 kW, and the system's total irreversibility is found to be 5852.88 kW. Furthermore, the hourly H2, O2, and freshwater generation amounts are 8.5 kg, 49.1 kg, and 9.3 m3, respectively. Finally, the levelized energy cost (LEC) and sustainability index of the system are found to be 0.128 USD/kWh and 0.215.

Performance enhancement of lab scale flash evaporation desalination system with sponge demisters: A practical approach

The current work focuses on mitigating the challenges associated with steam-carrying effects during flash desalination. Through experimental trials in a controlled laboratory setting, the impact of varying experimental parameters on the steam carrying ratio, flashing factor and separation efficiency is studied. Results suggested that the steam carrying ratio decreased with decreasing water pool height but increased with the degree of superheat and liquid entrainment. The value of the steam carrying ratio is reduced by 76.25 % by implementing a sponge inside the flash chamber at the same superheat. Liquid entrainment is significantly affected by the separation height and initial surge tank pressure. A high liquid entrainment results in a significant evaporated mass difference between experimental and theoretical results. The vapour mass transfer during the experiments without sponge arrangement is approximately two times the mass obtained from theoretical calculation. The results indicate that liquid entrainment is reduced by about 92% by incorporating the sponge at constant experimental conditions. The experimental data with sponge agree well with the theoretical results, with a maximum error of 18%. Finally, separation efficiency is proposed to compare the amount of liquid entrainment removed from total entrainment.

Analyzing the impact of vacuum level on the energy and exergy efficiency of a unique solar desalination unit driven by concentrating solar power technology

An in-depth analysis of a unique desalination unit based on concentrated solar energy was conducted in this study. A lab scale prototype was built and tested under variable vacuum levels between 0.3 bar and 0.7 bar to see how vacuum levels influence system performance. Results reveal a direct relationship between vacuum level and distillate production. Vacuuming of 0.7 bar produced a maximum distillate of 2520 ml/h. An average energy efficiency of 65.2 % was found for the brine heater. Moreover, the average exergy efficiencies were 88.2 % for the condenser, 17.2 % for the brine heater, and 41.6 % for the flash chamber. In order to determine the relationship between vacuum level and various system responses, mathematical models were also developed. Moreover, performance indicators such as energy utilization factor, gain output ratio, and specific energy consumption were also evaluated. The proposed device has a maximum energy utilization factor of 2.4, a maximum gain output ratio of 19.2, and a minimum specific energy consumption of 280.7 kWh/m3. The outcomes of this research are expected to provide valuable insights into the impact of vacuum level on solar-powered desalination systems and contribute towards advancing renewable energy into desalination systems.

A Development in Solar Desalination System with Flashing of Solar Heated Water

Solar still was successfully used for the desalination of saline water in many arid and oceanic regions of the world. But the yield of solar still was found very low and fluctuating. The new develop system with the flashing of solarheated water is found possible during the study of flashing of hot water in many thermal processes used during the chemical and pharmaceutical processes. A compact and effective desalination system using solar energy had designed during the research work from the design reviews collected from flashing hot water devices used in many thermal processes. The compact flash chamber and flash steam condenser are critical components developed for the novel desalination system using locally available materials during the research work. In present experimental work a flash chamber is designed for flashing of solar heated water. Experimental work shows that by increasing the mass flow rate of water from 0.01 kg/sec to 0.02 kg/sec the distillate output of water could be increased with higher temperature of water. It shows that around 38% of higher distillate output in water could be achieved with development of new system.

Performance Evaluation of Single Stage Flash Evaporation Desalination Unit Integrated with a Parabolic Trough Solar Collector for Basrah City Climate, Iraq

Solar energy is the most suitable among all renewable energy options for competing with fossil fuels in desalination due to its ability to utilize both heat and power for the process. In this study, the Parabolic Trough Solar Collector (PTSC) for powering a Single Stage Flash (SSF) desalination unit was proposed for Basrah city climate, Iraq. The desalination system comprises two directly coupled sub-systems: the PTSC and the SSF desalination unit. The preheated feed brine water coming from condenser was used as a Heat Transfer Fluid (HTF) for PTSC, which gets heated to a desired temperature referred to as the Top Brine Temperature (TBT). The numerical simulations were performed via EBSILON professional 16.02 (2022) software. The effects of TBT, mass flowrate of feed brine water to get the desired TBT, solar collector area, and vacuum pressure inside flash chamber on the performance of the desalination system was studied. A major finding of the current study can be summarized as follows: The collector efficiency is enhanced eventually as TBT increases. The maximum values of distillate water in June are around 5.5, 4.56, 3.69, 2.75 and 1.85 kg/h for 12.408, 10.434, 8.3472, 6.26, and 4.1736 m² collector area respectively, when TBT 107 °C and vacuum pressure 40 kPa. For 1.598 m² collector area, the total distillate in the 1st of June amounted to 7.9 kg, with an average production rate of around 0.7 kg/h. The solar SSF system's productivity per solar collector unit area at 20 kPa, 15 kPa, and 10 kPa vacuum pressures was 4.7 kg/day/m², 5.3 kg/day/m², and 6.25 kg/day/m², respectively. The average Performance Ratio (PR) values are determined to be 0.694, 0.577, and 0.491 for 10 kPa, 15 kPa, and 20 kPa, respectively. These results are very acceptable when compared with an existing literature.

Characteristics study of non-equilibrium flash for two-phase expansion based on equivalent expansion experiments

The two-phase expansion inside the expander could be divided into the non-equilibrium flash of superheated liquid and the expansion of the vapor. A higher flash rate would permit higher recovered expansion work. However, it is almost impossible to measure the flash rate inside the expansion chamber. In this paper, an equivalent expansion method s was proposed to study the non-equilibrium flash process for the two-phase expansion. The flash was controlled inside a constant volume flash chamber, which was connected to a vacuum tank to introduce and adjust the flashed vapor rate out of the flash chamber. The flash process inside the chamber was controlled under the working conditions similar to that inside the two-phase expander. By applying the equivalent expansion method, the flash rate could be measured easily. The experiments were carried out with an initial liquid height inside the chamber from 110 to 175 mm, and an initial liquid temperature from 110 to 130 °C with water as the working fluid. The instant flash rate and the PV diagram of the equivalent two-phase expansion were studied. Results showed that the instant flash rate increased and decreased sharply at first, and then the flash became gentle. Thus, the non-equilibrium flash of the two-phase expansion was divided into two stages of the rapid expansion process and the gradual expansion process. It was found that most of the flashed mass was generated during the rapid expansion process. Finally, a non-equilibrium flash model was proposed to simulate the flash process during the two-phase expansion process with the accuracy of ±3.7% predicting the pressure profile and the accuracy of ±2.7% predicting the expansion work.

A novel methodology for enhancing refrigeration performance using regenerative expansion in VCR system

Refrigeration is indispensable for a wide array of applications, ranging from household cooling to industrial freezing. Traditionally, mechanical methods have been utilized to transfer heat between different temperature reservoirs. However, the quest for energyefficient and low-maintenance systems has propelled innovations in refrigeration technology. One such innovation involves optimizing the utilization of flash gas within the system. This gas, if allowed to traverse the evaporator, can gradually deteriorate its components, resulting in heightened maintenance demands. To mitigate this issue, our modified system integrates a flash chamber downstream of the expansion device, such as a capillary tube. This chamber effectively segregates the flash gas from the liquid refrigerant. In our design, the separated flash gas is channeled into a shell and tube heat exchanger positioned adjacent to the condenser. Here, the flash gas circulates the tubes of the heat exchanger, efficiently extracting heat from the refrigerant flowing within the tubes. This strategic utilization of flash gas not only enhances the overall efficiency of the refrigeration system but also minimizes wear and tear on the evaporator components. Moreover, the outlet of the flash gas is connected to the inlet of the compressor, completing the cycle. By harnessing flash gas in this manner, our modified system not only enhances energy efficiency but also reduces maintenance requirements, offering a sustainable and economically viable solution for refrigeration needs. This innovative approach underscores the transformative potential of system modifications in advancing refrigeration technology, in line with the growing demand for environmentally friendly and efficient cooling solutions

Salinity impacts on a unique desalination system embedded with concentrated solar energy for cleaner production

This research comprehensively analyzed a unique solar desalination unit that operates on concentrated solar energy. The analysis primarily focused on evaluating three crucial components: the condenser, flash chamber, and brine heater. Testing was initially performed using seawater sourced from the eastern region of Saudi Arabia. Subsequently, to investigate the influence of salinity on the system performance, the device was tested under variable salinity levels ranging from 15,000 ppm to 35,000 ppm. Key parameters, including condenser temperature, brine heater temperature, and distillate production, were measured throughout the experimentation. The findings unveiled an inverse correlation between salinity and distillate production, as increasing the salinity from 15,000 ppm to 35,000 ppm resulted in a decline in distillate production. The maximum distillate achieved was 2400 ml/h at a salinity level of 15,000 ppm, corresponding to a constant feed rate of 0.2 l/min. The average energy efficiency of the brine heater was determined to be 61.9%. Moreover, the average exergy efficiencies were calculated as 81.3% for the condenser, 4.4% for the brine heater, and 44.3% for the flash chamber. Mathematical models were subsequently developed to establish the relationships between salinity and various system responses. Furthermore, performance metrics such as gain output ratio, energy utilization factor, and specific energy consumption were evaluated. The proposed system has a maximum gain output ratio of 16, a maximum energy utilization factor of 2.2, and a minimum specific energy consumption of 299.3 kWh/m3.

Techno-economic assessment of low-grade geothermal heat-driven ejector refrigeration cycle with a flash chamber and a booster compressor

Techno-economic assessment of low-grade geothermal heat-driven ejector refrigeration cycle with a flash chamber and a booster compressor

Numerical Simulation Method for Flash Evaporation with Circulating Water Based on a Modified Lee Model

Flash evaporation processes are widely adopted in the desalination, food processing, waste heat recovery and other industries for heat extraction or product separation. In this paper, a pressure-driven phase transition model is developed by improving the Lee model and combined with the VOF (Volume of Fluid) method to numerically simulate the flash evaporation process. In this modified Lee phase transition model, the driving force for the rates of the local phase transition is calculated using the local temperature and static pressure magnitude. Numerical simulations are carried out in a water-circulating flash chamber and compared with the experimental results to obtain the values of the time relaxation parameters. And the non-equilibrium fraction of the outlet water can be effectively obtained under different conditions of flow rate, inlet temperature and initial liquid level height. The time relaxation factor takes values from 0.195 to 0.43 (Pout,v = 19.9 kPa) and from 0.31 to 0.92 (Pout,v = 31.2 kPa) with increasing superheat. In addition, the model can effectively represent the evolution of the unstable flow flash evaporation from the initial rapid boiling state to dynamic equilibrium.

3E investigation and artificial neural network optimization of a new triple-flash geothermally-powered configuration

Geothermal systems are among the world's most well-appreciated sources for providing heat to generate power and exploit in numerous ways, attracting attention worldwide due to abundancy and renewability. The present investigation is dedicated to a cogeneration system providing power and hot water for domestic use. The novel system consists of three flash chambers and three turbines intended for power production. The heat source is geothermal subterranean reservoir. Furthermore, thermoelectric generators were creatively implemented as substitutions for condensers so to produce surplus power by utilizing waste heat. The proposed cycle was primarily analyzed with respect to the first and second laws of thermodynamics. As an additional novelty, entransy analysis was also included. After which, the findings were validated in accordance to previously verified scientific resources. The study revealed that the overall power production in the basic mode was 133 kW, 35.62 kW of which was generated by the TEGs. Further, the first and second law efficiencies for the integrated cycle were 26.8% and 64.8, respectively. The sum of entransy loss throughout the integrated system was 8.77MWK. Eventually, an artificial neural network optimization was performed to identify the optimum states of the system, where exergy efficiency and entransy loss were assigned as the objectives.

Experimental analysis of heat transfer characteristics of static water pool under low pressure vaporization

Low pressure vaporization (LPV) is considered a promising method for rapid cooling and a significant rate of water vaporization. This article presents an experimental investigation for the detailed heat and mass characterization of a static water pool exposed to low pressure conditions. An LPV experimental setup has been fabricated in the lab to investigate the effect of process parameters like initial temperature (Tw,0), initial vacuum tank pressure (Pv,0), and the water pool height (Hw,0) on the non-equilibrium fraction (NEF) and heat transfer coefficient (hv). Results shows that NEF initially increased to a high value and then tediously dropped. The final value of NEF decreased with decreasing the initial vacuum tank pressure and initial water pool height inside the flash chamber. A maximum value of the hv existed with the rise of the degree of superheat (ΔT) of liquid. It is found that with an increase of the degree of superheat by 13.44 °C, the value of hv is enhanced by 67%, and the NEF decreased by 46.7%, respectively.

Experimental studies on solar multi - effect sea water desalination system

A multi - effect desalination (MED) system with a capacity of 10 m3 has been designed, fabricated, erected and experimented to convert sea water into potable water using solar energy. Steam is flashed initially in the flash chamber of the desalination plant, using hot water from a solar flat plate collector field and is fed to the first stage of the multi-effect evaporator. The average hot water temperature realised from the collector field is 75°C. In the multi-stage evaporator, sea water is sprayed parallelly to vacuum pressure to produce water vapour and simultaneously condense the water vapour flashing through the tube from the flash chamber / previous effects. The brine and condensate is carried to the last stage of the multi-effect desalination (MED) system by utilizing monometric head. It is observed that during the experimentation, the maximum temperature difference between inlet and outlet of the condenser cooling water is 13°C. The ejector is used to maintain the vacuum pressure during the operation of MED system including flash chamber. Experimental studies on the MED system is carried out to understand the performance as well as thermal behaviour of the system using exclusively solar energy.

Proposal and Investigation of a New Tower Solar Collector-Based Trigeneration Energy System

These days, the low efficiency of solar-based thermal power plants results in uneconomical performance and high-cost uncompetitive industries compared with conventional fossil fuels. In order to overcome such issues, a novel combined cooling–power–heating (trigeneration) system is proposed and analyzed in this paper. This system uses an ammonia–water binary mixture as a working fluid and a solar heat source to produce diverse types of energy for a multi-unit building in a sustainable fashion. In addition to the basic cooling–power cogeneration cycle, a flashing chamber that will boost the flow rate of refrigerant without any additional heat supply is employed. By developing a mathematical model, the system performance is analyzed using varying parameters of solar irradiation, hot oil temperature, process heat pressure, and ambient temperature to investigate the influence on electrical power, cooling capacity, refrigeration exergy, energy utilization factor (EUF), and system exergy efficiency. Increasing direct normal irradiation (DNI) from 500 W/m2 to 1000 W/m2 reduces the system EUF and exergy efficiency from 53.62% to 43.12% and from 49.02% to 25.65%, respectively. Both power and refrigeration exergy increase with increasing DNI and ambient temperature, while heating exergy remains constant. It is demonstrated that of 100% solar energy supplied, 46.03% is converted into energetic output and 53.97% is recorded as energy loss. The solar exergy supplied is distributed into 8.34% produced exergy, 29.78% exergy loss, and the remaining 61.88% is the destructed exergy. The highest destruction of solar exergy (56.89%) occurs in the central receiver.

English

Modeling of the PV-thermal solar collector and thermal storage PCM using magnetized nanofluids to power the multi-stage flashing chambers to desalinate seawater has been presented. The proposed model was established after the mass and energy conservation equations were written for finite control volume with properties of the magnetized nanofluids heat transport fluid. The magnetized nanofluids studied and presented hereby are Ai2O3, CuO, Fe304, and SiO2. At different magnetic fields up to 3000 Gauss, the multiple chamber flashing process has been studied under various conditions, including different solar radiations, brine flows and concentrations, nanofluids concentrations, and flashing chamber temperatures and pressures. Solar radiations were taken as 500 w/m2, 750 w/m2, 1000 w/m2, and finally, 1200 w/m2. Nanofluids volumetric concentrations considered varied from 1% to 20% There is clear evidence that the higher the solar radiation, the higher the flashed flow produced. The results also clearly showed that the irreversibility is reduced by using magnetized nanofluid Ai2O3 at higher concentrations of 10% to 20% compared to water as base fluid. The highest irreversibility was experienced when water was used as a base fluid, and the lowest irreversibility was associated with nanofluid SiO2. The irreversibility increase depends upon the type of nanofluid and its thermodynamic properties. Furthermore, the higher the concentration, 10% to 20% of Ai2O3, the higher the availability at the last flashing chamber. However, the availability is progressively reduced at the last flashing chamber. Finally, the predicted results were compared well with experimental data published in the literature.

Exergy analysis of vacuum ice production device by solid adsorption

This paper proposes a vacuum ice production device by solid adsorption. An analysis model related to exergy loss and exergy efficiency is established in each component of the vacuum flash ice making system. By comparing the exergy analysis results of adsorption vacuum ice production device and condensing vacuum ice production, this paper has drown an effective method to reduce exergy loss. It has been found that the exergy efficiency of the adsorption vacuum ice production device is 9.64% higher than that of the condensing vacuum ice production device. The exergy efficiency of water vapor adsorption in the adsorption chamber is the highest, while the exergy efficiency of water vapor adsorption in the condensation chamber is the lowest. In order to reduce the energy demand of the device, the heat released by the condenser should be fully utilized to reduce the exergy loss of the condenser. At the same time, the heat and mass transfer of the flash evaporation process should be enhanced when designing the flash chamber, such as optimizing the ice making working fluid to improve the exergy efficiency of the flash chamber.

Multi-Objective Optimization of a Geothermal Steam Turbine Combined With Reverse Osmosis and Multi-Effect Desalination for Sustainable Freshwater Production

Abstract A novel geothermal desalination system is proposed and optimized in terms of maximizing the exergy efficiency and minimizing the total cost rate of the system. The system includes a geothermal steam turbine with a flash chamber, a reverse osmosis unit, and a multi-effect distillation system. First, exergy and economic analyses of the system are performed using Engineering Equation software. Then, an artificial neural network is used to develop a mathematical function linking input design variables and objective functions for this system. Finally, a multi-objective optimization is carried out using a genetic algorithm to determine the optimum solutions. The Utopian method is used to select the favorable solution from the optimal solutions in the Pareto frontier. Also, the distributions of the values of design variables within their allowable ranges are investigated. It is found that the optimum exergy efficiency and total cost rate of the geothermal desalination system are 29.6% and 3410 $/h, respectively. Increasing the seawater salinity and decreasing the intake geothermal water temperature result in an improvement in both exergy efficiency and total cost rate of the system, while variations in the flash pressure and turbine outlet pressure lead to a conflict between the exergy efficiency and the total cost rate of the geothermal desalination system over the range of their variations.