Steam Condensation Research Articles

Optimizing Plate Heat Exchanger Design for Steam Condensate Recovery Systems

Condensate water is typically generated as a by-product during the use of steam as a medium for heat transfer. In order to optimize the transfer area, the chemical industry often employs heat exchangers, such as the plate heat exchanger (PHE), which provides flexibility in adjusting the space area for heat transfer. This case study examines the optimization of plate geometry dimensions to enhance the heat transfer process of PHE equipment design. The optimization process involves mathematical equations and a literature review of the design of this type of heat exchanger. Improving the dimensional aspect of the plate geometry results in an increase in the overall heat transfer coefficient (U) and a reduction in the number of design requirements used. The study's estimation results suggest that the PHE design has a limitation on plate dimensions, which should be less than 0.3×0.6 m. Additionally, it is important to consider the pressure drop value, which should not exceed 29.07 kPa. A review of the chemical industry field provided estimated options for plate size and quantity, both of which support the optimization of heat transfer rate and design constraint thresholds. The implementation of the design has been found to enhance the performance of the planning process for recovering steam condensate water.

Enhancing Axial Flow Fan Performance in Air-Cooled Condensers: Tip Vortex Manipulators and Comparative Analysis of Numerical Simulation and Experimental Testing

Abstract Direct dry-cooled power plants typically operate numerous large-diameter axial flow fans in air-cooled condensers (ACCs) to facilitate the condensation of steam in the plant's thermodynamic cycle. Enhanced fan efficiency may, at scale, lead to significant parasitic power reductions and subsequent increases in plant power output. The performance of these fans may be increased by adding blade-tip modifications, which act to control blade-tip leakage flow. Previous studies have shown that manipulating the tip leakage vortex (TLV) increases the blade-to-air momentum transfer and stabilizes the air flow structures as it traverses the fan blade. This paper takes a step toward the development of improved tip vortex manipulators for an ACC fan. Three-dimensional computational fluid dynamics (CFD) simulations, and experimental testing of the modified and unmodified fan within an ISO test facility are performed. The results are then utilized to assess the accuracy of the simulation model, visualize the manipulated flow structures at the blade tip, and ultimately quantify the effect of the endplate designs on fan performance. Excellent correlation between numerical and test results for the unmodified fan is observed, and the benefit of blade-tip modification on fan performance is again confirmed experimentally. The simulation model, however, fails to predict improvements in fan performance under modification, and simulated tip leakage flows are investigated for clarification. It is hypothesized that deflection of tip endplates under operation account for differences between simulation and experiment, and that fluid–structure interaction analyses could potentially resolve discrepancies.

Efficiency of gas condensate heaters in reducing operating costs of combined-cycle gas installations

This article examines the efficiency of gas condensate heaters in the context of reducing the operating costs of combined-cycle gas installations. Gas condensate heaters are an innovative technological solution aimed at restoring the heat released during steam condensation. Based on the principles of returning part of the heat back to the system, their use contributes to a significant reduction in fuel consumption, which, in turn, leads to a reduction in operating costs. The work examines the mechanisms of operation of gas condensate heaters, their thermal characteristics, as well as their impact on the overall energy efficiency of combined-cycle gas installations. Using the example of the oil refining industry, the practical application of this technology for optimizing thermal processes is demonstrated. In conclusion, the importance of gas condensate heaters in the context of building environmentally sustainable and energy-efficient production systems is emphasized.

Analysis of total flavonoid and antioxidant activity of coconut shell liquid smoke (Cocos nucifera L.) as an antibacterial

Background: Coconut shell is often used for cooking or treated as waste. Liquid smoke is a by-product of coconut shell processing, which results from condensation of combustion steam. It is divided into grades one, two, and three based on the characteristics and utilisation. It contains phenolic, carbonyl acids and other compounds which act as antioxidants, antibacterials, and antifungals. Objective: To determine the total content of flavonoids, antioxidants and antibacterial activity in liquid smoke. Method: Liquid smoke was produced by a pyrolysator and distilled to produce grades one, two and three. It was then tested for antibacterial activity using the minimal inhibitory concentration (MIC) method against S. aureus and E. coli. The AlCl3 reagent and DPPH method were used to determine the total flavonoid and antioxidant levels, respectively. Results: The MIC of grade one, two, and three coconut shell liquid smoke was 10%; 10%; 5% against S. aureus; and 10%, 5%, and 5% against E. coli. The total flavonoid yields from grades one, two and three were 0.0041, 0.0174, and 0.2741 mg QE/ml, respectively. Test results for antioxidant grades with IC50 values were 142.82, 121.64, and 90.80 µg/mL. Conclusion: Coconut shell liquid smoke has antibacterial activity, contains a certain amount of flavonoids, and also possesses antioxidant activity.

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.

Overview on GRS CFD activities related to containment applications

Abstract In the case of a severe accident in a nuclear power plant, hydrogen could be produced in the superheated reactor core. The hydrogen could flow through a leak in the primary circuit into the containment and a hydrogen deflagration could occur. A consequence of such an event was the Fukushima accident in 2011. For the analysis of such events, different phenomena in the reactor containment must be simulated correctly such as the distribution of steam and hydrogen, steam condensation, thermal radiation, conjugated heat transfer, hydrogen recombination and deflagration. The application of Computational Fluid Dynamics (CFD) methods for such analyses is becoming more relevant. Selected models needed to simulate the different containment phenomena with OpenFOAM are currently being tested, validated or improved and further developed by a network of German research institutes and universities.

CFD simulations of helium layer erosion in one PANDA vessel following cooler activation

We performed CFD simulations of the two H2P6 cooler tests conducted in the PSI PANDA vessel as part of the OECD/NEA HYMERES-2 project. Initially, the vessel atmosphere consists of a 60/40 % vol. steam- air mixture. Then, a helium stratification (15 % vol.) is introduced in the upper half of the vessel. The two experiments H2P6_1 and H2P6_2 are characterized by the activation respectively of 3 and 1 cooler(s) in the upper part of the vessel. In the course of the experiments, condensation takes place, resulting in a gradual pressure decay and erosion of the helium layer until complete mixing is achieved.The URANS k-ε is used to model turbulence. CFD Best Practice Guidelines are followed to minimize numerical errors, with preliminary mesh sensitivity studies. A correlation based on the heat-and-mass transfer analogy is employed to estimate steam condensation rates.Each cooler consisting of 18 tubes is simplified into a cuboid with equivalent heat transfer area. In a further simplification, it is assumed that the cooler wall has a thickness of zero and is initially at the temperature of the coolant. The small initial energy stored in the mass of the cooler at time zero is therefore neglected.The simulation for H2P6_1 matches the main experimental parameters (heat removal rate, pressure, species concentrations) almost perfectly. For H2P6_2 the heat removal rate is slightly under-predicted, with a corresponding over-prediction of the pressure by a maximum of 3 %. The inclusion of radiative heat transfer modeling improves the accuracy of the temperature field but has little influence on the pressure or heat removal histories.These results show that CFD allows accurate predictions of containment mixing when coolers are activated. Moreover, the simulations also indicate that multiple cooler units can be represented by one larger equivalent unit.

Numerical Simulation on Two-Phase Ejector with Non-Condensable Gas

The two-phase ejector is a simple and compact pressure boosting device and widely used in ejector steam-generator water feeding systems and core emergency cooling systems. The direct contact condensation of water and steam is the key process of a two-phase ejector. Usually, the high-temperature and high-pressure steam will inevitably induce non-condensable gases. The existence of non-condensable gases will reduce the condensation heat transfer rate between steam and water, and harm the equipment. This study carried out 3D numerical simulations of a two-phase ejector based on an inhomogeneous multiphase model. The steam inlet pressure and the non-condensable gas mass fraction rang in 0.6–2.9 MPa and 1–10%, respectively. The heat and mass transfer characteristics were analyzed under different conditions. The results show that the heat transfer coefficient and plume penetration length increased with the steam inlet pressure. Non-condensable gas prevents direct contact condensation between the steam and water. The non-condensable gas mass fraction rises from 1% to 10%, the heat transfer between steam and water deteriorates, and leads to a lower heat transfer coefficient.

Experimental investigation on the effect of direct contact condensation regime on thermal stratification

Direct contact condensation affects the performance of a small modular reactor with pressure suppression system. Since the heat and mass transfer varies with the condensation regimes as well as steam-water interface shapes, the identification and classification of the condensation regimes are important. The experiment of steam direct contact condensation was carried out and the corresponding condensation regimes were studied. Specifically, the experiment was studied by injecting steam vertically into a wet well with subcooled water. The physical process of steam condensation phenomenon with varying undercooling degree of wet well was recorded by high-speed camera. According to the location of the steam-water interface and the shape of the steam bubble, the four condensation regimes were studied, namely chugging, external necking, spheroidal upward bubble and T-shaped upward bubble. Besides, it is found that thermal stratification occurs in the wet well at low steam mass flux, the influence of each condensation regime on the thermal stratification of wet well was studied. The experimental results show that the internal chugging and external necking cause a large downward circulation of subcooled water, which enhance the flow mixing around the discharge tube and the bottom of the wet well. Consequently, the thermal stratification phenomenon does not happen in those condensation regimes. However, the regimes like spheroidal upward bubble and T-shaped upward bubble cause the upward circulation of subcooled water in wet well, which cause the thermal stratification. The critical Richardson number (Ri) determines the condensation regimes. Furthermore, when the Ri is smaller than 1, the condensation regime is external necking. Besides, when the Ri is greater than 1, the condensation regimes are spheroidal upward bubble and T-shaped upward bubble.

NUMERICAL AND EXPERIMENTAL INVESTIGATIONOF STEAM FILM CONDENSATION ON A VERTICAL TUBE

NUMERICAL AND EXPERIMENTAL INVESTIGATIONOF STEAM FILM CONDENSATION ON A VERTICAL TUBE

Cascade type solar distiller with the use of photothermic materials applied in the treatment of surface water

The biggest challenge in solar energy distillation is the increase the production of treated water, so several research have been done to increase the daily yield of solar distillers, increasing the evaporation of saline water and consequently the condensation of steam. The objective of this work was to analyze the simultaneous performance of three cascade solar distillers with a wave-shaped heat absorber plate and the use of photothermal materials. The experiments were divided into three stages A, B and C. In step A, heat absorption tests of the photothermal materials (gravel, marbles, granite and ceramic tile) were performed. In stage B, the initial productivity of the three distillers (D1, D2 and D3) was measured, and in step C the productivity of the distillers was made with the introduction of photothermal materials in the less productive distillers. It was found that the introduction of photothermal materials (gravel and marbles) in distillers (D2 and D3) resulted in an increase in water production of 8 and 18% respectively.

Optimization Analysis of Multiple Steam Turbines and Condensers in Paper Mill Power Plant

The cooling tower water’s influence on turbines and condensers thermal efficiency were researched in this paper and the condenser working condition impact to turbines thermal efficiency was also discussed. Based on the basic model of turbines, condensers and cooling water, the optimization model for the system of turbines, condensers, cooling water and cooling water towers fan was proposed. One paper mill power plant which has multiple turbines, condensers and cooling water towers was taken as a case to verify the optimization model, the result showed that the optimization model was practical and useful for paper mill power plant; it can improve power plant efficiency and bring good economical performance for paper

Heat transfer characteristics in vertical tube condensers: Experimental investigation and numerical validation

The paper establishes a vertical steam condensation heat transfer experimental device to investigate the process of liquid film condensation heat transfer under the countercurrent heat transfer of a secondary coolant. An improved experimental method, integrating measurements and simulations, accurately calculates local heat transfer coefficients and heat flux. The validity of the data is confirmed through comparison with established condensation correlations, affirming the method's effectiveness. The correlations of previous research (i.e., Numrich, Carey, Oh, Lee, and Shah) demonstrate greater consistency with the experimental results, with mean relative deviations (MRD) of −4.90%, 7.18%, 11.42%, −8.63% −4.45%, and mean absolute relative deviations (MARD) of 11.61%, 21.57%, 23.60%, 18.97%, and 12.53%, respectively. Numrich's correlation demonstrated the closest congruence. Based on these results, the research proposes a new coupled heat transfer model, effectively simulating the interaction between external cooling water and steam condensation. This model simplifies the process by pre-defining coolant temperature changes per unit length, thereby reducing the need for extensive iterative calculations and eliminating assumptions about wall temperature. It accurately predicts the wall temperature, local condensing temperature, and coolant temperature in a vertical condenser. These experimental methods and models offer valuable insights for optimizing vertical condenser design and analysis. The study underscores the significance of combining simulation models with experimental measurements to enhance the understanding of heat transfer in complex systems. The findings promise to advance research in film condensation heat transfer and assist in condenser design and optimization.

Scaling analysis for the condensation induced water hammer effect in horizontal pipe

In nuclear power engineering, researchers pay significant attention to phenomena related to the condensation process involving direct contact between saturated steam and subcooled water, mainly the phenomenon known as Condensation Induced Water Hammer (CIWH). Within the steam pipes of the pressurized water reactor, when saturated steam comes into direct contact with subcooled water, it may form an isolated steam pocket surrounded by water. The condensation of steam within this pocket results in its subsequent collapse, accelerating the surrounding water column to collide with the pipe wall and causing a substantial pressure peak. In this paper, the scaling analysis was conducted on the CIWH phenomenon in the steam line of a small PWR. The research is rooted in a two-fluid, six-equation framework and employs equation-based analysis to investigate the non-dimensional number of CIWH occurring within horizontal pipelines. By analyzing the conservation equations, suitable non-dimensional criteria for thermohydraulic phenomena were determined. These criteria can be employed to ascertain experimental facilities' geometric dimensions and operating conditions, which can study the risks associated with CIWH phenomenon.

Analysis of the Multiphase Flow With Condensation in the Two-Phase Ejector Condenser Using Computational Fluid Dynamics Modeling

Abstract The liquid-driven two-phase ejector condenser is the object of the numerical investigation. The spray-ejector condenser is one of the critical components of the developed gas power plant with negative CO2 emission. The task of the ejector is to entrain exhaust gas and condense steam contained in it. Computational fluid dynamics (CFD) modeling allows analyzing complex phenomena and predicting the influence of a wide range of operating parameters on the local structure of the multiphase flow with condensation. The geometrical model of the ejector was designed to provide efficient steam condensation and generate sub-pressure region at the gas inlet. The 2D, axisymmetric CFD model was created using simcenter star ccm+ software. The multiphase mixture model was used to take into account two-phase flow. Turbulent flow was computed using k–ω SST model. Direct contact condensation of steam was calculated using two different approaches: the Spalding/evaporation model and the thermally-driven boiling/condensation model. The influence of various gas inlet velocities and the presence of CO2 on the operation of the ejector condenser were investigated based on scalar fields and charts representing changes in the most important variables along the flow path. The condensation is the most intense in the suction chamber. The boiling/condensation model predicts lower suction pressure and higher condensation effectivity than Spalding/evaporation model. The CO2 considerably affects the pressure and temperature distributions and reduces the condensation rate.

Impact of inlet steam state on ejector internal flow and performance considering non-equilibrium condensation

Most of the numerical studies adopted dry gas model to predict transonic and supersonic flow in steam ejectors, but it cannot accurately reflect flow characteristics in ejectors, since the condensation and evaporation of wet steam is ignored. The current work develops and validates a CFD model describing spontaneous condensation to simulate complicated flow behaviors and phase transition inside an ejector, and illustrates the impact of initial state of primary fluid including wet, saturated and superheated state on flow characteristics, mass and heat exchange and ejector performance. It is found that the initial steam wetness obviously impacts the average liquid fraction in the ejector. Both the superheated and wet initial primary steam suppress the process of mass and heat exchange during nucleation, and the position and intensity of nucleation are influenced by the inlet steam state. Compared with the case of dry saturated inlet steam, the superheated inlet steam improves entrainment ratio by 3.7%, and decreases compression ratio by 2.5%.

Numerical study on thermal hydraulics characteristics during steam submerged jet condensation from rectangular CD nozzle

The phenomenon of steam-water direct contact condensation (DCC) has significant importance in nuclear industry due to its rapid and efficient heat and mass transfer rates. In this numerical study, three dimensional simulations of steam submerged jet condensation from rectangular converging-diverging (CD) nozzle into subcooled water has been investigated. The steam condensation phenomenon has been captured from thermal phase change model as user defined function (UDF) in ANSYS Fluent software. The computational results were validated using experimental results as well as previously published numerical study. The effects of steam pressure and water temperature on distributions of various thermal hydraulics parameters including velocity, pressure, temperature, heat and mass transfer characteristics have been studied. The steam pressure and water temperature have been kept in the range of 200–500 kPa and 20–60 °C, respectively. The maximum value of jet velocity and heat transfer coefficient have been found as 803 m/s and 2.73 MW/m2K respectively. The peak velocity value increases with steam pressure. After maximum expansion point, the velocity profile curve is shifted downstream with steam pressure. The axial pressure distribution first decreases and then increases from expansion-compression waves. The axial temperature profile followed the similar trend as observed for axial steam pressure distribution. At constant steam pressure, the maximum rate of heat transfer coefficient decreases with the increase in water temperature. The maximum mass transfer rate under prescribed flow conditions has been found as 2789.8 kg/m3s. The peak mass transfer rate decreases with steam pressure and water temperature. The peak rates for heat and mass transfer have been observed in the nearby vicinity of nozzle exit location.

The impact of the distribution of the condensation energy adsorbed in the water pool on the DCC efficiency at sub-atmospheric pressure

The safety of a fusion reactor like ITER relies on the reliability of the pressure suppression system (for keeping pressure below 0.15 MPa during accidental scenarios), and, in turn, on the efficiency of Direct Contact Condensation (DCC).In this study, the role played by the distribution of the condensation energy in the water is analysed considering the experimental results of temperature and pressure recorded during steam condensation tests in a closed volume at sub-atmospheric conditions.The investigation of the mechanisms involved in the condensation at the water-steam interface is fundamental to verify that the subcooled water mass fully participates into the steam condensation for all the foreseen condensation regimes. Particularly, the paper analyses the distribution of the condensation energy in a water pool for different test conditions and with reference to the large-scale facility under operation at the DICI-University of Pisa.The subcooled water volume of the condensation tank in this system was assumed subdivided in 104 annular discrete volumes corresponding to the location of temperature and pressure sensors (testing monitoring points). Moreover, this discretization was used to implement a model to visualize the experimental data and in particular the accumulation of the condensation energy in the different part of the water pool and of the vacuum space.The experimental results showed that most of the tests had a participating fraction of water mass greater than 50%. Nevertheless, the non-uniformity and stratification of the temperature in the water pool requires a greater water mass for condensing a given steam mass. The analyses of steady state pure steam condensation tests determined that it needs to increase 1.39 times the water mass respect to the case of full participation of the water at the steam condensation.

Simulation study on transport characteristics of leakage gas from the condenser of power plant

Exploring the transport characteristics of leakage gas in the condenser can facilitate quicker identification of leak points when using Helium tracer gas method for detection. We construct a 3-D physical model of the condenser to simulate the Helium gas leakage process within the tube bundle. On the steam side, we adopt RNG k-?, porous media, steam condensation, and convective diffusion models to describe steam and leakage gas-flow. On the waterside, we use the tube bundle thermal resistance model to describe the steam-water heat transfer. The research concludes with three key points. When the centripetal pressure gradient is insufficient, there will be leakage gas enrichment, resulting in flowing out in the form of diffusion. When there is no centripetal pressure gradient in the tube bundle region, it will extract only a small amount of upstream leakage gas along with steam through the flow. When reaching a stable level for leakage gas, the leakage intensity is proportional to the outlets? flow rate but is independent of the transport form. The deviation of the mass-flow rate decreases with the mesh quantity increasing, which is less than 2% when the mesh quantity is over 638228. The deviation between simulated and actual values of the two parameters is less than 5%, which reveals the good agreement between numerical calculation and actual work conditions. These conclusions can assist employees and researchers in evaluating data on leak points and enhancing detection techniques.

Intensification of Heat Transfer during Steam Condensation in Process Condenser of NPP Unit Cooling System

The paper investigates heat transfer during condensation of water vapor on vertical pipes of the process condenser of the cooling system of a nuclear power unit. The numerical study was performed at different mass flow rates of steam in the range of its change from 20 kg/s to 40 kg/s. Intensification of heat exchange is provided by the use of highly efficient heat exchange profiled tubes. The study used a set of heat exchange tubes (25 mm in diameter and 1.4 mm wall thickness) with the following values of the distance between the grooves of the profiled tube: 0.007075 m, 0.00875 m, 0.00925 m, 0.0105 m. The effect of the groove depth (from 0.0007 to 0.0009 m) on heat transfer during water vapor condensation on vertical pipes was also studied. The study was carried out for the range of changes in the Reynolds number for the condensate film from 5254.2 to 10508.5. The study obtained data indicating an increase in the heat transfer coefficient on the pipe with an intensifier compared to the heat transfer coefficient on a smooth pipe. This analysis did not take into account the change in tube wall temperature.