Steam Condensation Process Research Articles

Experimental study on heat transfer characteristics of steam condensation in the presence of air and CO2 outside a vertical tube

Under severe accident conditions, in addition to steam and air, there are also other non-condensable gases inside the containment, such as CO2 produced by the molten corium concrete interaction (MCCI). Due to the significantly higher molecular weight and density of CO2 compared to steam and air, CO2 will have a significantly different impact on the steam condensation process compared to air. However, few scholars have paid attention to the impact of CO2 on the condensation process, and there is no empirical correlation applicable to this condition. Therefore, this article investigates the effect of different CO2 concentrations on the steam condensation heat transfer coefficient (CHTC) in the range of system pressure from 0.2 to 1.3 MPa and subcooling from 30 to 130 °C through experimental methods. Meanwhile, based on relevant experimental data, a new correlation suitable for calculating the steam CHTC in the presence of CO2 and air was fitted. The results indicate that under low steam concentration conditions, the addition of CO2 will reduce CHTC, while under high steam concentration conditions, CO2 will increase CHTC. The increase in system pressure will strengthen the condensation promotion effect of CO2 and weaken its inhibitory effect on condensation. In addition, by comparing experimental data under different component conditions, it was found that the new empirical correlation has high computational accuracy, and the calculation results of this correlation can contain more than 90 % of the data within a 15 % error range.

Numerical Investigation of a Two-Phase Ejector Operation Taking into Account Steam Condensation with the Presence of CO2

The application of a two-phase ejector allows for the mixing of liquid and gas and provides effective heat transfer between phases. The aim of the study is a numerical investigation of the performance of a water-driven, condensing two-phase ejector. The research was performed using CFD methods, which can provide an opportunity to analyze this complex phenomenon in 2D or 3D. The 2D axisymmetric model was developed using CFD software Siemens StarCCM+ 2022.1.1. The Reynolds-Averaged Navier–Stokes (RANS) approach with the Realisable k-ε turbulence model was applied. The multiphase flow was calculated using the mixture model. The boiling/condensation model, where the condensation rate is limited by thermal diffusion, was applied to take into account direct contact condensation. Based on the mass balance calculations and developed pressure and steam volume fraction distributions, the ejector performance was analyzed for various boundary conditions. The influence of the suction pressure (range between 0.812 and 0.90) and the steam mass flow rate (range between 10 g/s and 25 g/s) is presented to investigate the steam condensation phenomenon inside the ejector condenser. The provided mixture of inert gas (CO2) with steam (H2O) in the ejector condenser was investigated also. The weakening of the steam condensation process by adding CO2 gas was observed, but it is still possible to achieve effective condensation despite the presence of inert gas.

Thermal analysis of condensation-induced vacuum and its feasibility for operating a vacuum membrane distillation system

Vacuum pumps are primarily used in vacuum membrane distillation (VMD) for vacuum generation. However, vacuum pumps are characterized by low operational durability and a high energy demand. In this study, a steam condensation process was combined with the VMD process such that the vacuum created during the steam condensation process drove the VMD operation. A thermodynamic cycle comprised of three main processes: steam purging, vacuum creation, and water recovery was described. This paper presents a detailed thermal analysis of each process of the thermodynamic cycle based on heat transfer and thermodynamic models. The modeling results are compared with experimental data. The pressure in the vacuum chamber increased during the water recovery process because of the accumulation of non-condensable gases, which permeated the chamber along with the water vapors. Consequently, the mass flux of the VMD permeate decreased, and finally, the permeation ceased when the pressure in the chamber reached ~20 kPa; after this stage, the cycle restarted. For the current experimental conditions and vacuum chamber design, the durations of the purging, vacuum creation, and recovery processes were 30, 500, and 270 s. At least three linked vacuum chambers must be synchronized and operated simultaneously to realize continuous water recovery.

Supersonic nozzle performance prediction considering the homogeneous-heterogeneous coupling spontaneous non-equilibrium condensation

Supersonic nozzles are widely applied in steam turbines and other industrial fields. Condensation occurs due to rapid expansion of steam flowing through a sonic nozzle. The process is affected by the presence of steam impurities. The primary purpose of this study is to investigate the impact of different heterogeneous particles (solid particles, tiny droplets and NaCl particles) at different concentrations on the non-equilibrium condensing flow, and to classify and calculate condensation losses and total static isentropic efficiency resulting from the non-equilibrium condensation phenomenon. First, the proposed non-equilibrium condensation model is estimated numerically using the Barschdorff nozzle, and the model accuracy is validated by comparing the results with existing experimental data. Second, the effect of different particle concentrations on several condensing flows is studied using the Barschdorff nozzle. The results show that homogeneous condensation will get weaker with an increase in the particle concentration in the vapour condensing flow with solid particles and NaCl particles. Moreover, homogeneous condensation will be slightly enhanced first and then weakened with an increase in the particle concentration in the vapour condensing flow with tiny droplets. The steam condensing flow with different heterogeneous particles at the same particle concentration and the process of pure steam condensation are analysed. The results show that impurity particles in steam have a significant impeding effect on the process of homogeneous condensation. The losses are classified in the Barschdorff nozzle, and the magnitude of the losses and the flow total static isentropic efficiency are estimated. As the particle concentration increases from 1014[1/kg] to 1015[1/kg], the total static isentropic efficiency of solid particles and tiny droplets increases by 12.8 % and 9.6 %, respectively, while the total static isentropic efficiency of NaCl particles decreases by 27.2 %. This indicates that an appropriate increase in the particle concentration can effectively reduce condensation losses and improve total static isentropic efficiency. The paper describes the effect of heterogeneous particles on the steam condensing flow, providing a reference for future research on heterogeneous condensation processes.

Гідродинамічне дослідження групи струменів рідини в апаратах із циліндричними розподільними пристроями

The analysis of existing studies regarding the process of steam condensation from a vapor-gas mixture on liquid jets allows us to conclude that the vast majority of them are experimental in nature, so the results of these studies can be correctly used only for the appropriate range of parameter changes of the liquid and gaseous phases. Also, the subject of research in them is mainly the hydrodynamic mode of a continuous liquid jet along its entire length. During theoretical and experimental studies, it was established that the shape of the jets flowing out of the cylindrical holes counter to the oncoming steam current differs from cylindrical shape, depends on the flow parameters, and is characterized by their rotation with intense wave formation on the jet surfaces. The jets are combined with each other with their subsequent disintegration along the current, dispersed and carried away with the steam current. Accordingly, it is incorrect to apply existing methods of heat transfer calculation to the analysis of heat transfer in this type of jets, only on solid jets of liquid, outside the investigated range of parameters. That is, using classical equations is impossible due to the complexity of calculating the cross-sectional area of jet groups flowing through cylindrical holes, and accordingly, the area of the heat exchange surface. Namely, it is impossible to use the traditional concept of the heat transfer coefficient as a parameter. Therefore, most of the existing calculation methods are based on using dimensionless complexes that describe the degree of change in the temperature of the liquid along the length of the jets under the appropriate geometric conditions. That is, without finding the limits of changes in the continuity of liquid jets, determining the limiting hydrodynamic modes using the existing methods of heat exchange calculation is incorrect.

A numerical study on film condensation of steam with non-condensable gas on a vertical plate

The film condensation of steam is very common in several industrial areas, such as condensers in power plants, seawater desalination, and air-conditioning systems. In some studies, the non-condensable gas and liquid film are overlooked for the sake of simplicity. To provide an integral computational scheme, in the present study, the film condensation of steam in the presence of non-condensable gas on a vertical plate has been simulated using a two-dimensional CFD model combining a wall condensation model and volume of fluid (VOF) model. After verification, the proposed computational scheme is used to simulate the steam condensation process, with the mass fractions of non-condensable gas varying from 5% to 45%. The results indicate that the concentration of non-condensable gas in the boundary layer decreases gradually with the condensation process, resulting in a decline in the synergy between temperature and velocity field. It can also be found that the fluctuation of the liquid film can influence the concentration distribution of the non-condensable gas layer. For cases with high concentrations of steam, the thermal resistance of liquid film can reach more than 20% of the total thermal resistance, which should not be ignored.

Influence of LiBr concentration in the generation of superheated vapor for a Hygroscopic Cycle

The novel proprietary Hygroscopic Cycle Technology (HCT) is a power cycle distinguished for using hygroscopic compoundswater mixtures as the working fluid to optimize the condensation process of the turbine exhaust steam by absorption phenomena. Previous works focused on the performance of the condensation/cooling section of the cycle as well as in the main improvements achieved by HCT in comparison to traditional thermal power generation cycles in terms of efficiency and profitability. Nevertheless, the thermodynamic characteristics of the steam generated from hygroscopic-water mixtures in the HCT boiler are yet to be studied. In this article, a theoretical analysis of temperature and pressure conditions of pure water steam generated from different concentrations of LiBr-water mixtures is carried out by using the Engineering Equation Solver (EES) software. Results show that LiBr-H2O mixtures display higher saturation temperatures than pure water, which enables the cycle to directly generate superheated vapor with no need for superheating equipment inside the boiler. This fact further improves the economic advantages previously shown by HCT, since erection, operation and maintenance costs related to the superheating process are avoided.

Experimental Investigation of Coolant Side Characteristic on the Performance of Air-Cooled Condenser Structured by Horizontal Flattened Tube

The steam condensation process has been experimentally investigated in an air-cooled condenser (ACC). The ACC has been designed and built using a flattened cross-section horizontal tube. The flattened tube has an internal dimension of 102 mm x 12 mm with 4030 mm length. A range of vacuum operating conditions are applied to operate the ACC. In the experiments, parameters such as vacuum pressure, saturated temperature, wall tube temperature, rate of heat transfer, and local average steam heat transfer coefficient have been considered along the flow direction with the variation of cooling water temperature. The experimental results revealed that the steam saturated temperature and the related pressure decrease with the reduction of the cooling water temperature, and the temperatures of the upper and lower parts of the horizontal flattened tube. The results also showed that the local steam condensation heat transfer coefficient decreases along with the direction of the flow, but it there is incrementing with the decreasing of saturated steam temperature at a certain range of cooling water temperature.

Experiments on Water Gravity Drainage Driven by Steam Injection into Elliptical Steam Chambers

Based on a recently published theoretical model, in this work we experimentally studied the problem of gravity water drainage due to continuous steam injection into an elliptical porous chamber made of glass beads and embedded in a metallic, quasi-2D, massive cold slab. This configuration mimics the process of steam condensation for a given time period during the growth stage of the steam-assisted gravity drainage (SAGD) process, a method used in the recovery of heavy and extra-heavy oil from homogeneous reservoirs. Our experiments validate the prediction of the theoretical model regarding the existence of an optimal injected steam mass flow rate per unit length, ϕopt, to achieve the maximum recovery of a condensate (water). We found that the recovery factor is close to 85% when measured as the percentage of the mass of water recovered with respect to the injected mass. Our results can be extended to actual oil-saturated reservoirs because the model involves the formation of a film of condensates close to the chamber edge that allows for gravity drainage of a water/oil emulsion into the recovery well.

Conversion of LDPE and PP plastic waste into fuel by pyrolysis method

This study aims to produce fuel from plastic waste and determine the physical properties of the fuel. Plastic waste used is mineral water bottles (polypropylene/PP) and plastic bags (low-density polyethylene/LDPE). The method used is an experimental method using pyrolysis. 1 kg of raw material is chopped before being put into the pyrolysis container. The container is then heated and turns the plastic into a liquid and then evaporates. The hot plastic vapor flows into a heat exchanger to be condensed. The cooling process uses water with a counter flow direction of the steam flow. The results of the steam condensation process are then analyzed for their physical properties. The fuel obtained from 1 kg of raw materials is 0.863-0.908 kg, with a density of 742 – 761 kg/m3. The kinematic viscosity of the fuel is between 1.75-1.93 cSt. Flash points 1-2 oC and fire points 8-9 oC with HHV of 44.6-46 MJ/kg. The volume of fuel from plastic bottles of mineral water is more and has a higher calorific value when compared to the fuel from plastic bags waste.

Optimization of Condenser Backwash Method to Maintain Condenser Performance During the Backwash Process in PLTGU Grati

The condenser is a device used to change the water vapor phase that has been used to rotate the turbine blade into a liquid phase by condensing it. When the condenser tube is dirty, it can disrupt the steam condensation process which affects the efficiency of the condenser. To overcome this problem a condenser backwash is carried out.  Condenser backwash has a good influence on unit efficiency but backwash activities also reduce production by decreasing vacuum condensers and steam turbine loads. When the vacuum condenser backwash process decreases + - 24 mmHg and the steam turbine load decreases + - 8 MW.The condenser backwash process is carried out from the control room with the observation of parameters from the local area or equipment. Backwash condensers are done one by one as needed. The condenser type in PLTGU Grati Block I is a type of crossflow with two sides, namely, side A and side B. Each side of the condenser has a different sequence backwash condition. This study will be carried out a backwash method that is different from the sequence of automatic sequences.In the normal condenser backwash activity of data table 3 we can know there is a decrease in steam turbine load ± 8MW and a decrease in vacuum ± 24 mmHg. This is because at a certain period the condenser performance is reduced because at the time of switching valve one side of the condenser is not irrigated by seawater so that the heat transfer in the condenser is reduced which has an impact on a load of steam turbine and vacuum condenser. After the research was obtained that the greater the opening of the valve inlet when the condenser backwash then the decrease in vacuum and steam turbine load decreased even no decrease in load.The backwash method that can be done to keep the vacuum condenser and steam turbine load stable is by maneuvering the valve inlet, outlet, and condenser backwash valve. The results of the analysis obtained were a more stable decrease in steam turbine production in 0 MW and a decrease in the vacuum of 14 mmHg.

The coupling process of steam condensation and falling film evaporation with non-condensable gas

For the steam condensation process inside a horizontal tube under small temperature difference, the operating parameters such as steam flow rate and temperature difference are narrowed in limited variation ranges to guarantee the high heat transfer performance. When the steam is mixed with non-condensable gas, the effective temperature difference shows more complexity compared with pure steam condensation. In this paper, the condensation process of the mixed steam in the tube cooled by the falling film evaporative seawater outside the tube is calculated with the steam mass flow rate of 2–9 kg/(m2·s), the evaporation temperature of the seawater of 50–70 °C, the total temperature difference of 2–4 °C and the inlet non-condensable gas (NCG) mass fraction of 1–4%. The mixed steam condensation heat transfer model combined with distributed parameter model is established and validated to couple the heat transfer on both sides of the tube. The local saturation temperature depression of the mixed steam condensation is divided into two factors, one caused by the flow resistance and the other caused by the non-condensable gas mass fraction. Both types of saturation temperature depression increase with the increase of the inlet non-condensable gas mass fraction. The mass flow rate and the temperature difference are found to have more significant impact on the total temperature depression on the saturation temperature. Besides, the saturation temperature is found to have no significant impact on the condensation heat transfer of the mixed steam. The mass flow rate corresponding to the maximum heat transfer of the heat transfer tube is presented.

Carbon dioxide extraction from marine engine exhaust gases by the method of adsorption

The purpose of the article is to analyze a method of marine engine exhaust gases carbon dioxide purification by means of adsorption which proceeds in parallel with the process of steam condensation formed during the combustion of fuel in a diesel cylinder. The scheme of afacility of advance efficiency for marine engine exhaust gases purifying is given. This facility works with the use of granulated slag pumice as an adsorbent for exhaust gases harmful components and ozone as an oxidant in order to accelerate the purification process. A full-scale test was conducted in order to check the efficiency of the facility and evaluate its effectiveness in engine discharge gases purifying. Aformula is received for a conduction of a calculation of the carbon dioxide purifying degree in the experimental facility which contains in the engine exhaust gases depending on a crankshaft rotation speed.

Reduction entropy generation and condensation by NaCl particle injection in wet steam supersonic nozzle

The supersonic nozzle is very often used in many technical applications, such as fluid-flow machines or devices. If the medium flowing through a supersonic nozzle is a moist gas, moist air or wet steam, non-equilibrium condensation must occur. Such mediums usually contain impurities which affect the condensation phenomenon. The main purpose of this research is a numerical study on the effect of the content of impurities in steam on the non-equilibrium condensation phenomenon. In order to achieve this purpose, salt (NaCl) is used. Sodium chloride (NaCl) is a very common steam impurity. It may occur in a soluble or crystal form. Different concentrations of salt are considered as the input quantity. The results show that the process of steam condensation on salt particles has a significant impact on two-phase variables and flow parameters. In the presence of salt, steam condensation starts whenever the supersaturation ratio is above one. Latent heat of the condensation changes the flow pattern and reduces the nucleation rate and water droplet production. The presence of 1015 particles of salt reduces the outlet average liquid mass fraction and entropy generation by 14.5 % and 15.2 % respectively. The research results prove that steam impurities have a significant impact on non-equilibrium condensation.

Pressure drop in two phase flow of condensing air-steam mixture inside PHE channels formed by plates with corrugations of different geometries

The pressure drop in the two-phase condensing flow of air-steam mixture inside channels of plate heat exchanger (PHE) with different geometries of corrugations is studied based on experiments and one-dimensional mathematical modelling. The experiments were made with five samples of the PHE channel. In three of them plates with corrugations inclination angles 30, 45 and 60° at the same height of corrugations 5 mm. The other two plates corrugations height was 7.5 and 10 mm at the same pitch to height ratio and inclination angle of 60°. The correlation of pressure drop data for all experimental samples by average process parameters is not able to give acceptable accuracy. The correlation for local pressure gradients in two-phase condensing flow is identified using a developed one-dimensional mathematical model. The model of separated flows of phases is employed for channel zones close to air-steam mixture entrance. Further on channel length with an increase of liquid phase quantities, its combination with the dispersed annular flow structure model is used. The proposed equations can be included in the mathematical model when designing PHE and optimising the geometrical form of corrugations on its plates for steam condensation processes from an air-steam mixture.

Development of a Condensation Model and a New Design of a Condensation Hood—Numerical and Experimental Study

The development of a numerical model and design for the innovative construction of a heat exchanger (HE) used in a condensation hood (being a part of the combi-steamer) are described in this work. The model covers an air-steam flow, heat transfer, and a steam condensation process. The last two processes were implemented with the use of an in-house model introduced via User Defined Functions (UDF). As the condensate volume is negligible compared to the steam, the proposed model removes the condensate from the domain. This approach enabled the usage of a single-phase flow for both air and steam using a species transport model. As a consequence, a significant mesh and computation time reduction were achieved. The new heat exchanger is characterised by reorganised fluid flow and by externally finned pipes (contrary to the original construction, where internally finned pipes were used). This allowed a reduction in the number of the pipes from 48 to 5, which significantly simplifies construction and manufacturing process of the HE. The redesigned HE was tested in two cases: one simulating normal working conditions with a combi-steamer, the other with extremely high heat load. Measurement data showed that the numerical model predicted condensate mass flow rate (3.67 g/s computed and 3.56 g/s measured) and that the condensation capability increased at least by 15% when compared to the original HE design.

Experimental Study of Steam Injection into a Water Stream for Milk Sterilization

Steam injection into milk stream is a frugal method for milk sterilization. In this paper, the steam injection into a steady liquid water stream (instead of milk stream) is experimentally investigated. A transparent mixing chamber is fabricated using which the variations in steam condensation process are photographed by a high-speed camera. The length of the steam plume in water is determined using image processing of the still images of the phenomenon. The factors affecting the quality of steam condensation are studied. Increasing the chamber pressure reduces the steam plume length which in turn improves the quality of direct contact condensation. Decreasing the liquid water flow rate has an adverse effect on the phenomenon where the steam plume length is increased. It is also found that injecting the steam in a multi-stage configuration results in a reduction of the steam plume length, thereby, improving the condensation process.

Dynamic model to predict heat-induced protein denaturation and fouling in a Direct Contact Steam Condensation process

High heat treatment, using Direct Contact Condensation (DCC), is applied in the production of dairy products to ensure a high level of food safety. During this process a protein rich deposit layer can be formed causing fouling of the system resulting in a loss of effective production time and an increase in cleaning cycles. The dynamics of the heat treatment process is modelled, including the description of the pre-heating step with two laminar flow tubular heat-exchangers followed by a DCC. In this system the bulk reactions for whey proteins are modelled using unfolding, re-folding and aggregation kinetics. The formation of the deposit layer is described in the segment after the DCC using a flow averaged model incorporating diffusion of species through the mass boundary layer as well as adsorption to the wall and desorption from the wall. The desorption kinetics are key as the protein deposit layer releases from the wall once the wall friction increases due to the decreasing area available for throughflow. The model shows good agreement with experimental data and is capable of capturing the process dynamics, both for the heat exchanger and the DCC. The deposit layer formation model is in agreement with the trend observed in the experimental data but is not fully capturing the process dynamics.

Influence of Cooling Medium Flow Character on the Operation of Heat Exchangers with Steam Condensation Inside Tubes

The influence of the character of cooling medium motion in a heat exchanging apparatus on the process of steam condensation in the latter is considered in the cases of cross flow past a tube bank in the apparatus, longitudinal flow past tubes in the bank in the regimes of forward flow and countercurrent flow, superheated steam condensation, and of nonuniform distribution of the cooling medium in different zones of the apparatus. It has been established that in the case of cross flow past the first rows of the tube bank, cooling medium zones with reduced heat transfer efficiency appear in the apparatus. The dependence of the pressure losses by the steam, which condenses in a heat exchanger in regimes of countercurrent flow, forward flow, and cross flow, is investigated. Experimental data on the superheated steam temperature have been obtained and generalized. The positive influence of the throttle on the line of removal of the steam–air mixture to a steam–jet ejector in nonuniform cooling of the parallel channels of the condenser has been established experimentally, and the presence of the optimal size of the throttle on the line of removal of noncondensing gases has been confirmed.

Heat transfer characteristics of in-tube steam condensation process under stratified flow

For stratified flow condensation process, the heat transfer mechanisms in the film condensation zone above the vapour-liquid interface and the condensate zone below the interface shows significant differences. In the multi-effect evaporation device, due to the high sensitivity of the thermal performance to the variation of the heat transfer parameters, the heat transfer parameters distributions in the film condensation zone and in the condensate zone are worth exploring. In this paper, a validated distributed parameter model was established to simulate the heat transfer and flow process in a single tube of the falling film evaporator. The variation of the heat flux in the condensate zone was presented under various operating conditions. The concept of the effective tube length and the partition map of the in-tube condensation heat transfer process were proposed for the better understanding of the flow and heat transfer process. Results show that the heat transfer in the condensate zone to the total heat transfer can accounts for more than 10% of the total heat transfer, thus cannot be neglected. For the design of falling film evaporator, the condensation heat transfer process in the tube should be located in the high-efficiency heat transfer section. The steam mass flow rate, heat transfer temperature difference and the length of the heat transfer tube should matched to each other to guarantee the condensation heat transfer process be located in the high-efficiency heat transfer zone.