Non-condensable Gas Concentration Research Articles

Assessment of the RELAP5/MOD3.3 code for condensation in the presence of air using experimental data and theoretical model

This study has been performed to assess the condensation module of RELAP5/MOD3.3 code, which is still widely used in the nuclear industry, for in-tube condensation in the presence on noncondensable gas under forced convection conditions. The experimental works, conducted at the Massachusetts Institute of Technology (MIT), the University of California-Berkeley (UCB), and the Middle East Technical University (METU), have been utilized in order to realize the assessment process in the wide range of parameters. To investigate the relationship between mixture Reynolds number and interface temperature, the theoretical model based on the energy balance at the interface has been developed and the results have been compared with the RELAP5/MOD3.3 findings. The entrance, interfacial waviness, suction and interfacial shear stress effects have been considered in the modeling to obtain accurate estimation of the heat transfer coefficient, particularly at the entrance region. The comparisons show that the proposed model predicts the heat transfer coefficient reasonably well with a maximum mean deviation of 17.3% for the simulated cases. On the other hand, RELAP5/Mod3.3 cannot evaluate the relationship between the mixture Reynolds number and the interface noncondensable gas concentration and predicts the heat transfer coefficients with the mean deviations around 150%, 85% and 50% for the METU, the UCB and the MIT databases, respectively. The findings reveal that the RELAP5/MOD3.3’s capability to simulate the condensation with noncondensable gas phenomenon drastically decreases with increasing mixture Reynolds number.

A study on catalytic pyrolysis of biomass with Y-zeolite based FCC catalyst using response surface methodology

A response surface methodology (RSM) was used to investigate the influence of temperature, weight hourly space velocity (WHSV) and vapor residence time on the catalytic pyrolysis of hybrid poplar wood using Y-zeolite based FCC catalyst in a 50mm bubbling fluidized bed reactor. The levels of the independent variables were: temperature (400–600°C), WHSV (1–3h−1), and vapor residence time (3–6s). The Box–Behnken experimental design was used and a total number of 15 experimental runs including 3 center runs were generated. The analysis of variance (ANOVA) at 95% confidence interval was performed with Minitab 16 software package and reduced models were generated for the prediction of the responses. It was found that higher levels of WHSV (>1h−1) with shorter vapor residence time and moderate temperatures (⩽500°C) favor higher yield of organic liquid fraction. Also, higher temperature (>500°C) and WHSV (>2h−1) reduces the formation of coke/char. The catalytic pyrolysis with the Y-zeolite based FCC catalysts at high temperatures (>500°C) and long residence time enhanced the cracking of the primary vapors and increased the formation of CO, H2 and CH4. The catalytic process at higher temperatures (>500°C) and lower WHSV (⩽2h−1) decreased the oxygen content and increased the viscosity of the bio-oil. The reaction temperature was the most significant independent variable on char/coke yield, concentration of non-condensable gases, carbon content, oxygen content, pH and viscosity of the bio-oils. The WHSV was found to be the most important significant independent variable that affected the yield of organic liquid and the formation of water. The models for the prediction of the responses with the exception of viscosity were adequate and statistically significant.

Wetting Mode Evolution of Steam Dropwise Condensation on Superhydrophobic Surface in the Presence of Noncondensable Gas

It is well known that heat transfer in dropwise condensation (DWC) is superior to that in filmwise condensation (FWC) by at least one order of magnitude. Surfaces with larger contact angle (CA) can promote DWC heat transfer due to the formation of “bare” condensation surface caused by the rapid removal of large condensate droplets and high surface replenishment frequency. Superhydrophobic surfaces with high contact angle (> 150°) of water and low contact angle hysteresis (< 5°) seem to be an ideal condensing surface to promote DWC and enhance heat transfer, in particular, for the steam-air mixture vapor. In the present paper, steam DWC heat transfer characteristics in the presence of noncondensable gas (NCG) were investigated experimentally on superhydrophobic and hydrophobic surfaces including the wetting mode evolution on the roughness-induced superhydrophobic surface. It was found that with increasing NCG concentration, the droplet conducts a transition from the Wenzel to Cassie-Baxter mode. And a new condensate wetting mode—a condensate sinkage mode—was observed, which can help to explain the effect of NCG on the condensation heat transfer performance of steam-air mixture on a roughness-induced superhydrophobic SAM-1 surface.

不凝縮性ガス存在下における滴状凝縮熱伝達に関する研究

Dropwise condensation heat transfer coefficients can be calculated from the density of drop-size distribution and the growth rate of drops. In the case of steam including non-condensable gases the heat transfer coefficient can be calculated. The purpose of this study is to investigate the effect of pressure and non-condensable gas concentration for dropwise condensation heat transfer. Furthermore, the validity of the density of drop-size distribution formula in the presence of non-condensable gases proposed by Tanaka is evaluated. Heat transfer coefficients are measured in the air mole fraction range between 1 % and 25 % and in the pressure range between 0.1 MPa and 0.4 MPa. And drop diameters and drop numbers are measured using image analysis. As a result, the theoretical formula proposed by Tanaka is applicable when non-condensable gas concentration is 25 % or less.

Condensation in a vertical tube bundle passive condenser – Part 1: Through flow condensation

An experimental study and a boundary layer analysis were performed for the steam condensation in a vertical tube bundle passive condenser operating in a through flow mode. Four condenser tubes were submerged in a water pool and the heat from the condenser tube was removed through boiling. Experimental data were obtained for various system pressures (100–170 kPa), inlet steam flow rates (15–47 g/s) and non-condensable gas concentration (0–15%). The experimental results showed substantial deterioration in condensation when non-condensable gas was present. With increase in steam flow rate and system pressure the condensate rate increased. The boundary layer thickness and non-condensable gas concentration increased along the condenser tube length.

Condensation of a gas-vapor mixture in an electric field

Condensation of a gas-vapor mixture in a direct electric field is discussed in this paper. At a noncondensable gas concentration of 5%, an approximately two-fold increase in the condensed liquid amount is obtained. The condensation process enhancement is explained by the cooperative effect of the condensate film turbulization and the decrease in the diffusion resistance of the noncondensable gas layer in an electric field. The obtained results can be used for the design of electrohydrodynamic generators and compact vapor condensers.

Turbulent film condensation in the presence of non-condensable gases over a horizontal tube

A numerical model is presented for studying turbulent film condensation in the presence of non-condensable gases over a horizontal tube. Inertia, pressure gradient are included in this analysis, and the influence of turbulence in the proposed two-phase model is considered. The numerical results demonstrate that a very small bulk concentration of non-condensable gas reduces the heat transfer coefficient and film thickness considerably. The local heat flux and film thickness increase as tube surface temperature decreases at any bulk concentration of non-condensable gas. Moreover, inlet velocity increases as film thickness decreases and heat flux increases, a numerical result in agreement with that obtained by Nusselt. Numerical results indicate that average dimensionless heat transfer coefficients are in good agreement with theoretical and experimental data.

Optimization of downhole pump setting depths in liquid-dominated geothermal systems: A case study on the Balcova-Narlidere field, Turkey

Downhole pumps are being used increasingly more often in low-enthalpy geothermal wells. The depth at which these pumps are installed depends on the physical and chemical characteristics of the geothermal fluid, the production flow rate, and the reservoir pressure and permeability. In this study we have investigated the factors affecting pump setting depths in low-temperature, liquid-dominated geothermal systems and defined the relationship between flow rate and pressure drawdown based on multi-rate test results. The methodology proposed was applied to the Balcova-Narlidere geothermal field, Turkey. It was found that the most important parameters for determining the capacity and setting depth of a downhole pump were flow performance, non-condensable gas concentration, and temperature. The implementation of the methodology is illustrated.

Condensation heat transfer enhancement in the presence of non-condensable gas using the interfacial effect of dropwise condensation

Heat transfer characteristics of dropwise condensation (DWC) were experimentally studied on a vertical plate for a variety of non-condensable gas (NCG) concentration, saturation pressure, and surface sub-cooling degree. As the heat transfer performance was dominated by the vapor diffusion process near the interface of the gas–liquid within the gas phase, the additional thermal resistance of the coating layer may not be strictly limited, a fluorocarbon coating was applied to promote dropwise condensation mode. Compared with the traditional filmwise condensation (FWC), heat and mass transfer with NCG can be enhanced with the dropwise condensation mode. In the present paper, the effect of condensate liquid resistance should not be regarded as the most vital factor to explain the results, but the vapor diffusion process. This is attributed to the liquid–vapor interfacial perturbation motion caused by coalescence and departure of condensate droplets. The results also demonstrated that the feature of droplets departure is the dominant factor for the steam–air condensation heat transfer enhancement.

Experimental verification of the fast reactor safety analysis code SIMMER-III for transient bubble behavior with condensation

Experimental verification of a reactor safety analysis code, SIMMER-III, was undertaken for transient behaviors of large-scale bubbles with condensation. The present study aimed to verify the code for numerical simulations of relatively short-time-scale multi-phase, multi-component hydraulic problems. Among these, vaporization and condensation, or simultaneous heat and mass transfer, play important roles. In this study, a series of transient bubble behavior experiments dedicated to condensation phenomena with noncondensable gases was carried out. In the experiments, a pressurized mixture of noncondensable gas and steam was discharged as a large-scale single bubble into a cylindrical pool filled with stagnant subcooled water. The concentration of noncondensable gas was taken as an experimental parameter as was the species of noncondensable gas. The characteristics of transient behavior of large-scale bubbles with condensation observed in the experiments were estimated through experimental analyses using SIMMER-III. In the experiments with steam condensation, dispersion of the gas mixture discharged into the liquid pool was accompanied by vapor condensation at the bubble surface. SIMMER-III simulations suggested that the noncondensable gas had a less inhibiting effect on the condensation of large-scale bubbles. This is a different characteristic to that of the quasi-steady condensation of small-scale bubbles observed in our previous experiments.

Condensation heat transfer with noncondensable gas for passive containment cooling of nuclear reactors

Noncondensable gases that come from the containment and the interaction of cladding and steam during a severe accident deteriorate a passive containment cooling system's performance by degrading the heat transfer capabilities of the condensers in passive containment cooling systems. This work contributes to the area of modeling condensation heat transfer with noncondensable gases in integral facilities. Previously existing correlations and models are for the through-flow of the mixture of steam and the noncondensable gases and this may not be applicable to passive containment cooling systems where there is no clear passage for the steam to escape. This work presents a condensation heat transfer model for the downward cocurrent flow of a steam/air mixture through a condenser tube, taking into account the atypical characteristics of the passive containment cooling system. An empirical model is developed that depends on the inlet conditions, including the mixture Reynolds number and noncondensable gas concentration.

Three-dimensional numerical simulation of non-condensables accumulation induced by steam condensation in a non-vented pipeline

A substantial increase of the concentration of non-condensable gases in the mixture with steam can occur in a non-vented pipeline due to the condensation. This phenomenon is investigated with the thermal-hydraulic and physicochemical code HELIO. The hydrogen and oxygen accumulation is simulated and analyzed for a real non-vented steam pipeline of the nuclear power plant. The results show the propagation of non-condensables concentration front, the temperature and velocity field of the steam–non-condensables mixture, and the velocity and thickness of the condensate that drains on the pipeline’s inner walls. The gas mixture temperature is verified with measurements from a full size test facility. The presented modelling approach and numerical results are unique regarding the simultaneous solution of the heat and mass transfer in the system consisting of the steam–non-condensable gases mixture and the thin liquid film on the pipe’s wall.

Effect of noncondensable gas in a vertical tube condenser

An experimental study is performed to investigate the effects of noncondensable (NC) gas in the steam condensing system. A vertical condenser tube is submerged in a water pool where the heat from the condenser tube is removed by boiling heat transfer. The design of the test section is based on the passive condenser system in an advanced boiling water nuclear power reactor. Data are obtained for various process parameters, such as inlet steam flow rate, noncondensable gas concentration, and system pressure. Degradation of the condensing performance with increasing noncondensable gas is investigated. The condensation heat transfer coefficient and heat transfer rate decrease with noncondensable gas. The condensation heat transfer rate is enhanced by increasing the inlet steam flow rate and the pressure. The condensation heat transfer coefficient increases with the inlet steam flow rate, however, decreases with the system pressure. For the condenser submerged in a water pool with saturated condition, the strong primary pressure dependency is observed.

AN EXPERIMENTAL STUDY ON THE EFFECT OF NON CONDENSABLE GAS FOR SOLUTAL MARANGONI CONDENSATION HEAT TRANSFER

The condensation heat transfer characteristic curves for a ternary vapor mixture of water, ethanol, and air (or nitrogen) under several ethanol concentrations and relatively low concentrations of air (or nitrogen) were measured. The effect of non-condensable gas on several different domains in the condensation curves was discussed. The effect of non-condensable gas in the domains controlled by the diffusion resistance and the filmwise condensation was not notable; whereas that in the domain dominated by the condensate resistance of dropwise mode was remarkable. Moreover, variations due to changes in non-condensable gas concentration of several characteristic points representing the curves were discussed.

Flue Gas Injection Into a Mature SAGD Steam Chamber at the Dover Project (Formerly UTF)

Abstract The Dover Project (formerly the Underground Test Facility) is the world's first field pilot of the Steam Assisted Gravity Drainage (SAGD) process using dual horizontal well pairs to recover bitumen. There have been four phases of SAGD piloting at the Dover site thus far. The Phase B pilot, which consists of three 500 m long horizontal well pairs spaced 70 m laterally apart, has been in continuous operation since early 1993. Phase B reached the peak production rate of 300 m3/d or 100 m3/d per well pair on average in the middle of 1994. After sustaining the peak rate for about two years, the production has been in decline with a steady increase in steam-oil ratio. Research carried out in the past few years suggested that the addition of a suitable amount of non-condensable gases (NCG) would be an effective method to wind-down the steam chamber. It provides an economic means to continue bitumen production by utilizing the large amount of heat stored in the SAGD chamber. Beginning in April 1998, a small amount of natural gas was added continuously to the steam injection. The concentration of NCG has increased steadily in the past 3.5 years. The resulting performance has been better than initially expected. Based on the success of this NCG-steam wind-down strategy, a four-month flue gas injection test was conducted in 2001 to investigate the possibility of using the more cost-effective flue gas, rather than natural gas as an injectant. This paper summarizes the rationale for selecting the NCG-steam wind-down strategy, the field implementation of the flue gas injection test, and the resulting pilot performance. The successful implementation of this technology will have a profound impact on the overall process economics. Introduction The Dover Project is an in situ bitumen recovery facility on the Oil Sands Lease Number 328 located 70 km northwest of the City of Fort McMurray. It was initiated by Alberta Oil Sands Technology and Research Authority (AOSTRA) in 1984 and was ater joined by industry participants to pilot the SAGD processsing dual horizontal wells. The Dover Project Area is located in eight sections of land at the extreme eastern edge of the lease, as shown in Figure 1. To the immediate east of Dover is Petro-Canada's MacKay River Project, which is expected to produce 30,000 BOPD using the SAGD process in 2003. Several papers(1–3) have been published to describe, in detail, the Dover Project from the beginning until mid-1997. The following is a brief summary. FIGURE 1: Dover project area. Available in Full Paper. The first phase of testing, Phase A, involved the drilling of horizontal wells from a limestone tunnel network located about 20 m below the oil sand formation. These well pairs had a horizontal length of about 60 m and were spaced 25 m apart, as shown in Figure 2. They were operated from 1987 to 1991. Encouraged by the results from Phase A, the Project proceeded to the secondphase of piloting in late 1991.

Effect of Non-Condensable Gas Mass Fraction on Condensation Heat Transfer for Water-Ethanol Vapor Mixture

The condensation heat transfer characteristic curves for a ternary vapor mixture of water, ethanol and air (or nitrogen) under several ethanol concentrations and relatively low concentrations of air (or nitrogen) were measured. The effect of non-condensable gas on several different domains in the condensation curves was discussed. The effect of non-condensable gas in the domains controlled by the diffusion resistance and the filmwise condensation was not notable; whereas that in the domain dominated by the condensate resistance of dropwise mode was remarkable. Moreover, variations due to changes in non-condensable gas concentration of several characteristic points representing the curves were discussed.

A two-phase model for laminar film condensation from steam-air mixtures in vertical parallel-plate channels

Detailed results are presented for laminar film condensation from steam-air mixtures flowing downward in vertical flat-plate channels. The mixture flow is laminar and saturation conditions prevail at the inlet. A fully coupled implicit numerical approach is used that achieves excellent convergence behavior, even for high inlet gas mass fractions. The detailed results include velocity, temperature, and gas mass fraction profiles, as well as axial variations of film thickness, pressure gradient and Nusselt number. The effects of a wide range of changes in the four independent variables (the inlet-to-wall temperature difference and the inlet values of gas concentration, Reynolds number, and pressure) on the film thickness, axial pressure gradient, and the local and average Nusselt numbers are carefully examined. It was found that increases in inlet concentration of noncondensable gas caused significant decreases in the film thickness, local Nusselt number, and axial pressure gradient. An analytical solution for the film thickness and velocity field at the end of condensation path was developed and shown to be the asymptotic value of the numerical results for large distances along the channel.

B308 EFFECT OF NON-CONDENSABLE GAS MASS FRACTION ON CONDENSATION HEAT TRANSFER FOR WATER-ETHANOL VAPOR MIXTURE

The condensation heat transfer characteristics curves for a ternary vapour mixture of water, ethanol and air (or nitrogen) for several ethanol concentrations and relatively low concentrations of air (or nitrogen) were measured. The effect of non-condensable gas on several different domains in the condensation curves was discussed. The effect of non-condensable gas in the domains controlled by the diffusion resistance and the filmwise condensation was notable; whereas that in the domain dominated by the condensate resistance of dropwise mode was remarkable. Moreover, variations due to changes in non-condensable gas concentration of several characteristics points representing the curves were discussed.

액체로켓 추진제 공급계에서 캐비테이션 벤튜리의 유량 제어 특성

액체로켓 추진제 공급장치에 정착된 캐비테이션 벤튜리의 유량 제어 특성을 해석하였다. 해석에는 실험과 수치해석이 병행되었으며 캐비테이션이 존재하는 유동에서 두 결과의 유량 차이는 약 10%로 나타났다. 벤튜리 상류의 압력을 <TEX>$22.8{\times}10^5$</TEX>pa로 일정하게 유지하고 하류의 압력을 변동시켰을 때 <TEX>$3{\times}10^5$</TEX>pa 이상의 압력 차이에 대하여 유량이 증가하지 않음을 확인하였다. 비응축 기체의 농도 변화에 의하여 벤튜리 내부에 발생하는 증기의 분포는 크게 달라지지만 유량은 같은 수준이 유지되어 비응축 기체의 농도가 1.5PPM에서 150PPM로 커질 경우, 유량이 약 2% 감소하였다. 이는 작동유체가 포함하고 있는 비응축 기체의 팽창과 생성된 증기가 압력 회복을 저해하는 영향이 유사하기 때문으로 풀이된다. Characteristics of flow rate control has been studied for a cavitating venturi adopted in a liquid rocket propellant feed system. Both experiment and numerical simulation have been performed to give about 10% discrepancy of mass flow rate for cavitating flow regime. Mass flow rate is confirmed to be saturated for pressure difference higher than <TEX>$3{\times}10^5$</TEX>pa when the upstream pressure is fixed to <TEX>$22.8{\times}10^5$</TEX>pa and the downstream pressure is varied. The evaporation amount depends substantially to non-condensable gas concentration. However the mass flow rate characteristics is relatively insensitive to the mass fraction of non-condensable gas. So it reduces by only 2% when the non-condensable gas concentration is increased from 1.5PPM to 150PPM. From the previous comparison the expansion of the non-condensable gas and the evaporation of liquid are verified to gave same effect to the pressure recovery pattern.

Experimental Investigation of Mixing Phenomena inside a Concrete Containment Cooled by an Innovative Passive System

Several advanced nuclear plant concepts are characterized by the use of innovative cooling systems that remove the heat released inside the containment following a hypothetical accident, such as a loss-of-coolant accident, through passive heat transfer mechanisms. The design and installation of a localized passive containment cooling system (PCCS) inside a double-wall concrete containment requires the reliable knowledge of temporal and spatial distribution of noncondensable gas concentration, especially hydrogen, in a multicompartment geometry. Testing was conducted in the Large-Scale Containment Test Facility located at the Westinghouse Science and Technology Center in Pittsburgh, and the testing was modified to simulate in approximately one-tenth scale the main features of a concrete containment, designed by the Italian National Electric Utility (ENEL), in which the heat is removed through internal heat exchangers (HX) located in the dome region, and connected by an intermediate fluid loop to external HXs placed outside the double barrier concrete containment. No active component like pumps or human intervention are required for the operation of the system. The facility instrumentation, the test program, and the experimental results are described along with the first results obtained in the application of the FUMO code to the analysis of these experimental tests. The experimental data measured during the tests include temperature distributions inside the containment, helium concentrations at four internal locations, and laser Doppler anemometer measures to determine the atmosphere mixing under different simulated accident conditions. The experimental results indicate that helium, which simulates the hydrogen that may be released during some accident sequences, is distributed rather homogeneously inside the facility. The very good mixing exhibited by the helium indicates that the localized PCCS induces efficient convective motions inside the containment atmosphere, and this is a positive indication for safety analysis.