Amount Of Non-condensable Gas Research Articles

Physical Simulation of Steam Absorption Characteristics in Horizontal Wells of Super Heavy Oil Reservoir

In the process of dual Horizontal well SAGD development of super heavy oil, the steam absorption balance of upper horizontal steam injection well is an important factor to determine the development effect of SAGD. The factors affecting the steam absorption of upper horizontal wells involve reservoir permeability, steam injection technology, steam injection parameters, etc. The physical simulation method is used to study the influence degree of each specific factor and improvement measures. Based on the similarity criterion, the reservoir scale model is designed and made according to the oilfield prototype, and the simulation experiment is carried out on the steam absorption characteristics and influencing factors along the horizontal wellbore. The experimental results show that the steam injection rate, non condensable gas, the location of the steam injection string and the reservoir permeability have great effects on the steam absorption of the reservoir. The heating uniformity along the horizontal well can be improved by properly increasing the steam injection speed, adding a certain amount of non condensable gas to the steam, and the position of the steam injection string end in the relatively low permeability area of the reservoir. This achievement has a strong guiding significance for improving the steam absorption balance of horizontal wells and improving the development level of dual level SAGD.

Experimental study of non-condensable gas effects on sonic limit of sodium heat pipe

Due to unexpected gas leakage and long-term operation, the non-condensable gas (NCG) inevitably exists in high-temperature alkali metal heat pipe. Previous studies have mainly focused on its influences on startup and steady state operation characteristics of heat pipes. However, few of them conducted experiments to study the effects of NCG on sonic limit, which usually occurs during heat pipe startup or during steady state operation when the heat transfer coefficient at condenser section is high. In present work, experimental and analytical studies are conducted to the explore the effects of NCG on sonic limit of sodium heat pipes. With the heating power ranging from 500 to 1400 W, the sonic limit of 1 m-long sodium heat pipes with artery wick and axial groove wick are obtained based on oil-cooling system, which can widely adjust the cooling capacity at condenser section. The amount of NCG in heat pipe is estimated by Heat Pipe Transient Analysis Code (HPTRAN) and verified by experimental data. It is found that the existence of NCG in heat pipe leads to the decrease of maximum heat transfer rate under sonic limit. The mechanism of NCG effects on sonic limit is discussed based on phenomenological analysis. By introducing the added back pressure, a modified model to predict sonic limit considering NCG effect is proposed and the comparison with experimental data shows good agreements.

Thermal modeling and simulation of a single-flash geothermal power plant involving non-condensable gas: a case study of Kamojang geothermal field in Garut, West Java, Indonesia

The presence of non-condensable gases (NCGs) in a geothermal fluid disrupts the vacuum process in the condenser, reducing turbine efficiency and decreasing the total power output of the geothermal power plant (GPP). Therefore, to optimize the thermodynamic efficiency of a GPP, NCGs should be removed using a gas removal system. Since there is a substantial lack of design and simulation software for a GPP including NCG removal alternatives, in this study, we aimed to model and develop a software-based interface to simulate mass and energy balance involving an NCG fraction in a single-flash GPP as well as examine the thermodynamic performance of the gas removal system, which is the most important step in the planning and designing phase of a GPP. This software was validated using outputs of Kamojang GPP Units 2, 3, and 4 located at Kamojang geothermal field, Garut, West Java, Indonesia. Units 2 and 3 use two ejectors which are installed in series, and Unit 4 utilizes a hybrid system (HS) that is mostly a combination of vacuum pumps and a steam jet ejector (SJE). Our results showed that Kamojang GPP Units 2 and 3 generate 55.295 MW of power with an absolute error of 0.53%, whereas Unit 4 generates 60.218 MW of power with a 0.36% absolute error concerning the field data. These results correspond with the expected minimum error; therefore, our model’s parameters are considered valid and can be used for simulation. We found that using the simulation, the total steam saved by the HS at Kamojang GPP Units 2 and 3 was 534 kW. Furthermore, the net power production was reduced by 1.6% for the HS and 2.03% for the SJE with every 1% increase in the NCG fraction. The power requirement of the vacuum pumps remained less than the power generated by the motive steam which the ejector requires to dispose of the same amount of NCG, indicating that Kamojang GPP Units 2 and 3 will be more efficient if an HS is used.

Machine-Learning Approach for Forecasting Steam-Assisted Gravity-Drainage Performance in the Presence of Noncondensable Gases.

Steam-assisted gravity drainage (SAGD) is an effective enhanced oil recovery method for heavy oil reservoirs. The addition of certain amounts of noncondensable gases (NCG) may reduce the steam consumption, yet this requires new design-related decisions to be made. In this study, we aimed to develop a machine-learning-based forecasting model that can help in the design of SAGD applications with NCG. Experiments with or without carbon dioxide (CO2) or n-butane (n-C4H10) mixed with steam were performed in a scaled physical model to explore SAGD mechanisms. The model was filled with crushed limestone that was premixed with heavy oil of 12.4° API gravity. Throughout the experiments, temperature, pressure, and production were continuously monitored. The experimental results were used to train neural-network models that can predict oil recovery (%) and cumulative steam–oil ratio (CSOR). The input parameters included injected gas composition, prior saturation with CO2 or n-C4H10, separation between wells, and pore volume injected. Among different neural-network architectures tested, a 3-hidden-layer structure with 40, 30, and 20 neurons was chosen as the forecasting model. The model was able to predict oil recovery and CSOR with R2 values of 0.98 and 0.95, respectively. Variable importance analysis indicated that pore volume injected, distance between wells, and prior CO2 saturation are the most critical parameters that would affect the performance, in agreement with the experiments.

A novel method for removing noncondensable gas from loop heat pipe

Noncondensable gas (NCG) is a critical issue in loop heat pipes (LHPs) for space missions and can arise due to plenty of reasons. Compensation chamber (CC) of an LHP, being a nearly stagnant point, accumulates NCG that arises due to any reason. NCG in an LHP intended for space use should be removed before its hermetic sealing itself. In this paper, a novel method is presented for the first time to completely remove NCG from LHPs through a series of attempts using a simple setup consisting of a pressure sensor, a rough vacuum pump and a metering valve connected to the CC. The method is demonstrated on an LHP with flat evaporator with acetone as working fluid and air as NCG. When the LHP operates, a certain amount of NCG is removed from the CC through the vacuum pump by momentarily opening and closing the metering valve in each attempt. Through a series of test runs, based on a decrease in the operating temperature and an increase in the maximum heat transport prior to deprime in each test run with reference to those of the previous test run, it is ascertained that a certain amount of NCG is removed in each attempt. A unique model is also proposed to predict the NCG mass based on the CC pressure and the predicted CC liquid level. Results of the proposed model are validated with those of previous experiments in the LHP containing capacitance gauge for CC liquid level measurement.

Energy, exergy, economic and environmental (4E) analyses of a geothermal power plant with NCGs reinjection

In this study, a conceptual geothermal power plant with Non-Condensable Gases (NCGs) reinjection is analyzed from energy, exergy, exergo-economic, and environmental perspectives. The cycle is evaluated in considering both subcritical and supercritical working conditions. A sensitivity analysis comprising the variation of condensing temperature, turbine inlet pressure, and amount of NCGs within the geofluid is performed to assess the system performance from the thermodynamic, economic, and environmental points of view. The exergy efficiency results for the supercritical and the subcritical cycles are 52% and 50.5%, respectively. Results showed increasing the condensing temperature decreases exergy efficiency, net power, and exergetic performance parameters and increases total exergy destruction, exergo-destruction impact, and specific power cost in both working cases. According to the obtained results, an increase in the inlet pressure of the turbine in the supercritical case study reduces exergy efficiency and exergetic performance and increases the exergo-destruction impact factor. However, it increases the cycle exergy efficiency and exergetic performance criteria first and then decreases in a subcritical case. The LCOE for the supercritical cycle is 6.96 (c€/kWh) and for the subcritical is 5.52 (c€/kWh). The highest exergy destruction rates are related to the main heat exchanger, condenser, and turbine, respectively.

Energy, Exergy, Economic and Environmental (4E) Analyses of a Geothermal Power Plant with NCGs Reinjection

Abstract In this study, a conceptual geothermal power plant with Non-Condensable Gases (NCGs) reinjection is analyzed from energy, exergy, exergo-economic, and environmental perspectives. The cycle is evaluated in considering both subcritical and supercritical working conditions. A sensitivity analysis comprising the variation of condensing temperature, turbine inlet pressure, and amount of NCGs within the geofluid is performed to assess the system performance from the thermodynamic, economic, and environmental points of view. The exergy efficiency results for the supercritical and the subcritical cycles are 52% and 50.5%, respectively. Results showed increasing the condensing temperature decreases exergy efficiency, net power, and exergetic performance parameters and increases total exergy destruction, exergo-destruction impact, and specific power cost in both working cases. According to the obtained results, an increase in the inlet pressure of the turbine in the supercritical case study reduces exergy efficiency and exergetic performance and increases the exergo-destruction impact factor. However, it increases the cycle exergy efficiency and exergetic performance criteria first and then decreases in a subcritical case. The LCOE for the supercritical cycle is 6.96 ( c € / k W h ) and for the subcritical is 5.52 ( c € / k W h ) . The highest exergy destruction rates are related to the main heat exchanger, condenser, and turbine, respectively.

Effect of different evacuation pressures on thermal performance of vertically placed flat-plate pulsating heat pipe

ABSTRACT This paper is focused on the effects of different evacuation pressures on thermal performance of vertically placed flat-plate pulsating heat pipe (FP-PHP). Experimental results show that the difference in the amount of non-condensable gas (NCG) caused by evacuation pressures is an important reason for the difference in thermal performance of FP-PHP. The water FP-PHP under evacuation pressure of 200 Pa with 18.9 wt% NCG requires the least start-up power and time. NCG will increase the operation instability after ethanol FP-PHP has started up. Evacuation pressure has the least effect on HFE-347 FP-PHP, which can start up successfully without any evacuation.

Effect of evaporator/condenser elevations on a loop heat pipe with non-condensable gas

The coupling effect of evaporator/condenser elevations and non-condensable gas (NCG) on the performance of a loop heat pipe (LHP) operating in gravitational field was investigated experimentally. Ammonia and nitrogen were selected as the working fluid of LHP and the simulated gas of NCG, respectively. The experiments were conducted at three kinds of evaporator/condenser elevations, namely zero elevation, adverse elevation and positive elevation. Experimental results show that NCG will cause an increase in operating temperature, but the trends varies at different evaporator/condenser elevation elevations. The temperature rises caused by NCG at the zero and adverse elevations are negatively correlated with heat load, and the maximum temperature increments are both at the minimum heat load of 15 W, but the influence of NCG is less at adverse elevation. On the other hand, at favorable elevation, the temperature rise exhibits different characteristics in different LHP operation modes, i.e., positively correlated with heat load in gravity driven mode and negatively in capillarity-gravity co-driven mode, and the transition heat load is 60 W. For an LHP that has already contained a certain amount of NCG, functioning at favorable elevation could eliminate the adverse effects of NCG on operating temperature and heat transfer performance to some extent. Furthermore, it is found that the presence of NCG and adverse elevation appears to inhibit the backflow during startup and improve startup stability. These results might have reference significance for the design and installation of the LHP for terrestrial applications.

Investigation of bubble behavior with phase change under the effect of noncondensable gas

An Arbitrary-Lagrangian-Eulerian based numerical method is proposed to study the phase change bubble under the effect of noncondensable gas (NCG). In order to validate the underlying mathematical model, benchmark tests, including the bubble growth in quiescent superheated liquid and the condensation of rising bubble with NCG, are conducted. The numerical results by the phase change model, in which the mass transfer rate is directly determined by interfacial heat flux, is found to agree fairly well with analytical results, and the calculation of fluid flow and heat transfer by the present numerical approach is reasonable. Moreover, the numerical results of free rising bubble condensation with NCG are found to present good agreement with the experimental data on the evolution of bubble size, and the mass balance of the NCGs is proved to be achieved by the model. Finally, the subcooled boiling with NCG on a biphilic surface is numerically investigated, and the bubble behavior and internal distribution of the NCG are studied in detail. In the presence of NCG, the bubbles can even depart from the walls that are negatively superheated. The bubble keeps the bowl-shape for a long time before necking, which is consistent with the experimental observations. The contact line is found to stay at the boundary between the hydrophilic and hydrophobic surfaces. The results also show that the local accumulation of the NCG near the bubble surface decreases the local apparent saturation temperature and inhibits the condensation, and the growth and departure of bubbles is thus promoted. In addition, the amount of NCG in the bubble is found to determine whether the bubble in the subcooled boiling is detached or not.

Investigation of pressure transient analysis methods for single-phase and CO2-rich geothermal reservoirs

Geothermal reservoirs can undergo a transition from single-phase to two-phase or vice versa in their natural setting and during production. Some of these reservoirs can also contain considerable amounts of non-condensable gases, mainly (>90%) CO2. Thus, multi-phase and multi-component effects often complicate the analysis of geothermal well tests as pressure transient analysis (PTA) methods are mainly developed for single-phase flow and slightly compressible fluids.This work aims to investigate the suitability of commonly used PTA methods under two-phase and multi-component conditions. A series of numerical models were developed for a geothermal reservoir containing a mixture of water and CO2 incorporating the production/injection record and the corresponding pressure response. The pressure response of the numerical models was analysed to estimate the reservoir properties, and explore the accuracy of the interpretations. The parameters used in analytical models were also subjected to sensitivity analysis to identify their effect on the characteristic appearance of the pressure derivative plot for realistic interpretations of the reservoir characteristics.This modelling study demonstrates that geothermal reservoirs containing CO2 should be evaluated with great caution as the assumptions that analytical models do not take into consideration may have critical importance when assessing the well test derived properties.

Optimisation of steam and gas push to prevent water influx from a top-water-bearing area into a vapour chamber

This paper presents how to produce bitumen efficiently from the reservoir with top-water-bearing zone. The impact of naturally occurring and/or co-injected non-condensable gas on bitumen production is investigated using numerical studies. Non-condensable gas can improve energy efficiency in two ways: reduction of dynamic vacuum effect and blockage of direct contact of steam chamber and top water layer. A strategic operation mitigating the groundwater influx is presented. An artificial neural network (ANN) model adjusts both pressures of steam and non-condensable gas injected as well as the amount of non-condensable gas. The results show the optimised scheme of steam and gas push (SAGP) can improve the energy efficiency of thermal recovery by maintaining the pressure within the steam chamber enough to prevent excessive water influx, not to obstruct steam chamber expansion in early production stage. [Received: October 10, 2016; Accepted: February 2, 2017]

Optimisation of steam and gas push to prevent water influx from a top-water-bearing area into a vapour chamber

This paper presents how to produce bitumen efficiently from the reservoir with top-water-bearing zone. The impact of naturally occurring and/or co-injected non-condensable gas on bitumen production is investigated using numerical studies. Non-condensable gas can improve energy efficiency in two ways: reduction of dynamic vacuum effect and blockage of direct contact of steam chamber and top water layer. A strategic operation mitigating the groundwater influx is presented. An artificial neural network (ANN) model adjusts both pressures of steam and non-condensable gas injected as well as the amount of non-condensable gas. The results show the optimised scheme of steam and gas push (SAGP) can improve the energy efficiency of thermal recovery by maintaining the pressure within the steam chamber enough to prevent excessive water influx, not to obstruct steam chamber expansion in early production stage. [Received: October 10, 2016; Accepted: February 2, 2017]

Buildup of Abiotic Oxygen and Ozone in Moist Atmospheres of Temperate Terrestrial Exoplanets and Its Impact on the Spectral Fingerprint in Transit Observations

Abstract We investigate the abiotic production of oxygen and its photochemical byproduct ozone through water vapor photolysis in moist atmospheres of temperate terrestrial exoplanets. The amount of water vapor available for photolysis in the middle atmosphere of a planet can be limited by an atmospheric cold-trap, the formation of which largely depends on the amount of noncondensable gases. We study this effect using a photochemical model coupled to a 1D radiative-convective equilibrium model in atmospheres with N2, CO2, and H2O as the main constituents. We find that in atmospheres with a low N2 inventory, water vapor mixing ratios in the middle atmosphere can be more than two orders of magnitude higher compared to atmospheres with an Earth-like N2 inventory. Without a strong surface sink, the noncondensable oxygen can build up rapidly, drying out the upper atmosphere. With a moderate surface sink, the planet can approach a steady state with significant oxygen mixing ratios in which oxygen production is balanced by surface uptake. We use a radiative transfer model to study the spectroscopic fingerprint of these atmospheres in transit observations. Spectral signatures of abiotic oxygen and ozone can be of comparable magnitude as in spectra of Earth seen as an exoplanet. Middle atmospheric water vapor is unlikely to be a usable indicator of the abiotic origin of oxygen because of the influence of oxygen on the water vapor distribution. This suggests that atmospheric oxygen and ozone cannot be used as binary bioindicators and that their interpretation will likely require atmospheric and planetary models.

Investigations of effect of phase change mass transfer rate on cavitation process with homogeneous relaxation model

Abstracts The super high fuel injection pressure and micro size of nozzle orifice has been an important development trend for the fuel injection system. Accordingly, cavitation transient process, fuel compressibility, amount of non-condensable gas in the fuel and cavitation erosion have attracted more attention. Based on the fact of cavitation in itself is a kind of thermodynamic phase change process, this paper takes the perspective of the cavitation phase change mass transfer process to analyze above mentioned phenomenon. The two-phase cavitating turbulent flow simulations with VOF approach coupled with HRM cavitation model and U-RANS of standard k-e turbulence model were performed for investigations of cavitation phase change mass transfer process. It is concluded the mass transfer time scale coefficient in the Homogenous Relaxation Model (HRM) representing mass transfer rate should tend to be as small as possible in a condition that ensured the solver stable. At very fast mass transfer rate, the phase change occurs at very thin interface between liquid and vapor phase and condensation occurs more focused and then will contribute predictably to a more serious cavitation erosion. Both the initial non-condensable gas in fuel and the fuel compressibility can accelerate the cavitation mass transfer process.

Heat transfer characteristics and operation limit of pressurized hybrid heat pipe for small modular reactors

In this paper, a hybrid heat pipe is proposed for use in advanced nuclear power plants as a passive heat transfer device. The hybrid heat pipe combines the functions of a heat pipe and a control rod to simultaneously remove the decay heat generated from the core and shutdown the reactor under accident conditions. Thus, the hybrid heat pipe contains a neutron absorber in the evaporator section, which corresponds to the core of the reactor pressure vessel. The presence of the neutron absorber material leads to differences in the heated diameter and hydraulic diameter of the heat pipe. The cross-sectional areas of the vapor paths through the evaporator, adiabatic, and condenser sections are also different. The hybrid heat pipe must operate in a high-temperature, high-pressure environment to remove the decay heat. In other words, the operating pressure must be higher than those of the commercially available thermosyphons. Hence, the thermal performances, including operation limit of the hybrid heat pipe, were experimentally studied in the operating pressure range of 0.2–20bar. The operating pressure of the hybrid heat pipe was controlled by charging the non-condensable gas which is unused method to achieve the high saturation pressure in conventional thermosyphons. The effect of operating pressure on evaporation heat transfer was negligible, while condensation heat transfer was affected by the amount of non-condensable gas in the test section. The operation limit of the hybrid heat pipe increased with the operating pressure. Maximum heat removal capacity of the hybrid heat pipe was up to 6kW which is meaningful value as a passive decay heat removal device in the nuclear power plants. Based on the experimentally measured maximum heat removal capacities, models predicting the operation limit (flooding limit) of the hybrid heat pipe were developed.

Effect of non-condensable gas on the start-up of a gravity loop thermosyphon with gas–liquid separator

This study experimentally investigated the influence of non-condensable gas (NCG) on the start-up time of gravity loop thermosyphon (GLT) developed for regenerative building heating exchangers. A gas–liquid separator was added to the end of the condensate line in the GLT. Given characteristics of the NCG that accumulated in the gas–liquid separator, and the NCG is prevented from circulating in the loop, thereby effectively lowering the effect of NCG on heat exchange. The presence of NCG not only influenced the local condensation heat transfer of the condenser but also affected the start-up of the loop thermosyphon. Results of the experimental investigation revealed that the presence of NCG increased the start-up time of GLT. A higher NCG level corresponds to, a longer start-up time. In particular, the start-up time was 2.8 times more than that in the evacuation when amount of NCG was 30% in volume. The NCG–vapor blocks zone hinders the vapor transmission from the evaporator to the condenser in the vapor line between the evaporator and condenser, further causing a rapid increase in system pressure during start-up. Moreover, obvious pressure peak curve phenomena occurred in a number of conditions, such as heat load was greater than or equal 2.0kW and amount of NCG was less than or equal 30% in volume.

Measuring non-condensable gases in steam

In surgery, medical devices that are used should be sterilized. To obtain surface steam sterilization conditions, not only in the sterilizer chamber itself but also in the loads to be sterilized, the amount of non-condensable gases (NCGs), for instance air, should be very low. Even rather small fractions of NCGs (below 1%) seriously hamper steam penetration in porous materials or devices with hollow channels (e.g., endoscopes). A recently developed instrument which might detect the presence of residual NCGs in a reliable and reproducible way is the 3M(TM) Electronic Test System (ETS). In this paper, a physical model is presented that describes the behavior of this instrument. This model has been validated by experiments in which known fractions of NCGs were introduced in a sterilizer chamber in which an ETS was placed. Despite several approximations made in the model, a good agreement is found between the model predictions and the experimental results. The basic principle of the ETS, measuring the heat transfer by condensation on a cooled surface, permits a very sensitive detection of NCGs in harsh environments like water vapor at high temperatures and pressures. Our model may serve to develop adapted and optimized versions of this instrument for use outside the field of sterilization, e.g., in heat exchangers based on steam condensation.

Effect of Non-Condensable Gas Leakage on Long Term Cooling Performance of Loop Thermosyphon

We have developed a loop thermosyphon for cooling electronic devices. The cooling performance of a thermosyphon deteriorates with an increasing amount of non-condensable gas (NCG). Design of a thermosyphon must consider NCG to provide guaranteed performance for a long time. In this study, the heat transfer performance of a thermosyphon was measured while changing the amount of NCG. The resultant performances were expressed as approximations. These approximations enabled us to predict the total thermal resistance of the thermosyphon by the amount of NCG and input heating. Then, using the known leakage in the thermosyphon and the amount of dissolved NCG in the water, we can predict the amount of NCG and the total thermal resistance of the thermosyphon after ten years. Although there is a slight leakage in the thermosyphon, we are able to design a thermosyphon with a guaranteed level of cooling performance for a long time using the proposed design method.

Effects of Non-Condensable Gases on Heat Transfer Performance of Loop Thermosyphon for CPU Cooling

We have developed a loop thermosyphon for cooling electronics devices. Non-condensable gases (NCG) in a loop thermosyphon increase by leakage from outside, release of the gas dissolved in the refrigerant, and chemical reaction in the inside. Hence, it is necessary to know how the heat transfer performance changes when the amount of NCG in a loop thermosyphon increases. The effect of NCG's amount was measured for each component of the loop thermosyphon while changing the amount of heat input. The overall thermal resistance of a loop thermosyphon increased with the amount of NCG. The thermal resistance of the condensing part particularly increased with the NCG. The effect of NCG on the boiling part should be considered only by steam temperature which was raised by increase in the amount of NCG. The thermal resistance of the air cooling part is not affected by NCG, but the temperature difference of the air cooling part becomes smaller because heat-leakage increases with steam temperature.