Primary Mass Flow Research Articles

The Turbine Heat Waste of RDE for Desalination Laboratory Plant

Reaktor Daya Eksperimental (RDE) is currently being developed by Batan. This reactor uses HTGR technology as the basis for its development. It has an indirect cycle power conversion with primary coolant is helium and its secondary is water. The RDE will be operated not only for an electrical generation but also for cogeneration purposes. One process can be supported in the cogeneration scheme is seawater desalination. Water is the main source of life and its availability must be maintained on earth. Therefore, to overcome the scarcity of freshwater at the remote islands in Indonesia, it needs nuclear cogeneration by coupling of RDE and desalination. With this technology, it can simultaneously produce electricity and freshwater. A variety of desalting technologies has been developed over the years, including primarily thermal and membrane processes. This paper discusses the simulation of RDE for desalination purposes. The methodology used in this research is modeled and simulation by using ChemCAD. The desalination plant is simulated by the heat exchanger unit operation. The RDE primary mass flow rate is 4.3 kg/s, 700°C of temperature and 30 bars of pressure. The secondary coolant mass flow rate is 3.8 kg/s, 60 bars, and 350°C respectively. Depending upon the specific designs the temperature ranges of the waters in this exchanger could be between 80-130°C. The extraction point of the desalination process is at turbine output, with 300.16°C, 8 bars and 3.7 kg/s of mass flow rate. The total amount of freshwater will generate is 4.09 m3/h equal to 98.16 m3/day.

Effects of Hall current on MHD natural convection in between two vertical flat walls with induced magnetic field and heat source/sink

ABSTRACT The effects of Hall current and heat source/sink are considered on MHD natural convective flow of an electrically conducting viscous fluid in between two vertical flat walls with an induced magnetic field. The exact analytical solutions for converted flow equations from governing equations after using suitable non-dimensional variables are obtained. The effects of Hall current, heat source/sink, and magnetic field on the velocity components, induced magnetic field in flow dynamics, and the induced current density are presented through some figures and tables. The impact of the Hall current is massive on both components of velocity and those increases with Hall current. Whereas, both the components of the induced magnetic field and induced current density decrease due to Hall current. Whereas due to heat source(sink), the primary velocity enhances(reduces) and the effect is opposite for the secondary velocity. For increasing heat source parameter both primary and secondary induced magnetic field and induced current density increase, while temperature-dependent heat sink shows contrary effects. In two flat vertical walls, the variations in the skin-friction components, i.e. surface drag force components for the presence of magnetic field are opposite to each other. In addition, mass flow rate components enhance for Hall current and reduce for a stronger magnetic field. With increasing heat source parameter, the primary skin-friction component rises and secondary skin-friction component decreases at the left wall with higher temperature, while at the right wall with lower temperature both skin-friction components have increasing nature, and reverse impacts are observed for the heat sink. Due to the presence of heat source, primary (secondary) mass flow rate component enhances (reduces) and opposite effects have found for the heat sink.

Impact of primary nozzle area ratio on the performance of ejector refrigeration system

This paper proposes an experimental investigation to demonstrate the impact of the primary nozzle area ratios on the ejector performance in an R141b ejector refrigeration system. The experimental refrigerator was tested based on the alternative testing method in which the generator temperature and condenser pressure were held constant for particular test cases. Three primary nozzles were studied which had identical throat diameter but different nozzle area ratios which produced different exit Mach numbers. Three primary nozzles were equipped with one mixing chamber with throat diameter of 9 mm. With the alternative testing method, two critical evaporator temperatures were found, the lower and upper critical evaporator temperatures. It was also found that the change in the nozzle exit Mach number and the primary fluid mass flow rate (using different generator temperatures) had significant impact on these two critical points which affected the entire ejector performance. The primary fluid expansion coefficient (Cprimary), which is key to indicate the limited range of the working condition, was introduced. It indicates the expansion wave formation which has significant impact on two critical points. Hence, the proper value of Cprimary under various primary nozzle area ratios was determined for this present work.

The Analysis of Loss of Forced Flow Event on the HTGR Type Experimental Power Reactor

Since 2014, Indonesia's National Atomic Energy Agency (BATAN) has been launching a plan to construct a 10 MWt Experimental Power Reactor (Reaktor Daya Eksperimental / RDE). The RDE design is based on the small-sized pebble-bed high-temperature gas-cooled reactor (HTGR) technology with TRISO fuels. By concept, HTR-10 design, which was developed by the INET of China, is used as the reference design. During the development process, a safety analysis report (SAR) of RDE design has to be prepared to be evaluated by the Indonesia Nuclear Regulatory Agency (BAPETEN). The report contains, among others the description of the RDE accident sequences, which can be only provided by simulations using a certain code. This paper emphasizes the transient analysis, which is simulated using RELAP5/SCDAP/Mod3.4 , which is a thermal-hydraulic code specified for light water coolant systems. The simulated event is the loss of primary coolant mass flow, which is caused by the failure of the primary gas blower motor. The methodology of simulation is first by modelling the RDE nuclear steam supply system to verify steady-state operational parameter of the RDE design. The second step is to simulate the event of loss of flow, which is followed by the failure to shut down the reactor. The simulation results in the decrease of the fuel pebble temperature during the event due to the negative fuel temperature reactivity coefficient and the core heat removal by the cavity cooling. Overall, the RELAP5 code has a limitation in the RDE simulation to define two different non-condensable gases, which reduces the accuracy of the simulation results.

Effect of water nano-droplet injection on steam ejector performance based on non-equilibrium spontaneous condensation: A droplet number study

Condensation and evaporation processes in high velocity flowing steam within ejectors profoundly influence the performance of these devices. In the current study, the effects of water droplet injection in the inlet of the primary nozzle on the condensation and evaporation processes are investigated through the wet steam model. The findings reveal that the existence of liquid droplets in the steam related to the inlet of the primary nozzle has effects on the two-phase parameters, shock waves intensity, entrainment ratio, mixing layer growth and two-phase heat, such that these parameters are minimized or maximized for a specific number of droplets. The inlet wetness in the primary nozzle provides a delay in the condensation shock, and the maximum delay happens in the wetness 0.4%. In the case of using 2.0×1017 droplets with 17.5 nm radius (wetness 0.4%), in comparison with the case of without the droplets at the inlet, the entrainment ratio, primary mass flow rate, and secondary mass flow rate reduce by 2.79%, 0.8%, and 3.72%, respectively. The novelty of this study is displaying the effects of water droplet injection in the inlet of the primary nozzle on the ejector performance.

Transient analysis of TMSR-SF0 simulator

ABSTRACT Transient analysis of TMSR-SF0, a molten salt thermal-hydraulic experimental system of molten salt reactor, is investigated using RELAP5/MOD4.0 code. Simulation model consists of two coolant circuits. Variations in core power, primary mass flow, secondary mass flow, and air mass flow are studied separately. Both temporary and permanent phenomena of test facility are concerned in different circumstances. The results indicate that protective system should focus on unusual operation conditions in order to make safety measures for preventing the test facility from overheating and overcooling. The temperature distribution of key measuring points shows that both power and mass flow perturbations are acceptable in simulation model, which is the performance of high heat capacity of molten salt. Meanwhile, the ranges of perturbation are shown in this paper.

A new semi-empirical correlation for driving mass-flow rate calculation through ejectors for CO2 heat pumps. Comparison with predictions of other methods.

Carbon dioxide (CO2) is an interesting substitute of traditional HFCs in vapor compression systems, due to its environmentally friendly characteristics: zero ODP and extremely low GWP. Nevertheless, the use of CO2 heat pumps in residential heating and cooling applications actually is still limited, due to the different operating conditions of gas cooling, they can perform significantly worse than conventional.The use of ejection systems for the fluid expansion in a refrigeration cycle can contribute to recovery part of the mechanical energy otherwise dissipated as friction, leading to significant benefits in terms of performance. The ejector sizing is a critical point for the balancing of components and the correct operation of the CO2 heat pump; in this regard, the availability of reliable methods for calculating the motive flow rate would be useful. In recent years, ENEA Laboratory DTE-PCU-SPCT of the Casaccia research center, along with the Industrial Engineering Department of Federico II University of Naples, carried on a project aimed at evaluating experimentally the effect of several ejectors geometries on the global performance of a CO2 heat pump working with a transcritical cycle.This paper presents a new semi-empirical correlation for the ejector primary mass flow rate calculation, developed by the experimental data, based on the hypothesis of isentropic and choked flow. The correlation is then tested on other experimental data available in the literature for different ejectors. Finally, the predictions are compared to others semi-empirical correlations present in the literature.

Experimental Performance of a Two-Phase Ejector: Nozzle Geometry and Subcooling Effects

This paper presents the results of an experimental study on a two-phase ejector. The main objective is to assess the effects of the nozzle’s divergent and the throat diameter on performance under various working conditions. Under the same conditions, ejector operation with a convergent nozzle, results in higher critical primary mass flow rate and lower critical pressure than with a convergent-divergent nozzle version. Experiments show as well that the flow expansion is higher in the convergent-divergent nozzle. The throat diameter turns out to have an important impact only on the amount of the critical mass flow rate. The nozzle geometry has no impact on its optimal position in the ejector. Globally, the ejector with the convergent-divergent nozzle provides a higher entrainment ratio, due to a reduced primary mass flow rate and an increased secondary flow induction. Tests also show that the ejector with a lower throat diameter provides a higher entrainment ratio, due to better suction with less primary flow. Unlike the convergent-divergent nozzle, the convergent nozzle permits an entrainment ratio almost insensitive to a wide range of primary inlet sub-cooling levels. Primary and secondary mass flow rates increase proportionally with the subcooling level and result in a quasi-constant entrainment ratio.

Thermal-Hydraulics Operation Parameters Modeling and Analysis of KLT-40S Reactor at Steady-State and Transient Condition using RELAP5-3D

One of Floating Nuclear Power Plant (FNPP) designs in the world is currently being built by Russian Federation, named “Academic Lomonosov,” which uses two PWR types, KLT-40S as its power unit. However, too little information regarding its detailed technical specification is available, including its thermal-hydraulics parameters. The objective of this research is to create a thermal-hydraulic model of KLT-40S reactor core use RELAP5-3D and to predict fuel and cladding temperature value at the steady-state condition, and transient condition with a variety of primary coolant mass flow rate and pressure to simulate abnormal event within the reactor. The reactor thermal-hydraulic model is created by dividing 121 coolant channels in the actual nuclear fuel assemblies into two channels: one channel to simulate coolant flow in 120 fuel assemblies with average heat generation, and the other channel to simulate coolant flow in one fuel assembly with highest heat generation in the core. The fuel structure had solid cylinder geometry and made from ceramic-metal UO2 dispersed in the inert silumin matrix. The fuel cladding is made from zirconium alloy. These fuel heat structures generate heat from fission reaction and are modelled as a heat source according to the reactor power technical data, i.e., 150 MWt. The reactor axial power distribution is approximated by cosine distribution. Operation parameter variation that represents the real reactor normal operation condition in this research is a variation that has flow loss coefficient value 8,000, radial power peaking factor 1.1, and axial power peaking factor 1.1 with axial power peaking located in the middle of the fuel rod. The fuel and cladding temperature value at the steady-state condition and several transient conditions are predicted in this research, and there is no temperature value that goes beyond the safety limit.

The primary dynamic gravimetric system for gas mass flow measurement

High accuracy mass flow measurement is an enabling technology at the base of many industries. HORIBA STEC Co., Ltd. developed its own primary gas mass flow measurement system. We employed the dynamic gravimetric method in a vacuum chamber, and we use only mass and time information for mass flow rate calculation, with no correction for temperature, pressure and humidity. The system achieved 0.036% uncertainty as lowest of results with satisfactory performance of proficiency testing with NIST (National Institute of Standards and Technology). Then the laboratory has been granted ISO/IEC 17025 accreditation since 2017. This paper describes the system details and uncertainty analysis.

Experimental investigation of burning of pulverized peat in a bidirectional vortex combustor

The paper reports on the results of experimental research of bidirectional vortex combustor operation at different modes. This combustor implements a new idea of burning solid pulverized fuel in a bidirectional swirling flow. The experimental results confirmed the thesis about a wide range of stable operation of the combustor, as well as its environmental friendliness: the values of exhaust emission of CO and NOx are significantly lower than those for the direct-flow combustor. Besides, such combustor can operate in two modes: as an igniter or stabilizer of boiler furnace, where it generates a stable high-enthalpy flame as well as an independent device with low emission values. A summary of research results defines that the most environmentally friendly operating mode is achieved at the net air-fuel equivalence ratio λΣ = 1.3 and the ratio of primary and secondary air mass flow rates n = 2.7.

Thermo-economic analysis of composite district heating substation with absorption heat pump

A novel composite district heating substation (CDHS) with absorption heat pump was proposed and analyzed in this paper. The CDHS was composed of a water-LiBr absorption heat pump and two plate heat exchanges, which could improve the utilization efficiency of geothermal water and the primary supply water of the primary district heating network. The effect of geothermal water temperature and mass flow rate, and primary supply water mass flow rate variation on system performance were investigated and analyzed by case study. The objective was to maximize net profit and minimize payback period by the cascade utilization of the geothermal water and primary supply water. In addition, economic analysis and multi-objective optimization were conducted to find the optimal mass flow rate of the primary supply water based on the TOPSIS decision making method. Exergy loss analysis was applied under the optimal condition to discover which components had the largest exergy loss. Results indicated that, the proposed system had a net profit of 16.22 M$ in the life time and the minimum payback period was 2.2 years at the optimal primary supply water mass flow rate of 46.16 kg/s where the COP and exergy efficiency of the system were 1.85 and 59.81%, respectively.

Numerical and experimental investigation on an ejector designed for an 80 kW polymer electrolyte membrane fuel cell stack

An ejector aiming at an 80 kW polymer electrolyte membrane fuel cell system designed based on the Sokolov 1-D ejector mode is evaluated numerically and experimentally. A two-dimensional axisymmetric model for the ejector is established based on the Shear Stress Transport model and the Re-Normalization Group model and validated by comparing simulated results and experimental data. Effects of the ejector's mixing chamber diameter and diffusion chamber angle and humidity of the secondary flow on its performance are investigated by a Computational Fluid Dynamics method. The results show that the primary mass flow rate presents a linear relationship with the primary pressure and that the Re-Normalization Group model is more accurate than the Shear Stress Transport model in predicting the ejector's performance. When the diffusion chamber angle is 11° and 13°, the ejector exhibits the best performances. The mixing chamber diameter and the secondary flow humidity significantly influence entertainment ratio and hydrogen recirculation of the ejector.

Experimental parametric investigation of vapor ejector for refrigeration applications

A prototype ejector system having a nominal cooling capacity of 30 kW was used to study the influence of ejector geometry and operating conditions on the ejector performance. Experiments were realized over a wide parameter range: primary inlet pressure from 1700 to 2900 kPa; secondary inlet pressure from 170 to 550 kPa; outlet pressure from 350 to 1000 kPa. The performance was evaluated in terms of the entrainment ratio and the temperature lift. The experimental results led to the following observations: (a) A simple calculation of the primary mass flow rate can be used for the design of ejector systems; (b) A given ejector operated at fixed primary inlet pressure shows a range of outlet pressures where the entrainment ratio is maximum. A correlation of the optimal entrainment ratio versus the primary pressure is proposed; (c) There is an inverse relationship between the temperature lift and the entrainment ratio; (d) For a fixed primary inlet pressure, the optimal outlet pressure can be set at a given value by the appropriate geometry of the ejector. Finally, a two-plateau behavior of entrainment ratio as a function of outlet pressure was observed, which might be related to an improper nozzle exit position.

Investigation of the heat-recovery/non-recovery coke oven operation using a one-dimensional model

In order to predict the behaviour of the heat-recovery (HR) /non-recovery (NR) coke oven during the coke-making process, time-dependent numerical simulations have been carried out. A one-dimensional (1D), self-made (non-commercial) mathematical model has been used to predict temperatures, pressure and gas composition within upper-oven, down-comers and sole-flue of the oven analyzed. Moreover, mass flow rates of primary and secondary air, entrained from the surroundings, have been calculated. The results of the simulations indicate that the carbonization process performed in HR/NR ovens is slightly affected by surrounding conditions. A 15.8% (from 253 K to 293 K) increase in surroundings temperature has resulted in a 0.6% of temperature change within the upper-oven and the sole-flue. The same variation in ambient temperature affects slightly (0.3%) the primary and secondary air mass flow rate entrained from the environment. The increase in surroundings temperature reduces the natural draft by about 6 Pa, but pressure losses in the air ducts become higher. The usage of the so-called “sliding gates” installed in the primary and secondary air inlets is of great importance for coke-making. Changing the closure level of the primary air inlets by 25% causes the gas temperature to be altered by 4.3%. Another important factor is suction generated by a fan/stack. This parameter (suction increased by 40 Pa) changes the temperature inside the oven by about 9.7% for the upper-oven and 3.7% for the sole-flue. Both parameters have key significance for the carbonization process. The gathered data provides an improved understanding of the HR/NR coke oven operation and allows optimizing HR/NR coke oven design and the carbonization process itself.

A Review of Molten Salt Reactor Kinetics Models

Interest in circulating fuel reactors (CFRs), particularly molten salt reactors (MSRs) of the fluid fuel type, has been growing in the last two decades. Starting with a resurgence of interest in Europe, there have been a growing number of methods proposed and codes developed to model the kinetics of CFRs, which is a capability essential to the design and evaluation of such reactors. This work first reviews the physical phenomena unique to CFRs in light of current research and how CFR kinetics are impacted by these considerations. In general, it is found that the movement of delayed neutron precursors (DNPs) through the primary loop has significant impacts on transients at low reactor powers or those with significant spatial components such as a change in the primary loop mass flow rate. Effects on the neutron flux are exceedingly minimal and entirely negligible. An extensive review of published models and methods for simulating CFR kinetics is presented, along with transient simulations in fast and thermal neutron flux systems using representative codes from each of the main modeling categories. Comparisons among methods are presented as are recommendations for their use or nonuse in various transient and work-flow scenarios. In general, it is recommended that time-resolved, multigroup neutron diffusion approaches be used to establish ranges of applicability for point reactor kinetics (PRK)–based approaches that themselves may not be applicable for all modeling situations. In such cases, it is suggested that quasi-static approaches be used where PRK-based approaches cannot be used. Finally, a review of common assumptions used in these models is presented, along with an evaluation of their impact on model performance. It is found that neglecting turbulent diffusion in open core–type CFRs is a poor assumption that leads to an underestimation of the reduction of the delayed neutron fraction. Additionally, it is seen that exclusion of secondary heat transfer loops in models leads to underestimation of transient peaks and troughs.

Experimental investigation on the air excess and air displacement influence on early stage and complete combustion gaseous emissions of a small scale fixed bed biomass boiler

The world energy demand growth is more and more supplied by renewable energy sources. In this scenario, biomass has a key role in both heat and power generation. Particularly, biomass combustion can be used in small size micro and distributed generation systems, or in smart grids together with wind and solar energy where a programmable energy source is necessary to keep the electric grid stable. In this paper, a small size 140 kWth biomass fixed bed boiler of the University of Pisa, located at the Biomass to Energy Inter-University Research Centre (CRIBE), was studied experimentally to characterize the biomass combustion process. Emissions of NOx, O2, CO2 and CO, together with the temperature data, were measured in the flue gases. Moreover, the spatial distribution of volatile products from the fixed bed surface, such as H2, CO, CO2, CH4, C2H6, C2H4, C2H2, together with temperature data, was studied in the early combustion stage. The parametric variation of the feed air flow and its effect on the emissions and performances was also investigated. The results indicate that the primary air mainly affects the volatiles distribution on the biomass combustion surface. Therefore, the CO emission was minimized at values of 0.03%vol with an air excess equal to 2 and a 0.06 secondary to primary air mass flow ratio.

Theoretical model of transcritical CO2 ejector with non-equilibrium phase change correlation

A theoretical model of an ejector was proposed for a transcritical carbon dioxide ejector-expansion refrigeration system capable of predicting the mass flow rates of both primary and secondary flows. A non-equilibrium correlation in the energy-conservation equation was proposed and validated using 130 cases obtained from three different ejector configurations. The differences in the predicted primary mass flow rates between the cases with and without the correlation were insignificant when the liquid mass fraction at the nozzle throat xt was less than 0.65. However, the prediction error increases dramatically when the correlation was not used for xt > 0.65. The Mach number in the CO2 ejector is lower than 1.5 and the “double choking” phenomenon will not happen in the CO2 ejector. Finally, a correlation was fitted for the primary flow pressure at the nozzle throat, which can be used to replace iterative solving in the model calculation.

Experimental investigation on air displacement and air excess effect on CO, CO2 and NO emissions of a small size fixed bed biomass boiler

Abstract Biomass has a key role in the future of the energetic scenario, since it is a programmable renewable energy source which is suitable either to generate power and/or produce heat. This paper deals with biomass combustion processes in small size boilers, which is suited either for large residential buildings, or for small size industrial users. This kind of boilers is different from small pellet stoves and fireplaces and from large utility size boilers. In particular, those small size boilers have been seldom studied in the scientific literature about the combustion kinetics and pollutant formation mechanisms. Hence, the authors present the thermo-chemical data collected from a 140 kWth chipped wood boiler at the University of Pisa. The effect of the air excess and the ratio between and secondary feeding air and primary feeding air mass flow rate, on CO, CO2 and NOx emissions was investigated. Results have shown that the air excess has the main influence on the pollutant produced. A comparison of the measured data with those presented in the literature and the discrepancies with other studies are also discussed.

The performance of steam ejector refrigeration system based on alternative analysis

The performance of a steam ejector refrigerator was analyzed based on an “alternative analysis”. The alternative analysis reflects an actual operation of an ejector refrigerator. In this analysis, the evaporator saturation temperature associated with cooling load was varied while the boiler saturation temperature and the condenser pressure were fixed. Form this test, the critical evaporator temperature was determined. The critical evaporator temperature is the lowest point that ejector still operated under choked flow condition. A 1 kW experimental ejector refrigerator was constructed. Variation of operating conditions and primary nozzles were implemented. It was found that the variation in operating conditions and the nozzle throat diameters significantly affected the critical evaporator temperature. Variation of condenser pressure had a strong effect on critical evaporator temperature Meanwhile the entrainment ratio in the choked flow condition was independent of the condenser pressure. The critical evaporator temperature decreased with increasing the condenser pressure and vice versa. Variations of the boiler saturation temperature and the primary nozzle throat diameter affect the mass flow of primary fluid. Either increasing the boiler saturation temperature or the primary nozzle throat diameter, the mass flow of primary fluid increased. When the primary fluid mass flow was increased, the critical evaporator temperature was reduced. On the other hand, entrainment ratio in the choked flow condition decreased. However, if the primary fluid mass flow was increased to a certain value, evaporator temperature didn’t decrease as expected.