scholarly journals Numerical Evaluation of Novel Particle Release Patterns in High-Temperature Falling Particle Receivers

2017 ◽  
Author(s):  
Brantley Mills ◽  
Clifford K. Ho
Keyword(s):  
High Temperature ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Elevated Temperatures ◽  
Particle Mass ◽  
Test Facility ◽  
Volumetric Heating ◽  
Particle Release

Novel particle release patterns have been proposed as a means to increase the thermal efficiency of high-temperature falling particle receivers. Innovative release patterns offer the ability to utilize light-trapping and volumetric heating effects as a means to increase particle temperatures over a conventional straight-line particle release pattern. The particle release patterns explored in this work include wave-like patterns and a series of parallel curtains normal to the incident irradiation that have shown favorable results in previous numerical studies at lower particle temperatures. A numerical model has recently been developed of an existing falling particle receiver at the National Solar Thermal Test Facility at Sandia National Laboratories to evaluate these patterns at elevated temperatures necessary to evaluate radiative and convective losses. This model has demonstrated that thermal efficiency gains of 2.5–4.6% could be realized using these patterns compared to the conventional planar release depending on the particle mass flow rate. Increasing the number of parallel curtains, increasing the spacing between curtains, and shifting the particle mass flow rate deeper in the receiver cavity was also found to increase the thermal efficiency. These effects became less significant as the particle mass flow rate increased.

scholarly journals Off-Design Dynamic Performance Analysis of a Solar Aided Coal-Fired Power Plant

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2950
Author(s):  
Vinod Kumar ◽  
Liqiang Duan
Keyword(s):  
Power Plant ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Dynamic Performance ◽  
Feed Water ◽  
Saving Rate ◽  
Coal Consumption ◽  
Dynamic Performance Analysis

Coal consumption and CO2 emissions are the major concerns of the 21st century. Solar aided (coal-fired) power generation (SAPG) is paid more and more attention globally, due to the lesser coal rate and initial cost than the original coal-fired power plant and CSP technology respectively. In this paper, the off-design dynamic performance simulation model of a solar aided coal-fired power plant is established. A 330 MW subcritical coal-fired power plant is taken as a case study. On a typical day, three various collector area solar fields are integrated into the coal-fired power plant. By introducing the solar heat, the variations of system performances are analyzed at design load, 75% load, and 50% load. Analyzed parameters with the change of DNI include the thermal oil mass flow rate, the mass flow rate of feed water heated by the solar energy, steam extraction mass flow rate, coal consumption, and the plant thermal efficiency. The research results show that, as DNI increases over a day, the coal saving rate will also increase, the maximum coal saving rate reaches up to 5%, and plant thermal efficiency reaches 40%. It is analyzed that the SAPG system gives the best performance at a lower load and a large aperture area.

The Investigation of Back-Mixing Particles near Dust Outlet in Cyclone Separator with Tangential Inlet

2011 ◽  
Vol 239-242 ◽  
pp. 2142-2148
Author(s):  
Hui Min Tan ◽  
Jian Jun Wang ◽  
You Hai Jin
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Particle Diameter ◽  
Particle Mass ◽  
Cyclone Separator ◽  
Axial Distribution ◽  
Computational Fluid Dynamics Analysis ◽  
Back Mixing ◽  
Tangential Inlet

Based on experimental and computational fluid dynamics analysis, the phenomenon of particle back-mixing near the dust outlet in cyclone separator with tangential inlet was studied. The results show that particle back-mixing appears near the dust outlet geometry. Particle back-mixing can be divided into dust hopper back-mixing and discharge cone back-mixing for different generation mechanism. The upward flow coming from dust hopper, which occupies 17.7% of the inlet gas, can induce dust hopper back-mixing. The particle mass flow rate that caused by dust hopper back-mixing occupies 46.6% of total inlet particle mass flow rate. Precessing vortex core, bias flow and high turbulent intensity near the dust outlet can induce discharge cone back-mixing. For both dust hopper back-mixing and discharge cone back-mixing, particle back-mixing is serious near the dust outlet geometry, which occupies 56.8% of total inlet particle mass flow rate. Particle which is smaller than 18μm can mix backward. The axial distribution of particle concentration decreases sharply in a range of 1.5 D (cyclone diameter) height above the dust discharge port. At last, only 2.6% of back-mixing particles with diameter no bigger than 13μm escape from vortex finder. This effect on separator efficiency increases with the particle diameter decreases.

scholarly journals An experimental study of the thermal performance of the square and rhombic solar collectors

2018 ◽  
Vol 22 (1 Part B) ◽  
pp. 487-494 ◽  
Author(s):  
Aminreza Noghrehabadi ◽  
Ebrahim Hajidavaloo ◽  
Mojtaba Moravej ◽  
Ali Esmailinasab
Keyword(s):  
Experimental Study ◽  
Flat Plate ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Solar Collectors ◽  
Heating Systems ◽  
Solar Water Heating

Solar collectors are the key part of solar water heating systems. The most widely produced solar collectors are flat plate solar collectors. In the present study, two types of flat plate collectors, namely square and rhombic collectors are experi?mentally tested and compared and the thermal performance of both collectors is investigated. The results show both collectors have the same performance around noon (?61%), but the rhombic collector has better performance in the morning and afternoon. The values for rhombic and square collectors are approximately 56.2% and 53.5% in the morning and 56.1% and 54% in the afternoon, respectively. The effect of flow rate is also studied. The thermal efficiency of rhombic and square flat plate collectors increases in proportion to the flow rate. The results indicated the rhombic collector had better performance in comparison with the square collector with respect to the mass-flow rate.

Receiver Outlet Temperature Control for Falling Particle Receiver Applications

2021 ◽  
Author(s):  
Nathan Schroeder ◽  
Henk Laubscher ◽  
Brantley Mills ◽  
Clifford K. Ho
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Temperature Rise ◽  
Pid Controller ◽  
Input Parameter ◽  
Slide Gate ◽  
Process Variable ◽  
Test Facility ◽  
Outlet Temperature

Abstract Falling particle receivers (FPRs) are being studied in concentrating solar power applications to enable high temperatures for supercritical CO2 (sCO2) Brayton power cycles. The falling particles are introduced into the cavity receiver via a linear actuated slide gate and irradiated by concentrated sunlight. The thickness of the particle curtain associated with the slide-gate opening dimension dictates the mass flow rate of the particle curtain. A thicker, higher mass flow rate, particle curtain would typically be associated with a smaller temperature rise through the receiver, and a thinner, lower mass flow rate, particle curtain would result in a larger temperature rise. Using the receiver outlet temperature as the process variable and the linear actuated slide gate as the input parameter a proportional, integral, and derivative (PID) controller was implemented to control the temperature of the particles leaving the receiver. The PID parameters were tuned to respond in a quick and stable manner. The PID controlled slide gate was tested using the 1 MW receiver at the National Solar Thermal Test Facility (NSTTF). The receiver outlet temperature was ramped from ambient to 800°C then maintained at the setpoint temperature. After reaching a steady-state, perturbations of 15%–20% of the initial power were applied by removing heliostats to simulate passing clouds. The PID controller reacted to the change in the input power by adjusting the mass flow rate through the receiver to maintain a constant receiver outlet temperature. A goal of ±2σ ≤ 10°C in the outlet temperature for the 5 minutes following the perturbation was achieved.

Design and Testing of a Can Combustor for a Small Gas Turbine Application

2013 ◽  
Author(s):  
K. V. L. Narayana Rao ◽  
N. Ravi Kumar ◽  
G. Ramesha ◽  
M. Devathathan
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Turbines ◽  
Pressure Loss ◽  
High Energy ◽  
Experimental Results ◽  
High Mass ◽  
Test Facility ◽  
Design Requirements

Can type combustors are robust, with ease of design, manufacturing and testing. They are extensively used in industrial gas turbines and aero engines. This paper is mainly based on the work carried out in designing and testing a can type combustion chamber which is operated using JET-A1 fuel. Based on the design requirements, the combustor is designed, fabricated and tested. The experimental results are analysed and compared with the design requirements. The basic dimensions of the combustor, like casing diameter, liner diameter, liner length and liner hole distribution are estimated through a proprietary developed code. An axial flow air swirler with 8 vanes and vane angle of 45 degree is designed to create a re-circulation zone for stabilizing the flame. The Monarch 4.0 GPH fuel nozzle with a cone angle of 80 degree is used. The igniter used is a high energy igniter with ignition energy of 2J and 60 sparks per minute. The combustor is modelled, meshed and analysed using the commercially available ansys-cfx code. The geometry of the combustor is modified iteratively based on the CFD results to meet the design requirements such as pressure loss and pattern factor. The combustor is fabricated using Ni-75 sheet of 1 mm thickness. A small combustor test facility is established. The combustor rig is tested for 50 Hours. The experimental results showed a blow-out phenomenon while the mass flow rate through the combustor is increased beyond a limit. Further through CFD analysis one of the cause for early blow out is identified to be a high mass flow rate through the swirler. The swirler area is partially blocked and many configurations are analysed. The optimum configuration is selected based on the flame position in the primary zone. The change in swirler area is implemented in the test model and further testing is carried out. The experimental results showed that the blow-out limit of the combustor is increased to a good extent. Hence the effect of swirler flow rate on recirculation zone length and flame blow out is also studied and presented. The experimental results showed that the pressure loss and pattern factor are in agreement with the design requirements.

Analytical Modeling and Experimental Validation of Heating at the Leaf Seal/Rotor Interface

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
Michael J. Pekris ◽  
Gervas Franceschini ◽  
Andrew K. Owen ◽  
Terry V. Jones ◽  
David R. H. Gillespie
Keyword(s):  
Mass Flow Rate ◽  
Analytical Model ◽  
Mass Flow ◽  
Flow Rate ◽  
Temperature Rise ◽  
Thermal Characteristic ◽  
Frictional Heat ◽  
Test Facility ◽  
Engine Operation ◽  
Secondary Air

The secondary air system of a modern gas or steam turbine is configured to satisfy a number of requirements, such as to purge cavities and maintain a sufficient flow of cooling air to key engine components, for a minimum penalty on engine cycle efficiency and specific fuel consumption. Advanced sealing technologies, such as brush seals and leaf seals, are designed to maintain pressures in cavities adjacent to rotating shafts. They offer significant reductions in secondary air parasitic leakage flows over the legacy sealing technology, the labyrinth seal. The leaf seal comprises a series of stacked sheet elements which are inclined relative to the radial direction, offering increased axial rigidity, reduced radial stiffness, and good leakage performance. Investigations into leaf seal mechanical and flow performance have been conducted by previous researchers. However, limited understanding of the thermal behavior of contacting leaf seals under sustained shaft contact has led to the development of an analytical model in this study, which can be used to predict the power split between the leaf and rotor from predicted temperature rises during operation. This enables the effects of seal and rotor thermal growth and, therefore, implications on seal endurance and rotor mechanical integrity to be quantified. Consideration is given to the heat transfer coefficient in the leaf pack. A dimensional analysis of the leaf seal problem using the method of extended dimensions is presented, yielding the expected form of the relationship between seal frictional power generation, leakage mass flow rate, and rotor temperature rise. An analytical model is derived which is in agreement. Using the derived leaf temperature distribution formula, the theoretical leaf tip temperature rise and temperature distributions are computed over a range of mass flow rates and frictional heat values. Experimental data were collected in high-speed tests of a leaf seal prototype using the Engine Seal Test Facility at Oxford University. These data were used to populate the analytical model and collapsed well to confirm the expected linear relationship. In this form, the thermal characteristic can be used with predictions of mass flow rate and frictional power generated to estimate the leaf tip and rotor temperature rise in engine operation.

scholarly journals On-Sun Performance Evaluation of Alternative High-Temperature Falling Particle Receiver Designs

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Clifford K. Ho ◽  
Joshua M. Christian ◽  
Julius E. Yellowhair ◽  
Kenneth Armijo ◽  
William J. Kolb ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Particle Temperature ◽  
Free Fall ◽  
Mass Flow Rates ◽  
Mesh Structures ◽  
Free Falling ◽  
The Impact

This paper evaluates the on-sun performance of a 1 MW falling particle receiver. Two particle receiver designs were investigated: obstructed flow particle receiver versus free-falling particle receiver. The intent of the tests was to investigate the impact of particle mass flow rate, irradiance, and particle temperature on the particle temperature rise and thermal efficiency of the receiver for each design. Results indicate that the obstructed flow design increased the residence time of the particles in the concentrated flux, thereby increasing the particle temperature and thermal efficiency for a given mass flow rate. The obstructions, a staggered array of chevron-shaped mesh structures, also provided more stability to the falling particles, which were prone to instabilities caused by convective currents in the free-fall design. Challenges encountered during the tests included nonuniform mass flow rates, wind impacts, and oxidation/deterioration of the mesh structures. Alternative materials, designs, and methods are presented to overcome these challenges.

scholarly journals Numerical and Experimental Study of Microchannel Performance on Flow Maldistribution

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 323 ◽  
Author(s):  
Jojomon Joseph ◽  
Danish Rehman ◽  
Michel Delanaye ◽  
Gian Luca Morini ◽  
Rabia Nacereddine ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Experimental Studies ◽  
Wire Mesh ◽  
Pressure Losses ◽  
Macro Scale ◽  
Flow Maldistribution

Miniaturized heat exchangers are well known for their superior heat transfer capabilities in comparison to macro-scale devices. While in standard microchannel systems the improved performance is provided by miniaturized distances and very small hydraulic diameters, another approach can also be followed, namely, the generation of local turbulences. Localized turbulence enhances the heat exchanger performance in any channel or tube, but also includes an increased pressure loss. Shifting the critical Reynolds number to a lower value by introducing perturbators controls pressure losses and improves thermal efficiency to a considerable extent. The objective of this paper is to investigate in detail collector performance based on reduced-order modelling and validate the numerical model based on experimental observations of flow maldistribution and pressure losses. Two different types of perturbators, Wire-net and S-shape, were analyzed. For the former, a metallic wire mesh was inserted in the flow passages (hot and cold gas flow) to ensure stiffness and enhance microchannel efficiency. The wire-net perturbators were replaced using an S-shaped perturbator model for a comparative study in the second case mentioned above. An optimum mass flow rate could be found when the thermal efficiency reaches a maximum. Investigation of collectors with different microchannel configurations (s-shaped, wire-net and plane channels) showed that mass flow rate deviation decreases with an increase in microchannel resistance. The recirculation zones in the cylindrical collectors also changed the maldistribution pattern. From experiments, it could be observed that microchannels with S-shaped perturbators shifted the onset of turbulent transition to lower Reynolds number values. Experimental studies on pressure losses showed that the pressure losses obtained from numerical studies were in good agreement with the experiments (<4%).

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