scholarly journals Design and Testing of a Novel Bladed Receiver

2017 ◽  
Author(s):  
Jesus D. Ortega ◽  
Joshua M. Christian ◽  
Clifford K. Ho
Keyword(s):  
Surface Area ◽  
Light Trapping ◽  
Test Facility ◽  
Cfd Modeling ◽  
Discrete Ordinates ◽  
Receiver Design ◽  
Solar Absorptance ◽  
Efficiency Increase ◽  
Back Panel ◽  
Section Viii

Previous research at Sandia National Laboratories showed the potential advantages of using light-trapping features which are not currently used in direct tubular receivers. A horizontal bladed receiver arrangement showed the best potential for increasing the effective solar absorptance by increasing the ratio of effective surface area to the aperture footprint. Ray-tracing analyses using SolTrace were performed to understand the light-trapping effects of the bladed receivers, which enable re-reflections between the fins that enhance the effective solar absorptance. A parametric optimization study was performed to determine the best possible configuration with a fixed intrinsic absorptivity of 0.9 and exposed surface area of 1 m2. The resulting design consisted of three vertical panels 0.584 m long and 0.508 m wide and 3 blades 0.508 m long and 0.229 m wide with a downward tilt of 50 degrees from the horizontal. Each blade consisted of two panels which were placed in front of the three vertical panels. The receiver was tested at the National Solar Thermal Test Facility using pressurized air. However, the receiver was designed to operate using supercritical carbon dioxide (sCO2) at 650 °C and 15 MPa for 100,000 hours following the ASME Boiler and Pressure Vessel Code Section VIII Division 1. The air flowed through the leading panel of the blade first, and then recirculated toward the back panel of the blade before flowing through one of the vertical back panels. The test results of the bladed receiver design showed a receiver efficiency increase over a flat receiver panel of ∼5 – 7% (from ∼80% to ∼86%) over a range of average irradiances, while showing that the receiver tubes can withstand temperatures > 800 °C with no issues. Computational fluid dynamics (CFD) modeling using the Discrete Ordinates (DO) radiation model was used to predict the temperature distribution and the resulting receiver efficiencies. The predicted thermal efficiency and surface temperature values correspond to the measured efficiencies and surface temperatures within one standard deviation. In the near future, an sCO2 flow system will be built to expose the receiver to higher pressure and fluid temperatures which could yield higher efficiencies.

On-Sun Testing of a High Temperature Bladed Solar Receiver and Transient Efficiency Evaluation Using Air

2018 ◽  
Author(s):  
Jesus D. Ortega ◽  
Sagar D. Khivsara ◽  
Joshua M. Christian ◽  
Pradip Dutta ◽  
Clifford K. Ho
Keyword(s):  
Heat Transfer ◽  
Light Trapping ◽  
Heat Fluxes ◽  
Heat Transfer Fluid ◽  
Test Facility ◽  
Flow Loop ◽  
Solar Absorptance ◽  
Cfd Models ◽  
Efficiency Increase ◽  
Solar Receiver

Prior research at Sandia National Laboratories showed the potential advantages of using light-trapping features which are not currently used in direct tubular receivers. A horizontal bladed receiver arrangement showed the best potential for increasing the effective solar absorptance by increasing the ratio of effective surface area to the aperture footprint. Previous test results and models of the bladed receiver showed a receiver efficiency increase over a flat receiver panel of ∼ 5–7% over a range of average irradiances, while showing that the receiver tubes can withstand temperatures > 800 °C with no issues. The bladed receiver is being tested at various peak heat fluxes ranging 75–150 kW/m2 under transient conditions using Air as a heat transfer fluid at inlet pressure ∼250 kPa (∼36 psi) using a regulating flow loop. The flow loop was designed and tested to maintain a steady mass flow rate for ∼15 minutes using pressurized bottles as gas supply. Due to the limited flow-time available, a novel transient methodology to evaluate the thermal efficiencies is presented in this work. Computational fluid dynamics (CFD) models are used to predict the temperature distribution and the resulting transient receiver efficiencies. The CFD simulations results using air as heat transfer fluid have been validated experimentally at the National Solar Thermal Test Facility in Sandia National Labs.

scholarly journals Design and Modeling of Light-Trapping Tubular Receiver Panels

2016 ◽  
Author(s):  
Joshua M. Christian ◽  
Jesus D. Ortega ◽  
Clifford K. Ho ◽  
Julius Yellowhair
Keyword(s):  
Ray Tracing ◽  
Light Trapping ◽  
Test Facility ◽  
Flat Panel ◽  
Element Analysis ◽  
Solar Absorptance ◽  
Analysis And Design ◽  
Cfd Models ◽  
Multiple Receiver ◽  
Heat Shielding

Multiple receiver designs have been evaluated for improved optics and efficiency gains including flat panel, vertical-finned flat panel, horizontal-finned flat panel, and radially finned. Ray tracing using SolTrace was performed to understand the light-trapping effects of the finned receivers. Re-reflections of the fins to other fins on the receiver were captured to give an overall effective solar absorptance. The ray tracing, finite element analysis, and previous computational fluid dynamics showed that the horizontal-finned flat panel produced the most efficient receiver with increased light-trapping and lower overall heat loss. The effective solar absorptance was shown to increase from an intrinsic absorptance of 0.86 to 0.96 with ray trace models. The predicted thermal efficiency was shown in CFD models to be over 95%. The horizontal panels produce a re-circulating hot zone between the panel fins reducing convective loss resulting in a more efficient receiver. The analysis and design of these panels are described with additional engineering details on testing a flat panel receiver and the horizontal-finned receiver at the National Solar Thermal Test Facility. Design considerations include the structure for receiver testing, tube sizing, surrounding heat shielding, and machinery for cooling the receiver tubes.

scholarly journals Calorimetric Evaluation of Novel Concentrating Solar Receiver Geometries With Enhanced Effective Solar Absorptance

2016 ◽  
Author(s):  
Jesus D. Ortega ◽  
Julius E. Yellowhair ◽  
Clifford K. Ho ◽  
Joshua M. Christian ◽  
Charles E. Andraka
Keyword(s):  
Thermal Efficiency ◽  
Solar Power ◽  
Solar Furnace ◽  
Heat Transfer Fluid ◽  
Discrete Ordinates ◽  
Base Case ◽  
Outlet Temperature ◽  
Black Paint ◽  
Solar Absorptance ◽  
Flow Rates

Direct solar power receivers consist of tubular arrays, or panels, which are typically tubes arranged side by side and connected to an inlet and outlet manifold. The tubes absorb the heat incident on the surface and transfer it to the fluid contained inside them. To increase the solar absorptance, high temperature black paint or a solar selective coating is applied to the surface of the tubes. However, current solar selective coatings degrade over the lifetime of the receiver and must be reapplied, which reduces the receiver thermal efficiency and increases the maintenance costs. This work presents an evaluation of several novel receiver shapes which have been denominated as fractal like geometries (FLGs). The FLGs are geometries that create a light-trapping effect, thus, increasing the effective solar absorptance and potentially increasing the thermal efficiency of the receiver. Five FLG prototypes were fabricated out of Inconel 718 and tested in Sandia’s solar furnace at two irradiance levels of ∼15 and 30 W/cm2 and two fluid flow rates. Photographic methods were used to capture the irradiance distribution on the receiver surfaces and compared to results from ray-tracing models. This methods provided the irradiance distribution and the thermal input on the FLGs. Air at nearly atmospheric pressure was used as heat transfer fluid. The air inlet and outlet temperatures were recorded, using a data acquisition system, until steady state was achieved. Computational fluid dynamics (CFD) models, using the Discrete Ordinates (DO) radiation and the k-ω Shear Stress Transport (SST) equations, were developed and calibrated, using the test data, to predict the performance of the five FLGs at different air flow rates and irradiance levels. The results showed that relative to a flat plate (base case), the new FLGs exhibited an increase in the effective solar absorptance from 0.86 to 0.92 for an intrinsic material absorptance of 0.86. Peak surface temperatures of ∼1000°C and maximum air temperature increases of ∼200°C were observed. Compared to the base case, the new FLGs showed a clear air outlet temperature increase. Thermal efficiency increases of ∼15%, with respect to the base case, were observed. Several tests, in different days, were performed to assess the repeatability of the results. The results obtained, so far, are very encouraging and display a very strong potential for incorporation in future solar power receivers.

Hierarchical Nano/Micro-structured Surfaces with High Surface Area/Volume Ratios

2021 ◽  
pp. 1-36
Author(s):  
Ketki Lichade ◽  
Yizhou Jiang ◽  
Yayue Pan
Keyword(s):  
Surface Structure ◽  
Surface Area ◽  
Light Trapping ◽  
High Surface ◽  
High Surface Area ◽  
Three Dimensional ◽  
Structure Design ◽  
Surface Structures ◽  
Structured Surfaces ◽  
Design And Manufacture

Abstract Recently, many studies have investigated additive manufacturing of hierarchical surfaces with high surface area/volume (SA/V) ratios, and their performance has been characterized for applications in next-generation functional devices. Despite recent advances, it remains challenging to design and manufacture high SA/V ratio structures with desired functionalities. In this study, we established the complex correlations among the SA/V ratio, surface structure geometry, functionality, and manufacturability in the Two-Photon Polymerization (TPP) process. Inspired by numerous natural structures, we proposed a 3-level hierarchical structure design along with the mathematical modeling of the SA/V ratio. Geometric and manufacturing constraints were modeled to create well-defined three-dimensional hierarchically structured surfaces with a high accuracy. A process flowchart was developed to design the proposed surface structures to achieve the target functionality, SA/V ratio, and geometric accuracy. Surfaces with varied SA/V ratios and hierarchy levels were designed and printed. The wettability and antireflection properties of the fabricated surfaces were characterized. It was observed that the wetting and antireflection properties of the 3-level design could be easily tailored by adjusting the design parameter settings and hierarchy levels. Furthermore, the proposed surface structure could change a naturally-hydrophilic surface to near-superhydrophobic. Geometrical light trapping effects were enabled and the antireflection property could be significantly enhanced (>80% less reflection) by the proposed hierarchical surface structures. Experimental results implied the great potential of the proposed surface structures for various applications such as microfluidics, optics, energy, and interfaces.

Evaluating the Effective Solar Absorptance of Dilute Particle Configurations

2020 ◽  
Author(s):  
Clifford K. Ho ◽  
Luis F. González-Portillo ◽  
Kevin J. Albrecht
Keyword(s):  
Light Trapping ◽  
Relative Increase ◽  
Representative Elementary Volume ◽  
Average Particle ◽  
Temperature Profiles ◽  
Elementary Volume ◽  
Particle Cloud ◽  
Solar Absorptance ◽  
Effective Particle ◽  
Significant Temperature

Abstract Ray-tracing and heat-transfer simulations of discrete particles in a representative elementary volume were performed to determine the effective particle-cloud absorptance and temperature profiles as a function of intrinsic particle absorptance values (0 – 1) for dilute solids volume fractions (1 – 3%) representative of falling particle receivers used in concentrating solar power applications. Results showed that the average particle-cloud absorptance is increased above intrinsic particle absorptance values as a result of reflections and subsequent reabsorption (light trapping). The relative increase in effective particle-cloud absorptance was greater for lower values of intrinsic particle absorptance and could be as high as a factor of two. Higher values of intrinsic particle absorptance led to higher simulated steady-state particle temperatures. Significant temperature gradients within the particle cloud and within the particles themselves were also observed in the simulations. Findings indicate that dilute particle-cloud configurations within falling particle receivers can significantly enhance the apparent effective absorptance of the particle curtain, and materials with higher values of intrinsic particle absorptance will yield greater radiative absorptance and temperatures.

scholarly journals Dependency of Air Curtain Performance on Discharge Air Velocity (Grille and Back Panel) in Open Refrigerated Display Cabinets

2009 ◽  
Author(s):  
Pedro Dinis Gaspar ◽  
L. C. Carrilho Gonc¸alves ◽  
Andreas Vo¨geli
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Unit Length ◽  
Experimental Tests ◽  
Cfd Modeling ◽  
Air Velocity ◽  
Conservation Area ◽  
Air Curtain ◽  
Numerical Predictions ◽  
Back Panel

This study performs a Computational Fluid Dynamics (CFD) modeling of air flow and heat transfer of an open refrigerated display cabinet in order to evaluate the influence of the discharge air velocity on the performance of its recirculated air curtain. The physical-mathematical model considers the flow through the internal ducts, across the fans and the evaporator, and also the thermal response of food products. The fan boundary condition is modeled in order to vary the air velocity at the discharge grille. The back panel perforation is modeled as a porous medium. The density and dimension of the back panel perforation variation is modeled by the Darcy’s law with the Forchheimer extension, varying the viscous and inertial resistance coefficients of the porous medium, based on its porosity, permeability, air velocity and pressure loss coefficient. Experimental tests were conducted to characterize the phenomena near the physical borders and to prescribe boundary conditions as well as to validate the numerical predictions on the temperature, relative humidity and velocity distributions. The numerical results show that the lowest average temperature in the conservation area of the display cabinet is achieved at a discharge air grille velocity of 1.15 ms−1. This value is lower than the experimental one, 1.51 ms−1, measured on the real equipment. The absence of a velocity component in the third dimension, which can destabilize the air curtain, is assumed to be the reason for this discrepancy. The profiles of the numerical predictions of the air curtain indicate that in the optimum case the air curtain is not so stable to bear big disturbances from outside. In order to increase the thermal performance and to reduce the energy consumption of these equipments, it’s not recommended to run the re-circulated air curtain velocity below 1.15 ms−1. For each CFD model, the values and directions of the air mass flow rate and heat transfer across the re-circulated air curtain by unit length are predicted and compared with the experimental ones in order to evaluate its thermal energy gains and losses.

Design of “SIREC-1” Wire Mesh Open Volumetric Solar Receiver Prototype

2001 ◽  
Author(s):  
Félix M. Téllez ◽  
Manuel Romero ◽  
María J. Marcos
Keyword(s):  
Development Program ◽  
Mesh Size ◽  
Computer Code ◽  
Operating Conditions ◽  
Wire Mesh ◽  
Test Facility ◽  
Receiver Design ◽  
Two Phases ◽  
Set Up ◽  
Solar Receiver

Abstract The paper describes the design and status of development of a new open volumetric air receiver prototype. This receiver design, though developed in two phases, constitutes one deliverable in a Spanish project carried out by CIEMAT, IAER and INABENSA. The project, called SIREC, is partially financed by the European Funds for the Regional Development program (FEDER). The receiver prototype is now in fabrication and will be tested in the Sulzer volumetric receiver test facility at the Plataforma Solar de Almería (PSA) in Spain. Testing is scheduled for April, 2001. The prototype design includes an air return system and modular absorber elements, to facilitate their replacement and reduce manufacturing costs. The absorber is wire mesh. A computer code has been set up to select the mesh size (wire diameter and mesh distance) and number of screens. A sensitivity analysis for a variety of operating conditions has been carried out with this code to guide the absorber design and its testing.

Assessment of Particle Candidates for Falling Particle Receiver Applications Through Irradiance and Thermal Cycling

2021 ◽  
Author(s):  
Nathan Schroeder ◽  
Kevin Albrecht
Keyword(s):  
Thermal Cycling ◽  
Thermal Aging ◽  
Particle Surface ◽  
Solid Particles ◽  
Tube Furnace ◽  
Heat Transfer Fluid ◽  
Test Facility ◽  
Initial Value ◽  
Solar Absorptance ◽  
Hsp 40

Abstract Falling particle receiver (FPR) systems are a rapidly developing technology for concentrating solar power applications. Solid particles are used as both the heat transfer fluid and system thermal energy storage media. Through the direct irradiation of the solid particles, flux and temperature limitations of tube-bundle receives can be overcome, leading to higher operating temperatures and energy conversion efficiencies. Candidate particles for FPR systems must be resistant to changes in optical properties during long term exposure to high temperatures and thermal cycling using highly concentrated solar irradiance. Five candidate particles, CARBOBEAD HSP 40/70, CARBOBEAD CP 40/100, including three novel particles, CARBOBEAD MAX HD 35, CARBOBEAD HD 350, and WanLi Diamond Black, were tested using simulated solar flux cycling and tube furnace thermal aging. Each particle candidate was exposed for 10 000 cycles (simulating the exposure of a 30-year lifetime) using a shutter to attenuate the solar simulator flux. Feedback from a pyrometer temperature measurement of the irradiated particle surface was used to control the maximum temperatures of 775 °C and 975 °C. Particle solar-weighted absorptivity and emissivity were measured at 2000 cycle intervals. Particle thermal degradation was also studied by heating particles to 800 °C, 900 °C, and 1000 °C for 300 hours in a tube furnace purged with bottled unpurified air. Here particle absorptivity and emissivity were measured at 100-hour intervals. Measurements taken after irradiance cycling and thermal aging were compared to measurements taken from as-received particles. WanLi Diamond Black particles had the highest initial value for solar weighted absorptance, 96%, but degraded up to 4% in irradiance cycling and 6% in thermal aging. CARBOBEAD HSP 40/70 particles currently in use in the prototype FPR at the National Solar Thermal Test Facility had an initial value of 95% solar absorptance with up to a 1% drop after irradiance cycling and 4% drop after 1000 °C thermal aging.

Heliostat Characterization at the Central Receiver Test Facility

1981 ◽  
Vol 103 (2) ◽  
pp. 82-88 ◽  
Author(s):  
D. L. King ◽  
D. E. Arvizu
Keyword(s):  
Beam Quality ◽  
Department Of Energy ◽  
Test Facility ◽  
Receiver Design ◽  
Tracking Accuracy ◽  
Design Concepts ◽  
Future Design ◽  
Current State ◽  
Central Receiver ◽  
Accuracy Data

The Central Receiver Test Facility (CRTF) operated for the Department of Energy by Sandia Laboratories in Albuquerque, N. M. was constructed for the purpose of evaluating solar central receiver design concepts. At this facility working experience with the CRTF heliostat field has been gained and an extensive heliostat evaluation capability has evolved. Valuable information has been gained at the CRTF that will help in the future design and specification of heliostats. This paper summarizes the work that led to the current state of heliostat evaluation capability and includes; a description of the CRTF heliostat, measurements of environmental degradation of mirror reflectance, heliostat beam measurements with an instrumented sweeping bar, beam quality and tracking accuracy data obtained with the newly developed Beam Characterization System (BCS) and comparisons of measured beam data with the heliostat computer model HELIOS.

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