Generation of a Radiation Absorbing Medium for a Solar Receiver by Elutriation of Fine Particles From a Spouted Bed

2006 ◽  
Vol 128 (3) ◽  
pp. 406-408 ◽  
Author(s):  
Hanna H. Klein ◽  
Rachamim Rubin ◽  
Jacob Karni
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Fine Particles ◽  
Working Fluid ◽  
Equivalent Diameter ◽  
Spouted Bed ◽  
Thermal Systems ◽  
Absorbing Medium ◽  
Exit Temperature ◽  
Solar Receiver

In high-temperature solar-thermal systems the conversion of solar to thermal energy requires a radiation absorbing surface to transfer the radiative solar energy to the working fluid. The present study focuses on the generation of a moving radiation absorber using particles suspended in the working fluid. Three methods of particle entrainment in a gas were investigated. Elutriating fine particles from a spouted bed was found to be the preferred method. The diameter range of the entrained carbon black particles was 0.030-25μm, with 99.7% of the particles having an equivalent diameter less than 1μm, and 48% of the projected surface area was due to agglomerated particles with average equivalent diameter >5μm. The moving radiation absorber was tested in a solar receiver using nitrogen as a working fluid. The inner wall temperatures in the receiver cavity were below the gas exit temperature, which shows that the bulk heat transfer from the incoming solar radiation to the gas takes place via the moving radiation absorbing particles.

Experimental Evaluation of Particle Consumption in a Particle Seeded Solar Receiver

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Hanna Helena Klein ◽  
Rachamim Rubin ◽  
Jacob Karni
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Carbon Black ◽  
Wall Temperature ◽  
Air Flow ◽  
Operating Conditions ◽  
Working Fluid ◽  
Concentrated Solar Energy ◽  
Exit Temperature ◽  
Solar Receiver

This experimental study shows the behavior of a directly irradiated, high temperature, solar receiver seeded with a low concentration of carbon black particles as the radiation absorbing media in the presence of air or nitrogen as the working fluid. Experiments were conducted in the presence of highly concentrated solar energy with an energy flux of up to 3MW∕m2 at the aperture of the receiver. 99.9% of the particles had an equivalent diameter of <5μm, but the remaining larger agglomerates accounted for 51% of the overall projected surface area. The molar ratio of carbon to gas in the fluid entering the receiver was 0.004–0.008. The heat transfer from the solar radiation to the working gas was accomplished almost exclusively via the particles. The receiver behavior during steady-state operation was evaluated. The receiver gas exit temperatures achieved during the experiments were between 1000 and 1550°C. When nitrogen was used as working gas, its exit temperature exceeded the average wall temperature, whereas when air was used, its exit temperature was lower than the average wall temperature. The air flow may have been heated to some extent by the receiver walls, whereas in the case of nitrogen, the particle-to-gas heat transfer was dominant throughout the receiver. When the gas exit temperature was above 1200°C, the particle seeded nitrogen flow absorbed 12–20% more energy than particle seeded air flow under the same operating conditions (insolation, particle load, flow rate, close proximity in time). The air tests reached high exit temperatures despite the reduction of particle concentration due to combustion. This indicates that heat transfer mainly occurs over a relatively short time period after the particle seeded flow enters the cavity close to the receiver aperture, before significant particle burning takes place. The energy due to carbon combustion was 3–5% of total energy absorbed in the high temperature air experiments. The carbon particles’ oxidation rate in the presence of molecular oxygen was found to be significantly lower than values documented in the literature for high temperature carbon black combustion in air. The high solar flux, which promotes very high radiation→particle→gas heat transfer rate, might account for this retardation.

Heat Pipe Solar Receivers for Concentrating Solar Power (CSP) Plants

2013 ◽  
Author(s):  
Yiding Cao
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Solar Power ◽  
High Heat ◽  
Solar Flux ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Efficient Operation ◽  
High Heat Transfer ◽  
Solar Receiver

This paper introduces separate-type heat pipe (STHP) based solar receiver systems that enable more efficient operation of concentrated solar power plants without relying on a heat transfer fluid. The solar receiver system may consist of a number of STHP modules that receive concentrated solar flux from a solar collector system, spread the high concentrated solar flux to a low heat flux level, and effectively transfer the received heat to the working fluid of a heat engine to enable a higher working temperature and higher plant efficiency. In general, the introduced STHP solar receiver has characteristics of high heat transfer capacity, high heat transfer coefficient in the evaporator to handle a high concentrated solar flux, non-condensable gas release mechanism, and lower costs. The STHP receiver in a solar plant may also integrate the hot/cold tank based thermal energy storage system without using a heat transfer fluid.

Application of Supercritical Pressures in Power Engineering

2017 ◽  
pp. 404-457
Author(s):  
Igor Pioro ◽  
Mohammed Mahdi ◽  
Roman Popov
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
High Temperature ◽  
Gas Turbine ◽  
Power Plants ◽  
Thermal Power ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Thermal Power Plants ◽  
Power Cycles

SuperCritical Fluids (SCFs) have unique thermophyscial properties and heat-transfer characteristics, which make them very attractive for use in power industry. In this chapter, specifics of thermophysical properties and heat transfer of SCFs such as water, carbon dioxide and helium are considered and discussed. Also, particularities of heat transfer at SuperCritical Pressures (SCPs) are presented, and the most accurate heat-transfer correlations are listed. SuperCritical Water (SCW) is widely used as the working fluid in the SCP Rankine “steam”-turbine cycle in fossil-fuel thermal power plants. This increase in thermal efficiency is possible by application of high-temperature reactors and power cycles. Currently, six concepts of Generation-IV reactors are being developed, with coolant outlet temperatures of 500°C~1000°C. SCFs will be used as coolants (helium in GFRs and VHTRs; and SCW in SCWRs) and/or working fluids in power cycles (helium; mixture of nitrogen (80%) and helium [20%]; nitrogen, and carbon dioxide in Brayton gas-turbine cycles; and SCW “steam” in Rankine cycle).

Numerical Analysis of Natural Convection and Radiation for Tube Solar Receiver With Glass Window

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Zhang Guojun ◽  
Liu Changyu ◽  
Li Dong
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Natural Convection ◽  
Heating Temperature ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Surface Emissivity ◽  
Heating Wall ◽  
Convective Coefficient ◽  
Solar Receiver

Conjugate laminar natural convection heat transfer and air flow with radiation of tube solar receiver with glass window were numerically investigated. The discrete ordinate method was used to solve the radiative transfer equation. And the three-dimensional steady-state continuity, Navier–Stokes, and energy equations were solved. The temperature difference based on environment and high temperature surface of receiver is varied from 100 K to 1000 K. The influence of the surface emissivity, heating temperature, convective coefficient, and convective temperature of environment on the heat transfer from the receiver with glass window has also been investigated. The numerical results indicated that the highest temperature of glass window increases and the high temperature area becomes wide, with the temperature of heating wall and surface emissivity increasing. Adopting higher convective coefficient of glass window can reduce the peak magnitude of temperature distribution on glass window of tube receiver up to 45%.

Numerical Simulation of High Temperature Solar Receiver and Thermal Receiver for Solar Micro Gas Turbine

2017 ◽  
Author(s):  
Koji Matsubara ◽  
Sho Isojima ◽  
Mitsuho Nakakura ◽  
Yuji Yamada ◽  
Shota Kawagoe
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
High Temperature ◽  
Gas Turbine ◽  
Impinging Jet ◽  
Combustion Gas ◽  
Micro Gas Turbine ◽  
Thermal Receiver ◽  
The Many ◽  
Solar Receiver

Numerical simulation was made for high-temperature solar and thermal receivers of pressurized air for solar micro gas turbine system. The solar / biomass hybrid gas turbine was considered to generate 30kW to 100kW power. The gas turbine system was provided with the concentrated solar light from the dish reflector at the solar receiver and the combustion heat from the biomass synthesis gas at the thermal receiver. Numerical model was developed to the solar receiver and the thermal receiver to reveal their thermal potential. The solar receiver was a close loop concentric annuli to receive highly condensed solar light of 1,000kW/m2. The inner cylinder was made of high-temperature resistance ceramic irradiated by the condensed light on the inner side. The liner was inserted between the inner cylinder and the outer shell. The pressurized air passes the many holes of the liner to impinge the outer surface of the irradiation wall. These impinging jets caused high heat transfer coefficient on the irradiation wall and alleviates the thermal distribution in the receiver aisle. The liner and the outer shell were made by the high temperature resistance INCONEL alloy. The thermal receiver was also a close loop annuli. This uses the same part as the solar receiver and the biomass gas combustor combined to it. The combustor comprises of the liner and the center tube, installed to the inside of the ceramic cylinder. The biomass gas was provided to the gap between liner and the center tube, and the oxidant air to the outer side of the liner. The biomass gas was spouted from the many holes of the liner and mixed with the oxidant air. The resulted hot combustion gas impinged directly to the inner side of the ceramic cylinder. The impingement of the hot combustion gas thinned the thermal boundary layer and enhanced the heat transfer on the ceramic wall. The thermal receiver was designed to attain the preferable heat transfer performance by the inner impinging jet of the hot combustion gas as well as the outer impinging jet of the pressurized air. Three dimensional numerical model was developed to the solar receiver and the thermal receiver considered in the present study using ANSYS FLUENT. Parameter study showed that the exit air from the solar receiver was heated above 1200K or higher presently, and was continued to search better condition and better configuration of the system to obtain higher temperature. The numerical simulation revealed that the distance from the jet nozzle (linear holes) and the heat transfer surface is critical to the thermal distribution. The concept of the new solar and thermal receivers was confirmed on their usefulness; the multiple impinging jet effectively enhanced the heat transfer on the ceramic wall of the solar receiver and the thermal receiver to reduce the thermal inhomogeneity near the heat transfer surface with pressure loss of order 800Pa.

scholarly journals Thermal Stress and Deformation of Hollow Paddle-Shaft Components with Internal High Temperature Molten Salt Flow

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1557
Author(s):  
Taha Rajeh ◽  
Basher Hassan Al-Kbodi ◽  
Houlei Zhang
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
High Temperature ◽  
Stress Distribution ◽  
Molten Salt ◽  
Heat Exchangers ◽  
Von Mises Stress ◽  
Working Fluid ◽  
Stress And Deformation ◽  
Salt Flow

Excessive thermal stress and deformation are important reasons causing disservice of high temperature heat exchangers. This paper presents thermal stress and expansion analysis of single-leaf type hollow paddle-shaft components with internal high temperature molten salt flow based on three-dimensional numerical simulations. The results show that the hollow paddles enhance the heat transfer and decrease the maximum thermal stress simultaneously with the expense of a much higher pressure drop than that of solid paddles. The cumulative von Mises stress distribution curve shows that the stress distribution of the component with hollow paddles is more uniform than that with solid paddles. The radial and axial deformations do not differ much for the components with hollow and solid paddles. A larger volume of the fluid space in the hollow paddles leads to stronger heat transfer, smaller maximum thermal stress, and more uniform stress distribution. The effects of the paddle height, the diameter and number of flow holes, the molten salt flow rate, and the material-side heat transfer coefficient are identified. The advantages of hollow paddle designs in both heat transfer and thermal stress (local and overall) performance are revealed. The work in this study can provide a reference for the design and optimization of hollow paddle heat exchangers with high temperature molten salt as working fluid.

Effects of a High Porous Material on Heat Transfer and Flow in a Circular Tube

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Koichi Ichimiya ◽  
Tetsuaki Takeda ◽  
Takuya Uemura ◽  
Tetsuya Norikuni
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Porous Material ◽  
Entropy Generation ◽  
Circular Tube ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Equivalent Diameter

This paper describes the heat transfer and flow characteristics of a heat exchanger tube filled with a high porous material. Fine copper wires (diameter: 0.5 mm) were inserted in a circular tube dominated by thermal conduction and forced convection. The porosity was from 0.98 to 1.0. The working fluid was air. The hydraulic equivalent diameter was cited as the characteristic length in the Nusselt number and the Reynolds number. The Nusselt number and the friction factor were expressed as functions of the Reynolds number and porosity. The thermal performance was evaluated by the ratio of the Nusselt number with and without a high porous material and the entropy generation. It was recognized that the high porous material was effective in low Reynolds numbers and the Reynolds number, which minimized the entropy generation existed.

Suitability of various heat transfer fluids for high temperature solar thermal systems

2019 ◽  
Vol 159 ◽  
pp. 113973 ◽  
Author(s):  
Ravindra Vutukuru ◽  
A. Saikiran Pegallapati ◽  
Ramgopal Maddali
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Solar Thermal ◽  
Thermal Systems ◽  
Heat Transfer Fluids

scholarly journals Numerical investigation on heat transfer of supercritical CO2 in solar receiver tube in high temperature region

2021 ◽  
Vol 70 (3) ◽  
pp. 034401-034401
Author(s):  
Zhuang Xiao-Ru ◽  
◽  
Xu Xin-Hai ◽  
Yang Zhi ◽  
Zhao Yan-Xing ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Numerical Investigation ◽  
Temperature Region ◽  
High Temperature Region ◽  
Solar Receiver
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