Receiver Tube Research Articles

Geometrical variation in receiver tube of SEGS LS-2 parabolic trough collector (PTC) based on heat flux distribution to improve the thermal performance

Heat flux (HF) distribution around the receiver tube of parabolic trough collectors (PTC) has a crucial effect on their outlet temperature (To) and thermal efficiency (ηth). Since its receiver tube is as a heat exchanger, the higher amounts of ηthcan be achieved by changing the geometry of the receiver tube. In previous researches, the geometrical variations were made in the internal geometry of the receiving tube, such as the use of corrugated paths, the installation of fins, using porous media, using twisted tape, etc. In this work, changes are simultaneously made in the internal and external geometry of the receiving tube, which is for the first time based on the model of HF distribution around the receiver tube. These changes include usVηing and moving the receiver's central plug, and creating concavities on the receiver tube to augment the contact surface of the wall with the internal working fluid. These concavities are created in regions of the tube that have a higher heat transfer to increase the heat transfer rate as a fin. In order to generate various HFs around the receiver tube and consequently create different arrangements of fins, two types of PTCs have been used in this research. To compare the improvement of each case-studies rather than smooth case, two indices of efficiency-based (VfNu) and two-objective evaluation () are defined. Finally the results show that, in view point of Vη index, PTC with three-piece reflector and also with the central plug as well as the big fins can give the optimum results than the other case-studies. On the other hand, considering the index of VfNu, the conventional PTC with E.F = 2/3 and the big fins can give the optimum results.

Investigating Study of New Enhanced Parabolic Solar Collector Trough

Parabolic solar collector (PSC) was one of the most public used methods for heating purposes. This study modified PSC and increase its efficiency with minimum cost and space. A passive enhancement on PSC by adding fins on the outside tube surface was done. A copper tape was molded with a triangular fin shape around the copper receiver tube to increase the receiver tube’s heat-absorbing surface area. This enhancement increases the PSC thermal performance. The solar parabola collector has a length of 1 m while its width was 0.2m. The tube receiver has a 1m length with inside and outside diameters of 2.46cm and 2.54cm, respectively. Each fin has a 1 cm base and 1 cm height. The total number of triangular fins around the receiver tube was 100, which significantly enhanced PSC’s thermal performance. The readings were collected for fifteen days, with ten hours of continuous PSC automatic operation. The new SPC thermal performance was a promising technique with a low cost and efficient process compared to the traditional one with the same dimensions. The effect of volumetric flow rates was also studied where their values for 3, 5, 7, and 9 l/min. are 87.12%, 81.78%, 75.72%, and 58.53%, respectively.

Recovery of Partial Heat of Pyrolysis From Solar Thermal Collector for Thermochemical Conversion of Food Waste

Abstract Biomass conversion processes can be energy intensive. There is a need to seek renewable sources to meet such energy demand. In this study, a partial heat of pyrolysis from a concentrated solar power (CSP)-based solar heat collector is modeled. A numerical investigation of the flow in the heat collector element (HCE) of the CSP is performed. By using the finite volume formulation, the fluid flow behavior within the pipe of the HCE is simulated to determine the thermal absorption, heat losses, and efficiency obtainable from the solar irradiation on the receiver tube. Monte-Carlo Ray-tracing based software, soltrace, is used to estimate the incident heat flux on the LS-2 receiver with an average direct normal irradiance (DNI) value, based on a comparative performance study of three types of molten salts (i.e., the heat transfer fluids (HTFs)). The performance of three kinds of the LS-2 HCE (i.e., vacuum, air-filled, and evacuated types) is also analyzed in terms of heat loss and efficiency measurements respectively. HITEC provides the best performance in terms of stability in delivering the partial heat of pyrolysis for the gasification of food waste on moderate velocities of 0.75—2 m/s. Also, the pyrolysis of the feedstock is proposed with an operating feedstock rate of 0.19 kg/s and 0.17 kg/s for lower heating value (LHV) and higher heating value (HHV), respectively. It is anticipated that the combined heat of pyrolysis from the proposed dual heat cycle, comprising both the CSP and a biogas plant, will provide a solution to the demand for alternative power from biomass energy conversion.

An Experimental Study on New Multistage Solar Parabolic Trough Collector

Solar parabolic collector is a clean a promising traditional technique due to the deficiency in energy resources. A new designed multistage solar parabolic trough collector was proposed and its thermal performance was investigated in this study. The collector width and length are 1m with a copper receiver tube outside and inside diameters of 2.54cm, 2.46cm, respectively. Four buses tube receiver were proposed inside the parabolic collector fitted in a thermocouple at the entrance and exit regions of each bus. A solar tracker with a solar sensor for maximum collecting incident sun rays from the sun rise to sun set. The test section is covered with a glass sheet for easy cleaning and to protect the system from losing heat to the surrounding. To evaluate the thermal performance of the new collector, several variables were studied which are: temperature difference between the fluid inlet and outlet regions, heat absorbed by the collector, convective heat transfer rate, and collector thermal efficiency. All the studied variables show that minimum water volumetric flow rates will give max temperature difference between the fluid inlet and outlet regions, heat absorbed by the collector, convective heat transfer rate, and collector thermal efficiency respectively.

Thermal performance enhancement of direct absorption solar collector using nanoparticle in sunray trap

In this work, adapted from the concept of cavity, a new model of receiver tube presented and used in one direct-absorption solar collector (DASC) equipped with two linear parabolic reflectors (LPR). Using both the insulated wall and the cavity-like receiver tube minimize the energy loss in this new-presented receiver tube. Its other advantage is the increase of sun-rays path length created by the sequential reflections of rays in the receiver tube which leads to the attenuation of nanoparticle agglomeration. Therefore, the effect of mentioned two advantages of receiver tube as well as the effect of nanoparticles is analyzed separately. The new presented receiver tube with the absorbent walls is utilized in surface-base solar collector (SBSC) to survey the effect of using the nanoparticle. Also, to investigate the effect of using new-presented absorber tube in SBSC, the obtained results are compared with the conventional type of SBSC. For these purposes, after the sun-rays tracing conducted by a mathematical method, the numerical simulation is carried out by COMSOL software to investigate some effective parameters. Accordingly, using nanoparticle in the new-presented DASC enhances the efficiency by 5% than SBSC. Also, using the new presented cavity-like receiver tube in SBSC augments the efficiency up to 2% rather than conventional LS-2 collector. Finally, as the prominent finding of the current work, the highly-efficient DASC (i.e., 81%) can be achieved using the lower percentage of nanoparticle (i.e., α=0.07).

Thermal performance of solar collector based on volumetric absorption harvesting method using Fe3O4 nanofluid

In this study, the characteristics of volumetric absorption for solar harvesting using a Fe3O4@polyacrylic acid (PAA) nanofluid (NF) are investigated experimentally. The concentration of the Fe3O4@PAA NF was varied from 0 to 0.2wt%, and its mass flow rate was set to 0.0025 and 0.005 kg/s. As a result, the average efficiency of the solar collector at the Fe3O4@PAA NF of 0.05wt% was the highest at the mass flow rates of 0.0025 kg/s and 0.005 kg/s and the improvement ratio of average efficiency was 1.15 and 1.19, respectively, compared to water. The collector performance of the solar thermal harvesting improved owing to the improvement in the solar absorption and heat transfer, as well as the uniform temperature at the receiver tube as the concentration of the Fe3O4@PAA NF increased to a concentration of 0.05wt%. However, the collector performance of the solar thermal harvesting decreased for the 0.05wt% Fe3O4@PAA NF because of the increase in heat loss by the non-uniform temperature at the receiver tube and heat transfer. The increase in mass flow rate can reduce the heat loss by the decrease in temperature in the receiver tube; consequently, the efficiency of the solar collector using NFs is improved.

Contribution to the Parametric Study of the Performance of A Parabolic Trough Collector

This paper presents an analysis of the performance of a parabolic trough collector (PTC) according to some key operating parameters. The effects of the secondary reflector, the length and thickness of the absorber tube (receiver tube) and the flow rate of the heat transfer fluid (HTF) are investigated. The main objective is to determine an optimal operation, which improves the performance of a traditional PTC. The target variables are the temperature at the outlet of the tube, the amount of energy collected by the HTF and the efficiency of the system. The solar flux data concern the city of LAGHOUAT located in the south of Algeria. Four days in different seasons are considered. The optical analysis of the system is performed by using the open source SolTrace code. The output of this analysis is used as a boundary condition for the CFD solver. The conjugate heat transfer and the fluid flow through the absorber tube are simulated by using ANSYS-CFX solver. Water is considered as heat transfer fluids. The obtained results show that the use of a curved secondary reflector significantly improves the performance of the traditional PTC. As the thickness of the tube increases, the heat storage in the material increases, which increases the temperature at the exit of the tube and therefore the efficiency of the system. However, the length of the tube depends on the mass flow of the HTF and vice versa. To keep the efficiency constant by choosing another length, it is necessary to choose a mass flow rate proportional to the flow rate corresponding to the initial length.

Design and Thermal Analysis of Nanofluid-Based Compound Parabolic Concentrator

Given the enormous demand for intermediate temperature applications such as heating, cooling, desalination and process industry; it is imperative to develop efficient low-cost solar thermal systems. Although, non-concentrating collectors are ubiquitous, these are limited by the maximum achievable temperatures. To enhance the existing efficiencies and temperatures without the requirements for diurnal tracking of the sun; volumetric absorption-based receivers employing non-imaging concentrators hold promise. In the present work, we are proposing a nanofluid based volumetrically absorbing receiver housed in a novel compound parabolic concentrator (NCPC). Herein, we synergize the benefits of volumetric absorption and non-imaging concentrators for enhancing the output temperatures without increasing the collector area. Detailed analysis reveals that 6.5 °C higher temperature rise has been achieved with CPC as compared to non-concentrating collector under similar operating conditions and for a given collector surface area. Furthermore, it has been found that the performance of the nanofluid based CPC depends mainly on the volume fraction of nanoparticles and mass flow rate. Finally, the benefit of using two glass tubes receiver with vacuum over the single glass tube receiver has also been quantified; 18 °C higher temperature could be achieved with the two-glass tube receiver design.

Electrolytic Deposition of Ni/NiO on Stainless Steel for Production of Selective Surfaces

Abstract The solar energy is one of the most promising energy sources today. In this context, the goal of this work is to produce selective surfaces for receiver tubes of parabolic trough collectors (PTCs). Ideally, solar collectors should have an absorbing surface that has high absorptance for radiation in the solar energy spectrum and, at the same time, low emittance. Therefore, Ni/NiO selective surfaces were produced with Ni in the first film and NiO in the second film. The method used was by electrolytic deposition of nickel on stainless steel AISI 304, followed by oxidation in a muffle furnace. The thicknesses of the coatings were measured with the photometer Digimess, making it possible to verify their variations and the surface irregularities typical of the electrodeposition procedure. The NiO film was observed in scanning electron microscope (SEM). The film hardness was evaluated by the pencil hardness test and the adhesion by the tape test.

Research advancements and challenges in the design and fabrication of glass to metal seals for solar receiver tube applications

Glass to metal joints has a vast field of application due to their distinct properties in terms of electric conductivity, thermal conductivity, transparency, emissivity, reflectivity, coefficient of thermal expansion (CTE), density, wettability, and crystalline structure. This wide diversification in their properties makes this combination very useful in the special application like concentrated solar receiver tubes (CSRT), etc. This challenge becomes bigger when such seals are subjected to a very high temperature range, ultra-high pressure or ultra-high vacuum, and also gone through repeated number of thermal cycling over a period of time, as may be in the case of CSRT. Hence how to prepare a good quality seal for such constraints, study and control of many factors are essential covered such as seal design, oxidation layer thickness, manufacturing method, temperature and time of making seal, surface roughness, and residual stresses in glass, etc., that has been vigorously studied and reported in this paper.

The efficiency of linear Fresnel reflectors in producing superheated steam for power plant drive

Solar energy is one of the most important sources of renewable energies, which is widely used in many fields, such as electricity production through direct production of superheated steam based on Linear Fresnel Reflector. This study aims to show the optical and thermal behavior of linear Fresnel solar reflectors field directed to the electricity production in El-Oued region at Algeria. Four days of different weather data have been selected to track the change in solar field performance. Numerical optical modeling has shown that the optical performance of the solar field has reached 53.60 %, while the thermal study based on the numerical solution of the energy balance equations of the receiver tube proved that the thermal efficiency was 37.3 % and the average thermal loss coefficient was limited between 5.72 and 5.98 W/m²K. As for the superheated steam temperature, the lowest value was recorded in December with a value of 501 K. The results obtained are very compelling and encouraging to invest in this low-cost technology.

A review on application of nanomaterials in heat transfer fluid for parabolic trough concentrator

Solar energy harvesting through parabolic trough concentrator is finding wide range of application since it can work in the range of 40 °C to 800 °C. Parabolic trough concentrators are widely used in power generation plants and industrial process heating application as it can operate in the low and medium temperature. This is achieved by the selection of suitable heat transfer fluid in the receiver tube of the concentrator. The thermophysical properties of the working fluid plays an important role in enhancing the overall efficiency of the collector. The conventional heat transfer fluid used are water, ethylene glycol and Theminol oil which operate in the low temperature range. But recent researches in the field reveals that different type of nanofluid, can increase the working temperature of the heat transfer fluid and enhance the thermal conductivity and heat transfer properties of the fluid. This paper reviews the type of nanoparticles suspended in the based fluid forming a nanofluid, preparation techniques, their thermoophysical properties which make it suitable for replacing the conventional heat transfer fluid in the PTC.

Research advancements and challenges in the design and fabrication of glass to metal seals for solar receiver tube applications

Glass to metal joints has a vast field of application due to their distinct properties in terms of electric conductivity, thermal conductivity, transparency, emissivity, reflectivity, coefficient of thermal expansion (CTE), density, wettability, and crystalline structure. This wide diversification in their properties makes this combination very useful in the special application like concentrated solar receiver tubes (CSRT), etc. This challenge becomes bigger when such seals are subjected to a very high temperature range, ultra-high pressure or ultra-high vacuum, and also gone through repeated number of thermal cycling over a period of time, as may be in the case of CSRT. Hence how to prepare a good quality seal for such constraints, study and control of many factors are essential covered such as seal design, oxidation layer thickness, manufacturing method, temperature and time of making seal, surface roughness, and residual stresses in glass, etc., that has been vigorously studied and reported in this paper.

Preliminary Estimation of the Receiver Tube Wall Temperature Under Off-Design Conditions in Linear Fresnel Reflectors Solar Field

Preliminary Estimation of the Receiver Tube Wall Temperature Under Off-Design Conditions in Linear Fresnel Reflectors Solar Field

Numerical investigation on heat transfer of supercritical CO<sub>2</sub> in solar receiver tube in high temperature region

Supercritical CO<sub>2</sub> can be used as a heat transfer fluid in a solar receiver, especially for a concentrating solar thermal power tower system. Such applications require better understanding of the heat transfer characteristics of supercritical CO<sub>2</sub> in the solar receiver tube in a high temperature region. However, most of the existing experimental and numerical studies of the heat transfer characteristics of supercritical CO<sub>2</sub> in tubes near the critical temperature region, and the corresponding heat transfer characteristics in the high temperature region are conducted. In this paper, a three-dimensional steady-state numerical simulation with the standard <i>k</i>-<i>ε</i> turbulent model is established by using ANSYS FLUENT for the flow and heat transfer of supercritical CO<sub>2</sub> in a heated circular tube with an inner diameter of 6 mm and a length of 500 mm in the high temperature region. The effects of the fluid temperature (823–1023 K), the flow direction (horizontal, downward and upward), the pressure (7.5–9 MPa), the mass flux (200–500 kg·m<sup>–2</sup>·s<sup>–1</sup>) and the heat flux (100–800 kW·m<sup>–2</sup>) on the convection heat transfer coefficient and Nusselt number are discussed. The results show that the convection heat transfer coefficient increases while Nusselt number decreases nearly linearly with fluid temperature increasing. Both fluid direction and pressure have negligible effects on the convection heat transfer coefficient and Nusselt number. Moreover, the convective heat transfer coefficient and Nusselt number are enhanced greatly with the increasing of mass flux and the decreasing of heat flux, which is more obvious at a higher heat flux. The influences of buoyancy and flow acceleration on the heat transfer characteristics are also investigated. The buoyancy effect can be ignored within the present parameter range. However, the flow acceleration induced by the high heat flux significantly deteriorates the heat transfer preformation. Moreover, eight heat transfer correlations of supercritical fluid in tubes are evaluated and compared with the present numerical data. The comparison indicates that the correlations based on the thermal property modification show better performance in the heat transfer prediction in the high temperature region than those based on the dimensionless number modification. And Nusselt number predicted by the best correlation has a mean absolute relative deviation of 8.1% compared with the present numerical results, with all predicted data points located in the deviation bandwidth of ±20%. The present work can provide a theoretical guidance for the optimal design and safe operation of concentrating solar receivers where supercritical CO<sub>2</sub> is used as a heat transfer fluid.

Numerical analysis of cavity receiver with parallel tubes for cross-linear concentrated solar system

A comprehensive study to understand important parameters that affects the Cavity Linear Receiver (CLR) performance has been done. In this paper, the combined optical and thermal analysis has been successfully utilized, to investigate the thermal-hydraulic behavior of CLR of cross-linear CSP (CL-CSP) system, which is developed at the Tokyo Institute of Technology proposed a new CSP technology, which is called Cross Linear Concentrating Solar Power (CL-CSP). The first demonstration plant of cross-linear concept has been installed at Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal (23.2599° N, 77.4126° E), the combined analysis was done using a numerical model, which has been validated with literature and experimental test. The numerical model simulates the thermal-hydraulic behavior of CLR with the variation of working condition, surface property, and geometry. The optical efficiency and thermal efficiency are the main performance parameters for the simulation.From the numerical study, distribution of both solar flux and temperature on the receiver tubes shows high non-uniformity in axial and radial direction. Furthermore, the parameters effect on the CLR performance is investigated under general working condition of receiver of 673 K temperature, 0.0925 kg/s mass flow rate, and during solar noon of summer solstice.

Comprehensive mathematical model and efficient numerical analysis of the design parameters of the parabolic trough receiver

A new efficient computational approach for the determination of the main design parameters of the parabolic trough receiver is presented. The approach is based on a classical combination of the Monte Carlo ray tracing method for the optical problem and the 3D finite volume method for the thermo-fluid problem. Unlike previous studies, modeling was carried out using a created fully dimensionless thermo-fluid mathematical model and dimensionless numerical algorithm. Criterial complexes (relations between thermophysical, dynamic and geometrical properties) act as dimensionless variables in a mathematical model. A single criterial dependency for describing the temperature fields for any receiver geometry and any heat transfer fluid type was obtained. A proposed solution is correct for any inlet and ambient temperatures. The impact of concentrator surface errors and the design of a tube receiver on temperature fields was studied as well. The present study is the first attempt to mathematically generalize the thermo-fluid analysis in the parabolic trough receiver. A user can efficiently evaluate and predict all thermo-fluid parameters for chosen parabolic trough concentrator geometry with only one dependency without using costly standard software packages. Obtained data is useful for analysis during both the design and operational stages.

Analysis for a solar stripper design for carbon capture under transient conditions

This paper presents an advanced thermodynamic analysis to design a solar stripper (So-St) field to replace the conventional desorption unit in a post-combustion carbon capture (PCC) plant. By eliminating the large, complex, and costly stripper, a solar collector field (SCF) consisting of a number of So-St arrays is sized to directly release the CO2 gas from the rich solvent under transient conditions. In this study, a design protocol has been developed to address the key design challenges for the evolving two-phase flow in the solar receiver tube analysing the instantaneous flow regime, pressure drop, and vapour molar fraction (VMF) to enhance the heat transfer. This design protocol optimizes the physical properties of the So-St components and eventually leads to the whole So-St field sizing based on the nominal capture capacity. A case-study is demonstrated to capture 1.5M tonneCO2/y from a representative 660 MWe coal-fired power plant in Sydney/Australia. It is found that 22 rich solvent loops that each consists of an array of 6 parallel So-St modules, where each module consists of 6 segments in series is needed. The length/diameter of these So-St segments/modules are optimized for this case-study, and the design procedures are clarified and simplified which can be easily applied for other case-studies. Techno-economic validation of this novel So-St technology is an essential step-forward to fully solarize and autonomies carbon capture industry.

A review on passive methods for thermal performance enhancement in parabolic trough solar collectors

SummaryAmong the diverse renewable energy sources available, solar energy harnessing has become very common in most countries. Various collectors were developed, built and checked to work in various temperature ranges. The parabolic trough solar collector is found to be the most common among the other collectors in applications such as the distribution of process heat and the production of steam. The heat collector part known as receiver tube is one of the key practical devices of parabolic trough solar collector. Numerous research studies have centered on receiver tube to raise its thermal potential. The usage of passive techniques such as provision of inserts in the receiver tube and geometrical changes of receiver tube are efficient strategies for increasing thermal performance. Detailed review of the numerical and experimental studies conducted on heat transfer enhancement strategies that rely on the use of inserts with the use of different working fluids in a parabolic trough solar collector's receiver tube is described in this article. Additionally heat transfer enhancement due to geometrical modification of receiver tube is also presented. Further, on the basis of literature survey, a comparison among various strategies is outlined. These studies show that future work in this area, that is, usage of passive techniques in parabolic trough solar collector will offer further growth.

Parabolic trough photovoltaic/thermal hybrid system: Thermal modeling and parametric analysis

Combining solar energy systems that lead to the maximization of the avail solar energy have become a trend during the recent years. In this context, parabolic trough collector and solar photovoltaics are combined with each other to obtain parabolic trough Photovoltaic/Thermal hybrid system which enables simultaneous generation of electricity and production of hot water. The layout and cogeneration of the system are described comprehensively in this work. The novelty of this work is suggesting a new methodology for conducting thermal modeling of this system which is the thermal resistance analogy and simulating it using iterative procedure. Parametric analysis is carried out in order to investigate the influence of Reynolds number, receiver side length and receiver tube length and absorber thickness on the thermal and electrical performance of the system. The results show that the thermal efficiency decreases with the increase in Reynolds number, where it diminishes by 8.31% and 2.12% in the laminar and turbulent flow, respectively. However, it increases by about 35% when the receiver side length augments from 0.03 m to 0.2 m, and by 0.78% when receiver tube length increases from 4 m to 20 m. On the other hand, the electrical efficiency augments with the rise in Reynolds number where it increases by 38.25% in the laminar flow and 5.78% in the turbulent flow, while it decreases by 10.5% and 2% when the receiver side length and receiver tube length increases. Furthermore, the absorber thickness has no effect on the thermal and electrical behavior of the system where both efficiencies remains almost constant (thermal efficiency of 56.46% and electrical efficiency of 25.34%) with the increase in the absorber thickness from 0.02 m to 0.2 m.