Inclination Angle Of Cavity Research Articles

Analysis of heat transfer modes in the cooling of blocks generating different heat quantities

Achieving improved cooling efficiency and control in electronic components with varying heat outputs can be realized through a thorough analysis of different heat transfer modes, focusing on their contributions and interactions within the system. The analysis is conducted within a cavity containing three circular blocks generating varying amounts of heat. The blocks are affixed to an insulated plate, dividing the cavity into two identical sections with different fluids and different cooling mechanisms. In the open portion of the divided cavity, block cooling is achieved through forced convection using a nanofluid, while the closed section dissipates heat through natural convection and surface radiation. The numerical solution of the governing equations is performed using Galerkin's Finite Element Method, with detailed examination of the cooling process considering various parameters, such as block displacement (1.5cm≤y1≤3.25cm) and dimensions (0.25cm≤R≤1.5cm), Reynolds number (10≤Re≤1000), nanoparticles nature and volumetric fraction(0 %–10 %), emissivity (0≤ε≤1), thermal heat ratio(0.125 to 8), and cavity inclination angle(0°–180°). The results show that the combination of natural convection and surface radiation can be highly effective, rivaling forced convection in cooling the blocks. The study shows that an increase in the Reynolds number results in a temperature reduction of up to 6 °C, while increasing the emissivity leads to a more significant drop of around 10 °C. Additionally, miniaturizing the blocks by reducing their radius by a factor of six causes the maximum temperature to rise by over 20 °C.

Enhancing gas drainage efficiency in soft coal seams: Mechanically over-excavated cavities along borehole in floor tunnels

In addressing the challenge of gas drainage in soft coal seams, this study introduces an innovative technique involving mechanically over-excavated cavities along boreholes in floor tunnels. Through a combination of laboratory experiments, numerical simulations, and field tests, we investigate the efficacy of this method in weakening the coal structure and enhancing gas extraction. The influence of cavity parameters (inclined angle, cavity length and diameter, cavity number) on the mechanical properties and AE behavior of coal specimens were investigated by biaxial compression tests. Besides, the stress distribution and permeability evolution around the cavity were studied using FLAC3D combined with COMSOL software. Finally, the field tests were conducted in LiCun Coal Mine. The results indicate that a significant reduction in the compressive strength of coal specimens with increasing cavity dimensions. Notably, the peak stress in coal specimens decreased significantly as the cavity length, diameter, and number increased, by up to 42.09%, 39.38%, and 57.83%, respectively. In contrast, the peak stress increased with the cavity inclination angle, and it was about 1.14 times higher for specimens with a 90° angle than for those with a 15° angle. It is also found that the cavity inclination reduces the damage and acoustic emission activity of the specimen, while the cavity volume increases them and weakens the rock-bearing capacity. The failure modes of all specimens are shear failure combined with surface spalling. Numerical simulations employing FLAC3D and COMSOL software corroborated these results, demonstrating enhanced pressure relief and increased permeability around the cavities. Field tests conducted in the LiCun Coal Mine provided practical evidence of the method's efficacy, with a more than 3-fold increase in gas drainage concentration and volume observed compared to traditional drilling methods. By adopting mechanically over-excavated cavities, not only is the efficiency of gas drainage significantly improved, but also the safety and productivity of mining operations are enhanced. This study offers a promising and impactful solution for addressing gas drainage challenges in soft coal seams.

Turbulent natural convection inside inclined enclosures: Effects of adiabatic and heat-conducting inserts

Natural convection phenomena are found in many engineering applications, ranging from building and refrigeration design to nuclear reactors. Such importance has prompted both experimental and numerical studies aiming at enhancing heat transfer characteristics. Turbulent natural convection in closed cavities, apparently simple, is a stepstone to such problems, which require mathematical and numerical tools capable of providing accurate results. This work is inserted within this framework, in which influences of insert size and type (adiabatic/heat-conducting), and cavity inclination angle are assessed for Rayleigh numbers 10 7 ≤ Ra ≤ 10 9 . The study shows that the insert is mostly detrimental to heat transfer owing to restriction to recirculation, irrespective of the cavity inclination angle. An operation envelope for the global Nusselt number for all cavity inclination angles, insert sizes and types, and Rayleigh numbers was also determined.

Numerical simulation of heat transfer and entropy generation due to the nanofluid natural convection with viscous dissipation in an inclined square cavity

In this work, the effects of viscous dissipation on heat transfer and entropy generation of the nanofluid natural convection in an inclined square cavity are numerically investigated. A fractional-step semiimplicit finite difference algorithm based on the projection method on a staggered grid is proposed to solve the laminar natural convection problem, which has the advantage of larger time steps. The square cavity is filled with a nanofluid composed of (Cu) copper nanoparticles and water. and the viscous dissipative behavior of the mixture flow is not negligible. The studied parameters are Rayleigh number Ra ( 10 4 and 10 5 ), Eckert number Ec ( 0 − 2 ), the volume fraction of solid particles ϕ ( 0 − 0.06 ), and inclination angle of square cavity α ( 0 − π / 2 ). The Prandtl number is fixed to Pr = 6.2 . The results show that at any inclination angle, the increase in viscous dissipation leads to weakened heat transfer on the hot wall, enhanced heat transfer on the cold wall, and weakened flow in the square cavity. For the base solution without nanoparticles, the Eckert number has the greatest impact, with its effects on the average Nusselt number on the hot wall, maximum streamfunction, and average Nusselt number on the cold wall being ∼13, 0.15, 18.69%, and at Ra = 10 4 , and 12, 0.5, 28.87% at Ra = 10 5 , respectively. Research on entropy generation shows that as Eckert number increases, the entropy generation due to heat transfer increases, while due to fluid friction decreases. As the Rayleigh number increases, the effect of viscous dissipation increases. As the inclination angle increases, the effects of volume fraction and Eckert number weaken. Adding solid particles can effectively weaken the effect of viscous dissipation.

Fluid flow and heat transfer analysis of a ternary aqueous Fe3O4 ＋ MWCNT ＋ Cu/H2O magnetic nanofluid in an inclined rectangular porous cavity

The natural convective flow and heat transfer efficiency within a cavity have been utilized in various applications, such as solar collectors, heat exchangers, and cooling electronic devices. Ternary nanofluids have higher heat transfer features than nanofluids. Motivated by the aforementioned applications, the current study investigates the natural convective flow and thermal efficiency features of Fe3O4+MWCNT+Cu/H2O electroconductive ternary nanofluid-filled inclined, partially heated rectangular porous cavity under the impacts of an inclined magnetic field, heat source/sink, Joule heating, a resistance porous medium, and viscous dissipation. Additionally, to examine the best heat transfer rate performance of ternary nanofluids, different combinations of aqueous-based ferromagnetic, metallic, and carbon-based nanoparticles’ are also scrutinized. The considered system of equations with suitable initial–boundary conditions is solved by the Marker and Cell method. The results reveal that pertinent parameters such as Darcy number, Rayleigh number, cavity inclination angle, nanoparticle volume fraction, and heat source/sink have significant impacts on the convective flow regime. The investigation reflects that in the presence of a heat source, by augmenting the Fe3O4(33.3%),MWCNT(33.3%), and Cu(33.3%) nanoparticles’ volume fractions from 1% to 5%, the average heat transfer rate is increased by 7.49%. By considering Fe3O4(10%),MWCNT(45%), and Cu(45%) nanoparticles, the average heat transfer rate can be increased up to 8.95%. Fe3O4(10%)+MWCNT(45%)+Cu(45%)/H2O ternary nanofluids deliver the highest, and Fe3O4(45%)+MWCNT(45%)+Cu(10%)/H2O ternary nanofluids produce the lowest rate of heat transfer among the other combinations of ternary nanofluids. This outcome ensures that a suitable combination of nanoparticles extensively improves the heat transfer characteristics of the base fluids.

Entropy generation and heat transfer performance analysis of a non-Newtonian NEPCM in an inclined chamber with complicated heater inside

The present research deals with thermic energy storage structures based on nano-encapsulated phase change material with a complicated charger inside the storage system. Flow structures, heat transfer, and entropy generation performance are studied using the partial differential governing equations based on non-Newtonian nature of the working medium. Analysis has been performed numerically using the finite element method. Effects of the cavity inclination angle, inner charger structure, power-law index for non-Newtonian nature of the working liquid, Rayleigh number, and nanoparticles volume fraction on flow structures, entropy generation fields and temperature fields have been studied. It has been found that the considered dilatant working fluid is not effective for the heat transfer applications, because Nusselt number decreases with a growth of the power-law index. At the same time, the cavity inclination angle and inner heater structure can be effective parameters to manage the heat transfer and entropy generation.

Design and Experimental Study of Cavity Structure of Pneumatic Soft Actuator

In order to study the influence of the cavity inclination angle bending performance of pneumatic soft actuators, two kinds of soft actuators were designed, one with a five-degree-angle cavity structure, and the other with a hybrid variable-degree-angle cavity structure. The bending performance of zero-degree-angle, five-degree-angle, and hybrid variable-degree-angle soft actuators was investigated by experimental methods and the ABAQUS finite element simulation method. The results show that, under seven different pressure loads, the mean absolute error between the experimental results and the numerical simulation results for the zero-degree-angle soft actuator was 0.926, for the five-degree-angle soft actuator it was 1.472, and for the hybrid variable-degree-angle soft actuator it was 1.22. When the pressure load changed from 4 kPa to 16 kPa, the five-degree-angle soft actuator had the largest range-of-angle variation, with the bending angle increasing 193.31%, from 26.92 degrees to 78.97 degrees. In the same longitudinal displacement, the five-degree-angle soft actuator had the largest lateral displacement variation, and the bending effect was the best compared with the zero-degree-angle soft actuator and the hybrid variable-degree-angle soft actuator. According to the experimental and numerical simulation results, with the same structural parameter design, the cavity tilt angle increases, which can increase the bending angle variation range and improve the bending performance of soft actuators.

Numerical computation on MHD natural convective ternary nanofluid flow and heat transfer in a porous square cavity: Marker-and-cell technique

PurposeThe analysis of fluid flow and thermal transport performance inside the cavity has found numerous applications in various engineering fields, such as nuclear reactors and solar collectors. Nowadays, researchers are concentrating on improving heat transfer by using ternary nanofluids. With this motivation, the present study analyzes the natural convective flow and heat transfer efficiency of ternary nanofluids in different types of porous square cavities.Design/methodology/approachThe cavity inclination angle is fixed ω = 0 in case (I) and in case (II). The traditional fluid is water, and is treated as a working fluid. Ternary nanofluid's thermophysical properties are considered, according to the Tiwari–Das model. The marker-and-cell numerical scheme is adopted to solve the transformed dimensionless mathematical model with associated initial–boundary conditions.FindingsThe average heat transfer rate is computed for four combinations of ternary nanofluids: and under the influence of various physical factors such as volume fraction of nanoparticles, inclined magnetic field, cavity inclination angle, porous medium, internal heat generation/absorption and thermal radiation. The transport phenomena within the square cavity are graphically displayed via streamlines, isotherms, local and average Nusselt number profiles with adequate physical interpretations.Practical implicationsThe purpose of this study is to determine whether the ternary nanofluids may be used to achieve the high thermal transmission in nuclear power systems, generators and electronic device applications.Social implicationsThe current analysis is useful to improve the thermal features of nuclear reactors, solar collectors, energy storage and hybrid fuel cells.Originality/valueTo the best of the authors’ knowledge, no research has been carried out related to the magneto-hydrodynamic natural convective ternary nanofluid flow and heat transmission filled in porous square cavities with an inclined cavity angle. The computational outcomes revealed that the average heat transfer depends not only on the nanoparticle’s volume concentration but also on the existence of heat source and sink.

CuO–Water MHD Mixed Convection Analysis and Entropy Generation Minimization in Double-Lid–Driven U-Shaped Enclosure with Discrete Heating

Abstract The present study explores magnetic nanoliquid mixed convection in a double lid–driven U-shaped enclosure with discrete heating using the lattice Boltzmann method (LBM) numerical method. The nanoliquid thermal conductivity and viscosity are calculated using the Maxwell and Brinkman models respectively. Nanoliquid magnetohydrodynamics (MHD) and mixed convection are analyzed and entropy generation minimisation has been studied. The presented results for isotherms, stream isolines and entropy generation describe the interaction between the various physical phenomena inherent to the problem including the buoyancy, magnetic and shear forces. The operating parameters’ ranges are: Reynolds number (Re: 1–100), Hartman number (Ha: 0–80), magnetic field inclination (γ: 0°– 90°), nanoparticles volume fraction (ϕ: 0–0.04) and inclination angle (α: 0°– 90°). It was found that the N um and the total entropy generation augment by increasing Re, ϕ: and γ. conversely, an opposite effect was obtained by increasing Ha and α. The optimum magnetic field and cavity inclination angles to maximum heat transfer are γ = 90° and α = 0.

Heat Transfer in an Inclined Rectangular Cavity Filled with Hybrid Nanofluid Attached to a Vertical Heated Wall Integrated with PCM: An Experimental Study

In this paper, natural convective heat transfer in a rectangular cavity filled with (50% CuO-50% Al2O3)/water hybrid nanofluids connected to a wall containing a phase change material (PCM) has been experimentally investigated. The vertical walls were heated at varying temperatures while the horizontal walls were kept adiabatic. The considered parameters were the concentration of hybrid nanomaterial (Φ = 0.03, 0.05), the cavity inclination angle (θ = 0°, 30°, 45°), and the temperature difference between the hot and cold sides (∆T = 10, 15, 20 °C). The results have been validated and agree well with previously published papers. Furthermore, the main results stated that when the nanomaterial concentration increased, the heat transfer rate by free convection also increased. By increasing the natural convection flows via high temperature, symmetrical vortexes may appear near the heated wall. It also found that the PCM can potentially reduce the temperature of the hot side by up to 22% due to its high absorbability and heat storage. Furthermore, the inclusion of hybrid nanofluids in addition to the PCM enhanced its efficiency in heat storage and, therefore, its capacity to cool the hot side. Moreover, the influence of the inclination cavity enhanced the heat transfer, where θ = 30° was the optimal angle in terms of thermal conductivity.

Study of the coupling effect of elliptical cavities and cracks on tunnel stability under dynamic loads

This study to explore the coupling effect of elliptical cavities and cracks on the dynamic stability and failure modes of tunnels. A series of dynamic numerical simulations and model tests were conducted by using AUTODYN code and a modified drop hammer impact test device. A cracked tunnel model with an elliptical cavity was proposed in this study. The crack coalescence behaviour, crack initiation time and stress field around the elliptical cavity and the crack tips were calculated by using numerical simulation, and the dynamic initiation fracture toughness (DIFT) was also determined according to experimental and numerical results. According to these results, we conclude that the long and short axes of the elliptical cavity have a great influence on the crack coalescence behaviour and the stress field, and the long axis of the elliptical cavity has a greater influence than the short axis. When the inclination angle θ of the elliptical cavity is 90°, the stability of the crack is lowest, and when the inclination angle θ of the elliptical cavity is 45°, the effect of the elliptical cavity on the crack initiation behaviour is largest. DIFT was calculated and indicated that when the inclination angle of the elliptical cavity shows its smallest value, 90°, the cracked tunnel stability is lowest.

Influence of cavity inclination on mixed convection in a double-sided lid-driven cavity with a centrally inserted hot porous block

A numerical investigation is made to understand the influence of seven distinct cavity inclination angles (α = 0°, 15°, 30°, 45°, 60°, 75° and 90°) on the fluid flow behaviour during mixed convection in a double-sided lid-driven cavity for varied Richardson numbers (0.01≤Ri≤100). A hot porous square block with a blockage ratio of 0.25 is inserted at the cavity centre. We employ the multiple-relaxation-time lattice Boltzmann technique, which incorporates the Brinkman-Forchheimer-extended Darcy model for simulating flow through the permeable structure at different Darcy numbers (10−2≤Da≤ 10−6). The validation of the present developed code provides reasonable agreement with the previously reported findings acquired using conventional CFD approaches. It is noticed from the results that the cavity inclination angles provide a substantial impact on the generation of entropy and the rate of heat transfer. Furthermore, the findings reveal that the values of Ri and Da influence the optimal energy-efficient condition for a flow configuration.

Flow instabilities and heat transfer in a differentially heated cavity placed at varying inclination angles: Non-intrusive measurements

We report the non-intrusive investigation of the dependence of buoyancy-driven flow instabilities on the orientation angle of a differentially heated cavity of aspect ratio three. The cavity orientation angles considered are 60° and 30°. While moving from 60° to 30°, the cavity is inclined toward its stable configuration, wherein convection reduces. Flow instabilities have been captured through the spectral analysis of the transient history of temperature distribution recorded in a completely non-intrusive manner using a Mach–Zehnder interferometer. By virtue of the fact that in such configurations, corners of the cavity are the most active regions with regard to the interaction of buoyancy-driven fluid with the cavity walls, and the flow behavior is centrosymmetric (diagonal symmetry), the flow field in the top two corners of the cavity has been mapped. The spatio-temporally resolved interferometric measurements identified two distinct frequencies for cavity inclination angle (θ) of 60°. These two frequencies correspond to two different flow instabilities, namely, the Tollmien–Schlichting (TS) and gravity wave-induced instabilities. As the cavity is further inclined toward 30°, the instability in the boundary layer, i.e., the TS instability, ceases to exist, and only the gravity wave-induced instability is observed. The dependence of flow instabilities on cavity orientation angle is explained on the basis of interferometry-based measurements made in the form of interferograms and the corresponding whole field maps of temperature contours. The convective flow field in the differentially heated cavity has also been qualitatively captured using smoke visualization to provide direct support to interferometric measurements.

Effect of surface waviness on MHD thermo-gravitational convection of Cu−Al2O3−water hybrid nanofluid in a porous oblique enclosure

This study investigates thermo-fluid phenomena of magnetohydrodynamic (MHD) free convection utilizing Cu-Al2O3/water hybrid nanofluid in a porous oblique enclosure consisting of a heated wavy vertical wall. The coupled transport equations are solved numerically by implementing the dimensionless governing equations and using an indigenous FORTRAN-based CFD code and the finite volume approach (FVM). The flow physics along with heat transfer characteristics are explored thoroughly by varying the number of peaks (n) of the wavy wall at different Darcy-Rayleigh numbers (Ram), Darcy numbers (Da), Hartmann numbers (Ha), and nanoparticle volumetric fractions (ϕ) for different inclinations (γ) of the enclosure. The study findings indicate that the wavy curved wall does not always guarantee heat transfer boosting even with the increase in the effective heating surface area. An increase in active length of the wavy heated wall by the undulations (which is ∼320% with 8 undulations) leads to the heat transfer enhancement of ∼20% compared to a no-undulated cavity. The average heat transfer rate is maximum when n = 4, beyond which heat transfer decreases. Depending upon the setting of the value of Ram, Da, Ha, ϕ and γ, the flow-structure and associated heat transfer characteristics are severely altered. Cavity inclination angle has a significant role in controlling the overall thermal performance.

Optimization of Inclination Angle of Cavity and Characteristics of Attached Fins on the Absorber for Performance Enhancement of Solar Collectors

This research investigation was undertaken in ANDUAT, Kumarganj, Ayodhya, Uttar Pradesh, India to study the numerical optimization of natural convection heat suppression in a solar flat plate collector with straight fins. Optimal characteristics of an array of thin fins attached on the absorber plat were obtained by Particle Swarm Optimization algorithm (PSOA). Free convection considered dominant in the cavity. Governing equations contained continuity; momentum and energy are discretized by finite volume method. The medium is considered incompressible, whose free convection is dominant and Boussinesq approximation is applied. A simplified model of real systems is applied with free convection. Free convection problem is solved by SIMPLER algorithm. Two confined cavities with aspect ratios 30 and 60 are considered as flat plate solar collectors. The results indicate that significant reduction on the free convection heat loss can be obtained from solar flat plate collector by using plate fins, and an optimal plate fins configuration exit for minimal natural convection heat loss for a given range of Rayleigh number. Reduction of up to a maximum of 25% at 0 inclination angle was observed in aspect ratio 30. Results showed PSOA is able to obtain characteristics of attached adiabatic fins on the absorber plate also it can obtain optimal inclination angle of cavity to decrease heat losses from solar collectors. The results obtained provide a novel approach for improving design of flat plate solar collectors for optimal performance.

Effects of fins on magnetohydrodynamic conjugate natural convection in a nanofluid-saturated porous inclined enclosure

The magnetohydrodynamic conjugate heat transfer characteristics of a ferrofluid-filled porous inclined enclosure heated differentially have been investigated numerically in the present work. Two-conducting fins are attached to the hot wall of the cavity and the horizontal walls are insulated. The ranges of dimensionless flow controlling parameters are taken as: modified Rayleigh number (10 ≤ Ra⁎ ≤ 104), length of the fins (a = 0.3, 0.5, 0.7), gap between the two fins (b = 0.3, 0.5, 0.7), and Darcy number (10−5 ≤ Da ≤ 10−2), volume fractions of nanoparticles (0 ≤ ϕ ≤ 0.06), Hartmann number (0 ≤ Ha ≤ 50), and the cavity inclination angles (0 ≤ γ ≤ 90o). The finite element method has been used to solve the governing equations and the present code have been validated with previously published work. The results show that the average Nusselt number increases by increasing the modified Rayleigh number, Darcy number, fins length while it decreases by increasing the Hartmann number. For any range of modified Rayleigh numbers, the highest fin length and the widest gap between the fins can be a superior heating strategy. At a fixed fin length, the lower gap between the fins is of a better choice to boost heat transfer when the cavity inclination angle increases up to 30o.

Effect of partial magnetic field on thermo gravitational convection in an inclined cavity

The study presented gives a succinct overview of the effect of partially applied magnetic field on natural convective heat transfer in a differentially heated inclined cavity. The left and right sidewalls are differentially heated such that their temperatures are maintained (at T h and T c respectively), while the top and bottom walls have been assumed to be adiabatic, such that heat transfer through those walls can be neglected. The results are supposed to elucidate the effect of changing Rayleigh number (Ra), Hartmann number (Ha), and cavity inclination angle (f ) on the thermo-fluid phenomena. The analysis is carried out numerically utilizing finite volume based computing code. The results have been demonstrated in the form of streamlines, isotherms, and average Nusselt number. From the analysis, it is found that the flow structure and associated heat transfer characteristics are severely influenced by the studied range of governing parameters.

Influence of dome shape on flow structure, natural convection and entropy generation in enclosures at different inclinations: A comparative study

Flow structure is an essential aspect for the intensity of natural convective heat transfer in enclosures. Improvements in the enclosure geometry affecting the flow structure can increase the natural convective heat transfer performance. As the dome shaped walls can change the flow direction in a way to improve the flow circulations and natural convection, the present work numerically investigates laminar flow and natural convective heat transfer of air in dome shaped enclosures with three different dome inclinations. The dome shape can be designed for such enclosures by either filleting the corners of a rectangular cavity or replacing one of the adiabatic walls of a square cavity with a dome shaped wall. Therefore, the impact of dome shape utilization is analyzed from these two perspectives by separately considering the rectangular and square enclosures as reference cases. To broaden the investigation for various circumstances, three different Rayleigh numbers and four different cavity inclination angles are considered. Furthermore, the non-dimensional entropy generation rates are computed for each enclosure to evaluate their performance in terms of second law of thermodynamics. The results show that the dome shape wall significantly changes the flow structure by providing a smoother circulation, which facilitates more intensified convection currents by directing the hot fluid to the colder region of the enclosure, hence, establishing a more effective natural convective heat transfer. The computed results reveal that the mean Nusselt number can be augmented up to 22.5 and 25.0% by the utilization of dome shaped enclosure compared to the equivalent rectangular and square enclosures, respectively. The impact of the dome is dependent on the cavity inclination and generally decreases as Ra increases. Besides, the dome shaped enclosure codified by D45 gives the lowest entropy generation value.

Thermosolutal natural convection across an inclined square enclosure partially filled with a porous medium

The present study is a numerical inspection of the natural convection with double diffusion in a tilted square cavity filled with a vertical bi-layered composed porous and an adjacent fluid. Isotropic and homogeneous porous layer is considered in this case study. The porous layer is saturated by an aqueous solution with a Prandtl number Pr = 7. The horizontal walls are considered impermeable and adiabatic, while uniform concentrations and temperatures are set on the vertical walls. The Thomas algorithm is employed to find a solution for the system of the governing equations. The divergence of the non-linear system is avoided by introducing under–relaxation factors. The effects of the various non-dimensional governing parameters namely the thickness of porous layer, Rayleigh number, buoyancy ratio, Lewis number, cavity inclination angle, and the thermal conductivity ratio on the thermo-solutal natural convection and the rate of mass and thermal exchange are highlighted and discussed. The predicted findings are given in terms of flow patterns, thermal fields, and iso-concentration lines. The variation of the velocity field, stream function, Sherwood number, and Nusselt number is also inspected. The numerical results show complex flow structure modifying the local transfer (Nusselt and Sherwood numbers).

Cavity receivers in solar dish collectors: A geometric overview

Many studies, as numerical and experimental, regarding the applications of solar dish concentrators have been performed. Most researchers focused on the maximum thermal efficiency, the minimum heat loss, and their relations to the solar receiver geometries. This paper presents and discusses the previous studies investigating different cavity receiver geometries and their optimization methods with parabolic dish collectors. More specifically, cylindrical, hemispherical, conical, and flat sides cavity receivers are investigated in this manuscript. For an inlet operating temperature of 200 °C, the conical cavity shape has shown a thermal efficiency of around 70%, exergy efficiency of 30%, and optical efficiency of around 87%. The working fluid temperature is often around 650 °C–750 °C in the solar dish collectors. Due to high working temperature and cavity shape, heat losses such as radiation, conduction, and convection losses are highlighted that could provide adverse effects upon the system thermal efficiency. Besides, the diameter aspect ratio, the cavity inclination angle, type of tube, and the tube shape can be impressive on the cavity heat losses value. Therefore, the optimized geometry of the cavity receiver is a vital subject. Based on the analyzed issues, some suggestions and concluding remarks are presented.