High Heat Transfer Rates Research Articles

Thermodynamic analysis of EMHD ternary nanofluid flow with shape factor effects over a shrinking sheet: A non-Fourier heat flux model

The investigation of the flow characteristics of ternary hybrid nanofluids through a contracting sheet has considerable importance due to its potential for achieving exceptionally high rates of heat transfer. The ternary hybrid nanofluid then absorbs heat from the surface and carries it away. The objective of this study is to analyze the influence of couple stress and activation energy parameters on the flow of a ternary hybrid nanofluid ( H 2 O + MWCNT + ZnO + Al 2 O 3 ) through a contracting sheet with electric forces and convective boundary conditions. The heat flux model created by Cattaneo and Christov is utilized to examine the mechanism of heat transmission. The equations necessary to depict the problem have been transformed into a system, which has subsequently been resolved using the bvp4c solver (MATLAB built-in function). It is found that there is a rise in the Bejan number with the increase in the couple stress parameter. An increase in the volume percentage of multi-walled carbon nanotubes ( ϕ MW ) is observed to result in an augmentation of entropy generation . It has been observed that there is a fall in the friction factor when the couple stress parameter rises and at 0 ≤ Ed ≤ 0.6 , (electric field parameter), the friction factor is seen to rise at a rate of 0.638797 (Platelet) and (0.638784). A positive correlation is observed between the thermal relaxation parameter ( ϒ ) and fluid temperature, indicating that a rise in the former leads to an increase in the latter. It is discovered that, when 0 ≤ ϒ ≤ 0.3 , the Nusselt number rises by 0.022587 (Platelet) and 0.022275 (Cylinder). There is a negative correlation between the upsurge in the activation energy parameter ( Eg ) and the corresponding rise in the Sherwood number. At 0 ≤ Eg ≤ 3 , the Sherwood number is seen to decline at a rate of 0.0321 (Platelet) and 0.03208 (Cylinder).

Analysis of irreversibility on nanofluid flow through porous medium considering shape, dispersion and melting effects

This study is conducted to explore the impact of thermal dispersion and melting on the natural convective nanofluid (nickel zinc ferrite + SAE 20W-40 motor oil) flow over a stretching sheet in a Darcy porous medium. An irreversibility analysis has also been performed using the second law of thermodynamics. The fundamental nonlinear partial differential equations (PDEs) are converted into a system of dimensionless nonlinear ordinary differential equations (ODEs) through Lie group similarity transformations and then solved by employing the spectral local linearization method implemented in MATLAB software. It is noteworthy to highlight that the validation results indicate a strong concurrence with existing findings in previously published literature. After simulation, it is specified that the thermal dispersion disrupts the entropy (by 63.7%) and enhances the surface friction. Likewise, the heat transfer rate improves by 1.5% with the melting effect and 58.7% with the Darcy number. The results indicate that the brick-shaped particles exhibit a higher rate of heat transfer and lower entropy production. Further, this work has many uses such as, core, microwave, and biomedical applications like tumor treatments, bone plate surgeries, EMI (electromagnetic interfaces), electronics cooling, and aerodynamic extrusion processes, in the design of passive ventilation systems.

Magnetic field effect on mixed convection flow inside an oval-shaped annulus enclosure filled by a non-Newtonian nanofluid

The phenomenon of flow around a static or rotating circular cylinder has significant applications in various engineering fields, such as building, bridge, and structure engineering. It can be used to control flow-induced vibration, blowing or suction, moving surfaces, acoustic thriller, and synthetic jet. Additionally, there is a need to enhance heat transfer rates in many life and industrial applications, including cavity shape enhancement, heating or cooling spread inside a cavity, heat dissipation in electronic devices, thermal mixing in storage units, solar collectors, desalination, and journal bearing lubrication. This study explores the effect of a horizontal magnetic field and a rotating inner circular cylinder on mixed convection within a two-dimensional oval-shaped enclosure filled with a non-Newtonian nanofluid. The Galerkin Finite Element Method (GFEM) is utilized for analysis, with the enclosure undergoing differential heating and cooling on the inner cylinder wall and the enclosure wall, respectively. The nanofluid consists of water infused with copper nanoparticles. The study explores various simulation parameters, including the Richardson number (Ri), Hartmann number (Ha), the inclination angle of the enclosure (β), power-law index (n), circle center eccentricity (e), and nanoparticles volume fraction (φ). It has been observed that as the Ha and n index increase for different Ri values, a wavy trend in local Nusselt number (Nu) profiles along the heat source surface is observed. Additionally, the heat transfer rate decreases with increasing Ri for various combinations of Ha and n index. Under specific conditions, such as Ri = 0.001, Ha = 60, e = 0, φ = 0.09, and β = 90, the results show that, compared to a Newtonian fluid (n = 1), the heat transfer rate exhibits percentage gains of approximately 6.31% for a pseudo-plastic fluid (n = 0.6) and 8.47% for a Dilatant fluid (n = 1.4). The convective heat transfer was significantly enhanced when the eccentricity of the cylinder was positioned in the lower or upper regions of the oval-shaped enclosure, particularly at e = - 0.3. The highest heat transfer rates were observed at β = 60 and 240.

Rotary thermal desorption technology for treatment of oil-based drilling cuttings in shale gas industry

Oil-based drilling cuttings are hazardous wastes in shale gas exploitation and need careful treatments to reduce environmental pollution and waste of resources. One of most widely employed waste-treatment technologies is the thermal desorption due to its high oil recovery efficiency. However, it usually suffers low heat exchange efficiency, thus leveraging operation costs and equipment instability. Toward the end of alleviating limitation, this study rationally designs the structure of the heating component under the guidance of the flat wall heat conduction theory, and uses numerical simulation to analyze the heat transfer of the structure. A rotary thermal desorption technology was thus developed and evaluated. The simulation results showed that given a short time of 800 s the temperature difference between device and cuttings became less than 5 K, indicating good heat exchange efficiency. Large inlet radius of device and high inlet velocity of heat transfer oil were critical parameters to maintain high heat transfer rate. Through industrial experiments verification, the 0.14–0.2 % oil content of treated cuttings qualified the environmental standards. The components of the recovered oil were recyclable C9-C23 alkanes, and the dichromate oxidizability of recovered water was less than 500 mg/L limit. Comparing with other technologies, the scores suggested that this technology was a promising candidate for treating oil-based drilling cuttings.

Comparing the partial cooling and recompression cycles for a 50 MWe sCO2 CSP plant using detailed recuperator models

Supercritical carbon dioxide (sCO2) power cycles are attractive for renewable energy technologies as they exhibit high thermal efficiencies, compact components, and reduced cycle complexity and levelized cost of energy (LCOE) relative to traditional steam power cycles. Consequently, numerous studies have investigated different layouts and operating parameters in search of an optimal cycle configuration. Two cycle layouts provide promising results, namely the partial cooling with reheating (PCRH) cycle, and the recompression with intercooling and reheating (RCICRH) cycle. Both cycles utilise recuperators with high heat transfer rates and literature suggests that the cost for the recuperators may account for a significant portion of the total plant capital expenditure. When modelling the recuperator, most cycle comparative studies employ simplified recuperator models where heat exchanger effectiveness or conductance is utilised to approximate heat transfer. These models do not consider the effect of recuperator size and geometry on heat transfer and pressure drop in detail. In this work, for a concentrated solar power (CSP) application, the performance and component size requirements of the cycles are evaluated parametrically for different cycle mass flow split ratios, pressure ratios, and ratio of pressure ratios across the compressors using detailed discretised one-dimensional (1D) recuperator models. Furthermore, the geometry of these models are optimised (by volume) for straight and zigzag channel printed circuit heat exchangers (PCHEs), widely accepted as the most suitable for this application. Finally, a high-level cost comparison is conducted. The results show that if appropriate pressure drop assumptions are made, a simplified model approach yields valid cycle level results when compared with the results obtained using detailed models which consider practical recuperator geometry. However, the pressures and temperatures within the recuperator may not be predicted to a sufficient level of accuracy. In addition to providing clarity regarding the interplay between key cycle process parameters and cycle performance, straight channel PCHEs provide better thermofluid performance than zigzag channel PCHEs. Furthermore, the RCICRH cycle requires larger turbomachinery and a marginally higher capital outlay for the power cycle, but offers superior thermal efficiencies and requires smaller heat exchangers. For sCO2-CSP applications employing dry cooling, this suggests that the RCICRH cycle requires a smaller solar field and cooling system, and may therefore offer increased revenue in adverse weather conditions where direct normal irradiance (DNI) is low and/or ambient temperatures are high. However, the PCRH cycle requires a smaller solar receiver system, a smaller thermal energy storage (TES) system, and smaller turbomachinery, the cost savings of which may outweigh the benefits of the RCICRH cycle.

Darcy-Forchheimer hybrid nanofluid flow in an asymmetric channel with an exponential heat source, variable thermal conductivity, and activation energy

Background Heat transfer in nanofluid flows plays a vital role in many industrial, medical, and manufacturing industries. Hybrid nanofluid (HNF) has a significant potential to enhance the thermal characteristics of several fluids employed in a wide range of thermal systems and thus uses reduced energy and provides increased sustainability. Also, the thermal conductivity of nanofluid depends on the mobility of nanoparticles and that can be improved by activation energy (AE) besides the latent micro convection. Literature reveals that the research works available on the enhanced heat transfer due to the appropriate combination of nanoparticles along with AE in an asymmetric channel is very limited. Aim This study aims to explore the impact of the AE and the variable thermal conductivity (VTC) on the HNF flow in an asymmetric channel with permeable walls. The effects of radiation, thermal conductivity, and exponential heat sources are also considered. Method An effective similarity transformation is used to convert the governing equations into a system of nonlinear ordinary differential equations (ODEs). The nonlinear ODEs with appropriate boundary conditions are solved numerically by a shooting method. Results The consequences of the physical parameters on the axial velocity, temperature, and species concentration are explained and are presented through graphs. In comparison to viscous fluid, the dual nanofluids have a 5.8% higher heat transfer rate with VTC parameter at the lower wall. However, the species concentration rate of HNF is 20.0% higher than that of viscous fluid with AE parameter.

Effects of nonlinear thermal radiation on the efficiency of building integrated photovoltaic systems with nanofluid cooling.

The nonlinear effects of thermal radiation on the free convection flow of certain nanofluids along a heated wall are studied numerically using an original finite-difference method. Nanofluids are used to improve the performance of flat and curved integrated photovoltaic modules. The partial differential equations governing the flow are difficult to solve due to the strong non-linearity of the radiative term. In contrast to previous studies, the problem is solved directly without linearization by Rosseland's nonlinear approximation. The proposed numerical method is validated with results from the literature. The effects of nonlinearity and various physical parameters such as time, volume fraction and radiation parameter on the velocity, temperature, Nusselt number and skin friction coefficient of the CuO-water nanofluid are analyzed and presented graphically. A comparative study between the solutions given by the linear and non-linear problems reveals that Rosseland's linear approximation is no longer valid when the effect of thermal radiation is significant. On the other hand, the non-linear model better reflects the physical phenomena involved in the cooling process. Finally, a comparison of the performance of five nanofluids (CuO, Ag, Al2O3, Cu and TiO2 in water) shows that the Cu-water nanofluid performs best, with a high heat transfer rate and low shear stresses.

NUMERICAL INVESTIGATION OF HEAT TRANSFER AND TURBULENT FLUID FLOW FOR TRANSVERSE VORTEX GENERATORS WITH NANOPARTICLES

This paper proposes a simple design and easy-to-install vortex generator (VG) for heat exchangers to enhance heat transfer rates. The aim is to maintain low pressure drops and high heat transfer rates. The effects of the VG's geometrical parameters on thermal performance and pressure drop are investigated in this paper for divergent and convergent schemes using commercial software Comsol Multiphysics version 6. The effects of Reynolds number, VG angle, and the quantity of VGs on the response (i.e., Nusselt number and pressure drop) are investigated based on variance analysis. The nanoparticle concentration varies from 1 to 6%. The results indicate that the quantity of VGs is the most significant factor affecting pressure drop. The critical factor for heat transfer enhancement of divergent and convergent VGs are the Reynolds number and the quantity of VGs, respectively. Finally, the optimal conditions are predicted by the response surface methodology (RSM). The optimal requirements for using VG type A are β = 0°, the quantity is two, and the Reynolds number should be 9160. Furthermore, the optimal conditions for VG type B are β = 0°, Reynolds number is 10,000, and the number of VGs is two. The VG proposed in this study has a simple structure that can be efficiently designed and installed on heat exchangers. It is more efficient and applicable than the designs suggested in the literature.

THERMAL ANALYSIS OF A PLATE HEAT EXCHANGER (PHE) FITTED WITH CARDING TOOL PATTERNS USING CFD MODELING

Inspired by the wool carding tools, a new plate heat exchanger (PHE) design was developed, tested, and analyzed numerically. The present research work used computational fluid dynamics (CFD) simulations to examine the impact of various parameters, such as the rib type (continuous and discrete), the arrangement type (rectangular, square, and triangular), and the geometrical parameters (transversal and longitudinal pitches) on the PHE hydraulic and thermal performances. A three-dimensional (3D) evaluation of turbulent flow over a plate fitted with carding tool patterns was conducted using the<i> k-ε </i>turbulence model within the Reynolds number range from 400 to 1800. The numerical results were compared to previous experimental research to validate the dependability of the technique, and a mesh independence analysis was performed to confirm the precision and the accuracy of the CFD method. The results show that CFD ANSYS software can effectively predict the pressure drop across the carding tools and provide valuable insights into the fluid flow behavior within the system in terms of calculating the thermal hydraulic performance parameter (THPP) and the thermal effectiveness <i>ε </i>. The ultimate goal of this research work was to identify the ideal arrangement with the highest heat transfer rate and the lowest pressure losses in terms of determining the best THPP. Compared to the conventional chevron-type PHE, the thermal performance of the novel PHE design was enhanced by 25.63% and 47% in terms of nondimensional parameters e and THPP, respectively.

The impact of particle size in fluidized bed on heat transfer behavior: A review

This review paper explores the significance of fluidized bed heat exchangers in various industrial applications. By delving into the operation of fluidized beds as multiphase flow systems, the aim is to enhance their capabilities and efficiency. Key parameters such as minimum fluidization velocity and local gas holdup are crucial for characterizing the hydrodynamic behavior of materials within fluidized beds. Fluidization, achieved by passing atmospheric air through particulate solids, imparts fluid-like properties to the bed. Fluidized beds serve as reactors where this phenomenon takes place, offering several advantages in industrial processes, including high rates of heat and mass transfer, low pressure drops, and uniform temperature distribution. In future work, a focus on understanding and optimizing the fluidization process will contribute to further advancements in the performance of fluidized bed heat exchangers.

FMECA and FTA analysis applied to the manufacturing process of pulsating heat pipes

Pulsating heat pipes (PHPs) offer significant advantages for the thermal control of electronic components due to their simple manufacturing and high heat transfer rates. The reliability of PHPs has traditionally been assessed through long-life testing, but detailed reliability analyses from an equipment perspective are limited. The study of PHP reliability is essential due to its application and operational conditions. For instance, in aerospace applications these devices operate under severe conditions, and maintenance or replacement is impossible during operation, making them critical components in system functionality. The reliability analysis of PHPs focuses on the manufacturing process, considering future operating conditions. Although preliminary PHP testing will be conducted on Earth, laboratory conditions are less stringent due to the difficulty of replicating launch acceleration and space conditions for long-term testing under microgravity. This study presents an FMECA (Failure Modes, Effects, and Criticality Analysis) of the pulsating heat pipe manufacturing process, breaking down the production of each component. The results indicate that the most critical point is concentrated in the assembly of these components, leading to a higher incidence of welding failures. It recommends further work to improve welding and analyze mechanical stresses within the heat pipe.

Biodiesel production using microreactor with integrated microheater through multi-objective optimization approach

Microreactor is one of the process intensification techniques which uses reaction dimensions below millimeter size and have greater yield within lesser reaction time and a high heat transfer rate due to their high surface to volume ratio. To develop energy efficient reactors, microheater is chosen as the heating source for microreactor which consume less power than the conventional heating elements. Using response surface methodology (RSM) and artificial neural network (ANN) the effects of the biodiesel process variables was analyzed: catalyst concentration (0.5–2.5 wt.%), reaction temperature (35–55 °C), flow rate (5–25 mL/min), oil to methanol molar ratio (1:6–1:18), and power supplied to the microheater (15–35 W). To observe more than set limit, Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) and VIKOR were used to evaluate the optimum conditions. Under the optimum conditions of 20 mL/min flow rate, 45 °C reaction temperature, 1.5 wt.% catalyst concentration, 1:9 oil to methanol molar ratio, and 20 W power supplied, the maximum biodiesel yield for microreactor with microheater is 91.1 %. Using ultrasonic mixing additionally for microreactor with microheater had maximum yield of 94.4 % under the optimum conditions.

Effect of different micelles on charging and discharging behavior of phase change material

Phase change material (PCM) offers high-density thermal energy storage, making it attractive for thermal management applications of electronic circuitry and thermal energy storage. However, PCM, like paraffin wax, ideal for such low-temperature applications, has very low thermal conductivity. The present study focused on the improvement of the thermal conductivity of paraffin wax using surfactants. The surfactants used as thermal conductivity enhancers (TCE) are cetyltrimethyl ammonium bromide (CTAB), Dioctyl sodium sulfosuccinate (known as AOT) and sodium dodecyl sulfate (SDS). The surfactant self-aggregation called a micelle, acts as conducting medium inside the paraffin wax, providing better thermal conductivity. The highest heat transfer rate with a peak temperature of 71 °C was observed in the case of AOT micelle paraffin wax. Adding SDS, CTAB, and AOT surfactants increased the highest temperatures by 4%, 8.4%, and 18.33% compared to pure PCM.

Entropy analysis and hydrothermal behavior of magnetohydrodynamic MOS2–Fe3O4/H2O hybrid nanofluid flow driven by buoyancy in a square enclosure with diverse fin heights

Fins, referred to as extended surfaces, play a crucial role in enhancing heat transfer across various industrial sectors. They achieve this by increasing the surface area available for convective heat transfer. These widespread applications span fields such as energy production, mechanical engineering, surface studies, heat recovery processes, and chemical engineering. The broad utility of fins has prompted researchers to enhance their precision through diverse methods, including numerical, experimental, and analytical approaches. Motivated by these practical applications, this study undertakes a theoretical investigation to analyze the effects of varying fin heights on the behavior of a hybrid hydromagnetic nanofluid within a porous square enclosure. The study explores three distinct cases. In the first case, fixed-height heat fins are attached to the upper and lower walls. In the second case, the fin attached to the upper wall remains static, while those on the lower wall are extended from 0.25L to 0.5L. Conversely, the third case involves extending the height of the upper fin from 0.25L to 0.5L. The in-house MATLAB code, coupled with a finite difference method, is employed to solve the governing equations, and its reliability is confirmed through comparison with prior publications. Thorough numerical simulations are conducted, encompassing control parameters such as thermal radiation, Rayleigh number, nanoparticle volume fraction, Hartmann number, heat generation/absorption, and Darcy number. The numerical results are visually presented through streamlines, isotherms, and average Nusselt number plots, elucidating the impact of these parameters across a range of scenarios. It is noticed that case 3 exposes a 96.06% higher heat transfer rate than case 2 with higher values of volume fraction and Rayleigh number. In all three cases, the Rayleigh number and Hartmann number cause a reduction in the entropy generation. For a higher Rayleigh number, employing a hybrid nanofluid containing a volume fraction of 5% causes a 110.41% reduction in heat transfer for the case involving bottom fin height compared to case 1. Similarly, extending the top fin leads to a heat transfer reduction of 100.41%.

A numerical investigation into thermo-fluid characteristics of pulsating jet impingement on a dimpled surface

A two-dimensional axisymmetric numerical model is employed to study the flow and heat transfer attributes of the pulsating air jet impingement on a dimpled surface. The results are compared with the steady jet impingement. The results are examined at a fixed Reynolds number of 5000, over a Strouhal number range of 0.1–0.5, and pulsation amplitude of 15% and 25% for three different nozzle-to-surface separations (z/d = 2, 6, and 10). The pulsation amplitude of 15% has a minor effect on heat transfer from the dimpled surface. However, at 25% pulsation amplitude, significant improvements in the heat transfer rates are obtained in many combinations of jet Strouhal number and jet surface spacing. The value of the optimum Strouhal number provides conditions for the maximum heat transfer rate, which varied with nozzle-to-surface separation distances. Combinations of higher separations and lower Strouhal numbers (and vice versa) produced optimum heat transfer among the cases considered in the present study. The maximum improvement (17.41%) in the average heat transfer over the steady jet was found at z/d = 10 for pulsation at St = 0.1, while at z/d = 6, St = 0.2 provides the highest heat transfer rate. It is urged that the vortices formed in pulse jet close to the natural frequency of vortex formation provide a conducive environment for the vortex growth and their existence, significantly affecting the jet entrainment, mixing, and jet spread, which eventually play the decisive factor in determining the overall heat transfer rates on the dimpled surface.

Convective Flow of Water-Ethylene Glycol (50:50) Based Nanofluid Over a Spinning Down-Pointing Vertical Cone in a Darcy Porous Medium

The present work analyzes the free convective boundary layer flow of nanofluids around a heated and spinning down pointing vertical cone with the effect of magnetic field placed in a porous medium. The solutions of the partial differential equations with slip boundary conditions, which describes the flow are attained by a numerical based technique called fourth order Runge-Kutta method with shooting techniques after converting into ordinary differential equations with suitable transformations. The impact of governing parameter on velocity profile, temperature distribution is represented graphically. The range of the variables are 0 < M < 4, 0.01 < Φ < 0.04, 0 < ɛ < 4, 0 < Da < 4, 0.1 < Γ1 < 1.5 and 0.1 < Γ2 < 1.5. Increasing the value of Da noticeably promotes the F′(y) and G(y) and diminishes the H(y). Regarding tangential velocity, Fe3O4 dominates Al2O3 for every values of Magnetic parameter, spin parameter, Darcy number, velocity and thermal slip parameter. Fe3O4 possess 0.87% of high heat transfer rate than Al2O3 with respect to nanoparticle volume fraction. In case of slip parameters (velocity and thermal) Al2O3 shows good heat transfer rate than Fe3O4 with 0.93% and 0.98% respectively. It is scrutinized that the current results are in excellent compatibility with the outcomes noted as in previous works.

A comparative assessment of mono and hybrid magneto nanofluid flow over a stretching cylinder in a permeable medium with generalized Fourier’s law

This study investigates the flow and heat transfer of mono and hybrid nanofluids owing to a stretching cylinder in a porous medium under the influence of a magnetic field and convective boundary condition. The hybrid nanofluid is made up of copper (Cu) and silver (Ag) nanoparticles dispersed in a water-ethylene glycol mixture at a mass ratio of 50:50. The binary mixture of water and ethylene glycol is intermixed with spherical-shaped nanoparticles (copper) to create a mono nanofluid. The study considers the effects of generalized Fourier’s law and heat generation/absorption. The novelty of the study lies in considering the comparison of hybrid and mono nanofluid flows heat transfer efficiency with assumed effects and convective condition at the boundary of the cylinder. A system of ordinary differential equations (ODEs) controlling the flow and heat transport are derived using similarity transformations and are solved numerically using the bvp4c program of MATLAB software. The work explores the ways in which different parameters, such as the shape of the nanoparticles and their volume percentage, affect the pertinent profiles and are depicted in the form of graphical illustrations and numerically tabulated values. The results demonstrate that, in comparison to mono nanofluids, hybrid nanofluids including spherical and blade nanoparticles have a higher heat transfer rate and reduced surface drag when the particle volume fraction is increased in a water-ethylene glycol combination. Furthermore, there is a 0.83% increase in the heat transfer rate for hybrid nanofluids in comparison to mono nanofluids. This is because compared to mono nanofluids, hybrid nanofluids have lower viscosity and better heat conductivity. The results obtained in this study are vetted by making a comparison with published works and an excellent agreement between the values is seen. The study may find use in solar thermal systems, electronic cooling, heat exchangers, and other areas.

A perspective on high‐temperature heat storage using liquid metal as heat transfer fluid

AbstractEnergy storage systems are essential to secure a reliable electricity and heat supply in an energy system with high shares of fluctuating renewable energy sources. Thermal energy storage systems offer the possibility to store energy in the form of heat relatively simply and at low cost. In concentrating solar power systems, for instance, molten salt‐based thermal storage systems already enable a 24/7 electricity generation. The use of liquid metals as heat transfer fluids in thermal energy storage systems enables high heat transfer rates and a large operating temperature range (100°C to >700°C, depending on the liquid metal). Hence, different heat storage solutions have been proposed in the literature, which are summarized in this perspective. Based on these, future technical advances are suggested such as reducing the liquid metal share in the heat storage, using waste material as storage medium or using liquid metal as heat transfer fluids not only in sensible, but in latent or thermochemical energy storage systems. The use of waste material in a packed bed configuration with 5% porosity, for example, can bring down the storage material costs to 2%–3% of the costs of a liquid metal‐only storage system. Furthermore, future application fields beyond concentrating solar power are proposed: supply of industrial process heat, waste heat integration and power‐to‐heat‐to‐power processes.

Optimization of the effect of sinusoidal phase shift heating on mixed convective in an enclosure: LBM approach

This paper investigates the influence of mixed convective heat transfer in a two-dimensional enclosure with sinusoidal heat applied on the vertical walls by the Lattice Boltzmann Approach. Governing equations are resolved by the Single-Relaxation-Time Bhatnagar-Gross-Krook model. A two-dimensional, nine-directional lattice arrangement is chosen to attain better numerical stability with good accuracy. The results are presented for four different fluids having Prandtl numbers equal to 0.015, 0.7, 1.38, and 7.0 respectively for mercury, gaseous ammonia, noble gases, and water. This analysis is performed for selected Reynolds numbers (100 ≤ Re ≤ 2000) and Richardson numbers (0.0 ≤ Ri ≤ 10.0). The above parameters are optimized using the Design of the Experiment to achieve maximum heat transfer rate. Taguchi method is used to conduct the required numbers of numerical studies and the dominant parameters are quantitatively found using Analysis of Variance (ANOVA). The present numerical results are compared with the existing literature and found good agreements. Results show that the right-side wall has always a higher heat transfer rate than the left-side wall. The factor levels combination for maximum heat transfer rate is found as Pr = 7.0, Re = 2000, and Ri = 10.

Design and numerical investigation of heat transfer characteristics in annular cooking bowl using food graded heat transfer fluid for NCCS

The design of non-centrifugal cane sugar (NCCS) preparation methods is paramount for jaggery production. A numerical analysis is performed on an Annular Cooking Bowl (ACB) in which food graded heat transfer fluid (FHTF) is used as heat transfer fluid. The effect of mass flow rates (10 lpm, 15lpm and 20 lpm) and inlet temperatures (403 K, 413 K, 423 K and 433 K) are studied. Transient numerical simulations are conducted to predict the temperature of inner ACB surface and sugar cane juice, heat transferred from FHTF to bowl for various inlet conditions. In addition to, thermal efficiency of ACB and its effectiveness is estimated. The present approach shows that it can replace the traditional sugar cane juice boiling methods with NCCS unit, which eliminates bagasse as fuel and reduces the carbon emissions. From the results, highest ACB’s thermal efficiency is seen with FHTF inlet temperature of 433 K at low mass flow rate. However, ACB’s thermal efficiency decreases drastically with increasing in mass flow rate due to uncontrolled heat losses to surroundings. It is concluded that ACB’s thermal efficiency is observed as 21 % when FHTF is suppled 10 lpm and 433 K. It is seen that at temperature of 433 K and mass flow rate, 15 lpm and 20 lpm ACB’s thermal efficiency is registered as 17 %, and 13 % respectively. Results reveal that higher heat transfer rates are seen with food graded heat transfer fluid, and relatively high convective losses are observed, which further reduces the bowl thermal efficiency.