Conventional Heat Transfer Fluids Research Articles

Recent progress in emerging hybrid nanomaterials towards the energy storage and heat transfer applications: A review

• The overview of the emerging nanomaterials is discussed. • Insight review on synthesis of emerging hybrid nanomaterials and their obtained structures. • Elaborated discussion on the recent progress on hybrid nanomaterials towards energy storage applications. • Detail discussion on current progress on hybrid nanomaterials in heat transfer fluids. • The challenges and new opportunities of hybrid nanomaterials are outlined for future research. Hybrid nanomaterials, which is a combination of two or more nanoparticles have been extensively evaluated as a promising candidate for energy storage and heat transfer applications, benefitting from the rise of synergistic effects between them. The unique form of this emerging combination of nanomaterials not only offers the improved features of the integrated nanoparticles but gives us the opportunity to tailor their physicochemical properties simply by modifying their composition and morphology. Scientific findings have demonstrated that the dispersion of hybrid nanomaterials in the base fluids, known as - hybrid nanofluids gives us the alternative way to replace mono nanofluid and the conventional heat transfer fluids as it provides a much better heat transfer enhancement that is beneficial for advanced heat transfer devices. On the other hand, when hybrid nanomaterials were utilized for energy storage devices, it exhibits an outstanding electrochemical performance, providing a significant contribution to the specific capacitance which permits a new strategy to design new electrodes for advanced energy storage devices. In this article review, we summarised the recent advancements made on the emerging hybrid nanomaterials, comprising of the general overview of the emerging nanomaterials, the synthesis routes for hybrid nanomaterials and their acquired hybrid structures along with their practical applications as electrodes in electrochemical energy storage and as heat transfer fluids for advanced heat transfer devices. Finally, we have also outlined some challenging issues associated with hybrid nanomaterials that requires further attention for future research.

Performance enhancement of photovoltaic panel by using microencapsulated phase change slurry in channel with staggered pins

Microencapsulated phase change material (MPCM) in the form of particles suspended in conventional cooling fluids such as water has shown enhanced heat transfer characteristics when compared to conventional single phase heat transfer fluids. This is attributed to the latent heat of fusion of the MPCM, which results in higher heat capacity of the heat transfer fluid. The thermal performance of MPCM slurry as a heat transfer fluid can be further improved when used in a channel consisting of staggered pins. Use of MPCM slurry in heat transfer channels can result in efficient cooling performance of photovoltaic (PV) systems, where significant thermal loads are prevalent due to high levels of irradiance or working in hot climate conditions. The present work investigates numerically the impact of using MPCM slurry at different mass fractions on the cooling performance of a heat transfer channel attached to a PV panel. The numerical simulations were performed using the ANSYS-FLUENT solver in combination with user-defined functions used to account for the thermophysical properties of MPCM slurry. It was observed that the Nusselt number of MPCM slurry was much higher than for water as single-phase fluid, especially at higher mass fractions at the same flow rate. Moreover, the PV panel temperature was found to be significantly reduced when phase change material in the MPCM slurry experienced melting. Moreover, using staggered circular pins in the channel resulted in a significant reduction of the PV panel temperature even under concentrated irradiance conditions. However, an increase in pumping power was noticeable at high mass fraction of MPCM slurry. Finally, a remarkable increase in the PV panel efficiency was achieved under normal and concentrated irradiance levels by using MPCM slurry in the cooling channel with and without staggered circular pins.

Boundary layer flow of micropolar nanofluid towards a permeable stretching sheet in the presence of porous medium with thermal radiation and viscous dissipation

Nanofluids are a novel new generation of fluids to improve the heat transfer capabilities of conventional heat transfer fluids. The thermo–physical properties of these fluids are very classic in comparison to common fluids. However, one of the most crucial drawbacks for classical nanofluid models is that they cannot describe a class of fluids that have certain microscopic characteristics arising from the micro–rotation and local structure of the fluid elements. In the present study, a numerical investigation has been carried out to discuss the laminar two–dimensional heat transfer flow of micropolar nanofluid through a porous medium over a stretching sheet with viscous dissipation and thermal radiation containing copper (Cu) nanoparticles and water is considered as a base fluid. The mathematical model has been formulated based on Tiwari–Das nanofluid model. The basic equations are transmitted into a set of nonlinear ordinary differential equations using similarity transformation, and then the numerical solution is evaluated by using the Runge–Kutta fourth–order procedure. The relevant results of velocity, angular velocity and temperature are shown visually and discussed quantitatively in detail. The micro–rotation parameter enhances the velocity and temperature of the fluid. The boundary parameter declines the velocity but shows the reverse effects for angular velocity. The suction parameter decreases the velocity, but the reverse impacts are seen for the injection parameter. The graphical outcomes also show that the momentum boundary layer thickness increases with the values of volume fraction and porosity. The temperature is growing due to enhancing the Eckert number and radiation parameter.

ANALISA NUMERIK PENINGKATAN TRANSFER KALOR ALIRAN TURBULEN FLUIDA NANO TiO₂/AIR PADA CIRCULAR MINICHANNEL

Conventional heat transfer fluids such as water, ethylene glycol and oil are limited by their poor thermal properties therefore it is needed the advanced heat transfer fluids that be able to improve their thermal performance. Nanofluids is a colloidal dispersion of nano-sized particles which are a breakthrough of thermal system. This numerical study using the multi-phase mixture model method investigated the convective heat transfer of TiO2/water nanofluids flowing through a circular mini channel with a 1.09 mm diameter and 306 mm length under turbulent flow regime. TiO2 nanoparticles with a diameter of 21 nm were dispersed into water with volume concentrations of 1.0, 2.0, 3.5, and 5.0 vol.%. The Reynolds number was varied from 4000-20,000 and a constant heat flux of 6500 W/m2. The results showed that the addition of nanoparticles and the variation of the Reynolds number increased the convective heat transfer coefficient of TiO2/water nanofluid by 5.18%, 7.4%, 12.4%, and 14.3%, respectively, with increasing in nanoparticles concentrations.

NiO nanowire-containing heat transfer nanofluids for CSP plants: Experiments and simulations to promote their application

Concentrating solar power (CSP) is considered a clean, renewable and sustainable energy with a significant potential to become an alternative to polluting fossil fuel-based technologies. Among CSP collectors, parabolic-trough collectors (PTC) are the most mature technology, representing nearly 90% of the currently installed collectors in CSP plants worldwide. In this technology, a heat transfer fluid (HTF) carries the thermal energy absorbed to a power block to produce electricity. Improving the thermal properties of the conventional HTF could lead to an improvement of the efficiency of CSP plants. In this sense, the use of nanofluids as the HTF in these plants can be a promising choice. Here, polycrystalline NiO nanowire-containing nanofluids have been prepared using the conventional HTF used in CSP plants as the base fluid; that is, the eutectic and azeotropic mixture of biphenyl (26.5%) and diphenyl oxide (73.5%). The stability, rheological and thermal properties have been characterized, and an analysis of the performance of the nanofluids prepared in standard and volumetric absorbers have been carried out. The overall CSP system performance can be increased up to 34.8% using the nanofluid in a surface collector or up to 34.3% using the nanofluid in a volumetric collector, which are better than the predicted 28.5% using the conventional HTF in a standard surface collector, thanks to the improvements in thermal properties, both specific heat and thermal conductivity. Finally, from molecular dynamics simulations we determined that the mean free path of thermal vibrations is longer for monocrystalline NiO nanowires. Thus, the development of strategies for obtaining this kind of nanostructures is of great interest because they can further improve the efficiency of these nanofluids.

Effect of surfactant on stability, thermal conductivity, and viscosity of aluminium oxide–methanol nanofluids for heat transfer applications

• synthesis of nanofluids by suspending various surfactants–Al 2 O 3 in pure methanol. • surfactant effect on stability and thermophysical properties of MBNF have studied. • more than 180 days stability was found for Al 2 O 3 –methanol–(CTAB) nanofluids. • significant enhancement of thermal conductivity was found. Nanofluids, suspension of nanoparticles, perform better in heat transfer applications due to their excellent thermal properties over conventional heat-transfer fluids. In this study, the stability of Aluminium Oxide (Al 2 O 3 ) methanol nanofluids and their thermophysical properties (thermal conductivity (TC), viscosity, and density) are experimentally investigated. Various surfactants and nanoparticles were suspended into methanol and sonicated to stabilise the suspension at different weight fractions (0.05–0.15 wt%) of the nanoparticles and surfactants. The stability was analysed for the same ratios of different wt.% of nanoparticles and surfactants as a function of time. All the experiments were carried out at a temperature of 298 °K. Nanofluids characterisation, zeta potential and physical observations revealed 0.10 wt% of Al 2 O 3 –methanol with cationic surfactant cetyltrimethylammonium bromide (CTAB) surfactant nanofluids were stable for more than 180 days (6 months). The experimental results found that the TC, viscosity, and density of Al 2 O 3 –methanol nanofluids were all an increasing function of wt.% of nanoparticles. The addition of surfactant into the Al 2 O 3 –methanol nanofluids slightly affects the TC, viscosity, and density. The maximum enhancement of TC with surfactant was found to be 13.7% which was 1.4% lower than without surfactant of Al 2 O 3 –methanol nanofluids. However, the Al 2 O 3 –methanol nanofluids were more stable and had enhanced thermal properties such as (TC, viscosity, and density) over the base fluid. Therefore, the results encourage using these nanofluids in heat transfer applications.

Comparative study of hybrid and nanofluid flows over an exponentially stretched curved surface with modified Fourier law and dust particles

Hybrid nanofluids are the prospective liquids that possess improved heat transfer enactment and thermophysical characteristics than conventional heat transfer fluids (water, oil, ethylene glycol) and single-particle nanoparticle immersed nanofluids. Here, a comparison of the hybrid nanofluid comprising copper, copper oxide nanosized particles with ethylene glycol (Cu-CuO/C2H6O2) as the customary liquid, with nanofluid copper-ethylene glycol (Cu/C2H6O2) is made. The flow of hybrid nanofluid is considered over an absorbent curved sheet which is stretched exponentially with dust particles with modified Fourier law. The modeled problem is assisted by the melting heat and second-order slip boundary conditions. The system of equations is coped numerically after applying the boundary layer theory to the system of governing equations. It is witnessed that dust phase and temperature are augmented for escalating estimations of the curvature parameter. It is also perceived that an escalation in the thermal relaxation and concentration parameter values results in a lowering temperature of the fluid. Furthermore, it is remarked that fluid velocity is enhanced for large disk curvature. The hybrid nanofluid in case of heat transfer comparison is far ahead of the nanofluid. The acquired outcomes are also endorsed by making a comparison with a published study. An outstanding agreement is attained.

A Comprehensive Review on Efficiency Enhancement of Solar Collectors Using Hybrid Nanofluids

Because of its potential to directly transform solar energy into heat and energy, without harmful environmental effects such as greenhouse gas emissions. Hybrid nanofluid is an efficient way to improve the thermal efficiency of solar systems using a possible heat transfer fluid with superior thermo-physical properties. The object of this paper is the study the latest developments in hybrid applications in the fields of solar energy systems in different solar collectors. Hybrid nanofluids are potential fluids with better thermo-physical properties and heat transfer efficiency than conventional heat transfer fluids (oil, water, ethylene glycol) with single nanoparticle nanofluids. The research found that a single nanofluid can be replaced by a hybrid nanofluid because it enhances heat transfer. This work presented the recent developments in hybrid nanofluid preparation methods, stability factors, thermal improvement methods, current applications, and some mathematical regression analysis which is directly related to the efficiency enhancement of solar collector. This literature revealed that hybrid nanofluids have a great opportunity to enhance the efficiency of solar collector due to their noble thermophysical properties in replace of conventional heat transfer working fluids. Finally, some important problems are addressed, which must be solved for future study.

A Review on Environmental and Economic Impact of 2D Nanomaterials‐Based Heat Transfer Fluids

2D nanomaterials‐based heat transfer fluids show excellent thermal properties due to their large specific surface area; hence, they find large‐scale applications in automobile industries and cooling processes. Therefore, it is very essential to study the environmental and economic aspects of these 2D nanomaterial‐based nanofluids. In this review, we have discussed the environmental impact of 2D nanomaterial‐based heat transfer nanofluids under various conditions. The environmental impact analysis of these materials has shown excellent capability in reducing the energy consumption for heat transfer operations. Moreover, the possibility of nanomaterials and base fluid recovery makes it a sustainable alternative. In addition, health risk assessment on humans, cytotoxicity, and life cycle analysis have also been explored. The price‐performance index has been successfully used to study the economic impact of 2D nanomaterial‐based heat transfer fluids. The overall economic impact of 2D nanomaterial‐based heat transfer nanofluids provides an optimistic perspective over conventional heat transfer fluids. Moreover, graphene production, market trend, and commercialization obstacles were also discussed.

Synthesis and thermophysical properties of functionalized graphene quantum dots for enhancing heat transfer of conventional fluid

For the past few years, graphene quantum dots have been utilized in versatile applications due to their ultra-small size, non-toxicity, high heat transfer capacity, water solubility, and biocompatibility. In the presented work, the graphene quantum dots (GQD) is utilized to improve the thermophysical properties of conventional heat transfer fluid. In this research, the polyalkyline glycol (PAG) has been used as a conventional heat transfer fluid. The graphene quantum dots have been synthesized using hydrothermal method and further functionalized for the proper dispersion in PAG. The novel nanofluid has been synthesized using functionalized graphene quantum (FGQD) with based fluid as PAG. The FGQD-PAG nanofluid is synthesized with very lower concentrations of 100 ppm, 200 ppm, and 500 ppm. In order to investigate heat transfer capacity, each concentration of nanofluid has been investigated for thermal conductivity and viscosity. The experimental result shows that 500 ppm of FGQD-PAG lubricant improves the thermal conductivity by 2 W/mk. Also, the optimal viscosity for the nanofluid is observed with 100 ppm of FGQD-PAG based nanofluid. Further, it is observed that the use of graphene quantum dots with PAG base fluid is stable and does not require any use of surfactant for the dispersion. From this research, the problem of aggregation, agglomeration and precipitation occurring due to vander waal force has been addressed and is resolved by covalent surface modification. Thus, it is concluded that the graphene quantum dots can be effectively utilized in industrial applications where energy conservation is required.

Influence of nanoparticle concentration on thermophysical properties and heat transfer performance of Al2O3 nanosuspension for refrigeration system

Different types of conventional heat transfer fluid have been synthesized according to different thermal application for energy conservation. The recent advancement in last two decades have been found by using nanofluid. The nanofluid are modified heat transfer fluid which uses the dispersed nanoparticles within the fluid to enhance the thermo physical properties. The experimentation in the paper shows the development of Al2O3 based nanofluid for the refrigeration application and the effect of nanoparticle concentration on different thermo physical properties of nanofluid. The base fluid in the experiment used are polyester oil (POE) and mineral oil (MO) which are commonly used as compressor lubrication oil in a refrigeration system. The synthesis of nanofluid was carried using two step method with different weight percentage concentration of 0.02%, 0.04%, 0.07% and 0.1%. The experiment followed for the determination of thermal conductivity, viscosity and specific heat. Use of Hamilton model for thermal conductivity and brinkman model for viscosity has utilized and compared against the experimental observation. The highest gain in the thermal conductivity by almost 57% noted in by using the 0.1 wt% of Al2O3 nanoparticles with mineral oil with slight increment in the viscosity. All the synthesized nanofluid were found to be stable as well as without agglomeration.

Experimentally validated pore-scale numerical analysis for high-temperature (>700°C), high-efficiency (>90%) volumetric solar receivers

• Proposes an innovative, high-temperature semi-transparent packed-bed solar receiver. • Hits SunShot target with one of the highest efficiencies, 92% for T outlet ≥ 700 °C. • Develops a 3-D pore-scale model which couples the optical and thermo-fluid analyses. • Minimises reflection loss via an optical baffle and the pore-scale arrangement. • Reports new experimental validation test data for heat transfer in packed bed. Concentrated solar thermal/power (CST/P) systems are evolving to operate at higher temperatures (i.e., above 700 °C) to drive advanced cycles and thermochemical processes. The development of high temperature, high efficiency solar receivers—as the highest temperature component in a CST/P system—represents a critical technical challenge in this evolution. Commercial solar receivers have been limited to operation below 600 °C due to (1) the historic trade-off between operation temperature and efficiency, and (2) the operating temperature limits of the liquid conventional heat transfer fluids. This paper investigates a gas-phase, packed-bed receiver, which is capable of addressing these limitations. To date, this novel design has shown promise for this application, but it has only been modelled on the macro-scale (i.e., a 1-D model). To obtain a more detailed understanding of this type of receiver, this paper presents the results of a novel 3-D pore-scale analysis of the proposed receiver to characterise the optical-thermo-fluid behaviour. To ensure the validity of this approach, experimental tests were conducted for a complex packed bed of spheres. The 3-D pore-scale analysis enables the development of innovative mechanisms to reduce radiosity losses. It also provides a deeper level of insight regarding the stagnation pressure loss caused by the inlet air-jet flows. The final results demonstrated that the pore-scale modifications of the design can yield an optimised packed-bed receiver with a maximum efficiency of ∼ 92 % (for a hot air outlet temperature well above 700 °C). This optimised receiver design represents a new pathway towards high-temperature solar receivers, which can operate at very high efficiency, to enable CST/P systems to utilise advanced power cycles.

Engineering molten MgCl2–KCl–NaCl salt for high-temperature thermal energy storage: Review on salt properties and corrosion control strategies

Conventional thermal energy storage (TES) media and heat transfer fluids (HTFs) currently used in commercial concentrated solar power (CSP) plants are nitrate-based molten salts with working temperature up to about 565 °C. Current interest in raising the working temperature in next-generation CSP for higher energy conversion efficiency leads to chloride-based molten salt technology (>700 °C). MgCl2–KCl–NaCl salt is selected to be such a TES/HTF material due to its excellent salt properties, abundance and low costs. In this review, survey and evaluation of its exact eutectic composition by evaluation of the phase diagram as well as most relevant salt properties for design, construction and operation of a test loop and projection of a real TES/HTF system are presented. They include minimum melting temperature, vapor pressure, heat capacity, density, thermal conductivity and dynamic viscosity. The working temperature range 420–800 °C is suggested for the TES/HTF system using this salt. Moreover, the recommended values of the heat capacity, density, thermal conductivity and dynamic viscosity in the suggested working temperature range are given. In addition, corrosion control strategies for this salt including corrosion monitoring and mitigation techniques are briefly reviewed, since controlling the salt corrosivity is one main concern of the engineering aspects using the molten chlorides at high temperatures. Overall, this review is expected to supply reliable values of the most relevant salt properties and recommend the most promising corrosion control strategies for further material studies, as well as modeling, simulation, detailed design and construction of molten MgCl2–KCl–NaCl salt TES/HTF systems.

Performance Analysis of Shell and Tube Type Heat Exchanger Using Aluminium Oxide (Al2O3) Nano-Particle

Abstract: Research in convective heat transfer using suspensions of nanometer sized solid particles in a base fluid started only over the past decade. Recent investigations on nanofluids, as such suspensions are often called, indicate that the suspended nanoparticles markedly change the transport properties and heat transfer characteristics of the suspension. The very first part of the research work summarizes about the various thermo physical properties of Al2O3 Nanofluid. In evacuated tube solar water heating system nanofluids are used as primary fluid and DM water as secondary fluid in Shell and Tube Heat Exchanger. The experimental analysis of Shell and Tube heat exchanger integrated with Evacuated tube solar collector have been carried out with two types of primary fluids. Research study of shell and tube heat exchanger is focused on heat transfer enhancement by usage of nano fluids. Conventional heat transfer fluids have inherently low thermal conductivity that greatly limits the heat exchange efficiency. The result of analysis shows that average relative variation in LMTD and overall heat transfer coefficient is 24.56% and 52.0% respectively. The payback period of system is reduced by 0.4 years due to saving is in replacement cost of Evacuated Tube Collector. Keywords: ETC; Nanofluid; LMTD; Thermal Conductivity; Overall heat transfer coefficient

A Review of Thermal Property Enhancements of Low-Temperature Nano-Enhanced Phase Change Materials.

Phase change materials (PCMs) are of increasing interest due to their ability to absorb and store large amounts of thermal energy, with minimal temperature variations. In the phase-change process, these large amounts of thermal energy can be stored with a minimal change in temperature during both the solid/liquid and liquid/vapor phase transitions. As a result, these PCMs are experiencing increased use in applications such as solar energy heating or storage, building insulation, electronic cooling, food storage, and waste heat recovery. Low temperature, nano-enhanced phase change materials (NEPCM) are of particular interest, due to the recent increase in applications related to the shipment of cellular based materials and vaccines, both of which require precise temperature control for sustained periods of time. Information such as PCM and nanoparticle type, the effective goals, and manipulation of PCM thermal properties are assembled from the literature, evaluated, and discussed in detail, to provide an overview of NEPCMs and provide guidance for additional study. Current studies of NEPCMs are limited in scope, with the primary focus of a majority of recent investigations directed at increasing the thermal conductivity and reducing the charging and discharging times. Only a limited number of investigations have examined the issues related to increasing the latent heat to improve the thermal capacity or enhancing the stability to prevent sedimentation of the nanoparticles. In addition, this review examines several other important thermophysical parameters, including the thermal conductivity, phase transition temperature, rheological affects, and the chemical stability of NEPCMs. This is accomplished largely through comparing of the thermophysical properties of the base PCMs and their nano-enhanced counter parts and then evaluating the relative effectiveness of the various types of NEPCMs. Although there are exceptions, for a majority of conventional heat transfer fluids the thermal conductivity of the base PCM generally increases, and the latent heat decreases as the mass fraction of the nanoparticles increases, whereas trends in phase change temperature are often dependent upon the properties of the individual components. A number of recommendations for further study are made, including a better understanding of the stability of NEPCMs such that sedimentation is limited and thus capable of withstanding long-term thermal cycles without significant degradation of thermal properties, along with the identification of those factors that have the greatest overall impact and which PCM combinations might result in the most significant increases in latent heat.

Heat Transfer Performance of Green Bioglycol-Based TiO2–SiO2 Nanofluids

Abstract The dispersion of nanoparticles in conventional heat transfer fluids has been proven to improve the performance of the fluids. However, the study on the heat transfer performance of hybrid nanofluids in the mixture of water and green bioglycol (BG) is limited in the literature. This paper presents the heat transfer performance and friction factor of green BG-based TiO2–SiO2 nanofluids. The TiO2 and SiO2 nanoparticles were dispersed in the mixture of 60:40 water: bioglycol (W/BG) and prepared at various concentrations up to 2.5% and composition ratios of 20:80. The experimental study on forced convection heat transfer was done under turbulent flow at constant heat flux for operating temperature of 70 °C. The heat transfer enhancement increased significantly with volume concentrations. The maximum heat transfer enhancements of the TiO2–SiO2 nanofluids at bulk temperature of 70 °C were observed to be up to 67.81% for 2.5% volume concentration. A slight friction factor escalation of the nanofluids was observed with 12% maximum increment. New correlations were developed to estimate the Nusselt number, and friction factor with average deviations of less than 4.3%. As a conclusion, the employment of the ecofriendly coolant nanofluids in improving thermal performance is proven and applicable for turbulent forced convection heat transfer applications.

Promising Nanoparticle-Based Heat Transfer Fluids-Environmental and Techno-Economic Analysis Compared to Conventional Fluids.

Providing optimal operating conditions is one of the major challenges for effective heating or cooling systems. Moreover, proper adjustment of the heat transfer fluid is also important from the viewpoint of the correct operation, maintenance, and cost efficiency of these systems. Therefore, in this paper, a detailed review of recent work on the subject of conventional and novel heat transfer fluid applications is presented. Particular attention is paid to the novel nanoparticle-based materials used as heat transfer fluids. In-depth comparison of environmental, technical, and economic characteristics is discussed. Thermophysical properties including thermal conductivity, specific heat, density, viscosity, and Prandtl number are compared. Furthermore, the possible benefits and limitations of various transfer fluids in the fields of application are taken into account.

Energy and Exergy (2E) Analysis of an Optimized Solar Field of Linear Fresnel Reflectors for a Conceptual Direct Steam Generation Power Plant

Direct steam generation is a promising alternative to conventional heat transfer fluids for solar thermal power plants using linear concentrators because water and steam do not have thermal and chemical stability problems. The novelty of this study, an energy and exergy (2E) analysis, was that it was performed on several configurations of a conceptual direct steam generation solar power plant with optimized Fresnel reflectors in Agua Prieta, Mexico coupled with a regenerative steam Rankine power cycle to quantify their efficiency and establish a reference for future implementation of this technology in concentrated solar power plants in Mexico. The thermal model was assumed to be a 1D steady-state flow and validated against results in the literature. It was then applied directly to a case study to determine the size of the solar field. The design point was the lowest solar irradiance day, and evaluating the solar multiple with the highest solar irradiance, taking care not to oversize the solar field, as suggested for solar plants without energy storage. Comparing the performance of the optimized Fresnel field against the FRESDEMO field of Plataforma Solar de Almería, a considerable decrease in the length of the loop has been demonstrated with a low reduction in thermal efficiency.

A Brief Review on Thermal Behaviour of PANI as Additive in Heat Transfer Fluid

Since a decade ago, investigation on nanofluids has grown significantly owing to its enhanced thermal properties compared to conventional heat transfer fluids. This engineered nanofluid has been widely used in the thermal engineering system to improve their energy consumption by improving the thermal efficiency of the system. The addition of nano-size particles as additives dispersed in the base fluids proved to significantly either improve or diminish the behaviour of the base fluids. The behaviour of the base fluid highly depends on the properties of the additives material, such as morphology, size, and volume fraction. Among the variety of nanoparticles studied, the conducting polymers have been subject of high interest due to its high environmental stability, good electrical conductivity, antimicrobial, anti-corrosion property and significantly cheap compared to other nanoparticles. As such, the main objective of the present review is to provide an overview of the work performed on thermal properties performance of conducting polymers based nanofluids.

Deep eutectic solvents-based CNT nanofluid – A potential alternative to conventional heat transfer fluids

We investigated Deep eutectic solvents (DES) in this study as a potential substitute for conventional heat transfer fluids. Methyl-triphenylphosphonium-bromide (MTPB) and choline chloride (ChCl) as the hydrogen bond acceptors (HBAs), and ethylene glycol (EG) and triethylene glycol (TEG) as the hydrogen bond donors (HBDs), were used to form DESs. The molar ratio of HBA to HBD was varied between 1:3 and 1:5 to produce a total of 11 DESs. In each of these DESs, carbon nanotube (CNT) was added and dispersed at a constant concentration of 0.04 wt% to form DES-CNT-nanofluids. There was no surfactant added for stabilisation. The nanofluids were homogenised using an ultrasonic bath at 37 kHz for 4 h at room temperature. The freezing points of DES-CNT-nanofluids were analysed using differential scanning calorimetry while their thermal degradations, vapour pressures and weight losses were analysed using a thermogravimetric analyser. DES-CNT-nanofluids were found to have lower freezing points (down to -117.90 °C) as compared to EG and TEG, valued at -13.40 and -4.0 °C, respectively. The addition of HBA, such as MTPB and ChCl to form DESs, was found to increase the thermal stability of EG and TEG from 105 to 128 °C to 130 and 220 °C, respectively. Furthermore, the vapour pressures of DESs derived from EG and TEG, independently, were lower than that of pure EG and TEG by about 73% and 45%, correspondingly. The dispersion of CNT in DESs enhanced their thermal stabilities, activation energies and their kinetic parameters. The degradation reaction order was also determined through Friedman and Avrami models, respectively. Thus, DES has been proven to be a potential substitute for conventional heat transfer fluids due to its improved properties.