Conventional Heat Transfer Fluids Research Articles

Exploration of Recent Developments of Hybrid Nanofluids

Over the past two decades, research on hybrid nanofluids has developed at a breakneck pace. Hybrid nanofluids are the potential fluids that outperform conventional nanofluids heat transfer fluids regarding thermophysical characteristics and thermal performance. Hybrid nanofluids are traditionally prepared by emulsifying each nanoparticle into the base fluid independently or diffusing both particles as a composite form into the base fluid. Despite the popularity and broad application of hybrid nanofluids in industrial/manufacturing processes, the review article classifying the mathematical models and categorization of the various hybrid nanofluids is limited in the scientific community. In light of this, this study examines recent and past research articles on deterministic hybrid nanofluid flow problems by exploiting different categorizations and metrics (method to solve the differential equation, the geometry of choice and thermophysical effects that have been employed as well as the nano-particle types). Researchers will be able to use the findings of this study for a future research proposal. Essentially, it is to fill in the gaps in the literature, particularly regarding the mathematical model for hybrid nanofluid flow problems and determining the geometry, thermophysical properties, and nanoparticle type.

Experimental Thermal Conductivity Studies of Agar-Based Aqueous Suspensions with Lignin Magnetic Nanocomposites

Nanoparticle additives increase the thermal conductivity of conventional heat transfer fluids at low concentrations, which leads to improved heat transfer fluids and processes. This study investigates lignin-coated magnetic nanocomposites (lignin@Fe3O4) as a novel bio-based magnetic nanoparticle additive to enhance the thermal conductivity of aqueous-based fluids. Kraft lignin was used to encapsulate the Fe3O4 nanoparticles to prevent agglomeration and oxidation of the magnetic nanoparticles. Lignin@Fe3O4 nanoparticles were prepared using a pH-driven co-precipitation method with a 3:1 lignin to magnetite ratio and characterized by X-ray diffraction, FT-IR, thermogravimetric analysis, and transmission electron microscopy. The magnetic properties were characterized using a vibrating sample magnetometer. Once fully characterized, lignin@Fe3O4 nanoparticles were dispersed in aqueous 0.1% w/v agar–water solutions at five different concentrations, from 0.001% w/v to 0.005% w/v. Thermal conductivity measurements were performed using the transient line heat source method at various temperatures. A maximum enhancement of 10% in thermal conductivity was achieved after adding 0.005% w/v lignin@Fe3O4 to the agar-based aqueous suspension at 45 °C. At room temperature (25 °C), the thermal conductivity of lignin@Fe3O4 and uncoated Fe3O4 agar-based suspensions was characterized at varying magnetic fields from 0 to 0.04 T, which were generated using a permanent magnet. For this analysis, the thermal conductivity of lignin magnetic nanosuspensions initially increased, showing a 5% maximum peak increase after applying a 0.02 T magnetic field, followed by a decreasing thermal conductivity at higher magnetic fields up to 0.04 T. This result is attributed to induced magnetic nanoparticle aggregation under external applied magnetic fields. Overall, this work demonstrates that lignin-coated Fe3O4 nanosuspension at low concentrations slightly increases the thermal conductivity of agar aqueous-based solutions, using a simple permanent magnet at room temperature or by adjusting temperature without any externally applied magnetic field.

Cu-Graphene water-based hybrid nanofluids: synthesis, stability, thermophysical characterization, and figure of merit analysis

Hybrid nanofluids are emerging as an alternative to conventional heat transfer fluids and nanofluids for improving the thermal efficiency of heat exchanging devices synergistically due to their outstanding thermophysical properties associated because of the dispersion of different types of nanoparticles as compared to mono nanofluids. This will help in optimizing fluid characteristics in different flow regimes for several applications. However, enhancing the thermal energy efficiency of heat exchangers is challenging owing to the deprived stability of hybrid nanofluids at greater volume concentrations. This work concentrated on the synthesizing, thermophysical depiction, and thermal performance estimation of stable water-based Cu-graphene hybrid nanofluids using very low volume concentrations of Cu and graphene hybrid nanostructures. Cu-graphene hybrid nanofluid was successfully synthesized by dispersing the synthesized Cu and graphene nanostructures (keeping the Cu concentration constant at 0.04 vol % and varying the graphene concentration from 0.01 to 0.1 vol %) in water. Hybrid nanofluids display excellent stability against aggregation for up to 7 weeks, as proven by higher zeta potential values. Thermophysical characteristics of the prepared hybrid nanofluids were effectively measured. The thermal conductivity of Cu-graphene hybrid nanofluids shows exceptional enrichment (~ 35%) at minimal concentrations of hybrid nanostructures. Viscosity of the water-based hybrid nanofluids shows remarkable enhancement as compared to water and represents the increasing trend in viscosity of the base fluid with respect to the increase in concentration of hybrid nanostructures. The thermal and rheological properties of hybrid nanofluids are effectively validated with existing theoretical models. In addition, the specific heat and pumping power of Cu-graphene hybrid nanofluids with respect to the volume concentration of hybrid nanostructures are calculated using the existing theoretical equations. A figure of merit (FOM) analysis was conducted for the synthesized hybrid nanofluids to gauge thermal efficiency and evaluate the applicability of these hybrid nanofluids under laminar and turbulent flow conditions.

Thermophysical Properties of SWCNT Nanofluid

AbstractThe current paper has the objective of exploring the thermophysical properties (TPPs) of single walled carbon nanotube (SWCNT) nanofluids (NFs) for heat transfer applications. The effect of dispersing the nanotubes in conventional heat transfer fluids (HTFs) has been investigated. Carbon nanotubes (CNTs) have exceptionally high thermal conductivities. Using the effective medium theory, density, specific heat, thermal conductivity, and viscosity has been evaluated as functions of volume fractions. The base fluids considered in this work are water, ethylene glycol, engine oil, and kerosene oil as these are the commonly used HTFs for industrial applications. Theoretical predictions from this study show an increase in density, thermal conductivity, and viscosity with volume fraction while there is a decrease in specific heat with volume fraction. The effect of the aspect ratio (AR) of CNTs on the thermal conductivity of NF is also investigated. For low volume fractions of SWCNT, the thermal conductivity has been found to increase with AR. Further, this study has been extended for a real‐world application of heat transfer using SWCNT. In this paper, a numerical investigation of heat transfer in a square enclosure with differentially heated vertical walls, filled with SWCNT‐water NF under natural convection is carried out. Due to low concentrations of SWCNT in water, single phase flow is assumed. Velocity and temperature distributions are obtained as solutions to the energy and Navier–Stoke's equations. A comparison of the temperature and velocity profile has been represented by simulating the system over a range of Rayleigh numbers.

The PPy-coated halloysite nanotubes nanofluids with high stability and broad-spectrum absorption for effective photothermal conversion

In this study, a novel approach for the synthesis of eco-friendly and cost-effective composite nanomaterials PPy@HNTs was introduced. The proposed synthesis method offers environmental friendliness, simplicity, and cost-effectiveness. The resulting PPy@HNTs nanofluids, obtained through dispersion in a specially formulated base solution, demonstrate excellent dispersion stability, desirable thermophysical properties, and remarkable photothermal conversion performance. At a concentration of 800 ppm, the PPy@HNTs nanofluids exhibited an impressive efficiency of 79.2 %, surpassing the performance of conventional heat transfer fluids (HTFs). This research presents a promising avenue for the utilization of low-cost nanofluids in the field of photothermal applications.

Сравнительный анализ теоретических моделей определения теплопроводности наножидкости

This article is devoted to the study of thermal conductivity of nanofluid. A nanofluid is a liquid in which nanometer-sized solid particles are dispersed. These particles are called nanoparticles. Nanofluids have new promising thermophysical properties compared to conventional heat transfer fluids. Thermal conductivity is one of the main thermophysical properties of a liquid. Thermal conductivity is of great importance in processes where heat transfer and fluid flow occur. The article presents well-known theoretical models for determining the thermal conductivity of nanofluid. A brief description of these models is given. Some experimental work on determining the thermal conductivity of various nanofluids is considered. A computational study of the effect of aluminum oxide (Al2O3) and silicon dioxide (SiO2) nanoparticles on the change in thermal conductivity of a nanofluid has been performed. A comparative analysis of known computational models and experimental data is carried out. The accuracy of the calculated models is determined by determining the thermal conductivity of the nanofluid.

Nanoakışkanların Isıl Sistemlerde Enerji Verimliliğine Etkisi: Deneysel Verilerin Isıl ve Hidrodinamik Performans Ölçütleri ile Değerlendirilmesi

The energy efficiency of heat exchangers has become crucial in industrial applications due to ever-increasing energy costs. Therefore, various methods have been developed to enhance heat transfer and accelerate the process (shortening the time), reduce the size of heat exchangers, and increase energy (fuel) efficiency. In recent years, researchers have recommended nanofluid suspensions in place of common heat transfer fluids to improve energy efficiency. Nanofluid suspensions are obtained by adding nanometer-sized particles (less than 100 nm in at least one dimension) to heat transfer fluids. This study focused on experimental data in the literature to investigate the effects of nanofluids on transferred thermal power and required pumping power in heat exchangers. The relationship between the transferred thermal power and the pumping power was defined by two different performance criteria (Performance Evaluation Criterion-PEC and Energy Efficiency Criterion-EEC), allowing us to scrutinize the effects of nanofluids in thermal systems on energy efficiency (energy consumption) from a more realistic perspective. The results show that nanofluids are more disadvantageous than conventional heat transfer fluids in terms of the energy budget in industrial applications. It is concluded that nanofluids can be used in special applications where those disadvantages are insignificant.

Optimization of gaseous working fluid and internally finned absorber tube for enhancing the thermal performance of parabolic trough solar collector

The current study examined the effect of various types of longitudinal finned absorber tubes with the gaseous working fluid on the performance of the parabolic trough collector. Conventional heat transfer fluids, such as water, thermal oils, molten salts, etc., have been limited when the parabolic trough collector works at very high temperatures. Gas may be used as heat transfer fluid when this collector may operate at very high temperatures. However, the heat transfer coefficient of gas is smaller than the conventional heat transfer fluid. Therefore, fins may be used to improve the parabolic trough collector's thermal performance when gas is used as heat transfer fluid. Hence, selecting the best suitable gas as heat transfer fluid and the optimum fin structure is essential to improve this collector's thermal performance. In this context, the current study has considered seven different gases, namely air, carbon dioxide, helium, nitrogen, oxygen, methane, and neon, and six longitudinal finned absorber tubes with different profiles, namely, rectangular, triangular, trapezoidal, T-shaped, and Y-shaped to select the best suitable heat transfer fluid and optimum fin structure. The best suitable gas and optimum fin profile have been chosen based on specific criteria (multi-objective optimization technique or the performance enhancement factor index). This problem has been simulated using commercial software ANSYS Fluent 2020 R2. The experimental and numerical data discovered in the literature are used to validate the results of the current investigation and found in good accuracy between them. The methane gas is found to be the most suitable heat transfer fluid based on both criteria. Then, the effect of mass flow rate and inlet temperature of methane gas on the average friction factor and Nusselt number have been investigated. It is found that the average friction factor decreases with the mass flow rate for the given inlet temperature, while the opposite trend has been observed for the average Nusselt number. For the first time, the T-shaped and Y-shaped finned absorber tube has been proposed in the present study and compared with earlier fin profiles utilized by the researcher. It is found that the increment in thermal efficiency for T-shaped and Y-shaped finned absorber tubes with methane gas is 8.9338 % and 10.1360 %, respectively. In contrast, the increment in exergy efficiency for T-shaped and Y-shaped finned absorber tubes is 8.942 % and 11.622 %, respectively. There is a significant improvement in the thermal and exergy efficiency of the proposed model compared to the models considered in the literature (air flow through absorber tube with the rectangular fin profile). Furthermore, the highest average Nusselt number of 480.4651 is found for the T-shaped finned absorber tube than other examined cases. However, the friction factor is also high for these fin profiles. As a result, the value of the performance enhancement factor for this fin profile is reduced, and the maximum value of the performance enhancement factor is obtained for rectangular fin profiles. Generally, increasing fin height and width increases thermal performance and pressure loss. Therefore, six different dimensions of rectangular fin have been studied and compared with smooth tubes. It is found that the optimum fin dimension of the rectangular fin is a height of 5 mm and a width of 4 mm. The present results can be utilized for designing an internally finned absorber tube to improve the collector's thermal performance with gas as heat transfer fluid.

Comparison of the use of different nanofluids for heat transfer from the outer surface of spiral tubes: Energy, exergy, and exergoeconomic (3E) analysis

Heat exchangers play a crucial role in industrial processes by facilitating the efficient transfer of thermal energy. The thermophysical properties of nanofluids, which consist of nanoparticles dispersed in conventional heat transfer fluids, are enhanced. Their remarkable thermal conductivity and convective heat transfer characteristics have the potential to significantly improve heat transfer processes. In the present investigation, a numerical study has been carried out to investigate the effect of different nanofluids on heat transfer from outer surface of a spiral coil based on the first and second laws of thermodynamics. The numerical solutions are checked against previous experimental and numerical research in the field. Nusselt number, Euler number, exergy efficiency, irreversibility, and equipment cost are studied with respect to concentration, mass flow ratio (Rm), and shell and tube inlet temperature for a variety of nanofluids, including Al2O3/H2O, CuO/H2O, Fe2O3/H2O, and TiO2/H2O. Compared to water, the exergy efficiency is lower while using nanofluids, as shown by the results, especially in higher nanofluid concentrations, and among the different nanofluids, Al2O3–H2O nanofluid was found to have the highest thermodynamics second law efficiency. The exergy destruction rate experiences linear growth by increasing the nanofluid concentration. A higher pressure drop based on the Euler number is expected for nanofluids. In addition, the consumption of nanofluids on the shell side results in a considerable reduction of the purchased equipment cost (PEC) value compared to water. As opposed to the tube-side input temperature, variations in the shell-side inlet temperature found to have a greater impact on the heat exchanger's exergetic performance.

Insight into the dynamics of active and passive controls over the measurement of thermal conductivity of nanofluids subject to magnetic field and thermal radiation through the stretching surface

In comparison to conventional heat transfer fluids, nanofluids tend to significantly enhance thermal efficiency. This extensive study is to enhance heat transformation while accounting for the magnetohydrodynamic (MHD) nanofluid flow with the impact of non-linear thermal radiation and an irregular heat source over the stretching sheet. The impact of Arrhenius activation energy on active and passive controls of nanoparticles, thermophoresis, and Brownian diffusion has elaborated. The system of partial differential equations is first represented mathematically and then converted into the system of ordinary differential equations by using similarity transformations. The influence of various parameters is displayed numerically through tables, graphical impact, and surface plots on heat and mass transfer, micro-rotation distribution, and the Nusselt number. It is noticed that the temperature profile is intensified with increasing values of the temperature ratio parameter and thermal radiation (Rd) with active and passive controls. The impact of the magnetic field Biot number and thermophoresis parameter on the heat transfer rate has been scrutinized. .

Water-like thermal conductivity of ionanofluids containing high aspect ratio multi-walled carbon nanotubes and 1-ethyl-3-methylimidazolium-based ionic liquids with cyano-functionalized anions

In the era of growing climatic requirements, the search for efficient heat transfer and storage fluids for both industrial and domestic applications is a very important point on the road map of energy transformation in the economies of countries around the world. To achieve the assumed process parameters, working fluids must be characterized by many, often seemingly contradictory, parameters, such as high thermal conductivity and low viscosity, for effective heat transfer. Therefore, the media usually have a very complex structure, which is often designed on the atomic level. An example of such are ionanofluids (INFs) – colloidal dispersions of solid nanoparticles in ionic liquids (ILs). This work aimed to determine the impact and comparison of various cyano-functionalized anions ([SCN]−, [N(CN)2]−, [C(CN)3]−) in 1-ethyl-3-methylimidazolium ([Emim]+) ILs on key properties, such as thermal conductivity, density, viscosity, and structure of INFs, in a wide range of temperature and concentration (up to 10 wt%) of in-house synthesized multi-walled carbon nanotubes (MWCNTs) and carboxyl-functionalized (oxidized) MWCNTs, as well as commercially-available helical carbon nanotubes. Very promising results have been obtained, especially in the case of 1-ethyl-3-methylimidazolium tricyanomethanide [Emim][C(CN)3] with 5.0 wt% loading of ultra-high aspect ratio (up to 11,000) in-house 16 h MWCNTs – thermal conductivity reached 0.532 W·m−1·K−1 at 25 °C which is a threefold improvement (200 %) over the base IL. The thermal conductivity of this value is close to that of water, i.e., an absolute record holder among the conventional heat transfer fluids (0.606 W·m−1·K−1 at 25 °C). The nanofluids were characterized by long-term stability and a wide spectrum of rheological properties, from liquid-like INFs to solid-like ‘bucky gels’, which can be controlled mainly by the morphology and concentration of MWCNTs. For instance, liquid-like [Emim][N(CN)2] + 1.0 wt% in-house 16 h MWCNTs had a viscosity of 34.0 mPa·s (at 186 s−1, 25 °C), which was lower than those of many conventional heat transfer fluids including propylene glycol (42.3 mPa·s, 25 °C), Duratherm® S (49.2 mPa·s, 27 °C), Therminol® 66 (70.8 mPa·s, 27 °C), or Xiameter® PMX-210 (100 mPa·s, 25 °C), while solid-like [Emim][SCN] + 3.0 wt% in-house 16 h MWCNTs had a viscosity up to 8.9 Pa·s (at 18.6 s−1, 25 °C) and may be used in next-generation phase-change materials for efficient thermal energy storage.

EXPERIMENTAL THERMAL PERFORMANCE ANALYSIS OF NANOFLUID ASSISTED SLINKY GROUND HEAT EXCHANGER IN SPACE COOLING APPLICATION

Ground source heat pump has made a severe breakthrough in space conditioning applications due to their high energy efficiency, and expectations for these systems have increased due to using renewable energy. Concerning the increasing expectation, researchers and engineers have increased their research on these systems and focused on cost and efficiency. The efficiency of the ground source heat pump system is directly related to the ground heat exchanger loop, which provides the thermal connection between the heat pump and the ground, and increasing the effectiveness of the ground heat exchanger can be achieved with a nanofluid-based heat transfer fluid. On the other hand, as a ground source heat pump system component, ground heat exchangers have very different design configurations. Among the various configurations, slinky ground heat exchangers are of great interest due to their higher heat transfer efficiency and reduced installation space requirements compared to traditional straight pipe configurations. In this study, the effect of nanofluids on increasing the effectiveness of slinky ground heat exchangers was experimentally investigated and compared with the results obtained using conventional heat transfer fluids. The results obtained from the experimental study determined that using nanofluid at a rate of 0.1% as a heat transfer fluid in slinky ground heat exchangers in cooling applications increased the average effectiveness by about 20%.

Synthesis and Characterization of BaO-Enhanced Therm500 Nanofluids

In this study, we enhance the thermal conductivity of the conventional heat transfer fluid Therm500 by incorporating BaO nanoparticles. BaO:Therm500 nanofluids are synthesized and characterized at various concentrations (ranging from 0.001 to 0.006 g) and temperatures (300 K, 303 K, 313 K, and 323 K). The investigation includes the use of FT-IR spectroscopy to analyze the interaction between BaO nanoparticles and Therm500. Our findings indicate that there is no significant particle-fluid interaction. The enhanced thermal conductivity observed in BaO:Therm500 nanofluids is attributed to multiple factors. As the temperature increases, the viscosity of the nanofluid decreases, resulting in increased Brownian motion of nanoparticles and convective-like effects, ultimately leading to improved thermal conductivity. Additionally, we report the acoustic properties of BaO-Enhanced Therm500 nanofluids at the same four temperatures (300 K, 303 K, 313 K, and 323 K). Density, refractive index, and ultrasonic velocity measurements are performed for six different molar concentrations of BaO nanofluids (0.001 g, 0.002 g, 0.003 g, 0.004 g, 0.005 g, and 0.006 g). Subsequently, various acoustical parameters, such as adiabatic compressibility (β), intermolecular free length (Lf ), specific acoustic impedance (Z), Rao’s constant (R), molar compressibility (W), viscous relaxation time (τ), free volume (Vf ), Gibbs free energy (ΔG), and internal pressure (πi), are calculated. These acoustical characteristics are utilized to investigate molecular interactions within the nanofluid system. The study reveals a non-linear relationship between ultrasonic velocity and particle concentration, which is attributed to weak particle-fluid interactions. These findings provide valuable insights into the preparation and characterization of BaO-enhanced Therm500 nanofluids and their potential applications in heat transfer systems.

Efficiency Enhancement of Heat Transfer Fluids by Using Carbon Dots Nanoparticles Derived From Aloe Vera

Modern technological progress in transportation, medical, electronics and HVAC systems has resulted in an extreme need for a performance-enhanced heat transfer system. Heat transfer employing a flowing fluid is most used, and the thermal properties of liquids play a decisive role in heating and cooling applications in industrial processes. The thermal conductivity of a liquid is an important physical property that decides its heat transfer performance. Conventional heat transfer fluids have inherently poor thermal conductivity, making them inadequate for ultra-high heat transfer applications. Nanofluids are a new class of liquids whose properties are controllable by adding nanoparticles. A great deal of attention has been drawn to their enhanced heat transfer characteristics relative to that of pure fluid. This paper synthesizes three various Nano Fluids and experimentally compares their heat transfer capabilities using a shell and tube heat exchanger setup. An attempt is made to suggest applications for enhanced heat transfer. Al2O3 Nanofluid is compared with Nanofluid containing carbon dots derived from Aloe vera, and it has been found that carbon. Aloe vera yields more heat transfer

Thermophysical properties analysis of Al2O3, MgO and GO nanofluids with water for solar still

The conventional heat transfer fluid like water has limited potential to meet the needs of practical thermal applications. The current analysis is based on the comparative examination of the different heat transfer nanofluids (aqueous Al2O3, MgO, GO nanofluids) incorporated in the set-up of pyramid solar still, and their influence on the solar still performance was evaluated. The thermo physical properties of the prepared nano-suspensions were evaluated and studied. Dispersing nano-sized particles in the conventional heat transfer fluids (base fluid) significantly augments the thermo physical properties of the latter. This augmentation attained in the thermo physical properties depends upon the concentration of nanoparticles in the base fluid. Suspending Al2O3 nanoparticles in water at 1.0 wt% concentration results in the maximum increment of about 1%, 2%, 3%, and 4% in the thermal conductivity, specific heat, dynamic viscosity, and density relative to that of water and suspending MgO nanoparticles in water at 1.0 wt% concentration results in the maximum increment of about 1%, 2%, 3% and 4% in the thermal conductivity, dynamic viscosity, specific heat and density relative to that of water. Utilizing 1.0 wt% Al2O3 mono-nanofluid as the heat transfer fluid in the set-up results in the maximum increment of about 38.52% in the distilled water yield relative to that attained using water. Utilizing 1.0 wt% MgO mono-nanofluid as heat transfer fluid in the set-up results in a maximum increment of about 48.91% in the distilled water yield relative to that attained using water. In this present study, the thermophysical properties of Al2O3, MgO, and GO with water were investigated experimentally.

Nanofluids: New Generation Fluids on Industrialization Path

In the last Editorial, we presented the evolution of the journal "Energy and Thermofluids Engineering, ETE" (Mahbubul 2021) and mentioned that the Journal focuses on three main areas: renewable energy, conventional energy, and thermofluids engineering. The current Editorial is about nanofluids as one of the most promising thermofluids. Nanofluids are complex mixtures of nanoscale solid particles (1-100 nm) with heat transfer fluids. Conventional heat transfer fluids (e.g., water, glycols, refrigerants, oils, etc.) have very low thermal conductivities. This restricts the thermal phenomena, resulting in poor thermal efficiencies and exergetic outputs. When nanofluids are designed to have high thermal conductivity nanoparticles, they exhibit higher thermal conductivities than those of conventional heat transfer fluids.

Effect of nano materials for the nano fluids in solar thermal energy: A review on applications in solar collector

Sun is the prime source of energy in the universe. Solar energy is available freely and has no adverse effect on the environment like greenhouse gases, CO2 emission etc. Hence, solar energy has the significant role amongst all renewable energy sources. The conversion of solar energy into the thermal energy can be done through the flat plate solar collector. The conventional working fluids used in the solar collector has poor thermo-physical properties which lowers the efficiency of solar collector. This review throws light on the latest developments on the performance improvement of solar flat plate collector. The earlier research performed on the use of nanofluids for the performance improvement of solar flat plate collector is comprehensively presented. An extensive research indicates that improving the thermo-physical properties of conventional heat transfer fluid leads to the performance improvement of flat plate solar collector. This can be achieved by the use of nanofluid instead of conventional fluid in solar collector.

Performance analysis of sodium alanate hydride reactor with different nanofluids

The thermal management of the hydride based hydrogen storage reactor is the key factor to realize the complete storing potential of hydrides. In this regards a hydride reactor filled with sodium alanate in multiple tubes is numerically analyzed for absorption process. Based on various governing equations, a mathematical model of hydride reactor is developed and validated with the help of ANSYS Fluent. The hydride reactor uses mainly water or oil for heat exchange during hydrogen sorption. In the present study conventional heat transfer fluid (HTF) is replaced with the nanofluid since it has a greater heat exchange properties. The CuO/HTF, Al2O3/HTF and MgO/HTF nanofluids are selected based on previous studies and results of numerical experiment are recorded. The outcomes are attained for various parameters such as material and concentration of nanoparticles, supply pressure of hydrogen and inlet temperature of heat exchange fluid. The CuO/HTF nanofluid with concentration of 5 vol% exhibited better rate of absorption in comparison with other vol% concentrations and other selected nanofluids. It shows improvement in hydrogen absorption time up to 14% under selected conditions. Additionally, it is observed that CuO/HTF nanofluid with 5 vol% concentration is thermodynamically superior to other selected nanofluids; as a result it enhances the rate of the heat exchange up to 10% for hydride reactor. It is realized that the performance of CuO/HTF nanofluid with 5 vol% concentration is superior among picked nanofluids. Therefore for the hydride reactor the use the nanofluid is advantageous.

Fewer Dimensions for Higher Thermal Performance: A Review on 2D Nanofluids

The current work aims to offer a specific overview of the homogeneous dispersions of 2D nanomaterials in heat transfer base fluids—so-called 2D nanofluids. This data compilation emerged from the critical overview of the findings of the published scientific articles regarding 2D nanofluids. The applicability of such fluids as promising alternatives to the conventional heat transfer and thermal energy storage fluids is comprehensively investigated. These are fluids that simultaneously possess superior thermophysical properties and can be processed according to innovative environmentally friendly methods and techniques. Furthermore, their very reduced dimensions are suitable for the decrease in the size of thermal management systems, and the devices have attracted a lot of attention from researchers in different fields. Some examples of 2D nanofluids are those which incorporate graphene, graphene oxide, hexagonal boron nitride, molybdenum disulfide nanoparticles, and hybrid formulations. Although the published results are not always consistent, it was found that this type of nanofluid can improve the thermal conductivity of traditional base fluids by more than 150%, achieving values of approximately 6500 W·m−1·K−1 and interface thermal conductance above 50 MW·m−2·K−1. Such beneficial features permit the attainment of increments above 60% in the overall efficiency of photovoltaic/thermal solar systems, a 70% reduction in the entropy generation in parabolic trough collectors and increases of approximately 200% in the convective heat transfer coefficient in heat exchangers and heat pipes. These findings identify those fluids as suitable heat transfer and thermal storage media. The current work intends to partially suppress the literature gap by gathering detailed information on 2D nanofluids in a single study. The thermophysical properties of 2D nanofluids and not of their traditional counterparts, as it is usually encountered in the literature, and the extended detailed sections dedicated to the potential applications of 2D nanofluids are features that may set this research apart from previously published works. Additionally, a major part of the included literature references consider exclusively 2D nanomaterials and the corresponding nanofluids, which also constitutes a major gathering of specific data regarding these types of materials. Upon its conclusion, this work will provide a general overview of 2D nanofluids.

Improving the efficiency of the concentrating solar power plants using heat transfer nanofluids with gold nanoplates: An analysis from laboratory to industrial scale

We report about the remarkable changes in the thermophysical properties of the heat transfer fluid used in concentrating solar power plants with parabolic-trough collectors (Dowtherm A, a mixture of diphenyl oxide and biphenyl) by addition of Au nanoplates in mass fractions around 10−2 wt%. The resulting nanofluids are stable for weeks, and their enhanced physical properties make them good candidates for the application. Particularly, with 4.8·10−2 wt% of Au nanoplates, specific heat increases by 12.0 ± 1.2 % at 523 K and thermal conductivity increases by 24.9 ± 6.1 % at 373 K, with no measurable changes in density or dynamic viscosity. This set of physical properties allows to make a realistic estimation of the performance of a prototypical concentrating solar power plant using these nanofluids for solar-to-thermal energy conversion. We determine, using computational cost-free numerical models available in literature, that the performance of a concentrating solar power plant could increase up to 35.1 %, compared to the predicted 24.7 % with the conventional heat transfer fluid, with neither rheological penalties nor economically prohibitive structural changes. The findings here reported may contribute to encourage the application of heat transfer nanofluids in order to improve the efficiency of concentrating solar power plants, and to consolidate a working scheme that positively promotes the transition from laboratory scale to industrial scale.