Heat Transfer In Media Research Articles

Thermal performance improvement of energy storage materials for low operating temperature solar water heating systems

Recent studies have shown the attractive energy storage capabilities of phase change materials (PCMs); however, PCMs may not be fully effective due to their poor heat transfer characteristics. Moreover, the melting point of PCMs restricts direct integration into a solar collector for low operating solar water heating (SWH) applications. This study investigates the heat transfer enhancement of PCMs as well as aiming to lower their melting point onset to expedite the latent heat storage initiation. The selected types of PCMs are paraffin waxes with melting point temperatures of 28–72 °C. In Phase I, silicone oil is selected as a heat transfer medium to be used with the PCMs to establish natural convection enhancement, which led to maximum melting point depression of approximately 3 °C in the PCM72. In Phase II, the conductive heat transfer enhancement was studied by adding nanoparticles with varying mass concentrations. From this analysis, it was determined that PCM72 with 1% multi-walled carbon nanotubes (MWCNT) has shown an increase of approximately 3.81% in thermal conductivity. The obtained results from this study can lead to overall efficiency improvement of SWH systems by employing the PCM mixtures with low melting point, while keeping the high latent heat capacity, and high thermal conductivity.

Thermal performance investigation of Therminol55/MWCNT+CuO nanofluid flow in a heat exchanger from an exergy and entropy approach

Nanofluids have been extensively studied in recent decades and have been regarded as “next-generation heat transfer fluids” due to their superior properties. However, dispersion stability and application at higher temperatures are among the challenges that must be overcome. In this work, a new class of stable hybrid nanofluid based on multi-walled carbon nanotube (MWCNT) + cupric oxide (CuO) nanocomposite is produced with Therminol55 (TH55) as the base fluid. Nanofluids' thermophysical characteristics are investigated at varying concentrations (0.005–0.08 wt%), and they are subsequently employed as the heat transfer medium in a tube heat exchanger (HEX) for the turbulent flow regime. Thermal conductivity was significantly increased by 128.4% at the maximum nanocomposite concentration of 0.08 wt%. Despite this, nanocomposites enhanced the nanofluids' viscosity, which climbed gradually with concentration to a maximum enhancement of around 25% at 0.08 wt%. The heat transfer performance of the formulated nanofluids was numerically assessed and found to be good; for example, when compared to pure TH55, the heat transfer coefficient improved by up to 128%. The highest increase in Nu was 38.4%, while the maximum increase in pumping power was determined to be 103.88%. Furthermore, the maximum exergy efficiency was 47.84% at a 0.08 wt% concentration and a Reynolds number (Re) of 12500, which is somewhat higher than the 40.96% attained with pure TH55. The highest thermal performance factor was 1.31 for 0.08 wt %, exceeding the maximum thermal performance factors of 1.17, 1.11, 1.08, and 1.03 for 0.04, 0.02, 0.01, and 0.005 wt %, respectively. Consequently, a nanofluid made of MWCNT + CuO/TH55 might be a promising candidate for usage as a heat transfer fluid.

Thermal performances evaluation of a flat‐plate solar collector using microencapsulated phase‐change slurry as heat transfer medium

Thermal performances evaluation of a flat‐plate solar collector using microencapsulated phase‐change slurry as heat transfer medium

Use of the Alternating Directions Method in Cylindrical Coordinates, Applied to the Two-Dimension Unsteady Conduction Heat Transfer

Abstract Finding analytical solutions for the unsteady conduction heat transfer equation is generally very difficult due to the intrinsic complexity of the problem. In most cases, the equation has no analytical solutions. A numerical approach that surmounts these difficulties consists of the finite difference technique. The alternate directions finite-difference technique especially suits to the two-dimension heat conduction. The paper considers a hollow cylinder consisting of a conduction heat transfer medium, and the two-direction unsteady heat propagation within this medium is studied by means of the alternate directions method. The approach simulates the heat conduction process during a charge-discharge cycle of a single borehole heat storage.

Bottom-Up Estimates of the Cost of Supplying High-Temperature Industrial Process Heat from Intermittent Renewable Electricity and Thermal Energy Storage in Australia

We report the upper and lower bounds for the levelized cost of high-temperature industrial process heat, supplied from electricity generated with solar-photovoltaic (PV) and wind turbines in combination with either thermal or electric battery storage using hourly typical meteorological year (TMY) data, in systems sized to supply between 80% and 100% of continuous thermal demand at a site in the northern part of Western Australia. The system is chosen to supply high-temperature air as the heat transfer media at temperatures of 1000 °C, which is a typical temperature for an alumina or a lime calcination plant. A simplified model of the electrical energy plant has been developed using performance characteristics of real PV and wind systems and TMY data of renewable energy resources. This was used to simulate a large sample of possible system configurations and find the optimal combination of the renewable resources and storage systems, sized to provide renewable shares (RES) of between 80% and 100% of the yearly demand. This allowed the upper and lower bounds to be determined for the cost of heat based on two scenarios in which the excess energy is either dumped (upper bound) or exported to the electricity grid (lower bound) at the average generating cost. The lower bound of the levelized cost of energy (LCOEL), which occurs for the system employing thermal storage, was estimated to range from USD 10/GJ to USD 24/GJ for RES from 80 to 100%. The corresponding upper bound (LCOEU), also estimated for the system using thermal storage, are between USD 16/GJ and USD 31/GJ, for RES between 80% and 100%. The utilization of electric battery storage instead of thermal storage was found to increase the LCOE values by a factor of two to four depending on the share of renewable energy. Compared with current Australian natural gas cost, none of the systems assessed configurations is economical without either a cost for CO2 emissions or a premium for low-carbon products. The estimated cost for CO2 emission that is needed to reach parity with current natural gas prices in Australia is also presented.

Corrosion Behavior of Aluminum-Forming Alloy 310S for Application in Molten Chloride Salt CSP Thermal Storage Tank

The key to the new generation of solar thermal power plants is to increase the operating temperature of molten salt to 800°C, and change the heat transfer medium from nitric acid mixed salt to chlorine mixed salt, so as to significantly reduce the cost of power generation. Therefore, the alloy material’s resistance to high temperatures and fusible chloride salt is one of the core technologies for the successful implementation of concentrated solar power (CSP) technology. In this study, the aluminum-forming alloy (AFA) 310S for the heat storage tank was prepared by the aluminum-thermal reaction casting method. The hot corrosion behavior and mechanism of AFA 310S in chloride molten salt at 800°C were studied by static immersion etching for 600 h. AFA 310S exhibits good thermal corrosion properties in KCl 20.4 wt% + MgCl2-55.1 wt% + NaCl 24.5 wt%. The results indicate that compared with commercial 310S, AFA 310S has better oxidation resistance at 800°C. At the initial stage of corrosion, dense Cr2O3 and continuous Al2O3 passivation films are formed. At the same time, MgO-rich oxidation products were produced in the outermost layers of the two alloys during the 600 h process. Over time, however, the damage caused by chlorine became more apparent, mainly due to the “oxidation-chlorination” process of the metal. A large number of cavities and cracks on the surface are formed, and the oxide layer has obvious spalling. When the Al element was added into the alloy, the dense passivation film could be formed after 120 h of corrosion with the stronger corrosion resistance. The experiment simulated the corrosion behavior in the worst environment, such as air, unoxidized alloy, molten salt without corrosion inhibitor, etc. By weight loss calculation, commercial 310S plate is completely unsuitable for CSP plant. The corrosion rates of the two alloys are compared as follows: commercial 310S > AFA 310S. To sum up, AFA 310S has a good application prospect in concentrated solar power.

Parabolic trough field control utilizing all sky imager irradiance data – A comprehensive robustness analysis

Parabolic trough (PT) power plants focus the sun's irradiation onto an absorber tube using collector mirrors to increase the temperature of the heat transfer medium (HTF). In the power plant, the HTF is used to generate electricity. To heat up the HTF, PT solar fields are set up in large areas and pipes are used to distribute the HTF in the solar field. The control system adjusts the temperature by changing the mass flow into the solar field and the focusing of the individual collectors. Transient conditions such as cloud passage are the main challenge for the system. State of the art control schemes use information from a few irradiation measuring points in the solar field. These measurement points are precise for the individual location but cannot accurately represent the irradiation situation in the whole solar field. In this paper, a control system that uses spatially resolved irradiation information from all sky imager systems is investigated.First, the control system was developed and tested in various simulation runs under ideal conditions. The focus of this work is to investigate the robustness of the control concept under non-ideal conditions. For this purpose, the simulation conditions are adapted to real situations and the behavior of the control system is analyzed.A robust behavior of the control system is shown in the simulations under different non-ideal scenarios. Overall, an improvement in electrical yield of 1.4% can be achieved compared to a reference without access to spatially resolved irradiance data.

Sulfate Freeze–Thaw Resistance of Magnesium Potassium Phosphate Cement Mortar

Concrete facilities in the severe-cold areas of western China (salt lake environments and heavy saline soils) are seriously damaged by the multiple corrosion effects of freeze–thaw cycles and sulfate corrosion. Magnesium phosphate cement (MPC) cement-based material has become an ideal concrete structural component because of its superior performance. Because concrete structural repair materials are used in heavy-corrosion environments, their durability in those environments should also be considered. Regarding the salt-freezing resistance of MPC, the existing studies have all used a NaCl solution as the heat transfer medium. In addition to chlorine salt, sulfate, especially Na2SO4, is also common in typical use environments such as oceans, salt lakes, and groundwater. To evaluate the sulfate freeze–thaw resistance of potassium magnesium phosphate cement (MKPC) mortar, in this study the strength development, weight loss, and water absorption of MKPC mortar specimens subjected to different freeze–thaw cycles were tested and compared with those for Portland cement (P.O) mortar specimens of the same strength grade. The results showed that the P.O mortar specimen completely lost its strength after 75 cycles of rapid water freezing and thawing and 50 cycles of sodium sulfate solution (5%) freezing and thawing. However, the residual strength rating of the MKPC mortar specimen after 75 cycles of water freezing and thawing and 100 cycles of sodium sulfate solution freezing and thawing was higher than 75%. After 50 rapid freeze–thaw cycles in water and a 5% Na2SO4 solution, the P.O mortar specimen’s mass loss exceeded the 5% failure standard, whereas the mass loss of the MKPC mortar specimens was much less than 5%. Before the freeze–thaw cycles, the water absorption of the P.O mortar specimen was close to 8 times that of the MKPC mortar specimen, and after 50 water freeze–thaw cycles and 25 sulfate solution freeze–thaw cycles, the water absorption reached 4.88% and 5.68%, respectively. However, after 225 freeze–thaw cycles in water and the sulfate solution, the water absorption rates of MKPC mortar specimens were 2.91% and 2.51% respectively. The test and analysis results show that the freeze–thaw resistance of MKPC mortar was much higher than that of Portland cement mortar specimens. Those results provide a prerequisite for applying and expanding the use of MKPC-based materials in severe-cold areas of western China (salt lake and heavily saline soil environments).

Contribution to research on ground heat storages as part of building energy systems using RES

Contribution to research on ground heat storages as part of building energy systems using RES

Review of the spectrally selective (CSP) absorber coatings, suitable for use in SHIP

A key component in the conversion process of concentrated solar power (CSP) into thermal energy is a solar absorber coating. Many experimental and simulated coatings for various substrates for CSP water/steam or molten salt absorbers have been developed. The main challenges today remain in the selection of a low-cost and effective fabrication method, appropriate for industrial production, and assessment of the degradation rate and service life of these coatings, which affect the efficiency of the plant and the LCOE. In this article, we review different types of mid- (100 < T < 400 °C) and high-temperature (>400 °C) absorber coatings and their fabrication methods. The emphasis is on the solar absorptance, thermal emittance and the long-term (>10 years) thermal stability of the coatings. Spectral selectivity of the coatings, which is more difficult and expensive than other means, was proven to be essential for a low-to-mid temperature range and low concentration ratios, yet for high temperatures and high concentration ratios, high solar absorptive coatings can achieve the same or even better performance than spectral selective ones. Important factors for an efficient CSP absorber are compatibility of the coating and substrate under cyclic temperature conditions and high heat transfer rate to a heat transfer medium.

Numerical study on charging performance of multi-enclosed thermal storage: Multiple versus integrated thermal storage

Phase change materials can be considered as innovative heat transfer media that allow to accumulate energy for a charge period and to produce energy for a discharge period. Such materials are widely used in building elements, electronic cabinets and other technical systems. At the same time, the heat conductivity of known phase change materials are very low and for an intensification of heat transfer it is possible to include in the considered systems the porous structure or solid matrix. The present research deals with numerical analysis of charging period of phase change material in a square cavity filled with phase change materials and heated from the bottom wall. For an augmentation of energy transport the vertical heat-conducting partitions are added to this cavity. Using the enthalpy porosity model, numerical analysis has been performed for different numbers of vertical partitions illustrating also the evolution of the charging period. It has been shown that a rise of the vertical partitions number results in reduction of charging period with suppression of convective energy transport mode. Moreover, evolution of phase change material melting reflects a strengthening of this process due to heat conduction enhancement with high volume of solid partitions of high thermal conductivity.

Chloride Salt Purification by Reaction With Thionyl Chloride Vapors to Remove Oxygen, Oxygenated Compounds, and Hydroxides

Molten chloride salts (including MgCl2, KCl, NaCl, and ZnCl2) are being considered for heat transfer media for renewable (solar) and nuclear power generators, as fuel carrier for nuclear reactors, and as thermal energy storage media. Impurities such as oxygen, hydroxides, moisture, and sulfur are known to negatively influence the corrosion of materials in contact with the salt (e.g., structural metals). Commercially available chloride salts come with a range of impurities. Before using the chloride salts at high temperature, it is desirable to remove the impurities to increase the performance of the salt and reduce corrosion. In this study, we tested the use of thionyl chloride vaporized into a stream of argon to react with oxygenated impurities in a mixture of MgCl2-KCl-NaCl, removing them as HCl and SO2. The reagent was bubbled through the salt when both above and below the melting point. The reaction was followed using thermocouple data from the salt and by Fourier transform infrared (FTIR) spectroscopy on the exhaust of the reactor. The reaction kinetics were followed by comparing the peaks from SO2 product to SOCl2 reagent in the FTIR spectra. The purity of the salt was assessed at the end of the purification process by x-ray diffraction and inductively coupled plasma analysis. Although the process was effective in removing the oxygen content of the mixture, ternary compounds were formed in the process, including KNiCl3 and KMgCl3. The nickel in KNiCl3 came from the reaction between the salt and the nickel vessel. Thus, these experiments suggest that improvements to the process must be made before using SOCl2 vapors for the purification of chloride salts.

Optimal design of heat pump integrated low-grade heat utilization systems

Recovery and utilization of low-grade heat in the process industries offers considerable economic and environmental benefits. Low-grade heat utilization employs circulating medium for heat transfer between heat sources and sinks. Thus, it is in need to synchronously integrate heat sources, circulating medium and heat sinks. It is extremely challenging for optimal design of low-grade heat utilization systems (LHUS) when considering quantity and quality of heat sources, heat sink requirements, feasible integration technologies and economic performance simultaneously. The current design methods for low-grade heat utilization integrated with up-grading technologies are simplified, narrowing down their integration domain. In this work, integration strategy of LHUS with heat pump technology is first proposed. A novel methodology for optimal design of heat pump integrated low-grade heat utilization systems (HPiLHUS) is developed subsequently for implementing the integration strategy. A modified superstructure characterized by nodes, low-low pressure steam (LLPS) generation module and a heat pump system is presented. The node acts as mixer, splitter or heat exchanger, and thus enables HPiLHUS optimization in all feasible domain. The LLPS generation module provides a promising integration possibility for heat pump technology. The heat pump system aims to upgrade low-grade heat in order to improve energy utilization efficiency. A mixed-integer non-linear programming (MINLP) model is formulated for optimal design of LHUS/HPiLHUS. Real-world case studies are employed to demonstrate our method’s efficacy and applicability. The results show that integration of heat pump technology with LHUS reduces total annual cost (TAC) by 12.2%, demonstrating huge potential for reduction of energy consumption. Scenario analysis exhibit the advantages of our proposed modified method over conventional methods. Sensitivity analysis shows LLPS generation temperature and excavated heat sink duty have a great impact on TAC, which provides valuable information for implementing the heat pump integration strategy. The proposed methodology can be applied to industrial low-grade heat utilization and thus has a wide scope of applications.

Characterization of Low-Cost Particulates Used as Energy Storage and Heat-Transfer Medium in Concentrated Solar Power Systems.

Utilizing solid particles as a heat-transfer medium in concentrated solar power applications has gained growing attention lately. Unlike molten salts, solid particles offer many benefits, which include: high operating temperatures (greater than 1000 °C), a lack of freezing issues and corrosivity, abundant availability, high thermal energy storage capacity, a low cost, and applicability in direct irradiation. Comprehensive knowledge of thermophysical and optical properties of solid particles is essential to ensure an effective harnessing of solar energy. The most important considerations when selecting solid particles include: thermophysical and optical properties, thermal resistance, crack resistance, satisfactory health and safety risks, availability, and low cost. It is also imperative to consider optical and thermophysical characteristics that might change from what they were “as received” after cyclic heating for a long period. Therefore, the knowledge of thermal performance of particulate materials becomes significant before using them as a heat-transfer medium. In this study, some particulate materials were chosen to study their feasibilities as heat-transfer and storage media for a particle-based central receiver tower system. These particulate materials included white sand, red sand, ilmenite, and Carbobead CP. The candidate particulate materials were heated at high temperatures for 6 h and then cooled to room temperature. After that, cyclic heating was performed on the particulate materials for 500 h at 1200 °C. The optical properties were represented by weighted solar absorptance, and the thermophysical properties of the particulates were measured “as received” and after cyclic heating (aging). EDX and XRD were conducted to quantify the chemical composition and interpret the changes in appearance associated with the particulate materials after cyclic heating. The results showed a considerable agglomeration in all particulates except for white sand in the 6 h heating test, and high agglomeration in the ilmenite. A slight decrease in the optical properties in the white sand and Carbobead CP was found after the aging test. The specific heat was decreased for red and white sand. The EDX and XRD results for white sand and Carbobead CP showed chemical stability, indicating high durability and reliability.

Intensification of Heat and Mass Transfer in a Diabatic Column with Vortex Trays

We used vortex contact devices that we developed and investigated to make a new design of an alcohol diabatic distillation column with heat exchange pipes (as the reflux condenser) passing through concentrating section trays. In the column, ascending vapors partially condensed on the surface of vertically installed heat exchange tubes, forming a reflux. The reflux was then mixed with the draining liquid flow in the vortex contact devices placed on the trays. Heat was removed from the column through the boiling of the draining water film along the inner surface of the heat exchange pipes. We compared both diabatic and adiabatic columns fitted with the developed vortex contact devices on the trays. The proposed innovative contact system allows increasing productivity, reducing column dimensions and steam- and heat-transfer medium consumption, and increasing separation efficiency. Dependences for calculating the gas content, hydraulic resistance, and interphase surface required for designing the vortex contact devices of the proposed unit trays are presented.

Experimental Study on Separate Heat Pipe-type Passive Residual Heat Removal System of Swimming Pool-type Low-Temperature Heating Reactor

The use of separate heat pipe in Passive Residual Heat Removal System (PRHRS) for Swimming Pool-type Low-Temperature Heating Reactor (SPLTHR) has a good application prospect. An experimental study on miniaturized separate heat pipe-type PRHRS has been carried out. The heat transfer medium in the separate heat pipe is water and is at sub-atmospheric. The boundary conditions of the experiment refer to the operating range of SPLTHR. The two-phase natural circulation characteristics of the separate heat pipe-type PRHRS and the influence of boundary conditions on the system heat transfer capacity, flow instability and heat stratification of pool water are studied. Within the experimental range, the heat transfer rate is from 72.0 kW to 459.2 kW and the steam mass flowrate is from 0.031 kg/s to 0.197 kg/s. During the operation of the system, there is long-term flow instability. The process and causes of system instability are analyzed from the perspective of heat transfer. It is believed that the natural convective heat transfer outside the tube bundle hinders the heat transfer, resulting in instability. The heat transfer capacity of the system under three filling ratios of 30%, 50% and 70% was studied, and the results showed that the filling ratio within this variation range had little effect on the heat transfer capacity of the system. Furthermore, the thermal stratification in the pool has been analyzed.

Experimental and Numerical Study on the Dynamic Thermal Response of Building Interior Decoration Coatings during Intermittent Air-Conditioning in High U-Values Buildings in China

Interior decorating coatings (IDCs) are the heat-transfer medium between indoor air and building walls, which mainly form the cooling load and are important in an indoor built environment. To explore the impacts of the precooling process of IDCs on indoor thermal environment of occupants during intermittent air conditioning, this paper investigated the dynamic thermal response of IDCs. Three representative coating materials were integrated to the external insulation wall and internal insulation wall, and their interior surface temperatures were experimentally tested under intermittent air conditioning operation in southern China. Moreover, a heat transfer model was established and verified to analyze the influences of IDC on the thermal response of the interior surface. During the pull-down process, the cold was accumulated in the IDC layer with small thermal diffusivity and could not be transferred into the wall inside, so that the largest temperature reduction was obtained, meaning that the indoor thermal environment could meet the setpoint in a short time. According to modelling calculations, the thick IDC with volumetric specific heat capacity less than 1 × 105 J/(m3·K) and small thermal conductivity integrated to the internal insulation wall was beneficial to increase the thermal response rate and had the better energy-saving efficiency.

Heat transfer of granular flow around aligned tube bank in moving bed: Experimental study and theoretical prediction by thermal resistance model

Gravity-driven granular flow has been the heat transfer mediums in moving bed heat exchangers, which play vital roles in industrial heat saving and solar energy utilization. However, the heat transfer mechanism of granular flow is still worth of investigating around the tube bank. In this work, the aligned tubes were arranged in the moving bed, and the heat transfer of metallurgical slag was experimentally tested. It was found that, the heat transfer coefficients are significantly sensitive to the flow rate in the slow granular flow. The smooth flow with particle mixing can improve the heat transfer, while the local particle lagging will worsen the heat transfer around aligned tubes. To predict heat transfer coefficients of granular flow, the contact thermal resistance and the penetration thermal resistance are built with empirical factors (χ, a and η). In the near-wall region, x represents the sensitivity of the contact thermal resistance to particle sizes. Meanwhile, the contact time can be modified by a and η for the penetration thermal resistance in the funnel flow structure. The values of a and η are affected by the granular flow pattern, which tend to decrease in the smooth flow with strong particle mixing. Verified with the present experimental results and the previous literature data, the thermal resistance model has great potentials to explain the heat transfer around the aligned tube bank.

Characterization of radiation damage in 3D printed SiC

• High-purity SiC composites fabricated by additive manufacturing were irradiated. • Radiation-induced defects are easily observed in α-SiC particles but not CVI matrix. • Defect swelling measured by STEM-EELS is similar in α-SiC particles and CVI matrix. • Defect types and swelling are consistent with other forms of nuclear-grade SiC. • Interface denuded zone reveals sink strength bias and relative defect-type mobility. The SiC fuel matrix for advanced gas-cooled high temperature reactors as part of the Transformational Challenge Reactor program serves as the fuel particle container structure, a barrier to fission gas release, and a heat transfer medium. Its performance is particularly important because the fuel matrix must demonstrate good structural stability and thermal behaviors. An additive manufacturing methodology combining a binder jet 3D printing process with chemical vapor infiltration (CVI) for the production of SiC was recently developed. In this study, post irradiation examination by transmission electron microscopy shows that defect accumulation within the printed particles is very similar to other forms of high-purity SiC. However, damage accumulation was not directly observed in the CVI matrix because black spot damage and dislocation loops are difficult to image within the nanoscale highly faulted CVI matrix and because interstitial defects may rapidly annihilate at the stacking faults. Therefore, electron energy loss spectroscopy (EELS) analysis was used to analyze defect swelling in both the printed particles and the CVI matrix. The EELS analysis helped reveal that the radiation-induced swelling in the CVI matrix is similar to that of the printed SiC particles. This work shows that 3D printed SiC has behavior that is comparable to SiC processed by other means and that 3D printing could serve as a suitable processing technique for high-purity SiC for nuclear applications.

Effect of surfactants on the stability, rheological properties, and thermal conductivity of Fe3O4 nanofluids

Stability is the major factor that enables the application of nanofluids in energy conversion systems. Excellent rheological and thermal conductivity is the key for nanofluids to be an ideal heat transfer medium. In this work, we investigated the stability of Fe3O4 nanofluids by four characterization techniques, mainly from the viewpoint of surfactant type and mass ratio, and systematically studied its rheological and thermal conductivity properties by different experimental methods and analyzed the behavior of magnetic fluid thermal anisotropy by mathematical methods. The experimental results show that the surfactant Tetramethylammonium hydroxide (TMAH) has the best stability effect and can keep the Fe3O4 nanofluids more than 120 h. And the best ratio is when the mass ratio of Fe3O4 to TMAH is 1:4. The surfactant Polyvinylpyrrolidone (PVP) has the greatest effect on nanofluids viscosity. The increase in TMAH mass leads to a Newtonian fluid behavior of the nanofluids at low temperatures and low shear rates, besides shifting its shear thinning towards the high temperature region. However, from the curve relationship between the shear rate and shear stress, the Fe3O4 nanofluids belongs to the expansion fluid among non-Newtonian fluids. The surfactant Sodium dodecyl sulfate (SDS) have the greatest effect on the thermal conductivity of Fe3O4 nanofluids. Theoretical calculations show that as the concentration increases, the rate of heat transfer in the direction of the parallel magnetic field is significantly greater than in the direction of the perpendicular magnetic field, while the rate of heat transfer in the absence of a magnetic field is somewhere in between.