Heat Transfer Oil Research Articles

Primary Factors Affecting the Efficiency of Thermoelectric Power Generation Sheets for Waste-Heat Recovery from the Ship’s Exhaust Gas

In order to investigate the effect of different influencing factors on the application of temperature differential power generation in the ship exhaust gas and to explore the potential of waste heat recovery and the utilization of exhaust gas during ship travel, an experimental system based on the temperature differential power generation of ship exhaust gas in the marine environment was established. The maximum output power and the maximum efficiency of each temperature-difference power generation module were theoretically calculated. The results showed that the insulation material and the salt water (seawater) had little effect on the efficiency of the temperature differential power generation modules. Conversely, the installation pressure, the heat transfer oil, the cooling water temperature (seawater temperature), and the heat source temperature (exhaust gas pipe temperature) had a great influence on the open-circuit voltage and the maximum output power. The thermally conductive silicone grease and the cooling water temperature of 10 °C increased the open-circuit voltage by 31.54% and 18.95%, respectively, and increased the maximum output power by 82.05% and 51.79%, respectively. The maximum output of a single temperature differential power generator reached 63.5% when using an installation pressure of 3 bar, a cooling water temperature of 20 °C, double-layer aluminum insulation, and thermally conductive silicone grease. Finally, this study provides relevant data support for using temperature differential power generation devices for ship exhaust gas.

Photothermal Conversion Characteristics of ZnO/MWCNTs Binary Nanofluids and ZnO/MWCNTs/Au Ternary Hybrid Nanofluids in Direct Absorption Solar Collectors

Herein, the oil‐based ZnO/multiwalled carbon nanotubes (MWCNTs) binary nanofluids and ZnO/MWCNTs/Au ternary hybrid nanofluids are proposed. The effects of nanoparticles concentration, and the ratio of ZnO and MWCNTs on the optical properties and photothermal conversion performance are experimentally analyzed. Compared to the base fluid (heat transfer oil), the transmittance of the nanofluids decreases with increasing nanoparticle concentration. The ZnO/MWCNTs nanofluids show slightly higher optical absorption performance than MWCNTs due to the multiple scattering caused by the ZnO hierarchical structure. The ZnO/MWCNTs nanocomposites decorate with gold nanoparticles (Au NPs) to form ZnO/MWCNTs/Au ternary hybrid nanofluids. The ZnO/MWCNTs/Au nanofluids have slightly higher absorption performance in the visible region due to the plasmonic effect exhibited of the Au NPs. The photothermal results show that the maximum value of photothermal conversion efficiency (91.2%) of ZnO/MWCNTs nanofluids is achieved when maintaining the solid content of MWCNTs at 0.01 wt% and the ZnO and MWCNTs ratio of 2:3. The photothermal conversion efficiencies of MWCNTs and ZnO/MWCNTs/Au nanofluids are enhanced by about 35.6% and 42.8%, respectively. This work demonstrates that ZnO/MWCNTs and ZnO/MWCNTs/Au nanofluids have potential application as working fluids for direct absorption solar collectors.

Experimental research and simulation verification of recycling process of heat transfer oil

Experimental research and simulation verification of recycling process of heat transfer oil

Experimental research and simulation verification of recycling process of heat transfer oil

Experimental research and simulation verification of recycling process of heat transfer oil

Heat transfer and cost analysis of circular heating source based tubular rods loaded with thermal oil-MWCNT nanofluid

Nanofluid is a suspension of nanoparticles (NPs) in conventional fluids. It has emerged as a smart material for transferring heat efficiently and has a great potential to be used as a coolant. In this work, nanofluid is designed by considering multi walled carbon nanotubes (MWCNT) suspended in heat transfer oil. The focus is on the heat transfer through natural convection for a specific geometry of circular heating source based tubular rods. In particular, this is representative of heating by micro-processors and other electronic components. Comsol Multi-Physics 5.5 software has been used for investigating the temperature and velocity profile for different concentrations of MWCNT NPs in this geometry. Significant enhancement in outlet temperature of the nanofluid even at low concentration of the NPs has been observed. This signifies an efficient heat extraction from the circular heat point sources (microprocessors) in the tube. On the basis of mathematical formulation, cost analysis of the proposed system has been performed and the cost per heat point source (Chps) has been estimated for fixed concentration of CNTs (0.5%) with interest rates of 4%,8%,and10%. For life spans of 30 and 50 years of the system, the corresponding Chps is found to be 12.34$,14.10$,15.55$and10.06$,12.98$,14.74$ respectively using CNTs. Moreover, the outlet of the proposed system can be coupled with other photovoltaic thermal (PVT) based systems as an application i.e., solar distillation and solar water heaters in order to improve their efficiency.

Ternary molten salt energy storage coupled with graphene oxide-TiN nanofluids for direct absorption solar collector

Owing to the obvious advantages of direct solar collectors, considerable research has been continuously conducted for improving the efficiency of solar energy storage. Due to the instability in the solar energy reaching the Earth and the uneven distribution of solar irradiation during the day and night, it is difficult to continuously output the heat source. In order to further improve collection system performance, we have proposed a direct absorption solar collector, which uses graphene oxide (GO) nanosheets and titanium nitride (TiN) nanoparticles mixed with heat transfer oil as the working fluids, and uses a ternary mixed molten salt (44% Ca(NO3)2, 12% NaNO3, and 44% KNO3) as the heat storage core. Moreover, this new kind of collector has been experimentally investigated, and its solar thermal performance is studied with different proportion of GO to TiN in the nanofluids. The experimental results show that the maximum thermal energy can be stored in the collector is nearly 526.96 J, and the energy retention rate can reach 51.7%. Moreover, the solar thermal efficiency of this collector is up to 56.5%. In addition, the mechanism of heat storage is also studied in detail. This study provides a practical avenue for improving the application potential solar collector, which can effectively promote the heat storage for medium temperature of the collector subjected to incident irradiation.

Comparative Experiment of Wellbore Self-Circulation Heat Mining Capacity with Different Heat-Carrying Fluids

Abstract Based on the principle of wellbore self-circulation heat mining, the evaluation experiments of local wellbore self-circulation heat exchange laws and influencing factors were carried out. Water, SCCO2, R134a, and heat transfer oil were screened as the heat-carrying fluids. The heat exchange laws and heat mining capacity of these four heat carrying fluids were analyzed and compared, and their heat mining rates at the field scale were estimated using the similarity criterion method according to the experimental results. The results show that R134a and heat transfer oil can obtain the largest outlet temperature and the largest heat loss ratio, while the water can achieve a higher heat mining rate and a larger convective heat transfer coefficient than the other three fluids. The heat mining capacity of CO2 is significantly affected by the injection pressure. It is necessary to optimize the injection pressure larger than critical point to achieve the best heat mining performance. When the water is selected as the heat-carrying fluid, the heat mining rate can reach more than 1 MW if a horizontal wellbore with a length of 2000 m is applied for wellbore self-circulation at the field scale.

Effects of Methyl Cellulose and Soybean Protein Isolate Coating on Amount of Oil and Chemical Hazards in Chinese Fried Dough Cake

Fat-related diseases and chemical hazards produced during the frying process pose a major threat to human health. Coatings have been used as a practical method to reduce the amount of oil and chemical hazards associated with fried foods. Methyl cellulose (MC) and soy protein isolate were used as coating materials to pretreat Chinese fried dough cake (CFDC) before frying. The 1.5% MC concentration was the best choice for coating to simultaneously lower oil and chemical hazards in CFDC. The CFDC prepared using 1.5% MC had 11.3% oil, 73.70 μg/kg acrylamide, 0.15 mg KOH/100 kg acid, 8.54 mmol/kg peroxide, p-anisidine value of 6.36, 0.36 μg/g malondialdehyde, 0.13 μg/g 4-hydroxy-2-(E)-hexenal (HHE), 0.51 μg/g 4-hydroxy-2-(E)-nonenal (HNE), and 4,272 μg/kg glycidyl ester. In contrast, the uncoated CFDC had 19.2% oil, 117.55 μg/kg acrylamide, 0.25 mg KOH/100 kg acid, 14.40 mmol/kg peroxide, p-anisidine value of 9.76, 0.63 μg/g malondialdehyde, 0.23 μg/g HHE, 0.86 μg/g HNE, and 5,758 μg/kg glycidyl ester. MC and soy protein isolate enhanced the oil barrier of the coating film, which effectively reduced the heat transfer coefficients, oil transfer, oil oxidation, and chemical hazards in the CFDC. Our work on this edible coating contributes to methods for control of oil and chemical hazards in fried foods.

Liquid medium annealing for fabricating durable perovskite solar cells with improved reproducibility.

Solution processing of semiconductors is highly promising for the high-throughput production of cost-effective electronics and optoelectronics. Although hybrid perovskites have potential in various device applications, challenges remain in the development of high-quality materials with simultaneously improved processing reproducibility and scalability. Here, we report a liquid medium annealing (LMA) technology that creates a robust chemical environment and constant heating field to modulate crystal growth over the entire film. Our method produces films with high crystallinity, fewer defects, desired stoichiometry, and overall film homogeneity. The resulting perovskite solar cells (PSCs) yield a stabilized power output of 24.04% (certified 23.7%, 0.08 cm2) and maintain 95% of their initial power conversion efficiency (PCE) after 2000 hours of operation. In addition, the 1-cm2 PSCs exhibit a stabilized power output of 23.15% (certified PCE 22.3%) and keep 90% of their initial PCE after 1120 hours of operation, which illustrates their feasibility for scalable fabrication. LMA is less climate dependent and produces devices in-house with negligible performance variance year round. This method thus opens a new and effective avenue to improving the quality of perovskite films and photovoltaic devices in a scalable and reproducible manner.

Evening out the heat

Solar Cells The conversion of precursors into the active layer of perovskite solar cells normally occurs by heating the underlying substrate. Conversion tends to occur near the top of the film, where solvent is lost, and unwanted preheating of reactants occurs near the substrate before the reaction. Li et al. show that the use of a surrounding heat transfer oil (anisole) leads to more rapid and even heating, removes solvent, and avoids air and water contamination effects. The larger grains and more uniform films led a much greater retention of efficiency in moving from small-area to large-area devices. Science , abh3884, this issue p. [561][1] [1]: /lookup/doi/10.1126/science.abh3884

Multi-Field Collaborative of Oil-Immersed Transformer for Distributed Energy Resources Temperature Rise Considering the Influence of Heat Transfer Oil

The current calculation method of fluid–structure interaction (FSI) has a defect for oilimmersed transformers for distributed energy resources (DERs). In order to solve this problem, a calculation method is proposed for the temperature rise of oil-immersed transformers in this article. The vibration of insulating oil is considered in this method. Different from the temperature field model established by FSI, the effect of insulating oil vibration on the temperature field is considered. The structure field is introduced to establish the insulating oil vibration model. The temperature field correction coefficient is introduced by coupling the insulating oil vibration and the natural convection of the insulating oil. The result shows that compared with FSI, the results of the calculation method in this study are consistent with the experiment, and the temperature field distribution in the oil-immersed transformer can be calculated more accurately.

Simulation and Experimental Study of the Preheating Mould Temperature Distribution in Semi-Solid Diecasting

The mould temperature distribution has a great influence on the semi-solid diecasting. In the present study the temperature distribution of a plane-shaped mould was investigated by using the method of numerical simulation and experiment. The results showed that the preheating mould temperature field was affected by three important simulation parameters, the heat transfer coefficient hoil between the heat transfer oil and the mould, the heat transfer coefficient hair between the mould and the air, and the heat transfer coefficient hcontact between the mould core and the mould frame. The simulation results showed that (1) with the increase of hoil, the overall mould temperature imcreased; (2) with the increase of hair, the overall mould temperature decreased, while the surface temperature gradient of mould frame grad T-f and the temperature difference between the mould core and the mould frame ∆T increased; (3) With the increase of hcontact, ∆T decreased and the temperature of mould frame increased. When the heat oil temperature Toil=290°C, the heat transfer coefficients were optimized as hoil=500Wm-2K-1, hair=7Wm-2K-1, and hcontact=1000Wm-2K-1 according to the experimental results. The average temperature difference between the simulation result and the experimental result was 3.45°C, and the average relative error was 1.73%.

Rolling-horizon dispatch of advanced adiabatic compressed air energy storage based energy hub via data-driven stochastic dynamic programming

Faced with environmental pollution and energy crisis, energy hub yields an improvement on efficiency and flexibility of multi-energy supply. Advanced adiabatic compressed air energy storage (AA-CAES) is a promising large-scale energy storage technology and is attracting increasing attention due to its heat-electricity co-storage potentials. This paper investigates the external characteristics of advanced adiabatic compressed air energy storage and exploits its ability to implement an energy hub. First, a dual state-of-charge (SoC) model of advanced adiabatic compressed air energy storage is presented, taking into account the system off-design features and the impact of ambient temperature. The state-of-charge of the air storage tank depends on the mass of stored air, whose mass flow rate affects the charging and discharging electric power. The state-of-charge of the high-temperature thermal energy storage depends on the mass of heat transfer oil, whose mass flow rate determines the reserving and releasing heating power. Adjusting the mass flow rates of air and oil offers flexible control on the power and thermal outputs. An energy hub is built based upon the advanced adiabatic compressed air energy storage. To address the daily self-dispatch of the energy hub facing the uncertainties of load and ambient temperature, a data-driven stochastic dynamic programming model is proposed which allows a rolling horizon implementation. The Kernel regression is employed to estimate the conditional probability distribution of uncertainties. The cost-to-go functions in the Bellman equation are approximated via sampling and interpolation. Case studies validate the effectiveness of the proposed approach. The results indicate that: 1) The proposed dynamic programming method outperforms model predictive control in computational efficiency. 2) Neglecting the temperature effect on compressed air energy storage operation leads to 4.5%, 7.8%, and 9.2% regulation errors of charging, discharging and heating power, respectively.

Effect of gas-liquid two-phase macro-mixing on the uniformity of temperature distribution in a top-blown stirred tank using image analysis

This paper investigates the effect of two-phase mixing of gas and liquid in a top-blowing mixing tank on the uniformity of temperature distribution, using hot heat transfer oil and air as the working medium. Results show that temperature difference is the main factor influencing the temperature field uniformity in the mixing tank, and the uniformity of the temperature distribution increases with the temperature difference increased, while the increase of the air flow and the insertion depth of the gun has less influence on the uniformity of the temperature distribution. In addition, a new threshold selection method is proposed for grayscale maps with temperature fields corresponding to different color gradations, in which the overall mean is replaced by the mean of the grayscale values in the target region, and a highly correlated model between the temperature field and the grayscale map is determined with a correlation coefficient of 0.98. Using a thermal imaging camera and digital image processing techniques, combining with a deviation approach, a relative ratio η between the uniformity of the two-dimensional temperature field distribution and the uniformity of the pixel distribution of its corresponding grayscale map is established. In particular, the indicator shows an interesting trend with an increasing temperature difference, i.e., the ratio is close to 1. The effect of bubble-flow topology on the uniformity of temperature distribution was explored, and it was found that betti numbers averages were negatively correlated with temperature distribution uniformity factor. Finally, a correlation model (correlation coefficient of 0.95) between the uniformity of the temperature field distribution and the average volumetric thermal coefficient was obtained experimentally.

Natural Recyclable High-efficiency Oil-water Separation and Interfacial Dye Adsorption Material: Duck down Fiber

ABSTRACT Present study reports the application potential of a natural down fiber in the fields of oil-water separation and interfacial dye adsorption. The dripping experiment shows that the blue water droplets can maintain a spherical shape on the surface of the fiber with a contact angle of 155.8°, while the contact angle of oils was 0°, indicating that the fiber has superhydrophobic and ultralipophilic characteristics. Further studies reveal that this fiber has excellent absorption capacities for various oils with 120.11 g/g (vacuum pump oil), 102.11 g/g (heat transfer oil), 99.27 g/g (engine oil), and oil retention capacities after 24 hours with 94.51%, 94.29% and 92.14% respectively. The oil absorption ratios after ten cycles of use are respectively 52.75%, 60.30%, 64.79% of the initial value. More importantly, as an oil-water separation and interfacial adsorption material, down fiber with a separation efficiency as high as 97.7% and dye removal efficiency are 88.70% (Methylene blue) and 88.39% (Rhodamine B). Therefore, this natural fiber can be used as a recyclable oil-water separation and adsorption material to protect water resources.

Development of a low-temperature-difference indirect-heating kinematic Stirling engine

Stirling engines can become a key component of distributed combined heat and power systems using renewable energy; however, their heat transfer surfaces suffer from overheating. To solve this, a low-temperature-difference indirect-heating kinematic Stirling engine employing a heat-transfer medium was developed. A new basic design method is devised by returning to the ideal Stirling cycle. The basic design of an engine optimized for temperature differences can be carried out using these criteria. To realize this basic design as an actual engine, an α+-type engine—the basic type suitable for low-temperature difference conditions—was developed. We developed a 10 kW-class engine using the basic design and type. Heat transfer oil was heated to 300 °C by burning wood biomass and circulated to the engine, which attained a maximum output of 14.3 kW, and a thermal efficiency of 15%. The engine was installed at the Minamisōma city community center and operates as a micro-combined heat and power system connected to the grid and independently during emergencies. The results show that the concept of the indirect heating low-temperature difference-type Stirling engine solves the main problem of its practical use, which can be used as a new distributed energy system.

Space Charge Measurements in Thin Bilayer BOPP Films by Thermal Pulse Method

In this paper, space charge accumulation in bilayer dielectrics composed of two metalized biaxially oriented polypropylene (BOPP) films thermally coupled by thin heat transfer oil (dibenzyltoluene, DBT) is investigated by thermal pulse method. An improved thermal pulse method for in-situ double-sided measurements is proposed to achieve higher spatial resolution. The accumulation and decay of the injected space charge is monitored after the laminated films being subjected to DC applied field of 150 V/μm at various temperatures from 25°C to 70 °C. Experimental results show that both charge injection rate and migration are sensitive to the operated temperature. Bipolar space charge injection is the rule, but negative charge becomes dominant as the injection rate asymmetry enhances with the elevated temperature. The interface between the films acts as a potential barrier to space charge transport at relative low temperature and the effect of the potential barrier appears weaken as the temperature rises. Therefore, the maximum electrical field by accumulated space charge is approximately 80 V/μm and the internal interface has little impact at 70°C.

Performance Study of Nanofluids TiO2/TermoXT 32 inside Double-Concentric Pipes Heat Exchanger using Twisted Tape Insertions

Nanotechnology offers a lot of opportunity in enhancing systems with one of those excellences is called “nanofluids”. This working fluid has higher thermal conductivity compared to that of conventional coolants. In this study, the “nanofluids”, consists of Titanium Dioxide nanoparticle and heavy-duty heat transfer oil called TermoXT 32, have been developed and observed to obtain the temperature characteristics inside the specific heat exchanger. The experiments were carried out on a test rig that constructed by a double-concentric tube with an inner pipe diameter of 38.1 mm for the inside tube and an inner diameter of 75.2 mm for the outer tube. The temperature of “nanofluids” was varied by the effect of twisted tape inserts. There are three twist ratio variations which are 7.35, 5.25, 4.72. The working fluid, “nanofluids”, was constantly flowed and maintained at a low temperature of 20°C. The flow rate was varied at 12 LPM; 16 LPM; and 20 LPM. The variation of “nanofluids” TiO2/TermoXT 32 was divided into two volume fraction variations of 0% (base fluid) and 0.3%. The results showed that the “nanofluids” temperature characteristics in the double-concentric tube heat exchanger have superior ability in term of heat transfer performance. Furthermore, these findings could be a great contribution to the application in an automotive radiator.

Multi-objective optimization of thermophysical properties of f\u2013Al2O3 nano-dispersions in heat transfer oil

Nanofluids are proven to be the next-generation smart fluids with tunable thermal and viscous properties. Nanomaterial concentration plays a vital role in determining the heat transfer and viscous transport characteristics. An optimum concentration is generally required to regulate a feasible and economical heat transfer operation. This research involves the modeling and optimizing different temperature-dependent thermal and viscous parameters for varying concentrations of nanofluids. The nanofluids consist of functionalized alumina (f–Al2O3) nano-dispersions in thermal oil (highly refined mineral oil). The experimentally measured temperature-dependent nanofluids' properties are used to optimize thermophysical parameters using Response Surface Methodology. Two case studies/scenarios are considered in the present research, where the primary objective is to maximize thermal conductivity for heat transfer applications and minimize nanoparticle loadings for economical operation. The input parameters include temperature and nanoparticle loadings. The output parameters or response include thermal conductivity, viscosity, density, and specific heat of nanofluids. For case study 1, the optimal findings for the thermal conductivity, viscosity, density, and specific heat are 0.146061 W/m °C, 0.031889 Pa.s, 838.529 kg/m3 and 1533.9 j/kg °C, respectively. For case study 2, the optimal findings for thermal conductivity, viscosity, density, and specific heat are 0.13476 W/m °C, 0.0226062 Pa.s, 831.071 kg/m3 and 1791.14 j/kg °C, respectively. Although the optimal value for thermal conductivity decreased in case study 2, the nanoparticle weight % was reduced from 1 to 0.322473%.

Preparation of thermal conductive anticorrosive composite coatings via synergistic effect of carbon nanofillers and heat transfer oil

Thermal conductivity of polymers gains much attention in many fields, and the formation of a heat conduction network is very important for polymer coatings. Carbon nanofiller is one type of excellent candidate fillers for improving thermal conductivity, but the poor incorporation between the filler and the polymer restricts coating performances. In this study, the heat transfer oil (HTO) was used as a medium to communicate the carbon nanofiller with the polymer (poly(vinylidene fluoride) (PVDF), fluorinated ethylene propylene (FEP)) and to improve the thermal conductivity and corrosion resistance of PVDF composite coatings. The micronanostructure of superhydrophobic PVDF/FEP/SiO2 (modified PVDF or m-PVDF) composite coatings was used as a storage space for the HTO, so that various carbon nanofiller including carbon nanotubes (CNTs), graphene, carbon black, and carbon nanofibers can take effect in improving thermal conductivity. Among the m-PVDF/carbon nanofiller composite coatings, the HTO/m-PVDF/CNTs coating gained the highest thermal conductivity of 0.53 W·m−1·K−1 after HTO modification, which was 3.3 times that of the m-PVDF/CNTs coating and was attributed to the connectivity of HTO. The anticorrosion of HTO/m-PVDF/CNTs was increased by 3 orders of magnitude than that of m-PVDF/CNTs owing to the synergistic effect between the HTO and CNTs in blocking the invasion of corrosive species. This research provides a unique way to design and fabricate high-thermal-conductivity composite coatings with high anticorrosion by the synergism between carbon nanofiller and HTO.