Variant graphene,graphene oxides(GO),and graphene nanoplatelets(GNP)dispersed in blood-based copper(Cu)nanoliquids over a leaning permeable cylinder are the focus of this study.These forms of graphene are highly benef...Variant graphene,graphene oxides(GO),and graphene nanoplatelets(GNP)dispersed in blood-based copper(Cu)nanoliquids over a leaning permeable cylinder are the focus of this study.These forms of graphene are highly beneficial in the biological and medical fields for cancer therapy,anti-infection measures,and drug delivery.The non-Newtonian Sutterby(blood-based)hybrid nanoliquid flows are generalized within the context of the Tiwari-Das model to simulate the effects of radiation and heating sources.The governing partial differential equations are reformulated into a nonlinear set of ordinary differential equations using similar transformational expressions.These equations are then transformed into boundary value problems through a shooting technique,followed by the implementation of the bvp4c tool in MATLAB.The influences of various parameters on the model’s nondimensional velocity and temperature profiles,reduced skin friction,and reduced Nusselt number are presented for detailed discussions.The results indicated that Cu-GNP/blood and Cu-GO/blood hybrid nanofluids exhibit the lowest and highest velocity distributions,respectively,for increased nanoparticles volume fraction,curvature parameter,Sutterby fluid parameter,Hartmann number,and wall permeability parameter.Conversely,opposite trends are observed for the temperature distribution for all considered parameters,except the mixed convection parameter.Increases in the reduced skin friction magnitude and the reduced Nusselt number with higher values of graphene/GO/GNP nanoparticle volume fraction are also reported.Finally,GNP is identified as the superior heat conductor,with an average increase of approximately 5%and a peak of 7.8%in the reduced Nusselt number compared to graphene and GO nanoparticles in the Cu/blood nanofluids.展开更多
Graphene has superhigh thermal conductivity up to 5000 W/(m·K),extremely thin thickness,superhigh mechanical strength and nano-lamellar structure with low interlayer shear strength,making it possess great potenti...Graphene has superhigh thermal conductivity up to 5000 W/(m·K),extremely thin thickness,superhigh mechanical strength and nano-lamellar structure with low interlayer shear strength,making it possess great potential in mini-mum quantity lubrication(MQL)grinding.Meanwhile,ionic liquids(ILs)have higher thermal conductivity and better thermal stability than vegetable oils,which are frequently used as MQL grinding fluids.And ILs have extremely low vapor pressure,thereby avoiding film boiling in grinding.These excellent properties make ILs also have immense potential in MQL grinding.However,the grinding performance of graphene and ionic liquid mixed fluid under nano-fluid minimum quantity lubrication(NMQL),and its tribological mechanism on abrasive grain/workpiece grinding interface,are still unclear.This research firstly evaluates the grinding performance of graphene and ionic liquid mixed nanofluids(graphene/IL nanofluids)under NMQL experimentally.The evaluation shows that graphene/IL nanofluids can further strengthen both the cooling and lubricating performances compared with MQL grinding using ILs only.The specific grinding energy and grinding force ratio can be reduced by over 40%at grinding depth of 10μm.Work-piece machined surface roughness can be decreased by over 10%,and grinding temperature can be lowered over 50℃at grinding depth of 30μm.Aiming at the unclear tribological mechanism of graphene/IL nanofluids,molecular dynamics simulations for abrasive grain/workpiece grinding interface are performed to explore the formation mechanism of physical adsorption film.The simulations show that the grinding interface is in a boundary lubrication state.IL molecules absorb in groove-like fractures on grain wear flat face to form boundary lubrication film,and graphene nanosheets can enter into the grinding interface to further decrease the contact area between abrasive grain and workpiece.Compared with MQL grinding,the average tangential grinding force of graphene/IL nanofluids can decrease up to 10.8%.The interlayer shear effect and low interlayer shear strength of graphene nanosheets are the principal causes of enhanced lubricating performance on the grinding interface.EDS and XPS analyses are further carried out to explore the formation mechanism of chemical reaction film.The analyses show that IL base fluid happens chemical reactions with workpiece material,producing FeF_(2),CrF_(3),and BN.The fresh machined surface of workpiece is oxidized by air,producing NiO,Cr_(2)O_(3) and Fe_(2)O_(3).The chemical reaction film is constituted by fluorides,nitrides and oxides together.The combined action of physical adsorption film and chemical reaction film make graphene/IL nano-fluids obtain excellent grinding performance.展开更多
A novel graphene oxide/titanium dioxide(GO/TiO2) solvent-free nanofluid was firstly synthesized by employing GO, which was in-situ deposited by TiO2 as the core and(3-Glycidyloxypropyl) trime thoxysilane(KH560) ...A novel graphene oxide/titanium dioxide(GO/TiO2) solvent-free nanofluid was firstly synthesized by employing GO, which was in-situ deposited by TiO2 as the core and(3-Glycidyloxypropyl) trime thoxysilane(KH560) and polyetheramine-M2070 as the shell. The morphology and structure of GO/TiO2 nanofluid were verified by Transmission electron microscopy(TEM), X-ray diffraction(XRD) analysis, Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS) and UV-vis absorption spectra. These studies confirmed that TiO2 has been deposited onto GO with good dispersion, and the organic shell has been grafted onto the core successfully. Thermo gravimetric analysis(TGA) and viscosity analysis indicated that this nanoparticle hybrid material presented a liquid state without solvent at room temperature, and has great fluidity and thermal stability. The solubility investigation of GO/TiO2 nanofluid revealed its excellent amphiphilicity and the potential as the functional nanocomposites.展开更多
Improvement of the heat transfer effect of cold side of a thermoelectric generator(TEG) is one of the approaches to enhance the performance of the TEG systems.As a new type of heat transfer media,nanofluids can enhanc...Improvement of the heat transfer effect of cold side of a thermoelectric generator(TEG) is one of the approaches to enhance the performance of the TEG systems.As a new type of heat transfer media,nanofluids can enhance the heat transfer performance of working liquid significantly.In this study,the performance of a commercial TEG with graphene-water(GW) nanofluid as coolants in a minichannel heat exchanger is investigated experimentally at low temperatures.The results show that the output power of TEG increases with the flow rate under 950 mL/min.However,the fluid flow rate has no influence on the output power of TEG with higher flow rate(larger than 950 mL/min) when the heat transfer dynamic balance state of the system is reached.The optimal concentration and flow rate of nanofluid are 0.1 wt%and 950 mL/min,respectively.At the optimal conditions,the improved voltage,output power and conversion efficiency with GW nanofluid applied in the cooling system are increased by11.29%,21.55%and 3.5%in comparison with those with only water applied,respectively.展开更多
Addition of graphene nanoplatelet(GNP)into water is a promising method for improving cold storage system performance,and its application requires comprehensive understanding of solidification behavior of GNP-water nan...Addition of graphene nanoplatelet(GNP)into water is a promising method for improving cold storage system performance,and its application requires comprehensive understanding of solidification behavior of GNP-water nanofluid.In the present study,the influences of GNP mass concentration,cold storage cavity size and shape on solid-liquid interface evolution,temperature distribution,streamline profile as well as solidification rate are numerically analyzed.The enthalpy-porosity technique is adopted to track solid-liquid interface.The results show that the enhancement effect of GNPs on solidification is mainly reflected in the final stage in which heat conduction is predominant;the solidification occurs at the bottom of cavity in the early stage,and the solid-liquid interface is similar to the shape of cavity itself and then tends to be circular in the middle and final stages respectively;the reduction degree of solidification time reaches 30.1%at GNP mass concentration of 1.2 wt%under present simulation conditions;decreasing cavity size and adopting triangular cavity are beneficial for promoting the solidification,but they will suppress the enhancement effect of GNPs on solidification.展开更多
基金funded by the Ministry of Higher Education,Malaysia,through the Research Fund of Fundamental Research Grant Scheme (FRGS/1/2020/STG06/UM/02/1:FP009-2020).
文摘Variant graphene,graphene oxides(GO),and graphene nanoplatelets(GNP)dispersed in blood-based copper(Cu)nanoliquids over a leaning permeable cylinder are the focus of this study.These forms of graphene are highly beneficial in the biological and medical fields for cancer therapy,anti-infection measures,and drug delivery.The non-Newtonian Sutterby(blood-based)hybrid nanoliquid flows are generalized within the context of the Tiwari-Das model to simulate the effects of radiation and heating sources.The governing partial differential equations are reformulated into a nonlinear set of ordinary differential equations using similar transformational expressions.These equations are then transformed into boundary value problems through a shooting technique,followed by the implementation of the bvp4c tool in MATLAB.The influences of various parameters on the model’s nondimensional velocity and temperature profiles,reduced skin friction,and reduced Nusselt number are presented for detailed discussions.The results indicated that Cu-GNP/blood and Cu-GO/blood hybrid nanofluids exhibit the lowest and highest velocity distributions,respectively,for increased nanoparticles volume fraction,curvature parameter,Sutterby fluid parameter,Hartmann number,and wall permeability parameter.Conversely,opposite trends are observed for the temperature distribution for all considered parameters,except the mixed convection parameter.Increases in the reduced skin friction magnitude and the reduced Nusselt number with higher values of graphene/GO/GNP nanoparticle volume fraction are also reported.Finally,GNP is identified as the superior heat conductor,with an average increase of approximately 5%and a peak of 7.8%in the reduced Nusselt number compared to graphene and GO nanoparticles in the Cu/blood nanofluids.
基金Supported by Shandong Provincial Natural Science Foundation of China(Grant Nos.ZR2022ME208,ZR2020QE181)National Natural Science Foundation of China(Grant Nos.51705272,52005281)+1 种基金China Postdoctoral Science Foundation(Grant No.2018M642628)111 project(Grant No.D21017).
文摘Graphene has superhigh thermal conductivity up to 5000 W/(m·K),extremely thin thickness,superhigh mechanical strength and nano-lamellar structure with low interlayer shear strength,making it possess great potential in mini-mum quantity lubrication(MQL)grinding.Meanwhile,ionic liquids(ILs)have higher thermal conductivity and better thermal stability than vegetable oils,which are frequently used as MQL grinding fluids.And ILs have extremely low vapor pressure,thereby avoiding film boiling in grinding.These excellent properties make ILs also have immense potential in MQL grinding.However,the grinding performance of graphene and ionic liquid mixed fluid under nano-fluid minimum quantity lubrication(NMQL),and its tribological mechanism on abrasive grain/workpiece grinding interface,are still unclear.This research firstly evaluates the grinding performance of graphene and ionic liquid mixed nanofluids(graphene/IL nanofluids)under NMQL experimentally.The evaluation shows that graphene/IL nanofluids can further strengthen both the cooling and lubricating performances compared with MQL grinding using ILs only.The specific grinding energy and grinding force ratio can be reduced by over 40%at grinding depth of 10μm.Work-piece machined surface roughness can be decreased by over 10%,and grinding temperature can be lowered over 50℃at grinding depth of 30μm.Aiming at the unclear tribological mechanism of graphene/IL nanofluids,molecular dynamics simulations for abrasive grain/workpiece grinding interface are performed to explore the formation mechanism of physical adsorption film.The simulations show that the grinding interface is in a boundary lubrication state.IL molecules absorb in groove-like fractures on grain wear flat face to form boundary lubrication film,and graphene nanosheets can enter into the grinding interface to further decrease the contact area between abrasive grain and workpiece.Compared with MQL grinding,the average tangential grinding force of graphene/IL nanofluids can decrease up to 10.8%.The interlayer shear effect and low interlayer shear strength of graphene nanosheets are the principal causes of enhanced lubricating performance on the grinding interface.EDS and XPS analyses are further carried out to explore the formation mechanism of chemical reaction film.The analyses show that IL base fluid happens chemical reactions with workpiece material,producing FeF_(2),CrF_(3),and BN.The fresh machined surface of workpiece is oxidized by air,producing NiO,Cr_(2)O_(3) and Fe_(2)O_(3).The chemical reaction film is constituted by fluorides,nitrides and oxides together.The combined action of physical adsorption film and chemical reaction film make graphene/IL nano-fluids obtain excellent grinding performance.
基金supported by the National Natural Science Foundation of China(51373137)the International cooperation project of Shaanxi Province(2016KW-053)the Natural Science Basic Research Plan in Shaanxi(2017JQ2002)
文摘A novel graphene oxide/titanium dioxide(GO/TiO2) solvent-free nanofluid was firstly synthesized by employing GO, which was in-situ deposited by TiO2 as the core and(3-Glycidyloxypropyl) trime thoxysilane(KH560) and polyetheramine-M2070 as the shell. The morphology and structure of GO/TiO2 nanofluid were verified by Transmission electron microscopy(TEM), X-ray diffraction(XRD) analysis, Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS) and UV-vis absorption spectra. These studies confirmed that TiO2 has been deposited onto GO with good dispersion, and the organic shell has been grafted onto the core successfully. Thermo gravimetric analysis(TGA) and viscosity analysis indicated that this nanoparticle hybrid material presented a liquid state without solvent at room temperature, and has great fluidity and thermal stability. The solubility investigation of GO/TiO2 nanofluid revealed its excellent amphiphilicity and the potential as the functional nanocomposites.
基金supported by the National Natural Science Foundation of China(Grant Nos.51590902&51476095)the Natural Science Foundation of Shanghai(Grant No.14ZR1417000)+1 种基金the Key Subject of Shanghai Polytechnic University(Material Science and Engineering,Grant No.XXKZD1601)the Program for Professor of Special Appointment(Young Eastern Scholar,Grant No.QD2015052)at Shanghai Institutions of Higher Learning
文摘Improvement of the heat transfer effect of cold side of a thermoelectric generator(TEG) is one of the approaches to enhance the performance of the TEG systems.As a new type of heat transfer media,nanofluids can enhance the heat transfer performance of working liquid significantly.In this study,the performance of a commercial TEG with graphene-water(GW) nanofluid as coolants in a minichannel heat exchanger is investigated experimentally at low temperatures.The results show that the output power of TEG increases with the flow rate under 950 mL/min.However,the fluid flow rate has no influence on the output power of TEG with higher flow rate(larger than 950 mL/min) when the heat transfer dynamic balance state of the system is reached.The optimal concentration and flow rate of nanofluid are 0.1 wt%and 950 mL/min,respectively.At the optimal conditions,the improved voltage,output power and conversion efficiency with GW nanofluid applied in the cooling system are increased by11.29%,21.55%and 3.5%in comparison with those with only water applied,respectively.
基金Project(19242197218/2020/AR1) supported by Anna Centenary Research Fellowship provided by the Center for Research, Anna University, Chennai, Tamilnadu, India。
基金National Natural Science Foundation of China Civil Aviation Joint Fund(U1933121)the Natural Science Foundation of Shanghai(Grant No.19ZR1422300)。
文摘Addition of graphene nanoplatelet(GNP)into water is a promising method for improving cold storage system performance,and its application requires comprehensive understanding of solidification behavior of GNP-water nanofluid.In the present study,the influences of GNP mass concentration,cold storage cavity size and shape on solid-liquid interface evolution,temperature distribution,streamline profile as well as solidification rate are numerically analyzed.The enthalpy-porosity technique is adopted to track solid-liquid interface.The results show that the enhancement effect of GNPs on solidification is mainly reflected in the final stage in which heat conduction is predominant;the solidification occurs at the bottom of cavity in the early stage,and the solid-liquid interface is similar to the shape of cavity itself and then tends to be circular in the middle and final stages respectively;the reduction degree of solidification time reaches 30.1%at GNP mass concentration of 1.2 wt%under present simulation conditions;decreasing cavity size and adopting triangular cavity are beneficial for promoting the solidification,but they will suppress the enhancement effect of GNPs on solidification.