To examine and investigate the impact of nanofluid on heat exchanger performance,including the total heat transfer,the effect of friction factor,the average Nusselt number,and the thermal efficiency,the output heat tr...To examine and investigate the impact of nanofluid on heat exchanger performance,including the total heat transfer,the effect of friction factor,the average Nusselt number,and the thermal efficiency,the output heat transfers of a shell and tube heat exchanger using ZnO nanoparticles suspended in water has been conducted numerically.The governing equations were solved using finite volume techniques and CFD simulations with ANSYS/FLUENT Solver 2021.The nanoparticles volume fractions adopted are 0.2%and 0.35%that used in numerical computations under 200 to 1400 Reynolds numbers range.The increasing of temperature is approximately 13%from the bottom to the top of heat exchanger,while the maximum enhancement of Nusselt number is about 10%,19%for volume fractions 0.2%and 0.35%respectively.The elevated values of the friction factor at the volumetric ratios of 0.2%and 0.35%are 0.25%and 0.47%respectively.The findings demonstrate that the performance efficiency of shell and tube heat exchanger is enhanced due to the increase in Nusselt number.展开更多
The entropy analysis of viscoelastic fluid obeying the simplified Phan-ThienTanner(SPTT)model with variable thermophysical properties are obtained for laminar,steady state and fully developed Couette-Poiseuille flow.T...The entropy analysis of viscoelastic fluid obeying the simplified Phan-ThienTanner(SPTT)model with variable thermophysical properties are obtained for laminar,steady state and fully developed Couette-Poiseuille flow.The homotopy perturbation method(HPM)allows us to solve nonlinear momentum and energy differential equations.The Reynold’s model is used to describe the temperature dependency of thermophysical properties.Results indicate that the increase of the group parameter(Br=U)and the Brinkman number(Br)which show the power of viscous dissipation effect;increases the entropy generation while increasing fluid elasticity(εDe2)decreases the generated entropy.Increasing the Reynolds variational parameter(a)which control the level of temperature dependence of physical properties attenuate entropy generation when moving plate and applied pressure gradient have the opposite direction and decreases entropy generation when moving plate and applied pressure gradient have the same direction or both plates are at rest.Also,increasing elasticity reduces the difference between variable and constant thermophysical properties cases.These results may give guidelines for cost optimization in industrial processes.展开更多
Vortex methods are frequently used for the numerical simulation of incompressible flow, especially for the flow with high Reynold’s number. Three dimensional vortex methods are a kind of large-scale computation, whic...Vortex methods are frequently used for the numerical simulation of incompressible flow, especially for the flow with high Reynold’s number. Three dimensional vortex methods are a kind of large-scale computation, which can be further divided into some different approaches. However, whatever approach is applied, one step to determine the velocity field from the vorticity field is necessary, which is often carried out by展开更多
采用大涡模拟和Ffocws-Williams and Hawkings(FW-H)数值模型预测方法,在雷诺数为1.6×10^(5)条件下研究常用和专用垂直轴风力机翼型的单音噪声特性和流场特征.结果表明:翼型单音噪声特征与压力面尾缘处的压力波动关系密切,压力波...采用大涡模拟和Ffocws-Williams and Hawkings(FW-H)数值模型预测方法,在雷诺数为1.6×10^(5)条件下研究常用和专用垂直轴风力机翼型的单音噪声特性和流场特征.结果表明:翼型单音噪声特征与压力面尾缘处的压力波动关系密切,压力波动频率越大,单音噪声特征越明显;在相同条件下,对称翼型表面压力功率谱密度要高于非对称翼型的功率谱密度,噪声声压级也相对较大;翼型最大相对厚度对压力波动功率谱密度有重要影响,相对厚度越大,表面压力功率谱密度越低,翼型越薄单音噪声特征越明显;翼型最大相对弯度影响单音噪声对应的频率位置,最大相对弯度的位置越靠近尾缘,单音噪声对应的主频率越低.展开更多
Numerical solutions are obtained for non-steady, incompressible fluid flow between two parallel disks which at time t are separated by a distance H(1-αt)1/2 and a magnetic field proportional to B0(1-αt) -1/2 is appl...Numerical solutions are obtained for non-steady, incompressible fluid flow between two parallel disks which at time t are separated by a distance H(1-αt)1/2 and a magnetic field proportional to B0(1-αt) -1/2 is applied perpendicular to the disks where H denotes a representative length, BO denotes a representative magnetic field and α-1 denotes a representative time. Similarity transformations are used to convert the governing partial differential equations of motion in to ordinary differential form. The resulting ordinary differential equations are solved numerically using SOR method, Richardson extrapolation and Simpson’s (1/3) Rule. Our numerical scheme is straightforward, efficient and easy to program.展开更多
文摘To examine and investigate the impact of nanofluid on heat exchanger performance,including the total heat transfer,the effect of friction factor,the average Nusselt number,and the thermal efficiency,the output heat transfers of a shell and tube heat exchanger using ZnO nanoparticles suspended in water has been conducted numerically.The governing equations were solved using finite volume techniques and CFD simulations with ANSYS/FLUENT Solver 2021.The nanoparticles volume fractions adopted are 0.2%and 0.35%that used in numerical computations under 200 to 1400 Reynolds numbers range.The increasing of temperature is approximately 13%from the bottom to the top of heat exchanger,while the maximum enhancement of Nusselt number is about 10%,19%for volume fractions 0.2%and 0.35%respectively.The elevated values of the friction factor at the volumetric ratios of 0.2%and 0.35%are 0.25%and 0.47%respectively.The findings demonstrate that the performance efficiency of shell and tube heat exchanger is enhanced due to the increase in Nusselt number.
文摘The entropy analysis of viscoelastic fluid obeying the simplified Phan-ThienTanner(SPTT)model with variable thermophysical properties are obtained for laminar,steady state and fully developed Couette-Poiseuille flow.The homotopy perturbation method(HPM)allows us to solve nonlinear momentum and energy differential equations.The Reynold’s model is used to describe the temperature dependency of thermophysical properties.Results indicate that the increase of the group parameter(Br=U)and the Brinkman number(Br)which show the power of viscous dissipation effect;increases the entropy generation while increasing fluid elasticity(εDe2)decreases the generated entropy.Increasing the Reynolds variational parameter(a)which control the level of temperature dependence of physical properties attenuate entropy generation when moving plate and applied pressure gradient have the opposite direction and decreases entropy generation when moving plate and applied pressure gradient have the same direction or both plates are at rest.Also,increasing elasticity reduces the difference between variable and constant thermophysical properties cases.These results may give guidelines for cost optimization in industrial processes.
基金Project supported by the National Natural Science Foundation of China
文摘Vortex methods are frequently used for the numerical simulation of incompressible flow, especially for the flow with high Reynold’s number. Three dimensional vortex methods are a kind of large-scale computation, which can be further divided into some different approaches. However, whatever approach is applied, one step to determine the velocity field from the vorticity field is necessary, which is often carried out by
文摘采用大涡模拟和Ffocws-Williams and Hawkings(FW-H)数值模型预测方法,在雷诺数为1.6×10^(5)条件下研究常用和专用垂直轴风力机翼型的单音噪声特性和流场特征.结果表明:翼型单音噪声特征与压力面尾缘处的压力波动关系密切,压力波动频率越大,单音噪声特征越明显;在相同条件下,对称翼型表面压力功率谱密度要高于非对称翼型的功率谱密度,噪声声压级也相对较大;翼型最大相对厚度对压力波动功率谱密度有重要影响,相对厚度越大,表面压力功率谱密度越低,翼型越薄单音噪声特征越明显;翼型最大相对弯度影响单音噪声对应的频率位置,最大相对弯度的位置越靠近尾缘,单音噪声对应的主频率越低.
文摘Numerical solutions are obtained for non-steady, incompressible fluid flow between two parallel disks which at time t are separated by a distance H(1-αt)1/2 and a magnetic field proportional to B0(1-αt) -1/2 is applied perpendicular to the disks where H denotes a representative length, BO denotes a representative magnetic field and α-1 denotes a representative time. Similarity transformations are used to convert the governing partial differential equations of motion in to ordinary differential form. The resulting ordinary differential equations are solved numerically using SOR method, Richardson extrapolation and Simpson’s (1/3) Rule. Our numerical scheme is straightforward, efficient and easy to program.
