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61.
New experimental results on pressure loss for the single and two‐phase gas‐liquid flow with non‐Newtonian liquids in helical coils are reported. For a constant value of the curvature ratio, the value of the helix angle of the coils is varied from 2.56° to 9.37°. For single phase flow, the effect of helix angle on pressure loss is found to be negligible in laminar flow regime but pressure loss increases with the increasing value of helix angle in turbulent flow conditions. On the other hand, for the two‐phase flow, the well‐known Lockhart‐Martinelli method correlates the present results for all values of helix angle (2.56‐9.37°) satisfactorily under turbulent/laminar and turbulent/turbulent conditions over the following ranges of variables as: 0.57 ≤ n′ ≤ 1; Re′ < 4000; Rel < 4000; Reg < 8000; 8 ≤ x ≤ 1000 and 0.2 ≤ De′ ≤ 1000. 相似文献
62.
分析了纺丝侧吹风空调机组及送回风系统设计及其自动控制系统配置的节能措施。合理选择送风余压、送风量、送风温度、送风相对湿度等工艺参数以及空调机组的形式,正确利用回风和自动控制方式,加强生产运行管理,有利于节能。 相似文献
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64.
The nucleation and growth of CO2 bubbles in non-Newtonian and Newtonian fluids that were initially supersaturated under different pressures are investigated in the present work. Quantitative information by means of two cameras reveals that at an immobile nucleation site the bubble grows rapidly followed by a linear increase in bubble diameter with time. After reaching a critical size, the bubble detaches from the stagnant site to rise in liquids with an exponential temporary increase for both the diameter and distance. A simple physical reasoning was proposed to qualitatively explain these observed phenomena. Recently, the growth rate and flow fields around a CO2 micro-bubble were measured in a microdevice by a micro-Particle Image Velocimetry in water. This information at microscale gives new insight into the complex mechanism of bubble nucleation and growth in fluids and could help to develop a rigorous theoretical modelling and numerical simulation such as the Lattice Boltzmann approach. 相似文献
65.
The forced convective heat transfer characteristics for incompressible power-law fluids past a bundle of circular cylinders have been investigated numerically. The cylinder-to-cylinder hydrodynamic interactions have been approximated via a simple cell model. The momentum and energy equations have been solved using a finite difference based numerical method for a range of physical and kinematic conditions. The role of the two commonly used thermal boundary conditions, namely, constant temperature or constant heat flux, on heat transfer characteristics has also been studied. Extensive numerical results elucidating the effect of shear-thinning viscosity on the values of Nusselt number have been obtained for Peclet numbers ranging from 1 to 5000, Reynolds number in the range 1-500, flow behaviour index 1?n?0.5 and three values of voidages, namely, 0.4, 0.5 and 0.6, typical of tubular heat exchangers and tube banks. Under all conditions, varying levels of enhancement in Nusselt number are observed due to shear-thinning behaviour. The surface averaged Nusselt number shows strong dependence on the values of voidage, power-law index, Reynolds and Peclet numbers. The paper is concluded by presenting comparisons with the scant experimental results available in the literature. 相似文献
66.
J. Popplewell 《Chemical Engineering Communications》1988,67(1):243-257
Magnetic measurements on ferrofluids can be used to determine the magnetic concentration which may be as large as 15% by volume in a very viscous fluid. Additional information on the particle size distribution parameters and the mode of magnetisation can be obtained from an analysis of the magnetisation curve. Magnetic studies are also invaluable for a correct interpretation of the magnetic dichroism, birefringence and small angle neutron scattering (SANS) data. Measurements on a ferrofluid after freezing enables the shape anisotropy to be determined and the degree of particle elongation (∼15%) calculated. 相似文献
67.
The electrodiffusion technique was performed in order to investigate the shear rate on a scraped surface heat exchanger. Microelectrodes were placed inside: the walls of the outer cylinder; the inlet and outlet bowls; the rotor and the blades. Highly viscous Newtonian fluid (Emkarox HV45 solutions) and non-Newtonian model fluid (aqueous solutions of CMC) were used. The electrodiffusion method allowed us to measure wall shear rates. Maximum shear rate was observed at the scraping surface and caused by blades scraping, high shear rate was also measured on the leading edge of the blades. In the other parts of the exchanger, shear rate remained low but the development of Taylor vortices completely modified the scraped surface heat exchangers behaviour inside the surface of the bowls. A dimensionless representation of the friction factor was established for the inner and outer wall surface of the exchanger. 相似文献
68.
The ideal thermodynamic performances of a variety of non-CFC refrigerants and their mixtures were calculated by using the Patel-Teja equation of state. The results indicated that the preferable non-CFC refrigerant mixtures could be HCFC-I24 +HFC-152a, HFC-152a + HFC-134, dimethyl ether + HCFC-22, and dimethyl ether + HCFC-124 for air-conditioning systems, and binary mixtures of HCFC-22 + HFC-125, and HCFC-22 + HFC-143a for low-temperature applications. Those potential non-CFC mixtures were suggested for further investigations. 相似文献
69.
70.