Turbulent flow characteristics and heat transfer applications of a twisted heat exchanger with 3-lobed cross section along with Y-tape insert are numerically studied. The working fluids for the simulations are pure water and water–Al2O3 nanofluid using two-phase mixture model. The study is carried out for various nanofluid volume fractions of 0.01, 0.02 and 0.03 with Reynolds number in the range of 5000–20,000. The effect of nanoparticles in heat transfer augmentation for smooth and lobed tubes is discussed based on presenting the highest thermal performance, which is a relation between heat transfer rate and pressure loss. Results show that implementing the twisted tube with Y-tape insert enhances the heat transfer more than the twisted tube. Relative Nusselt numbers for twisted tubes decrease with Reynolds number in comparison with the plain tube. Turbulent intensity, swirl number and tangential velocity of twisted tube with insert are higher than empty twisted tube indicating that inserting the Y-tape intensifies the turbulence and disturbs the fluid flow further. On the other hand, although the twisted tube increases the pressure drop more than plain tube, the case with Y-tape drastically increases the friction factor. So, the thermal performance of twisted tube with insert is lower than empty twisted tube. Adding nanoparticles to the base fluid has different influence on the investigated cases. It augments the relative Nusselt number inside plain tube and empty twisted tube with slight increment in friction factor. Increasing the nanoparticles concentration enhances the heat transfer rates for these cases while it does not increase the relative Nusselt number inside twisted tube with Y-tape insert at high Reynolds number and nanoparticle concentration. Moreover, it can be found that twisted tube with or without Y-tape insert is more efficient at low Reynolds number in comparison with the plain tube.
相似文献 |
|||||||
|
|||||||
|
排序方式： 共有168条查询结果，搜索用时 0 毫秒
41.
This paper presents numerical investigations on melting of phase change material using N-eicosane inside a cylindrical container. Numerical simulations are performed for symmetric melting of phase change material between two cylinders in concentric and eccentric arrays using the FLUENT software which is sub-cooled initially to 1 °C. Inner cylindrical tube is considered hot wall while outer tube is insulated. Predicted result shows that melting rate is the same approximately for concentric and eccentric array before time of 15 min. After this time, melting rate decreases in concentric array. It is due to the pure conduction between hot tube and cold solid phase change material. 相似文献
42.
Omidi Mohamad Rabienataj Darzi A. Ali Farhadi Mousa 《Journal of Thermal Analysis and Calorimetry》2019,137(4):1451-1462
43.
A new solid-phase microextraction fiber based on alumina/titania sol-gel-coated on copper wire for headspace sampling of chlorinated organic solvents (chloroform, carbon tetrachloride, trichloroethene, and tetrachloroethene) from urine samples is introduced. The influences of fiber coating composition and microextraction conditions (extraction temperature, extraction time, and ionic strength of the sample matrix) on the fiber performance were investigated. Also, the influence of temperature and time on desorption of analytes from fiber was studied. The proposed fiber has high capacity and demonstrates fast sampling of chlorinated organic solvents from urine samples with high sensitivity. The relative standard deviation (RSD, n=5) for all analytes was below 6.5%. 相似文献
44.
A hollow fiber liquid-phase microextraction technique coupled with high-performance liquid chromatography with fluorescence detection was employed for determination and evaluation of the binding characteristics of drugs to bovine serum albumin (BSA). Enantiomers of guaifenesin (an expectorant drug) were investigated as a model system. After optimization of some influencing parameters on microextraction, the proposed method was used for calculation of the target drug distribution coefficient between n-octanol and the buffer solution as well as study of drug-BSA binding in physiological conditions. The developed method shows a new, improved and simple procedure for determination of free drug concentration in biological fluids and the extent of drug-protein binding. 相似文献
45.
Golshan Mazloom Fatola Farhadi Farhad Khorasheh 《Journal of Analytical and Applied Pyrolysis》2009,84(2):157-164
The disposal of used tires is a major environmental problem. With increasing interest on recovery of wastes, pyrolysis is considered as an alternative process for recovering some of the value in scrap tires. An accurate kinetic model is required to predict product yields during thermal or catalytic pyrolysis of scrap tires. Pyrolysis products contain a variety of hydrocarbons over a wide boiling range. A common approach for kinetic modeling of such complex systems is lumping where each lump is defined by a boiling point range. Available experimental data for thermal and catalytic pyrolysis of scrap tires from the literature were used to evaluate two types of lumping models; discrete and continuous lumping models. The lumps were described in terms of the boiling point distribution of the reactant mixture. In the discrete model, the conversion of heavier to lighter lumps was described in terms of series and parallel first order reactions. In the continuous model, the normalized boiling point was used to describe the reactant mixture as a continuous mixture. An optimization procedure was implemented for estimation of the model parameters using experimental data reported in the literature. Model predictions with indicated that although the discrete model could reasonably predict the yields of different cuts in the products, predictions of the continuous model were very good, especially in thermal pyrolysis. 相似文献
46.
A wide variety of aldehydes were efficiently converted to their corresponding carboxylic acids in high yields using H2O2/HCl in the presence of hydroxylamine hydrochloride. In addition, selective oxidation of aldehydes in the presence of other functional groups such as hydroxyl group, carbon‐carbon double bond and other heteroatoms can be considered a noteworthy advantage of this method. 相似文献
47.
A kinetic method for the accurate and sensitive determination of metronidazole benzoate (MB) has been described. The method is based on the oxidation of MB with KMnO4 in alkaline medium in the presence of sodium dodecyl sulphate (SDS). At a fixed time of 10 min, the formed magnate ion is spectrophotometrically measured at 610 nm. The determination of MB by the fixed‐concentration and rate constant method is feasible with the calibration equation obtained, but the fixed‐time method proves to be more applicable. The proposed method was successfully used for the quantitative determination of MB in suspended oral syrup after the separation of MB with a simple separation method. Beer's law was obeyed from 0.55 mgL?1 to 33 mgL?1 and the RSD% value for syrup was 3.44. The results obtained agreed with those obtained by the BP method. 相似文献
48.
A one‐pot synthesis of 2,4,5‐trisubstituted imidazoles from 1,2‐diketone or α‐hydroxy ketone, aldehyde and ammonium heptamolybdate tetrahydrate in an inexpensive and readily available ionic liquid, tetrabutylammonium iodide (TBAI) in molten state using catalytic amounts of p‐TSA has been described. 相似文献
49.
The electrooxidation of hyoscine N‐butylbromide (HBB) was investigated by rotating disk electrode voltammetry, cyclic voltammetry and controlled potential coulometry in 0.1 M HNO3 and in 0.1 M tetrabutylammonium perchlorate (TBAP) solutions of acetonitrile at a platinum (Pt) electrode. Based on the results obtained, it is suggested that a bromide ion of HBB was oxidized in one reversible step in aqueous solutions and in two reversible steps in acetonitrile. A differential pulse voltammetric (DPV) method at a Pt electrode was developed for the determination of HBB in the concentration range of 1.0 × 10?6‐1.0 × 10?3 M. The procedure was applied to the determination of HBB in its formulations as well as its recovery from blood serum and urine samples. 相似文献
50.
|
| 设为首页 | 免责声明 | 关于勤云 | 加入收藏 |
|
Copyright©北京勤云科技发展有限公司 京ICP备09084417号 |