共查询到19条相似文献,搜索用时 70 毫秒
1.
2.
3.
4.
5.
从螺旋正交坐标系下的Navier-Stockd方程组出发,利用realizable k-ε湍流模型和SIMPLEC算法,对直管和多种不同几何尺寸的螺旋管内的流动进行了数值模拟,研究了螺旋管的扭率τ、管径与曲率半径比r/Rc、入口速度vi以及流体粘度对螺旋管内迪恩涡的影响.模拟结果表明:扭率和曲率比的变化会引起螺旋管内轴向速度、径向速度最大值的偏移和速度大小的变化;径向速度和全压在入口速度低于约0.8 m/s时随入口速度递增:流体粘度的提高引起径向速度和全压的增大,并有利于迪恩涡旋的形成. 相似文献
6.
为了探讨糖厂的烟气水膜除尘耦合换热技术实施的可行性,建立了带水膜湿烟气与空气之间的换热实验装置,进行带水膜湿烟气的对流传热实验研究。在该换热装置中,烟气在矩形通道中流动并喷入雾化热水,通过换热面加热另一侧的空气,同时,在烟气侧通道安装波纹板强化单元,以强化热质传递。实验确定最佳液气比,通过改变波纹板峰高、波纹段高、段数及烟气流速,研究带水膜饱和烟气的对流传热系数。结果表明:饱和烟气对空气的换热量显著;最佳液气比为3.3~4.2 L/m~3;烟气流速和波纹板添加段数的增加显著增大对流传热系数。回归了最佳液气比下的传热准则关联式。 相似文献
7.
8.
文章介绍了工业锅炉和其它换热设备中对流受热面传热强化的发展及西安交通大学动力工程多相流国家重点实验室在传热强化方面的研究进展。 相似文献
9.
10.
纵向涡发生器强化传热管的实验研究 总被引:3,自引:0,他引:3
介绍了一种高效强化传热管,沿传热管内壁轴向均匀排布三列成对的纵向涡发生器,在常壁温条件下进行加热空气在管内流动的冷却实验,研究强化传热管的传热和阻力特性。结果表明,在过渡流区管内置纵向涡发生器的强化传热大大增强,Nu增大为光管的2.02.3倍,阻力损失也相应有所增加,提出一种比较优化的发生器的形状设计,探讨了传热和阻力随设置间距变化的规律。 相似文献
11.
Bogdan I. Pavel 《International Journal of Heat and Mass Transfer》2004,47(23):4939-4952
The present experimental and numerical work investigates the effect of metallic porous materials, inserted in a pipe, on the rate of heat transfer. The pipe is subjected to a constant and uniform heat flux. The effects of porosity, porous material diameter and thermal conductivity as well as Reynolds number on the heat transfer rate and pressure drop are investigated. The results are compared with the clear flow case where no porous material was used. The results obtained lead to the conclusion that higher heat transfer rates can be achieved using porous inserts at the expense of a reasonable pressure drop. Also, it is shown that for an accurate simulation of heat transfer when a porous insert is employed its effective thermal conductivity should be carefully evaluated. 相似文献
12.
This paper focuses on the study of heat transfer enhancement in natural vertical convection by using delta‐winglet longitudinal vortex generators. In the experimental range of Rayleigh numbers, the effect of attack angle, height, and width of the winglet of longitudinal vortex generator (LVG) on heat transfer performance was experimentally investigated. The results showed that there was an optimal attack angle and that the height and width can affect the heat transfer. In terms of array performance, it was shown that initial arrays could enhance the performance of later arrays. Moreover, the effects of LVG and low rectangular fins were compared. The results showed that the effect of LVGs was greater than that of low rectangular fins. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(6): 402–409, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20126 相似文献
13.
A pulsating flow in a pipe was experimentally investigated to determine the effect of pulsation on the rate of heat transfer. The influence of hydrodynamic parameters and characteristics of the pulsation on heat transfer was carefully studied. In order to adjust the pulsating parameters, a self‐oscillator was designed so the length of the resonator and the length of the outlet nozzle could be adjusted. The results show that the heat transfer rate is strongly affected by both the hydrodynamic parameters and the configuration of the resonator. With the increase of the flow rate of the liquid and the length of the chamber, heat transfer is enhanced. There is an optimal length at which the heat transfer enhancement attends to the best. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 279–286, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20020 相似文献
14.
Detailed heat transfer measurements were performed by using 178 thermocouples in a channel with pin fin array. Local heat transfer coefficients and local heat transfer enhancement coefficients were obtained for eight Reynolds numbers ranging from 2000 to 100,000 on the endwall of the channel. The endwall boundary conditions for heat transfer investigation are heating the bottom endwall and heating symmetrically the bottom and top endwalls with constant heat flux. The mechanism of heat transfer enhancement with pin fin array has been discussed. © 2001 Scripta Technica, Heat Trans Asian Res, 30(7): 533–541, 2001 相似文献
15.
强化换热的方法及新进展 总被引:1,自引:0,他引:1
介绍了强化传热技术的概念、分类方法以及发展过程,总结了近几年出现的强化换热新技术、新方法。主要包括新型强化换热材料及其工质的应用、各种异型强化换热管的应用以及内插物强化换热技术,其中以新型强化换热材料及工质的介绍为重点。这些新型材料和工质包括多孔材料、液态金属和纳米流体。最后分析了目前我国强化换热技术的实际应用情况及存在的问题,提出了推广建议,对从事强化换热技术研究的工作者提供一定的参考。 相似文献
16.
建立了考虑液态相变材料自然对流的壳管式相变蓄热单元的三维模型,数值分析了自然对流对相变蓄热过程的影响.对比研究了外侧强化传热管和双侧强化传热管对相变蓄热单元蓄热性能的强化效果.结果表明,液态相变材料的自然对流,会引起固-液界面分布不均匀现象,采用外翅片管可以有效削弱这一现象;采用外侧强化传热管和双侧强化传热管,都可以缩短相变材料完全熔化以及整个蓄热过程所需时间.与采用光管时相比,采用外侧强化传热管时,完全熔化时间减少了18.0%;采用双侧强化传热管时,完全熔化时间减少52.5%.可见,采用带有外翅片的强化传热管,不仅可以削弱自然对流引起的固-液界面不均匀性问题,而且可以强化相变蓄热单元的蓄热性能. 相似文献
17.
Experiments were conducted to investigate flow and heat transfer characteristics of water in rectangular microchannels. All tests were performed with deionized water. The flow rate, the pressures, and temperatures at the inlet and outlet were measured. The friction factor, heat flux, and Nusselt number were obtained. The friction factor in the microchannel is lower than the conventional value. That is only 20% to 30% of the convectional value. The critical Reynolds number below which the flow remains laminar in the microchannel is also lower than the conventional value. The Nusselt number in the microchannel is quite different from the conventional value. The Nusselt number for the microchannel is lower than the conventional value when the flow rate is small. As the flow rate through the microchannel is increased, the Nusselt number significantly increases and exceeds the value of Nusselt number for the fully developed flow in the conventional channel. The micro‐scale effect was exhibited. The Nusselt number is also affected by the heat flux. The Nusselt number remains the constant value when the flow rate is small. The Nusselt number increases with the increase in the heat flux when the flow rate is large. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(4): 197–207, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20206 相似文献
18.
H.A. Mohammed P. GunnasegaranN.H. Shuaib 《International Communications in Heat and Mass Transfer》2011,38(1):63-68
In this paper, heat transfer and water flow characteristics in wavy microchannel heat sink (WMCHS) with rectangular cross-section with various wavy amplitudes ranged from 125 to 500 μm is numerically investigated. This investigation covers Reynolds number in the range of 100 to 1000. The three-dimensional steady, laminar flow and heat transfer governing equations are solved using the finite-volume method (FVM). The water flow field and heat transfer phenomena inside the heated wavy microchannels is simulated and the results are compared with the straight microchannels. The effect of using a wavy flow channel on the MCHS thermal performance, the pressure drop, the friction factor, and wall shear stress is reported in this article. It is found that the heat transfer performance of the wavy microchannels is much better than the straight microchannels with the same cross-section. The pressure drop penalty of the wavy microchannels is much smaller than the heat transfer enhancement achievement. Both friction factor and wall shear stress are increased proportionally as the amplitude of wavy microchannels increased. 相似文献
19.
Masahide Nakamura Misa Yoshihara Ken Watanabe Orie Tamura Wataru Sugiyama 《亚洲传热研究》2009,38(5):263-274
We numerically investigated the influence of the wall oscillation mode on the heat transfer characteristics of a two‐dimensional channel. In the present study, two channels with different wall oscillation modes were considered: a two‐dimensional channel bounded by a fixed wall and a transversely oscillating wall (channel A) and a two‐dimensional channel in which the upper and lower walls oscillate transversely in the same manner (channel B). The fully implicit finite difference method was used for the analysis of the conservation equations and the time‐dependent coordinate transformations were applied to solve the moving boundary problem. The calculated results are summarized as follows. (1) The wall oscillation has a significant effect on the heat transfer enhancement in the low‐Reynolds‐number region for each channel. (2) If increased pressure loss must be avoided, then channel B is more suitable than channel A. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20250 相似文献