共查询到20条相似文献,搜索用时 75 毫秒
1.
2.
横掠钉头管对流换热的实验研究 总被引:5,自引:1,他引:4
利用热质比拟原理及萘升华技术,对横掠钉头管的对流换热进行了实验研究。对管面上及钉头上的放热系数分别进行了测量,并对其做了比较。最后给出了计算钉头管平均放热的实验关联式。 相似文献
3.
如果使用式(12)测定换热系数值,则隐含测试者已假设测试装置处于热平衡之中。由于橡胶平板比我们的测试装置中的其他元件有更大的热惯性,因此达到上述热平衡状态所需的时间必须加以考虑。因此作为第二步的校准工作,我们测定 相似文献
4.
分析表明轮胎的热状态受轮胎外形尺寸和表面对流换热系数变量的影响。在本文报道的研究工作中.一种试验装置已被设计和组装,并能在宽广的操作条件下测定轮胎的对流换热系数。所测得数据表明空气流动速度、边界层厚度和湍动水平、湿度、轮胎表面污染、轮胎表面粗糙度和不平整度、轮胎表面的湿润度等对对流换热系数有影响,并讨论了这些结果对轮胎功损耗的意义。 相似文献
5.
6.
梭式窑对流换热的模拟研究 总被引:10,自引:0,他引:10
在梭式窑空气动力模型上,采用不同规模的烽嘴,研究了烧嘴的流量与喷速对窑内对流换热的影响。提出了换热不均匀度的定义式,推导了入窑气体温度与换热不均匀度的关系,得到了梭式窑对流换热关系式。 相似文献
7.
利用萘升华热质比拟实验方法,在直流吸入式风洞中对雷诺数5 000—50 000范围内空气绕流7种轴长比椭圆柱在不同攻角下的平均传热特性进行了实验测量,并且采用小区域平局传热等效局部传热的方法,对3种不同轴长比椭圆柱的局部传热特性进行了实验研究,对比分析了多种工况下的平均努塞尔数和局部努塞尔数。结果表明:各轴长椭圆柱表面局部努塞尔数分布趋势相似,前驻点处局部努塞尔数最高,沿着流体流向椭圆柱体表面局部努塞尔数逐渐减小,在分离点处达到最低点,随后再逐渐增加,迎流面局部努塞尔数始终高于背流面对称区域;7种不同轴长比椭圆柱的表面平均努塞尔数在攻角0°—90°范围内随攻角的变化趋势基本一致,平均努塞尔数均随攻角的增加而增大。 相似文献
8.
9.
10.
11.
建筑外表面对流传质系数是围护结构热湿耦合计算和建筑能耗模拟中的重要参数。为直接准确得到该参数,提出了建筑物壁面对流传质系数的测量方法,该方法通过测量萘试件的质量通量和表面温度,即可计算得到壁面传质系数。为验证该方法的准确性及可靠性,在风洞内设置6组不同风速工况,分别采用了萘升华法与传统热平衡法进行对比。结果表明:随风速的增加,萘试件表面温度随之降低,而对流传质系数逐渐增加。两种方法测试结果接近,二者所得对流传质系数相差在10%以内,不同风速条件下平均偏差小于5%,认为该测量方法可行。该研究可为室外真实条件下建筑外表面对流传质系数提供测试方法指导,对热湿耦合计算和墙体蒸发换热的研究也具有重要意义。 相似文献
12.
An experimental study was conducted to investigate the fouling process of calcium carbonate on the heat transfer surface, during forced convective heat transfer. The dynamic monitoring apparatus of fouling resistance was set up for the present experiments. The fouling behavio(s were examined under different factors including fluid velocity, hardness,alkalinity, solution temperature, and wall temperature. Asymptotic fouling curves varying with time were obtained. The fouling rate and asymptotic fouling resistance increased and the induction periods were shortened with the fluid velocity decreasing, hardness andalkalinity increasing, and solution temperature and heat transfer surface temperature increasing. Thecomponents of fouling that formed on the heat transfer surface included crystallization fouling and particulate fouling. The thermal performance parameter of fouling,ρfhf, varied from 380 to 2600 kg·W·(m^4·K)^-1, increasing with growing velocity and decreasing solution temperature, hardness or alkalinity. Furthermore, the thermal conductivity of fouling, λf, varied from 1.7 to 2.2 W·(m·K)^-1 . 相似文献
13.
14.
15.
A. V. Shenoy 《加拿大化工杂志》1992,70(2):375-380
There have been many attempts in the literature to develop analogies for momentum, heat and mass transfer to drag reducing fluids; however, none have considered the presence of a pressure gradient when formulating the analogies. In the present work, a momentum/heat transfer analogy has been developed under the influence of small pressure gradient for drag reducing fluids using the Nakayama et al. (1984) solution methodology for Newtonian fluids. The results of the present analysis have been found to compare well with existing theoretical expressions. 相似文献
16.
William B. Krantz Hanyong Lee Siladitya Ray Chaudhuri Sun‐Tak Hwang 《American Institute of Chemical Engineers》2012,58(3):678-689
Density change during mass or heat transfer can cause convection in the absence of buoyancy forces. Prior studies have shown that this convection can be significant in the determination of diffusion coefficients and in the casting of polymeric membranes. Including this effect is challenging even for advanced numerical codes. A general methodology for obtaining the mass‐average velocity for unsteady‐state, one‐dimensional, multicomponent mass and/or heat transfer circumvents the problem of numerically solving the coupled continuity equation. Scaling analysis permits assessing the importance of this convection for a generic equation‐of‐state. Numerical predictions for evaporation from a liquid layer for components having density ratios of 1:1 and 0.7:1 indicate that ignoring convection results in errors of 34% and 24% in the evaporation time and final thickness, respectively. This convection also influences the evaporation in the percutaneous application of cosmetics, medications, and insecticides, curing of paints, varnishes, and lacquers, and formation of thin films. © 2011 American Institute of Chemical Engineers AIChE J, 2012 相似文献
17.
18.
柯尔本类似律不仅形式最简单,而且能较好地与化工传递过程的实验数据相吻合.本文介绍了柯尔本类似律、研究了柯尔本类似律的适用范围.结果表明:柯尔本类似律适用于无形体阻力的工况;对于有形体阻力的工况,同一设备内的传热与传质的柯尔本j因数仍可近似相互换算. 相似文献
19.