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排序方式: 共有92条查询结果,搜索用时 31 毫秒
1.
Du Yongbo Yu Pengfei Wang Junxiong Zhang Jinping Wang Chang’an Che Defu 《Journal of Thermal Analysis and Calorimetry》2021,143(1):327-334
Journal of Thermal Analysis and Calorimetry - Coal O2/CO2 combustion is a promising carbon capture and storage technology for coal-fired power plant. Char consumption rate prediction is essential... 相似文献
2.
3.
根据拼合原理,以对苯二酚(p-HQ)、间苯二酚(m-HQ)及邻苯二酚(o-HQ)为先导化合物,通过一侧酚羟基的苄基保护、引入溴乙酸甲酯、还原、与3种糖元偶联、脱除保护基得到9种目标化合物。 同样以3-(4-羟基苯基)-1-丙醇为起始物质,通过苄基保护、与3种糖元偶联、脱除保护基得到3种目标化合物。 通过IR、1H NMR、13C NMR、HRMS等波谱分析方法对所合成的12种目标化合物进行了结构表征。 对合成的酚类糖苷缀合物进行了美白活性研究。 结果表明,化合物p-HQ-6a、m-HQ-7a、p-HQ-6b、m-HQ-6b、o-HQ-6b、p-HQ-6c、m-HQ-7c、L-3a和L-4b对酪氨酸酶有抑制作用,其中o-HQ-6b和p-HQ-6c对酪氨酸酶的抑制作用优于阳性对照物α-熊果苷。 相似文献
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5.
刘德辅 《数学物理学报(B辑英文版)》1995,(1)
(刘德辅)BEHAVIORASt→∞OFTHESOLUTIONSOFTHELINEARSYSTEMOFELASTICTHEORYONNON-STAR-SHAPEDEXTERIORDOMAINS¥LiuDefu(Dept.ofApplMath.,Bei... 相似文献
6.
大型对称不定箭形线性方程组的分解方法 总被引:4,自引:1,他引:3
1 引言 首先考虑2×2矩阵 显然当k>1/2时,矩阵K是对称正定的,且K可以分解成Cholesky因子:当k=1/2时,K为奇异矩阵;而当k<1/2时,K为对称不定矩阵,这时K有广义Cholesky分解式:并且这种分解是稳定的,一般地我们给出定义 定义1.1 设有矩阵K∈R~((m+n)×(m+n)),若总存在排列矩阵P∈R~((m+n)×(m+n))和对称正定矩阵H∈R~(m×n)、G∈R(m×m)使得则称矩阵K为对称拟定(Symmetric quasidefinite)矩阵。 相似文献
7.
The heat transfer process occurring in a condensing heat exchanger where noncondensible gases are dominant in volume is different from the condensation heat transfer of the water vapor containing small amount of noncondensible gases. In the process the mass transfer due to the vapor condensation contributes an important part to the total heat transfer. In this paper, the Colburn-Hougen method is introduced to analyze the heat and mass transfer process when the water vapor entrained in a gas stream condenses into water on the tube wall. The major influential factors of the convective-condensation heat transfer coefficient are found as follows: the partial pressure of the vapor p
v
, the temperature of the outer tube wall T
w
, the mixture temperature T
g
, Re and Pr. A new dimensionless number Ch, which is defined as condensation factor, has been proposed by dimensional analysis. In order to determine the relevant constants and investigate the convection-condensation heat and mass transfer characteristics of the condensing heat exchanger of a gas fired condensing boiler, a single row plain tube heat exchanger is designed, and experiments have been conducted with vapor-air mixture used to simulate flue gases. The experimental results show that the convection-condensation heat transfer coefficient is 1.52 times higher than that of the forced convection without condensation. Based on the experimental data, the normalized formula for convention-condensation heat transfer coefficient is obtained.
A
heat transfer area m2
-
Ch
condensation factor
-
c
p
specific heat at constant pressure, J/(kg·K)
-
G
mass flux Kg/(m2·s)
-
h
heat transfer coefficient W/(m2·K)
-
J
J-factor
-
Nu
Nusselt number
-
pa
pressure
- Pr
Prandtl number
-
Q
heat transfer rate
-
q
heat flux W/m2
-
r
latent heat, kJ/kg
- Re
Reynolds number
-
Sc
Schmidt number
-
T
temperature, C or K
-
heat conductivity m W/(m·K)
-
density, kg·m3
-
g
gas
-
h
moistened hot air
-
i
interface
-
v
vapor
-
w
water 相似文献
8.
The near-wall transport characteristics, inclusive of mass transfer coefficient and wall shear stress, which have a great
effect on gas–liquid two-phase flow induced internal corrosion of low alloy pipelines in vertical upward oil and gas mixing
transport, have been both mechanistically and experimentally investigated in this paper. Based on the analyses on the hydrodynamic
characteristics of an upward slug unit, the mass transfer in the near wall can be divided into four zones, Taylor bubble nose
zone, falling liquid film zone, Taylor bubble wake zone and the remaining liquid slug zone; the wall shear stress can be divided
into two zones, the positive wall shear stress zone associated with the falling liquid film and the negative wall shear stress
zone associated with the liquid slug. Based on the conventional mass transfer and wall shear stress characteristics formulas
of single phase liquid full-pipe turbulent flow, corrected normalized mass transfer coefficient formula and wall shear stress
formula are proposed. The
calculated results are in good agreement with the experimental data. The shear stress and the mass transfer coefficient in
the near wall zone are increased with the increase of superficial gas velocity and decreased with the increase of superficial
liquid velocity. The mass transfer coefficients in the falling liquid film zone and the wake zone of leading Taylor bubble
are lager than those in the Taylor bubble nose zone and the remaining liquid slug zone, and the wall shear stress associated
falling liquid film is larger than that associated the liquid slug. The mass transfer coefficient is within 10−3 m/s, and the wall shear stress below 103 Pa. It can be concluded that the alternate wall shear stress due to upward gas–liquid slug flow is considered to be the major
cause of the corrosion production film fatigue cracking. 相似文献
9.
The forced convection heat transfer with water vapor condensation is studied both theoretically and experimentally when wet
flue gas passes downwards through a bank of horizontal tubes. Extraordinarily, discussions are concentrated on the effect
of water vapor condensation on forced convection heat transfer. In the experiments, the air–steam mixture is used to simulate
the flue gas of a natural gas fired boiler, and the vapor mass fraction ranges from 3.2 to 12.8%. By theoretical analysis,
a new dimensionless number defined as augmentation factor is derived to account for the effect of condensation of relatively
small amount of water vapor on convection heat transfer, and a consequent correlation is proposed based on the experimental
data to describe the combined convection–condensation heat transfer. Good agreement can be found between the values of the
Nusselt number obtained from the experiments and calculated by the correlation. The maximum deviation is within ±6%. The experimental
results also shows that the convection–condensation heat transfer coefficient increases with Reynolds number and bulk vapor
mass fraction, and is 1∼3.5 times that of the forced convection without condensation. 相似文献
10.