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81.
A nonlinear regression scheme for determining heat transfer correlations from overall heat exchanger measurements is presented. The proposed scheme is valid for any two-fluid heat exchanger data where only one fluid's thermal resistance varies. The resulting regression model has three unknowns; two are associated with the variable resistance, and the third is the sum of all other resistances. The model can be analyzed only by using nonlinear regression because it cannot be transformed into linear form. Unlike existing approximate methods of analysis (known as modified Wilson plots), the proposed scheme is guaranteed to converge if a solution exists. The scheme was successfully tested by analyzing data collected on a tube-fin heat exchanger with continuous plain fins. 相似文献
82.
This paper presents a study on the deformation of anisotropic fibrous porous media subjected to moistening by water in the liquid phase. The deformation of the medium is studied by applying the concept of effective stress. Given the structure of the medium, the displacement of the solid matrix is not taken into account with respect to the displacement of the liquid phase. The transport equations are derived from the model proposed by Narasimhan. The transport coefficients and the relation between the variation in apparent density and effective stress are obtained by test measurements. A numerical model has been established and applied for studying drip moistening of mineral wool samples capable or incapable of deformation.Nomenclature
D
mass diffusion coefficient [L2t–1]
-
e
void fraction
-
g
gravity acceleration [Lt–2]
-
J
mass transfer density [ML–2t–1]
-
K
hydraulic conductivity [Lt–1]
-
K
s
hydraulic conductivity of the solid phase [Lt–1]
-
K
*
hydraulic conductivity of the deformable porous medium [Lt–1]
-
P
pressure of moistening liquid [ML–1 t–2]
-
S
degree of saturation
-
t
time [t]
-
V
speed [Lt–1]
-
X
horizontal coordinate [L]
-
Z
vertical coordinate measured from the bottom of porous medium [L]
-
z
z-coordinate [L]
Greek Letters
porosity
- 1
total hydric potential [L]
-
g
gas density [ML–3]
-
1
liquid density [ML–3]
-
0
apparent density [ML–3]
-
s
density of the solid phase [ML–3]
-
density of the moist porous medium [ML–3]
-
external load [ML–1t–2]
-
effective stress [ML–1t–2]
-
bishop's parameter
-
matrix potential or capillary suction [L]
Indices g
gas
- 1
moistening liquid
- p
direction perpendicular to fiber planes
- s
solid matrix
- t
direction parallel to fiber planes
- v
pore
Exponent *
movement of solid particles taken into account 相似文献
83.
84.
介绍了用恒流法自制仪器精确测定液体的粘滞系数.该自制仪器,能有效地保证底部的密封性、液体水位恒定和可操作性,还增设一个玻璃管连通器,附加一根标尺和游标使液体水位的测量精确度提高.并在接毛细管输出液体的量筒处加上光电计使测量液体流速的精确度提高,采用该仪器测定了水和乙醇两种液体在变温条件下的粘滞系数,经实验比对,所测得结果与理论值能较好地吻合.同时设计了可调换不同管径的毛细管,能快速准确地测量多种变温液体的粘滞系数. 相似文献
85.
Nicola Bellomo Nils Calander Eugen Mamontov Magnus Willander 《Comptes Rendus Mecanique》2003,331(7):461-467
86.
0Introduction Anelectronicpackageisgenerallyconstructedwithanactivesiliconchip,mountisland,gold wires,leadframesandsoldersasshowninFig.1(a).Toprotectfromtheenvironment,thesilicon chipisusuallyencapsulatedinresin.SincethesematerialshavedifferentCTE(coeffic… 相似文献
87.
用正交旋转试验设计,建立了一种比多元线性回归设计更简明的水基高分子润滑剂摩擦系数的数学模型.通过摩擦系数的响应曲面分析,可以确定润滑剂配方中各组分用量变化的优化水平,用图示法分析各组分间的交互作用和它们对润滑剂质量指标的影响.此外,利用响应曲面分析法还可为研究多组分复配润滑剂的润滑性能提供数理依据 相似文献
88.
89.
M. Yanuka 《Transport in Porous Media》1992,7(3):265-282
The percolation theory approach to static and dynamic properties of the single- and two-phase fluid flow in porous media is described. Using percolation cluster scaling laws, one can obtain functional relations between the saturation fraction of a given phase and the capillary pressure, the relative permeability, and the dispersion coefficient, in drainage and imbibition processes. In addition, the scale dependency of the transport coefficient is shown to be an outcome of the fractal nature of pore space and of the random flow pattern of the fluids or contaminant. 相似文献
90.