Thermal properties fluids

Thermal Properties and Temperature related Behavior of Rock/fluid Systems... 

A knowledge of the viscous and thermal properties of non-Newtonian fluids is essential before the results of the analyses can be used for practical design purposes. Because of the nonlinear nature, the prediction of these properties from kinetic theories is as of this writing in its infancy. Eor the purpose of design and performance calculations, physical properties of non-Newtonian fluids must be measured. 

For turbulent flow of a fluid past a solid, it has long been known that, in the immediate neighborhood of the surface, there exists a relatively quiet zone of fluid, commonly called the Him. As one approaches the wall from the body of the flowing fluid, the flow tends to become less turbulent and develops into laminar flow immediately adjacent to the wall. The film consists of that portion of the flow which is essentially in laminar motion (the laminar sublayer) and through which heat is transferred by molecular conduction. The resistance of the laminar layer to heat flow will vaiy according to its thickness and can range from 95 percent of the total resistance for some fluids to about I percent for other fluids (liquid metals). The turbulent core and the buffer layer between the laminar sublayer and turbulent core each offer a resistance to beat transfer which is a function of the turbulence and the thermal properties of the flowing fluid. The relative temperature difference across each of the layers is dependent upon their resistance to heat flow. 

Only data on thermal properties of the fluid are necessarv to calculate mixer side coefficients in most... 

Silicone fluids find a very wide variety of applications mainly because of their water-repellency, anti-stick properties, low surface tension and thermal properties. 

Examination of the thermodynamic properties of fluid tables shows how the viscosity varies with temperature. In order to obtain a general impression of this, consider the data in the thermal properties of fluid tables and the various values at different temperatures. 

Najjar, Bell, and Maddox studied the influence of physical property data on calculated heat transfer film coefficients and concluded that accurate fluid property data is extremely important when calculating heat transfer coefficients using the relationships offered by Dittus-Boelter, Sieder-Tate, and Petukhov. Therefore, the designer must strive to arrive at good consistent physical/thermal property data for these calculations. 

Figure D-6 Pressure-enthalpy diagram for ethylene. (From RE Sterling, Fluid Thermal Properties for oi Petroleum Systems. Houston, TX Gulf Pub. Reprinted by permission.) - ...

The chaotropic properties of many chemical compounds prevent the H2O cage structures necessary for the formation of solvates and thus facilitate the transfer of nonpolar molecules between nonaqueous and aqueous phases. Water is incombustible and nonflammable, odorless and colorless, and is universally available in any quality important prerequisites for the solvent of choice in catalytic processes. The DK and d can be important in particular reactions and are advantageously used for the analysis and control of substrates and products. The favorable thermal properties of water make it highly suitable for its simultaneous dual function as a mobile support and heat transfer fluid, a feature that is utilized in the RCH/RP process (see below). 

At first sight, it might appear preferable to use water as a cooling fluid since it has better thermal properties and lower viscosity. In practice, however, water had to be ruled out because of troublesome water electrolysis phenomena which can occur between windings of the solenoids when a voltage is applied accros the magnet. 

The forward search starts from the name of a chemical compound, proceeds to finding its molecular structure, and then its physical and chemical properties, such as the boiling point, melting point, density, etcetera, in a handbook. Many databases for single compounds are also organized by classes and families of similar structures. Fluid solutions represent the next level of complexity. For the most important fluids, such as water, air, and some refrigerants, we can find extensive tables for the thermal properties of mixtures. For complex fluids, such as paint and emulsion, which are difficult to characterize and to reproduce, specialized books and journals should be consulted. The properties of some crystalline solids can be found, but usually not for multicrystal composite and amorphous solids. 

In this book we consider only fluids that are isotropic, meaning that the fluid properties are independent of direction. By contrast, solids can readily have spatially oriented properties. Consider, for example, a common material like graphite, whose molecular structure has strongly oriented layers. Both mechanical and thermal properties are vastly different normal to and parallel to the layers. While ordinary fluids exhibit no such properties, it is possible to have anisotropic fluids. For example, long-chain polymeric fluids can exhibit properties that are oriented relative to the flow directions. 

The mean temperature difference (A T)m depends on the terminal temperatures, the thermal properties of the two fluids and on the flow pattern through the exchanger. 

The nature of the colloidal dispersion can have important influences on other food properties. For example, a 50/50 % emulsion of oil (fat) and water has a very different thermal properties in O/W versus W/O form. The O/W emulsion would be expected to have the greater thermal conductivity, water being the external phase and, other factors being equal, should freeze at a faster rate [811]. O/W food emulsions tend to be quite fluid, whereas W/O food emulsions tend to be more viscous, sometimes solid-like. 

The rate of heat transfer per unit area of heat exchanger (heat flux), q, will be a function of the temperature driving force AT, tube diameter d, the mean fluid flow velocity u, fluid flow properties density p and viscosity p - and fluid thermal properties - specific heat capacity cp and thermal conductivity k. 

Since the purpose of diking is to contain a spilled fluid effectively while reducing the vapor generation rate, a secondary containment system that will be impervious to the fluid must be provided. It should also have favorable thermal properties to retard the boiloff rate. 

In view of the foregoing discussion, one may anticipate that convection heat transfer will have a dependence on the viscosity of the fluid in addition to its dependence on the thermal properties of the fluid (thermal conductivity, specific heat, density). This is expected because viscosity influences the velocity profile and, correspondingly, the energy-transfer rate in the region near the wall. 

Note that the relation in Eq. (6-12) is the same as Eq. (5-114), except that the Stanton number has been multiplied by Pr2/3 to take into account the variation of the thermal properties of different fluids. This correction follows the recommendation of Colburn [15], and is based on the reasoning that fluid friction and heat transfer in tube flow are related to the Prandtl number in the same way as they are related in flat-plate flow [Eq. (5-56)]. In Eq. (6-12) the Stanton... 

Their unique properties predestine them for both very specific applications and broad use in the field of polymer composites. They not only enhance mechanical properties but also electrical and thermal properties, act as flame retardants, etc. Thus their positives can be successfully exploited from simple or advanced polymer matrix reinforcement, through electronic devices, sensors and actuators, to electrorheological fluids, to name just the most important applications. 

We discussed the nature of glass transition only qualitatively in the section on thermal properties (Chapter 10). We did, however, mention a couple of essentially empirical equations that describe the viscosity of a fluid. One such is the Doolittle equation, which we rewrite here in a somewhat different form (Equation 13-103) ... 

---