Fluid energy conversions

Hung, T.C. (2001). Waste heat recovery of organic Rankine cycle using dry fluids. Energy Conversion and Management, 42 539-553. 

One form of solar heat does offer interesting possibilities and is refeiTcd to as OTEC (Ocean-Thermal Energy Conversion). The OTEC power plant principle uses the solar heat of ocean surface water to vaporize ammonia as a working fluid in a Rankine cycle. After the fluid is expanded in the turbine, it is condensed by the 22°C colder... 

In the interest of energy conversion, process heat can be obtained from a heat recovery unit in which heat is recovered from turbine or reciprocating engine exhaust. In a heat recovery unit, an exhaust gas flows over finned tubes carrying the fluid to be heated. The hot exhaust gas (9()0"F to I.2(K) F) heats the fluid in the tubes in a manner similar to that in which air cools the fluid in an aerial cooler. It is also possible to recover heat from exhausts by routing the exhaust duct directly through a fluid bath. The latter option is relatively inefficient but easy to install and control. 

As the fluid flows over the forward part of the sphere, the velocity increases because the available flow area decreases, and the pressure decreases as a result of the conservation of energy. Conversely, as the fluid flows around the back side of the body, the velocity decreases and the pressure increases. This is not unlike the flow in a diffuser or a converging-diverging duct. The flow behind the sphere into an adverse pressure gradient is inherently unstable, so as the velocity (and lVRe) increase it becomes more difficult for the streamlines to follow the contour of the body, and they eventually break away from the surface. This condition is called separation, although it is the smooth streamline that is separating from the surface, not the fluid itself. When separation occurs eddies or vortices form behind the body as illustrated in Fig. 11-1 and form a wake behind the sphere. 

Oceanic zooplankton species, wax esters in, 26 204-205 Ocean ranching, 3 198 Ocean raw materials, 17 684-699 consolidated deposits of, 17 691-694 economic aspects of, 17 697 fluid deposits of, 17 694-695 minerals recovery from, 17 695—697 unconsolidated deposits of, 17 686-691 Ocean resources, global, 17 684—686 Oceans, selenium content of, 22 11. See also Marine entries Seawater Ocean thermal energy conversion (OTEC) power plants, 13 267, 268 26 92-93 Ocean transportation, 25 328 Ochratoxin A, 7 267-268 Ochre (mineral hematite) color, 7 333... 

Because of its high heat capacity, ammonia is used as the working fluid in Ocean Thermal Energy Conversion (OTEC) units. See http //www.nrel.gov/otec/for more information. 

Incident solar energy is absorbed by the surface water of the oceans. Ocean surface temperatures in excess of 26°C occur near the equator. Pure water has a maximum density at a temperature of 4°C. The chilled water tends to settle to the depths of the ocean. The combination of the warmed ocean surface water and cold deep ocean water provides the thermodynamic condition needed to operate a heat engine called ocean thermal energy conversion (OTEC). A typical closed-cycle OTEC Rankine cycle using a working fluid such as ammonia or a freon is suggested. 

The suitability of a cycle for hydrogen production depends upon the overall thermal efficiency and operational feasibility. A highly endothermic reaction step is required in a cycle to achieve effective heat-to-chemical energy conversion. For efficient mass and momentum transfer a fluid based system is preferred [96] and, ultimately, for large-scale hydrogen production other factors such as environmental effects and cost effectiveness must also be considered. 

OCEAN THERMAL ENERGY CONVERSION (OTEC). Utilization of ocean temperature differentials between solar-heated surface water and cold deep water as a source of electric power. In tropical areas such differences amount to 35-40°F. A pilot installation now operating near Hawaii utilizes a closed ammonia cycle as a working fluid, highly efficient titanium heat exchangers, and a polyethylene pipe 2000 feet long and 22 inches inside diameter to handle the huge volume of cold water required. Alternate uses for such a system, such as electrolysis of water,... 

Anderson Computational Fluid Dynamics The Basics with Applications Anderson Modem Compressible Flow With Historical Perspective Arora Introduction to Optimum Design Borman and Ragland Combustion Engineering Burton Introduction to Dynamic Systems Analysis Culp Principles of Energy Conversion... 

The intracellular concentration of K+ is high in most animal cells relative to that of external fluids. The converse is true for Na+. The free energy necessary to pump these ions against their concentration gradients is derived from the hydrolysis of ATP. Hydrolysis is controlled by the K+ and Na+ stimulated ATPase which is imbedded in the cell membrane and has stimulation sites on both the intracellular and extracellular surfaces. To fully activate the pump, Mg2+, in addition to Na+ and K+, must be present. K+ activates the ATPase exterior to the cell and Na+ on the interior. An introduction to this subject can be found in Stryer72. The effect of vanadate on Na+, K+-ATPase has been reviewed19 73. ... 

During food engineering operations, many fluids deviate from laminar flow when subjected to high shear rates. The resulting turbulent flow gives rise to an apparent increase in viscosity as the shear rate increases in laminar flow, i.e., shear stress = viscosity x shear rate. In turbulent flow, it would appear that total shear stress = (laminar stress + turbulent stress) x shear rate. The most important part of turbulent stress is related to the eddies diffusivity of momentum. This can be recognized as the atomic-scale mechanism of energy conversion and its redistribution to the dynamics of mass transport processes, responsible for the spatial and temporal evolution of the food system. 

Fostedil exists in two polymorphic forms, characterized by melting points of 95.3°C (Form I) and 96.4°C (Form II), a free energy difference of only 71.8 cal/mol at 37°C, and distinctly different infrared absorption and x-ray powder diffraction patterns [6]. Solubility studies suggested that Form I was more stable than Form II. Mechanical mixing in an automated mortar showed that complete conversion of Form II to Form I occurred in 2 h. Milling fostedil in an industrial fluid energy... 

---