Thermal energy fluid heat exchangers

Thermal Energy Fluid Heat Exchangers, Condensers, and... 

Fig. 6. In a binary electricity generation plant, the hydrothermal water from the weU, A, is passed through a heat exchanger, B, where its thermal energy is transferred to a second, more volatile working fluid. The second fluid is vaporized and deflvered to a turbine, D. After exiting the turbine the spent working fluid is cooled and recondensed in another heat exchanger, E, using water or air as the coolant, F. It is then fed back to the primary heat exchanger to repeat the cycle. Waste hydrothermal fluid, C, can be reinjected into the producing field.

Convective heat transmission occurs within a fluid, and between a fluid and a surface, by virtue of relative movement of the fluid particles (that is, by mass transfer). Heat exchange between fluid particles in mixing and between fluid particles and a surface is by conduction. The overall rate of heat transfer in convection is, however, also dependent on the capacity of the fluid for energy storage and on its resistance to flow in mixing. The fluid properties which characterize convective heat transfer are thus thermal conductivity, specific heat capacity and dynamic viscosity. 

The overall heat transfer coefficient for thermal energy exchange between the tube wall and the reacting fluid may be taken as 1.0 x 10 3 cal/cm2-sec-°K. The effective thermal conductivity of the catalyst pellets may be taken as equal to 6.5 x 1CT4 cal/(sec-cm-°C). 

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,... 

The thermal conductivity of solvents, X, is an important property of solvents with respect to the removal of heat generated in exothermal reactions and in their uses as heat exchange fluids. When convection is the mechanism of thermal conductance, it depends on the mobility of the molecules of the solvent and therefore increases the smaller these molecules are. For globular molecules in the gaseous phase the thermal conductivity is proportional to the viscosity X/r = (5/2 )R/M, where Mis the molar mass, but this relationship does not hold in liquids. For the latter, the potential energy is also involved, and the expression that fits the data for over 270 solvents is (Marcus 1998) ... 

JAEA conducted an improvement of the RELAP5 MOD3 code (US NRC, 1995), the system analysis code originally developed for LWR systems, to extend its applicability to VHTR systems (Takamatsu, 2004). Also, a chemistry model for the IS process was incorporated into the code to evaluate the dynamic characteristics of process heat exchangers in the IS process (Sato, 2007). The code covers reactor power behaviour, thermal-hydraulics of helium gases, thermal-hydraulics of the two-phase steam-water mixture, chemical reactions in the process heat exchangers and control system characteristics. Field equations consist of mass continuity, momentum conservation and energy conservation with a two-fluid model and reactor power is calculated by point reactor kinetics equations. The code was validated by the experimental data obtained by the HTTR operations and mock-up test facility (Takamatsu, 2004 Ohashi, 2006). 

A heat exchanger is any device that effects transfer of thermal energy between two fluids that are at different temperatures. The two fluids do not come in direct contact but are separated by a solid surface or tube wall. Common heat exchangers include... 

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