Thermal efficiency cooling flow rates

High heat-transfer rates and sufficient cooling via internal, two-phase flow and circulation are consequently necessary to ensure that modem boilers operate below their particular critical heat-flux (CHF) conditions. This minimizes poor thermal efficiency performance, risks of thermal metal fatigue, and probable tube failures from excessive temperatures. 

An important thermodynamic parameter in cooling tower calculations is the ratio of the thermal capacity of the water stream to that of the sir stream. This parameter is referred to as, the tower capacity factor. It is shown that when air or water efficiency, are plotted against the capacity factor test points for a given tower are found to lie on a single smooth curve. The correlation is obtained, irrespective of whether the equipment is used as a water cooler or air cooler, and irrespective of the temperature levels, temperature ranges and barometric pressures. The paper also shows that when a specified amount of heat has to be rejected into a specified air stream, optimum performance giving the lowest average water temperature is obtained when the water flow rate is chosen so that its thermal capacity is equal to the potential thermal capacity of the air stream. 13 refs, cited. 

A power plant operating on heat recovered from the exhaust gases of internal-combustion < uses isobutane as the working medium in a modified Rankine cycle in which the upper pressure I is above the critical pressure of isobutane. Thus the isobutane does not undergo a change of p" as it absorbs heat prior to its entry into the turbine. Isobutane vapor is heated at 4,800 kPa to 2 and enters the turbine as a supercritical fluid at these conditions. Isentropic expansion in the turh produces superheated vapor at 450 kPa, which is cooled and condensed at constant pressure, resulting saturated liquid enters the pump for return to the heater. If the power output of the modi Rankine cycle is 1,000 kW, what is the isobutane flow rate, the heat-transfer rates in the heater condenser, and the thermal efficiency of the cycle ... 

Example 5.18 Determination of Coolant Flow Rate Required Consider a 100-plate, 10-kWe PEFC stack operating at 48% thermal efficiency, as determined from a stack voltage measurement. Each individual fuel cell is to be cooled by a flowing Uquid water coolant channel. In order to balance the water generated in the fuel cell and prevent flooding, it is... 

Thermal conductivity is an important parameter used for material thermal calculations in the injection molding simulation. A variation in the thermal conductivity will alter the cooling rate and hence cause a variation in the temperature this in turn will cause the viscosity, pressure, and frozen layer to vary. Classical Fourier theory, which assumes thermal conductivity to be a constant scalar value depending only on temperature alone, is inadequate to describe the heat conduction in deformed molten polymer. Van den Brule (1989, 1990) and van den Brule and O Brien (1990) suggested that heat transport mechanisms along the backbone of a polymer chain are more efficient than those between neighboring chains. Hence, the orientation of polymer chain segments induced by flow leads to an anisotropic thermal conductivity. To describe anisotropic thermal conduction, one... 

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