Work inputs

Similar to volumetric efficiency, isentropic (adiabatic) efficiency T is the ratio of the work required for isentropic compression of the gas to work input to the compressor shaft. The adiabatic efficiency is less than one mainly due to pressure drop through the valve ports and other restricted passages and the heating of the gas during compression. 

Tabie 3-i gives the work inputs to the system and the overaii thermodynamie effieieney of the proeess. An aeeounting of the work quantities suppiied to the various funetions in the proeess is given in Tabie 3-2. 

Wa = adiabatic work input P[ = inlet pressure Qi = inlet volume T(a = adiabatic efficiency... 

W, = work input to the shaft Ql = volume of lubricant Pl = specific weight of the lubricant CpL = specific heat of the lubricant At = lubricant temperature rise... 

The actual work input coefficient, is written by taking the ideal work input coefficient, Equation 5.1, and modifying by the addition of the slip factor, SF. The geometric relationship of the Stodola slip function is shown in Figure 5-23. 

By replacing the ideal work input coefficient with actual work input coefficient, the actual head input can be written as... 

Wiesner, 153. 126 Wong, 426 Work, 59, 109 Work input coefficient, actual, I -54... 

The difference between the work input and the elastic stored energy is the crack growth resistance, R,... 

The above analysis has been concerned with heat transfer from the control volume. Consider next heat [AQ] = [d REvlx transferred to the control volume. Then that heat could be reversibly pumped to CV (at temperature T) from the atmosphere (at temperature To) by a reversed Carnot engine. This would require work input... 

A closed cycle [CHT]i, with state points 1,2,3,4, is shown in the T,s diagram of Fig. 3.7. The specific compressor work input is given by... 

Consider next a similar recuperative cycle, but one in which the compression process approximates to isothermal rather than isentropic, with the work input equal to the heat rejected (this may be achieved in a series of small compressions of polytropic efficiency Tjp, followed by a series of constant pressure heat rejections). It may then be shown that the thermal efficiency of this cycle is given by... 

In the transmission of energy by these simple machines, the conseiwation law always applies The work input equals the work output. Wlien work is done by a system, energy is transferred out of it and when work is done on a system, energy is transferred into it. When two objects interact by way of a machine (e.g. a lever), the work out of one object equals the work into the other. The work done by a person forcing one end of a lever downward equals the work done lifting a load at the other end as the lever moves upward. In any practical situation, the frictional forces resisting motion will always increase the amount of force (and work) required to do ajob. 

The car used in the example above would travel 90 meters during its acceleration (assumed constant) to 30 m/s in 6 seconds. The increase in kinetic energy would be 450,000 joules, which exactly equals the work input of 5,000 newtons x 90 meters. 

The number of rotor revolutions per mix cycle relates directly to unit work input and to temperature rise. This variable can be employed when checking between mixed batches for changes in feeding operations, materials and mixer conditions. Power/work input measures the energy consumed by the mixer. A greater compensation for variations in feed stocks and mixer temperatures is provided by power control. 

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