Work per unit mass

To be classed as a fan, the work per unit mass on the gas must be less than 25 kj kg" above this value it is called a turbo compressor. 

TABLE 9.6 Category According to Work per Unit Mass... 

Description Code Work per unit mass, m kg- Maxirmtm fan pressure, kPa Class... 

Figure 6.30. Expansion work per unit mass of ethane, propane, and isobutane.

The speciflc work done by the fluid in expansion can be read from Figures 6.30 or 6.31 if its temperature is unknown. Saturated propane at a pressure of 1.9 MPa (19 bar) has a temperature of 328 K, almost the superheat-limit temperature. Note that it is assumed that temperature is uniform, which is not necessarily the case. From Figure 6.30, the expansion work per unit mass for saturated liquid propane is... 

Explosion energy can be calculated by employing a slight variation on Eq. (6.3.26), by multiplying expansion work per unit volume by fluid volume, instead of multiplying expansion work per unit mass by fluid mass. Both propane and butane must be considered. This gives, for example, for vapor energy for the 50% fill-ratio case ... 

The combination of properties U - TS occurs so frequently in thermodynamic analysis that it is given a special name and symbol, namely A, the work fimction or maximum luork (because it represents the maximum work per unit mass, obtainable during any isothermal reversible change in any given system). Therefore, it is seen that... 

W Net work per unit mass done by system on surroundings J/kg L2T ... 

An engine operates on an Otto cycle with a compression ratio of 8. At the beginning of the isentropic compression process, the volume, pressure, and temperature of the air are 0.01 m, llOkPa, and 50°C. At the end of the combustion process, the temperature is 900°C. Find (a) the temperature at the remaining two states of the Otto cycle, (b) the pressure of the gas at the end of the combustion process, (c) the heat added per unit mass to the engine in the combustion chamber, (d) the heat removed per unit mass from the engine to the environment, (e) the compression work per unit mass added, (f) the expansion work per unit mass done, (g) MEP, and (h) thermal cycle efficiency. 

Bjarnholt and coworkers (Refs 13 and 21) used a semi-empirical approach to estimate the useful energy of HE via underwater expln energy measurements. In essence, their approach involves computation of a shock toss factor, ft > 1, to estimate the shock energy at the HE/water boundary from measured shock energies at some distance from the HE. This is coupled with the assumption that the measured bubble energy at some distance from the HE equals the bubble energy at the HE/water boundary. Then the total underwater expansion work per unit mass of HE, A0, is given by ... 

Air liquefaction system Liquid yield (y = riif/m) Work per unit mass liquefied, (kj/kg) Figure of merit... 

For flow in cylindrical conduits, the viscous work per unit mass of the fluid is expressed in terms of a friction factor and a specific kinetic energy by... 

Wp Pump work per unit mass of fluid, J/g or ft-lby/lb Z Height above datum plane, m or ft Z , at station a Zj, at station b... 

The enthalpy is also called total heat, inherent heat, and several other names in older thermodynamics texts. Obviously, it is the combination of the internal energy per unit mass and the injection work per unit mass. You will soon appreciate its convenience in solving practical problems. Substituting Eq, 4.33 in Eq. 4.32, we find its exact equivalent ... 

The amount of frictional work per unit mass in typical fluid flow problems is generally less than in the examples cited above. I... 

Here we use to avoid confusion with F for force. Most civil engineering texts call this quantity ghf or where g is the acceleration of gravity and hf or stands for friction head loss (Sec. 5.4). Some thermodynamics textbooks introduce the idea of the lost work in explaining the second law of thermodynamics. For a constant-density fluid at the heat reservoir temperature, the friction heating per unit mass is exactly equal to the lost work per unit mass, so some texts call this term LW. Other texts call it (-AP/p),since for the most common pipe friction problem, steady flow in horizontal, constant-area pipes. S - -tsPIp. 

Example 6.3. Two reservoirs are connected by 2000 ft of 3-in schedule 40 pipe (actual inside diameter is 3.068 in). We wish to pump 200 gal/min of water from one to the other. The levels in the reservoirs are the same, and both are open to the atmosphere see Fig. 6.11, What are the pump work per unit mass, the required pump power, and the required pump pressure rise ... 

Equation 7.54, which describes the work per unit mass to be obtained from a frictionless, moving blade which changes the velocity of a jet of fluid, can be put in the form of an instructive plot by dividing both sides by Vf /2,to find... 

Here the fluid enters at the center = 0), so the far right term is zero. Then solving for the work per unit mass, we find... 

For a pure impulse turbine, the work per unit mass passing through the system is given by Eq. 7,54. Prepare a plot of dW Jdm)l dW I... 

The Claude cycle has the advantage of being more efficient than the simple Linde cycle on the basis of work per unit mass of gas liquefied. As a result, it is possible to operate at a lower compressor discharge pressure than in the Linde cycle. 

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