Work loss

Indirect savings include work loss, death,and disability... 

It is important to keep tlie temperamre differenees in a low-temperature heat exehanger from beeoming too wide, espeeially at its low temperature end beeause here the temperature differenee represents work loss. The temperature differenee is shown in Figure 3-4 by areas marked X, Y, and Z. The assoeiated work losses are these areas divided by the square of their respeetive absolute temperatures and multiplied by 565, the heat rejeetion temperature. Their respeetive magnitudes... 

Inert gas is used to blanket certain fixed-roof tanks for safet. Here is how to determine the inert gas requirements. Inert gas is lost in two ways breathing losses from day/night temperature differential, and working losses to displaee changes in active level. 

Adiabatic expansion of the air in the engine causes a maximum temperature drop of the exhaust. Adiabatic compression causes a maximum temperature rise of the compressed air. These effects combine to cause the greatest work loss of any compressed-air system, when pressurized air must be cooled back to atmospheric temperature. The energy analysis parallels the one just made for the polytropic system. This shows that net areas on both PV and TS graphs measure the work lost. 

The total expenditure of work = loss of free energy... 

Beuzen JN, Ravily VF, Soutre EF, Thomander L (1993). Impact of fluoxetine on work loss in depression. Int Clin PsychopharmacoU 8> 319-21. 

Kletz, T. A. 1985. Cheaper, safer plants, or wealth and safety at work. Loss Prevention Hazard Workshop Module. 2nd ed. Rugby IChemE. 

Kletz, "Cheaper Safer Plants, or Wealth and Safety at Work", Loss Prevention Hazard Workshop Module, Second edition, IChemE, 1985... 

The frictional work loss W/ depends on the geometry of the system and the flow conditions and is an empirical function that will be explained later. When it is known, Eq. (6.13) may be used to find a net work effect Wv for otherwise specified conditions. 

The maximum work output of any thermodynamic system or process can be obtained, if the material in the system or the working fluid in the process is brought into equilibrium with the environment reversibly. The actual work output of a technical process with combustion is much smaller because the combustion is highly irreversible. The work losses in a continuous combustion can be evaluated if the exergy (or available energy) before and after the reaction is calculated. This exergy is described by the equation ... 

The exergy losses or the work losses are 79% and 21% in the boiler and condenser, respectively. In a Rankine cycle, exergy losses are due to irreversibilities occurring during heat transfer with finite temperature differences in the boiler and condenser. In order to decrease exergy losses, the temperature differences should be made smaller. Regeneration may help to decrease the temperature differences. 

Example 4.13 Simple reheat Rankine cycle in a steam power plant A simple ideal reheat Rankine cycle is used in a steam power plant (see Figure 4.19). Steam enters the turbine at 9000kPa and 823.15 K and leaves at 4350kPa. The steam is reheated at constant pressure to 823.15K. The discharged steam from the low-pressure turbine is at 10 kPa. The net power output of the turbine is 65 MW. Determine the thermal efficiency and the work loss at each unit. 

Tc = 285 K. The highest exergy loss occurs due to heat transfer in the boiler. The regeneration stage work loss is... 

Example 4.17 Ideal reheat regenerative cycle A steam power plant is using an ideal reheat regenerative Rankine cycle (see Figure 4.23). Steam enters the high-pressure turbine at 9000 kPa and 773.15 K and leaves at 850 kPa. The condenser operates at 10 kPa. Part of the steam is extracted from the turbine at 850 kPa to heat the water in an open heater, where the steam and liquid water from the condenser mix and direct contact heat transfer takes place. The rest of the steam is reheated to 723.15 K, and expanded in the low-pressure turbine section to the condenser pressure. The water is a saturated liquid after passing through the water heater and is at the heater pressure. The work output of the turbine is 75 MW. Determine the work loss at each unit. 

Table 4.6b shows the distribution of exergy losses at each process based on 7jt = 0.80, T0 = 290 K, 7n = 1700 K, and Tc = 290 K. The table shows that the highest exergy loss occurs due to heat transfer in the boiler. The work loss in the regeneration stage is minimal. 

The extracted steam is condensed and mixed with the water output of the condenser. The rest of the steam expands from 700 kPa to the condenser pressure of 10 kPa. The steam flow rate produced in the boiler is 60 kg/s. Determine the work loss at each unit. 

Example 4.20 Energy dissipation in an actual cogeneration plant A cogeneration plant uses steam at 900 psia and 1000°F to produce power and process heat (see Figure 4.26). The steam flow rate from the boiler is 16 lb/s. The process requires steam at 70 psia at a rate of 3.2 lb/s supplied by the expanding steam in the turbine. The extracted steam is condensed and mixed with the water output of the condenser. The remaining steam expands from 70 psia to the condenser pressure of 3.2 psia. If the turbine operates with an efficiency of 80% and pumps with an efficiency of 85%, determine the work loss at each unit. 

Example 4.23 Analysis of the Claude process in liquefying natural gas We wish to partially liquefy natural gas in a Claude process shown in Figure 4.28. It is assumed that the natural gas is pure methane, which is compressed to 80 bar and precooled to 300 K. In the expander and throttle the methane is expanded to 1.325 bar. The methane after the first heat exchange at state 5 is at 80 bar and 250 K. Thirty percent of the first heat exchangers output is sent to the expander. Only 10% of the first heat exchange is liquefied. The expander efficiency is 0.8. Determine the work loss in the liquefaction section excluding compression and precooling. 

---