Last time we learned that the amount of useful work, To better gauge the effects of a condenser, let’s look at the differences between its being present and not present. Let’s first take a look at how much work is produced by a steam turbine without a condenser. The steam entering the turbine inlet has a pressure of 2000 pounds per square inch (PSI) and a temperature of 1000°F. Knowing these turbine inlet conditions, we can go to the steam tables in any thermodynamics book to find the enthalpy, by Gordon J. Van Wylen and Richard E. Sonntag list enthalpy values over a wide range of temperatures and pressures. For our example this volume tells us that,Fundamentals of Classical Thermodynamics
where Since there is no condenser attached to the steam turbine’s exhaust in our illustration, the turbine discharges its spent steam into the surrounding atmosphere. The atmosphere in our scenario exists at 14.7 PSI because our power plant happens to be at sea level. Knowing these facts, the steam tables inform us that the value of the exhausted steam’s enthalpy,
Combining the two equations we are able to calculate the useful work the turbine is able to perform as:
h1474 BTU/lb – 1015 BTU/lb = 459 BTU/lb_{2} = This equation tells us that for every pound of steam flowing through it, the turbine converts 459 BTUs of the steam’s heat energy into mechanical energy to run the electrical generator. Next week we’ll connect a condenser to the steam turbine to see how its efficiency can be improved.
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