Thermo 2

Engr. Rolie A. Castro

A steam turbine with rated capacity of 56,400kW operates with steam at inlet conditions of8,600 kPa and 500oC, and discharges into acondenser at a pressure of 10 kPA Assumingthe turbine efficiency of 0.75, determine thestate of the steam at discharge and the massflow rate of the steam.

Water at 45oC and 10 kPa enters an adiabaticpump and is discharge at a pressure of 8,600kPa. Assume the pump efficiency to be 0.75.Calculate the work of the pump, thetemperature change of the water, and theentropy change of the water.

A steam power cycle.

inpumpW ,

SteamTurbine

Mechanical Energyto Generator

Heat Exchanger

Cooling Water

Pump

Fuel

Air

CombustionProducts

System Boundary

for Thermodynamic

Analysis

outturbineW ,

outQ

outstackQ ,

inQ

A Rankine power plant operates on steam at a boiler pressure of 500 psia. If the condenser pressure is maintained at 2 psia and the steam leaves the boiler superheated 400oF, calculate the efficiency of the cycle and the quality of the steam leaving the turbine.

* A fuel is burned within the engine itself, and the combustion products serves as the working medium, acting on a piston of the cylinder.Air Standard Power Cycle

a. Otto Cycle b. Diesel Cyclec. Brayton Cycle

External Heat Source Power Cyclesa. Stirling Cycleb. Ericsson Cycle

Spark Ignition

Compression ignition

1-2 ; Isothermal compression with heat rejection

2-3 ; Constant pressure with heat addition

3-4 ; Isothermal expansion with heat addition

4-1 ; Constant pressure with heat rejection

An engine operates on the air standard Ottocycle. The conditions at the start ofcompression are 80oF and 14.7 psia. The heatadded is 2100 BTU/lb-mole of air. Thecompression ratio is 10:1. Determine:

a. the pressure and temperature at eachstate in the cycle.

b. the thermal efficiency of the engine.

c. the mean effective pressure.

Process Operation

1-2 ; Isobaric absorption of heat at low temp.

2-3 ; Adiabatic compression

3-4 ; Isobaric rejection of heat at high temp.

4-1 ; Adiabatic expansion

Electrical Power In

Compressor

Evaporator

Condenser

Expansion Valve

inW

inQ

outQ

A vapor compression type of plant employingtetrafluoroethane as refrigerant is to be designedfor a capacity of 10 tons of refrigeration whenoperating between a condenser temperature of140oF and an evaporator temperature at -20oF.Assuming that the compression process isreversible and adiabatic and that the vapor leavingthe evaporator is saturated, determine:

a. the refrigeration effectb. the circulating effectc. the power requiredd. COPe. heat rejected

A house has a winter heating requirement of 30kW and a summer cooling requirement of 60 kW.Consider a heat pump installation to maintain thehouse temperature at 20oC in winter and 25oC insummer. This requires circulation of refrigerantthrough the interior exchanger coils at 30oC inwinter and 5oC in summer. Underground coilsprovide the heat source in winter and the heat sinkin summer. For a year round ground temperature of15oC, the heat transfer characteristics of the coilsnecessitates refrigerants temperature of 10oC inwinter and 25oC in summer. What are the minimumpower requirements for winter heating and summercooling?

A 2000 ft3 boiler is operated at constantpressure of 200 psia. Initially, the boiler containssaturated liquid water and saturated steam atequilibrium with each other. During a cetain timeinterval, 40,000 lbm of steam at 400

oF and 200 psiaare withdrawn while simultaneously 20,000 lbm offeedwater at 130oF are fed to the boiler. At the endof the process, the vapor remaining in the boileroccupies 70% of the boiler volume. Determine:

a. % by wt. composition of initial content of theboiler?

b. Amount of heat added to the boiler during theprocess