Thermal Power Engineering Answers

In a 15 TR ammonia refrigeration plant for cooling a large warehouse, the
condensing temperature is 25oC and evaporating temperature -10oC. The refrigerant
ammonia is sub-cooled by 5oC before passing through the throttle valve. The vapour
leaving the evaporator is 0.97 dry. Find:
1. Coefficient of performance
2. Power required

Saturation
Temperature Enthalpy Entropy Specific Heat,
oC kJ/kg kJ/kgK kJ/kgK
Liquid Vapour Liquid Vapour Liquid Vapour
25 298.9 1465.84 1.1242 5.0391 4.6 2.8
-10 135.37 1433.05 0.5443 5.4770 - -

A chemical laboratory uses an air refrigeration cycle system operating between
pressures of 4 bar and 16 bar. The air temperature after heat rejection to
surrounding is 37oC and air temperature at exit of refrigerated lab is 7oC. The
isentropic efficiencies of turbine and compressor are 0.85 and 0.8 respectively.
Determine compressor and turbine work per TR; C.O.P; and power per TR. Take

restaurant food storage air conditioning working on air refrigeration cycle of 10
tonnes capacity works between 4 bar and 16 bar. The air leaves the cold chamber at
0
oC and discharges air at 25oC to the expansion cylinder after air cooler. The
expansion and compression cylinders are double acting. The mechanical efficiency of
compressor and expander are 85% and 80% respectively. The compressor speed is
250 r.p.m and has a stroke of 250mm Determine:
1. C.O.P
2. Power required
3. Bore of compression and expansion cylinder
(Assume isentropic compression and expansion as polytropic with n = 1.25)

An aircraft air conditioner works between the pressure limits of 1 bar and 5 bar. The
temperature of the air entering the compressor from the cabin and expansion
cylinder are 10o
c and 25oC respectively. The expansion and compression follow the
pv1.3=constant. Find the following:
1. The theoretical C.O.P of the refrigeration cycle:
2. If the load on the system assuming the actual C.O.P is 50% of the theoretical
C.O.P
3. The stroke length and the piston diameter of single acting compressor
running at 300 r.p.m and the volumetric efficiency is 85%.
(Take L/d = 1.5 : cp = 1.005 kJ/kgK ; cv = 0.71 kJ/kgK

Refrigerant-134a enters the condenser of a heat pump at 180 psia and 140 ºF at a rate of 8.3 lbm/min and leaves as a saturated liquid. If the compressor consumes 103.25 Btu/min of power, determine the coefficient of performance of the heat pump unit.

Question 3 of 3
"In a reversible non-flow process with a gas, the initial pressure and specific volume are 270 psia and 4 cu. ft/lb, respectively. The final pressure and specific volume are 80 psia and 9 cu. ft/lb."

The same gas is brought reversibly from the same initial to the same final state above, but the state change is affected by a non-flow constant volume, and a non-flow constant pressure process in combination. Draw the p-v diagram and find the work done on or by the gas if he sequences of the processes is Constant pressure followed by constant volume
Select the correct response:

1.250.0 BTU/lb
2.124.5 BTU/lb
3.45.0 BTU/lb
4.74.00 BTU/lb

Question 2 of 3 5 Points
"In a reversible non-flow process with a gas, the initial pressure and specific volume are 270 psia and 4 cu. ft/lb, respectively. The final pressure and specific volume are 80 psia and 9 cu. ft/lb."

The same gas is brought reversibly from the same initial to the same final state above, but the state change is affected by a non-flow constant volume, and a non-flow constant pressure process in combination. Draw the p-v diagram and find the work done on or by the gas if he sequences of the processes is Constant volume followed by constant pressure.
Select the correct response:

1.124.5 BTU/lb
2.45.0 BTU/lb
3.250.0 BTU/lb
4.74.00 BTU/lb

Two boilers one with superheater and other without superheater are delivering equal quantities of steam into a common main.The pressure in the boilers and main is 20 bar absolute.The temperature of steam from a boiler with a superheater is 350 degree Celsius and temperature of steam in the main 250 degree Celsius.Determine the quality of steam supplied by the other boiler assume specific heat of superheated steam Cp-2.25KJ/Kg K

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question in picture

Two pounds of steam initially having a specific entropy of 1.6356 BTU/lbm-0R and an internal energy 1100.0 Btu/lbm undergo a constant temperature reversible non-flow process at 3000F such that the final entropy is 1.5150 BTU/lbm.0R and the internal energy is 1016.4 BTU/lbm. Find: The transferred heat, BTU The work done, ft-lbf