2. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 1 A single-stage reciprocating compressor takes 1m 3 of air per minute at 1.013 bar and 15 0 C and delivers it at 7 bar. Assuming that the law of compression is PV 1.35 = constant, and the clearance is negligible, calculate the indicated power. Mass of air delivered per min. : Delivery Temperature : Indicated Work : … .ANS

3. Example 2 If the compressor in last example is driven at 300 rpm and is a single acting, single-cylinder machine, calculate the cylinder bore required, assuming a stoke to bore ration of 1.5:1.Calculate the power of the motor required to drive the compressor if the mechanical efficiency of the compressor is 85 % and that of the motor transmission is 90%. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Volume dealt with per min. at inlet = 1 m 3 /min Hence, Vol. drawn in per cycle = 1/300 = 0.00333 m3/cycle = Cylinder Volume Thus, cylinder bore, D = 0.1414 m or 141.4 mm … .ANS Power input to the compressor = … .ANS

5. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 3….contd P 1 P 2 V 1 V 2 3 2 4 1 Heat Transferred : … .ANS

6. Example 4 Following data relate to a performance test of a single-acting 14 cm X 10 cm reciprocating compressor: Suction Pressure =1 bar Suction temperature = 20 0 C Discharge Pressure = 6 bar Discharge temperature = 180 0 C Speed of compressor = 1200 rpm Shaft Power = 6.25 kW Mass of air delivered =1.7 kg/min Calculate the following: 1. The actual volumetric efficiency. 4. The indicated power. 2. The isothermal efficiency. 5. The mechanical efficiency. 3. The overall isothermal efficiency. ME0223 SEM-IV Applied Thermodynamics & Heat Engines P 1 P 2 V 1 V 2 3 2 4 1 … .for single-acting compressor

7. Example 4….contd ME0223 SEM-IV Applied Thermodynamics & Heat Engines P 1 P 2 V 1 V 2 3 2 4 1 … .ANS Indicated Power : … .ANS

8. Example 4….contd ME0223 SEM-IV Applied Thermodynamics & Heat Engines P 1 P 2 V 1 V 2 3 2 4 1 Isothermal Power : … .ANS … .ANS … .ANS

9. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 5 A single-stage double-acing air compressor is required to deliver 14 m 3 of air per min measured at 1.013 bar and 15 O C. the delivery pressure is 7 bar and the speed 300 rpm. Take the clearance volume as 5 % of swept volume with the compression and expansion index of n = 1.3. Calculate: 1. Swept volume of the cylinder 2. Indicated power 3. Delivery temperature. Swept Vol. V s = V 1 – V 3 = V 1 – V c = V 1 – 0.05 V s Vol. induced per cycle = ( V 1 – V 4 ) P 1 =1.013 bar P 2 =7 bar V 1 V 4 6 2 5 1 3 4 V 3 Swept Volume, V 1 -V 3 =V s V 3 =V c = 0.05 V s 288 K V 1 = 1.05 V s

10. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 5….contd V 4 = 4.423 V 3 = 4.423 X 1.05 V s = 0.221 V s (V 1 – V 4 ) = 1.05 V s – 0.221 V s = 0.0233 m 3 … .ANS Swept Volume, Delivery Temperature : … .ANS Indicated Power : … .ANS

11. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 6 A four-cylinder double-acting compressor is required to compress 30 m 3 / min of air at 1 bar and 27 0 C to a pressure of 16 bar. Determine the size of motor required and cylinder dimensions if the following data is given : Speed of compressor = 320 rpm. Clearance volume = 4 % Stroke : Bore ratio = 1.2 Mechanical Efficiency = 82 % Index = 1.32 Assume no pressure change in suction valves and air gets heated by 12 0 C during suction stroke. Net Work done : … .ANS Motor Power : … .ANS

12. Example 6….contd ME0223 SEM-IV Applied Thermodynamics & Heat Engines Vol. Efficiency : Swept Vol. per cylinder : … .ANS … .ANS

13. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 7 Air at 103 kPa and 27 0 C is drawn in L.P. cylinder of a two-stage air compressor and is isentropically compressed to 700 kPa. The air is then cooled at constant pressure at 37 0 C in an intercooler and is then again compressed isentropically to 4 MPa in the H.P. cylinder, and is deliverer at this pressure. Determine the power required to run the compressor if it has to deliver 30 m 3 of air per hour measured at inlet conditions. P 1 = 103 kPa P 3 = 4 MPa 3 2 1 P 2 = 700 kPa L.P. H.P. Volume Mass of air delivered per min. : Temperature for compression process 1-2’ : Temperature for compression process 2-3 :

14. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 7….contd Work required to run the compressor : … .ANS

15. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 8 A trial on a two-stage single-acting reciprocating compressor gave the following data : Free air delivered =6 m 3 /min Delivery Pr. = 40 bar Atm. Pr. and Temp. = 1 bar 27 ºC Speed = 400 rpm Intermediate Pr. = 6 bar Temp. at inlet to 2 nd stage = 27 ºC Law of Compression = PV 1.3 = C Mechanical Efficiency = 80 % Stroke of L.P. = Stroke of H.P. = Diameter of L.P. P 1 = 1 bar P 3 = 40 bar 3 2 1 P 2 = 6 bar L.P. H.P. Volume Assuming Vol. Efficiency of 100 % , … .ANS Swept Vol. of H.P. cylinder = Vol. of air at 6 bar, 27 ºC … .ANS

16. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 8….contd Indicated Work : … .ANS

18. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 9….contd Power Required : … .ANS Mass of air handled : Delivery Temperature : Heat rejected in Intercooler : … .ANS

19. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 10 A two-stage air compressor with complete intercooling delivers air to the mains at a pressure of 30 bar, the suction conditions being 1 bar and 15 0 C. if both cylinders have same stroke, find the ratio of cylinder diameter for the efficiency of compression to be maximum. Assume index of compression to be 1.3. P 1 P 3 3 2 1 P 2 L.P. H.P. Volume 2’ 5 6 4 For max. efficiency :

20. ME0223 SEM-IV Applied Thermodynamics & Heat Engines Example 10 Delivery Temperature : For Const. Pr. Process 2 – 2’ : Thus, we get : Hence : … .ANS