7/23/2019 Tutorial 5 Reciprocating Compressor

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EMH332 APPLIED THERMODYNAMICS

 

TUTORIAL 5

RECIPROCATING COMPRESSORS

 

(SSL conditions: 25ºC; 101.325 kPa)

1. A reciprocating air compressor indces 5.!5 " 10#3 m$ o% air per c&c'e at SSL

conditions. % te de'i*er& pressre is !20 kPa+ ca'c'ate te ,ork trans%er per c&c'e i% te

compression and e"pansion processes are:#

  (a) re*ersi-'e po'&tropic+ n 1.2.

(-) re*ersi-'e adia-atic+ n 1./

(c) re*ersi-'e isoterma'

 

2. Air is to -e compressed trog a pressre ratio o% 10:1 %rom SSL conditions.

ind te po,er reired %or a %ree air de'i*er& (A) o% 0.05m$s. A'so %ind te rotationa'

speed i% te s,ept *o'me is 1/.5 " 10#3 m$. 4e c'earance *o'me is ! per cent o% te

s,ept *o'me+ and n 1.3 %or compression and e"pansion.

 

3. Air is compressed in a reciprocating compressor %rom SSL conditions to a

 pressre o% 0. 6Pa in one stage. 4e po'&tropic inde" o% compression and e"pansion is

1.3+ and te c'earance *o'me is / per cent o% te s,ept *o'me. Ca'c'ate te ,ork

trans%er per kg o% air de'i*ered and te eat trans%er dring compression and e"pansion

 per kg o% air de'i*ered.

/. A sing'e acting reciprocating compressor rnning at 2/0 7P6 de'i*ers 0.1m$s

A. n'et conditions are SSL and te de'i*er& pressre is /82 kPa. 4e c'earance

*o'me is 5 per cent o% te s,ept *o'me and te compression and re#e"pansion

 processes are considered re*ersi-'e and go*erned -& te 'a, p91.2  const. Ca'c'ate:

(a) te s,ept *o'me;

(-) te po,er reired to dri*e te compressor i% its mecanica' e%%icienc& is 85;

(c) te ma"imm pressre against ,ic te compressor co'd teoretica''& operate.

 

5. A sing'e stage reciprocating air compressor is reired to de'i*er m$ min A.

4e indction conditions are 5 kPa and 32 ºC. e'i*er& is at 0. 6Pa and te 'a, %or

te compression and e"pansion processes is: p91.3  constant. % te c'earance *o'me is

5 o% te s,ept *o'me+ ca'c'ate te teoretica' po,er and te *o'metric

e%%icienc&  -ased on SSL conditions.

7/23/2019 Tutorial 5 Reciprocating Compressor

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!. A tree stage reciprocating air compressor as a %ree air de'i*er& o% 2.83m$min

 -ased on SSL conditions. 4e indction pressre and temperatre are 8kPa and

32 ºC respecti*e'&. Ca'c'ate te idea' minimm po,er (stating te assmptions

reired) %or a de'i*er& pressre o% 6Pa and an inde" o% compression n 1.3.

etermine are te inter stage pressres.

. A %or stage reciprocating compressor takes in air at 1 -ar < 32 ºC and de'i*ers it

at 112-ar. 4e inde" o% compression %or eac stage is 1.28 and inter#coo'ing is sed so

tat te in'et temperatre is te same %or eac stage. 4e pressre ratios are cosen to

gi*e ea' ,ork per stage. etermine te *o'me o% air de'i*ered (at SSL conditions) per

k= ,ork inpt+ and te air de'i*er& temperatre.