1-stage Compressor

Question 1

Compressor Work if S=C and PV^n = C, Wc

Answer 1

use k if isentropic, use n if polytropic

(nP1V1’)/(n-1) [(P2/P1)^(n-1)/n -1]

Question 2

Compressor Work if T=C, Wc

Answer 2

P1V1’ ln [P2/P1]

mRT1 ln (P2/P1)

Question 3

Volumetric Efficiency, ƞ_v

Answer 3

V1’/V_D

(V1-V4)/(V1-V3)

1+c-c(P2/P1)^1/n

c = V_c/V_D

Question 4

Piston Displacement, V_D

Answer 4

LANƞaƞc

Question 5

Piston Speed, V_P

Answer 5

2LN

Question 6

Mean Effective Pressure, mep

Answer 6

W_c/V_D

Question 7

Heat Loss, Q_Loss using energy balance

Answer 7

Wc+h1+KE1 = Q_Loss + h2 + KE2

Wc = (h2-h1) + (KE2-KE1) + Q_Loss

Wc = m_g * C_pg * (T2-T1)

Question 8

Air-cooled compressor, Q_LOSS

Answer 8

m_a C_pa (t2-t1)
m_a (h2-h1)

Question 9

Water-cooled compressor, Q_LOSS

Answer 9

m_w C_pw (t2-t1)
m_w (h2-h1)

Question 10

Compressor efficiency, ƞ_c

Answer 10

ideal work/actual work

W_ideal/W_indicated

Question 11

mechanical efficiency, ƞ_m

Answer 11

W_indicated/shaft work

W_indicated/BP

BHP = IHP + FHP

FHP = 0.105(V_D)^0.75 in HP

V_D = piston displacement in cfm

Question 12

Overall efficiency, ƞ_o

Answer 12

W_ideal/BP
ƞ_m*ƞ_c