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Heat Pumps > Gas > Flashcards

Gas Flashcards

1
Q

What are the 5 advantages of gas cycles

A

1 - clean and sometimes inert working fluid
2 - smaller surfaces needed for heat transfer
3 - working fluid can be lubricant
4 - turbine doesn’t have problems of wet vapour
5 - pressure is relatively low so less heavy piping

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2
Q

What are the ideal gas relations

A 
PV = m RT 
P = row RT
dh = cpdT
du = cv dT
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3
Q

What are the ideal gas relations for isentropic

A 
pv^k = constant 
TV ^(K-1) = constant 
T P (k-1/k) = constant
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4
Q

What is the work done by a compressor

A

W = m (he - hi)
= h2 - h1
= cp (T2 - T1)

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5
Q

What are the three types of compressor

A

1 - reciprocating (high P low fr)
2 - centrifugal (low P high fr)
3 - axial flow (similar to 2)

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6
Q

Why aren’t reciprocating compressor ideal

A
  • intake and exhaust valves for not open and close instantaneously
  • losses occur due to values and some heat transfer may take places
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7
Q

What is the equation for effectiveness of a compressor

A

n = (v1 - v4) / (v1 - v3)

the volume drawn in over the displacement volume

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8
Q

What is the broke

A

diameter of piston

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9
Q

What is the stroke

A

distance the piston travels in

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10
Q

What happens at the TDC

A

volume occupied by air is min

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11
Q

What happens at the BDC

A

volume occupied by air is max

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12
Q

What is the compassion ratio for an engine

A

r = VBDC/ VTDC

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13
Q

What is the work done by the cycle

A

W(cycle) = (MEP) (Vbdc- Vtdc)

MEP = mean effective pressure

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14
Q

What are the stages of an otto cycle

A

0 - 1 pision at tab and moved to bcc, air sucked in
1 -2 at bcc valve closed and poison impressed until tdc
2 -3 ignition occurs, T and P increase
3 -4 combustion products expand isentropicaly to bcc
4 - 1 exhaust valve opens P decrease and V constant

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15
Q

What is the heat transfer in an out of an otto cycle

A

Q in = mcv (T3 - T2)

Q out = mcv (T4 - T1)

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16
Q

What is the effciceny of an otto cycle

A 
n = W net/ Qin = 1 - Q out/Q in 
n = 1 - 1/(r^(k-1))
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17
Q

What are the stages in the diesel cycle

A

1 - 2 isentropic compression
2 - 3 isobaric heat addition
3 - 4 combustion terminated, expansion occurs isentropicaly
4 -1 contact volume, heat rejection.

18
Q

What is the efficiency for the diesel cycle

A

n = 1 - (1/r^(k-1) x ((rc^k - 1)/k(rc-1))

19
Q

What is the efficiency of the sterling and Ericsson cycles

A

n = 1 - Ql/Qh = 1 - Tl/Th

20
Q

What is a gas turbine?

A
  • used to produce power

- can operate on a closed or open system

21
Q

What is an open cycle

A

air enters compressor, passes through constant pressure combustion chamber, through turbine and into atmosphere

22
Q

What is a closed cycle

A

combustion chamber replaced with heat exchanger and energy enters from exterior source
additional heat exchanger transfers heat from the cycle so that working fluid returns to initial state

23
Q

What factors effect the efficiency of the Baryton cycle

A

1 - irreversibility in compressor and turbine
2 - pressure drop in flow passages and combustion/ heat exchanger
3 - work required by compressor

24
Q

what is the efficiency of a Baryton cycle

A

n = 1 - rp^(1-k/k) where rp - P2/P1

25
Q

What is the efficiency of the regenerative gas cycle

A

n = (W turb - W comp)/q in

= 1 - T1/T4 x rp^(k-1/k)

26
Q

What is a CHP

A

system where both electrical power and heat are itlized

27
Q

What are turbojet engines

A

reaction engin with turbine only extracting sufficient energy to drive compressor,
high speed air craft

28
Q

What are turbofan engines

A

reaction engine, part of air entering gets compressed fully

lower noise and better fuel consumption so used for civilian air craft

29
Q

What are turboprop engines

A

use exhaust stream to power additional power turbine which drive a propeller

30
Q

what are turbo shaft engines

A

like turbo prop, power turbine couples to an output shaft absorbing as much energy in gas stream, helicopters

31
Q

What does V thrust equal?

A

V thrust = V6 - V1

32
Q

What is the mole fraction

A

yi = Ni /N

33
Q

What is the mass fraction

A

mfi = mi / m

34
Q

What is the mean molecular weight of a mixture

A

m = M/ N

35
Q

What is the mixtures gas constant

A

R = R bar / m

36
Q

What is the amigo model

A
  • treats each component as though is exists separately at the same pressure and temperature of mixture
  • total volume is the sum of the comments
37
Q

What is the dalton model

A

-each comment occupies the same volume and has the same temperature as mixture. -total pressure is the sum of component pressure

38
Q

what is the relative humidity ratio for absolute humidity?

A

w = mv/ma

where mv is mass of water vapour, ma is mass of dry air

39
Q

what is the relative humidity ratio

A

phi = mv/mg

where mv is mass of water vapour, mg is max mass of vapour in air at same temp

40
Q

What is the drew point temperature

A

temperature at which vapour condenses when its cooled at constant pressure

41
Q

Draw a ts and pv graph for stringing and erricson cycle

A

.

42
Q

Draw a ts and pv graph for barytone cycle regenerative cycle

A

.

Heat Pumps (2 decks)

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