L10 - Machines & Efficiency Part 2

Formula for Q out in a T-s diagram

Q(out) = T2*(s2-s1)

What is the efficiency from Carnot cycle in T-s diagram?

n = 1 - T1/T2

What is the efficiency of the ideal otto cycle?

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

r = Vmax/Vmin = compression ratio

k = cp/cv

cp = heat capacity at constant pressure

cv = heat capacity at constant volume

V = Volume

What happens at each stage of the Ideal Stirling Cycle?

1-2 Isothermal Expansion: heat addition from external source, T = const

2-3 Regeneration: internal heat transfer form the working fluid to the regenerator V = const

3-4 Isothermal compression: heat rejection to the external sink, T = const

4-1 Regeneration: internal heat transfer from the regenerator back to the working fluid V = const

What is the Coefficient of Performance (COP) of the Ideal Refrigeration Cycle?

COP = 1/((TH/TL)-1)

TH - High temp

TL - Low temp

What is the COP of the Ideal Heat Pump?

COP = 1/(1-(Tl/TH))

What principle are refrigeration and heat pump cycles based on, and what does it allow?

They are based on the reversed Carnot cycle, which allows heat to be moved from a low temperature to a high temperature, but requires work input to do so