##### Question

In: Mechanical Engineering

# ericsson cycle

Consider an ideal Ericsson cycle with air as the working ﬂuid executed in a steady-ﬂow system. Air is at a temperature of 270 degrees and a pressure of  120 kPa at the beginning of the isothermal compression process, during which 150 kJ/kg of heat is rejected. Heat transfer to air occurs at a temperature of 1200K. Determine

(a) the maximum pressure in the cycle

(b) the network output per unit mass of air

(c) the thermal eﬃciency of the cycle

## Solutions

##### Expert Solution An Ericsson cycle involves an isothermal heat-addition process and an isothermal heat-rejection process. the Ericsson cycle diﬀer from the Carnot cycle in that the two isentropic processes in the Carnot cycle are replaced by two constant-pressure regeneration processes. The cycle utilizes regeneration, a process during which heat is transferred to a thermal energy storage device called a regenerator during one part of the cycle and is transferred back to the working ﬂuid during another part of the cycle.

the p-v and T-s diagrams are shown in the diagram above and the processes are as follows:

1 → 2: isothermal compression,

2 → 3: isobaric heating in the combustion chamber,

3 → 4: isothermal expansion in the turbine,

4 → 1: isobaric heat transfer in surroundings

(A). The maximum pressure

the change in entropy can be given by:

S4-S3=qout/TL: (-150/300K

=-0.5KJ/Kg/K

The change of entropy can also be given by:

cp In(T4/T3) - R In(p4/p3)

from the T-s diagram, T3=T4=TL

the change in entropy can therefore be given by:

-0.5KJ/KG/K = Cp In1-(0.287kJ/KG/K) In( P4/P3)

-0.5KJ/KG/K = 0 - (0.287KJ/KG/K) In (P4/120Kpa)

p4 = 685.12Kpa which is our maximum pressure

(B)The net work output

Wnet = qin - qout

for an ideal reversible cycle, (qin/qout)=(TH/TL)

qin = qoutX(TH/TL)

= 150X(1200/300) = 600KJ/Kg

The net work is given by:

qin-qout

600KJ/kg - 150KJ/kg

Wnet = 450KJ/Kg

(c) The thermal efficiency of the cycle

thermal efficiency = 1 - (TL/TH)

= 1 - (300/1200)

0.75 = 75%

(a). maximum pressure = 685.12 Kpa

(b.). the net work output = 450kJ/Kg

(c). the thermal efficiency = 75%

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