Energy thermodynamic cycles

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  • The fuel can be Natural gas or synthetic fuel gas.
    It consists of two isoentropic and two isobaric processes
  • Energy thermodynamic cycles

    1. 1. THERMODYNAMIC CYCLES HEAT ENGINES&HEAT PUMPS EFFICIENCY AND COEFFICIENT OF PERFORMANCE PRESENTED BY:SUJI.S.K
    2. 2. THERMODYNAMIC CYCLES A thermodynamic cycle is a series of thermodynamic processes transferring heat and work, while varying pressure, temperature and other state variables, eventually returning a system to its initial state
    3. 3.  A minimum of 3 such processes are required to construct a cycle.  All processes need not have work interactions (eg: isochoric)  All processes need not involve heat interactions either (eg: adiabatic process).
    4. 4. “When a system undergoes a thermodynamic cycle then the net heat supplied to the system from the surroundings is equal to the net work done by the system on its surroundings” ΣQsupplied-ΣQrejected= Wnet  The efficiency of the cycle is defined as η= Wnet/ΣQsuppied
    5. 5. Carnot Cycle It consists of two isotherms and two adiabatics
    6. 6. Carnot Cycle (contd..) • Carnot cycle is the one with which all other cycles are compared. • η= Wnet/ΣQ supplied = ΣQsupplied-ΣQrejected/ΣQsupplied =Q41-Q32/Q41 =(T1-T2)/T1 Carnot efficiency of (T1-T2)/T1 is the best we can get for any cycle operating between two fixed temperatures.
    7. 7. OTTO CYCLE It consists of two isochores and two adiabatics
    8. 8. OTTO CYCLE(contd..) There is no heat interaction during 1-2 and 3-4 •Heat is added during constant volume heating (2-3) Q23= Cv(T3-T2) •Heat is rejected during constant volume cooling(4-1) Q14= Cv(T4-T1) • η = Wnet/ΣQ supplied = ΣQsupplied-ΣQrejected/ΣQsupplied =(Q23-Q14)/Q23= 1 -[(T4-T1) / (T3-T2)]
    9. 9. Diesel Cycle Diesel cycle consists of two isoentropic, isochoric and one isobaric process one
    10. 10. Diesel cycle(contd..) Q23=mCp(T3-T2) Q14=mCv(T4-T1) η = Wnet/ΣQ supplied = ΣQsupplied-ΣQrejected/ΣQsupplied =(Q23-Q14)/Q23 = 1 –(1/γ)[(T4-T1) / (T3-T2)]
    11. 11. Brayton Cycle The fuel can be Natural gas or synthetic fuel gas. It consists of two isoentropic and two isobaric processes
    12. 12. Reversible Cycle • A cycle consisting of all reversible processes is a reversible cycle. Even one of the processes is irreversible, the cycle ceases to be reversible. Otto, Carnot and Brayton cycles are all reversible.
    13. 13. • A reversible cycle with clockwise processes produces work with a given heat input and are known as power cycles. The same while operating with counter clockwise processes will reject the same heat with the same work as input and are known as heat pump cycles .
    14. 14. HEAT ENGINE • A device which produces work by transferring heat from a warmer to a cooler body is called a heat pump.
    15. 15. Carnot Engine • Carnot engine has one Q +ve process and one Q -veprocess. This engine has a single heat source at T1and a single sink at T2. If Q +ve> Q -ve; W will be +ve. It is a heat engine
    16. 16. Heat pump • A device which transfers heat from a cooler to a warmer body (by receiving energy) is called a heat pump. • A refrigerator is a special case of heat pump. • Just as efficiency for a heat engine, for a heat pump the coefficient of performance (COP) is a measure of how well it isdoing the job.
    17. 17. Carnot Cycle for a Refrigerator/heat Pump » TH=T1, TC=T2
    18. 18. Heat Pump (contd…) • In a heat pump the entity of interest is Q1. COP HP = Q1/W • In a refrigerator the entity of interest is Q2. COP R = Q2/W • NOTE: η, COPHPCOP R are all positive numbers, • The highest COPHP obtainable will be T1/(T1-T2)
    19. 19. •An irreversible engine can’t produce more work than a reversible one. •An irreversible heat pump will always need more work than a reversible heat pump. •An irreversible expansion will produce less work than a reversible expansion •An irreversible compression will need more work than a reversible compression

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