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Thermal Engineering 1

by Abhishek Apoorv
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Abhishek Apoorv
Abhishek Apoorv
www.vidyarthiplus.com Paavai Institutions Department of MECH ME1251 THERMAL ENGINEERING UNIT I GAS POWER CYCLES UNIT-I 1. 1
www.vidyarthiplus.com Paavai Institutions Department of MECH CONTENTS TECHNICAL TERMS 1.1 The Otto Cycle 1.2 Diesel Cycle 1.3 Solved Problems 1.4 Dual Cycle 1.5 The Brayton Cycle 1.6 Actual PV diagram of four stroke engine 1.7 Solved Problems 1.8 Two Marks University Questions 1.9 University Essay Questions UNIT-I 1. 2
www.vidyarthiplus.com Paavai Institutions Department of MECH TECHNICAL TERMS: 1. Gas Power Cycles: Working fluid remains in the gaseous state through the cycle. Sometimes useful to study an idealised cycle in which internal irreversibilities and complexities are removed. Such cycles are called:Air Standard Cycles 2. The mean effective pressure (MEP) A fictitious pressure that, if it were applied to thepiston during the power stroke, would producethe same amount of net work as that produced during the actual cycle. 3. Thermodynamics: is the science of the relations between heat ,work and the properties of system 4. Boundary: System is a fixed and identifiable collection of matter enclosed by a real or imaginary surface which is impermeable to matter but which may change its shape or volume. The surface is called the boundary 5. Surroundings: Everything outside the system which has a direct bearing on the system's behaviour. 6. ExtensivePropety: Extensive properties are those whose value is the sum of the values for each subdivision of the system, eg mass, volume. 7. IntensivePropety: Properties are those which have a finite value as the size of the system approaches zero, eg pressure, temperature, etc. 8. Equilibrium: A system is in thermodynamic equilibrium if no tendency towards spontaneous change UNIT-I 1. 3
www.vidyarthiplus.com Paavai Institutions Department of MECH exists within the system. Energy transfers across the system disturb the equilibrium state of the system but may not shift the system significantly from its equilibrium state if carried out at low rates of change. I mentioned earlier that to define the properties of a system, they have to be uniform throughout the system. Therefore to define the state of system, the system must be in equilibrium. (Inequilibrium of course implies non-uniformity of one or more properties). 9. Process: A process is the description of what happens when a system changes its state by going through a succession of equilibrium states. 10. Cyclic Process: A cyclic process is one for which the initial and final states of the system are identical. 11. Isentropic process: is one in which for purposes of engineering analysis and calculation, one may assume that the process takes place from initiation to completion without an increase or decrease in the entropy of the system, i.e., the entropy of the system remains constant. 12. Isentropic flow: An isentropic flow is a flow that is both adiabatic and reversible. That is, no heat is added to the flow, and no energy transformations occur due to friction or dissipative effects. For an isentropic flow of a perfect gas, several relations can be derived to define the pressure, density and temperature along a streamline. 13. Adiabatic heating Adiabatic heating occurs when the pressure of a gas is increased from work done on it by its surroundings, e.g. a piston. Diesel engines rely on adiabatic heating during their compression UNIT-I 1. 4

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