Transcript INTRODUCTON
Ch:1 INTRODUCTON PRIME MOVERS DEFINATION Prime movers is a device which use the energy from natural sources and convert in to mechanical works. Before the development of machine man had to depend on his own physical strength and on animal, mainly horse. So when was the mechanical system was invented at that time unit of power is horse power. Technically, it is a group of machines that transform energy from thermal, electrical, or pressure into mechanical form for use in different sources for some mechanical work. Engines and turbines are examples. Sources of energy used by Prime movers. Burning of fuels: It is the most important topics of energy. heat energy is librated when fuel is burnt. Different fuels have different calorific value based on on heat is given out. The heat energy converted in to mechanical work by using heat energy. River water: River water is another useful and widely used another sources. Water potential energy convert in to the kinetic energy when it reaches the prime movers. River water is also used to generate the steam in the boiler and its used in the steam turbine. Atoms: Using atoms as a source of energy is recent development. It is also widely use energy source. heat energy produce by fission of the atoms. Wind and solar energy: It is the renewable energy sources of energy. this is the freely available energy sources. Sources of energy to run prime movers Sources of energy Non Thermal Thermal water fuel Nuclear External combustion engine Reciprocating steam engine Geothermal Tidal power Bio-gas wind Solar energy Internal combustion engine Reciprocating I.C engine Stem turbine Closed cycle gas turbine Open cycle gas turbine Definitions Force : A body of mass m subject to a force F undergoes an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force i.e., F = ma. Weight: It is the force exerted by gravity w = m x g (N) Weight of an object is not constant. It depends on the gravitational force Mass : Mass is the quantity of matter. It depending force acting on it. Mass of the body is same weather the body is on the moon or the earth. Pressure: Pressure is the ratio of force to the surface area over which it is exerted. Pressure : Force (n) 2 Area (mm ) n 1 pascal 1 mm 2 Breaker power : Power delivered by the engine is break power. Energy : It is defined as the capacity of doing work. Energy conservation Energy cannot be destroyed or created it can change from its State. This conversion may be completed or partial High grade energy: Energy that can completely converted in to the work. Low grade energy: energy of which only certain portion can be converted in to the work. Specific heat : energy is required to rise the temperature of unit mass of a substance by one degree is know as its specific heat. Which is denoted by (c) Q m C T C Q( KJ ) m( Kg ) T ( K ) Unit of specific heat is kj / kg k Melting point: The point it where the solid converted in to the liquid when heat is added. Boiling point: The point it where the liquid converted in to the vapour when heat is added. Critical point: It is the temperature above which only one phase is existing. i.e vapour Tripple point It is the temperature at which all the three phases solid, liquid and vapour are in equilibrium. Below this point only two phase are existing solid and vapour. solid is directly converted into the vapour. This process called sublimation Types of systems Open system a system where matter or energy can flow into and/or out of the system. Heat mass Closed system : where energy can enter or leave but matter may not. i.e pressure cooker Isolated system : In these system energy and mass can not across the boundary. i.e thermos flask Enthalpy : It is the combination of the (u+pv) it is defined enthalpy and is given symbol. it is denote by (H). H= u + pv Efficiencies Brake power of an engine (b.p): It is the power available for work at the output shaft of the engine. Indicated power (i.p) : It is the power developed in its engine cylinder Friction power : i.p = b.p + Friction power Mechanical efficiency : braekpower mech indicatedpower Steady flow energy equation (SFEE) Enter P1 v1 w U1 c1 p1v1 EXIT z1 P2 V2 entery q Datum line z2 U2 C2 P1 and p2 – Pressure at the entry and exit. V1 and v2 – volumes at the enter and exit m3 / kg U1 and u2 – internal energy at the entry and exit kj/kg. C1 an c2 – velocity at the entry and exit m/s Potential energy : This is because of the height of the fluid from the datum. P.E = z kj/kg Kinematics energy : it is the energy because of the motion of the fluid. K.E = 1 2 c kj / kg 2 gc Internal energy : Internal Energy is the energy stored in a system at the molecular Level. Which is denoted by the (u) and the unit is kj/kg Flow and displacement work : Flow work at the entry = p1v1 Flow work at exit = p2v2 Heat received by the system = q kj/kg External work done by the system = w kj/kg. 2 2 c c z1 u1 p1v1 1 q z2 u2 p2v2 2 w 2 gc 2 gc By the law of conservation of energy we have Total energy entering at the system = Total energy leaving the system 2 2 c1 c2 z1 u1 p1v1 q z2 u2 p2v2 w 2 gc 2 gc First Law of Thermodynamics : The first law of thermodynamics is often called the Law of Conservation of Energy. This law suggests that energy can be transferred from one system to another in many forms. Also, it can not be created or destroyed. Zeroth law of thermodynamics: If two bodies are thermal equilibrium with third body and they are also thermal equilibrium with each other . Second law of thermodynamics: Two statement for 2nd law of thermodynamics 1. Kelvin Plank Statement. 2. Clausius statement. Kelvin Plank Statement : it is impossible for any device that operate on a cycle to receive heat from a single source and produce a net amount of work. Clausius statement : It is impossible to construct a device that operates in a cycle and produce no effect other than the transfer of heat a lower temp. body to a higher temp. body.