BRIEF INTRODUCTION TO GAS POWER CYCLES AND VAPOR POWER CYCLES Power cycles mean those cycles which gives us net motion or electricity from heat supplied from some source in one form or the other. All power cycles are heat engine cycles. These operate on one cycle or the other. The efficiency depends on the manner […]
SOME IMPORTANT FACTS ABOUT ENTROPY Entropy is energy flow from order to disorder. Entropy is quantitative measure of disorder or randomness or chaos in a system. A highly ordered system has low entropy. Only change in entropy is of importance in any process which is expressed as dS=dQ/T In a cyclic process it is presented […]
PROPERTIES OF GASES Gas is one of four fundamental states of matter among a solid, liquid, gas and plasma. A pure gas may contain only one type of atoms like oxygen gas or may consists of more than one type of atoms like CO2, No2 and air. The molecules in a gas are far apart than […]
Highlights of general thermodynamic relations If f(x,y,z) =0 then (i) (∂x/∂y)z (∂y/∂z)x(∂z/∂x)y = –1 (∂y/∂x)z(∂x/∂y)z=(∂y/∂z)x(∂z/∂y)x =(∂z/∂x)y(∂x/∂z)y=1 Z=z(x,y), y =y(z,x) and x=x(y,z) If z = z(x,y) then dz = (∂z/∂x)y dx + (∂z/∂y)x dy For a continuous function ∂2z/∂x∂y =∂2z/∂y∂x Internal energy(U), Helmholtz energy (A), enthalpy (H) and Gibb’s free energy(G) are characteristic functions in thermodynamics.These […]
HIGHLIGHTS OF AVAILABILITY Availability is the maximum theoretical work which can be obtained by a heat engine. Since some heat is rejected in a heat engine, therefore recovery of maximum work is not possible. The work which cannot be recovered because of heat rejection to the surroundings is the unavailability. When heat is added to […]
HIGHLIGHTS —– SECOND LAW OF THERMODYNAMICS First law does not give the direction of the process as well as does not specify the quantity of conversion from one form of energy into another form of energy. A heat engine is one which converts heat energy into work or mechanical motion i.e. input is heat and […]
NOZZLE HIGHLIGHTS There is conversion of pressure into kinetic energy. There is work done in a nozzle. There is no energy transfer in a nozzle. Nozzle is considered horizontal unless otherwise stated i. e. Z1 = Z2 Convergent nozzle is used in industry as spray nozzles. Convergent nozzles are used in all aircrafts. Convergent –divergent […]
M C Q ON CONDENSERS A condenser condenses steam coming from the (a) Boiler (b) Super heater (c) Economizer (d) None ANS: (d) A condenser in a steam thermal plant (a) Decreases expansion ratio in the turbine (b) Decreases back pressure of steam (c) Increases condensation temperature (d) None ANS: (b) Hot water coming […]
M C Q ON ENTROPY OF STEAM/WATER Entropy of water is zero at (a) -400C (b) -200C (c) +400C (d) None ANS: (d) Change of entropy from temperature t1 to t2 is given by (a) ∫ds =∫ cp dT/T (b)∫ ds = ∫cv dT/T (c) ∫ds = ∫(cp dT/T + cv dT/T) (d) None ANS: (a) Entropy of wet steam is […]
M C Q ON THERMODYNAMIC AIR CYCLES A Carnot Cycle consists of (a) Two isobaric and two isentropic processes (b) Two isothermal and two isobaric processes (c) Two isothermal and two isentropic processes (d) None ANS: © Otto cycle is also known as (a) Constant pressure cycle (b) Constant volume cycle (c) Constant temperature cycle […]