Engineering Applications of Control Volume-2 P M V Subbarao Professor Mechanical Engineering Department More Innovations for Extrasomatism…..

Steam Power Plant: A series of CVs in SSSF

Pumping of Incompressible Fluids Adiabatic pumping of a liquid is almost an Isothermal process!!

2 – 3 : Steam Generation : Isobaric Heating No work transfer, change in kinetic and potential energies are negligible Q CV

Oil Fired Steam Boiler

Turbine : Adiabatic Process No heat transfer. Change in kinetic and potential energies are negligible 3 4 T  ssuming a single fluid entering and leaving…

Diagram of Large Power Plant Turbine

HP Turbine Rotor

LP Turbine Rotor

Highly compressible flow through Turbine

Steam Power Plant: A series of CVs in SSSF

4 – 1 : Condenser : Isobaric Cooling : p 4 = p 1 No work transfer, change in kinetic and potential energies are negligible  Q CV   ssuming a single fluid entering and leaving…

Schematic for PC Power Plant with cooling Water from A River

Windcatcher (Bagdir)

Schematic for PC Power Plant with cooling tower

Air Cooled Condenser System

Net Heat and work Actions First law for a cycle:

Turbojet Engine: A Heat Engine with Single Phase – Non Pure Substance Q in Q out W out

Structure of A Domestic Refrigerator 1: Evaporator/Freezer 2: Condenser 3: Compressor 4 : Throttling Device

Thermodynamic Cycle of A Refrigerator

Simplified Diagram of A Refrigerator Throttling Valve Compressor All the parts are CVs working in USUF processes. Condenser : Transient Constant Pressure Cooling. Compressor : Transient adiabatic Compression. Throttling Device: Homogeneous and Transient Isoenthalpic process. Evaporator: Transient Constant Pressure Cooling.

Analysis of Uniform State Uniform Flow Devices

First Law for CV:Uniform State Uniform Flow Conservation of mass: Conservation of energy: Properties of CV are variant: Continuous Accumulation or/and depletion of mass of a CV. Continual Addition or removal of energy for a CV.

Salient Features of Process Rate of mass inflow  Rate mass outflow. The states of inflows and outflows are invariant although the mass flow rates may be time varying. Rate of Work done is variant. Rate of Heat transfer is variant. Change of state or process is both for the CV and Flows! The incoming fluid changes its state from inlet(at one time t 0 ) to exit (at time t 0 +  t) condition. A CV with USUF process is approximates as a homogeneous but variant device. The importance of time is very high!

CV following A USUF Process for time  t A change of state occurs in a CV with USUF due to change in time. A total change in a CV over time  t can be calculated using: Total change in mass of A CV during a time interval  t

Total change in energy of A CV during a time interval  t All parameters mentioned above are homogeneous and variant.

Let us now integrate this equation over time  t, during which time we have

First Law for A CV executing USUF for finite time

Throttling Devices Throttling devices are any kind of flow restricting devices. They cause large pressure drop in the fluid. The pressure drop in fluid is often accompanied by a large drop in temperature and rarely a raise in temperature. The magnitude of temperature drop or rise during a throttling process is governed by a property called Joule-Thomson Coefficient.

Throttling Valves Throttling: Reduces Pressure Common Assumptions: –SSSF –No work or heat transfer –Neglect changes in PE and KE Energy Balance: Throttling Valve 0 0

Isenthalpic (h = constant) Process Internal energy + Flow energy = Constant The fluids whose pv increases during throttling generate cooling effect. The fluids whose pv decreases during throttling generate cooling effect

The Joule-Thomson Experiment