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We are adding Thermal Engineering 1 study Notes, Diploma Thermal Engineering 1 answers for N Scheme important Questions and answers for the Unit 1 – 14 marks. Check the link below to download Thermal Engineering 1 pdf for Diploma in Mechanical 3rd sem
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Thermal Engineering 1 Scheme: N Semester: 3
Unit – 1, Basic of Thermodynamics and thermodynamic Processes of Perfect Gases
Note: all the questions carries 7 marks only ( Part – B – 14 Marks – Can split into 7 marks)
Important theory questions – 7 marks
1. What is Pressure? Explain Gauge Pressure and Absolute Pressure.
Pressure
Pressure is defined as the normal force per unit area of the surface. The unit of pressure depends upon the units of force and area. Its unit is N/m2 , Pascal (Pa) and bar. It is denoted by ‘p’.
Mathematically, p = 𝑭 𝑨
Note: 1 bar = 1×105 N/m2 = 100 kN/m2 = 0.1 MN/ m2 . 1Pa = 1 N/m2 1kPa= 1 kN/m2
Gauge pressure and Absolute pressure
The reading of the pressure gage is known as gauge pressure, while the actual pressure is called absolute pressure. Mathematically, For pressures above atmospheric,
Absolute pressure = Atmospheric pressure + Gauge pressure
For pressures below atmospheric, the gauge pressure will be negative. This negative pressure is known as vacuum pressure.
Mathematically, Absolute pressure = Atmospheric pressure – Vacuum pressure
Note:
Pabs = Patm + Pg
Pabs = Patm – Pv
Patm= 760 mm of Hg = 1.01325 bar = 1.01325 x 105 N/m2 = 101.325 kN/m2
2. What is Temperature? Explain STP & NTP Conditions?
Temperature
Temperature is the amount of heat in a system.
Temperature is defined as the degree of hotness or coldness of a body. The unit of temperature measurement is degree. It is denoted by ‘T’.
When the heat is added to a body and it becomes hotter, its temperature is said to rise.
When a body cools down, its temperature is said to fall.
Absolute Temperature
Absolute zero temperature is taken as -273°C. The temperatures measured from this zero are called absolute temperatures. The absolute temperature in Celsius scale is called degree Kelvin (K).
Mathematically,
Absolute Temperature in K = Temperature in °C + 273
Standard Temperature and Pressure (S.T.P)
The temperature and pressure of any gas, under standard atmospheric conditions, is taken as 15°C (288 K) and 760 mm of Hg respectively pressure are termed as Standard temperature and pressure
Normal Temperature and Pressure (N.T.P)
The conditions of temperature and pressure at 0°C (273 K) temperature and 760 mm of Hg pressure are termed as normal temperature and pressure
- Explain Thermodynamic system, Surroundings and Boundary. What are the different types of thermodynamic system?
Thermodynamic system:
The thermodynamic system (simply known as system) may be defined as a definite area or a space where some thermodynamic process is taking place.
It is a region where our attention is focussed for studying a thermodynamic process.
A little observation will show that a thermodynamic system has its boundaries and anything outside the boundaries is called its surroundings as shown in fig.
These boundaries may be fixed like that of a tank enclosing a certain mass of compressed gas, or movable like boundary of a certain volume of liquid in a pipe line.
Surroundings
Everything outside of the system which affects the behavior of the system is called surroundings.
Boundary
The system and surroundings are separated by the system boundary. It may be real or imaginary.
Types of thermodynamic systems:
- Closed system(Non flow process)
- Open system (flow process)
- Isolated system
- Closed system: In a closed system or non-flow system, Energy crosses the system boundary in the form of heat and work, but there is no mass transfer. Example: Gas contained in the cylinder
- Open system: In an open system or flow system or control volume system, both energy and mass (heat and work) cross the boundary of the system Examples: Air compressor, flow through nozzles and turbines
- Isolated system: In an isolated system no mass and no energy crosses the boundary of the system. Example: Thermal flask and insulated gas container
4. Explain Intensive and Extensive Properties
Properties of System:
The state of the system may be identified or described by certain observable quantities such as volume, temperature, pressure and density etc.All the quantities which identify the state of the system are called properties.
There are two sorts of property: 1. Intensive properties 2. Extensive properties
Intensive or Intrinsic properties: These are the properties which are independent of the mass of the system. Examples: Temperature, pressure, velocity, density, specific heat etc…
Extensive or Extrinsic properties: These are the properties which are dependent on the mass of the system Examples: volume / mass = specific volume Enthalpy / mass = Specific enthalpy
- What is Point function and Path Functions?
Point functions:
The quantities which are independent on the process of path followed by the system are known as point functions.
Path Function:
The quantities which are dependent on the process or path followed by the system are known as path functions.
1 – 2 = point funtion
1- a – 2 or 2 – c -1 or 1 –b- 2= path function
- Derive the Characteristic gas equation
It is modified form of general gas equation.
If the volume (V) in the general gas equation is taken as that of 1 kg of gas (known as its specific volume, and denoted by Vs ) , then the constant C (in the general gas equation) is represented by another constant R (in the characteristic equation of gas)
- Derive the relationship between Specific heats and Gas constant.
Relationship between specific heats and gas constant
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