2.3 Thermodynamics Flashcards
Name the 3 types of thermometers
- Bulb thermometer
- Bimetallic thermometer
- Thermistor
What are thermocouples used for
Measure high temperatures
Where would a Bimetallic Thermometer be used
Fire detection system & OAT
What is a Thermistor
A device to measure temperature that changes its electrical resistance with changes in temperature. Most common device
3 scales of tempeature
Deg Celcius (C)
Kelvin (K)
Deg Farenheit (F)
Formula to convert Deg F to Deg C
deg C = 5 / 9 (F - 32)
(50 - 32) x 5 / 9 = 10 deg C
Formula to convert Deg C to Deg F
deg F = 9 / 5 C + 32
9 / 5 x 50 + 32 = 122 deg F
9/5 = 1.8
Temperature at which deg C & deg F are the same
-40 deg
Formula to convert Kelvin to deg C
K = deg C + 273.15
What is zero Kelvin otherwise known as
Absolute Zero. Whare all molecular movement would stop
Formula for Specific Heat
c = Q / m x /\T or Heat added Q = m x c x /\T
- c = specific heat {j/kg K}
- Q = heat energy added {J}
- m = mass {kg}
- /\T = change in temp {K}
Formula for Heat Capacity
C = Q / /\T or Haet added Q = C x /\T
* C = heat capacity (J/K)
* Q = heat energy added (J)
* /\T = change in temp (K)
Name the 3 types of Heat transfer
Conduction, Radiation, Convection
The only method of heat transfer in solids is
Conduction, however it also occurs in liquids
Heat transfer from one part of the fluid to another, is called?
Convection
Formula for Linear Expansion
/\L = aLo/\T
* /\L = change in length (m)
* a = coefficient of linear expansion
* Lo = original length
* /\T = change in temperature
Formula for Area Expansion
/\A = 2aAo/\T
* Ao = original area of body (m^2)
* a = coefficient of linear thermal expansion
* /\A - change in area of the body (m^2)
* /\T = change in temperature (deg C)
Formula for Volumetric Expansion
/\V = 3aVo/\T
* Vo = original volume of the body (m^3)
* a = coefficient of linear thermal expansion
* /\V = change in volume of the body(m^3)
* /\T = change in Temperature (deg C)
Describe the first law of thermodynamics?
Energy can neither be created nor destroyed but can only be transformed from one form to another. In simple terms: Energy in = Energy out
Formula for Thermodynamics first law
Q = /\U + W or W = Q - /\U or /\U = Q - W
* Q = heat energy added (J)
* W = work done by the gas (J)
* /\U = change in internal energy (J)
2nd Law of Themodynamics
The second law of thermodynamics states that the total energy output (as produced by a machine) is equal to the amount of heat supplied.
Formula for change in Entropy
/\S = Q / T
* /\S = change in entropy (J/K)
* Q = heat energy absorbed (J)
* T = temperature (K)
There are two types of thermodynamic cycles: open and closed. Each cycle has the same five basic elements. What are they?
Working substance – a medium that receives, stores and transports the energy.
Heat source – supplies thermal energy to the working fluid.
Heat receiver – absorbs the heat (or thermal energy) from the working substance.
Pump – moves the working substance from the low-pressure side to the high-pressure side of the cycle.
Engine – converts the thermal energy to work in mechanical energy.
There are three main processes in the engine working cycle during which changes in temperature, pressure, or density occur:
- Compression
- Combustion
- Expansion