Third Year Sem 2 Theory Flashcards
What is Dry Bulb Temperature?
The ambient air temperature. It is called “Dry Bulb” because the air temperature is indicated by a thermometer not affected by the moisture of the air. (Normal Temp of air)
What is the Wet Bulb Temp?
The adiabatic saturation temperature. The Wet Bulb temperature is always between the Dry Bulb temperature and the Dew Point
What is the Dew Point?
The Dew Point is the temperature at which water vapor starts to condense out of the air.
T.dp = Tsat@pv
What is the absolute / specific humidity?
Ratio of vapor mass/ dry air mass
Also w = 0.622 (Pv/Pa) or = 0.622(Pv/P-Pv)
What is relative Humidity?
Ratio of Mass of vapor / Mass of maximum moisture hold of air
O/ = Pv/Pg
What is theNusselt Number?
Indicated the improvement in convective heat transfer from a surface relative to conduction heat transfer.
What is the Prandtle Number?
Indicated relative magnitude of thermal to momentum diffusion. Also provides property dependence of fluid
What is the Reynolds Number?
Ratio of Inertia to Viscous effects. Also shows turbulent and mixing ability.
What is the Grashof Number?
It is the natural convention equivalent of the Re number and the flows ability to mix.
What are the three modes of heat transfer? Explain them!
Conduction - spontaneous from hot-cold wherever temp gradient
Convection - Transfer due to fluid motion
Radiation - Electromagnetic waves between separated surfaces
What is Fourier Law?
The rate of heat flowing in a given direction is proportional to the temp gradient in that direction and the area normal to the direction.
Q=-KA dT/dx
What’s the difference between natural and forced convection?
Natural (free) is when induces by buoyancy forces
Forced caused by external forces (fans or pumps etc)
What are the three things that happen to Radiation?
Absorbed (alpha), Transmitted (tauo), Reflected (rho)
What is a black body?
One which completely absorbs radiation! alpha = 1
Will shiny things have a high or low emissivity?
lower
What is Irradiation?
G is the combined total of radiation.
example alpha = G.absorbed rad / Incident Radiation (G)
Note: Alpha + Tauo + Rho = 1
What is an opaque body?
Tuao = 0 (transmitted radiation = 0)
What affects fin temp distribution and rate of decrease?
Its controlled by the convective heat loss relative to the conduction heat transfer. h and P determine the convective loss and K and A determine the conduction transfer.
Explain the basic principle and its limitations upon which ideal gas mixtures are treated to allow calculation of properties and application to the energy conservation equations.
Mixtures assumed independent and dont interact at molecular level. Mass/energy can simply add. Limitations as gas behaves non-ideal at high densities with low temp or high pressure.
What’s Daltons Law?
Pressure of a gas mixture is equal to the sum of pressures if each gas existed alone at the mixture temp and volume.
What’s Amagats Law?
Volume of a gas mixture is equal to the sum of volumes if each gas existed alone at the mixture temp and pressure.
What is the Rayliegh Number?
Product of Grashofand Prandtle
