FDSC 405 Engineering Exam 1 Flashcards
(14 cards)
Base Units
Unit of Length
Unit of Mass
Unit of Time
Unit of Thermodynamic Temp
Meter (m)
Kilogram (kg)
Second (s)
Kelvin (K)
Derived Units & dimentions
Newton (N) M (L/ t2)
Joule (J) (M L2/ t2)
Watt (W) (M L2 / t3)
Volt (V)
Ohm
Pascal (ML/ t2) / L2
Pascal second (M/Lt)
Quantity and units/bsae units
Force SI: kg m / s2
Energy, work, quantity of heat N m SI: kg m2 / s2
Power, radiant flux J/s & N-m/s SI: kg m2 /s3
Electrical potential, potential diff, electromotive force W/A SI: m2 kg s-3 A-1
Electrical resistance V/A SI: m2 kg s-3 A-2
Pressure/Stress (force/area) SI: N/m2
Viscosity Pa-s SI: kg/m-s
Area L2
Volume L3
Speed, velocity L/t
Acceleration L/t2
Density, mass density M/L3
Specific volume
m2
m3
m/s
m/s2
kg/m3
m3/kg
Dynamic viscosity
Moment of force
Surface tension
Power density, heat flux
Heat capacity, entropy
Specific heat capacity
Specific energy
Thermal conductivity
Energy density
Pa s SI: m-1 kg s-1
N m SI: m2 kg s-2
N/m SI: kg s-2
W/m2 SI: kg s-3
J/K SI: m2 kg s-2 K-1
J/(kg K) SI: m2 s-2 K-1
J/kg SI: m2 s-2
W/(m K) SI: m kg s-3 K-1
J/m3 SI: m-1 kg s-2
Temp F = 32+1.8(Temp C)
Temp C = (Temp F - 32) / 1.8
Temp K = Temp in C + 273
Dimensionless Ratio
Useful for expressing physical relationships
Fluid flow correlation
Heat transfer correlation
Independent of the system of units used for measurement
Specific gravity ( density of material divided by the density of water at the same temp)
Mass balance- conservation of mass
Cannot be created or destroyed but its composition can be altered
(Rate of mass entering a system) - (Rate of mass exiting a system) = (Rate of accumulation of mass within the system)
accumulation = 0
(rate of mass entering) = (rate of mass exiting)
Moisture content
wet basis 0-100%
MCwb (mass of moisture / mass of wet product) x 100%
Moisture content
dry basis 0 to > 100%
MC db (mass of moisture / mass of dry product) X 100%
Pressure measured relative to absolute vacuum is called absolute pressure
zero absolute pressure represents total vaccum
Pressure measured relative to atmospheric pressure is gauge pressure
negative gauge pressure represents vacuum
Pabsolute = Pgauge + Patmosphere
Static pressure exerted by a column of liquid
P = rho g h
P = Static pressure (Pa)
rho = density (kg/m3)
g = gravitational acceleration (9.8 m/s2)
h = Ht of liquid column (pressure head) (m)
Sensible heat: Changes temperature
Mass x Sp. heat x change in T
Latent heat
Changes phase Mass x heat of crystallization Mass x heat of vaporization
Ice + Heat of crystallization = liquid water at 0C
Liquid water at 0C + Sensible heat = saturated liquid water at 100C
Liquid water at 100C + Heat of vap. = Saturaded water vapor (steam) at 100C
Saturated water vapor (steam) at 100C + Sensible heat = Superheated steam
Enthalpy is the energy value (relative to refernce state)
Latent heat of crystallization = Enthalpy of saturated liquid - Enthalpy of ice
Latent heat of vaporization = Enthalpy of saturated vapor - Enthaply of saturated liquid
Energy Balance
Conservation of energy
In an open or closed system, total energy entering minus the energy exiting is equal to the rate of accumulation (temp increase)
In a open system, both mass and energy balances have to be carried out
Movement of material across the system boundary result in changes in both the mass and the energy values
In a closed system, only energy balance needs to be carried out
Viscosity
Rheology is the study of flow
Describes the resistance to flow
Flow is a kind of deformation
Different fluids exhibit different resistance to flow and they have different viscosities
Viscosity = Shear stress / Shear rate
- Shear stress = Force/ Area
- the shear stress acts parallel to the flow
- Shear rate
- Velocity gradient
- delta u / delta r = du/dr
