Heat and Mass Transfer Flashcards
Evaporation is also sometimes called as
Water distillation
The concentration of glycerin from a water solution by the application of heat is called
Evaporation
The total amount of evaporation and evaporator is capable of producing per unit of time
Capacity
When the pressure of the chamber is decreased, the boiling point of the solution inside the chamber will
Decrease
A heat transfer device that is used to liquefy vapors
Condenser
The temperature driving force of an evaporator is the difference between the condensing steam temperature and
Boiling point of the solution (T)
In a country where capital is scarce and energy cost is low, which is appropriate to install? Single or Multiple-Effect Evaporator?
Single-effect evaporator
What is called the fresh feed that enters at the coldest effect?
Backward feed
In commercial practice, the areas in all effects for a multiple effect evaporator are
Constant
A multiple effect evaporator ______the steam cost (increases or decreases?)
Decreases
___ of the vapor is recovered and reused in the multiple effect
evaporator.
Latent heat
It is the deposition and growth on body walls, and specially on
heating surfaces, of a material undergoing an irreversible chemical reaction in the evaporator.
Scaling
It is the formation of deposits other than salt or scale and maybe due to corrosion.
Fouling
Evaporation Chapter at Perry’s
Chapter 11
In industrial crystallization from a solution, the two phase mixture of mother liquor and crystals of all sizes, which occupies the crystallizer and is withdrawn as product is called
Magma
In practice, slow cooling maintaining a low level of supersaturation produces ___ crystals and fast cooling produces ___ crystals.
Large, small
It is the process by which crystalline bodies are created within a supersaturated fluid.
Nucleation
When a solution is cooled to produce a supersaturated solution and hence to cause crystallization, the heat that must be removed is the sum of the ____ necessary to cool the solution and the heat of crystallization
Sensible heat content
Element that is constant with heaters
Humidity
Element that is constant when dealing with adiabatic dryers
Wet bulb temperature
For adiabatic dryers, the exiting air always has a ___ humidity than the humidity of the entering air.
Greater/higher (H2 > H1 for adiabatic dryers)
Which of the following processes may always be regarded as a constant-humidity process?
a. cooling of air
b. air conditioning
c. water-cooling in a cooling tower
d. heating of air
D.
Wet bulb and dry bulb temperatures become identical at
100% saturation curve
Steady state temperature reached by a small amount of liquid evaporating into a large amount of unsaturated vapor-gas mixture is called?
Wet bulb temperature
The degrees of freedom associated with a humidification process is
2
Which of the following remains constant during sensible cooling process?
a. specific humidity
b. partial pressure of vapor
c. both a and b
d. neither a nor b
C.
During sensible cooling process
a. relative humidity decreases
b. relative humidity increases
c. wet bulb temperature increases
d. both b and c
B.
Also known as 100% relative humidity
Dew Point
To remove all the moisture from a wet solid requires exposure to
perfectly dry air
The portion of water in the wet solid that cannot be removed by the air in its contact is called
Equilibrium moisture content
Moisture contained by a substance in excess of the equilibrium moisture is called
Free moisture
When drying banana chips under the sun, the rate of drying is faster on a
a. slightly breezy day
b. cloudy day
c. calm day
d. hot and windy day
D.
The critical moisture content in case of drying indicates
Beginning of the falling-rate period
In drying at the falling rate period, the rate at which moisture is removed from the solid material
a. increases with time
b. remains constant
c. decreases with time
d. no more drying takes place
C.
Heat-sensitive materials like certain pharmaceuticals and food stuff can be dried by
Freeze-drying
Detergent solution is dried to a powder in a
Spray dryer
Calcium ammonium nitrate (a fertilizer) is dried in a
Rotary dryer
Rotary dryer cannot handle
Sticky materials
Another term for freeze-drying
Lyophilization
