Ch. 12 Flashcards
- A ___________ works on the principle of cool air contacting and removing heat from warm water.
a. shell and tube exchanger
b. circulating pump
c. cooling tower
d. evaporator
e. deaerator
c. cooling tower
- The hyperbolic cooling tower has the advantages of:
1) Low initial cost 2) Low power consumption 3) Long service life 4) Minimum maintenance
a. 1, 2, 3
b. 2, 3, 4
c. 1, 3, 4
d. 1, 2, 4
e. 1, 2, 3, 4
b. 2, 3, 4
- The cooling tower design in which the fan is least likely to ice up is:
a. Hyperbolic
b. Induced draft
c. Forced draft
d. Counterflow
e. Balance draft
b. Induced draft
- The cooling tower design in which the noise level from the fan is likely to be the lowest is:
a. Hyperbolic
b. Induced draft
c. Forced draft
d. Counterflow
e. Balance draft
b. Induced draft
- The double pipe heat exchanger belongs to the ___________ category.
a. regenerative
b. bent pipe
c. double tube
d. jacketed pipe
e. recuperative
e. recuperative
- The concentric pipe heat exchanger is suitable for high pressure service because ______________________.
a. the metal selected is stainless steel
b. the tubes, etc are small in dimension
c. the tubes are seamless construction
d. the unit is ASME stamped
e. None of the above
b. the tubes, etc are small in dimension
- The double pipe heat exchanger is a _______________ flow design.
a. concurrent
b. high differential temperature
c. high differential pressure
d. countercurrent
e. low differential temperature
d. countercurrent
- Concentric pipe heat exchanger fins can be attached by ________________.
a. mechanical insertion
b. casting
c. brazing
d. None of the above
e. All of the above
a. mechanical insertion
- The disadvantages of hairpin heat exchangers are:
1) Small heat transfer surface area 2) Not a flexible design 3) Cleaning is expensive 4) Each hairpin introduces more leak points 5) Non-standardized parts
a. 1, 3, 4
b. 1, 2, 3
c. 3, 4, 5
d. 1, 4, 5
e. 2, 4, 5
a. 1, 3, 4
- Which of the following is a disadvantage of a U-shaped shell and tube heat exchanger ____________________.
a. tubes are bent to a minimum radius
b. outer tubes are easily replaced
c. only one tube sheet
d. no differential expansion
e. good for high temperatures only
c. only one tube sheet
- U shaped shell and tube heat exchangers are not known for ______________________.
a. high heat transfer rates
b. high temperatures
c. high pressure
d. high differential expansion
e. All of the above
d. high differential expansion
- Fixed tube sheet shell and tube heat exchangers have ________________.
a. tube sheets that are contained with in the shell
b. little access for cleaning
c. tubes that are hard to plug
d. tube sheets not welded to the shell
e. None of the above
e. None of the above
- Fixed tube sheet chemical cleaning is used to clean ________________.
a. the inside of the tubes
b. the outside of the tubes
c. only the tubesheets
d. All of the above
e. None of the above
b. the outside of the tubes
- The floating tube sheet in the design allows for the _____________.
a. tube bundles to be easily removed
b. tube bundles to be easily repaired
c. different designs for different applications
d. different rates of expansion
e. use of different pressures and temperatures
d. different rates of expansion
- Reboilers are _________________________________.
a. an exchanger with process fluids on the tube inside
b. a boiler with steam on the outside of the tubes
c. an exchanger with steam inside the tubes
d. an exchanger that only reheats fluids to drive off vapours
e. a boiler that produces steam to heat vapours
c. an exchanger with steam inside the tubes
- What are the advantages of a Kettle type reboiler:
1) Provides flexibility 2) Rapid steamer 3) Gravity circulation 4) Easily accessible 5) Smaller size
a. 1, 2, 3
b. 2, 3, 5
c. 3, 4, 5
d. 1, 4, 5
e. 1, 3, 4
e. 1, 3, 4
- Horizontal thermosyphon reboilers require _________________.
a. a large vapor space
b. a small vapour space
c. a flooded shell
d. lots of heat transfer tubes
e. placement equal to the liquid level in the tower
c. a flooded shell
- Vertical thermosyphon reboiler often has _____________________.
a. heated liquid on the tube side
b. positioning next to a horizontal tower
c. steam on the tube side
d. liquid on the shell side
e. All of the above
a. heated liquid on the tube side
- In a horizontal thermosyphon reboiler, heat is controlled by _____________________________________.
a. adding more steam to the vessel
b. raising the vapour pressure on the shell
c. reducing the vapour pressure on the shell
d. raising the levels on the shell side
e. by varying the condensate level in the tube side
e. by varying the condensate level in the tube side
- Plate heat exchangers (PHE’s) use what to separate the two mediums a/an _______________________________.
a. rubber gaskets
b. different flow patterns
c. the plate corrugations
d. inlet and outlet piping
e. alternate plates
e. alternate plates
- Maximum cooling in PHE’s is maintained by _______________.
a. corrugating the plates
b. inlets and outlets at the plate corners
c. counter flowing the two streams
d. the thickness of the gaskets
e. thinness of the steel plates
b. inlets and outlets at the plate corners
- High heat transfer coefficients are maintained by ________________.
a. the use of numerous plates
b. the use of stainless steel
c. thinness of the gaskets
d. close spacing of the plates
e. All of the above
d. close spacing of the plates
- The use of compression bolts on PHE’s is to ________________.
a. tighten end plates
b. seal gaskets
c. compress the plate pack
d. decrease flow channel size
e. All of the above
e. All of the above
- Advantages of PHE’s include:
1) A rapid start up 2) Leakage easily detected 3) Enables use of low flow rates for erosion 4) Can cool toxic materials 5) Minimal heat loss
a. 1, 3, 4
b. 1, 2, 5
c. 2, 3, 4
d. 3, 4, 5
e. 1, 3, 5
e. 1, 3, 5
- Aerial Coolers are not used for _____________________.
a. cooling below ambient temperature
b. where water supply is limited
c. cooling in series with water coolers
d. cooling before water coolers
e. cooling where water fouling is a concern
a. cooling below ambient temperature
- Aerial coolers can be used when the liquid temperature is above:
a. 25°C
b. 35°C
c. 45°C
d. 55°C
e. 65°C
d. 55°C
- Aerial coolers are arranged in _____________________.
a. units
b. bays
c. bundles
d. banks
e. All of the above
e. All of the above
- In an Aerial cooler, how many bundles are in a bay _____________________.
a. one
b. two
c. one or more
d. two or more
e. three
c. one or more
- In an aerial cooler, a bay has how many fans:
a. one
b. one or more
c. two
d. two or more
e. three
d. two or more
- Temperatures in Aerial coolers are not controlled by ___________________.
a. stop, start of fans
b. induced draft fans
c. louvers open or closed
d. natural draft
e. forced draft
d. natural draft
- The most common configuration of an overhead aerial cooler is __________________________________.
a. vertical
b. A frame
c. V frame
d. horizontal
e. All of the above
d. horizontal
- Vertical arrangements of overhead aerial coolers are not used _____________________.
a. to take advantage of natural flow from top to bottom
b. to take the wind into consideration
c. in steam condensing applications
d. to keep the footprint small
e. in small packaged units
c. in steam condensing applications
- Overhead aerial condensers control very low freezing temperatures by _________________________.
a. closing louvers at the entrance
b. closing louvers at the exit
c. recirculating hot exhaust air
d. controlling the fan speed
e. shutting down all the fans
c. recirculating hot exhaust air
- The most common configuration of power generating plant steam condensing overhead aerial condensers are _____________________.
a. vertical
b. A frame
c. V frame
d. horizontal
e. All of the above
b. A frame
- The most commonly used method of increasing aerial cooler capacity is ______________________.
a. larger cooling fans
b. increase number of headers
c. increase the number of tube bundles
d. change the tube configuration
e. add fins to the tubes
e. add fins to the tubes
- When cooling fluids, atmospheric spray cooling towers do not depend on __________________________.
a. atmospheric conditions
b. wind drift
c. wind direction
d. tower fill
e. spray
d. tower fill
- The cooling process in atmospheric packed tower depends on _____________________________.
a. the production of fine droplets
b. the direction of the wind
c. air speed through the tower
d. the proper use of natural currents
e. the proper design of the louvres
a. the production of fine droplets
- The greatest savings in a Hyperbolic cooling tower is the _________________.
a. use of small amounts of packing
b. concrete structures last forever
c. savings in power
d. small footprint
e. reliability of the tower
c. savings in power
- In counterflow hyperbolic cooling towers, the cooling is most dependent on _________________________.
a. clean suction screens
b. density difference of the air
c. adequate water flow over the tower
d. cooling water drift
e. adequate air flows
b. density difference of the air
- Hyperbolic towers are used because ____________________.
a. they work in humid climates
b. they are extremely dependable
c. they are predictable in operation
d. they cost less to maintain
e. All of the above
e. All of the above
- Mechanical draft cooling towers are best used when _________________________.
a. they are in a dry climate
b. the intakes are unobstructed
c. they are close to the plant
d. there is no wind
e. the water flow in each cell is equal
a. they are in a dry climate
- Makeup to a cooling tower is best prevented by ____________________.
a. use of smaller fans
b. installation of tower packing
c. use of louvres
d. tower orientation
e. drift eliminators
e. drift eliminators
- Forced draft cooling towers do not use ______________________.
a. fill
b. spray
c. pack
d. louvres
e. drift eliminators
d. louvres
- Forced draft cooling towers are not suited to cold weather operation because ___________________.
a. the fans pump cold air
b. the exhausted hot air can not be recirculated
c. the cold inlet air causes freezing in the tower bottom
d. The drift eliminators freeze up and plug
e. None of the above
a. the fans pump cold air
- What is the greatest advantage of induced draft cooling towers?
a. The fans will not freeze
b. A smaller footprint-fits on an existing site
c. No recirculation of warm air
d. The induced draft cooling tower has the highest heat transfer
e. None of the above
c. No recirculation of warm air
- The greatest disadvantage of a counterflow induced draft tower is ___________.
a. the height of the tower
b. high horsepower electric motors
c. very complex path for the air flow
d. structure must be heavier to withstand the added weight
e. louvers can freeze and cause collapse of tower
b. high horsepower electric motors
- The greatest advantage of a crossflow cooling tower is _____________.
a. they are lower in height
b. they are larger and have a more stable footprint
c. they are smaller and have lighter fans
d. they have a very long air travel path
e. they are less prone to warm air recirculation
d. they have a very long air travel path
- The greatest influence on the operating efficiency of a cooling tower is ________________________.
a. the size of the fans
b. the height of the tower
c. the length of the air path
d. the amount of fill and spray
e. the contact time between air and water
e. the contact time between air and water
- The number one reason for fill in a cooling tower is to ___________________________.
a. break the water into small droplets
b. make the air path as tortuous as possible
c. increases the cooling capacity
d. lower the overall height of the tower
e. maximize air/water contact time
e. maximize air/water contact time
