Exam (elaborations)
RETA INDUSTRIAL REFRIGERATION BOOK 2
- Course
- Institution
RETA INDUSTRIAL REFRIGERATION BOOK 2
[Show more]
Content preview
RETA INDUSTRIAL REFRIGERATION BOOK 2Which of the following factors listed below does not affect heat transfer?
(pg. 1-2)
A) Temperature Difference
B) Surface Area
C) Thermal Conductivity
D) Density - Answers-D) Density
An example of a poor conductor of heat is? (pg. 1-3)
A) Aluminum Tubing
B) Schedule 40 Steel Pipe
C) Wood
D) Water - Answers-C) Wood
Thermal conductivity ('K') is? (pg. 1-3)
A) Exactly the same for any metal
B) The number of BTU's that will pass in 1 hour through a material 1" thick with an area
of 1 sq. ft. if the temperature difference from one side to the other is 1°F
C) A measure of the total energy (heat content) per pound of refrigerant measured in
BTU's
D) A relationship between heat and temperature that is useful in determining discharge
temperatures. It is heat moved into or out of the process, divided by the absolute
temperature in BTU's/pound/R - Answers-B) The number of BTU's that will pass in 1
hour through a material 1" thick with an area of 1 sq. ft. if the temperature difference
from one side to the other is 1°F
Which is NOT a common source of fouling of a heat exchange surface?
(pg. 1-7)
A) Water
B) Oil
C) Frost
D) Dirt - Answers-A) Water
Which statement is true? (pg. 1-3)
A) The higher the 'k' factor, the greater the thermal conductivity
B) The lower the 'k' factor, the greater the thermal conductivity
C) The higher the 'k' factor, the lower the thermal conductivity
D) The 'k' factor is not associated with thermal conductivity - Answers-A) The higher the
'k' factor, the greater the thermal conductivity
Optimum 'U' factor for the given material that the heat exchanger is made of results
when? (pg. 1-7/8)
A) There is no impeding substance such as ice, dirt, or oil on the surfaces of the heat
exchanger tubes
,B) Maximum airflow across the evaporator is achieved
C) The system is operating with the design recirculation low
D) The system is maintaining temperature - Answers-A) There is no impeding substance
such as ice, dirt, or oil on the surfaces of the heat exchanger tubes
When air flow is decreased across a heat exchange surface, cooling capacity is? (pg. 1-
10)
A) Reduced
B) Increased
C) Not changed because area is not changed
D) Not changed because evaporator temperature is not changed - Answers-A) Reduced
One advantage of using axial type fans is? (pg. 1-12)
A) Quieter operation
B) They require less motor horsepower per CFM
C) They can move air further across the space to be cooled
D) They can work against a higher static pressure - Answers-B) They require less motor
horsepower per CFM
Which of the following is NOT a result of scale build-up on a condenser coil? (pg. 1-13)
A) Reduced heat transfer
B) Increased operating cost
C) Increased 'U' value
D) Increased condensing temperatures - Answers-C) Increased 'U' value
If 'R' value is doubled, what will happen to the heat transfer rate (assuming the
temperature difference and the area do not change)? (pg. 1-13)
A) The rate of heat that is transferred will be double
B) The rate of heat that is transferred will be cut in half
C) The rate of heat that is transferred does not change
D) The conductance is doubled so that heat transfer rate is increased - Answers-B) The
rate of heat that is transferred will be cut in half
What happens to the theoretical capacity of an evaporator in a 0°F freezer if the
ammonia evaporating pressure is dropped from 8.96 PSIG to 6.11 PSIG? (pg.
A) The capacity of the evaporator is reduced by 50%
B) The capacity of the evaporator is doubled
C) The capacity of the evaporator is not changed
D) The capacity of the evaporator is increased by 50% - Answers-C) The capacity of the
evaporator is not changed
Damaged insulation on the suction line in an ammonia refrigeration system will? (pg. 1-
14)
A) Not change the efficiency of the system because suction pressure will not change
B) Cause efficiency loss and potential damage to the suction line
C) Look bad but will not cause any major problems
,D) Cause an efficiency loss but will not cause any other problems - Answers-B) Cause
efficiency loss and potential damage to the suction line
Enthalpy is? (pg. 2-2)
A) A measure of total energy (heat content) per pound of refrigerant measured in BTU's
B) The net heat absorbing capacity of the refrigerant after the point of expansion
C) The amount of cooling effect that can be obtained from a refrigeration system
D) Heat that cannot be measured through a change in temperature - Answers-A) A
measure of total energy (heat content) per pound of refrigerant measured in BTU's
The enthalpy diagram? (pg. 2-6)
A) Illustrates the changes of condition and heat content of a pound of refrigerant at
different points of the refrigeration cycle
B) Illustrates the total heat transfer capacity of the system from evaporators through
condensers in tons of refrigeration
C) Utilizes two scales, pressure and tons of refrigeration
D) Does not take into account the effect of flash gas - Answers-A) Illustrates the
changes of condition and heat content of a pound of refrigerant at different points of the
refrigeration cycle
The enthalpy diagram has three regions of refrigerant condition which are? (pg. 2-10)
A) Solid, Liquid and Gas
B) Subcooled Liquid, SAT Liquid and Vapor, and Superheated Vapor
C) Hot, Medium, and Cold
D) Flash Gas, Subcooled Liquid, Subcooled Liquid and Flash Gas - Answers-B)
Subcooled Liquid, SAT Liquid and Vapor, and Superheated Vapor
The pressure scale on an enthalpy diagram typically used in the U.S. is expressed in?
(pg. 2-8)
A) Kilopascals
B) PSIG
C) PSIA
D) Newtons - Answers-C) PSIA
In a refrigeration system (at normal refrigeration pressures), how does the heat content
of a pound of saturated vapor compare to the heat content of a pound of saturated
liquid? (pg. 2-10)
A) The heat quantity in a pound of saturated vapor is greater than the heat quantity in a
pound of saturated liquid at the same pressure
B) The heat quantity in a pound of saturated vapor is less than the heat quantity in a
pound of saturated liquid at the same pressure
C) The heat quantity in a pound of saturated vapor is equal to the heat quantity in a
pound of saturated liquid at the same pressure
D) It is not possible to measure heat content in a pound of saturated vapor - Answers-A)
The heat quantity in a pound of saturated vapor is greater than the heat quantity in a
pound of saturated liquid at the same pressure
, In a refrigeration system (at normal refrigeration pressures), how does the volume of a
pound of saturated vapor compare to the volume of a pound of saturated liquid? (pg. 2-
A) A pound of saturated vapor occupies a larger volume than a pound of saturated liquid
at the same pressure
B) A pound of saturated vapor occupies a smaller volume than a pound of saturated
liquid at the same pressure
C) A pound is a pound, they take up the same volume
D) The volume of a pound of saturated liquid depends on the pressure applied to it -
Answers-A) A pound of saturated vapor occupies a larger volume than a pound of
saturated liquid at the same pressure
Centrifugal fans have an advantage over propeller fans in that they ______________
than prop fans? (pg. 1-12)
A) Require less physical space
B) Consume more hp per CFM of air moved
C) Are quieter
D) Have fewer components to maintain - Answers-C) Are quieter
The operating engineer? (pg. 1-7)
A) Cannot change the 'k' factor of the metal but has some control of the overall 'U' factor
for the evaporator as a unit
B) Can increase 'k' factor by increasing the air velocity over the evaporator and has
some control of the overall 'U' factor for the evaporator as a unit
C) Should allow frost to collect on the evaporator increase 'k' factor
D) Can increase 'k' factor by starting another compressor - Answers-A) Cannot change
the 'k' factor of the metal but has some control of the overall 'U' factor for the evaporator
as a unit
The limiting factor of an evaporator's capacity that the operator cannot control is? (pg. 1-
7)
A) Suction Temperature
B) Suction Pressure
C) Evaporator Size
D) Refrigerant Liquid Feed Flow - Answers-C) Evaporator Size
The best way to keep an evaporator from being affected by oil build-up is to? (pg. 1-8)
A) Operate the system at the correct evaporator temperature
B) Periodically remove oil from the oil collection points
C) Set hot gas defrost cycle for a minimum of 30 minutes
D) Increase air flow across the evaporators - Answers-B) Periodically remove oil from
the oil collection points
The effectiveness of a heat transfer surface depends on several factors. One factor the
operator has control over is? (pg. 1-8)
A) Evaporator surface area
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller GEEKA. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $13.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
75632 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now