[D2L] Final Exam Flashcards
What is happing in an evaporator?
1) the coil is releasing heat
2) the coil is absorbing heat
3) the coil is releasing cold
4) the coil is absorbing cold
the coil is absorbing heat
What colour is r22?
Green
When charging air conditioning systems with R-410A, the refrigerant must be added as a vapour?
T or F
False
Where do we find the slinger blade?
Window Shaker
Specific Gravity =
A ratio of a substances density divided by water density at 4C
convert 53kpag to kpaa
154.3 kpaa
convert 7psia to “hg
15.7
Convert 126C to rankine
718 R
Convert 0F to C
-18C
A compressed gas cylinder of 10cu/ft is filled to 36psig. Trent dropped the bottle from the building and dented it, reducing the volume to 4cu/ft. as the ambient temperature has remained constant, what is the new pressure in the bottle?
112 psig
A balloon has a predictable expansion rate affected at 100psig. if the balloon is moved from an ambient area of 55F to an ambient area at 105F, and it started at 5cuft, what should the current volume of the balloon be?
5.49 cuft
A 7cu/ft cylinder of gas in a 58F room has a reading of 56psig. if the cylinder were to be heated to 186F, what would you expect the gauge to read?
73 psig
In a 65F room sits a bottle labelled r404a, on it a digital gauge that reads 135.5psig what is in the bottle.
saturated refrigerant
In a 65F room sits a bottle labelled r134a, you hook up a gauge that reads 110psi what would you assume is in the bottle?
unknown
What refrigerant code is ammonia?
R-717
If you are going to remove or attach gauges to a system, the service valve should be in which position first?
Backseated
The unit for specific heat is Btu/lb/farenheit degree
T or F
True
Specific heat is the amount of heat required to change one pound of substance by one Fahrenheit degree.
True
As water is heated the molecules move faster
True
Which method of heat transfer uses liquids and gases and involves fast vibrating molecules take up more space than slower vibrating molecules?
Convection
What kind of mechanical energy do we use to transfer from a low zone to a high zone?
1) Pumps
2) Compressors
3) Fans
4) All of the above
All of the above
When looking at a thermostat we are reading Latent heat
T or F
False
What is the state change called when a substance changes from a liquid to a vapour?
Evaporating
Positive displacement compressors (Reciprocating) have cylinders and pistons
T or F
True
Potential energy is energy based on position
T or F
True
How does a centrifugal compressor increase refrigerant pressure?
Forces the acceleration of refrigerant
Absolute zero is when molecular motion stops.
T or F
True
Which law is the sum of each individual gas equals the total pressure?
Daltons law
Lower CoP (Coefficient of Performance) values result in an effective performance
T or F
False, higher CoP is considered effective
Lower CR (Compression Ratio) values result in a greater system performance
T or F
True
What are the units for enthalpy?
btu/lb
If the dry bulb temperature is equal to the wet bulb temperature, the water vapour will begin to condense.
T or F
True
How many grains of moisture are in one pound of water?
7000 grains
What does VOC stand for?
Volatile Organic Compounds
Oxygen makes up the majority of our air.
False
Which anemometer uses a propeller to detect airflow?
rotating vane type
Where are the Terminal units often located when a hydronic system is used?
In the duct work above the zone it’s used in
What is not recommended regarding belts?
1) check belt tension every 6 months
2) If you change 1 belt on a sheave you change all of them
3) replacement of a 4L belt is ok with an A or AX belt
4) use belt dressing or lubrication on the belt to reduce slippage
use belt dressing or lubrication on the belt to reduce slippage
What is the airflow direction of an axial fan?
Parallel to the shaft
What is the minimum fresh air that must enter a building?
10-20%
What is the purpose of a Make up air unit?
to replace exhausted air
Why do you not oil sleeve bearings?
the sleeve bearing loses its lubricating lead
The filter test which is a timed test and uses white paper downstream of a filter, which dust then lands on and light is shone through the paper is which type of test?
Atmospheric dust spot test
What is velocity pressure?
A force applied by a fluid’s motion in one direction
What are the three main types of filters?
dry, wet, electric
What is a by-product of an electronic air cleaner?
Polluting version of ozone gas
What is the range of MERV rating for a good residential air filter?
5 to 9
In Alberta, which organization administers the B52-05 Mechanical Refrigeration Code?
Alberta Boilers Safety Association = ABSA
The scope of the B52-05 Mechanical Refrigeration Code provides for the minimum requirements of design, construction, installation and maintenance.
True
The B52 code applies to private residences.
T or F
False
What is the main purpose of the Code of Practice?
to protect the Earth’s ozone layer
Which organization is responsible for administering the Code of Practice and refrigerant release in Alberta?
Alberta Environment
What is the safety rating of most refrigerants in our industry?
A1
Which of the following chemicals is not covered under the Code of Practice?
1) chlorofluorocarbons
2) chlorines
3) hydrofluorocarbons
4) refrigerants used in automobiles
chlorines
How is a ball valve used?
as a movable hole or as a plug
What is a valve’s operator?
any device used to move a control valve’s stem and disk
Which valve has the greatest pressure drop?
Globe Valve
Which valve is for Water ONLY?
Gate Valve
What is the flow pattern for a diverting valve?
One inlet pipe, and two separate outlet pipes
Where is an evaporator pressure regulator located on a dual temp system?
Downstream of the Coolers evaporator
What is the refrigerant group for R-12?
Methane
Who is responsible for the phase-out schedules for ozone depleting substances?
The Montreal Protocol est. 1987
What is a negative quality for synthetic oils?
highly hygroscopic
What position should refrigerant cylinders be transported?
upright and secured
HEPA filters are 99.7% eff (0.3 microns) and ULPA filters are 99.9% (0.1 microns)
True
In a draw through fan, the blade should be how far into the shroud
2/3
What is the volume flow rate of air moving at a velocity of 400fpm in a 10” round duct
218 CFM
How much heat is removed from air crossing a cooling coil if the air volume flow rate is 210 cfm and the amount of heat removed is 10btu for every cubic ft of air
9450 btu/min
A cooling coil with a 600CFM blower drops the temperature from 85F to 55F. How much sensible heat has been removed?
19440 BTUH
How much heat would be required to turn 226 lbs of 85F water into 263F steam?
253224
pitot tube position A, B, C, D
Pv in. wc 0.025, 0.030, 0.040, 0.035
Pv mm wc 1.016, 1.270, 1.397, 1.524
What is the average velocity?
722 FPM
What is the definition of pressure?
Force applied over an Area
Keeping temperature constant. The air will have a higher Enthalpy at a lower Relative Humidity than at a Higher Relative humidity.
False
a 5 ton AC unit is equal to how many BTU/min?
1000
Second law of thermodynamics
Energy moves from an area of high heat to an area of low heat
Which fan is not good at creating pressure
Axial
Lowest efficient centrifugal fan type is
Forward curve
What is the formula BTUH = 1.08 x CFM x ΔT?
Sensible Heat Transfer
Which property does not get plotted on a Psychrometric chart?
Entropy
Fluid Pressure based on the height of a column of liquid is
Head/Static pressure
You should take your Duct traverse readings how far away from an elbow or tee?
6-10 duct diameters
A receiver can hold a max of
90% at 90F
How long do we keep records of anything refrigerant related?
5 years
Maximum Refrigerant Recovery weight is
80% at 70F
What is Bernoulli’s Theorem or Law?
An increase in velocity pressure results in a decrease in static pressure.
Refrigerant R-410A, Head pressure of 388psi What is the saturated discharge temp?
115F
Which of the following is a chlorofluorocarbon?
R-12.
What is the approximate pressure reading at the top of a 50ft condo, when the pressure on the main floor is 30 psig?
5 psig.
The most common place refrigerant 717 is used is in a rack system
T or F
False
The superheat added to the refrigerant vapour in an evaporator is 10C degrees. What is it in Fahrenheit?
18F
What is the tonnage capacity of a refrigeration system that must remove the following heat load in one day?Product load ………………………………………… 160,998 BTU/Day
Wall load ……………………………………………….. 15,620 BTU/Day
People load ……………………………………………. 18,514 BTU/Day
Lights, Fans etc. Load ………………………………. 12,238 BTU/Day
0.72 Tons
What is the velocity of the refrigerant flowing through the refrigeration system?
Mass flow rate
The Line of constant Entropy on a PE chart is
From the inlet of the compressor to the outlet of the compressor
On a pressure enthalpy chart, where do you find the Heat of rejection(HoR)?
across the entire length of the top
