Refridgeration Flashcards
The low side of a vapor compression cycle contains the?
Evaporator
What is the primary unit of heat used in the United States
BTU British thermal unit
Which direction does heat flow
From warm to cold
In which component does refrigerant release or exhaust heat
The condenser
Besides temperature what other fundamental variable can be changed to alter the boiling point of a substance
Pressure
Where is the atmospheric pressure greater Miami or Leadville
Miami
Besides conduction and convention what is another method heat is transferred from one substance to another
Radiation
What causes atmospheric pressure
The pressure or mass of the atmosphere pushing down on the earths surface
Refrigeration cycles move heat from one location to another using what type of heat
Latent heat transfer
When a refrigeration system moves heat does it release more less or the same amount of heat that it absorbs
More
Which term refers to liquid refrigerant super heated or sub cooling
Sub cooling
Is the refrigeration cycle that operates in the water fountain the seam is that in a large chiller
Yes
What best identifies the nature of refrigerant going in and out of the metering device
Liquid in gas liquid mix out
In normal operation does liquid refrigerant return to the compressor in the refrigerating machine
No
How many thousand BTU per hour generate a ton of cooling capacity
12,000 BTU per hour
What best identifies the nature of the refrigerant going in and out of the condenser
Gas in liquid out
Compressors add heat to the refrigerant in two ways what are they
Heat of compression and motor heat
Gaseous refrigerant heated above its boiling point is said to be
Super heated
What is the word used to describe the state of matter of gas heated just a little above its boiling point
Superheated
True or false most of the heat transferred by the refrigerant in a vapor compression cycle is a latent heat
True
Sub cooling occurs in which of the four parts of the refrigeration cycle
Condenser
Which has more enthalpy a pound of water at 32° or a pound of ice at 32°
A pound of water
What unit is enthalpy expressed in
Btu/lb
What are the primary hazards when working around refrigerant in an enclosed area
Suffocation and displacement of oxygen
Refrigerant recovery cylinders are equipped with which safety devices
Fusible plug and pressure relief valve
What gas is used to purge refrigerant lines during brazing
Nitrogen
What direction is refrigerant piping sloped
It is slightly sloped down in the direction of refrigerant flow
What piping configuration keeps oil or liquid refrigerant from running back down the discharge line in the office cycle
S or inverted trap
What type of fitting is not acceptable for copper refrigerant lines
Compression fittings
If the temperature of a full refrigerant recovery cylinder is increased what happens to the pressure inside the cylinder
The pressure will rise
Scientists have identified CFC &HCFC refrigerants as agents of __________Depletion in the upper atmosphere
Ozone
A condensing unit contains which two of the four main refrigeration components
Condenser and compressor
How does a suction or discharge line P-trap assist with the flow of oil
It builds up a pool of oil which partially blocks the pipe reducing the effective size of the pipe and causing oil to entrain with the refrigerant
In which state does oil Best mix with refrigerant
Liquid
Are liquid line solenoid valves directional, that is does it matter which side you connect the liquid line from the condenser and which side points to the metering device
Yes
Brazing rod comes in the 0% 5% 15% in some higher percentages like 40% what metal is referred by the percentages
Silver
What brazing rod requires a special paste flux when making copper to steel joints
40%
When a flame is exposed to refrigerant gas what is produced
Acids
What two forces act on oil movement in refrigeration systems
Gravity and refrigerant velocity
What is an undesirable side effects of an undersized pipe in refrigerant piping
Too high of a velocity
What is an undesirable affect of an oversize pipe in refrigerant piping
Too low of velocity allowing refrigerant and oil to separate
What device is installed to prevent refrigerant migration to the evaporator in the off cycle
Liquid line solenoid valve
What weight of tubing is commonly used in refrigeration installations
Type L
What is cleaned out of copper tubing labeled ARC/OXY or med gas that is left in regular tubing
Manufacturing oils and waxes
What can help fit up larger copper refrigeration fittings
Paraffin wax or soap
One practice that helps larger tubing fittings fit up is
File away the lip on the outside of the pipe left over from the tubing cutters
What is the purpose of pressurizing ARC tubing with dry nitrogen for shipping and storage
To keep oxygen out preventing oxidation
Removing banks of pistons from operation to achieve a reduction in compressor capacity is a feature of which type of compressor
Reciprocating
True or false compressors with unloaders are typically set up to start fully loaded
False
If the compressor is fully unloaded and compressor operation still results in suction gas pressure below desired levels what is accessory may be installed to address the situation
Hot gas bypass
What is the order of the state of refrigerant as it passes through the condenser in normal operation
Gas to saturated vapor to sub cool the liquid
What can cause higher compressor head pressure’s
Debris in bedded in condenser coil’s or build up of dust on condenser coil’s
The amount of heat rejected in the condenser is greater than or less than the amount of heat absorbed in the evaporator
Greater than
What flower arrangement results in the most efficient heat transfer three hydronic heat exchanger or coil
Counter flow
Excessively high temperature difference between the entering and leaving water of a condenser could indicate
Restricted water flow
What type of condenser is typically found on smaller equipment
Double pipe
What type of water condenser is typically found on larger equipment
Shell and tube
What measure is taken to reduce the buildup of scale in cooling tower water loops
Chemical additive
If a chilled water source is used to remove heat from the water cooled condenser what device might be installed to keep head pressure steady
Water regulating valve
A once through water cooled condenser refers to an application which
City water passes through the condenser and then down the drain
To keep condenser water from getting too cold contemporary cooling towers typically use what for leaving water temperature control
A variable frequency drive on the fan motor to modulate fan speed
What measurement is taken to keep cooling tower sumps from freezing in the winter
Heat trace or receiving tank on the inside of the building
Water levels in the sump of a cooling tower or the evaporative condenser are typically controlled by what
A float valve
What advantages do water cooled condenser’s have over air cooled condenser’s
Lower condensing temperatures and pressure on the refrigerant side making compressor is more efficient
What are the advantages of air cooled condensers over cooling tower systems
No seasonal changes in operation are needed
The main problem with the air cooled condensers in some areas of the country like ours is
Cottonwood debris that blows through the air gets sucked into them
