Definitions and Acronyms

Question 1

Define Absolute Pressure

Answer 1

The complete pressure, including the pressure of the atmosphere

Gauge + 101.3kPa = absolute pressure

Question 2

Define Ambient Pressure

Answer 2

The temperature surrounding an object as measured with a normal thermometer

Question 3

Define ammonia

Answer 3

An all-natural, highly efficient refrigerant, comprised of nitrogen and hydrogen. NH3 = R717

Question 4

Define anhydrous

Answer 4

Without water. Anhydrous ammonia is pure ammonia

Question 5

Define atmospheric pressure

Answer 5

The pressure exerted by the atmosphere. At sea level the atmospheric pressure is 101.325 kPa (14.7 pounds per square inch

Question 6

Define boiling point

Answer 6

The temperature at which a liquid will boil. This temperature changes with pressure. Higher pressure raises boiling point. Lower pressure lowers boiling point.

Question 7

Define BTU

Answer 7

The amount of heat required to raise one pound of water by one degree F. It takes 144 BTU to freeze one pound water 32 degrees F to one pound ice 32 degrees F

Question 8

Define brine

Answer 8

The term used for the secondary coolant that is circulated through the arena or curling club floor. Calcium chloride is most common; sodium chloride,ethylene, other glycols have been used

Question 9

Define brine pump

Answer 9

The pump used to circulate the brine through the chiller and arena floor piping system

Question 10

Define chiller/evaporator

Answer 10

The point in the system where the refrigerant absorbs heat from the brine, and turns from a liquid to a gas. It is on low side of system. Low pressure liquid and gas

Question 11

Define compression ratio

Answer 11

The ratio of absolute discharge pressure divided by absolute suction pressure. Lower compression ratio is more efficient. A lower discharge pressure or higher suction pressure will improve compression ratios

Question 12

Define compressor

Answer 12

The pump used to remove the vaporized refrigerant from the chiller at a low pressure at the rate it is boiling and compress the refrigerant gas to a pressure where normal air and water temperatures will condense the gas back to a liquid.

Question 13

Define condenser

Answer 13

The point in the system where the refrigerant gives off the heat that it had absorbed in the chiller/evaporator and condenses from a gas back into a liquid. Most common is air-cooled for Freon, and evaporative condenser for ammonia. Water-cooled are sometimes used at facilities

Question 14

Define conduction

Answer 14

The transfer of heat by free moving molecules such as is when heat is transferred along a piece of metal when one end is heated

Question 15

Define conductivity

Answer 15

The ability of a material to convey or conduct heat. A material’s ability to conduct heat is expressed in coefficient of heat transfer. Metals typically have a high rate transfer and insulation has a low rate of transfer

Question 16

Define convection

Answer 16

The transfer of heat by free moving molecules such as would happen in a flow of warm water, air, or brine or refrigerant.

Question 17

Define crankshaft seal

Answer 17

A mechanical sealing device installed in the compressor crankcase which allows the crankshaft to exit the compressor and rotate freely without the loss of refrigerant or oil.

Question 18

Define dew point

Answer 18

The temperature at which moisture will condense out of a body of air. If air comes into contact with an object that has a temperature below the dew point, condensation will occur. (Eg. if dew point is 10C and glass is 8C, moisture will start to condense on the glass

Question 19

Define direct refrigeration system

Answer 19

In an ice arena application, a direct refrigeration system often refers to one in which the primary refrigerant is circulated directly in the floor rather than using a secondary coolant.

Question 20

Define direct expansion chiller (DX)

Answer 20

A chiller which circulated the primary refrigerant, Freon, in the tubes and the secondary refrigerant in the shell. The refrigerant is metered by a thermostatic expansion valve at a rate that causes all of it to evaporate while absorbing heat from the brine. The last tubes in the chiller further warm up the refrigerant by approx 6C of superheat to ensure no refrigerant enters the compressor.

Question 21

Define dry bulb temperature

Answer 21

The air temperature as it would be measured by a normal thermometer

Question 22

Define electronic leak detector

Answer 22

A hand held device used to locate refrigerant leaks

Question 23

Define eliminator plates

Answer 23

Steel or plastic baffles installed on the top of an evaporative condenser to reduce the amount of spray-over and water loss

Question 24

Define enthalpy

Answer 24

A measure of the energy content of a system per unit of mass

Question 25

Define eutectic point

Answer 25

In a brine solution, the eutectic point is the lowest achievable freeze temperature whereby the addition of more antifreeze will actually start to raise the freeze point.

Question 26

Define evaporative condenser

Answer 26

The condenser is where the heat is rejected from the refrigeration system and the refrigerant gas turns back to a liquid..an evaporative condenser employs the high heat absorption ability of evaporating water as well as forced-air convection cooling coil to increase its effectiveness

Question 27

Define evaporator/chiller

Answer 27

The point in the system where the refrigerant absorbs the heat from the brine, and turns from a liquid to a gas. It is on the low side of the system

Question 28

Define expansion valve

Answer 28

A pressure-reducing device designated to reduce the high-pressure liquid refrigerant to a low-pressure liquid as it enters the chiller. Common types of expansion devices for ammonia system are high side floats, low side floats, and hand expansion valves. Freon plants often use a thermostatic expansion valve.

Question 29

Define firebox

Answer 29

A firebox is most commonly used on ammonia systems. It is painted red and is located outside the building adjacent to the plant room. Inside the firebox is a hand valve to facilitate the blowing off of the ammonia charge in the event of an emergency. There is also an electrical switch tied into the refrigerator plant control circuit to enable the operator to shut down all the motors. Make sure that you have a policy in place governing the release of refrigerant from the fire box.

Question 30

Define fire point.

Answer 30

The temperature at which oil vapour will support a flame.

Question 31

Define flash gas

Answer 31

As a liquid refrigerant moves through the expansion valve, there is a drop of pressure. The drop in pressure causes a small amount of liquid refrigerant to evaporate which causes the refrigerant to drop in temperature.

Question 32

Define floc point

Answer 32

The temperature of which waxes will separate from oil

Question 33

Define frost heaving

Answer 33

In an ice arena, if the facility has no method to prevent the buildup of ice below the arena floor, frost and ice will begin to develop to the point that the floor will start to heave. The severity can be extreme. It is a good practice to install a heating floor below any ice surface operating more than 7 months a year

Question 34

Define a hermetic compressor

Answer 34

A commercial grade compressor that has both the compressor and the motor within the same housing. The compressors are manufactured in screw, reciprocating, and scroll style

Question 35

Define high pressure cut-out

Answer 35

A safety switch which senses the high pressures and will stop the compressor before dangerous pressure levels build up. High refrigerant pressures will develop if the condenser fan or pump fails, among other reasons

Question 36

Define high side

Answer 36

All parts of the refrigeration system subjected to discharge pressure. The high side starts at the discharge valves of the compressor and continues to the expansion device. Another common term for high side pressure is condenser pressure

Question 37

Define high side float

Answer 37

A refrigerant metering device that drains the liquid refrigerant from the condenser at the rate which it is being condensed. The high side float chamber is connected to the high pressure side of the system on the liquid return line from the condenser. As liquid refrigerant drains from the condenser and fills the float chamber it permits the liquid to drain into the condenser. The high side float is the dividing point in the system where high pressure liquid refrigerant turns into low pressure liquid refrigerant. The high side float is used on critically charged systems.

Question 38

Define joule

Answer 38

The unit of all forms of energy in the S.I. system. (System international)

Question 39

Define latent heat

Answer 39

Heat given off or absorbed while a substance changes state from a liquid to a gas or from a gas to a liquid. There is no temperature change during the process

Question 40

Define latent heat of fusion

Answer 40

The amount of heat that is added or subtracted from a substance to turn it from a solid to a liquid, and vice versa without a temperature change. Latent heat of fusion of water is 335 kj/kg to turn water at 0C to ice at 0C (144 BTU per pound to turn water at 32F to ice at 32F)

Question 41

Define latent heat of vaporization

Answer 41

The amount of heat that is added or subtracted from a substance to turn it from a liquid to a gas, and vice versa without a temperature change. The latent heat of vaporization of water is 2257 kj/kg to turn water at 100C to Vapor at 100C

Question 42

Define low pressure control

Answer 42

A safety switch designed to stop the compressors in the event of a low-pressure condition on the low side. This could be caused by a loss of refrigerant, or a loss of secondary coolant flow among other reasons.

Question 43

Define low side

Answer 43

All parts of the system subjected to suction pressure. The low side of the system starts after the expansion device and continues to the crankcase of the compressor. Other common terms for the low side pressure are the suction pressure and back pressure.

Question 44

Define low side float

Answer 44

A refrigerant metering device which has a chamber connected to the low pressure side of the system (chiller) . As the refrigerant level in the chiller drops, the low side float permits more liquid to enter the chiller. The low side float is the point in the system where the high pressure liquid refrigerant is reduced to low pressure refrigerant.

Question 45

Define non-ferrous metals

Answer 45

Any metal that does not contain iron. Aluminum, copper, brass, silver, lead, manganese, gold, mercury, tin, are a few of the 47 non-ferrous elements.

Question 46

Define MMC

Answer 46

The Motor Control Center houses all of the fuses, switches, hour meters, magnetic contactor, overloads, amd wiring in a single housing for all or most of the electrical loads in the refrigeration plant.

Question 47

Define oil failure switch

Answer 47

A safety switch designed to stop the compressor in the event of the loss of lubrication. A loss of lubrication could result from failing to add oil, plugged filter, or liquid flood back among other reasons.

Question 48

Define oil separator

Answer 48

The oil separator is installed on the discharge line of the refrigeration compressor in order to remove as much oil as possible from the discharge gas as it travels from the compressor to the condenser

Question 49

Define pour point

Answer 49

The temperature at which oil begins to flow

Question 50

Define psig

Answer 50

Pounds per square inch gauge. Pressure when read directly from a pressure gauge, and not including atmospheric pressure

Question 51

Define primary refrigerant

Answer 51

The refrigerant which absorbs heat by evaporating in an evaporator. Ammonia and Freon are examples of primary refrigerant.

Question 52

Define radiation

Answer 52

The transfer of heat via energy waves that travel freely through space. An example is the sun transferring heat energy through the vacuum of space to be absorbed by the planet.

Question 53

Define receiver

Answer 53

A pressure vessel used for storage of refrigerant in a refrigerant system.

Question 54

Define reciprocating compressor

Answer 54

A compressor that employs pistons within a sleeve for the purpose of a compressing low pressure refrigerant vapour into high pressure refrigerant vapour. The piston reciprocates up and down in the sleeve.

Question 55

Define Relative humidity

Answer 55

A ratio of the amount of moisture in a quantity of air compared to the total amount of moisture the air can hold at that temperature

Question 56

Define relief valve

Answer 56

A safety device designed to release the refrigerant to the atmosphere at a safe pressure in the event of an unusual high pressure situation such as could be caused by a fire or failure of system components.

Question 57

Define reverse acting high pressure control

Answer 57

Control switches designed to turn on the condenser pumps and fans in a response to an increase of discharge pressure.

Question 58

Define saturation temperature.

Answer 58

The temperature at which a substance can exist as either a liquid or a gas. One kj added would cause some of it to boil or one kj removed will cause some of it to liquefy. Whenever there is both liquid and vapour in the same vessel, the refrigerant is saturated. This is the boiling point at that particular pressure.

Question 59

Define secondary coolant.

Answer 59

The coolant that absorbs heat from the primary refrigerant in the chiller/evaporator. Calcium chloride is the most common secondary coolant in a typical arena or curling club

Question 60

Define Sensible heat

Answer 60

The heat associated with the temperature change of a substance. It can be measured with a thermometer

Question 61

Define sling psychrometer

Answer 61

A hand operated instrument used to determine relative humidity. It typically consists of two glass tube thermometers stuck on a swivel with a handle, where one of the thermometers has a wet cloth sock on the sensing end. When swung through the air, the thermometers show wet and dry bulb temperatures which is used to determine the humidity of the air

Question 62

Define specific heat

Answer 62

The amount of heat required to change the temperature of one kg of a substance 1C

Question 63

Define specific gravity.

Answer 63

The weight of substance compared to water. Water 1 kg/litre and is said to have a specific gravity of 1. Any substance added to water would have a specific gravity >1

Question 64

Define subcooled

Answer 64

The temperature of a liquid below its saturation temperature. Water at 90C would be 10 degrees sub-cooled. Sub-cooling a liquid refrigerant ahead of the expansion device reduces flash gas and increases system efficiency

Question 65

Define sublimation

Answer 65

A change of state from a solid to a gas without turning into a liquid.

Question 66

Define super-heated

Answer 66

The temperature of a gas above its saturation temperature. Steam at 110C would be 10 degrees superheated. Refrigerant vapour leaving a DX chiller would be 10 degrees superheated to ensure that there is no liquid entering the compressor. Compressor discharge gas is highly superheated.

Question 67

Define thermostatic expansion valve. TXV

Answer 67

A metering device commonly used on DX chillers. It creates the pressure drop between the high pressure and low pressure side of the system. The purpose of the thermostatic element is to ensure that there is at least 10 degrees superheated in the refrigerant vapour leaving the chiller. This will ensure there is no liquid in the vapour that would damage the compressor

Question 68

What is a ton of refrigerant (US/imperial)

Answer 68

The amount of heat removed from 1 short ton ( 2000 lbs; 907 kg) of water at 32F when turning it into one short ton of ice at 32F in 24 hrs. A ton of refrigerant is expressed as 200 BTU per minute 12,000 BTU per hour 288,000 BTU per day

Question 69

What is a tonne of refrigeration SI Units

Answer 69

The amount of heat removed from 1 tonne(1000 kg) of water at 0C when turning it into ice at 0C in 24 hrs. 233 kj/min 335,000 kj/day

Question 70

Define viscosity

Answer 70

The resistance to flow of a fluid. The measure of internal friction. Eg. molasses has higher viscosity than alcohol. As temperature increases, viscosity decreases

Question 71

Define wet bulb temperature

Answer 71

An indication of the amount of humidity in the air. A low wet bulb temperature is an indication of dry air.

Question 72

Define wet bulb depression.

Answer 72

The difference between the wet bulb and dry bulb temperatures