Definitions and Acronyms Flashcards
Define Absolute Pressure
The complete pressure, including the pressure of the atmosphere
Gauge + 101.3kPa = absolute pressure
Define Ambient Pressure
The temperature surrounding an object as measured with a normal thermometer
Define ammonia
An all-natural, highly efficient refrigerant, comprised of nitrogen and hydrogen. NH3 = R717
Define anhydrous
Without water. Anhydrous ammonia is pure ammonia
Define atmospheric pressure
The pressure exerted by the atmosphere. At sea level the atmospheric pressure is 101.325 kPa (14.7 pounds per square inch
Define boiling point
The temperature at which a liquid will boil. This temperature changes with pressure. Higher pressure raises boiling point. Lower pressure lowers boiling point.
Define BTU
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
Define brine
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
Define brine pump
The pump used to circulate the brine through the chiller and arena floor piping system
Define chiller/evaporator
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
Define compression ratio
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
Define compressor
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.
Define condenser
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
Define conduction
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
Define conductivity
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
Define convection
The transfer of heat by free moving molecules such as would happen in a flow of warm water, air, or brine or refrigerant.
Define crankshaft seal
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.
Define dew point
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
Define direct refrigeration system
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.
Define direct expansion chiller (DX)
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.
Define dry bulb temperature
The air temperature as it would be measured by a normal thermometer
Define electronic leak detector
A hand held device used to locate refrigerant leaks
Define eliminator plates
Steel or plastic baffles installed on the top of an evaporative condenser to reduce the amount of spray-over and water loss
Define enthalpy
A measure of the energy content of a system per unit of mass
Define eutectic point
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.
Define evaporative condenser
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
Define evaporator/chiller
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
Define expansion valve
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.
Define firebox
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.
