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local 94 unit3a
lesson post text mid
| Question | Answer |
|---|---|
| the forms of ________________ used in refrigeration and HVAC systems include mechanical electrical and head | Energy |
| ______________ Energy is the energy of work. | Mechanical |
| ______________ heat is the heat applied to or removed from a substance that results in a temperature change. | sensible |
| _____________ heat is the heat applied to or removed from a substance that results in a change of state | Latent |
| _____________ pressure is any pressure above a perfect vacuum (0 Psia). | Absolute |
| ___________ is the scientific study of the behavior of heat. | Thermodynamics |
| __________ pressure is the force exerted by the weight of the atmosphere (gas molecules) on the earth's surface | Atmospheric |
| __________ is the energy of a substance resulting from the internal motion of its molecular structure. | Heat |
| ______ is the pressure measurement above atmospheric pressure that is used to express pressure derived from the operation of a closed system. | Gauge |
| All of the following are methods of heat transfer except: | Low to high |
| A __________ is the quantity of heat required to raise the temperature of 1lb of water 1° F. | British thermal unit (btu) |
| ________ is the amount of moisture, or water vapor, in air. | Humidity |
| __________ is the process of reducing air pollution by introducing enough fresh outdoor air into a building to dilute indoor pollutants. | Ventilation |
| A __________ HVAC unit is a self-contained building cool ing unit that has the components contained in one cabinet. | Packaged |
| A(n)__________is a substance that moves heat by chang ing state from a liquid to a gas when absorbing heat and from a gas to a liquid when rejecting heat. | Refrigerant |
| A(n)________ is a refrigeration component that creates refrigerant flow. | Compressor |
| The main components of a refrigeration system that perform the heat-moving process are the _________. | Evaporator and condenser |
| A(n)__________ is a type of heat exchanger that rejects heat from hot refrigerant vapor to a medium (air or water) in order to change the state of the refrigerant to 100% liquid. | Condenser |
| A(n) _________ is a type of heat exchanger that absorbs heat into cold refrigerant vapor from a medium (air or water) in order to change the state of the refrigerant to 100% vapor. | Evaporator |
| A(n) __________ is a component that causes a pressure drop of high-pressure liquid refrigerant. | Expansion device |
| All of the following are criteria refrigerants should meet except | High compression ratio |
| _________ point is the temperature at which oil vapors ignite without the oil itself burning. | Flash |
| _________ is a condition that occurs when a substance contains harmful. components that may cause health problems. | Toxicity |
| _________ is the ability of a substance to support ignition. | Flammability |
| All of the following refrigerant types are the most regulated by the EPA except: | HFO's |
| Refrigerants should have low __________. | Freezing points |
| When a system operates close to the _________ point, the compressor must perform more work. | Critical |
| When a zeotropic blend leaks from a system | It causes fractionation |
| Fractionation causes all of the following except: | Occurs with azeotropic type refrigerants |
| Refrigerant _________ must be compatible with the refrigerant. | Oil |
| A __________ is a rule that has been made mandatory by a federal, state, or local government. | Regulation |
| A _________ is a set of regulations or minimum requirements related to a particular trade or environment. | code |
| The mission of the __________ is to advance the arts and sciences of heating, ventilation, air conditioning, and refrigeration to serve humanity and promote a sustainable world. | (ASHRAE) |
| ________ is an independent organization that test equipment and products to verify conformance to national codes and standards. | underwriters Laboratories (UL) |
| A __________ is a hand tool used to straighten the edges of thin metal fins that extend from the condenser or evaporator coils. | Fin comb |
| A _________ is a hand tool applied to the end of tubing used to flare the end of the tubing. | Flaring tool |
| A(n) ________ measure heat energy by measuring energy emitted by the material and displays temperature as a numeric value. | Infrared temperature meter |
| A __________ is a device that detects heat levels from infrared energy emitted without making direct contact with the target. And displays the temperature as an image. | Thermal imager |
| A(n) _________ leak detector is a detector that is a stationary leak detector system with sensors and controllers to detect one specific type of refrigerant. | Fixed (refrigerant monitor) |
| Most temperature measuring instruments use a (n) _________ to take the temperature of the test point. | Temperature probe |
| _________ is a copper tubing joining method that uses nonferrous filler metal with a melting temperature less than 840°F. | Soldering |
| _____________ is typically done around 1100 to 1500 degrees F | Brazing |
| A typical use for tubing is _________. | Transfer of refrigerant through cycle |
| A typical material used for tubing is _________. | Copper |
| One of the distinguishing features of ACR tubing is that it is _________. | Sized by outside diameter |
| HVAC tubing may be _________ to reduce heat transfer to the cold refrigerant and improve efficiency | insulated |
| Before cutting copper tubing ______________. | Measure and mark cut lo cation on tubing |
| Before flaring copper tubing ______________. | Check length, condition of tubing ends and slip coupling nut over the end |
| Before soldering copper tubing __________. | Check length, conditions of ends and clean |
| Before brazing copper tubing ____________. | Apply flux |
| __________ and screw compressors are used in large commercial systems. | Centrifugal |
| All of the following are known as positive displacement compressors because a specific amount of vapor is displaced, or moved to change volume except: | Centrifugal |
| Refrigerant flow rate can be expressed either as weight (mass) or ___________ of refrigerant | Volume |
| ____________ compressors are most popular in AC pack aged unit applications. | Reciprocating |
| Smaller-tonnage compressors often use | Fully welded hermetic |
| Larger tonnage compressors used on packaged AC systems use__________ | Semi-hermetic |
| The type of compressor that has the motor and the compressor in separate housing is the __________. | Open drive |
| Reciprocating compressors use_____________ to direct refrigerant flow into the compressor during the suction stroke and out of the compressor during the discharge stroke. | Valves |
| ____________ compressors have a motor overheating challenge, due to design. | Hermetic |
| Since liquid cannot be compressed _____________________. | Slugging conditions must be avoided |
| A(n) __________ evaporator is an evaporator that uses a fan to circulate air across an evaporator coil. | Air-medium |
| A(n) _____________ evaporator is an evaporator that uses a pump to circulate water across an evaporator coil | Water-medium |
| A __________ evaporator is a heat exchanger in which the entire evaporator is full of liquid refrigerant. | Flooded |
| A ____________ evaporator is a heat exchanger in which refrigerant boils from a partial liquid/gas mixture to 100% gas before the refrigerant leaves the evaporator. | Dry-type |
| A ___________ evaporator produces superheated vapor before the refrigerant leaves. | Dry-type |
| The main design(s) of condensers is (are) ______________ | Air cooled & water cooled |
| A(n) ______________ is a type of heat exchanger that rejects heat from hot refrigerant vapor to a medium (air or water) in order to change the state of the refrigerant to 100% liquid. | Condenser |
| Typically, subcooled refrigerant can be between | 5 and 15 degrees F |
| Shell and Tube condenser are typically used in large chillers, and ________________ | Water flows through the tubes, and refrigerant f lows through the shell |
| A condenser is responsible for not only changing the state of the refrigerant from vapor to liquid, but also eliminating the _______________ in the refrigerant and allowing | Superheat |
| A(n) _______________ expansion valve is an expansion device that uses a bulb and spring to open and close a valve orifice to control the amount of refrigerant entering an evaporator. | Thermostatic |
| ______________ is a condition where the thermostatic expansion valve opens and closes often, causing widely varying evaporator conditions. | TXV hunting |
| The expansion device is located _____________ | In the liquid line close to the evaporator inlet |
| The purpose of the expansion device is to ______________ | Cause a sudden pressure drop in the liquid refrigerant |
| The ______________ is often misdiagnosed as the root of problems that were instead caused by another part of the system. | Expansion device |
| The ___________ is used to create a predetermined resistance to flow (pressure drop) and are used on mass-produced central air conditioning systems. | Fixed plate orifice |
| The thermostatic expansion valve is an expansion de vice that uses _______________ to control the amount of refrigerant entering the evaporator. | Pressure & temperature |
| The force(s) that influences the opening of a TXV is the ______________. | Bulb pressure |
| The force(s) that influence the closing of a TXV is the ___________________. | Spring and evaporator pressure |
| The following may be reasons to use an external equalizer line except | When the evaporator pressure is ported from in side the TXV body |
Created by:
jigger