HVAC Test
how many watts of electrical power are equal to 1 horsepower
746
BTU
British thermal unit
Latent heat
Change of state of a substance
Vapor is more dense than liquid and, as if liquid refrigerant boils comma it has a tendency to sink
False
Ice melts in an icebox because
Heat flows through the insulated walls he enters when the door is open he enters when warm food is placed in the icebox all of the above
Superheat
Is the point above boiling point of a substance
The evaporator in the refrigeration system
Obsorbs heat from the product to be cold
What happens when room temperature soda is poured into a glass of ice
The ice melts because it is absorbing heat from the soda
A molecule is the smallest portion that an element or substance can be divided into
True
The difference in the level of heat between two substances will determine the heat transfer rate between the substance
True
The discharge gas from the compressor is high pressure, high temperature, superheated vapor
True
The evaporator can be thought of as a heat sponge
True
The law of conservation of energy states that energy is neither created nor destroyed
True
When water boils at 212 degrees Fahrenheit it is only absorbing latent heat
True
The law requires technicians to recover refrigerant from a refrigeration system so that they
Will not be released into the atmosphere May be used again May be reclaimed for future use all of the above
Reciprocating compressor have
a piston and cylinder
a solid material exerts a pressure or force
downward only
a vapor material exerts a pressure or force
in all directions
When refrigerant enters the compressor it is a
low pressure low temperature superheated vapor
a liquid material exerts a pressure or force
outward and downward
Condensing
when a vapor turns liquid
Fusion
when the state changes from solid to liquid
The temperature on the Fahrenheit scale where all molecular biology stops is
- 460º F
The temperature on the Celsius scale where all molecular activity stops is
-273º C
How many BTU's are required to change five pounds of ice at 20º F to steam at 220º F
1,304 BTU/h
At Standard conditions on the Celsius scale, water will boil at
100º C
Pure water boils at a temperature of 212º Fat which of the following standard conditions?
14.967
A ton of refrigerant is equal to
288000 BTU/ 24 hours
The standard atmospheric pressure at sea level is
29.92
one watt of electrical energy is equal to
3.413 BTU
How many BTU's must be removed from one pound of water at 200º F for it to end up as ice at 30º F?
313 BTU
a helicopter is lifted an 800-pound unit at a rate of 200 feet per minute. how many horsepower of work energy is the helicopter using in the process?
4.848hp
Great amount of heat energy is in the change of state
970 BTUs
Separation
A mixture of vapor liquid at room temperature
High temperature Refrigeration is that produced by
An air - conditioning system
Good ventilation is important when working around Refrigeration equipment because modern refrigerants
Are heavier than air and may displace oxygen around you
The volume of gas varies inversely with the absolute pressure, provided the temp remains constant . this is called
Boyles Law
What are the three commonly used letter in devices
Capillary tube Karma automatic expansion valve, thermostatic expansion valve
At a constant pressure the volume of gas varies as to the absolute temp and at constant volume the pressure of the gas varies directly with the absolute temp. this is known as
Charles Law
The pressure in a refrigeration system is changed in the
Compressor and expansion valve
the refrigerant in a refrigeration system changes state
Condenser and evaporator
The human body gives off heat by
Convection, Radiation and Conduction
The total pressure of a confined ,mixture of gases is the sum of the pressures of each of the gases in the mixture. this is known as
Daltons Law
At what location or locations in a refrigeration system does the saturation pressure correspond to the saturation temperature
Evaporator and condenser
For the refrigeration system to operate correctly, because there's almost always be at a lower saturation temperature than the evaporator
False
Regardless of water is in a solid, liquid, or vapor State, the heat per pound to change the temperature of the water is the same
False
Water boils at 212 degrees Celsius
False
Where refrigerant leave the compressor it is a
High-pressure high-temperature superheated vapor
What is BTU
Is the amount of heat energy that is required to raise the temperature of 1 pound of water to 1 degree Fahrenheit
Subcooled
Is the point below condensing temperature of a substance 10°F- 15°F in the liquid line
What is the purpose of the metering device
It reduces the boiling point of the refrigerant far enough below the temperature of the load to get the required heat transfer rate
Condenser
It rejects sensible and latent heat
Refrigerant
Liquid that can be made to evaporate at low temperature and pressure and condenses at high temperature and pressure
PSIG indicates
Pound per square inch gauge
What is Refrigeration
Refrigeration is the process of removing heat from a place where it's not wanted and transferring that he took place where it makes little or no difference
The condenser
Reject the heat from the refrigerant
The amount of heat needed to change the temperature of a substance will vary with the type of substance. this heat quality is called
Specific heat
Major components of the refrigeration system are
Suction Line, compressor, condenser, metering device.
Specific heat
The number of BTUs required to raise the temperature of 1 pound of a substance to one degree Fahrenheit
What is the purpose of subcooling the liquid refrigerant before it leaves the condenser
The purpose is to reduce the amount of flash gas and increase the capacity of the system it helps the evaporator operate more efficiently
The unit use to measure electrical power is
Watt
Refrigeration can be described as
a process of removing heat from a place where its not wanted to a place that makes little or no difference
Sensible heat
change in temperature of a substance
If the temperature remain constant and the volume that a gas occupies increases, the pressure will
decrease
A bourdon tube is often found in a
pressure gauge
The compressor in the refrigeration system
pumps the refrigerant throughout the system
As the temperature of a material increases, the molecules in the material
travel faster
