Midterm Review Flashcards
Heat flows quicker between two objects when they have ________
Greater Temperature Difference
HVAC Techs work with what type of energy?
Thermodynamics
Heat flows from _________ to _________
Hot to Cold
1st Law of Thermodynamics states what?
Energy can not be created or destroyed
Thermodynamics is the science of …..
Heat and Energy Movement
Heat transfer between closely packed molecules is called?
Conduction
Metals used in the HVAC field have ________ conductivity
Thermal
Adding fins to the tubing in a Coil ________ the heat transfer rate.
Increase
Twice the surface area, _________ the heat transfer
Twice
Heat transfer through a flowing medium is called _____________
Convection
Passive systems _______ rely on mechanical means to increase heat transfer
A. Do
B. Do not
B. Do not
Forced Convection systems _____ rely on mechanical means to move a molecule to increase heat transfer
A. Do
B. Do not
A. Do
Active systems use ________ and _________ to increase heat transfer through convection
Fans and Pumps
Waveforms are how __________ heat transfer work
Radiant
A measurable change in temperature is called ____________ heat
Sensible
Objects are heated by this type of energy
Radiant
To calculate the specific rise in temperature of a material, techs use the ___________ ___________ capacity
Specific Heat
Changing the state of refrigerant, either gas to a liquid, or liquid to gas, or liquid to ice, or ice to liquid uses __________ heat
Latent
Which takes more heat, Latent or Sensible change?
Latent
To transfer heat, you need a heat source and a __________
Heat sink
The official definition of saturation is?
When liquid and vapor are present at the same time
To cause some gas is to condense to a liquid, we need to ________ heat
Reject
20 lbs of saturated refrigerant has the same, less, or greater pressure as 5 lbs of saturated refrigerant, at the same temperature
Same
The pressure of a refrigerant controls the ____________________ of that refrigerant
Saturation Temperature
If you increase the temperature of a saturated refrigerant, the pressure will
Increase
If you increase the pressure of a century the refrigerant, the temperature will ___________
Increase
Adding heat to a refrigerant gas is called _____________
Superheat
Removing heat from a liquid refrigerant is called ____________
Subcool
Pressure is expressed as ____________
Weight
Manometers measure ?
Pressure
Manifold gauges measure pressure compare to _________________
Atmospheric pressure
What does Saturation mean?
Completely Full
Mercury columns measure
Vacuum
Water columns measure
Lower Pressure
What is atmospheric pressure at sea level?
14.7 psia
High pressure gauges measure pressure ___________ atmospheric pressure
Above
Low side (compound) gauges measure pressure ____________ and ___________ atmospheric pressure
Above and Below
Absolute pressure is stated in
PSIA
Vacuum is any pressure ____________ atmospheric pressure
Below
A perfect vacuumed using absolute measurements is _________ “ HG Absolute
0
To cause some liquid to change to a gas, we need to __________ heat
Add Latent Heat
Barometric pressure is the same as ?
Atmospheric Pressure
High temperature and high relative humidity both produce?
Low atmospheric pressure
How do you convert psia to psig?
Pressure - 15 = psig
How do you convert psig to psia?
Pressure +15= psia
