Midterm Flashcards
The condition that occurs when a person cannot sense the difference between themselves and the surrounding air.
Comfort
The condition that occurs when a person can sense the difference between themselves and the surrounding air.
Discomfort
A method of heat transfer
caused by the direct physical contact of substances.
Conduction
A method of heat transfer
in which heat is moved from one location to another through the circulation of a substance.
Convection
A method of heat transfer in which invisible heat rays move heat.
Radiation
What are the two main causes of combustion inefficiency?
incomplete combustion and an excess amount of air
How many conditions must be known in order to complete a psychrometric chart?
2 of the 7
How is a vacuum measured?
In inches of mercury
Define Absolute pressure.
Any pressure above a perfect vacuum (0 psi).
Define a Vacuum.
Any pressure that is less than atmospheric pressure.
The force exerted by the weight of the atmosphere (gas molecules) on the earth’s surface.
Atmospheric pressure.
A pressure measurement above atmospheric pressure that is used to express pressure derived from the operation of a closed system.
Gauge pressure
The ability of a material
to hold heat.
Specific heat
The measurement of a liquid’s resistance to flow (thickness).
Viscosity
The process of breaking a liquid into small droplets.
Atomization
A chemical reaction in fuel that occurs when oxygen reacts with hydrogen (H) and carbon (C) at an ignition temperature.
Combustion
How are air conditioning systems cooling often measure in?
Tons
Define a British thermal unit (Btu)
The quantity of heat required to change the temperature of 1 lb of water 1°F.
Define a ton.
The amount of heat required to melt one ton of ice (2000 lbs) over 24 hr. One ton of cooling equals 12,000 Btu/hr or 288,000 Btu/24 hr (12,000 x 24 = 288,000).
Define Humidity
The amount of moisture, or water vapor, in air.
What determines the amount of ventilation necessary for comfort?
The number of occupants and the kind of activity taking place inside the building.
The amount of work that can be performed by a force.
Energy
What are the different forms of energy? (7)
Heat (thermal), gravity, sounds, light, chemical, electrical, and mechanical energy.
What is occurring when an insufficient amount of oxygen is supplied by combustion air to combine with all the elements in a fuel?
Incomplete combustion
The temperature of air if it was cooled to 100% relative humidity?
Wet-bulb temperature
What is the energy of work?
Mechanical
The heat applied to or removed from a substance that results in a temperature change?
Sensible heat
The heat applied to or removed from a substance that results in a change of state.
Latent heat
What are the oxygen, carbon dioxide, and carbon monoxide levels of a fuel used to determine?
Combustion efficiency
Any substance that is burned to produce heat.
A fuel
Fuel, oxygen, and ignition temperature are the three requirements of what process?
Combustion
What two readings are used to adjust a burner so that it will operate as efficiently as possible?
Carbon dioxide and flue-gas temperature
People tend to have the best comfort at a what relative humidity?
45%
A graph that defines the properties of air at various conditions.
Psychrometric chart
What temperature is the temperature at which water vapor in the air begins to condense?
Dewpoint
The process of reducing air pollution by introducing enough fresh outdoor air into a building to dilute indoor pollutants.
Ventilation
Building HVAC systems typically use what for heating and cooling?
Furnace or boilers for heating and air conditioners or chillers for cooling.
What air velocity, in buildings, is considered ideal for comfort?
40 fpms
A self-contained building cooling unit that has the components contained in one cabinet.
A packaged unit
The amount of moisture in the air compared to the amount of moisture the air would hold at the same temperature when air is saturated, or full of moisture.
Relative humidity
What device removes moisture from the air by causing the moisture to condense or be trapped?
A dehumidifier
The rate at which work (in ft-lb) is produced per unit of time (in sec).
Power
A colorless and odorless gas fuel.
Natural gas
What takes place in a furnace or boiler to heat a building?
Combustion
What type of combustion occurs when enough oxygen is supplied by combustion air to combine with all elements in a fuel?
Complete combustion
What type of air is provided to a burner for the proper combustion of a fuel?
Combustion air
The point at which a flame is established.
Burner face
The temperature of air as taken with a standard thermometer.
Dry-bulb temperature
The total amount of heat contained in a substance.
Enthalpy
What is used to express enthalpy?
BTUs
The carbon dioxide and other va-
pors that exit a furnace or boiler to the atmosphere using a flue, which is a pipe or channel for conveying exhaust
gases.
Flue gas
