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HVAC Midterm Chapters 1-4 EXAM with complete solution 2024_2025
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HVAC Midterm Chapters 1-4 EXAM with complete solution 2024_2025
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HVAC Midterm Chapters 1-4 EXAM withcomplete solution 2024/2025
cooling process - ANSWER-removes heat from from air, which causes the temp
of the air to drop
ventilation - ANSWER-supplies or removes air from space (required to replenish
the oxygen supply) (dilutes odor) (provide makeup air for rooms with exhaust
systems; maintains acceptable air balance
Factors that influence human comfort - ANSWER-Temperature, humidity, Air
quality, and Air movement
heating, cooling, filtration, ventilation & humidification are collectively called -
ANSWER-Air Conditioning
2 common complaints - ANSWER-temp to hot or cold & humidity is either to high
or too low
Fixed louvres - ANSWER-redirect the airflow; causing rain/snow to fall out of air
suspension
Dampers - ANSWER-control the airflow
finned heating coils - ANSWER-some may be use steam to heat air, steam goes
through coil & heats air traveling around, steam condenses inside coil & returns
to boiler
,finned cooling coils - ANSWER-chilled water to cool air, water circulates through
coil & removes heat from air travelling around coil, warmed water leaves coil &
returns to chiller
An increased air flow increases the heat loss of the body by - ANSWER-
conduction, convection & evaporation which helps body to remain comfortable
when the room temp is higher than normal.
humidifiers - ANSWER-add water to air, pump water from water bath & inject it
into airflow using spray nozzles
Air diffusers - ANSWER-direct the flow of air into the space without creating a
draft
fans - ANSWER-create airflow/air movement
Return air - ANSWER-% of exhaust air is recirculated to increase building
efficacies & lowers the operating costs. This air must be retreated
Outside air - ANSWER-aka make-up air, regulated by building codes; used to help
maintain human health conditions
mixed air - ANSWER-mixture of return air & make-up air (needs to be treated)
supply air - ANSWER-air treated by HVAC system that's supplied to the building
Human health is the key criteria when deigning an - ANSWER-HVAC system
Effective temperature (ET) - ANSWER-(temperature, humidity & air movement)
measure of comfort that which involves the combined effects of dry-bulb temp,
relative humidity & air movement (not an actual temp even though its expressed
in C & F) (cannot be measured with a thermometer)
An airflow of 4-8 m/min is considered - ANSWER-relatively still
air draft of 19.8 m/min, most people would consider it to be a - ANSWER-draft
crowded spaces should be kept at - ANSWER-lower temperatures
rooms on the north side should be kept - ANSWER-warmer during winter
, moisture added to increase the RH minimizes the effects of - ANSWER-static
electricity
in colder climates, dehumidification may be required in humid areas to prevent: -
ANSWER-structural damage during winter due to frost formation in exterior walls
Air movement/circulation is required in each space to dissipate _______________
from occupants & prevents build up of __________ which may develop in
stagnant areas. - ANSWER-body heat, odors
Air filters must remove contaminates (impurities) such as - ANSWER-dust, dirt,
smoke, pollen & lint
temperature kept between _____________ & best for everyone is ________ -
ANSWER-18-22 degrees & 20
Humidity kept between ___________ and best for everyone is ________ -
ANSWER-30-70% and 50%
Humidity in winter is best at _______ - ANSWER-30%
Humidity in summer is best at ______ - ANSWER-70%
relationship of temp & humidity is called - ANSWER-psychometrics
radiant heat - ANSWER-rooms on sunny side kept cooler
higher temps if occupants in building for (prevents discomfort) - ANSWER-short
amount of time
Unitary systems - ANSWER-each individual room/zone has a self contained AC
unit; maintains the desired environmental conditions
Central systems - ANSWER-air handling unit in central mechanical room, ducts
distributes (filter, humidify/dehumid, heat, cool; can have thermostat in each
room, provide individual room temp
Combined systems - ANSWER-air handling unit in central room, ducts distribute
(usually only has ventilation, preheating & cooling) supplementary equip located
in each zone to provide heating + additional cooling. Complex, costly but superior
zone temperature control
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