[ILM] 102D Flashcards
wet thermometer gives
a wet bulb temperature
if the air is perfectly dry, then that air sample is said to have
zero enthalpy
sublimation
the phase change from a solid directly to a vapour without passing through the liquid state
Dew Point(DP)
an air condition in which dry and wet bulb temperatures are the same
most people are comfortable in a relative humidity ranging between
30-60%
how many grains in 1lb of water
7000 grains
the higher the specific density of air,
the greater the horsepower rate the fan and its driving motor require to move the heavier air
Volatile Organic Compounds
emit toxic gases
VOC
wet air is lighter than dry air
T or F
True
Standard air
Temp: 68F
Press: 14.7 psia
Density: 0.075 lb/ft3
Air transfers heat in 3 ways:
- Radiation
- Conduction
- Convection
Radiation
gas only
Convection
gas or liquid
Conduction
solid
pressure is
the amount of force applied per unit area
weight of 1psi
is similar to the weight of approx. 6897 five-dollar-bills
1 psig ==
0 psia == -14.7psig
2.04”hgv
29.92”hgv
Total pressure - Static pressure ==
Velocity pressure
velocity means both
speed & direction
typical AC unit cfm
typical Heat Pump unit cfm
400 cfm/ton
450 cfm/ton
MERV stands for
the higher the MERV,
Minimum Efficiency Reporting Value
the more efficient the filter
MERV rating
1-20
MERV ratings
- basic residential furnace
- good residential, basic commercial
- good commercial
- hospital surgical areas
- 1-4
- 5-9
- 10-14
- 15-17
pitot tube is
an air pressure measuring device
anemometer
measures air velocity
velometer
an airflow meter that takes readings in feet per minute and is used for taking direct readings of air velocities
Determine the velocity for 0.04” wc
v = 4005 x root 0.04
= 4005 x 0.2
= 801 fpm
Determine air volume flow rate
cfm = fpm x (A in inches / 144 in2/ft2)
Find the amount of heat (total heat transfer)
Q = 4.5 x cfm x delta(h)
delta(h) = change in btu
Find the amount of sensible heat (sensible heat transfer)
Q = 1.08 x cfm x delta(f)
delta(f) = change in temperature
