Transcript Cooling Loads Lecture #1

ARCH-432
Conduction Cooling Loads
First Exam
October 14th
Hot Glass
http://www.theguardian.com/artanddes
ign/2013/sep/06/walkie-talkie-architectpredicted-reflection-sun-rays
Lotus Temple or Baha'i
Temple
http://www.bahaihouseofworshi
p.in/architectural-blossoming
Attendance
What amazing
improvement did the
ancient Romans make
to Greek architecture
so their homes (called
heliocaminus, i.e.
house furnaces) were
far more energy
efficient?
A.
B.
C.
D.
Used cavity walls
Made domed roofs
Insulated the walls
Put transparent mica in
the windows
E. Honeycombed the floor
Attendance
Put transparent mica in the windows.
In some rare occasions, glass in the
South facing windows trapped the heat
inside the home. The home pictured
dates from the first century B.C. and is a
typical heliocaminus.
heliocaminus
heliocaminus
What You Need to Know
Describe the components that make up
a cooling load
Understand the fundamental differences
between heating and cooling loads
What You Need to be Able To Do
Calculate simple conduction cooling
loads
Evaluate systems to identify energy
savings
Terms
Cooling load
Total Equivalent Temperature
Differential (TETD)
Storage effect
Time Lag
Thermal mass
Cooling Load
“The amount of energy that must be
removed from a space in order to
maintain the space within the comfort
zone.”
Good News!
Same
Same
Same
Same
Same
‘R’ values
‘U’ values
conduction heat transfer
convection heat transfer
radiation heat transfer
Cooling Load Components
roof
lights
glass solar
infiltration
people
equipment
glass
conduction
exterior
wall
floor
partition
wall
Sensible and Latent Gains
cooling load components
conduction through roof, walls, windows,
and skylights
solar radiation through windows, skylights
conduction through ceiling, interior
partition walls, and floor
people
lights
equipment/appliances
infiltration
ventilation
system heat gains
sensible latent
load
load
Major Differences from
Heating Loads
Peak conditions
Heat storage effect
Consideration of both latent and
sensible gains
More unique sources of heat gain
Time of Peak Cooling Load
heat gain
east-facing
window
roof
12
6
12
6
12
mid
a.m.
noon
p.m.
mid
Storage Effect (thermal lag)
Prof. Kirk’s one-of-a-kind,
surefire process guaranteed to
result in a mind-numbing law
suit.
CenterStone Building
August 24 start date
Dec. 31 completion
date
Heat turned on the
first week of
December
Thermal Mass Dilemma
Time Lag
solar effect
time lag
B
A
12
6
12
6
12
mid
a.m.
noon
p.m.
mid
Time lag!
Conduction – Sunlit Surfaces
Total Equivalent Temperature
Difference (TETD) is used to account
for the added heat transfer due to the
sun shining on exterior walls, roofs, and
windows, and the capacity of the wall
and roof to store heat. The TETD is
substituted for T in the equation for
conduction.
Q = U  A  T
TETD
Conduction Gains
(Walls and Roofs and doors)
Q = U x A x TETD
where TETD is the Total Equivalent
Temperature Differential, which accounts for
 Temperature difference
 Mass
 Color
 Solar Gain
Step #1 – Select Wall Type
Step #2
Select Sun time
Select color of wall


D = dark
L = light
Select wall orientation
Step #3 – Read Value of TETD
Same Steps for Roofs
For Windows
Btuh = (U x A x TD) + (A x SC x SHGF)
A= Area
TD = outdoor design – indoor design
temp.
SC = shading coefficient
SHGF = solar heat gain factors
EQ Credit 8.1 - Daylighting
ASHRAE Standard
90.1


10% lighting load
credit for harvesting
10% lighting load
credit for occupancy
sensors
Heat Gain from People
A function of activity
Always contains
both sensible and
latent components
Equipment - Office
Best obtained from manufacturers
Can be reduced by using Capture Hood
Usually is sensible, but may have a
latent component
Equipment Loads (ASHRAE
Fundamentals)
Ventilation Load
Must consider both sensible and latent
loads
QS = 1.1 x CFM x (T2 – T1)
QL = .68 x CFM x (W2 – W1)
Q T = QS + Q L