Commander S100 User Guide
17
3.3.1 Enclosure sizing
Correctly sizing an enclosure for the drive is an important aspect of the installation process and if over-looked can cause the enclosure temperature to
rise excessively making the drive less efficient. The calculations for sizing an enclosure are based on the total heat dissipation of the equipment inside
the enclosure which can be calculated as follows:
1. Add the dissipation figures from section 10.2
for each drive that is to be installed in the enclosure.
2. Calculate the total heat dissipation (in Watts) of any other equipment (such as EMC filters) to be installed in the enclosure.
3. Add the heat dissipation figures obtained above. This gives a figure in Watts for the total heat that will be dissipated inside the enclosure.
Follow the equations below to calculate the minimum required unobstructed surface area and the minimum air-flow required. Select the enclosure
(cabinet) and enclosure fan based on the values produced.
3.3.1.1 Calculating the size of a sealed enclosure
The enclosure transfers internally generated heat into the surrounding air by natural convection (or external forced air flow); the greater the surface
area of the enclosure walls, the better is the dissipation capability. Only the surfaces of the enclosure that are unobstructed (not in contact with a wall
or floor) can dissipate heat.
Calculate the minimum required unobstructed surface area
A
e
for the enclosure from:
Where:
A
e
= Unobstructed surface area in m
2
(1 m
2
= 10.9 ft
2
)
P
= Power in Watts dissipated by
all
heat sources in the enclosure
k
= Heat transmission coefficient of the enclosure material in W/m
2
/°C
Typical values of heat transmission:
•
Polypropylene PP:
0.1 - 0.22
•
Stainless steel:
16 - 24
•
Aluminium:
205 - 250
T
int
= Maximum permissible temperature in °C inside the enclosure
T
ext
= Maximum expected temperature in °C outside the enclosure
3.3.1.2 Calculating the air-flow in a ventilated enclosure
The dimensions of the enclosure are required only for accommodating the equipment. The equipment is cooled by the forced air flow.
Calculate the minimum required volume of ventilating air from:
Where:
V
= Air-flow in m
3
per hour (1 m
3
/hr = 0.59 ft
3
/min)
P
= Power in Watts dissipated by
all
heat sources in the enclosure
T
int
= Maximum permissible temperature in °C inside the enclosure
T
ext
= Maximum expected temperature in °C outside the enclosure
k
= Ratio of
Where:
•
P0
is the air pressure at sea level
•
PI
is the air pressure at the installation
Typically, a factor of 1.2 to 1.3 can be used. This will allow for any pressure drops in dirty air-filters.
A
e
=
P
k(T
int
- T
ext
)
V =
3kP
T
int
- T
ext
P
0
P
I
Summary of Contents for COMMANDER S100
Page 118: ...0478 0650 02...
