Specifications

1188
Thermal Management: Heat Exchangers
Heat Exchangers Sizing and Selection
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Subject to change without notice © 2011 Pentair Technical Products
Heat Exchang ers
Heat Exchang ers Sizin g and Select ion
Heat Exchangers Sizing and Selection Overview
Before choosing a thermal management solution, you need to carefully consider the specics of your application in addition to the following
factors:
• Fan packages and blowers may introduce ambient contaminants like oil mist and dust into the enclosure
• Heat exchangers (this section) cannot cool below the ambient temperature
• Closed-loop air conditioners can cool below ambient temperature and reduce humidity without introducing contaminants
• Simple ventilation devices such as louvers or grilles and lters are appropriate if maintaining a cool, constant temperature is not a critical
factor
Once you have determined the proper form of cooling equipment you need, selecting the required cooling capacity is outlined in this
section.
When Should You Use a Heat Exchanger?
A heat exchanger is recommended when:
• ambient air contaminants must be kept out of the enclosure
• the integrity of the enclosure must be maintained
• temperature slightly above ambient inside the cabinet is acceptable
• humidity is not a factor
How to Read Heat Exchanger Catalog Numbers
XR - 29 - 18 - 1 - 6 - 012
XR = Heat Exchanger Series; XR Modied Heat Pipe Core heat exchanger
29 = Approximate height of the heat exchanger (i.e., 29 = 29-in. high)
18 = Capacity in W/°F
1 = 115 V, 2 = 230 V
6 = 50/60 Hz
012 = UL Type
Heat Exchanger Sizing
1. Determine internal heat load in Watts (W).
1 W = 3.413 BTU/Hr.
Determine the internal heat load produced by equipment as total operating Watts.
2. Determine desired temperature dierence in degrees F.
1K ΔT = 1.8 F ΔT K ΔT = °C ΔT
Determine the ΔT (°F), the temperature dierence between the maximum temperature outside the enclosure (T
o
) and the maximum desired
temperature inside the enclosure (T
i
), which can be calculated as:
T
i
- T
o
= ΔT for heat exchangers.
3. Determine exposed surface area of the enclosure in square feet.
Area (ft.
2
) 1 m
2
= 10.76 ft.
2
Calculate the exposed surface area of the enclosure in Square Feet:
Area (ft.
2
) = 2[(H x W) + (H x D) + (W x D)] ÷ 144
where “H”, “W”, and “D” are the dimensions of the enclosure.
4. Determine required heat exchanger performance rating.
Watts ÷ ΔT(°F) - [0.22 x Area (ft.
2
)] = Watts/°F
Use this formula to determine the required cooling capacity needed to maintain the desired operating temperature for your enclosure. This
selection procedure applies to uninsulated, sealed, gasketed enclosures in indoor locations.
It is recommended that the average “Air In” rating be used when sizing an application. However, it may be possible to use a lower-rated heat
exchanger by locating the most heat-sensitive components in line with the “Air Out” opening of the heat exchanger. The actual performance
rating of any heat exchanger may vary slightly because of the airow impedance of the specic electronics congurations.