Page 3 - 2016 Thermal Management Cooling Units Catalog Pages

THE TECHNOLOGY OF COOLING
Cooling with Closed Loop Cooling Units
Pfannenberg cooling units operate on the principle of the Carnot cycle. This means that the cooling unit functions as a heat pump that “pumps” the thermal energy transferred from the electronic cabinet (heat dissipated from the components) up to a higher level of temperature (the ambient temperature can reach levels as high as + 55 °C). The air inside the enclosure is cooled down by the evaporator and at the same time dehumidified.
How do I know if a cooling unit is the right product for my application?
• If the ambient temperature is greater than the target internal temperature of the enclosure, active cooling is required.
• If a NEMA Type 12 to 4x rating is required - closed loop systems can maintain the NEMA Type rating of the cabinet.
Properly sizing a cooling unit
To properly size a cooling unit you must know the required cooling capacity in Watts, mounting requirements (side, integrated or top mount) and the dimensions of the cooling unit and enclosure.
{P = P - P } {P = C x A x ∆T } CDRR
Utilizing performance curves to properly size cooling units:
Pfannenberg utilizes the DIN standard 35/35 °C when rating our cooling units. Many other companies use 50/50 °C, which provides a higher, non-usable value. Customers should use their own application temperatures to determine the proper cooling capacity of the system.
• PC [ Watt ]:
Refrigeration capacity of a cooling unit.
• PD [ Watt ]:
Dissipation loss: Thermal power generated inside a cabinet by the dissipation loss of components.
• PR [ Watt ]:
Radiant heat gain/loss: Heat transfer through the skin of the enclosure (insulation factor not included).
• C [ W/m2 °C ]:
Coefficient of heat transmission.
• A [ m2 ]:
Surface area of electronics cabinet.
• ∆T[ °C ]:
Difference in temperature between the ambient air and the air inside the electronics cabinet.
PC BTU W
23900 7000
20500 6000 17100 5000 13648 4000 10250 3000
6850 2000
3400 1000
00
Important information when utilizing cooling units:
• The refrigeration capacity should exceed the dissipation loss from the installed components by approximately 10%.
• The enclosure should be sealed to prevent the inflow of ambient air.
• Use the door contact switch to impede operation with open doors and consequent excessive accumulation of condensation.
• Use cooling units with maximum clearance between air inflow and air outflow to prevent poor circulation.
• Make sure that the air inflow and air outflow in the external circuit is not hindered, preventing proper heat exchanging at the condenser.
• When using top-mounted cooling units, make sure that components with their own fans do not expel the air directly into the cooling units cool air outflow.
• Make sure unit is level.
• Setting the temperature to the lowest setting is not the optimal solution due to the condensation issues. The value we have preset on the cooling unit is a sound compromise between cooling the inside of the enclosure and the accumulation of condensation.
For additional technical data, drawings and templates. www.pfannenbergusa.com
25 30 35 40 45 50 55°C
77 86 95 104 113 122 131°F
Ambient Temperature TA
Note: Cooling capacity may vary between voltage and configurations.
Electrical Enclosure Internal Temperature Ti
+45 °C / 113 °F +35 °C / 95 °F +25 °C / 77 °F
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COOLING UNITS