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A typical cascade refrigeration has more than 24 moving parts. All compressors require lubricating
oils and additives to function.
The Stirling Ultracold Humm™ cooling system includes just three moving parts, two in the free-piston Stirilng engine (piston and displacer) and
the tube axial fan. Because the piston and displacer float on helium gas bearings, lubricants are not required and the system uses no oil.
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FPSE vs. Cascade
Stirling Ultracold ultra low temperature freezers are not only better than conventional cascade refrigerated freezers, they’re different. While both attain a certain level of relative cooling, the Stirling Ultracold freezer offers benefits cascade systems cannot deliver.
Comparison Summary:
Stirling Ultracold Free-Piston Stirling Engine vs. Cascade Refrigeration
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Comparison
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Stirling Ultracold
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Cascade System
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Comment
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Compressor
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None
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Two
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High stage and low stage required to achieve ultra low temperatures.
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Compressor Motor
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None
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Two
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Moto heat adds to HVAC load.
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Condenser Fan
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One
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Two
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Stirling fan is tube axial, similar
to high-end computer.
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Evaporator
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Thermosiphon
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Expansion Tube
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The thermosiphon is isothermal – same temperature at all points of the tube. An expansion tube is coolest at the inlet, warmest at the outlet.
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Uniformity
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Best
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Unknown
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Stirling freezer interior walls are isothermal, generating better top-to-bottom uniformity.
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