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Thermo King Tests Futuristic Cooling

Only one moving part. That’s what the sign said on what looked like a typical Thermo King trailer-mounted refrigeration unit at the food industry’s October Productivity Convention and Exposition in Phila- delphia. But only the outside shell of the refrigeration unit was typical.
Inside was a new cryogenic system the company claims can pull temperatures down to -20° three times faster than a diesel unit and could mark the beginning of a new era in refrigerated transportation.
Thermo King’s SB-III CR cryogenic system is being fleet-tested, but the company brought a unit to the food industry show seeking reaction from potential customers.
The SB-III CR relies on a pressurized tank of liquid carbon dioxide that is released slowly over the course of a day. The rapidly expanding gas quickly absorbs heat as it rushes through the coils. The moving gas also powers the fan that circulates cold air throughout the trailer. That fan, says Thermo King, is the moving part.
Spent carbon dioxide vents into the atmosphere. No gas is released inside the trailer.
The system releases virtually no pollution, only harmless carbon dioxide that would have been released into the atmosphere in any case. The system is quiet and requires little maintenance.
And then there’s the rapid cooling. With the SB-III CR, customers won’t have to precool trailers in the yard, said Smith. Indeed, one food chain executive who has been running a test unit told Heavy Duty Trucking that after loading at a sealed dock at 30°, his company’s 48-foot test trailer pulls down to 0° in 13 minutes. He said the company has been using the cryogenic-equipped trailer on daily runs for two years.
However, the SB-III CR has its limitations. The most critical is range. According to Minneapolis-based Thermo King, the on-board tank of liquid carbon dioxide will last from eight to 19 hours, depending on the inside temperature desired, the number of open-door stops and other factors.
The problem is refilling the liquid carbon dioxide tank. Though outside sources could be located and set up for scheduled runs, the system requires a custom-designed, on-site station that filters dirt and ice from the carbon dioxide. The cleanliness of the carbon dioxide is important, said Smith, since contaminants could gum up that single, critical moving part.
That means the cryogenic unit will work best on local distribution runs, particularly those in which the trailer returns empty or with nonrefrigerated items on board.
But that’s just for now. Thermo King is taking a long view, and with the advent of SB-III CR, a cryogenic future has grown a whole lot easier to imagine.