U.S. manufacturer Tecumseh partnered with Italian ice cream machine manufacturer Frigomat to develop what they call the “first-ever” propane (R290)-based self-soft-serve ice cream machine, which “ensures food safety while maintaining superior compressor performance.”

The machine’s performance and testing were described by Anthony Chambon, Application Engineer at Tecumseh Products Company, along with a pre-taped video presentation by Francesco Tripepi, Frigomat’ CEO, at the ATMOsphere America Summit 2023 held June 12–13 in Washington, D.C.

“Cooperation between Tecumseh and Frigomat has generated a unique product marking the beginning of a new era of soft-serve machines with zero environmental impact refrigeration,” said Tripepi, adding that the unit “complies with most of the modern restrictive regulations on the subject” in a hermetically sealed unit.

“Frigomat came to us to assist them in the development of the self-pasteurizing feature of its machine,” which allows “reuse of the ice cream mix day after day” with pasteurization carried out nightly to prevent the development of bacteria, said Chambon

Frigomat chose to go with R290 because it is a “pure gas with favorable characteristics,” said Tripepi, indicating that the new unit performed 20% more efficiently than the previously used HFO refrigerant blend R452A.

The unit – developed for the U.S. and the European market – uses Frigomat’s Kiss 1HT Model 736 (a countertop soft ice cream machine, serving 266 ice creams an hour) and Tecumseh’s R290 compressor Model CAJ 2464U, operating in LBP (low back pressure) using 148g (5.2oz) of propane to provide 1.5kW (0.43TR) of refrigeration capacity with a COP of 1.45. 

The ice cream machine has a tank to hold the mix with a dispensing cylinder underneath it. The evaporator coil is located between the tank and the cylinder. When the user pulls the handle down, a motor pumps the ice cream into the cylinder, where it freezes, and the gear worm pushes the ice cream through a nozzle for dispensing.

Self-pasteurization is like hot gas defrost, which appears simple, Chambon said, but “it is difficult because of the duration at the high temperature.” The unit takes about an hour in the heating phase to raise the mix from the serving temperature of 32°F (0°C) to the pasteurizing temperature of 156°F (69°C), where it stays for 50 minutes for food safety in the holding phase before entering the refrigeration phase to drop it back to the serving temperature, which takes about 40 minutes.

Working under severe applications

During pasteurization, the highest stress points for the compressor are at the end of the heating process, during the temperature holding time and especially at the beginning of the refrigeration process due to the high suction temperature and mass flow rates, Chambon said.

“To record the maximum compressor operating temperatures in the critical operating zones, we set up several thermocouple places – in the suction muffler at the junction with the cylinder head, inside of the discharge chamber and at the intakes of the suction muffler,” Chambon said. 

The maximum operating temperatures stayed within the compressor’s warning thresholds at the muffler intake, muffler cylinder head, cylinder head, motor windings and discharge port. The lubricating oil maximum temperature of 214°F (101.1°C) was at the limit of its warning threshold of 212°F (100°C), Chambon said, “but it is not critical.” 

The first minute of compressor operation in the refrigeration phase is the most critical operating zone in the pasteurization process. “The compressor operated within its approved operating window,” Chambon noted, showing the condensing and evaporating temperatures graphed according to the first five seconds of the refrigeration phase operation time.

“Specific tests carried out at Tecumseh laboratories in France proved that the compressor is suitable for working under such severe applications,” Tripepi said. R290 promises to be particularly suitable for installation in a high condensation environment, with its ability to “maintain a condensation value that is easily controllable in respect to the room temperature,” he added.

“Even with difficult applications, our compressor is robust and reliable,” Chambon added.

Headquartered in Ann Arbor, Michigan, Tecumseh offers R290 compressors ranging in displacement sizes from 5 to 35cc (0.33 to 2.33hp) and an R290 Celseon condensing unit. At 2022 Chillventa, the company unveiled a 0.4kW (0.1TR) micro rotary propane compressor suited to EV (electric vehicle) mobile cooling under its Masterflux brand.

Headquartered in Guardamiglio, Italy, Frigomat has designed ice cream machines for over 50 years and offers a “complete range of artisan laboratory equipment” to the global market.

“Even with difficult applications, our compressor is robust and reliable.”

Anthony Chambon, Application Engineer at Tecumseh Products Company