For a laser system used in medical applications in operating theatres, AMS Technologies has developed a particularly quiet yet powerful cooling solution based on two linear compressors. The compact cooler fits into a 19-inch rack insert, keeps the cooling water of the laser exactly at the operating temperature and avoids a disturbing noise level in the operation theater.

Two Linear Compressors

Munich-based company Schumacher Elektromechanik has been comissioned to provide the power supply and cooling technology for a medical laser system. Being a long-standing AMS Technologies customer and partner, Schumacher Elektromechanik turned to the AMS thermal experts for the refrigerant circuit.

In line with the specifications for cooling capacity, temperature difference below ambient and maximum temperature deviation, AMS Technologies developed a concept based on two linear compressors operating in parallel and adjustable within wide limits. A compact plate heat exchanger serves as the interface to the customer's water circuit – with the refrigerant flowing through the heat exchanger on one side and the cooling water on the other.

Compact and Quiet

This approach also made it possible to meet two further requirements of the application: The laser system had to be very compact and quiet in order to minimize the impact on the doctors' work in the operating room, so the entire refrigerant cooling solution, including the heat exchanger, had to fit into a low-height, 19-inch rack mount and generate low operating noise. Conventional chillers with rotary compressors, however, are usually quite noisy, whether the temperature is controlled by a "hot gas bypass" (hissing noise of the corresponding valve) or in "on/off" mode (periodic switch-on or switch-off processes with start or stop noise and vibrations).

80 W to 1600 W Cooling Capacity

In contrast, the particularly compact linear compressor used here operates continuously at an almost constant frequency and only varies the stroke to regulate the cooling capacity. This compressor can hardly be heard at almost any cooling capacity – the maximum operating noise, according to the manufacturer, is 38 dBA. In addition, one of the two linear compressors operated in parallel can be switched off at low cooling requirements, so that the resulting solution delivers a very finely controllable cooling capacity between 80 W and 1600 W with hardly any change in operating noise over the entire range. The laser system being a medical device, AMS Technologies has designed the cooling solution for certification to relevant standards.

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