By Eamonn Ryan
Mobile refrigeration systems are a complex integration of compressors, evaporators, condensers, piping and various control devices. In the latest episode of Taking the Temperature on HVACR, Jamie Kitchen hosted experts Jörg Saar and John Broughton to explore how internal components and connection types differ from stationary systems. This is part four of a seven-part series.
Kitchen started the discussion by highlighting a key difference: hoses versus copper piping. “The hoses have something called permeability,” he explained. Hoses are flexible to accommodate movement in mobile systems, but they allow more moisture ingress than rigid copper piping. Jörg elaborated, “That’s why there’s a recommendation to exchange the filter dryer more often – to make sure it’s still doing its job.” In other words, the filter drier – a crucial component for removing moisture from the refrigerant – requires more frequent maintenance in mobile applications due to the higher exposure to humidity.
Connection types are another critical design consideration. Face seal connections, commonly used in mobile systems, consist of two plates with an O-ring and a nut, allowing easy removal of components without disturbing surrounding piping. Broughton explained, “You can take [the filter dryer] out without moving the remaining pipes a single bit.” This contrasts with flare or solder connections, which are more common in stationary systems but require partial disassembly or heating, making maintenance slower and more cumbersome.
Vibration is a central reason for these design choices. Mobile systems are constantly exposed to road or sea-induced motion, which can loosen traditional connections or induce stress in rigid components. Saar noted, “The face seal is excellent because it handles vibration and allows straightforward maintenance.” Flexible hoses and vibration-resistant mounts are also integrated into mobile designs to reduce wear on piping, valves and fittings.
Kitchen pointed out a further distinction between cars and commercial mobile refrigeration: “Cars are mostly stationary – the system only runs a few hours a day. Mobile commercial systems run 24/7.” This difference emphasises that while passenger vehicles may tolerate simpler designs, trucks, buses and ships require robust components that can withstand continuous operation under challenging conditions.
The podcast also discussed internal pipe routing and the use of flexible copper or multi-layer hoses to minimise stress and prevent cracking. Broughton remarked, “On a truck, you typically have more hoses instead of fixed copper pipes – that gives you flexibility.” Hoses must balance durability with permeability concerns, requiring careful selection of materials, layers and protective coatings.
Maintenance strategies in mobile systems also differ from stationary setups. More frequent replacement of filter driers, regular inspections of flexible hoses, and attention to O-ring or face seal connections are essential to ensure reliability. Saar explained, “You can think of it like an oil change for your car – you maintain the system proactively to avoid downtime and spoilage.”
Finally, Kitchen tied the discussion back to the cold chain, emphasising that component design directly affects product quality. “If humidity creeps in or a connection leaks, the temperature drops or spikes and the goods are compromised,” he said. Broughton added, “Whether it’s flowers, frozen pizza, or pharmaceuticals, the system must maintain its environment precisely.”
For HVACR engineers, understanding these internal differences is vital for system design, installation and ongoing maintenance. Mobile systems require specialised knowledge to balance flexibility, vibration resistance, and accessibility without compromising performance. For logistics operators, these considerations translate into fewer failures, consistent product quality, and adherence to industry standards.