PreCoolSkin – Preliminary Study for the PhD Project “CoolSkin”
Piston rods in oil‑free reciprocating compressors are subjected to intense frictional heating at the rod-seal interface, which dramatically shortens seal life. The PreCoolSkin pre-study examined whether promising surface technologies can increase the thermal conductivity of the piston rod surface, thereby substantially improving seal cooling.
TU Dresden simulation data define the theoretical potential: even a thin coating with modest conductivity can noticeably increase heat removal, while a thicker coating with very high conductivity promises a dramatic boost in cooling performance compared with the baseline steel.
A systematic literature review, together with interviews with OEMs, compressor part manufacturers, and other industry partners, identified the most promising surface enhancement routes: thermal spraying, laser cladding, laser roll cladding, and bulk forming. These processes can deposit relatively thick layers, are largely independent of rod geometry, and provide strong metallurgical bonds, making them superior to thin‑film techniques for this application.
Figure 1: Schematic of the CoolSkin approach
Figure 2: Coating thicknesses of various surface technologies
Material‑level analysis (Fig. 3) shows that conventional high‑conductivity metals (Cu, Al, Mg) already deliver a clear improvement over the conventional piston rod steel, while metal‑matrix composites (MMCs) such as Cu‑diamond or Al‑SiC can achieve substantially higher gains. Advanced ceramics (WC, SiC, AlN, BeO) also offer good thermal performance, whereas MXenes, despite their attractive properties, are currently less favourable due to limited technological readiness and high cost.
Complementary concepts—conformal cooling channels, two-phase heat pipe inserts, and metal foam/PCM hybrids—provide additional avenues for heat rejection.
The present conclusions rely on literature and expert opinion; gaps remain in tribological behaviour, fatigue strength, gas compatibility and manufacturability at scale. The forthcoming PhD project, CoolSkin, will experimentally test selected material-process combinations, validate them through detailed simulations, and conduct the necessary mechanical and wear assessments to confirm their suitability for industrial compressor applications.
Figure 3: Thermal Conductivity of various surface materials