Viscosity measurements for various pentaerythritol esters in the range of temperatures between 273.65 K and 373.15 K

The correct formulation of lubricants is crucial for efficient and environmentally sustainable refrigeration systems. Lubricants must ensure proper compressor lubrication and miscibility with the refrigerant to guarantee stable oil return, particularly with the current transition toward low-GWP refrigerants (ASHRAE Handbook, 2018). Among available candidates, polyol esters (POEs) are attractive due to their thermal stability, compatibility with modern refrigerants, and tuneable viscosity achieved by varying polyol or acid structures. Viscosity strongly influences lubrication performance and overall system efficiency. Nevertheless, data on branched pentaerythritol esters (PEBs)—key precursors for POE blends—remain scarce, while linear pentaerythritol esters (PECs) are better documented (Lin et al., 2020). In this study, the dynamic viscosity of eleven pure pentaerythritol esters—five linear (PEC) and six branched (PEB)—was measured from 273.65 K to 373.15 K using a rotational cone-plate rheometer. The experimental uncertainty was ±5%. The new dataset provides reliable reference values for both PEC and PEB esters, supporting future modelling and formulation of POE lubricants for next-generation low-GWP refrigeration applications.