Loop Heat Pipes (LHPs) are high-performance and high-reliable passive capillary two-phase heat transport devices that allow the transport of heat over long distances by the evaporation and condensation of a working fluid that flows around the loop. Its advantages of flexibility and robustness in design and assembly as well as antigravity capability of heat transport have made the LHP a superior thermal management device, among a variety of other options available. LHPs utilize latent heat of vaporization of a working fluid inside a loop to transport heat from a source to a sink, and to achieve this they take advantage of surface tension generated in a porous structure (a.k.a. “wick”) to create the capillary forces needed for the circulation of the fluid. Traditional LHP consists of five main components: evaporator, vapour and liquid line, condenser, and compensation chamber (CC) (a.k.a.“reservoir”). Typically, only the evaporator and CC contain a complex porous wick structure, while the rest of the loop is made of smooth wall transport lines. The current trend in LHP research concerns primarily applications operating at near room temperature. However, when it comes to potential applications of LHP operating at elevated values of reduced temperatures (i.e., between 500K-700K), a research gap is created. A literature search did not reveal many comparative data for LHP operating at elevated values of temperature reduced and is limited to some outdated papers of Anderson et al. and Faghri et al. and hence recently no working fluids and their chemical compatibility with LHP components and materials have been validated in this temperature range and no live test results are present. Moreover, the extension of the typical LHP operating temperature range is directly driven by the selection of an appropriate working fluid. Hence, compatibility between materials and working fluids is the main benchmark in the LHP design.