In order to reduce the amount of primary refrigerant, one solution could be the use of phase change material (PCM) slurries, such as gas hydrate slurries, in secondary loops. Previous studies have shown that cyclopentane (CP) acts as a thermodynamic promoter to form hydrates and to modify the equilibrium conditions toward lower pressure and higher temperature of CO2 hydrates (having one of the higher melting enthalpy: 374 kJ.kg-1). The present work is dedicated to the rheological and thermal study of simple CP hydrate and mixed CP + CO2 hydrate slurries in a temperature-pressure controlled flow loop. For various concentrations of CP in oil-in-water emulsions (3-15wt%), the results showed that the viscosity of these slurries increases with a decreasing shear rate, exhibiting mostly a shear-thinning behaviour. Based on the heating tube method, the thermal characteristics of CP and CP + CO2 hydrate slurries showed their ability to enhance heat transfer coefficients.