Experimental study on the rheological behavior of tetrafluoroethane (R-134a) hydrate slurry

Information on the rheological characteristics of clathrate hydrate slurry is vital due to its diverse applications including hydrate slurry transportation as in seawater desalination by gas hydrate process, gas delivery through slurry pipelines, cold thermal energy storage, and secondary refrigeration by hydrate slurries. The current study experimentally investigated the rheological behavior of Tetrafluoroethane (Freon) hydrate slurry formed from R-134a and water serving as a medium for sea water desalination. Experiments were performed in a flow loop with a volume of 5.68L and an inner pipe diameter of 21.5mm, which was immersed in a constant temperature bath to maintain hydrate stable condition. Experiments were conducted with two phases in the loop; solid hydrate particles and liquid water. The hydrate solid volume fraction ranged from 15.8 to 31.7vol%. Pressure drops along the straight section of the pipe were monitored while temperature, solid volume fraction and flow rate were kept constant at desired values. The experimental results indicated that Freon slurry can be considered as a pseudo-plastic fluid. The shear-thinning characteristics of Freon slurry became more pronounced as the hydrate solid fraction increased. An empirical power law type equation that relates the apparent viscosity of the Freon slurry to the hydrate solid volume fraction and shear rate was developed and compared with experimental values. The experimental results well supported the values of the apparent viscosity calculated from the modeled equations.