New technology in comfort cooling applications: Experimental study on paraffin in water emulsion

Phase Change Slurries (PCS) are viewed as an emerging technology in the field of comfort cooling. This kind of fluids have a much greater apparent specific heat capacity than conventional single-phase fluids and the heat transfer rate between the PCS and the wall of the heat exchanger may be enhanced. This study deals with the heat transfer behavior of a paraffin-in-water emulsion, especially the convection heat transfer coefficients during cooling inside a channel (typical of plate-heat exchangers) having a 1 m long rectangular section (80 × 6 mm2). The stability of the paraffin in water emulsion was examined under mechanical-thermal load during a period of time. Furthermore, an experimental analysis was performed on the rheological behavior of the emulsion during flow in a specific test rig. The tests were conducted using a pipe viscometer at different temperatures of the emulsion and at different shear rates. The results obtained in laminar flow show that the heat transfer coefficients of the emulsion are comparable to those for the single-phase fluid (water). The Phase Change Material Emulsion remains pumpable even after the crystallization of the dispersed phase. All these experimental results can be used to design Phase Change Material Emulsion-based cooling systems for thermal comfort.