| κ | thermal conductivity, W/m °C |
| T | temperature, °C |
| R2 | accuracy of linear correlations, - |
| κ | electrical conductivity of the nanofluid, µS/cm |
| ϕ | particle volume concentration, % |
| φ | particle volume fraction, - |
| Subscripts | |
| f | refers to base fluid |
| nf | refers to nanofluid |
| np | refers to nanoparticles |
| r | refers to relative |
| Abbreviations | |
| EDL | electrical double layer |
| TEC | thermo-electrical conductivity ratio |
| PEM | proton exchange membrane |