Alternative Calorimetry Based on the Photothermoelectric (PTE) Effect: Application to Magnetic Nanofluids

Photothermoelectric (PTE) calorimetry was applied for the first time for thermal characterization of liquids. Both back and front detection configurations, together with the thermal-wave resonator cavity (TWRC) scanning procedure, have been used in order to measure the thermal diffusivity and thermal effusivity of a particular magnetic nanofluid: carrier liquid—transformer oil, surfactant—oleic acid, nanoparticles’ type—\(\hbox {Fe}_{3}\hbox {O}_{4}\).The investigations were performed as a function of the nanoparticles’ concentration. Small increases of thermal diffusivity (from \(9.06\times 10^{-8}\,\hbox {m}^{2}{\cdot } \hbox {s}^{-1}\) up to \(9.84\times 10^{-8}\,\hbox {m}^{2}{\cdot } \hbox {s}^{-1})\) and thermal effusivity (from \(450\,\hbox {W}{\cdot } \hbox {s}^{1/2}{\cdot } \hbox {m}^{-2}{\cdot } \hbox {K}^{-1}\) up to \(520\,\hbox {W}{\cdot } \hbox {s}^{1/2}{\cdot } \hbox {m}^{-2}{\cdot } \hbox {K}^{-1})\) with increasing concentration of \(\hbox {Fe}_{3}\hbox {O}_{4}\) nanoparticles (from 0 up to 0.623 mg \(\hbox {Fe}_{3}\hbox {O}_{4}/\hbox {ml}\) fluid) were observed. The comparison with the photopyroelectric (PPE) method shows that PTE and PPE give similar results but, for the moment, PPE is more accurate.