Effective heat capacity of ferrofluids – Analytical approach

• A new model for effective heat capacity (EHC) of in-field ferrofluids is developed.
• The possible impact of Brownian motion and magnetic fields on EHC is studies.
• An energy analysis as temperature is increased shows a small enhancement in EHC.
• EHC of homogeneous, iso-/aniso-tropic ferrofluids strongly depends on particle load.
• Similar trends for EHCs of both ferrofluids and nanofluids are expected.

Ferrofluids generally possess special thermophysical characteristics because of the magnetization of the particles. Treating a ferrofluid as a nanofluid with particles having magnetization properties, this study investigates the impact of both magnetic field and Brownian motion of particles on the specific heat. An analytical approach is employed to develop a model for the effective heat capacity of a ferrofluid that includes contributions from both factors. The model provides a modification to the classical thermal equilibrium model for heat capacity of a colloidal suspension. The modified heat capacity has two additional terms called Brownian and magnetic heat capacities. However, computations show that a very small enhancement in effective heat capacity is observed. The small enhancement was also found insufficient to overcome lessening of the heat capacity of the ferrofluid due to the existence of low-heat capacity solid particles.