A multi-phase ferrofluid flow model with equation of state for thermomagnetic pumping and heat transfer

Abstract

A one-dimensional multi-phase flow model for thermomagnetically pumped ferrofluid with heat transfer is proposed. The thermodynamic model is a combination of a simplified particle model and thermodynamic equations of state for the base fluid. The magnetization model is based on statistical mechanics, taking into account non-uniform particle size distributions. An implementation of the proposed model is validated against experiments from the literature, and found to give good predictions for the thermomagnetic pumping performance. However, the results reveal a very large sensitivity to uncertainties in heat transfer coefficient predictions.

Potential of enhancing a natural convection loop with a thermomagnetically pumped ferrofluid

“…We make use of a recently presented and validated model for thermomagnetic pumping and heat transfer [1]. This model treats phase change in the base fluid and the resulting multiphase flow in a rigorous manner.…”

“…In this paper, we suggest a procedure for designing an optimal solenoid and optimal ferrofluid for a particular application, and we derive a simple approximation for the expected thermomagnetic pumping action. Then we apply the suggested optimization procedures to set up a case study using the full model from [1]. We consider a 1 m long natural convection cooling circuit and show how thermomagnetic pumping can be used to improve its performance.…”

“…In [1], it was found that the predicted effect of thermomagnetic pumping was sensitive to heat transfer coefficients, which have high uncertainties. In the present paper, we eliminate much of this uncertainty by comparing thermomagnetic performance with natural convection, an effect which is also driven by heat transfer.…”

“…In Sec. 2, we briefly present the flow model equations that were introduced in [1]. We describe how these equations are solved numerically with periodic boundary conditions for a convection loop.…”

“…First, a simplified analytical estimate for the thermomagnetic pumping action is derived, and then design rules for optimal solenoid and ferrofluid are presented. The design rules are used to set up a medium-scale (1 m, 10-1000 W) case study, which is modeled using a previously published and validated model (Aursand et al [1]). The results show that the thermomagnetic driving force is significant compared to the natural convection driving force, and may in some cases greatly surpass it.…”