Nanoferrofluid addition enhances ammonia/water bubble absorption in an external magnetic field

The absorber is one of the most critical components to consider in the improvement of absorption refrigeration cycle performance. In this work, we investigated the addition of an Fe3O4 nanoferrofluid in combination with the application of an external magnetic field as a new method for enhancing absorption in an ammonia/water bubble-type absorber and performed a detailed experimental study of its effects on bubble absorption. The results showed that the combined effect of the nanoferrofluid and the external magnetic field significantly enhanced ammonia/water bubble absorption, and the enhancement of the combined factors was greater than that by either factor alone under the same conditions. To obtain the greatest enhancement, we also determined the optimal concentration of nanoferrofluid within the investigated range and found that absorption was further enhanced with increasing magnetic field intensity at a constant nanoferrofluid concentration. At an initial ammonia mass concentration of 20%, an Fe3O4 nanoferrofluid mass concentration of 0.10% and an external magnetic field intensity of 280 mT, the effective absorption ratio reached a maximum of 1.0812 ± 0.0001 under adiabatic condition. Finally, we discuss the mechanism of absorption enhancement by the nanoferrofluid and external magnetic field in this system.

► A new enhancing method is developed for application to NH3/H2O bubble-type absorption.
► We conducted experiments using ferrofluid in magnetic field for enhancing absorption.
► Absorption was further enhanced by the combination of ferrofluid and magnetic field.
► The mechanism of ferrofluid in magnetic field enhanced bubble absorption is discussed.
► Enhanced absorption may depend on heat transfer, bubble motion and flux linkage action.