Abstract
Viscoelastic fluids in low Reynolds number flow regime have important potential for heat transfer performance in contrast to Newtonian fluuids. To provide a high efficiency heat exchanger, the authors are aiming at controlling the heat transfer rate actively, in particular, with photo-rheological fluids (PRFs) which include photoisomer, the rheological properties of which can be tuned by light. The viscoelasticity of the fluids as a working fluid of heat transfer becomes weaker as the exposure time increases. As a result of the experiment, both relaxation time and pressure loss penalty were decreased with UV irradiation. The corresponding heat transfer rate also has a decreasing trend as the exposure time is lengthened more. These changes are supposed to be caused by weaker viscoelasticity of the aqueous solution that may significantly influence flow structure, as OMCA, one component of the solute used in the present study, undergoes a photo-isomerization.
