(421a) Invited - Preventing Nanoparticle Plate-out in Heat Exchangers during Carrier Fluid Phase Change and Implications for Power Generation

For over a decade, a great deal of research has been conducted on the enhancement of heat transfer using nanofluids. Most exclusively, these results are rooted in the measured increase in thermal conductivity of the nanofluid when compared to the base fluid. Far less research points to negative drawbacks such as degradation of specific heat of the carrier fluid and viscosity increase with the addition of nanoparticles. We focus on the use of metal organic frameworks (MOFs) to enhance the energy transfer of a working fluid as it changes phase. The benefit of MOFs as a nanoparticle manifests itself within the energy equation in the form of the enthalpy of adsorption and desorption. We detail the many challenges faced over several years in working with nanofluids that use MOFs. Ultimately, using MOFs in power cycles can enhance the overall efficiency of the cycle with short payback period. As with most energy conversion cycles, working fluid phase change is a necessity, and resulted in nanoparticle plate-out on the various surfaces where phase change occurs. Our team has looked at several techniques for preventing this plate-out. One technique that shows promise in solving the plate-out problem involves forming a dispersion of the nanoparticles in a non-volatile low viscosity oil that is then added to the working fluid. Optical and IR spectroscopic techniques show that working fluid adsorption-desorption occurs unimpeded in the oil dispersion.