Application of functionalized nanofluid in thermosyphon

A water-based functionalized nanofluid was made by surface functionalizing the ordinary silica nanoparticles. The functionalized nanofluid can keep long-term stability. and no sedimentation was observed. The functionalized nanofluid as the working fluid is applied in a thermosyphon to understand the effect of this special nanofluid on the thermal performance of the thermosyphon. The experiment was carried out under steady operating pressures. The same work was also explored for traditional nanofluid (consisting of water and the same silica nanoparticles without functionalization) for comparison. Results indicate that a porous deposition layer exists on the heated surface of the evaporator during the operating process using traditional nanofluid; however, no coating layer exists for functionalized nanofluid. Functionalized nanofluid can enhance the evaporating heat transfer coefficient, while it has generally no effect on the maximum heat flux. Traditional nanofluid deteriorates the evaporating heat transfer coefficient but enhances the maximum heat flux. The existence of the deposition layer affects mainly the thermal performance, and no meaningful nanofluid effect is found in the present study

Theoretical study of Oldroyd-b visco-elastic fluid flow through curved pipes with slip effects in polymer flow processing

The characteristics of the flow field of both viscous and viscoelastic fluids passing through a curved pipe with a Navier slip boundary condition have been investigated analytically in the present study. The Oldroyd-B constitutive equation is employed to simulate realistic transport of dilute polymeric solutions in curved channels. In order to linearize the momentum and constitutive equations, a perturbation method is used in which the ratio of radius of cross section to the radius of channel curvature is employed as the perturbation parameter. The intensity of secondary and main flows is mainly affected by the hoop stress and it is demonstrated in the present study that both the Weissenberg number (the ratio of elastic force to viscous force) and slip coefficient play major roles in determining the strengths of both flows. It is also shown that as a result of an increment in slip coefficient, the position of maximum velocity markedly migrates away from the pipe center towards the outer side of curvature. Furthermore, results corresponding to Navier slip scenarios exhibit non-uniform distributions in both the main and lateral components of velocity near the wall which can notably vary from the inner side of curvature to the outer side. The present solution is also important in polymeric flow processing systems because of experimental evidence indicating that the no-slip condition can fail for these flows, which is of relevance to chemical engineers

Sensible air cool-warm fan with thermoelectric module systems development

An experimental investigation on the application of thermoelectric modules for cooling and heating supply air of the conventional fan system is performed. The thermoelectric cooling module is comprised of six thermoelectric plates, two cold water boxes and a hot water box. While the thermoelectric heating module is comprised of three thermoelectric plate, a cold and hot water boxes. The obtained results from the heating capacity of the sensible air cool-warm fan system are presented and compared with those from the conventional fan system (without thermoelectric module). It can be found that the minimum and maximum water temperature obtained from the thermoelectric module are 12 °C and 70 °C, respectively. For on-off modes every 5 min, average cool air obtained from the fan system with thermoelectric module is 2.0 °C lower than that without thermoelectric module while average warm air temperature is 2.5 °C higher than that without thermoelectric module. The obtained results are also expected to guideline that will allow designing and developing the sensible air cool-warm fan system with thermoelectric module system to higher thermal performance. Keywords: Sensible air cool-warm fan, Thermoelectric module, Cooling and heatin

Evaluation of the heat transfer performance of helical coils of non-circular tubes

10.1631/jzus.A1000296Journal of Zhejiang University: Science A12163-7