Morteza Ghanbarpour

Fabrication, Characterization and Thermophysical Property Evaluation of SiC Nanofluids for Heat Transfer Applications

Nanofluids (NFs) are nanotechnology-based colloidal suspensions fabricated by suspending nanoparticles (NPs) in a base liquid. These fluids have shown potential to improve the heat transfer properties of conventional heat transfer fluids. In this study we report in detail on fabrication, characterization and thermo-physical property evaluation of SiC NFs, prepared using SiC NPs with different crystal structures, for heat transfer applications. For this purpose, a series of SiC NFs containing SiC NPs with different crystal structure (α-SiC and β-SiC) were fabricated in a water (W)/ethylene glycol (EG) mixture (50/50 wt% ratio). Physicochemical properties of NPs/NFs were characterized by using various techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fouriertransform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and Zeta potential analysis. Thermo-physical properties including thermal conductivity (TC) and viscosity for NFs containing SiC particles (α- and β- phase) weremeasured. The results show among all suspensions NFs fabricated with α-SiC particles have more favorable thermo-physical properties compared to the NFs fabricated with β-SiC.The observed difference is attributed to combination of several factors, including crystal structure (β- vs. α-), sample purity, and residual chemicals exhibited on SiCNFs. A TC enhancement of ∼20% while 14% increased viscosity were obtained for NFs containing 9 wt% of particular type of α-SiC NPs indicating promising capability of this kind of NFs for further heat transfer characteristics investigation.

A hybrid cooling system for telecommunicatioin base stations

Huge amount of energy is consumed by a typical telecommunication base station in order to keep the indoor climate temperature low enough to avoid any damage to IT/electronic equipment. By increasing the number telecommunication base stations applying more energy efficient cooling strategies are urgently needed. Free cooling either in direct approach (e.g. extracting fresh air), or indirect approach (e.g. thermosiphon or air to air heat exchanger) is a well-proven strategy to reduce the total power consumption for cooling telecommunication base stations. This article proposes a hybrid cooling system, which is an integrated vapour compression unit with a thermosiphon unit in a single frame. In such a hybrid system the indoor air circulates through a closed loop with minimal interaction with the outdoor air. This article suggests a model to control and estimate the potential of energy savings by a hybrid cooling system. Based on the results for an indoor temperature set point of 25 °C the cooling load provides by the hybrid system can be divided among three different operating modes: 0-59% (thermosiphon), 12-41% (dual mode), and 12-88% (air conditioning) depending on the location of the base stations.