Domhnaill Hernon

A Vision for Thermally Integrated Photonics Systems

Thermal management has traditionally been relegated to the last step in the design process. However, with the exponential growth in data traffic leading to ever-greater levels of component integration and ever-higher levels of energy consumption, thermal management is rapidly becoming one of the most critical areas of research within the ICT industry. Given the vast use of optics for efficient transmission of high-speed data, this paper focuses on a new thermal solution for cooling the components within pluggable optical modules. Thermally Integrated Photonics Systems (TIPS) represents a new vision for the thermal building blocks required to enable exponential traffic growth in the global telecommunications network. In the TIPS program, existing thermal solutions cannot scale to meet the needs of exponential growth in data traffic. The main barriers to enabling further growth were identified and a research roadmap was developed around a scalable and efficient integrated thermal solution. In particular, the effects of replacing inefficient materials and large macroTECs with better thermal spreaders and μTECs are investidated. In addition, new forms of μChannel cooling into the package to more efficiently remove the heat generated by the lasers and the TECs are being studied which can lead to future photonic devices that can be deployed in a vastly more dense and integrated manner to address the requirements of future telecommunication networks.

Design of Complex Structured Monolithic Heat Sinks for Enhanced Air Cooling

The design and characterization of monolithic heat sinks, which can take the form of complex structures, is reported. The designs were conceived to augment heat transport for enhanced air cooling by exploiting clearly identified physical mechanisms, i.e., by streaming the flow through a 2-D array of polygonal ducts, by introducing flow-obstacle-induced local mixing, and by exploiting hydrodynamic instabilities to sustain flow unsteadiness. Fabrication of these unconventional designs was achieved by 3-D printing plastic patterns and converting them into monolithic copper structures by investment casting. A direct simulation approach aided by analytical solutions and experimental validation was undertaken to quantify fluid flow and heat transfer parameters. This paper concludes by quantifying the performance enhancement of the proposed heat sink geometries relative to a conventional longitudinally finned heat sink. On an equal pumping power basis, finned foam and slotted hexagonal heat sinks outperform conventional parallel plate finned heat sinks. On the other hand, the parallel plate heat sinks are better for pressure drop less than 20 Pa and slotted honeycombs are better for higher pressure drops (>;20 Pa).

Significantly extending the operational range of free cooling in radio Base Station indoor shelters

Both telecommunication equipment providers and solution providers are facing immense pressure to drastically enhance the energy efficiency of their hardware and networks in order to ensure environmental impact is as negligible as possible. Furthermore, increasing fuel and electricity costs are causing ever increasing operation expenditure. Alcatel-Lucent has a strong track record of tackling the aforementioned issues by innovating and deploying a suite of low-cost energy-efficient “green” telecommunications solutions. In this paper, we provide a description and analysis on one of these solutions, called “Smart Cool Solution for Base Stations (SCS4BS)”, which is dedicated to the optimization of the operational range of traditional “free cooling” solutions.

Experimental investigation into honeycomb heat sinks incorporating varying size slots for enhanced heat transfer

In this experimental investigation novel honeycomb heat sink designs that incorporate slots of varying length are presented. Thermal and hydrodynamic performance comparisons are made for a longitudinally-finned heat sink, a wavy wall heat sink of the same geometric dimensions, a closed channel honeycomb heat sink and a number of honeycomb heat sinks with different length (3mm, 6mm and 13mm) of vertically orientated slot. The heat sinks are manufactured using an investment casting process which provides a means of fabricating complex designs as one monolithic structure with high thermal conductivity that would not otherwise be possible using traditional techniques. It is demonstrated that enhanced heat transfer was achieved with the introduction of vertically oriented slots into the closed channel honeycomb structure. It is found that there is an optimum slot length per unit length of the heat sink and in the current experimental range the best performance was observed with 6mm length slots.

Experimental Performance of Novel Foam and Schwarz Surface Heat Sinks

In this experimental investigation two novel heat sink designs that employ different flow phenomena for enhanced heat transfer are presented. Thermal and hydrodynamic performance comparisons are made for three foam heat sinks with and without fins and two heat sinks with zero-mean curvature based on the Schwarz minimal surface design. Results for a longitudinally-finned heat sink are presented as a baseline comparison against the complex foam and Schwarz “3D” heat sink designs. The heat sinks are manufactured using an investment casting process providing a means of fabricating complex designs as one monolithic piece with high thermal conductivity that would not be possible using traditional techniques. It is demonstrated that against pumping power and velocity parameters the foam structures perform reasonably well in the higher velocity range. It is shown that the pressure drop across the foam and Schwarz structures is significant and the application of these designs in real systems will depend on the design constraints of the system, e.g. the foams may work well in a fan mounted heat sink assembly but not in a typical telecommunications application where flow bypass is important.Copyright

Hotwire Measurements Downstream of a Delta Winglet Pair at Two Angles of Attack

Hotwire measurements were obtained downstream of a delta winglet pair placed on an unheated flat surface. Time-averaged mean velocity, RMS, fast Fourier transform and instantaneous velocity statistics are examined to gain insight into the effect that a delta winglet pair has on manipulating an otherwise steady baseline flow. Typically, results presented in the literature are in time-averaged form and this implies that the majority of information that relates to enhanced heat transfer, i.e. unsteady flow phenomena, is lost. It is for this reason that the current investigation examines the flow downstream of the vortex generator (VG) with hotwire anemometry so as to achieve good temporal and spatial measurement resolution. The mean velocity and RMS profiles presented at two different Angles of Attack (AoA) provide valuable information on the extent to which the VG manipulates the flow. In the centreline the boundary layer is significantly thinned in comparison to other spanwise locations indicating the presence of the downwash region. The shape of the mean velocity and RMS profiles also indicate the extent to which the vortex structures grow in the spanwise direction with downstream distance from the VG. The peak RMS values are shown to increase with downstream distance in some spanwise planes and decrease with downstream distance for other spanwise planes thereby illustrating complex fluid flow interactions. Examining the instantaneous flow features reveals the true nature of the unsteadiness and also elucidates some of the more complex flow phenomena, such as positive spikes found in the near-wall region, that may lead to enhanced heat transfer. It is also observed from the instantaneous velocity traces that large negative spikes are observed in the freestream region close to the boundary layer edge. These structures help to explain the interaction between the near wall and freestream flow field thereby resulting in significantly enhanced mixing.Copyright