Thermal management of mobile computing devices plays an important role in the performance and reliability of their electronic components. Centrifugal blowers are the most commonly used system-level cooling solution for these devices. In this paper, novel designs of centrifugal blowers called Plated Blowers (PB) and Disc Blowers (DB) are proposed for cooling laptop computers, where the conventional rotor blades are replaced by a new design either comprising of circular sheet metal as a rotor with punched holes and residual hanging chads or discrete blades formed along the disc beside each hole that works to displaces air. It had a similar working principle as Volumetric Resistance Blower (VRB), where the porous disc is replaced by randomly distributed small structures across a circular plate which moves the air within the blower. A numerical study was conducted on these designs to determine the flow rates under an operational angular speed of 6000 RPM. The results showed that both PB and DB designs can outperform the traditional blade fan design as well as the VRB in terms of air volume flow rate at isorpm conditions(not necessarily iso-acoustic). Like VRB which has a porous rotor, the newly discussed designs are also expected to offer a significant acoustic advantage over traditional bladed blowers, which can enable an increase in overall platform power in these mobile computing systems.

Ionic wind is an effective technique to enhance natural convection cooling, as it can generate flow with minimum moving parts and power consumption. This paper presents an experimental investigation of ionic wind for heat transfer enhancement for an aluminium heat sink under natural convection. Experiments were performed at different orientations of the aluminium heat sink to determine the relative impact of buoyancy and EHD driven heat transfer. Tests were conducted for different electrode spacing ranging between 5 mm to 15 mm subjected to 5.64 kV corona voltage and considering three different sets of emitters having varied number of electrodes. Vertical orientation of fin yielded maximum advantage in cooling from ionic wind. The enhancement was significantly affected by the number of electrodes in the emitter and electrode spacing. There exists an optimum electrode number and spacing where the enhancement was found to be maximum. For the present study, it was found to be 10 nos. and 10-mm respectively. The results showed that ionic wind can help reduce the thermal resistance by a factor of up to 2.34 compared to natural convection for vertical arrangement. In case of inclined orientation, results suggested existence of an optimal angle for maximum cooling in presence of ionic wind, where the reduction in thermal resistance was up to a factor of 1.6. The increase in corona voltage from 5.64 kV to 7.05 kV, for optimum spacing, caused the enhancement to increase from 2.34 to 3.09 for 10 number of needle electrodes.

In this paper, we present our results on a relatively new kind of blower called Volumetric Resistance Blower (VRB) for cooling of portable computing platforms like laptop computers. The VRB performance was modeled numerically and compared to traditional bladed blowers. The sources of noise, dominant in bladed blower, are absent in case of VRB, because it uses a continuous porous disk instead of discrete blades. Thus, even though at iso-rpm, VRB yielded lower flowrate, its iso-acoustic performance could be superior. Hence, further analysis was crucial to quantify the potential benefit. The acoustics experiments for bladed blower and VRB were conducted in a hemi-anechoic chamber in accordance with ECMA-74 and ECMA TR/99 standards. Iso-acoustics pressure versus volume flowrate plot for both bladed blower and VRB are compared. VRB was found to have superior performance as compared to bladed blower. The volume flowrate at open flow condition for bladed blower and VRB are comparable, but as back pressure increased the flowrate yielded by VRB kept increasing and at stagnation condition, VRB showed around 79% higher static pressure. In the second part of the work, the experimentally validated numerical model for VRB was used for numerical optimization using a design of experiments (DOE) approach and varying the geometrical parameters. Rotor distance (minimum distance from the axis of rotation of impeller to the cutwater surface) was found to be the most important parameter, and an optimum value was found. A second DOE elucidated the optimal rotor hub center location in the two-dimensional space inside the casing as when the rotor is tucked back into the casing as much as possible and when the rotor distance is above 20.15 mm. A partial P-Q curve is generated (up to 20 Pa) for optimal geometry configuration. Based on the numerical and experimental evidence, VRB is found to have the potential to replace traditional bladed design in portable computing devices. In addition, due to absence of blades, it creates lower tonal noise, giving a much more comfortable experience to the end user.

In this paper, a novel design of centrifugal blower called Plated Blowers (PB) is proposed for cooling of laptop computers where the conventional rotor blade is replaced by a new design comprising of a sheet metal rotor with punched holes and residual hanging chads. A numerical study was conducted on these designs to determine the flow rates under operational speed of 6000 rpm. The results showed that the PB designs can outperform the traditional blade fan design as well as the Volumetric Resistance Blower (VRB) [1] in terms of air flow rate at iso-rpm conditions. Similar to VRB which has a porous rotor, the PBs are also expected to offer significant acoustic advantage over bladed fans (claim to be validated through tests), which can result in a boost in overall platform power in these mobile computing systems.

Heat dissipation in electronic devices is highly essential to maintain the temperature within safe limits and overcome the component failure. Ionic wind has emerged as one of the potential cooling technologies in thermal management of electronic devices over conventional cooling methods. The ionic wind cooling has drawn considerable attention for both external and internal flows owing to the favorable characteristics such as silent operation, quick response, minimum power and compactness. In the recent years, new actuating strategies have been developed by various researchers for enhancement of heat dissipation. The motive of the present review is categorized into three. The first is to provide an insight in recent advancement of ionic wind from the point of physics and electric field; later the application of ionic wind for heat transfer enhancement in both external and internal flows such as cooling of plates, circular tubes, channel, power chips and heat exchangers is reported. In addition, the delay in flow separation accounting for change in flow characteristics is also discussed. Some of the key outcomes and new designs of ionic wind generator are highlighted, which guides for further optimal design. Finally, the ongoing challenges and possible future research areas that can have impact on technology is presented.