An experimental investigation into the deployment of 3-D, finned wing and shape memory alloy vortex generators in a forced air convection heat pipe fin stack

• Published in: Applied thermal engineering 2011-10, Vol.31 (14), p.2230-2240
• Main Authors: Aris, M.S., McGlen, R., Owen, I., Sutcliffe, C.J.
• Format: Article
• Language: English
• Subjects: Active delta wings; Air conditioning. Ventilation; Applied sciences; Delta wings; Devices; Devices using thermal energy; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fin stack; Forced convection; Heat exchangers (included heat transformers, condensers, cooling towers); Heat pipes; Heat transfer; Heat transfer enhancement; Heating, air conditioning and ventilation; Intermetallics; Shape memory alloys; Stacks; Theoretical studies. Data and constants. Metering; Three dimensional; Ventilation; Vortex generators
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2011.03.015

Forced air convection heat pipe cooling systems play an essential role in the thermal management of electronic and power electronic devices such as microprocessors and IGBT’s (Integrated Gate Bipolar Transistors). With increasing heat dissipation from these devices, novel methods of improving the thermal performance of fin stacks attached to the heat pipe condenser section are required. The current work investigates the use of a wing type surface protrusions in the form of 3-D delta wing tabs adhered to the fin surface, thin wings punched-out of the fin material and TiNi shape memory alloy delta wings which changed their angles of attack based on the fin surface temperature. The longitudinal vortices generated from the wing designs induce secondary mixing of the cooler free stream air entering the fin stack with the warmer fluid close to the fin surfaces. The change in angle of the attack of the active delta wings provide heat transfer enhancement while managing flow pressure losses across the fin stack. A heat transfer enhancement of 37% compared to a plain fin stack was obtained from the 3-D tabs in a staggered arrangement. The punched-out delta wings in the staggered and inline arrangements provided enhancements of 30% and 26% respectively. Enhancements from the active delta wings were lower at 16%. However, as these devices reduce the pressure drop through the fin stack by approximately 19% in the de-activate position, over the activated position, a reduction in fan operating cost may be achieved for systems operating with inlet air temperatures below the maximum inlet temperature specification for the device. CFD analysis was also carried out to provide additional detail of the local heat transfer enhancement effects. The CFD results corresponded well with previously published reports and were consistent with the experimental findings. ► Heat transfer enhancements of heat pipe fin stacks was successfully achieved using fixed and active delta wing vortex generators. ► The active vortex generators, made from Ti–Ni, protruded into the flow stream at high temperatures and resume a low profile position at a low temperature set point. ► By considering wing spacing and the distance from the leading edge of the fin stack, heat transfer enhancements of up to 37%, compared to plane fin stacks, were achieved. ► By replacing the fixed delta wings with the active vortex generators, heat transfer enhancements of up to 16% was achieved and the pressure loss associat