The HeatSculptor project aims to develop a new surface engineering process; Surfi‐Sculpt®, for heat exchangers, in conjunction with state‐of‐the‐art thermal modelling and interface software. Combining these technologies will allow significant design changes to enable the production of heat exchangers with increased efficiency and functionality that are cost competitive for a variety of applications.
Equipment critical to our daily lives such as aerospace and life support systems, telecommunications, railway signals and data storage hardware use large numbers of components which generate heat by numerous mechanisms. A sudden fault or a gradually developing ‘over temperature’ event may have multiple secondary effects, reducing the life of an entire system and having potentially major social, environmental and economic impacts.
Many advanced systems employ sophisticated over temperature thermal shutdown circuitry; however by the time these fuse‐like systems engage, lasting damage has often occurred to expensive systems. Electronic faults causing over temperature events include, amongst others, short circuits (most common), bus contention (in data transmission buses), thermal runaway (in bipolar transistors), high stalling rates (in data transmission systems) and commonly high ambient temperatures.
A review of the state-of-the-art of electronics thermal management shows that a better grasp of the science of heat transfer must be attained as the demands on electronic equipment become more extreme. Whether cooling by means of natural convection, radiation, forced convection or evaporative cooling, the importance of appropriate and effective cooling are clearly illustrated by examples like:
- In power transformers, a small increase of <5ºC in the nominal operating temperature and a <20ºC increase in isolated hot spot temperatures can result in significant, 86%, reduction in device operating life, typically from 65,000 to 9,000 hours.
- 60% of electric motor failures are due to overheating; relatively small increases in electric motor operating temperature, caused by high duty cycle loading, rapidly cause deterioration in winding insulation and reduce life by 50% for each 10ºC of sustained operating temperature.
- Electrical resistance in a computer’s silicon chips leads to rapid heating when their essential heat exchangers are removed or fail. A thermal gradient of 12ºC/second is typical with chips reaching a critical temperature (~200ºC) and physically burning out in around 15 seconds.
- Problems with heat removal from electronics continue to increase and more than 70% of electronics failures are attributed to ‘over temperature’ events.
Design considerations are complex and regulations often confusing when attempting to achieve extreme performance from close packed electrical and electronic devices, as a result, new improved and quantified methods of managing and dissipating heat within systems are of critical importance to designers.
Conventional heat exchanger manufacturing processes are extensively developed and only small future efficiency improvements are likely to arise. The HeatSculptor project will generate an enabling technology that is expected to increase the performance of heat exchangers by >23%. Until now, designs have been constrained by production technologies e.g. machining or chemical etching. The new electron beam surface engineering process, Surfi-Sculpt®, has the capability to rapidly create complex Heat‐Sculptor surface geometries that are not possible with existing techniques.
HeatSculptor will further optimise the performance of heat exchangers by modelling fluid flow and heat transfer characteristics of these Surfi-Sculpt surfaces. Working together the surface geometries produced will not only provide an increase in surface area, but will also optimise the flow of cooling media over the surface, maximising its heat transfer potential.
The processes developed will provide a flexible manufacturing route, opening up the possibility of providing differential heating and cooling as required. For example, a higher density of features could be used to provide preferential cooling at a hot spot, supporting a move from traditional designs to high‐value added, knowledge intensive goods.
These revolutionary changes to heat exchanger design, with the expected improvements in product performance, versatility and cost over current designs, provide many opportunities for valuable economic return.