Dr. Tony Robinson’s Fluids and Heat Transfer research group at Trinity College Dublin conducted research covering a broad range of subjects that are fundamental to the science and technology of thermal energy conversion, transport and management. The primary mission of his group is to advance the state-of-the-art of thermal energy systems by developing a fundamental understanding of thermal energy transport phenomena and applying this knowledge to advanced and innovative heat exchange components, devices and technologies.
Tony’s interest in researching infrared heating has developed alongside his research in energy flows in domestic building environments, in particular when it comes to the relationships, between heating, comfort and energy cost. Thermal comfort is typically achieved by the brute force method of heating the air which is subsequently ventilated to the outside in order to maintain adequate indoor air quality. This is quite obviously not a sustainable approach and more elegant solutions, such as IR heating which have the potential to produce the desired comfort by directly heating the target, need to be developed. To achieve this it will not only require further R&D but also education so that people can make informed decisions about their home energy use. In the context of domestic appliances, entertainment and IT systems, aggressive R&D have developed scientific principles into technologies which are now ubiquitous. The same is not true for domestic thermal systems which have largely evolved as a trade and have thus not entertained anywhere near the same levels technological advancement.
Tony is attracted to the concept of IR heating because it is elegant, efficient and can be precisely engineered to suit a particular heating need. Even still, the design and implementation of IR heating also offers its own challenges in the context of human comfort. These relate to the design of the IR heater which include, but are not limited to, (i) the focusing and/or spreading of the radiation from source to target (ii) the visible glare from the source and the conundrum that the power density drops as the wavelength increases (ii) the transient response characteristics of the heater (iv) the absorption characteristics of the target and its location relative to the heater etc. In my view, there is a very broad field for R&D in IR heater technology in the domestic environment.
The challenge is to get the balance right, in the sense that most IR comfort/space heaters on the market are simply designed in the context of minimizing manufacturing cost. In my view they should be designed in the context of providing the maximum comfort (itself not easy to define) for the minimum expenditure on energy. Of course they will need to be designed for manufacture, but the design constraints should not be target output power and cost as this is crude and will not facilitate the uptake of IR technology since the comfort issue remains open. Some specific issues that need to be resolved include developing a deeper understanding of the human perception of heat in the context of comfort. This is an interesting challenge for IR heating considering that comfort will be related to a net exchange of thermal energy with ones surroundings. In a climate controlled environment the body will be warmer than its surroundings so that there is a net flow of energy from the body to the surroundings. The room is comfortable for an individual when this flow correctly balances the heat generated by one’s own metabolism, and this comfort zone will vary from person to person. With IR heating, the surroundings could be cooler resulting in a larger energy flow from the body but this compensated by the absorption of IR radiation, perceived as heat, and thus can strike the same balance with regard to comfort and do so intelligently and with less net energy expenditure.
To begin the design process we must first develop the capacity to characterize Infrared heaters; both experimentally and mathematically. Based on the scarce information available in the academic literature there is no scientific methodology or protocol for doing this. To this end our group has recently been researching different methodologies for 3D mapping of the radiant heat flux distribution from IR sources as well as characterizing their emissivity. The core concept of the 3D mapping strategy is very similar to that used to generate 3D velocity profiles in flowing liquids whereby a 3D positioning system is used to control and monitor the position of an appropriate sensor and the results are post processed to create 3D fields. In this research we are using advanced thermal imaging, IR thermometry, heat flux sensors as well are IR heat flux radiometers.
Near field thermal footprint of an IR heater impinging on a flat matt black surface (Enterprise Ireland-Innovation Voucher scheme funded)
The Research Paper
Human Comforting Heating Research