21st Symposium: Turbomachinery Measuring
22-23 March - 2012
Conference on Thermal Energy Management
26 March - 2012
The Energy Institute training course
27-29 March - 2012
20th PIN Meeting
2 May - 2012
6th International Conference: Thermal Engineering
22-25 May - 2011
8th ECI International Conference
3-7 June - 2012
Sustainable Energy In Buildings
14-20 October - 2012
by D.A. Reay
Heat transfer, heat exchangers and process intensification have featured strongly in 2011. The UK hosted (in Manchester) the 3rd European Process Intensification Conference (EPIC), that many PIN members attended. Later in this issue you will find a summary of what Roger Benson said on the opening day of the Conference. While I have misgivings about the desire to have 'distributed manufacturing' and distribution of other processes such as domestic combined heat and power (DCHP) - more on this later -, he concluded that the time for PI is now.
The IChemE will be taking over much of the administration of PIN from the beginning of 2012, including the organisation of the first meeting - in Newcastle on 2 May, 2012 - see News Item below. This is a most welcome change, opening up PIN to a wider audience and bringing the strength of the Institution to bear in aiding dissemination and networking. Adam and I greatly welcome it.
On another theme, having been involved in more widely diverse technologies than I care to remember over my 46 year career (and counting), it strikes me that most technologies have come close to failure when they were first conceived because of flaws in the materials/fluids available at that time, rather than any lack of engineering skills. In the laboratory where I spent the first 22 years of my working life, pioneering work on lasers, MPD (magneto-plasma dynamics), superconducting machines and high temperature heat pumps, to name a few, it was materials problems that dogged progress and commercialisation. Readers will recognise parallels in aerospace and other sectors, where material developments following early aerodynamic and design breakthroughs have eventually, possibly decades later, allowed successful implementation of the concepts.
When I first graduated, I spent a year or so in the research laboratories of C.A. Parsons & Co. Ltd., (now Siemens in Newcastle upon Tyne). As well as steam turbines, the company had been extensively involved in gas turbine development - my Section Leader had worked on coal-fired gas turbines for motive power - and they earlier employed Dr. W. Hryniszak, a gas turbine heat exchanger and materials specialist.
Wikipedia, where a short section is devoted to the work of Dr. Hryniszak on attempting to improve the economy of the gas turbine for the German Army Panther tank, introduces the reader to gas turbine recuperation and regeneration, and the contribution at the time by Dr. Hryniszak. ....... "Much of the poor fuel economy of the gas turbine in the traction role was due to the hot exhaust, which essentially represented lost energy. In order to reclaim some of this energy, it is possible to use the hot exhaust to pre-heat the air from the compressor before it flows into the combustion chamber, using a heat exchanger. Although not common, these recuperators are used in a number of applications today."
"W. Hryniszak of Asea Brown Boveri in Heidelberg designed a recuperator (that sounds like a regenerator) that was added to the otherwise unmodified GT 102 design (the tank power unit) to produce the GT 103. The heat exchanger used a rotating porous ceramic cylinder fit into a cruciform duct. Air from the gas generator's exhaust entered the duct outside the cylinder at 500 Celsius and blew around the cylinder, heating it and then exhausting at about 350o C. The ceramic cylinder rotated slowly in order to avoid overheating the "hot" side. Compressed air flowing into the power turbine was piped through the middle of the cylinder, entering at about 180o C and exiting at about 300o C.
"This meant that 120o C of the 800o C final temperature of the air did not have to be provided by the fuel, representing a fairly substantial savings. Estimates suggested an improvement of about 30% in fuel consumption. It was also suggested that a second heat exchanger could be used on the gas generator engine core, saving another 30%. This reduced fuel use by half overall, making it similar to the original gasoline engine. These estimates appear unreasonable in retrospect, although General Motors did experiment with these systems throughout the 1960s and 70s".
His work at C.A. Parsons highlighted the materials concerns in developing suitable gas turbine recuperators and regenerators, and it is fair to say that as we increase turbine inlet temperatures today and strive for more effective recuperation, materials considerations (not least the economics of using advanced alloys) still feature strongly.
For those who wish to read a most interesting treatise on heat exchangers, see: W. Hryniszak. Heat Exchangers: Application to Gas Turbines. Butterworth Scientific Publications, London 1958. One used copy for £10.00 plus postage is available (Dec. 2011) on Amazon!
Returning to the theme of decentralisation, I hope to be presenting a Keynote at the Heat Powered Cycle Conference in The Netherlands in 2012. Heat powered cycles (HPCs) cover absorption and adsorption heat pumping equipment, organic Rankine cycles (and other thermally-driven cycles), vapour recompression plant, etc.
I propose to examine the opportunities for reducing the capital and installed cost of this equipment in the process industries in a number of ways, including the use of compact heat exchangers. Has miniaturisation got a role to play in the process sector, as opposed to being mainly directed at electronics thermal management etc? Going the extra mile - can process intensification of the HPC unit operations, or more extensive integration with the principal processes in the factory, help to overcome the first cost barrier. Cost is most frequently the key feature to be overcome in recovering energy using other than conventional heat exchangers.
I feel that decentralisation of many processes would be a step too far in established industrialised nations such as those in Western Europe, where utilities are established based upon central power generation and production facilities, with small users (such as homes), supplied by, in general, excellent distribution networks for gas, water and electricity. Within some countries, including the UK, there is a trend towards decentralisation of power generation - be it by renewables or DCHP. The recent generosity of the feed-in tariff has seemingly allowed renewable power generation at a local level to leapfrog the domestic CHP units such as the British Gas Ecogen unit (based upon a Stirling engine). In a few years time it will be interesting to revisit these installations and to examine their longevity!
One area where decentralisation is a disadvantage is the capture of carbon (CC). While we have fossil-fuel fired power stations serving our grid, the convenience of fitting abatement technologies to a few large plants, be they to mitigate acid rain or carbon dioxide emissions, is obvious. This is an area where process intensification and efficient heat transfer can potentially contribute energy and cost savings to the clean-up plant, and for CC the Process Intensification Group at Newcastle University is building on PhD research carried out several years ago in using high gravity systems for absorption intensification. This has led to commercial contracts for design and experimental work, under the direction of Jon Lee.
A 'Happy New Year' to all our readers from Adam Harvey and me.