In his most recent published research, appearing in Applied thermal engineering, City, University of London, Dr Martin White explores a novel organic Rankine cycle system, based on a two-phase expansion through numerical simulations of the system.
His paper, Cycle and turbine optimization for an ORC operating with two-phase expansion, considers the use of modern fluids whose properties could help alleviate concerns about damage to turbines, while allowing the benefits of two-phase expansion to be realized.
Waste heat from a range of industries, from iron and steel to food and beverage, is currently released into the environment. Thus, the recovery of this wasted energy could have an important role in reducing the environmental footprint of the manufacturing sector and help ensure the sustainability of future manufacturing practices.
Dr White, Senior Lecturer in Thermal Energy at the School of Mathematics, Computer Science and Engineering, says:
One of the most promising groups of waste heat recovery technologies is that which is able to convert this waste heat into electricity. However, current technologies, generally based on the Organic Rankine Cycle (ORC) – which is similar to a vapor cycle but works with a different fluid rather than water – generally have relatively poor thermodynamic performance and are associated with high costs.
In a conventional ORC system, power is produced by the turbine which is designed to operate completely with fluid in the gaseous state. This is done to avoid the presence of liquid droplets in the impeller which could damage or erode the machine. However, previous research has suggested that the intake of a two-phase fluid, which is a combination of liquid and vapor, could improve the power output of these systems.
Dr White believes that if a suitable turbine design for two-stage operation can be devised, the performance of ORC systems could be improved.
The simulations he carried out indicate that for residual heat temperatures up to 250degrees centigrade, the introduction of two-phase expansion could generate up to 28% more power than conventional single-phase systems. In addition, candidate designs for the turbine are proposed and require further study in further studies.
The work was carried out by Dr White as part of his Royal Academy of Engineering funded research grant.
With his scholarship, Dr. White is studying next-generation waste heat recovery technologies based on two-phase expansion.