Thermoacoustics: Increasing Fuel Efficiency and Reducing CO2 Emissions

Written by on July 24, 2015 in Technology

Thermoacoustics – A technology that can increase fuel efficiency and reduce CO2 emissions in marine vessels
By Sarah Challis, European Thermodynamics Ltd

The following article is a spotlight on thermoacoustics written by European Thermodynamics, a leading thermal management company in the UK. The intention of the article is to increase awareness and understanding of thermoacoustics amongst an engineering audience and to promote our knowledge and technology in thermoacoustics.

Thermoacoustics (TA) technology comprises the energy transfer between a compressible fluid (e.g. helium gas) and a solid body that is induced by acoustic propagation. The thermoacoustic effect is a physical interaction between heat and sound waves.

TA technology is particularly interesting for Marine applications because it can be used to increase fuel efficiency and reduce emissions by converting exhaust waste heat into acoustic energy and then into electricity.

There are two designs of device:

  1. Travelling wave – This type of device is available ‘off the shelf’. It consists of a (primary) cold heat exchanger, a regenerator mesh, a hot heat exchanger, a pulse tube, a (secondary) cold heat exchanger, a feedback loop and a passage for the acoustic output. Some of the acoustic power is required in the feedback to continue running the TA device. This is considered a natural occurrence which is unexplained. The acoustic output is usually used agitate an electro-acoustic transducer of some kind such as a linear alternator to produce the electricity.
  2. Standing wave – The standing wave is an in and out device, much more simplified that the travelling wave device shown (below).
Travelling wave device. Image credit: European Thermodynamics.

Travelling wave device. Image credit: European Thermodynamics.

Thermoacoustics background

Thermoacoustics was first recorded in the late 1800’s and was further researched throughout the 19th and 20th centuries. Most recently, in the 1970’s it was discovered that an acoustic wave could cause the compressible fluid to experience a thermodynamic cycle akin to that of a Stirling engine. This opened up opportunities for the potential of using a TA device in specific applications (e.g. new design of refrigerators).

Devices can be used in two ways:

  1. Macro-scale: transportation (e.g. waste heat harnessing from engines), defence (e.g. cooling of naval navigation systems), biological (cryogenic cooling), and energy e.g. in buildings and petro-chemical situations (e.g. heat pumps being driven by renewable origins, and liquefaction of natural gas)
  2. Micro-Scale – micro-electronics e.g. localised cooling of components, and MEMS (Micro Electro-Mechanical System) (e.g. for regulating the heat transfer and temperature rates in labs on chips’)

Thermoacoustic technology is available now!

The TITAN project, led by European Thermodynamics and partnered with the University of Leeds and TWI in the UK, developed a small scale prototype system which demonstrated the thermoacoustic technology in a vessel exhaust. This prototype can operate at temperatures from typically 100°C up to 500°C, at high pressure (from about 40mbar up to about 50bar). It uses Helium, or pressurised atmospheric air, as the (internal) working medium and has an efficiency of 5% to 10%.

The prototype has been developed for use in marine applications to increase fuel efficiency and reduce emissions by using was use waste heat for the recovery to. The TITAN technology will enable net CO2 emission reductions through the improved fuel efficiency of the marine vessels, and other vehicle types where the technology is applied.

For more information on the TITAN project and to request a demonstration, please contact European Thermodynamics.

Copyright © 2015 by Marine Science Today, a publication of Marine Science Today LLC.

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