Heat Exchangers for Future Heavy Commercial Vehicle Powertrains with reduced CO2 emissions

From the early days of the Internal Combustion Engine, its cooling system has been developed from quite crude evaporative systems to today’s lightweight and compact radiator designs. During the development a number of other inventions have been introduced in the cooling system e.g. thermostats, engine oil coolers, charge air coolers fans and pumps. Later emission legislation, e.g. the European Euro 4 and Euro 5, have brought the use of Exhaust Gas Recycling (EGR) in order to limit NOx formation, and this is efficient if the EGR is cooled in an EGR cooler – yet another heat exchanger in the field of IC-Engines.

In the periphery, more and more other vehicle components requires cooling – e.g. the mechanical transmissions, the power steering, and even the electronic units themselves. All powertrain heat exchangers have the purpose of removing excess heat. The fundamental cooling need comes from that energy is not transformed completely to its desired form (usually work) due to the limited thermal-, mechanical-, or electric processes used.

Up to now, the process has not been any issue, since the energy source, oil that is, has been considered infinite, despite sporadic oil-crises. Other emissions, like NOx-, hydrocarbon (HC) and particulate matter (PM) have had higher priority due to health and other environmental concerns. Today we have another, this time global concern: The net CO2 released from oil- and coal combustion affects the earth atmosphere so that the global average temperature rises, and probably still there will be several unpleasant consequences revealed to that. Research programs have started in order to find other energy sources and to reduce existing oil- and coal consumption, and also to capture and store CO2. Limited access to alternative fuels is also a driving force towards efficient vehicles.

Following these research programs are new legal actions in terms of CO2 emission-regulations, initially with some sort of tax, or fee, that will open up for new innovations that reduce net CO2 release into the atmosphere. Today, CO2 regulations in cars and small vans are introduced in the EU and soon also on heavy duty commercial vehicles (CV).
The commercial vehicles (CV) have for a long time used diesel engines for best economy and they have little potential in significant short term efficiency leaps. This has increased the interest for recovering energy that is cooled off or expelled in the engine exhausts. Waste Heat Recovery (WHR), bottoming cycles similar as used in power plants, will perhaps be the solution in CV applications as well. Several types of bottoming cycles are possible, from simple steam process (Rankine cycle), to advanced Stirling engines or through thermoelectric devices with batteries and electric engines.
The proposed thesis work has the objective to study a Rankine cycle WHR system, specifically the operating conditions for heat exchanger components in such bottoming cycle, in a Euro VI long haulage truck application.

Thesis milestones
1. Literature survey on bottoming cycles. The aim is to find basic information on selection on working media, expanders, basic heat exchanger types and selection – especially for low temperature Rankine (bottoming) cycles suitable for mobile applications.

2. Build (or modify existing-) engine- and Rankine bottoming cycle models. The aim is to get thermodynamic- and engine modeling experience and to investigate ways to implement models for bottoming cycles and detailed heat exchanger models. The cycle’s simulation work will be made in GT-Power, detailed models will be made in other software’s (e.g. Fortran) and linked to GT-power.

3. Use the models to extract heat exchanger dimensioning data and CO2 savings. The aim is to set an initial design and extract steady state temperatures and pressures for some interesting load cases, but also to find transient load data useful for design and dimensioning of heat exchangers in mobile applications. The aim is also to predict overall cycle gain in terms of CO2 savings.

4. Use the dimensioning data to specify heat exchanger design and materials. The aim is to refine the initial heat exchanger design and to refine heat exchanger models to get more accurate operating conditions and hence new dimensioning data. If required, the aim is also to identify limitations in the bottoming cycle components that have the greatest limitation of overall CO2 savings.

5. Use the models to find out how sensitive the savings are to transients and parametric variations. The aim is to find out how the savings may be affected by thermal inertia and to find out how to select performance of the bottoming cycles with respect to the engine driving cycle.

6. Write a final report. The aim is to have a detailed report describing all the actions that have been performed and the knowledge gained, i.e. the report should be detailed enough for reproducing the work done for reaching the same conclusions. It should also include problems faced, recommendations for improvements and future work.

The Master’s thesis work will be carried out primarily at LTH in Lund, with interactions and visits to TitanX in Mjällby

Key Contacts:
TitanX:
Olof Erlandsson, 0456-55056, [email protected]
Arnaud Contet, 0456-55080, [email protected]
LTH:
Martin Tunér, 046-2224050, [email protected]