A new simulation capability is presented to enable the performance of a hardware-based temperature control system to be assessed in thermally-managing heat-generating automotive vehicle powertrain parts. Temperature control is assumed to involve spray evaporative cooling of powertrain parts exposed to vibration. Two hypotheses are proposed to enable construction of a practical simulation that is both accurate and computationally efficient. The first is that a dynamic correlation model for single-nozzle spray evaporative cooling of a flat test-piece exposed to vibration, can be used as a reasonable model for multiple-nozzle spray evaporative cooling of component parts with curved cooling surfaces of non-horizontal orientation. The second is that the transient heat diffusion properties of a particular 3-dimensional component can be replaced by a 1-dimensional (1D) equivalence. To test this hypothesis, Finite Element models for two representative parts have been constructed and used to demonstrate the quality of the 1D heat diffusion equivalence, for which a fast Finite Difference solution can be exploited. To test the accuracy of test-piece surface temperature control simulation, an experimental test facility has been built in hardware, in which the temperature of two instrumented test-pieces exposed to vibration (from a shaker) are controlled by spray evaporative cooling. Each test piece is electrically-heated and the hardware control system is configured using PID control, for which appropriate gains are selected. Detailed comparisons of temperature control by hardware and simulation are given for the two test-pieces under static and dynamic conditions. Good agreement is generally obtained between simulated surface temperatures compared with measurements taken from both test-pieces. The paper shows that temperature control of a hardware-based control system using spray evaporative cooling of powertrain parts can be confidently simulated.

An experimental investigation of the effect of surface vibration on spray evaporative cooling has been undertaken using a dynamic test rig.The horizontal circular test section involved a spray nozzle on top of a shaker being shaking at different frequencies and amplitudes to examine the effect of vibration on the nucleate boiling regime.The combination of the two-phase spray cooling and dynamic surface conditions has not previously been studied.The results clearly show that dynamic surface conditions influence nucleate boiling.In general, the evidence shows that vibration impedes heat transfer.The influence of amplitude and frequency are shown however not to have the same trend for all the excess temperatures.Depending on the mechanism, combinations of amplitude and frequency can either increase or decrease the heat transfer coefficient compared with the static cooling surface.

The present investigation aims to devise a thermal management system (TMS) for electric vehicles able to improve on limitations like charging time and all-electric range, together with the safety and environmental impact of the chosen thermal medium. A research gap is identified, as focus is often on addressing system thermal performance without considering that the thermal medium must not only provide suitable performances, but also must not add risks to both passengers and the environment. Thus, this work proposes an innovative cooling system including graphite sheets and a Loop Heat Pipe, filled with Novec™ 649 as working fluid, due to its exceptional environmental properties (GWP = 1 − ODP = 0) and safety features (non-flammable, non-toxic, dielectric). A three-cell module experimental demonstrator was built to compare temperatures when the proposed TMS is run with Novec™ 649 and ethanol. Results of testing over a bespoke fast charge driving cycle show that Novec™ 649 gave a faster start-up and a slightly higher maximum temperature (0.7 °C), meaning that the gains in safety and lower environmental impact brought by Novec™ 649 came without lowering the thermal performance. Finally, the TMS was tested under three different fast charge conditions (1C, 2C, 3C), obtaining maximum temperatures of 28.4 °C, 36.3 °C and 46.4 °C, respectively.

Aiming to improve on key Electric Vehicles issues, such as maximum temperature during fast charging, parasitic power and cost reduction, an innovative thermal management system for a 3-cell battery module, including a flat plate Loop Heat Pipe and graphite sheet inserts, is presented. The proposed Loop Heat Pipe, located at the bottom of the module, can transfer efficiently up to 150 W from the battery module to a remote heat exchanger connected to the HVAC chiller of the vehicle. Graphite sheets have the twofold function of promoting heat transfer along the cell plane direction, while hindering it in the transverse direction. Since Loop Heat Pipes need no electrical power, this design allows for a reduction of parasitic power consumption, as well as a reduction in the need of maintenance, with respect to standard forced air or liquid-based thermal management systems. The design feasibility was verified thanks to a Lumped Parameter Model, which was validated against in-house experimental data, using a copper/copper flat plate Loop Heat Pipe and two different working fluids, ethanol and water. Results showed that this design complies with the battery thermal requirements both at pack and cell level, with maximum temperature during fast charge and temperature spread across the cell being 31.5 degrees C and 2 degrees C, respectively, during ambient temperature tests. When compared against a liquid cold plate design, this new design lowered the maximum temperature after fast charge by 3.6 degrees C. Finally, the developed model proved able to predict the effects of design parameters on the thermal performance of the system.

A novel cooling method for Electric Vehicles battery modules by means of Loop Heat Pipe and graphite sheets is proposed. The Loop Heat Pipe is a passive two-phase system and as such it reduces the parasitic power consumed by the EV thermal management. A validated lumped parameter mathematical model has been created describing the thermo-fluid-dynamic problem and used to simulate the performance of the cooling system during highway driving and ultra-fast charging conditions. The numerical predictions show a clear potential to contain the cells’ temperature below 40°C even during ultra-fast charging, with a 3.3K peak temperature reduction in comparison to a conventional liquid cooling method. Moreover, this system adds only 8% of the battery pack mass and it shows potential parasitic power reductions of one order of magnitude.

New empirical correlation models are constructed to characterise heat transfer associated with spray evaporative cooling of vibrating surfaces - a process involving complex two-phase physics well beyond current numerical simulation capabilities. The proposed correlation models, which account for dynamic, rather than just static surface conditions as in existing models, are constructed using dimensional analysis involving the Generalized Buckingham Π-Theorem. Experimentally-measured spray evaporative cooling data is used to fit the model using the Vibrational Reynolds number and a dimensionless acceleration number which better correlate the influence of surface frequency and amplitude in the nucleate boiling regime. Different coolant flow-rates through a full-cone spray nozzle are used to cool a flat circular test-piece acting as a horizontal surface. The test-piece surface is excited by a shaker through a range of low and high vibration frequencies and amplitudes. The results show that surface dynamic effects certainly influence nucleate boiling, but they also show that surface vibration does not have the same effect for all excess temperatures - dynamic effects can either increase or decrease heat transfer depending on the heat transfer mechanism. These new models are important for thermal management in several areas, particularly involving batteries, power electronics, and electrical machines in automotive and aerospace applications.

A novel inverter and a corresponding high-powered electric machine (“motor”) were developed for a hybrid vehicle. The inverter is a compact oil cooled silicon MOSFET design rated at 25 kW that drives a frameless 6-phase 8 pole, interior permanent magnet (IPM) motor with oil (Automatic Transmission Fluid, ATF) cooling and novel windings. Both Oil- and water-cooled inverter variants were explored. Both the inverter and the motor were designed, built and tested to A-sample level. A major aim of the design was to make it possible to cool the motor, inverter and gearbox from the same oil supply. The focus of the work presented in this paper is reducing the thermal resistance of the inverter through the use of impingement jet cooling. Cooling of the electrically live tab of MOSFETs is well known to reduce thermal impedance, hence improving performance; this was achieved in the oil-cooled design by exploiting the oil’s electrical insulating property.

In this paper the development of a high power (20-25kW) 48V electric machine designed to fit into a dual clutch transmission (DCT), and a corresponding inverter are reported. The electric machine was a frameless 6-phase, 8-pole, interior permanent magnet (IPM) motor with oil (automatic transmission fluid, ATF) cooling and novel windings, and the inverter was a compact oil cooled silicon MOSFET design. Both were designed, built and tested. The motor was designed to fit into the same volume as an existing 15kW machine to enable testing in the existing gearbox, whereas the inverter was designed as a standalone unit. A major aim of the design was to make it possible to cool the motor, inverter and gearbox from the same oil supply. In this paper the benefits of running such 48V systems at powers higher than 10-15kW is discussed along with some of the design challenges encountered and the ways that they were addressed.

Heavy Duty Diesel Engine (HDDE) are between the biggest contributors to CO2 emission and ambient pollution as they are the most widely used technology for commercial vehicles and ship propulsion applications, as well as, together with reciprocating gas engines, for small medium-size distributed stationary power generation. New emission legislations in the on and off highway sectors, such as for example EURO VI and Tier 4 final, regarding NOx and Particulate Matter (PM), are also becoming year by year more stringent. For these reasons, in the last years, concerns about further engine development and efficiency improvement are of primary importance and several technologies have been studied and implemented. This review is meant to give an overview of the Organic Rankine Cycle (ORC) technology to recover wasted thermal energy in Heavy Duty Diesel Engines (e.g. exhaust gas, EGR, coolant circuit, charge air cooling, oil circuit) with particular focus on vehicle applications for on and off highway sectors (e.g. long-haul trucks, earth-moving machines, agricultural tractors). In addition, multiple different engine operating profiles in terms of torque and speed are gathered and reported for a variety of typical vehicles, in order to characterize the best system design point for the chosen application.

The ECCO-MATE Project is a European Union funded project aimed to develop a synergistic framework for cutting edge research on novel engine technologies for higher energy efficiency and lower emissions. The project partners, Ricardo plc, an engineering consulting company, and the University of Trieste, focus the research attention on waste heat recovery systems, such as Organic Rankine Cycles (ORC), which are gaining increasing interest by engine manufacturers, vehicles and ships fleet operators, because of their potential for further increasing engine efficiency and decreasing fuel consumption. In particular, in the frame of the developed research activity, the 1-D Ricardo engine simulation software WAVE has been used in order to assess novel engine concepts, both in the commercial vehicles and marine sectors. A combined engine-ORC system First and Second Law of Thermodynamics analysis has been proposed in order to study where system inefficiencies are concentrated and propose improvements, with particular focus on commercial vehicle heavy duty diesel engines. A thermo-economic analysis has been also considered. Furthermore, in collaboration with the project partners National Technical University of Athens (NTUA) and Winterthur Gas & Diesel (WinGD), an innovative low pressure Exhaust Gas Recirculation (EGR) configuration for low speed 2-stroke ship propulsion units has also been studied with the aim of reducing NOx in order to meet IMO Tier III emissions limits. ORC systems are, in this application also, a promising technology that can be used, in synergy with emission reduction systems, to recover, in particular, low temperature heat sources such as engine coolant and scavenging air, always with the aim of improving overall system efficiency while respecting new stringent emission reduction targets. The first results of the research activity show that a fuel consumption improvement up to 10% could be achieved both for commercial vehicles off-highway applications and in the marine sector, depending on the type of ORC and waste heat recovery architecture chosen and the engine considered. (C) 2017 The Authors. Published by Elsevier Ltd.

This paper reports on an investigation into the potential for a thermoelectric generator (TEG) to improve the fuel economy of a mild hybrid vehicle. A simulation model of a parallel hybrid vehicle equipped with a TEG in the exhaust system is presented. This model is made up by three sub-models: a parallel hybrid vehicle model, an exhaust model and a TEG model. The model is based on a quasi-static approach, which runs a fast and simple estimation of the fuel consumption and CO2 emissions. The model is validated against both experimental and published data. Using this model, the annual fuel saving, CO2 reduction and net present value (NPV) of the TEG’s life time fuel saving are all investigated. The model is also used as a flexible tool for analysis of the sensitivity of vehicle fuel consumption to the TEG design parameters. The analysis results give an effective basis for optimization of the TEG design.