Validation and Design of Heavy Vehicle Cooling System with Waste Heat Recovery Condenser

Abstract

The idea of recovering waste heat, and using it for some useful purpose, is certainly not new. Within vehicular applications, most people are aware, perhaps unknowingly, of some form of waste heat recovery technology. The simplest of these forms is most-likely the utilization of engine waste heat for the purpose of cabin heating. In this instance, the waste heat engine coolant stream simply transfers heat to the cabin, instead of outside air, in order to provide the desired level of passenger comfort. Another common, and more complex, form of waste heat recovery is the use of a turbocharger. In this instance, some of the waste heat from the exhaust stream is used to drive a compressor, via an exhaust-driven turbine, for the purpose of increasing the aerobic potential of an internal combustion engine, which in turn increases its power output. This evolution of waste heat recovery technology from simple thermal waste heat utilization, to thermal mechanical waste heat utilization with the automotive industry is an evolutionary path not unique to this industry, and has subsequently taken place in other areas outside of on-road applications. Of ABSTRACTFuel efficiency for tractor/trailer combinations continues to be a key area of focus for manufacturers and suppliers in the commercial vehicle industry. Improved fuel economy of vehicles in transit can be achieved through reductions in aerodynamic drag, tire rolling resistance, and driveline losses. Fuel economy can also be increased by improving the efficiency of the thermal to mechanical energy conversion of the engine. One specific approach to improving the thermal efficiency of the engine is to implement a waste heat recovery (WHR) system that captures engine exhaust heat and converts this heat into useful mechanical power through use of a power fluid turbine expander.Several heat exchangers are required for this Rankine-based WHR system to collect and reject the waste heat before and after the turbine expander. The WHR condenser, which is the heat rejection component of this system, can be an additional part of the front-end cooling module. Packaging this WHR condenser as part of the front-end cooling module can be an engineering challenge given the tight underhood environment where the current powertrain cooling components are already near system-capable thermal limits. This paper shows how Lattice Boltzmann Method based simulations using highly-detailed vehicle geometry were utilized in the development of the heat exchanger architecture used to meet peak cooling needs as well as provide sufficient cooling airflow to the WHR condenser under all operating conditions. Heat exchanger results from the simulations are shown to compare well to cooling test measurements in a fully-climatic vehicular wind tunnel.

Numerical characterization under uncertainties of a piston expander for exhaust heat recovery on heavy commercial vehicles

“…A trade-off due to weight, packaging, fan engagement and aero complexities must be found. Designing a compact cooling system is also a main challenge to reach the expected fuel consumption reduction [16]. Exoès decided to use the existing ICE cooling loop to avoid an additional front radiator and to be compatible with all the different truck cooling architectures.…”

Transient performance evaluation of waste heat recovery rankine cycle based system for heavy duty trucks

“…A high attention is paid to the evaporators in order to accurately predict the steady state and dynamic performance of those components (corresponding to the model presented in section 3.3.3). In this paper, a finite volume approach has been chosen to implement the continuous set of equations (equations 6,7,8,9). Figure 9 shows the schematic of the discretized model.…”

“…However, before the Rankine cycle based system can be applied to commercial vehicles, the challenges of its integration have to be faced. The work done in [8] and [9] show that one of the main limitation is the cooling capacity of the vehicle. But other drawbacks, such as the back pressure, weight penalty or transient operation should not be minimized [10,11].…”

Experimental and Numerical Characterization of the Sliding Rotary Vane Expander Intake Pressure in Order to Develop a Novel Control-Diagnostic Procedure

“…In the first case, the condenser acts as a further radiator so its dimensions and frontal area can be relevant. Moreover, the package of the condenser as part of a front-end cooling module represents an engineering challenge as the thermal limits have been quite reached by the current power train cooling components located in a tight under hood environment [28]. On the contrary, in the second and third case, the liquid coolant ensures a downsizing of the condenser but the coolant must be refrigerated by the external air in an additional radiator [29].…”