The fuel economy of recent small size DI diesel engines has become more and more efficient. However, heat loss is still one of the major factors contributing to a substantial amount of energy loss in engines. In order to a full understanding of the heat loss mechanism from combustion gas to cylinder wall, the effect of hole size and rail pressure under similar injection rate conditions on transient heat flux to the wall were investigated. Using a constant volume vessel with a fixed impingement wall, the study measured the surface heat flux of the wall at the locations of spray flame impingement using three thin-film thermocouple heat-flux sensors. The results showed that the characteristic of local heat flux and soot distribution was almost similar by controlling similar injection rate except for the small nozzle hole size with increasing injection pressure.
For improving the thermal efficiency and the reduction of hazardous gas emission from IC engines, it is crucial to model the heat transfer phenomenon starting from the intake system and predict the intake air’s mass and temperature as precise as possible. Previously the authors developed an empirical equation based on an experimental setup of an intake port model of an ICE in order to be implemented into the engine control unit and numerical simulation software for heat transfer calculations. The authors developed an empirical equation based on the conventional Colburn analogy with the addition of Graetz and Strouhal numbers. Introduced dimensionless numbers were used to characterize the entrance region, and intermittent flow effects, respectively.
Heat exchangers are a prolific application found in all things that concern fluid and power; they are mission-critical applications that affect overall performance in aircraft of all sizes. Yet, for years, heat exchangers have been constrained, by traditional manufacturing, in terms of limited geometric freedom and lengthy lead times. Consider the following • Heat exchangers are commonly fabricated with stainless steel and then gold brazed, which can be extremely costly • Each weld joint costs $100; in traditionally manufactured fuel and high-pressure systems, there could be hundreds of welds • There can be a lack of integration with other systems like electrical motors or conformal cooling with batteries. Assembly integration, testing, and validation are lengthy and difficult. Additive manufacturing (aka 3D printing) has opened new possibilities for thermal conductivity and heat-exchanger design that enable end users to push the limits of what is possible.
Fuel cell systems are on track to become a mainstream power generation source for various sectors. The transportation industry has a significant interest in fuel cell technology primarily for economic and sustainability reasons. During the product development of fuel cell systems, suppliers and OEMs are faced with many strategically and technically challenging questions under stringent end user requirements and economics. In order to select a competitive system topology, it is first required to understand the design criteria and limits for a respective market and application. Consequently, engineers are faced with many technical challenges especially in understanding and optimizing complex interactions of fuel cell stacks with the propulsion platforms. One practical example of this is the cold start of a fuel cell.
The force, torque, and energy methods of measurement are all in common use and should yield the same test results. Effects of steering, traction, and non steady-state tire operations are excluded from the recommended practice because they are still in the research stage. Methods of correcting laboratory data to road conditions are being developed.
Moderator - Rohit Saha, Cummins Inc. Panelists - Vitthal K. Khandagale, CUMMINS TECHNOLOGIES INDIA PVT LTD Libera Natalia La Face, CNH Industrial SpA Cedric Rouaud, Ricardo UK, Ltd. This panel discussion will focus on developments and innovations in the field of thermal management challenges of commercial vehicles. This panel will bring together subject matter experts from industry, software vendors, national labs and suppliers. Abstracts are invited in one of thermal management areas like cabin thermal comfort, fill and de-aeration of cooling systems, under-hood heat transfer and air flow management, cooling challenges of fuel cell powertrains, noise abatement and packaging. This panel will also include latest developments in physical testing, cooling system packing, software vendor, and optimization of cooling strategies to improve energy efficiency.
In recent years, because of the regulations on the use of high Global Warming Potential(GWP) HFC refrigerants, alternative refrigerants for vehicle HVAC are under development for the application in the heat pump system for vehicles. Furthermore, since the energy consumed by the HVAC system significantly affects the driving range of EVs, both the heating/cooling performance and the energy consumption of the heat pump system should be considered to use the alternative refrigerants for the EV HVAC system. In this study, R290 refrigerant is selected as working fluid in heat pump system for the EV HVAC system. Due to the flammability of R290, secondary loop heat pump system is selected to isolate the R290 cycle in a separate module. Based on the secondary loop heat pump system using R290, an integrated 1-D EV model is developed to estimate the performance and the energy consumption of the heat pump system over a driving cycle.
Carbon dioxide (CO2 or R744) is a promising next-generation refrigerant for mobile air-conditioning applications (MAC), which has the advantages of good heating performance in cold climates and environmental-friendly properties. This paper presents a simulation model of an integrated internal heat exchanger (IHX) and accumulator (Acc) using the finite volume method. The results are validated by a group of experimental data collected with different transcritical R744 mobile air-conditioner and heat pump (MHP) systems, and the error was within �10%. The impacts of refrigerant mass flow rate and operating temperatures on the heat transfer rate of the IHX, improvement on refrigeration capacity and the liquid level in the Acc were studied. Results show that the net benefits of IHX are significant in AC mode, while it helps preventing flooding of the compressor in MHP mode.
As OEMs look to increase thermal efficiency of their existing engine architectures there is an increased focus on the performance of the cooling system. Water jackets in combination with radiators are the main components to remove excessive heat from the engine block originating from in-cylinder combustion. The temperature reached by the engine block spans from ambient temperature up to 400 K, leading to high thermal gradients and significant failure risks. In this work, the mechanical stresses due to the thermal expansion are evaluated via 3D numerical simulations via an innovative workflow. Typically, solving for the thermal stress, requires two different meshes. In the first mesh, the fluid and solid equations are solved with a finite volume approach. In a second phase, the temperature from the first mesh is mapped onto a second mesh, to allow the thermal stress calculation with a finite element approach, leading to discretization and interpolation errors.
The piston temperature has to be carefully controlled to achieve effective and efficient thermal management in the internal combustion engines. One of the common methods to cool piston is by injecting oil from the crankcase underside to the piston under-crown area. In the present study, a novel 3-D multiphase thermal-fluid coupled model was developed using the commercial CFD software SimericsMP+ to study the piston cooling using the oil jet. In this model, an algorithm was proposed to couple the fluid and solid computation domain to account for the different timescale of heat transfer in the fluid and solid due to the high thermal inertia of the solid piston. The heat transfer coefficient (HTC) and reference temperature were mapped to the piston top surface and the liner temperature distribution was also used as the boundary condition. The temperature-dependent material properties, piston motion, and thermal contact resistance between the ring and piston were also accounted for.
In the context of the improvement of energy management optimisation on PHEV applications, thermal management is playing a great role. The electrical energy absorbed by the electric ancillaries to heat up or cool down the electric components and the cabin can be as high as the electrical energy required to move the vehicle. PHEV presents a high level of complexity of the cooling/heating circuit architecture with several circuits and multiple pumps and valves due to the presence of high temperature, low temperature and cold temperature cooling circuits. Those circuits can be coupled or not depending on the ambient temperature and driving conditions. In order to minimise the electrical energy used to heat up or cool down components and cabin using electric heater and/or heat pump, waste heat recovery from electric components, electric air conditioning compressor with chiller.
We have performed a numerical and experimental study on the impact of adding heat pipes to a PCM based battery thermal management system. Phase change materials (PCMs) are used as a battery thermal management system to absorb heat by melting in a specific temperature range, leading to a temporary constant and uniform temperature around battery cells. They also can be used as mechanical support for battery cells and safety measure to prevent fire propagation in case of thermal runaway. The main drawback of these materials is their low thermal conductivities. Our proposed approach is the integration of heat pipes with PCM as a hybrid system to take advantage of both technologies including the temperature peak absorption and structural support of PCM along with very high effective thermal conductivity, temperature uniformity and passive operation of heat pipes. Flat heat pipes integrated with PCM are tested with 18650 cells under various C-rates and ambient temperatures.
Under cold operating conditions (ambient temperature of 20oF), the electric energy consumed to provide occupant comfort and system thermal management in battery electric vehicles (BEVs) can reduce driving range up to 40% compared to the baseline operation in a 75oF ambient temperature. In hot environments (ambient temperature of 95oF), BEVs can suffer a 15-20% driving range penalty from HVAC energy consumption compared to the baseline. Effective integration of newly designed thermoelectric (TE) systems that use available TE materials provide performance enhancement in both R1234yf and CO2 HVAC systems. This presentation discusses subsystem designs, design tradeoffs and performance gains. The TE subsystems utilize an integrated design with cycle and material fabrication advancements to improve the coefficient of performance (COP) and reduce the size of HVAC systems that operate with low global warming potential (GWP) refrigerants.
The pace of change that the automotive industry is experiencing in the recent years is unprecedented. For legislative and market driven reasons, the automobile is moving away from the internal combustion as the sole means of propulsion towards more innovative system architectures. Almost every new vehicle is electrified to a certain degree, ranging from mild hybrids to battery and fuel-cell electric vehicles, which significantly increases the number of components and systems that need to be integrated and balanced to ensure the maximum efficiency of the powertrain. Combining this with the increased amount of vehicle variants present on the market, it becomes clear that engineers must consider many scenarios. Powertrain components, such as e.g. the battery, e-machine, power electronics can operate safely and efficiently only in a very narrow temperature band. Therefore, thermal management is critical.
Heat pumps are used in BEV for energy-efficient heating and to increase range in winter. At low temperatures, frost forms on the exterior heat exchanger surface, which leads to a decline in the system efficiency. The heat capacity is no longer able to be covered by the heat pump and the heat exchanger has to be defrosted. Subsequently, the heat pump operation can start again, which is referred as cyclic frosting / defrosting. Up to now, heat exchanger frosting is prevented in vehicle heat pumps series production by limiting the suction pressure of the heat pump depending on the dew point of the air. A cyclic frosting / defrosting strategy offers a large potential for a more energy-efficient heating and higher winter range. The presentation provides an overview of the three-year research project �cyclic frosting / defrosting of vehicle heat pumps�. In the beginning, the frosting behavior of different micro port extruded tube heat exchanger geometries and coatings is evaluated.
The reliability of Li-ion batteries (LIBs) is essential for electric vehicles (EVs) safety due to the fast charging/discharging, environmental dynamic loads and high temperature usage involved in LIB service. Among the LIB safety hazards, thermal runaway is recognized as the most critical one due to its rapid development and severe safety threat. Nowadays, the most common safety monitoring method is to measure the surface temperature and disconnect the LIBs when it reaches the threshold. Due to the thermal resistance, measurement on the battery surface cannot reflect the electrode temperature, which is crucial for LIB safety. Besides, most existing surface temperature-based LIB safety management methods neglect the difference in different abusing conditions and cannot provide customized LIB management. In our work, resistance temperature detectors (RTDs) were embedded into LIBs with additive manufacturing.
Heat exchangers are a prolific application found in all things that concern fluid and power; they are mission-critical applications that affect overall performance in aircraft of all sizes. Yet, for years, heat exchangers have been constrained, by traditional manufacturing, in terms of limited geometric freedom and lengthy lead times. Consider the following � Heat exchangers are commonly fabricated with stainless steel and then gold brazed, which can be extremely costly � Each weld joint costs $100; in traditionally manufactured fuel and high-pressure systems, there could be hundreds of welds � There can be a lack of integration with other systems like electrical motors or conformal cooling with batteries. Assembly integration, testing, and validation are lengthy and difficult. Additive manufacturing (aka 3D printing) has opened new possibilities for thermal conductivity and heat-exchanger design that enable end users to push the limits of what is possible.
Fast and ultra-fast charging batteries are key enablers for wide public acceptance of electric vehicles (EV's). Development of new, highly-efficient, and safe thermal management techniques are a fundamental challenge. Immersive single and two-phase cooling technologies are very promising, and require development of new fluids. In this presentation, Arkema proposes novel, highly effective, non-flammable, dielectric, low-pressure and environmentally friendly fluids for both single-phase liquid and two-phase immersive cooling applications.