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In this paper an analytical and numerical study was conducted on the influence of a Non-uniform fluid inlet flow distribution on a phase-change heat exchanger. The analytical results show that the heat transfer will deteriorate as compared to the case where the inlet velocity distribution is uniform, and the degree of deterioration will decrease when the number of heat transfer units is increased. The numerical results indicated that there is more heat transfer deterioration when the fluid of the small heat capacity fluid is Non-uniformly distributed than when the fluid of the large heat capacity is Non-uniformly distributed with the same heat capacity rate ratio. A new concept of heat exchanger design is studied where the rearrangement of heat transfer area compensates for the effect of fluid flow maldistribution. This concept has the potential to enhance the heat transfer performance of automotive heat exchangers.

This paper describes the use of computational fluid dynamics (CFD) as a tool to investigate fluid flow and heat transfer characteristics in louvered fin heat exchangers that are widely used in automotive industry. CFD supplies you with information from inside the heat exchanger like spatial distributions of temperature and velocity fields between the fins. The right interpretation of this information can reduce the number of prototypes and thus save time and money in the development process. Variations of grid density, differencing schemes and boundary conditions have been performed in 2D to ensure the reliability of the numerical results. With the recommendations of the 2-D study 3-D calculations have been made. The numerical results show good agreement with experimental data. The experimental values for overall pressure drop and heat transfer have been obtained using a test facility for heat exchangers at Behr.

The paper describes a predictive tool for the determination of air and coolant temperatures and heat exchange resulting from the operation of heat exchangers, e.g., radiator or air-conditioner condenser in the underhood of automotive engines. The paper describes a detailed computational model where both the fluid streams are numerically solved and the phase change of the refrigerant is taken into account in a condenser simulation. An actual underhood simulation with interactions with a radiator is presented. A numerical simulation for a condenser is also presented. Reasonable agreement is shown with the test data.

The traditional approach for vehicle thermal development relies heavily on experimentation and experience. A virtual vehicle would be very beneficial in providing upfront engineering support which should lead to time and cost savings. To realize a useful model, the authors have based their approach on experimental data and correlations for each significant vehicle component. The vehicle has been divided into five linked modules representing powertrain cooling and cab climate. The paper describes the approach taken for each module and shows that good agreement can be found between model predictions and actual measurements.

A survey and analysis of the body sealing and interior airflow performance of a range of medium-sized passenger cars has been conducted. These studies have been carried out under static and dynamic exterior airflow conditions in a full scale wind tunnel, at airspeeds of up to 96km/h, and the ventilation performance of the vehicles characterized in terms of body leakage and extract airflow, equivalent hole size, total interior airflow and blower power requirements. In addition, more fundamental laboratory studies of the effect of interior airflow path and extract geometry have been conducted, leading to an enhanced understanding of the results obtained from the full-vehicle work.

Noise reduction of Automotive HVAC systems is a hard task because of the highly complicated and very sensitive turbulent flow in the blower fan unit. First, we identified the location of noise sources by the Sound Intensity (SI) method, then we investigated the flow pattern by the oil-mist method. As a result, two main noise generation mechanisms have been identified. One mechanism is generated by the interaction of the strong steady flow of air in the unit with the fan wheel, and the other is from the turbulent flow between the fan blades. Results: A new fan blade design was developed that had improved control of the turbulent flow, and which configuration caused a noise reduction of 2 dB-A over current blown fan systems.

Computational Fluid Dynamics (CFD) analysis has been used extensively in the design of automotive HVAC systems with the objective of optimize system performance and shorten the product development time. In this paper, the three dimensional Navier-Stokes code STAR-CD was used to determine the overall system pressure drop and velocity field, as well as, individual component pressure and velocity field. In addition, a better insight into the flow characteristics of the HVAC system has been obtained through the CFD analysis. Thermal performance of the HVAC module can also be achieved through the use of user supplied subroutines, which model the thermal effects of heat exchangers. In this paper, two specific systems were analyzed. The first system consisted of a simplified plentum, multiple inlet designs, blower, and evaporator core. The main focus of this analysis was placed on inlet design.

Analysis of an automotive engine cooling fan assembly was performed to identify the factors which cause vibration during operation and to quantify the relative contribution of these factors in the generation of forces that are transmitted through the vehicle. Both design and manufacturing aspects of the fan assembly and its components were considered. Vibration forces generated during fan operation can be generally attributed to the level of unbalance in the motor fan assembly. This unbalance results from several factors which occur throughout the fan's manufacturing process. An understanding of rotational unbalance and the factors contributing to the level of generated force is an important element in fan design. This understanding can be used to determine the most effective and economical solution to an existing vibration problem or to avoid such problems through cognizant design of future fan assemblies.

This paper summarizes the design, development, fabrication, validation, and application of a new device called the Skin Thermal Transducer (STT). The development of this instrument was driven by the demand for reliable information on human skin temperatures during contact with a warm surface on the interior of an automobile. The primary technology that enabled the development of the STT was the thermo-electric cooler (TEC) in combination with a heat sink that is used to simulate the core temperature of the human body. The STT was validated with human skin data and the agreement was within an acceptable range. The STT provides the automotive engineer with a measuring device to optimize and validate the underbody regions of the vehicle with respect to occupant thermal comfort. The STT can also be applied to optimize other automotive and non-automotive products in which the human skin touches a warm surface.

A three dimensional simulation of the flowfields within an intercooler has been performed, which included both the charge and cooling air flow. The simulation intended to demonstrate the application of numerical and computational techniques to heat exchangers with secondary heat transfer surfaces. The intercooler model selected for this work was typical of commercial designs and some experimental data was available. A multiblock grid was developed from CAD data using PROSTAR™ meshing software. The flowfield was then calculated using STAR-CD™ finite volume Computational Fluid Dynamics (CFD) software using one processor of an HP K400 computeserver. In the simulation the intercooler secondary heat transfer surfaces (fins) were replaced by conducting distributed resistance (porous media). The resistance had been calibrated by 2D CFD studies of the fin designs.

Analysis of the NOCOLOK™ aluminum brazing process is difficult because of the multiple reactions which can occur at high temperature between the components of this complex system: flux (KAIF4 and K3AIF6), oxides (principally Al2O3), and reactive alloying elements in the core or filler, such as Mg and Li. The “Mg-poisoning” phenomenon, in which the oxide removal properties of the flux are reduced, is a key concern of those using the NOCOLOK process. Thermochemical calculations demonstrate that an initial Mg content of 0.2%-0.4% coming into contact with the flux is sufficient to inhibit the desired oxide dissolution (i.e., the flux is “poisoned”). Based on thermodynamic calculations, the principal “poisoning” reaction appears to be: 3Mg (liq. soln.) + 3KAIF4 = 3MgF2 + K3AIF6 + 2AI (liq. soln.).

A correlation for total gas-side heat transfer rate has been derived from the analysis of engine data for measured heat rejection rate, frictional dissipation, and published data on exhaust port heat transfer. The correlation is related to the form developed by Taylor and Toong, and the analysis draws on this. However, cylinder and exhaust port contributions are separated. Two empirical constants are fixed to best match predicted to measured results for heat rejection to coolant and oil cooler under steady-state conditions, and also for exhaust port heat transfer rates. The separated contributions also defined a correlation for exhaust port heat transfer rate. The description of gas-side heat transfer is suited to needs for the analysis of global thermal behaviour of engines.

A suite of computer programs for engine thermal analysis and the analysis of thermal interactions with external systems has been developed. Defining an engine design is made particularly simple and the representation generated agrees well with measured data. Engine geometry, mass, and internal coolant volume are determined from a short list of key parameters and the selection of a generic template. Thermal conditions in the engine structure are modelled numerically using the lumped-capacity method. Heat exchange at boundaries with gas, coolant and oil flows are described through sub-models giving good agreement with data for global characteristics of engine behaviour. The effects of spark timing and coolant composition on heat transfer rates are taken into account, as is the effect of frictional dissipation as a heat source. Validation and applications of the model are described.

Two newly developed brazing alloys suitable for vacuum brazing (VAC) and controlled atmosphere brazing (CAB), Hogal-3571 and Hogal-3572 respectively, will be presented in this paper. Together with high strength after brazing long life corrosion properties in SWAAT were achieved. Hogal-3571 and 3572 will be compared to other high strength alloys that are already delivered by Hoogovens Aluminium, i.e. Hogai-3570 as well as AA6063 and P.A6060. This paper describes the metallurgical development of the two new brazing alloys. The chemical compositions, the strengthening mechanism, the strength as a function of the cooling rate and the TTP-diagram of the Hogal-3571 alloy will be discussed.

Thirteen GM-Harrison vacuum-brazed aluminum radiators with 3005 and “long-life” K319 alloy tubes having roughly 10 years of field service in Buffalo or Florida were examined to determine whether K319 performed as predicted in improving resistance to airside corrosion. Some 3005-tube radiators, with supplemental chromate and paint protection, had multiple tube perforations (though they did not leak). Bare K319-tube radiators, however, were in generally excellent condition. The sacrificial protection mechanism inherent in the long-life alloy proved to be very effective in prolonging service life. The corrosion observed in these field samples correlated well with that found in radiators exposed to the SWAAT accelerated test, which is used to gauge the external corrosion resistance of radiator materials

In non-corrosive flux brazing the flux contains a eutectic mixture of K3AIF6, and KAIF4, which starts to melt at around 560°C. The melted flux disrupts the existing oxide film on aluminium alloys and suppresses further oxidation thus maintaining fluidity of the AI-Si based brazing alloy. To facilitate downgauging there is a drive to develop higher strength core alloys. Using alloys with an increased level of magnesium will readily achieve significant improvements in post-brazed strength, however, the brazeability of alloys containing high levels of magnesium deteriorates as a result of magnesium reacting with the flux to form a higher melting point compound, which inhibits fluidity of the molten cladding alloy. This paper discusses the influence of brazing conditions to increase tolerance to magnesium in core alloys.

The use of computer aided engineering (CAE) analysis with the tool FLOTHERM® in conjunction with experiments is outlined as a powerful tool for system level thermal management of automotive radios. Results from experiments on a specific radio in a thermal test chamber are compared to those from the computational model at critical locations such as the CD (compact disc) optics to validate the model. Following the validation, a sequence of results for radios with and without cooling fans follows with a summary of design changes and their effect on lowering component temperatures.

Shape Energy Resources' CabinAir system is a thermal storage heating and air conditioning system that stores heat or cool energy in a phase change thermal fluid system. The CabinAir design, interconnected to the climate control system on a heavy duty vehicle, is charged from the engine coolant or air conditioning system. On an Electric or Hybrid Electric Vehicle, the CabinAir system is charged during the battery recharging time using an on-board refrigeration system or electric resistance heating element powered by the battery recharging source. Vehicle drivers can select whether to store heating or cooling energy and later retrieve it as needed for cab comfort conditioning. This product technology will reduce unwanted emissions, save fuel, and condition a vehicle's interior environment making it comfortable for driving or resting.

Load maps show the relative frequency of ambient temperatures and driving states divided in several classes. They are a means to determine the yearly average of performance or power consumption of an automotive air-conditioning system. The load maps for California, Central and Southern Europe are used to illustrate the differences in power consumption. The possible power savings using an evaporator control concept are discussed and assessed as an example for an new technique which has low effect at high load but large impact at part load conditions.

During the past few years, a new Flat Oval Tube Condenser has been developed (1) and launched in the market place (2) as a very strong and competitive alternative to the well known brazed Parallel Flow Condenser, due to its high performance and low cost. The Flat Oval Tubing used for this condenser application, seems very similar to traditional tubing used in Oval and Flat Oval Tube Radiators. However, due to higher pressure and pulsations when the A/C system is cycled on and off, it was very important to study fatigue properties to ensure a sufficient lifetime for Flat Oval Tube Condensers.