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Demand for a high thermal performance heat exchanger with good durability in a small packaging space can be very challenging. For the durability testing, the typical thermal cycle test in the lab with the fixed temperature cycles can be very time consuming and costly. In order to shorten the product development time and cost, CAE tools have been explored for the radiator thermal cycle simulation. Due to the nature of the most common failure mode, it is imperative to develop reliable methodologies so that the transient temperature, stress, and corresponding fatigue life for the product can be predicted. This paper focuses on the prediction of the metal temperature during the radiator thermal cycle using computational fluid dynamics (CFD) with conjugate heat transfer. To verify the developed temperature prediction method in CFD, thermal cycle tests were performed for three radiator samples. The test procedure and some of the test results are reviewed.

A multiple reference frame (MRF) model was developed by Gosman [1] for the prediction of flow fields induced by impellers in mixing vessels. The simulation results using this approach agree with the test data reasonably well if certain conditions exist. Many CFD engineers have adopted this approach to simulate the fan performance for automotive powertrain cooling simulations [4]. This paper describes the authors' experience using the MRF model in truck fan simulations. For the fan performance studies with a plate shroud, CFD simulation results with different sizes of rotating zones were compared with the test data. Very good agreement between the CFD simulation and the test data with plate shroud can be achieved if a properly sized rotating zone is selected. For the fan performance studies with a real shroud, a simple piece of plywood was used to mimic the engine blockage and the MRF model with one fixed-size rotation zone was used for the CFD simulation.

The US Army uses a light tactical High-Mobility Multi-Purpose Wheeled Vehicle (HMMWV) which, due to the amount of armor added, requires air conditioning to keep its occupants comfortable. The current system uses R134a in a dual evaporator, remote-mounted condenser, engine-driven compressor system. This vehicle has been adapted to use an environmentally friendly refrigerant (carbon dioxide) to provide performance, efficiency, comfort and logistical benefits to the Army. The unusual thermal heat management issues and the fact that the vehicle is required to operate under extreme ambient conditions have made the project extremely challenging. This paper is a continuation of work presented at the SAE Alternate Refrigerants Symposium held in Phoenix last June [1].

The desire to reduce environmental damage and conserve fossil fuels, as well as current and pending legislation, highlights the need for a truck air conditioner that can be operated when the truck engine is off. Different solutions to this problem have been suggested but the most viable seems to be an electrically driven vapor compression unit. Because of the lack of electrical power when the truck is not running, a practical A/C system must be energy efficient. After a number of studies and tests, a control algorithm to economically match cooling requirements to system capacities has been developed and is under test.

The PFR (parallel flow) condenser possesses numerous advantages for the automotive designer. Light weight, compact dimensions, low refrigerant charge and high performance are well documented features. In addition, the PF condenser offers a corrosion resistant materials package. This helps to assure a long life in a vehicular application where a corrosive environment is present. The corrosion resistance of the PFR condenser is documented and explained in this paper. Laboratory accelerated corrosion tests (CASS) and field testing in the harsh climate of Montreal gave evidence of the effectiveness of cathodic protection by zinc. Observed (SEM-EDS) zinc diffusion profiles at the critical areas of the condenser characterize the diffusion layers. It is clear that these zinc concentration profiles are responsible for the excellent corrosion resistance.

This paper reviews vehicular wind tunnel tests performed on a heavy truck air conditioning system utilizing refrigerants HFC-134a and CFC-12 with various condensers. Refrigerant type was found to have little effect on system temperatures but considerable effect on system pressures. Condenser design was able to compensate for the increased pressures induced by HFC-134a. Condenser design also affected refrigerant charge weights of both refrigerants. Refrigerant charge weights are important today because of limited supplies of CFCs, and will be important in the future when more costly HFC-134a becomes the standard refrigerant. Structural durability of the compact, lightweight PF® condenser was found to be acceptable for heavy truck applications. REVISIONS RECENTLY MADE to the Montreal Protocol by its signatory nations have shortened the timetable for phaseout of ozone-depleting compounds.

In 1967, Mr. P. Beatenbough presented the Thirteenth L. Ray Buckendale Lecture. The subject of his presentation was Engine Cooling Systems for Motor Trucks. In the twenty three years that have elapsed since that paper was presented, many significant advances have occurred in the field of engine cooling. This paper will explore those developments as well as discuss the functional issues involved in heavy truck cooling system design. Fundamental engineering concepts will be presented as well as simple conceptual models. Broad directions are suggested.