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This paper reports tests to determine the effect of R- l34a-oil mixtures on condensation in a 1.32 mm hydraulic diameter extruded aluminum tube used in automotive refrigerant condensers. The tests were performed at 8 kW/mz heat flux for 600, 1000, and 1800 kg/m2s mass velocity with 3.25,6, and 10% oil concentration (by mass). At low vapor qualities, oil increases the condensation coefficient (h), and at vapor qualities above 50%, oil reduces the h-value. The h-reduction is more severe at increased oil content. Oil increases the pressure gradient, and the pressure-gradient increase is more severe at higher oil concentration.

This paper assesses present automobile radiator design technology and suggests design improvements for future radiators. Primary emphasis is given to copper/brass (cu/br) radiators and a comparison of their performance characteristics with brazed aluminum and expanded tube-and-fin types. A rational assessment of failure mechanisms is presented and these are related to observed failure modes. A heat transfer design computer program is used to predict core weight for different material thicknesses, tube pitches, and fin spacing. This work shows that cu/br cores can be weight competitive with aluminum cores. Design improvements are proposed and discussed. The design improvements are applicable to the currently used tube-and-center construction. The objectives of the improvements include lower weight and material cost, reduced assembly cost, and greater reliability. Factors affecting reliability include corrosion, material stress, mechanical design, and joint strength.