Design and Manufacture of an Oil Cooler by Additive Manufacturin

The objective of this study is to design and fabricate an oil cooler (oil to air heat exchanger) by metal additive manufacturing as a swap-in replacement for an existing aluminum oil cooler in a Case New Holland model CX55B excavator. The oil cooler must provide a heat duty of 15 kW with pressure drops less than 343 Pa and 170 kPa on the air and oil side respectively. The dimensions of the designed heat exchanger are limited to those of the existing heat exchanger (430 mm x 530 mm x 50 mm) for interchangeability. The heat exchanger must be fabricated by selective laser melting using the Concept Laser Xline 1000R machine and the design must satisfy the design constraints specific to this process. The design must sustain a burst pressure of 2 MPa and meet standard test requirements specified by Case New Holland.;To produce a design that satisfies these specifications and meets the performance requirements, a finned lenticular tube bank concept with internal heat transfer enhancement techniques (such as offset strip fins) is selected from numerous ideas presented during a brainstorming session. Lenticular tube shape offers more internal space to accommodate enhancement features and results in lower pressure drop on air side as compared to circular tubes. Due to unavailability of heat transfer and pressure drop correlations, the finned lenticular tube bank is approximated as a finned circular tube bank and analyzed over a range of tube diameters (5 mm to 10 mm) and transverse pitch to diameter ratios (1.7 to 2.5). The heat transfer and pressure drop is assumed to be equivalent for same tube diameter and transverse pitch to diameter ratio as long as the number of tubes accommodated in the constrained volume are the same. Finite element analysis of the tubes and headers is done using SolidWorks to produce a design which withstands the specified burst pressure of 2 MPa. Manufacturability of the parts with desired dimensions and features based on results of the thermal and mechanical analysis is verified based on the limitations of the Concept Laser machine. Two test prints are fabricated to test the combinations of various feature geometries and sizes.;The final design is based on the analysis and test prints and consists of 8 mm diameter lenticular tubes with a thickness of 1mm and a slenderness ratio of 0.77. Plain external fins with a thickness of 0.5 mm and an optimum fin spacing of 4.5 mm are employed on the air side while internal offset strip fins with a fin length of 10 mm are fabricated on the oil side. The external fins and internal offset strip fins are angled at 45 degrees with the tube axis for printability in selected print orientation. The design is predicted to produce a heat duty of 16.9 kW with pressure drops of 92 Pa and 26.6 kPa on air and oil side respectively. The design conforms to all the requirements from the product design specification.;Additive manufacturing enables fabrication of intricate shapes and unconventional geometries which can be optimized for heat transfer or pressure drop (such as shaped tubes or fin shapes) without being limited by the constraints imposed by conventional manufacturing. The study utilizes the design freedom offered by additive manufacturing advantageously to successfully fabricate an oil cooler consisting of small diameter shaped tubes with internal features which would be difficult to manufacture by conventional manufacturing. The successful fabrication of the oil cooler bolsters the suitability of additive manufacturing to fabricate oil coolers, however extensive testing is necessary to put these heat exchangers to practical use.