An integral requirement of efficient electrical component design is the need to package a large number of components in a relatively small volume. Most if not all of the components in high density component packages, however, typically generate heat which cumulatively exceeds acceptable operating levels for the electrical components of interest. As such, it is necessary to cool these areas of elevated heat, or stated differently, it is necessary to cool all of these elements to substantially the same temperature at the same time.
Often times, liquid flow heat exchangers with micro-channels are used to transfer heat away from the heat sources (i.e. the electrical components). It is possible to manufacture compact, efficient micro-channel heat exchangers or cold walls for this purpose, such as the heat exchangers disclosed in U.S. Pat. No. 7,032,657 B2 to Winslow et al on Apr. 25, 2006, and in U.S. Pat. No. 7,201,217 B2 issued to Johnson et al on Apr. 10, 2007. However, such heat exchangers require as many as five or perhaps more levels of brazing during the manufacturing process. Multiple brazing steps, in addition to the performance of complex machining operations, increase significantly the overall cost of manufacturing. Moreover, heat exchangers of this design are limited in physical size (typically 24 inches×24 inches) by the very complexity of the brazing operation, with the extended brazed surface being the most susceptible to failure. Small braze failures, often discovered after the final machining operations have been performed, can result in expensive scrapped hardware.
Further, with conventional designs and those disclosed in the prior art cited above, precise and uniform temperature control can be challenging. Temperature control can be achieved across the surface of a cold plate by controlling the pressure drop across each heat exchanger element. This approach, however, requires providing input and output orifices of pre-selected dimensions at each heat exchanger element. Tight dimensional control of the input and output orifices cannot be incorporated into the designs of the prior art because the larger scale brazing operations required for heat exchanger assembly will plug or distort the orifices, thereby causing highly undesirable non-uniform cooling across the face plate. Consequently, there is an unacceptably high scrap rate as a result of post-manufacturing thermal testing failures. Finally, small braze joint leaks can occur near electrical through-holes in the assembly. These leaks are difficult to locate and repair.
An important quality control element of heat exchanger manufacturing is the thermal testing and characterization of the heat exchanger once it is assembled. Monolithic designs consisting of hundreds of micro-channel cores, as might be required for a phased array radar, cannot be thermally verified in a cost effective manner.
Hence, there is a need for a multi-element, modular micro-channel heat exchanger, and a method of manufacturing the same, for cold wall applications of any size that overcome one or more of the drawbacks identified above.