Copper mesh. compressed and formed into porous matrices of various shapes and sizes, has been routinely used in high heat load/flux component cooling with water at the Advanced Photon Source (APS) to significantly enhance the heat transfer performance. Now the same mesh configuration is being applied to the cryogenic cooling of optical components, such as the monochromators, mirrors and multilayers with liquid nitrogen in single phase. Two-phase heat transfer is avoided to prevent flow-induced noise (vibrations and jitter) in the ultrasensitive optical components. Hence there is a great need to understand the limits of single-phase heat transfer with copper mesh using liquid nitrogen. Recently an extensive experimental program has been undertaken to investigate the heat transfer limits in conductive porous matrices with liquid nitrogen as the coolant. This paper presents the data obtained, compares the data with existing single- and two-phase correlations, and interprets the results for cryo-cooled optical component cooling applications.