Investigation of Surface Aging Effects on the Repeatability of Saturated Pool Boiling Heat Transfer

摘要

Surface condition has been shown to be the main parameter impacting pool boiling heat transfer performance, namely heat transfer coefficient (HTC) and the critical heat flux (CHF). Many surface modification methods have been developed and studied to improve boiling heat transfer performance by creating nano/micro-scale surface topologies to induce more nucleation sites that can be activated at lower wall superheat, hence improving the HTC.In the current work, the effect of the boiling surface aging on pool boiling performance enhancement is investigated through a repeatability study. First, the design, development, and calibration of a high-accuracy pool boiling apparatus with a relatively large boiling surface area is detailed. This apparatus was subsequently used to investigate the effect of the surface oxidation and contamination on the pool boiling performance for bare copper surfaces. Tests were performed at the saturated conditions using deionized water at atmospheric pressure. The surfaces were tested seven times which amounted to 40 hours of testing. The experiment results demonstrated that the surface aging had a significant effect on the HTC, which reached up to 22% of improvement compared to the freshly prepared surface. However, its effect on CHF is minimal with at least 25 hours of tests are required to get repeatable results within 5%.