CNT Coating Enhances Pool Boiling Heat Transfer and Critical Heat Flux

In the nuclear reactor systems, critical heat flux (CHF) and nucleate boiling heat transfer coefficient (NBHTC) are well known as the main parameters determining the safety and efficiency of the system. Generated heat flux during the normal operation of a reactor is strongly limited below CHF. Moreover NBHTC is a key parameter representing efficiency of heat transfer. Consequently, a lot of studies on CHF and NBHTC have been conducted in various fields. Pool boiling experiments were carried out with the bare and CNT coated plate surfaces to confirm the effect of the surface characteristics, especially porosity and thermal conductivity. The experimental results showed that CHF of the CNT coated surface was enhanced by 33% as compared to the bare surface. However, degraded NBHTC was observed regardless of the similar contact angles. The enhanced CHF could be due to the increased thermal conductivity and/or the increased porosity. Degraded NBHTC is the direct result of the reduced nucleation site density, which is affected by the size of the nucleation cavity. More study is needed to confirm the emerged result and different size of the CNT will be used for coating process