Evaluation of the thermal performance of dropwise condensation from a
semi-solid lubricant impregnated vertical condenser tube
Abstract
The quest for augmenting dropwise condensation heat transfer performance
has been the driving force behind the exploration of innovative
techniques and approaches to fulfil the desired objective. Recent
literature in condensation heat transfer unveils that dropwise
condensation heat transfer improvements from Slippery Liquid Infused
Porous Surfaces (SLIPSs) was central to the study of several researchers
because these surfaces have shown excellent droplet mobility due to
extremely low adhesion between the condensing liquid and the lubricant
infused surface, thereby, promote dropwise condensation. As part of
supplementing current research on SLIPSs, for the first time, the
present study explores the potential of a semi-solid lubricant
impregnated porous surface in enhancing the condensation heat transfer
performance of a vertical condenser tube. The results of experiments
conducted over a wide range of subcooling (5°C ≤ ΔT ≤ 65°C) in a
saturated steam environment signify that Copper tubes with semi-solid
lubricant impregnated porous surfaces are potential candidates for
enhancing dropwise condensation heat transfer coefficient when compared
to an untreated vertical Copper condenser tube. The highest enhancement
is found to be 280% at a subcooling of 40°C. Also, the semi-solid
lubricant impregnated porous surfaces are proficient in sustaining
dropwise condensation for a time period of 72 hours without any
degradation in the heat transfer performance. The method devised here
for fabricating the semi-solid lubricant impregnated surfaces is simple,
less expensive, and less time-consuming compared to the techniques
reported earlier for fabricating the SLIPSs. Additionally, in this work
an approach based on numerical optimization by a stochastic global
optimization technique, namely, Genetic Algorithm, is proposed to
retrieve the coefficients and the exponent in the mathematical
expression of overall resistance, which in turn is used to compute the
tube-side dropwise convection heat transfer coefficient.