  Wicking is a widely studied process across various natural and artificial
systems. A more industrially relevant configuration is when the wicking liquid
is allowed to evaporate, such as in the heat pipes and the variants, in order
to regulate the operating temperature effectively. We consider a simpler case
for investigation where liquid ethanol (kept in a container) climbs onto a thin
filter paper oriented vertically and is exposed to laboratory conditions,
facilitating mass loss via evaporation, thereby inducing the cooling effect. We
use three filter papers having different permeability values and three
diagnostics concurrently for each case in order to understand the entire
dynamics; these are optical imaging, thermal imaging, and precision weighing
scale. Results revealed a steady-state height considerably below Jurin's limit
for all the cases, indicating evaporative mass loss as the primary limiting
parameter rather than the conventional gravitational effect in such a process.
Further, thermal imaging unveiled a non-uniform temperature distribution along
the filter paper with a very peculiar temperature inversion near the mid-way of
the wicking liquid. We use this feature to improve the Constant Evaporation
Model (CEM by Fries et al) by addressing this non-linear behaviour as a
consequence of the evaporation rate being a function of the vertical position;
we term this newly proposed model Non-Constant Evaporation Model, (NCEM). In
the NCEM, we test two different power-law relations for the evaporation rate
and both seemingly capture the essential features of this dynamic process.
However, both the models do not capture the process completely and further
refinement is needed for complete understanding. Since evaporation rate is the
limiting factor, we included it in defining two new non-dimensional numbers
(Evaporation Height Number, EHN and Evaporation Time Number, ETN).
