a developing area of science attempting to evaluate water loss from plants or animals. Evaluation is usually confounded by organism controlled water loss*. The focus of this wiki is attempting to understand water loss from areas outside the control of the organism, often known as insensible water loss**. A more accurate but less manageable term could be Insensible Trans-Epidermal Water loss ( ITEWL ). This wiki understands that (with present understanding) it is impossible to define a dividing line with which to separate the organism from its epidermis***, however will attempt to elucidate mechanisms, and ultimately aid quantification in differing environments.
TEWL is a poorly understood topic due to complex factors relating to the epidermis of the plant or animal, and the complex science of evaporation and water vapor in the air. It is relevant to many real world situations affecting people, plants and animals.
Users of this wiki will probably accept that the existing science has its limitations****, and then be prepared engage in the wiki process to hasten understanding
** however medical POV defines insensible water loss to include water loss from lungs
*** for further clarity see(new page coming...)
**** thermodynamic fugacity etc
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anyone can edit here too, but Wikipedia is an encyclopedia, here More detail, Original Research and Community Building are permitted(see Wikia and Wikipedia) The host(Wikia) of this wiki is, at present, Ad-supported.
because the mechanisms of TEWL are not fully understood, the problem must first be defined, and this is probably the most major obstacle. The boundary of most(all?) organisms between internal and external is usually the epidermis. If the epidermis is to exist it must have a thickness, no matter how thin, and therefore we must therefore define the edges of the epidermis, and herein lies a problem.
The term Water Vapor Transmission Rate (WVTR) or Moisture Vapor Transmission Rate (MVTR) commonly measured in [Grams per SquareMetre per Day] is analogous with TEWL. However determining macro-conditions either side of a sheet material is far easier than micro-conditions between the inside and outside of an epidermis hour by hour, or even minute by minute.
Anyone wishing to better understand water loss through the epidermis that is incidental to major paths such as Perspiration and Transpiration. (ie, unregulated, unavoidable water loss)
Understanding the Enthalpy of a non-ideal gas (air) in a non-closed (open) system is probably important.
meteorologists are probably quite good at it but tend to hesitate the nearer to the ground where most epidermis(s) exist.
engineers tend to understand systems that are high energy, usually strong heating or strong cooling, and airbourne water becomes a small component. Energy transfer with steam is high temperature, high pressure.
The term 'Non-equilibrium thermodynamics' has produced a interesting article on Wikipedia, something relevent to the non-ideal gas that we mostly call air.
Clusters of water
two water molecules are called a dimer, but very small water droplets contain around a hundred molecules.
So what is between a dimer and an Aerosol?
Average Humidity
Is it possible to determine average Humidity ? - see Average humidity, this leads to deeper questions regarding sample rate and drift and humidity datum and (exposure: intensity or duration ? seeDurational analysis )
.pdf of lecture slides by Bob Imhof, London Southbank University and a vendor of instruments for skin bioengineering (Biox Systems Ltd) on TEWL and the Skin Barrier
David N. Blauch fundamentals of ideal gases (Java required for interactive learning)
royalsociety.org Adaptation of metabolism and evaporative water loss along an aridity gradient (note in this publication TEWL means 'Total Evaporative Water Loss')
Alergologia e Inmunologia Clinica JOURNAL:Vol.15,Nº5 OCTOBER 2000 article"Atopic dermatitis" a recomendation of Temperature and Humidity for patients under section 'General hygienic measures' of 18degC@50%rh.Note:this Geographical region is Spain.
Added by Smalldrops
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