Saturday, October 8, 2011

While Energy is Fungible, the Work is Not

Something so simple is so hard to explain.

Explaining the Kimoto equation unfortunately requires completely changing the way one looks at the atmospheric effect. In general, outgoing radiation balanced by down welling radiation of equal amounts have no net impact. The atmosphere is different. While the energy fluxes are just flows, they represent energy at a point in space and time. So while a surface flux may be matched, it has more impact at the surface. It creates more collisions in the denser environment. This is an increase in conductivity. So while two flows may pass, they are maintaining conductive conditions. Energy must be conserved, but the location of that energy is important.

In the atmosphere, there are changes in the type of energy flowing. There is latent heat from water warmed a the surface and carried aloft which does not lose its latent energy until it change phase. Conductive energy which is the number of collisions between molecules and radiant every which does not require a collision to release energy.

All three interact in the atmosphere until they revert to radiant energy and escape to space.

Each is better at transferring potential energy of a given type at a give efficiency. How easy it is to transfer heat from one boundary layer to another is extremely important. For example water is very efficient transferring energy via conduction to air that air is transferring energy to water. In an air to water heat exchanger, a conductive metal is used for the water and air boundary. Smooth tubes can be used on the water side without much loss of efficiency. On the air side, undulations are used to cause more turbulence in the air to increase the rate of collisions of the air molecules. On our oceans, heat flow from the surface increases with wave action and wind speed, more molecules contact the water's surface so more heat can be transferred. Water to air transfer of conductive heat is 1000 times more efficient that air to water, because the energy contain in every water molecule is much higher and the contact with other water molecules is much more efficient for transferring energy with in the water.

Air being orders of magnitude lower in density, takes longer to transfer energy between air molecules. Pure gases have different coefficients of heat transfer. Argon and Xenon are noble gases selected for their insulation qualities. Water vapor and carbon dioxide are not because they are better conductors. They are far from idea, but better

For example gases at atmospheric pressure separated by metal have heat transfer coefficients of 5 to 35 W/m^2K under pressure that changes to 100 to 500W/m^2K.

Under normal atmospheric conditions, water vapor and CO2 enhance the heat transfer because they can absorb energy both by conduction and through radiation. Under pressure they can transfer more and at a higher temperature they can transfer more than under lower temperature and pressure. The addition of more carbon dioxide increases the radiate energy absorbed, the number of collisions which increases the rate of conduction and increase the rate of evaporation. If there is a window for radiant heat transfer, some of this energy is transferred further from the water's surface which tends to decrease the rate of heat transfer because radiate heat transfer is not as efficient as conductive.

In the atmosphere, the adaptions of the Kimoto equation tells me, that while energy is fungible, the impact of the flows are very different, 24Wm-2 up of conductive flux is balance by 24Wm-2 down of radiative flux down from one point in the atmosphere, is not the same as 24Wm-2 up 100 meters and matched by a counter flux of 24Wm-2 at the TOA.

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