REN R350 Lecture Notes - Lecture 4: Thermal Conductivity, Energy Economics, Sensible Heat
19 Sep 2016
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Document Summary
Ground heat (qg): conduction, transfer mechanism (thermal energy in the ground, hot t1 > cool t2 (temperature differential exerted over a speci c distance z1-z2), fourier"s law, linear transport equation. Sensible heat (qh): convection, mass transfer (mass ow) in slowly moving air currents. Both heat energy forms: up into the air - sensible heat - convection, down into the ground - ground heat/sensible heat - conduction, mechanisms are different. Latent heat (qe): energy used or released during phase change of water (l). John dalton (1800s): started doing measurements on evaporation, humidity sensors, rate of evaporation was greater on windy days - evaporation is proportional to the difference in humidity gradient and wind, evaporation = change in humidity x wind speed. Latent heat exchange (qe): potential energy gradient for vapour pressure, mass and energy transfer, evaporation, driving force is the vapour pressure gradient (kpa), wind (u) helps maintain vapour pressure gradient, c = coef cients (different for each situation).
