Deserts are usually very dry. Despite that is the goal to extract water from the humid sky via a water catcher. The wate

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Deserts are usually very dry. Despite that is the goal to
extract water from the humid sky via a water catcher. The water
catcher consists of a flat surface/plate which is covered with a
special film to facilitate heat radiation. During the night, when
its cold, the heat from the plate will radiate in to the sky. The
surface reduces in temperature for the water vapor to condense
(sometimes freeze) on the surface. The water will later during the
early morning be stored before it evaporates in the air. In this
assignment, we are going to calculate how much water was gathered
during the night.
Lets assume that the area of the water cather’s surface is 1m2,
the water content in the air is the same during the day and the
night as well as the condensation of the water vapor does not
affect the air’s water contents. The convection heat transfer
coefficient ,αk, of air is set as 5 W/(m2 *K), the emissivity can
be set as ε. The latent heat of vaporization of water,r, is assumed
to be 2480 kJ/kg and the enthalpy ,c, is 335 kJ/kg. The relative
humidity is 20% during day time when the temperature is tday . F12
can be set as ε. During clear nights, the estimated temperature is
-80°C Calculate: The temperature of the water cather’s surface in
the equilibrium state during the night The diffusion heat transfer
coefficient αd [W/(m2*K)] Massa of water per m2 that is possible to
gather during 8 hours in night time
Given parameters: tday= 38°C, ε= 0.86 , tnight=18°C