Does hydrophobicity decreases heat transfer efficiency? I was thinking about the the scaling problem in heating systems and how they could be avoided with hydrophobic surfaces, when I hypothesized if the hydrophobicity could compromise the heat transfer efficiency.
I understand that hydrophobicity of a surface is usually translated as the angle that a drop of fluid does with the surface. The higher the angle, the less the contact area and more hydrophobic is the surface.
However, I cannot visualize how will be the contact of a continuous flow of fluid (without drops). In such case, how does the hydrophobicity translates? 
Will it be translated as the distance between the molecules of the fluid and the atoms of the surface? Or as the total contact area?
If so, will the contact area of a superhydrophobic surface be almost zero and therefore the heat transfer efficiency between surface and fluid be decreased?
 A: I found this Doctoral Dissertation while searching for the answer of your questions.
There are answers to most of your questions in there.
Firstly, on page 11, there is a very clear explanation of the behaviour of the water molecules at the interface:

Water molecules near a hydrophobic surface display unique signatures of surface chemistry. A hydrophobic interface is characterized by enhanced fluctuations in water density (83). Water and the hydrophobic surface are coupled through weaker dispersive interactions, thus the cost of deforming
  the interface is lower. The hydrophobic surface accommodates larger fluctuations in water density, and cavities are more easily inserted. Water is also more compressible near a hydrophobic surface compared to a hydrophilic surface (84).

Secondly, on page 30, they explain the effect of changing hydropobicity of the surface on the density fluctuation.

We used extensive MD simulations to probe hydrophobicity at the nanoscale. In
  the first part, the hydrophobicity of chemically heterogeneous surfaces was characterized using nanoscopic signatures of hydrophobicity. The measurements used included water density fluctuations and hydrophobic probe binding. ... The results highlight an asymmetry in the effect of mutations to change surface
  hydrophobicity. Introducing a single -OH head group to a hydrophobic -CH3 quenches local fluctuations in water density, and the reverse mutation, a single -CH3 head group in a -OH surface, does not enhance local fluctuations to the same degree.

And finally, on page 68, they say that hydrophobicity has an effect on heat transfer at the interface.

We explored the effects of surface chemistry, nanoscale roughness, and the direction of heat flow on the magnitude of interfacial thermal conductance. We found that increasing the hydrophilicity of SAM surfaces by replacing -CF3 with -OH head groups results in an increase in thermal conductance that is slightly non-linear with the fraction of -OH groups. The magnitude of this non-linearity is much smaller than that displayed by other molecular measures of interface wetting (e.g., free energy of cavity formation).

