Abstract
Estimating rate of evaporation from undisturbed water surfaces to moving and quiet air has been the topic a vast number of research activities. The obvious presence of various shapes of gravity waves on the water body surfaces was the motivation of this experimental investigation. In this investigation experimental measurements have been done to quantify evaporation rate from wavy water surfaces in free, mixed and forced convection regimes. The effects of a wide range of surface gravity waves from low steepness, round shaped crest with slow celerity, to steep and very slight spilling crest waves, on the water evaporation rate have been investigated. A wide range of \({\text{Gr}}/{\text{Re}}^{2} (0.01 \le {\text{Gr}}/{\text{Re}}^{2} \le 100)\) was achieved by applying different air flow velocities on a large heated wave flume equipped with a wind tunnel. Results reveal that wave motion on the water surface increase the rate of evaporation for all air flow regimes. For free convection, due to the effect of wave motion for pumping rotational airflows at the wave troughs and the dominant effect of natural convection for the air flow advection, the maximum evaporation increment percentage from wavy water surface is about 70 %. For mixed and forced convection, water evaporation rate increment is more sensitive to the air flow velocity for the appearance of very slight spilling on the steep wave crests and the leeward air flow structures.
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Abbreviations
- d :
-
Still water depth (m)
- g:
-
Gravitational acceleration (m/s2)
- Gr :
-
Mass transfer Grashof number
- H :
-
Wave height (m)
- k :
-
Wave number \(\left( {1/{\text{m}}} \right)\)
- L :
-
Wave length (m)
- L c :
-
Characteristic length along the test chamber (m)
- \(\dot{m}_{e}\) :
-
Evaporation rate of water \(\left( {{\text{kg/m}}^{2} \;{\text{h}}} \right)\)
- Nu :
-
Nusselt number
- P :
-
Pressure (Pa)
- \(P_{v,s}\) :
-
Saturated vapor pressure at the water surface
- \(P_{v,\infty }\) :
-
Saturated vapor pressure at the ambient air
- Re :
-
Reynolds number
- S :
-
Stroke of the paddle
- T:
-
Wave period \(({\text{s}})\)
- V :
-
Velocity of air \(\left( {{\text{kg}}/{\text{m}}^{3} } \right)\)
- ρ :
-
Density \(\left( {{\text{kg}}/{\text{m}}^{3} } \right)\)
- μ :
-
Dynamic viscosity \(({\text{Ns}}/{\text{m}}^{ 2} )\)
- \(\bar{\rho }\) :
-
Mean mixture density of air \(\left( {{\text{kg}}/{\text{m}}^{3} } \right)\)
- σ :
-
Paddle frequency
- g:
-
Moist air property including dry air and water vapor
- s:
-
Properties at the surface of the water
- ∞:
-
Average properties at the ambient air
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Acknowledgments
The authors wish to express their sincere thanks to Ferdowsi University of Mashhad, who has financially supported the project (Grant No. 1/16560).
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Jodat, A., Moghiman, M. & Shirkhani, G. An experimental investigation on the effects of surface gravity waves on the water evaporation rate in different air flow regimes. Heat Mass Transfer 49, 1823–1830 (2013). https://doi.org/10.1007/s00231-013-1211-2
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DOI: https://doi.org/10.1007/s00231-013-1211-2