Evaporation In Water Literature Review

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CHAPTER 2 LITERATURE REVIEW 2.1 Evaporation Evaporation over large water bodies has a crucial role in the global hydrological cycle. Evaporation occurs whenever there is a vapour pressure deficit between a water surface and the atmosphere. In addition, the available energy needs to be sufficient for vaporization. Vaporization is to enable a phase change from liquid to gaseous state (Abdelrady, 2013). There are four main factors that affect evaporation which are the area of exposed water surface, the temperature increases loss, the movement if air above the water surface and the relative humidity (Magin & Randall, 1960). According to the kinetic theory of evaporation, molecules of water are in a constant state of random motion, colliding…show more content…
It can mean different things in different situations. Thermodynamic temperature is a measure of the kinetic energy in molecules or atom of substances. Evaporation can take place at any temperature. As the temperature increases, the evaporation also will increase. This is because as the temperature rises, the water molecules begin moving about more rapidly and molecules will start to escape. Besides that, warmer air also affects the speed of evaporation. Even if a body of water is cool, warm air above the water can transport some of its energy to the water molecules, allowing them to escape more rapidly. Occasions arise when a knowledge of the evaporation rate from a land or water surface is required in circumstances where direct measurements are not possible. According Linacre (1977), a simple formula use for estimate evaporation rates in various climate, using temperature data. The Penman formula is use for evaporation rate is simplified to the following Et= ((500 Tm)⁄((100-A)+ 15(T-Td)))/(80-T) mm 〖day〗^(-1) (2.3) Where: Et is the evaporation rate; Tm = T + 0.006h, h is elevation (metres), T is the mean temperature, A is the latitude (degree) and Td is the mean dew-point. In typical uses of evaporation estimates for examining the hydrology of the catchment or an irrigated field. 2.5 Relationship between Evaporation with…show more content…
The following model has been selected from the literature as it is mathematically straight forward and as a result should be relatively easy. The equation for evaporation in outdoor swimming pools (Smith, Lof and Jones, 1994) is given as: E= ((30.6+32.1 x U)(Pw-Pa))/∆H (2.4) Where E is evaporation rate in kilograms per meter squared per hour, U is the wind speed propagating over the water surfaces in metres per second, Pw is the saturation vapour pressure for specific water temperature in units of mm Hg, Pa is the saturation vapour pressure at the air dew point temperature in units of mm Hg and ΔH is the latent heat of water for specified water temperature in the tank in units of kJ per

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