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Aerosol of microscopic water droplets suspended in the air above a cup of hot tea after the water vapor has sufficiently cooled and condensed. Water vapor is an invisible gas, but the clouds of condensed droplets refract and scatter the sunlight and are thus visible. Droplets of water vapor in a pan. Demonstration of evaporative cooling.
Direct evaporative cooling (open circuit) is used to lower the temperature and increase the humidity of air by using latent heat of evaporation, changing liquid water to water vapor. In this process, the energy in the air does not change. Warm dry air is changed to cool moist air. The heat of the outside air is used to evaporate water.
Liquid water that becomes water vapor takes a parcel of heat with it, in a process called evaporative cooling. [3] The amount of water vapor in the air determines how frequently molecules will return to the surface. When a net evaporation occurs, the body of water will undergo a net cooling directly related to the loss of water.
Evaporation: The evaporation of the warmer water reduces the mass of the water to be frozen. [22] Evaporation is endothermic, meaning that the water mass is cooled by vapor carrying away the heat, but this alone probably does not account for the entirety of the effect. [5] Convection, accelerating heat transfers: Reduction of water density ...
These heat exchanges influence the climate system. The evaporative phase of the cycle purifies water because it causes salts and other solids picked up during the cycle to be left behind. The condensation phase in the atmosphere replenishes the land with freshwater. The flow of liquid water and ice transports minerals across the globe.
Evaporation: the movement of water directly to the air from sources such as the soil and water bodies. It can be affected by factors including heat, humidity, solar radiation and wind speed. [6]: Ch. 1, "Evaporation" Transpiration: the movement of water from root systems, through a plant, and exit into the air as water vapor.
Mass transfer is often coupled to additional transport processes, for instance in industrial cooling towers. These towers couple heat transfer to mass transfer by allowing hot water to flow in contact with air. The water is cooled by expelling some of its content in the form of water vapour.
The interactions of the air and water flow allow a partial equalization of temperature, and evaporation of water. The air, now saturated with water vapor, is discharged from the top of the cooling tower. A "collection basin" or "cold water basin" is used to collect and contain the cooled water after its interaction with the air flow.