Indoor Temperature and Humidity Loads - Calculate sensible and latent heat from persons, lights, electric equipment, machines, evaporation from water surfaces, polluting fluids and miscellaneous loads.Pressure - Online calculator, figures and tables with melting points of ice to water at pressures ranging from 0 to 29000 psia (0 to 2000 bara). Heat Loss from Open Water Tanks - Due to evaporation the heat loss from an open water tank like a swimming pool may be considerable.Evaporative Cooling - Evaporative cooling tutorial.Cooling Tower Efficiency - Maximum cooling tower efficiency is limited by the cooling air wet-bulb temperature.Area Units Converter - Convert between units of area.Air Drying Force - The drying force of air depends on the air moisture holding capacity and the water surface to air evaporation capacity.Temperature - The moisture holding capacity of air increases with temperature. Air - Humidity Ratio - The mass of water vapor present in moist air - to the mass of dry air.Air Psychrometrics - Moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content.V - velocity of air above water surface (m/s) H we - evaporation heat (enthalpy) of water (kJ/kg) X - humidity ratio in air (kg/kg) (kg H 2O in kg Dry Air) - Mollier - Psychrometric X s - maximum saturation humidity ratio in air (kg/kg) (kg H 2O in kg Dry Air) To reduce the energy consumption and to avoid moisture damages in building constructions it is common to use heat recycling devices with heat pumps moving latent heat from the air to the water in the swimming pool. Note! - during operation time the activity in a swimming pool may increase the evaporation of water and the required heat supply dramatically. remove the wet surface - possible with plastic blankets on the water surface outside operation time.increase the moisture content in the air - may increase the condensation and damage of the building constructions for indoor pools.reducing the air temperature - not a comfort solution.reducing the water temperature - not a comfort solution.reducing the size of the pool - not really practical.reducing the air velocity above the water surface - limited effect.The energy loss and required heat supply can be reduced by The heat supply required to maintain the temperature of the water in the swimming pool can be calculated as The evaporation heat (enthalpy) of water at temperature at 20 oC is 2454 kJ/kg. The evaporation from the surface can be calculated as The area of the swimming pool can be calculated as With air velocity above the water surface 0.5 m/s the evaporation coefficient can be calculated as With air temperature 25 oC and 50% relative humidity the humidity ratio in the air is 0.0098 kg/kg - check Mollier diagram. The maximum saturation humidity ratio in the air above the water surface is 0.014659 kg/kg. There is a 50 m x 20 m swimming pool with water temperature 20 oC. Required heat to cover evaporation can be calculated asĮxample - Evaporated Water from a Swimming Pool
To maintain the water temperature - heat must be supplied to the water. Most of the heat or energy required for the evaporation is taken from the water itself. Note! The units for Θ don't match since the this is an empirical equation - a result of experience and experiments. X = humidity ratio air (kg/kg) (kg H 2O in kg Dry Air)
X s = maximum humidity ratio of saturated air at the same temperature as the water surface (kg/kg) (kg H 2O in kg Dry Air) V = velocity of air above the water surface (m/s) Θ = ( 25 + 19 v ) = evaporation coefficient (kg/m 2h) G h = amount of evaporated water per hour (kg/h) G s = amount of evaporated water per second (kg/s) The amount of evaporated water can be expressed as: Evaporation of water from a water surface - like an open tank, a swimming pool or similar - depends on water temperature, air temperature, air humidity and air velocity above the water surface.
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