Cooling & Heating - Andrews Sykes

DefinitionsR.H.Relative Humidity is the relationship between the amount of water vapour in air at anytemperature and the maximum amount of water vapour which the air could absorbbefore condensation takes place. Relative humidity is expressed as a percentage.Dew PointThe temperature at which water vapour in the air condenses out.Vapour pressureThe partial pressure in the air due to the presence of water.CondensationWhen humid air cools, the water vapour becomes liquid.Cold BridgeAn area of physical contact between a warm and cold surface where condensationoccurs.Surface areaL x B = m 2VolumeL x B x H = m 3Latent HeatThe heat required to evaporate or condense water with no change in temperature.K-factorHeat transmission coefficient.Wet Bulb TemperatureTemperature of humid air with a thermometer with a wet covering around the mercuryreservoir, at an air speed of +/-3 m/sec.Dry Bulb TemperatureTemperature of humid air, measured with a normal thermometer.Absolute HumidityAmount of water vapour, expressed in kg, which is present per kg. of dry air.Psychrometric DiagramA diagram in which a relation is given between the absolute and relative humidity at aspecified pressure for each temperature.PressureForce per surface unit (n/m 2 - PA).168 Click www.andrews-sykes.com