Tutorial to the basic physics behind flash steam generation Entropy of steam superheated to temperatures above saturation pointįlash Steam Generation - Fundamental Physics Wet steam, the dryness fraction and enthalpy Enthalpy of steam superheated to temperatures above boiling point Control valves and cavitation, application ratio and multi stage control valves Flash steam produced in condensate pipe lines Steam systems carries heat through pipes from the boiler to consumers as heat exchangers, process equipment etc.
Thermodynamics of steam and condensate applications Steam & condensate systems- properties, capacities, pipe sizing, systems configuration and more With higher pressure - more energy can be transferred in a steam distribution system. Note! The specific volume of steam decreases with increased pressure - and the amount of heat energy distributed by the same volume increase.The evaporation heat is 2046.53 kJ/kg at 7 bar g. The specific enthalpy of vaporization decreases with steam pressure. The heat energy (enthalpy of evaporation) needed at 7 bar g to vaporize the water to steam is actually less than required at atmospheric pressure. According the table 720.94 kJ is required to raise 1 kg of water from 0 oC to saturation temperature 170 oC. More heat energy is required to raise its temperature to saturation point at 7 bar g than needed when the water is at atmospheric pressure. In a steam distribution system the pressure is always more than 0 bar gauge.Īt 7 bar g ( absolute 8 bar) the saturation temperature of water is 170.42 oC. Steam at atmospheric pressure is of a limited practical use because it cannot be conveyed by its own pressure along a steam pipe to the points of use. = 2675.43 kJ/kg Example - Boiling Water at 170 oC and 7 bar (700 kPa) Atmospheric Pressure The total specific enthalpy for steam at 0 bar gauge is: Therefore at 0 bar g ( absolute 1 bar) the specific enthalpy of vaporation is 2257.19 kJ/kg. Therefore the specific enthalpy of water at 0 bar g (absolute 1 bar ) and 100 oC is 417.51 kJ/kg.Īnother 2257.92 kJ of energy is required to evaporate 1 kg of water at 100 oC into 1 kg of steam at 100 oC. Vacuum steam is the general term used for saturated steam at temperatures below 100☌.Įxample - Boiling Water at 100 oC, 0 bar (100 kPa) Atmospheric PressureĪt atmospheric pressure (0 bar g, absolute 1 bar ) water boils at 100 oC and 417.51 kJ of energy is required to heat 1 kg of water from 0 oC to evaporating temperature 100 oC.1) 1 bar abs = 0 bar gauge = 100 kPa abs = atmospheric pressure
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