Published on April 22, 2014
Steam Formation Unit - 4
Some important terms Liquid that is not about to vaporize, is called Compressed liquid. Liquid that is about to vaporize, is called Saturated liquid.
A vapour that is about to condense is called Saturated vapor. A vapor that is not about to condense (i.e., not a saturated vapor) is called a superheated vapor.
At a given pressure, the temperature at which a pure substance changes phase is called the saturation temperature Tsat. Likewise, at a given temperature, the pressure at which a pure substance changes phase is called the saturation pressure Psat.
Formation of steam
Graphical representation of formation of steam
h-s Diagram or Mollier Diagram
IMPORTANT TERMS RELATING STEAM FORMATION Sensible heat of water (hf ) It is defined as the quantity of heat absorbed by 1 kg of water when it is heated from 0°C (freezing point) to boiling point. It is also called total heat (or enthalpy) of water or liquid heat invariably. Latent heat or hidden heat (hfg). It is the amount of heat required to convert water at a given temperature and pressure into steam at the same temperature and pressure. It is expressed by the symbol hfg.
• Superheated steam. When steam is heated after it has become dry and saturated, it is called superheated steam and the process of heating is called superheating. Superheating is always carried out at constant pressure. The additional amount of heat supplied to the steam during superheating is called as ‘Heat of superheat’ • Total heat or enthalpy of wet steam (h). It is defined as the quantity of heat required to convert 1 kg of water at 0°C into wet steam at constant pressure. It is the sum of total heat of water and the latent heat and this sum is also called enthalpy. Where Cps is the specific heat of superheated steam at constant pressure.
Dryness fraction or Quality (x). The term dryness fraction is related with wet steam. It is defined as the ratio of the mass of water vapour in steam to the mass of steam containing it. It is usually expressed by the symbol ‘x’ or ‘q’. Where mg and ml are the masses of vapour and liquid respectively in the mixture. lg g mm m x
We can also write
Constant quality lines
Steam table is a tabular presentation of properties such as specific enthalpy, entropy, internal energy and specific volume at different saturation pressures and temperatures. Steam table may be on pressure basis or on temperature basis. The table on pressure basis has continuous variation of pressure and corresponding to it : saturation temperature (Tsat), enthalpy of saturated liquid (hf), enthalpy of saturated vapour (hg), entropy of saturated liquid (sf), entropy of saturated vapour (sg), specific volume of saturated liquid (vf), specific volume of saturated vapour (vg), internal energy of saturated liquid (uf), internal energy of Steam Tables
Dryness fraction measurement: In the measurement of quality, the object is always to bring the state of the substance from the two-phase region to the single-phase or superheated region, where both pressure and temperature are independent. It can be measured either by adiabatic throttling or electric heating.
Throttling calorimeter: In the throttling calorimeter, a sample of wet steam of mass m and at pressure p1 is taken from the steam main through a perforated sampling tube. Then it is throttled by the partially- opened valve to a pressure p2, measured by mercury manometer, and temperature t2, so that after throttling the steam is in the superheated region.
The initial state (wet) is given by p1 and x1, and the final state by p2 and t2 (superheated). Now With p2 and t2 being known, h2 can be found out from the superheated steam table. The values of h1 and hfgp1are taken from the saturated steam table corresponding to pressure pi. Therefore, the quality of the wet steam xi can be calculated.
Electric calorimeter: The sample of steam is passed in steady flow through an electric heater, as shown. The electrical energy input Q should be sufficient to take the steam to the superheated region where pressure p2 and temperature t2 are measured. If I is the current flowing through the heater in amperes and V is the voltage across the coil, then at steady state Q = VI x 10-3 kW. If m is the mass of steam taken in t seconds under steady flow condition, then the steady flow energy equation for the heater (as control volume) gives
w1h1+ Q = w1 h2 where w1 is the steam flow rate in kg/s (w1 = m/t kg/s) So, h1+ Q/w1= h2 With h2, Q and w1 being known, h1 can be computed. Now h1 = hfp1 + x1hfgp1 Hence x1 can be evaluated.
Discrete element method modelling (DEM) has proven over many years to be a powerfu...
Segregation Testing to confirm packer isolation and well integrity. Monitor w...
A small presentation of History matching and a case study on it. Also on Gas mater...
Steam and Its Properties Definition and Introduction Steam is the gaseous phase of water. ... Formation of Steam temperature-Enthalpy Diagram t-h diagram)
Steam is water in the gas phase, which is formed when water boils. Steam is invisible; however, "steam" often refers to wet steam, the visible mist or ...
Viele übersetzte Beispielsätze mit "steam formation" – Deutsch-Englisch Wörterbuch und Suchmaschine für Millionen von Deutsch-Übersetzungen.
Steam reforming of natural gas - sometimes referred to as steam methane reforming (SMR) - is the most common method of producing commercial bulk hydrogen.
Soccer Manager 2016 ... Devs need to learn how to use the Steam API: ... why did you remove the feature where we could make our own formation?
Welcome to Soccer Manager ... Steam locks up ... Nuer, ect. in formation while I as manager of Barcelona have some nobodies becase all of my important ...
Steam Workshop: Total War: ... ability/formation, ... Improved Roman Animations and Formations Mod. Subscribe. Subscribed.
Le groupe Steam France réalise et installe vos équipements et accessoires de stérilisation, désinfection et péristerilisation dans les hopitaux et ...
Standard heat of formation or standard enthalpy change of formation. How heats of formation are calculated.