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Q: Thermal Dynamics and Steam generator ( Answered ,   1 Comment )
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 Subject: Thermal Dynamics and Steam generator Category: Science > Technology Asked by: myxlplix-ga List Price: \$10.00 Posted: 10 Jan 2003 11:17 PST Expires: 09 Feb 2003 11:17 PST Question ID: 141296
 ```Setup: A steam powered generator looses ten percent of the energy from the fuel from exhaust heat and the generator extracts another 35% from the steam with the remaining energy (55%) lost when the steam is condensed to liquid water to be reused by the boiler. Question Part A: What would the formula be to calculate how much energy would be needed to "pump" the steam straight into the boiler instead of condensing it first. (Raising the "used" steam's pressure so it will flow into boiler without back flow from the boiler) Please exclude such consideration like energy loss through heat escaping through pipes or the pump not being efficent. Question Part B: What websites or other sources are available to help explain the principles involved. Please ask for clarifications if needed```
 ```Hi, myxlplix ! With the help of my resident steam buff and "Kempe's Engineers Yearbook Vol 2" Morgan Bros. Publishers, London, 1958, Chapter "Air Compression, Pneumatic Equipment, etc." by J. R. Quertier, an appropriate formula would be: 1) In an isothermal change of conditions (either compression or expansion) temperature remains constant ("iso" = equal , "thermal" = temperature). Theoretical horsepower (hp) to compress and deliver gas isothermally is: hp = (( 144 * P1 * FAD) / 33000 ) * log e (P2 / P1) where FAD is volume of gas @ initial conditions of P1 and T1 expressed in cubic feet per minute with P expressed in pounds per square inch (psi) absolute; for P = absolute pressure p = gauge pressure v = volume of gas at pressure P ( volume in cubic feet). B = barometric pressure T = absolute temperature 144 comes from the number of square inches in a square foot 33000 foot-pounds force per second is one horsepower 14.7 psi is one unit of barometric pressure at sea level ( or 1000 millibars). log e is the natural or Napierian logarithm of the mathematical expression that follows it. P1 and P2 indicate initial and final pressures; T1 and T2 indicate initial and final temperatures. P = p + B = p + 14.7 psi Note: T is assumed to be in Temperature Fahrenheit. The above equation can be used to determine the "gas" horsepower for water-cooled compressors of two or more stages with intercoolers between stages. This is fine where the gas is air; for exhaust steam, heat given to the steam in each stage would need to be removed in the next intercooler and many stages and intercoolers would be required to keep the process even approximately isothermal. However, at fairly typical steam turbine exhaust conditions the equation for the horsepower (hp) to recompress this exhaust steam (instead of putting it to a condenser) might read using the formula given above : hp = (( 144 * 1.0 * 16.6 ) / 33000 ) * log e ( P2 / 1 ) where P2 is the absolute pressure in the boiler to which the exhaust steam is to be returned (without a condenser in between). Boiler pressures can vary considerably between individual units, but for - say - 600 psi (not terribly high for some modern power stations) we can expect that the horsepower calculated above will come to about 54% of the output power of the turbine. Taking into account various losses there is obviously little advantage in using this method as opposed to condensing. 2) In an adiabatic compression no heat is added to the gas and no losses (due to friction and eddies) occur. ("Adiabatic" = without transference of heat. Chambers.) It conforms to the equation: P (v raised to power gamma) = constant, where gamma is the ratio of specific heats at constant pressure and volume. Hence: P1 / P2 = ( v2 / v1) raised to power gamma - ( T1 / T2) raised to power (gamma / (gamma-1)) Theoretical horsepower for single stage adiabatic compression is given by: hp = (( 144 * P1 * FAD) / 33000 ) (gamma / (gamma-1)) ((P2/P1) raised to power (( gamma-1) / gamma -1 )) In practice, heat is given out during compression and hence: P (v raised to the power n) = constant where n < gamma. For air n = 1.2 to 1.25 for slow speed water jacketed compressors, or n = 1.3 to 1.35 for high speed air cooled compressors. For air gamma is usually given as 1.4 and for superheated steam gamma = 1.387 ; from: "Steam Engine Theory and Practice" by William Ripper, Longman's, 1908 : but note that turbine exhaust steam is not likely to be superheated. The conclusion generally is that it takes as much or more energy to recompress ("pump") exhaust steam and feed it back to the boiler as it does to condense it and simply pump it back in as water . In addition a lot more mechanical complication is required. As for web resources, Subrata Bhattacharjee has a selection of java applets for performing various tests at: http://thermal.sdsu.edu/testcenter/javaapplets/ "You can solve just about any thermodynamic problem (at the undergraduate level) and perform parametric studies without a single line of programming with these applets. The range of topics includes basic concepts, evaluation of thermodynamic states, first law of thermodynamics for closed and open systems, second law of thermodynamics, entropy and availability analysis, power and refrigeration cycles, generalized charts, gas mixtures, air conditioning, combustion, and gas dynamics." They can be run on-line, or you can purchase the programme - free to educators. Details and a slideshow tutorial are at: http://thermal.sdsu.edu/testcenter A professional software supplier is Archon Engineering who supply Steam Tables software at US\$40.00 - download a free trial - at: http://www.archoneng.com "Steam Tables - (Metric and US units) This program provides the thermodynamic properties of water using IFC formulation for industrial use. Knowing any two properties, the user is able to completely define the properties of water/steam. Unlike most steam table programs, this program also provides the user with the point's location on the T-S diagram. Multiple points can be connected by a line, defining the user's process system. It even gives you the steam quality." A book with the same information is "Steam Tables: Thermodynamic Properties of Water Including Vapor, Liquid, and Solid Phases" by Joseph H. Keenan, Frederick G. Keyes, Philip G. Hill, Joan G. Moore January 1969 ISBN: 0-471-46501-1 which is available for £139.00 from: http://www.wileyeurope.com A very clear abstract of a paper on "Direct Solar Steam Generation" by W.D.Steinmann and W. Eck of the German Aerospace Centre's Institute of Technical Thermodynamics can be found at: http://www.meike.com/solarpaces.au/symposium/papers/Stei2.pdf Contact details for Wolf Steinmann are at the head of the article. Of other possible interest: The pressure vessels and piping division of the fluid-structure interaction committee of ASME International held a symposium at which a paper on "PRELIMINARY RELAP5 SIMULATIONS OF MULTIPLE STEAM GENERATOR TUBE RUPTURE EVENTS IN KOREA NEXT GENERATION REACTOR" was scheduled to be given by J. H. Jeong, Cheonan College of Foreign Studies; K. S. Chang, Sunmoon University, S. J. Kim, Korea Advanced Institute of Science and Technology; & J. H. Lee, Korea Institute of Nuclear Safety, KOREA http://www.cfdcanada.com/ptrans.html If that is of interest a transcript might be available through CFD Canada whose site has a wealth of articles, scientific papers, "Stories of the month" and simulations promoting their CFD modelling software FLUENT at: http://www.cfdcanada.com Keep scrolling down the very long page, and be warned the font they have used is very, very tiny. Not all links work. But generally articles are clear and easy to follow, and may help your general research. Also of general interest is the account of a steam-powered house in Victoria, Australia at: http://www.ata.org.au/45steam.htm Search terms: "steam powered generator" "thermal dynamics steam"```
 myxlplix-ga rated this answer: and gave an additional tip of: \$10.00 ```Thank you, I was thinking the answer would be something like this. My curiousity had taken hold of me over the past few weeks and I can't stand to put a subject down until I get a better understanding of it. Your answer help considerably. Please buy yourself and the resident steam buff a beer for me :) I'll probably have several other question in the comming weeks :)```
 ```Sorry - in the example: hp = (( 144 * 1.0 * 16.6 ) / 33000 ) * log e ( P2 / 1 ) the factor to convert kilowatts to horsepower was omitted. It should read: hp = 1.33 * (( 144 * 1.0 * 16.6 ) / 33000 ) * log e ( P2 / 1 ) The 16.6 cubic feet per minute relates to the weight of steam likely to be passed out of the exhaust of a turbine per kilowatt produced at the exhaust pressure of 1.0 psi absolute. Good luck with your book.```