What is Steam: Definition and 534 Discussions

Steam is water in the gas phase. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Steam that is saturated or superheated is invisible; however, "steam" often refers to wet steam, the visible mist or aerosol of water droplets formed as water vapour condenses.
Water increases in volume by 1,700 times at standard temperature and pressure; this change in volume can be converted into mechanical work by steam engines such as reciprocating piston type engines and steam turbines, which are a sub-group of steam engines. Piston type steam engines played a central role in the Industrial Revolution and modern steam turbines are used to generate more than 80% of the world's electricity. If liquid water comes in contact with a very hot surface or depressurizes quickly below its vapor pressure, it can create a steam explosion.

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  1. S

    Why increasing the mass flow of steam increases its temperature

    Maybe I'm over-analysing this but if we take a simple example of a tube within which steam is flowing. Why does the temperature (and pressure) of the steam increase as the mass flow rate is increased? Is it simply because as more mass is added in the flow, the pressure within the system...
  2. mudweez0009

    Safety Injection during Main Steam Line Break

    Why is Safety Injection used during Main Steam Line Break? All that I can find is that it brings water back to the cold leg to compensate for the loss during the break.
  3. J

    How can enthalpy values be calculated for an isothermal process involving steam?

    What equations are relevant to finding the initial and final enthalpy values of an isothermal process? There is an initial dryness fraction and a heat value is also added. I know how to use steam tables to find the initial value of H but not the final. Does H even change? Thanks
  4. gfd43tg

    Solving Steam Entering Turbine Problem

    Homework Statement Exhaust gas at 400°C and 1 bar from internal-combustion engines flows at the rate of 125 mol s-1 into a waste-heat boiler where saturated steam is generated at a pressure of 1,200 kPa. Water enters the boiler at 20°C (T_σ), and the exhaust gases are cooled to within 10°C of...
  5. M

    Calculating Heat Balance & Steam kg/kg for Different Variables

    Hello, Im new here, sorry for my english, but I am in desperate need of help regarding my own experiment which i need to finish. I need to calculate steam kg/kg (flash steam maybe in english?). Basically i have entering steam temperature and pressure and exiting steam temp. and pressure from...
  6. J

    Constant Temperature Process (Steam)

    Homework Statement Homework Equations In an isothermal process, where the dryness fraction of steam is given - Does the law of P1V1 = P2V2 still stand? Mass is also given here. I know that I should not be using PV = mRT for steam. Thanks The Attempt at a Solution
  7. A

    Why not Solar -> Electrolysis -> Burn to make steam energy?

    Why not Solar --> Electrolysis --> Burn to make steam energy? Solar heat and light are both available in abundance, especially in the tropics. That being so, why is that no attempts have been made to use Solar-Electricity to split water in large amounts, into H2 and O2 to boil water to produce...
  8. C

    Equilbrium temp of ice and steam mixture

    Homework Statement You are asked to mix equal masses of of ice and steam at 0.00°C and 100.00°C respectively, What will the final temperature of the mixture be? The mixture is in a perfect insulator. ms=mass of steam mi=mass of ice LHV,s=Heat of vaporization of steam=2257J/g LHF,i=Heat...
  9. T

    Conserving Heat & Steam at Refineries: Ideas & Solutions

    after visiting my fathers job and noticing the tons of cooling towers, i wanted to know if there was a way to prevent/ conserve the lost steam and heat. At the refinery the cooling towers are used to cool water from multiple applications from varying temperatures. A water pump could replace a...
  10. gfd43tg

    What is the effect of initial conditions on steam filling a tank?

    Homework Statement A tank made of a material with negligible heat capacity is connected to a pipeline containing steam at 20 kPa and 250°C. Assume the tank is well insulated and that it has a volume of 1 m3. The tank is filled with steam until the pressure equilibrates, then it is disconnected...
  11. S

    Steam Table Calc: Enthalpy of Water

    How to calculate specific enthalpy of water if pressure and temperature are given.(by using steam table)?
  12. W

    How to calculate the speed of a steam turbine?

    For a uni project one of my concepts is to use the exhaust heat of a formula student car to boil water and use the steam to either spin a turbocharger or an electric generator to produce electricity. How would i calculate how fast i could get the turbine to spin? What equations do i use? And...
  13. F

    [Thermodynamics] How big and heavy do steam turbines need to be?

    I'm curious how large(dimensions) and how heavy/massive a steam(or other gas) turbine needs to be to extract a given fraction and amount of the energy from the fluid. For example if a power plant is producing 1GW of thermal power, how much of that can realistically be converted to electrical...
  14. S

    Steam Line Valve: Common Practice?

    hi guys...can anyone tell me that whether v use only globe valve in steamline connections in common practice?
  15. S

    Steam condensation in the presence of air

    I've been reading about this topic in a book recently and it states that when steam (water vapor) condenses on a cold surface in the presence of air, the increase in air concentration at the condensation interface causes a reduction in the steam pressure and hence, temperature. I am wondering...
  16. M

    Work done on condensing steam in a piston

    Homework Statement A cylinder has a well fitted 2.0Kg metal piston whose cross-sectional area is 2.0cm^2. The cylinder contains water and steam at constant temperature. The piston is observed to fall slowly at a rate of 0.30cm/s because heat flows out of the cylinder walls. As this...
  17. Z

    Thermodynamics, enthelpy change for steam

    Homework Statement Steam at 200psia and 600 *F [state 1] Enters a turbine through a 3-inch-diameter pipe with a velocity of 10(ft)/(s). The exhaust from the turbine is carried through a 10-inch-diameter pipe and is at 5psia and 200 *F [state 2]. What is the power output of the turbine? H1 =...
  18. T

    Calculating Internal Energy Change in Saturated Steam Throttling Process

    Homework Statement "Dry, saturated steam at 1500kPa is throttled (perhaps, expanded) to a final condition of 100kPa, dry and saturated. Calculate the change in internal energy." Homework Equations Q= ΔU + W (Q, heat supplied. U, internal energy. W, work) Steam table interpolation...
  19. R

    Air vent on steam exchangers: How?

    Often on high points of steam heated Shell&Tube heat exchangers etc. I've seen a vent specified to allow air and other non condensables to vent. e.g. this sketch http://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/14/6/fig_14_6_1.gif What's this device (I mean the one...
  20. gauss44

    Using steam to force out fumes in apartment

    So, a friend of mine just moved into a basement apartment with one window next to the front door. (I know, it sounds a lot like mine so far but it isn't.) She gets fumes coming in through the front window when they refuel the oil for the boiler room. This is because the window doesn't seal...
  21. S

    Design & Theory of Steam Platens for Rubber Curing Presses

    Hi all, I'm looking for design of steam platens for Rubber curing presses.The steam platens heat the green rubber article while curing.Other mediums such as oil,induction heating are also available,but I'm more interested in design of steam platens. There is one patent available in google...
  22. S

    Turbomachinery: number of stages and power of steam turbine

    Please help! Steam turbine. Given parameters: turbine speed, steam flow, steam inlet and outlet pressures, nozzle and blade velocity coefficients, blade angles and blade velocity. I can find all efficiencies. How could I calculate number of stages required and the actual power produced?
  23. J

    Calculating Steam Pressure in Closed Container

    I am trying to calculate the volume of liquid water i need to place in a sealed container in order to obtain 10 psi of steam pressure in that closed container. Here are the numbers: Temp: 816 C Volume of steel pipe: 154.497 ml Final pressure: 10 psi If I left out a required number...
  24. S

    Thermodynamics ( steam tables ) isentropic

    Homework Statement The power output of an adiabatic steam turbine is 5 MW. If the device can be assumed to operate as a steady flow device with isentropic expansion, determine the following: i) The dryness fraction, x, at the exit from the turbine; ii) The work output per unit mass of steam...
  25. K

    Question regarding non flow steam process

    Hi There, quite an informative forum.Im struggling with a question which reads as follows: At a certain point during the expansion cycle in a steam engine cylinder, the steam pressure was 1.1 MPa and the dryness 0.85, At the end of the expansion process the pressure was 0.28Mpa and the dryness...
  26. P

    Creating a Portable Steam Unit Without Stove Heating

    Is it possible to create a portable steam unit similar to this but without the use of the a heating element from a stove. http://vimeo.com/42042554 If so?, briefly how would one go about this? I would like to create something identical but with it's own heating unit and be hand...
  27. M

    Archived Mixing steam at different pressures

    Homework Statement steam flow through a line is 3.5 kg/s at 650 kps and .9 dry. It enters a mixing line where it exits at 800kpa, dry and saturated. The mixing steam is throttle from 2000kps to 800kpa. What is the mass of throttling steam added to have a final mixture of 800 kpa dry steam...
  28. S

    How does the steam turbine work in a solar thermal power plant?

    (English is not my native language so I apologize for the rest of the post) Hi everyone! I'm an engineering student and I'm currently working on a solar thermal project. I'm trying to model a concentrating solar power (CSP) plant according to DNI (Direct Normal Incidence) change during a...
  29. T

    Dimensions for a Steam Piston Valve

    Hello, I'm Nate, and I'm looking to build a compressed-air engine. I'm using a pneumatic cylinder with a 3" bore and a 12" stroke. That was simple enough to find. What hasn't been simple to find is a manual valve large enough to actuate it. I've found small 5-way valves on ebay and amazon, but...
  30. M

    Thermodynamic steam tables help.

    I am trying to figure out the temperature of steam when it is only dry saturated, it has the follwoing properties Mass = 0.05kg pressure = 15bar volume = 0.0076m^3 temperature = 250°C Thanks
  31. D

    Entropy change when converting water to steam

    Homework Statement At constant atmospheric pressure, 20g of water at 30C is converted into steam at 250C. Assume the heat capacity of liquid water is constant at 4.2 J/gK and the heat of vaporization at 100C is 2260 J/g. The molar heat capacity of water vapor at constant pressure is given by...
  32. T

    Adiabatic steam turbine - find the second law efficiency

    Homework Statement The Attempt at a Solution So pretty much for this question you want to find the actual work output of the turbine and the reversible work output. To find the reversible (theoretical) work output, you know that s2 = s1, so based on that information you can find what...
  33. J

    Rate of evaporation and steam tables

    Looking at the steam table below, if I understand things correctly, it will take 419kJ to bring a kg of water to the boil at 100°C and a further 2257kJ to turn all of that boiling water into steam. I assume that would have to be in an open boiler, as the pressure inside of a closed vessel would...
  34. S

    Steam turbine: typical outlet velocity

    Hello, would someone know a real-life example value of the steam velocity at the turbine outlet? Also, an example mass flow (kg/s) at outlet? The typical pressure at outlet? If you know these for both high-pressure (HP) and low-pressure (LP) stage turbines, that would be great I have tried to...
  35. T

    Find the max velocity of the steam in a steady-flow adiabatic nozzle

    Homework Statement http://i.imgur.com/4kztfIs.png The Attempt at a Solution According to the solution, the max velocity is when the entropy of state 1 is equal to the entropy at state 2. Why is this the case? My friend says it is because the system is isentropic but I am still very...
  36. T

    Using Steam Tables to Solve Part (b) - Find Initial and Final Temps

    Homework Statement The Attempt at a Solution I thought you could use steam tables to find the initial and final temperatures in order to solve part (b). The solution assumes rho = 1000kg/m^3 (or in other words all liquid). So in the steam tables: This tells me that at 100kPa the...
  37. F

    Solving Steam Problems: Calculating Heat Transfer with Thermodynamic Properties

    1.I am currently working through some steam questions and I am struggling with this problem. I am using "Thermodynamic and Transport Properties of Fluids byG.F.C Rogers and Y.R Mayhew Here are my questions as it is written: "(A) Steam at 30 bar, 375 degrees C flows through a cooling coil...
  38. Z

    Thermodynamics: Steam Tables

    A compressor adiabatically and reversibly compresses a mixture of saturated water and steam from a pressure 1.02 bar and specific volume of 1.25 m^3/kg to 0.473 m^3/kg. Calculate the fraction of steam at the compressor entrance, the exit entropy, and the exit pressure. For the fraction of...
  39. T

    Work done on piston by steam

    Homework Statement Here is the solution from the textbook: I don't understand how they can assume a linear relationship. In fact I don't even understand the math... Why does the solution take the average pressure? Isn't the relationship between pressure and volume PV^n = constant?
  40. F

    Non-flow process with steam (Constant Pressure) Part II

    In a non-flow process, 0.6kg of steam at a pressure of 10 bar and a temperature of 235°C is cooled at a constant pressure in a cylinder. After 45 minutes the cylinder contains 0.12 kg of saturated water and 0.48kg of dry saturated steam. Calculate (a)the change in internal energy, the work...
  41. F

    Non-flow process with steam (Constant Pressure)

    Question 1 In a closed system, 0.6kg of wet steam at a pressure of 5 bar and a dryness fraction of 0.2 is heated at constant pressure until the volume occupied is 0.18m3. (A)Calculate the change in internal energy, the work energy and the heat energy transferred during the process. Question 2...
  42. E

    Why the mass of steam formed during condensation is equal to 9H2

    1. Why the mass of steam formed during condensation is equal to 9H2 While studying about the lower calorific value of fuel the equation is L.C.V.= H.C.V. – heat of steam formed during combustion Now here in the book they have written that, Let ms = mass of steam formed in per kg of...
  43. T

    Thermodynamics problem - internal energy of a saturated steam?

    Homework Statement For those who are not interested in reading through the different values I get for each stage then please answer this question: What is the internal energy at state 1? When water is a saturated steam... Is it U_vap + U_liq since saturated steam has both liquid and...
  44. S

    Thermodynamics (final temperature, ice mixed with steam)

    Homework Statement If 10-kg of ice at 0 degrees Celsius is added to 2-kg of steam at 100 degrees Celsius, the temperature of the resulting mixture is? Use Joules. ANSWER: 40 Homework Equations Specific Heats: Ice = 2060 Steam = 2020 Latent Heats: Water melting = 3.33x10^5...
  45. N

    Steam Blocked: What Happens to Temperature at 3.8 bar?

    If i am supplying steam at a pressure of 3.8 bar (temperature at this pressure is 142 C) and the steam flow gets blocked. Does the temperature of the steam increase at the same pressure?
  46. N

    Is a Closed, Adiabatic Device Feasible For Work With Steam?

    2. A closed, adiabatic device claims to derive useful work by expanding 1 kg of steam from 500 C and 20 bar to 100 C and 1 bar. Do you believe this claim? Assume steam is a real fluid following the steam tables in Appendix A.III.
  47. D

    Has anyone experienced with the SST-9000 Steam Turbine by Siemens?

    Has anyone experienced with SST-9000 siemens steam turbine here? I am much astonished to see the steam parameter and the output. Main steam parameter- 290 Degree C/ 75 Bar Reheat steam parameter – 277 degree C / 9 Bar ST power Output is 1700MW. Can anyone explain, how is has been made...
  48. J

    Understanding Condensation & Vacuum in Steam Engines

    Hello everyone, Could someone help me with the following question: I'm trying to find out the equations that govern this process; why if you condense steam in a cylinder is a partial vacuum created (such as in early steam engines)? The pressure difference then causes the atmosphere to push...
  49. S

    Steam Engine Question - Help Understanding Needed

    Ok, so I have complete faith in the tried and proven laws of thermodynamics, including the part of the second law which states that it is impossible to create a heat engine working in cycle that takes in a certain amount of heat energy, and converts all the heat energy it takes in, into...
  50. A

    Design a condenser of a steam power plant

    This question is from my textbook: Thermodynamics an Engineering Approach 7ed SI Units, cengel. It is problem 10-129 and I can't seem to figure it out. Design the condenser of a steam power plant that has a thermal efficiency of 40 percent and generates 10 MW of net electric power. Steam...
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