Is a Vertical Increase in Pressure Possible in the Pump Stage of a Steam Engine?

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Discussion Overview

The discussion revolves around the concept of pressure changes in the pump stage of a steam engine, specifically addressing whether a vertical increase in pressure without a change in volume is feasible. Participants explore theoretical and practical implications related to steam engines and their operational mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the feasibility of a vertical increase in pressure without a corresponding decrease in volume, suggesting that pumping typically involves both pressure increase and volume reduction.
  • Another participant expresses confusion over the term "pump stage" in relation to steam engines, indicating a need for clarification on terminology.
  • A different participant proposes that maintaining a fixed volume while adding heat could allow for an increase in pressure, although they request more context and visual aids to better understand the scenario.
  • One reply provides a link for further information and describes the operational principles of a steam engine, mentioning the role of heat and pressure in moving a piston, while also noting the need for water replenishment over time.
  • A later contribution discusses the compressibility of water in the liquid phase, suggesting that while the pressure increase may not be truly vertical, it can be approximated as such due to the negligible work required to pressurize water.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the terminology or the feasibility of a vertical pressure increase without volume change. Multiple competing views and uncertainties remain regarding the mechanics of steam engines and the definitions used in the discussion.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the steam engine's operation, the definitions of terms like "pump stage," and the specific conditions under which pressure changes occur. These factors are not fully resolved within the conversation.

pivoxa15
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My textbook shows a PV diagram for a steam engine with the pump stage having no change in volume and with only a vertical increase in pressure. How can that be done. I can only imagine pumping a substance by pushing it inwards hence increasing its pressure but also reducing its volume. How can there be no reduction in volume?
 
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What do you mean by the 'pump' stage? I've never heard that term in relation to a steam engine.
 
Well, you can do this by putting heat into the system while maintaining a fixed volume. It would help to have more text and a picture though. What do you mean by a "steam engine"? Please provide more information.
 
Look at this link and re-state your question?

http://travel.howstuffworks.com/steam1.htm

The boiler tank contains very hot water and steam under high pressure. The average pressure stays about the same, depending on the amount of heat (power input) applied to the tank, and the speed and load on the engine (power output). The amount of water decreases over time requiring the engine to be refilled. Through valves, the high pressure is used to move a piston (both directions usually), and is then released. The loss of steam is replaced by the super heated water boiling and replacing the steam released on the exhaust side of the piston.
 
Assuming a condensing steam cycle:
In the liquid phase, the compressibility is very small.
Therefore the slope is very steep, but not really a vertical.
Practically, it doesn't change much to consider it as vertical: the work to pressurize the water is negligible.
 

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