Solar power plant: steam quality questions

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SUMMARY

The discussion focuses on the design challenges of a small solar power plant utilizing solar troughs, specifically addressing the heat transfer problem in the solar collector field. The engineer aims to transition water from 110 degrees Fahrenheit to superheated steam at 550 degrees Fahrenheit, encountering difficulties in calculating the necessary pipe length for complete vaporization. Key equations discussed include the energy required for vaporization, Qvap = mdot * hfg, where mdot is the mass flow rate and hfg is the latent heat of vaporization. The engineer seeks insights on iterating pipe length to achieve 100% steam quality during the transition phase.

PREREQUISITES
  • Understanding of thermodynamics, particularly phase change and heat transfer principles.
  • Familiarity with solar thermal energy systems, specifically solar trough technology.
  • Knowledge of steam tables for determining latent heat of vaporization.
  • Proficiency in programming concepts, particularly iterative loops for calculations.
NEXT STEPS
  • Research the calculation of heat transfer rates per unit length in solar trough systems.
  • Learn about the use of steam tables to find latent heat values for various pressures and temperatures.
  • Explore programming techniques for implementing while loops in computational models.
  • Investigate methods for optimizing the design of solar collector fields for efficiency.
USEFUL FOR

Engineers and designers involved in renewable energy projects, particularly those focused on solar thermal systems, as well as students studying thermodynamics and heat transfer applications.

CUaero12
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Hey guys, I'm an engineer working on the design of a small start up solar power plant. The solar power plant will operate using "solar troughs" instead of the traditional photovoltaic cells. In these systems water is the working fluid and sunlight is focused from a solar reflector onto a pipe containing the water. Here is an image of a typical solar trough:

[PLAIN]http://www.renewableenergyaccess.com/assets/images/story/2004/3/26/SEGS_NREL.jpg

The water is pumped through a large field of these parabolic solar troughs until it is superheated steam that is suitable to run through a turbine.

Right now I'm working on the basic heat transfer problem regarding the solar collector field and have run into a bit of a roadblock.

The water will be entering the field at 110 degrees Fahrenheit and needs to exit the field at 550 degrees Fahrenheit. I'm trying to compute how long the pipe in the field needs to be to achieve this temperature. I've got most of it down except the transitional part between liquid and steam. When the water starts to boil, the temperature will remain constant until all of the fluid is vaporized. During this time the quality of the steam will change and the volume of the fluid will be composed of liquid and vapor. I'm trying to iterate through and see how much length of field it will take before the water is completely vaporized (the quality is 100%) but am having trouble figuring out how to compute this. I want to iterate through using a while loop (while the quality of the fluid is less than 100%, keep adding one meter length of pipe to the field until this is achieved) but am stuck on figuring out exactly how.

Does anyone have any ideas or insight into the problem? Let me know if more information about the problem is needed, I can provide more details and numbers if necessary (the mass flow rate through the field is known as well as the heat of vaporization, etc.)
 
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Have you been able to figure out your heat transfer rate per unit length: Q / L ? If not, I can make some suggestions.

If so, the energy required to vaporize the water is: Qvap = mdot * hfg

where,

Qvap = heat required for vaporization
mdot = mass flow rate of water / steam
hfg = latent heat of vaporization (look up in steam tables)

Qvap = heat required for vaporization

and you can solve for length of pipe to transfer Qvap.
 

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