Transcript Thermophysical Properties of a Cryogenic Pulsating Heat Pipe

Lukas Feierabend
M.S. Graduate Student
Mechanical Engineering
Thesis: Model Development and Simulation of
Central Receiver Systems for Solar Towers
Model Development and Simulation of Central
Receiver Systems for Solar Towers
L. Feierabend, S.A. Klein, D.T. Reindl
Technology Overview
Process flow diagram of the PS10 solar tower power plant. [1]
•
The heliostat field, evenly distributed on the northern hemicycle (PS10) around the tower, tracks the
position of the sun and reflects radiation onto the central receiver.
•
Heat transfer fluid (HTF) (e.g. molten salt, steam, air) flows through tubes on the receiver surface and
absorbs incident solar radiation.
•
Thermal energy is stored in large units to compensate for times when there is little or
no solar radiation and during peak loads.
•
The HTF is routed into a heat exchanger to deliver heat for a steam cycle (Rankine, Brayton).
•
This cycle converts thermal energy into electricity with a nominal output of 11 MW (PS10).
Cylindrical Receiver
Cylindrical receiver on top of the
Solar Two Power Tower in Barstow,
CA. [2]
•
Heat transfer fluid tubes are welded together to form a cylindrical
surface area.
•
Solar radiation is incident on the entire receiver circumference,
therefore the heliostat field can be extended to cover the ground
area completely around the tower. However, one has to consider that
•
•
the costs for the heliostat field account for about a third of the
total investment costs.
•
Additionally, the radiation flux incident from the southern part of
the field is low compared to the radiation reflected from the
northern mirrors.
The cylinder surface is completely exposed to the surroundings, thus
the convective and radiative heat losses are high.
Cavity Receiver
PS10 cavity-type receiver . [3]
•
The receiver cavity is formed by welded tubes, which contain the
heat transfer fluid. The receiver face approximates a semicircular
cylinder shape.
•
Reflected radiation enters the cavity through a north-facing aperture.
The heliostat field is built exclusively within the range of possible
incidence angles onto the receiver.
•
The geometry of the cavity-type receiver reduces radiative and
convective heat losses, although forced convection losses depend
significantly on the wind direction.
Project Objectives
•
•
Improvement of existing correlations for convective heat losses from receiver
surfaces with numerical modeling of air flow around different receiver
geometries.
Development of a TRNSYS model for cavity-type central solar receivers for
future incorporation into the “Solar Analysis Model”.
References:
[1]
Romero, M., Buck, R. and Pacheco J. E. (2002). An Update on Solar Central Receiver Systems, Projects,
and Technologies, Journal of Solar Energy Engineering, Vol. 124, pg. 98-108.
[2]
http://renewablefeed.googlepages.com/solarpower
[3]
http://www.worldfutureenergysummit.com/files/geyer_michael.pdf