This experimental study shows the behavior of a directly irradiated, high temperature, solar receiver seeded with a low concentration of carbon black particles as the radiation absorbing media in the presence of air or nitrogen as the working fluid. Experiments were conducted in the presence of highly concentrated solar energy with an energy flux of up to $3MW∕m2$ at the aperture of the receiver. 99.9% of the particles had an equivalent diameter of $<5μm$, but the remaining larger agglomerates accounted for 51% of the overall projected surface area. The molar ratio of carbon to gas in the fluid entering the receiver was 0.004–0.008. The heat transfer from the solar radiation to the working gas was accomplished almost exclusively via the particles. The receiver behavior during steady-state operation was evaluated. The receiver gas exit temperatures achieved during the experiments were between 1000 and $1550°C$. When nitrogen was used as working gas, its exit temperature exceeded the average wall temperature, whereas when air was used, its exit temperature was lower than the average wall temperature. The air flow may have been heated to some extent by the receiver walls, whereas in the case of nitrogen, the particle-to-gas heat transfer was dominant throughout the receiver. When the gas exit temperature was above $1200°C$, the particle seeded nitrogen flow absorbed 12–20% more energy than particle seeded air flow under the same operating conditions (insolation, particle load, flow rate, close proximity in time). The air tests reached high exit temperatures despite the reduction of particle concentration due to combustion. This indicates that heat transfer mainly occurs over a relatively short time period after the particle seeded flow enters the cavity close to the receiver aperture, before significant particle burning takes place. The energy due to carbon combustion was 3–5% of total energy absorbed in the high temperature air experiments. The carbon particles’ oxidation rate in the presence of molecular oxygen was found to be significantly lower than values documented in the literature for high temperature carbon black combustion in air. The high solar flux, which promotes very high $radiation→particle→gas$ heat transfer rate, might account for this retardation.

1.
Karni
,
J.
,
Kribus
,
A.
,
Doron
,
P.
, and
Rubin
,
R.
, 1997, “
The DIAPR: A High Pressure, High Temperature Solar Receiver
,”
ASME J. Sol. Energy Eng.
0199-6231,
119
, pp.
74
78
.
2.
Steinfeld
,
A.
, 2005, “
Solar Thermochemical Production of Hydrogen-A Review
,”
Sol. Energy
0038-092X,
78
, pp.
603
615
.
3.
Bertocchi
,
R.
,
Karni
,
J.
, and
Kribus
,
A.
, 2004, “
Experimental Evaluation of a Non-Isothermal High Temperature Solar Particle Receiver
,”
Energy
0360-5442,
29
, pp.
687
700
.
4.
Klein
,
H. H.
,
Rubin
,
R.
, and
Karni
,
J.
, 2006, “
Generation of a Radiation Absorbing Medium for a Solar Receiver by Elutriation of Fine Particles from a Spouted Bed
,”
ASME J. Sol. Energy Eng.
0199-6231,
128
(
3
), pp.
406
408
.
5.
Kogan
,
A.
,
Kogan
,
M.
, and
Barak
,
S.
, 2005, “
Production of Hydrogen and Carbon by Solar Thermal Methane Splitting III. Fluidization, Entrainment and Seeding Powder Particles Into a Volumetric Solar Receiver
,”
Int. J. Hydrogen Energy
0360-3199,
30
(
1
), pp.
35
43
.
6.
Dahl
,
J.
,
Buechler
,
K. J.
,
Weimer
,
A. W.
,
Lewandowski
,
A.
, and
Bingham
,
C.
, 2004, “
Solar-Thermal Dissociation of Methane in a Fluid-Wall Aerosol Flow Reactor
,”
Int. J. Hydrogen Energy
0360-3199,
29
, pp.
725
736
.
7.
Trommer
,
D.
,
Hirsch
,
D.
, and
Steinfeld
,
A.
, 2004, “
Kinetic Investigation of the Thermal Decomposition of CH4 by Direct Irradiation of a Vortex-Flow Laden With Carbon Particles
,”
Int. J. Hydrogen Energy
0360-3199,
29
(
6
), pp.
627
633
.
8.
Haueter
,
P.
,
Moeller
,
S.
,
Palumbo
,
R.
, and
Steinfeld
,
A.
, 1999, “
The Production of Zinc by Thermal Dissociation of Zinc Oxide-Solar Chemical Reactor Design
,”
Sol. Energy
0038-092X,
67
, pp.
161
167
.
9.
Klein
,
H. H.
,
Karni
,
J.
,
Ben-Zvi
,
R.
, and
Bertocchi
,
R.
, 2007, “
Heat Transfer in a Directly Irradiated Solar Receiver∕Reactor for Solid-Gas Reactions
,”
Sol. Energy
0038-092X,
81
, pp.
1227
1239
.
10.
Kogan
,
A.
, and
Kogan
,
M.
, 2002, “
The Tornado Flow Configuration-An Effective Method for Screening of a Solar Reactor Window
,”
ASME J. Sol. Energy Eng.
0199-6231,
124
, pp.
206
214
.
11.
Bertocchi
,
R.
, 2002, “
Carbon Particle Cloud Generation for a Solar Particle Receiver
,”
ASME J. Sol. Energy Eng.
0199-6231,
124
, pp.
230
236
.
12.
Yuen
,
W. W.
,
Miller
,
F. J.
, and
Hunt
,
A. J.
, 1986, “
Heat Transfer Characteristics of a Gas-Particle Mixture Under Direct Radiant Heating
,”
Int. Commun. Heat Mass Transfer
0735-1933,
13
, pp.
145
154
.
13.
Hurt
,
R. H.
, and
Calo
,
J. M.
, 2001, “
Semi-Global Intrinsic Kinetics for Char Combustion Modeling
,”
Combust. Flame
0010-2180,
125
, pp.
1138
1149
.
14.
,
P.
, and
Denning
,
R. J.
, 1996, “
Oxidation Rate of Soot Particulates by Oxygen in the Temperature Range 150–3500K Determined Using a Shock Tube
,”
J. Chem. Soc., Faraday Trans.
0956-5000,
91
(
21
), pp.
4159
4165
.
15.
Funken
,
K.-H.
,
Luepfert
,
E.
,
Hermes
,
M.
,
Bruehne
,
K.
, and
Pohlmann
,
B.
, 1999, “
Oxidation Rates of Carbon Black Particles Exposed to Concentrated Sunlight
,”
Sol. Energy
0038-092X,
65
(
1
), pp.
15
19
.
16.
Hunt
,
A. J.
,
Ayer
,
J.
,
Hull
,
P.
,
Miller
,
F.
,
Noring
,
J. E.
,
, and
Worth
,
D.
, “
Solar Radiant Heating of Gas-Particle Mixtures
,” Lawrence Berkley Laboratory Report No. LBL-22743.
You do not currently have access to this content.