REACTOR DYNAMICSFrontsSpontaneous Oscillations and Patterns :

Luss et al (1991)Above: mult. of homogeneous and front solutions in controlled wireBelow: A back-and-forth travelling pulse

Left: A hot pulse rotating around Ni ring during H2 oxidationRight: A travelling pulse during CO oxidation in a bed (feed from left; Hlavacek et al)

Spatiotemporal patterns in CO oxidation on Pd/GFC(Sheintuch et al, 2003)

CO oxidation over a disk (1.4 % CO;Tg= 225; Ts=245-251)

1 2 3

3

214216220

214217.5228

214.5218.5230.2

213228.7232

215228.8230.2

225.5229.8231

228.5231.5233

230.8232.7234.3

230.5233234.5

233.5235236.8

233.5234.8236.3

230.2232.5234

229.5231.5232.8

224.5225226

218220221

1st frame

after 7 sec

after 28 sec

Relative radial distance

Temperature oC

1

-7214216220

-6214217.5228

-5214.5218.5230.2

-4213228.7232

-3215228.8230.2

-2225.5229.8231

-1228.5231.5233

0230.8232.7234.3

1230.5233234.5

2233.5235236.8

3233.5234.8236.3

4230.2232.5234

5229.5231.5232.8

6224.5225226

7218220221

1

000

000

000

000

000

000

000

000

000

000

000

000

000

000

000

1st frame

after 7 sec

after 28 sec

Relative radial distance

Temperature oC

2

3

CO oxidation over a ring (35/22 mm,1% CO;Tg= 225; Ts=245- 251 )

1

0.1150.8

0.1030.75

0.1320.69

0.1760.632

0.2060.647

0.2350.676

0.2790.692

0.3240.706

Lower peak

Upper peak

Exit CO2 concentration, %

1

2150.1150.8

2200.1030.750.4265

2240.1320.690.411

2300.1760.6320.404

2360.2060.6470.4265

2420.2350.6760.4555

2480.2790.6920.4855

2540.3240.7060.515

1

000

000

000

000

000

000

000

Reactor temperature,oC

CO2 concentration, %

2

00

00

00

00

00

00

00

ixtinguished state

ignited state

Exit CO2 concentration, %

3

1

239

232

236

246

252

258

271

Hot spot temperature, oC

1

224239

215232

220236

230246

236252

242258

254271

1

232

236

246

252

258

271

Tignited state, oC

2

3

1

2

3

4

5

7

10

20

Feed gas temperature, oC

Number of secondary oscillations

1

2542

2483

2424

2365

2307

22410

21420

1

2

3

4

5

7

10

20

Fed gas temperature, oC

Number pulses

2

3

Figure 2: Propagating reaction waves on catalytic surfaces. (A) Temperature wave observed in CO oxidation on the surface of a supported Pd catalyst. The wave arises from coupling of the autocatalytic heat generation to heat conduction. (B) Spirals and target patterns in the isothermal NO reduction on Rh single crystal. The wave is arises from to coupling of the autocatalytic generation of empty

The Phenomenology of the Belousov-Zhabotinsky Reaction

Anodic oxidation of Nickel

Anodic oxidation of aluminum

Fig. 1Schematic drawing showing the difference between the morphogen gradient model and Turing model. (A) A morphogen molecule produced at one end of an embryo forms a gradient by diffusion. Cells know their position from the concentration of the molecule. The gradient is totally dependent on the prepattern of the morphogen source (boundary condition). (B) Adding a second morphogen produces a relatively complex pattern; but with no interactions between the morphogens, the system is not self-regulating. (C) With addition of the interactions between the morphogens, the system becomes self-regulating and can form a variety of patterns independent of the prepattern. [Art work by S. Miyazawa]

Fig. 2Schematic drawing showing the mathematical analysis of the RD system and the patterns generated by the simulation. (A) Six stable states toward which the two-factor RD system can converge. (B) Two-dimensional patterns generated by the Turing model. These patterns were made by an identical equation with slightly different parameter values. These simulations were calculated by the software provided as supporting online material. (C) Reproduction of biological patterns created by modified RD mechanisms. With modification, the RD mechanism can generate more complex patterns such as those seen in the real organism. Simulation images are courtesy of H. Meinhardt [sea shell pattern (5)] and A. R. Sandersen [fish pattern (13)]. Photos of actual seashells are from Bishougai-HP (http://shell.kwansei.ac.jp/~shell/). Images of popper fish are courtesy of Massimo Boyer (www.edge-of-reef.com).

Flow reversal operation Direct heat exchange The bed acts as regenerative heat exchanger Accumulation of the heat generated Simple design and small dimensions High temperatures for low concentrations

: 15 , : 0.5% -

Flow rate of 15 l/min and feed concentration of 0.5%Reverse-flow operation

Maximal temperature vs. Flow rateSimulationExperimental

Maximal temperature vs. ConcentrationFlow rate of 10 l/min

Inner-recirculationFlow rate of 5.7 l/min and feed concentration of 0.5%ToTnTn (Exp.)To(Exp.)

ConclusionsReverse flow and inner recirculation operations exhibit higher temperatures than the once-through operation.No difference was seen between the homogeneous and heterogeneous models.Reverse flow operation is favorable at high flow rates, and inner-recirculation operation at low flow rates.Parameter analysis showed that heat transfer coefficient and bed conductivity affect the most.

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