Directed reflectivity, long life AMTEC condenser (DRC). Final report of Phase II SBIR program[Alkali Metal ThermoElectric Converter] Page: 11 of 33

Table 6: Effect of side wall emissivity corresponding to Tungsten Coating on FPC vs. SS
Total Heat Loss, Watts %
E = 0.3 E = 0.1 Improvement
Flat Plate 132.49 117.12 11.6%
DRC 129.47 114.54 11.5%
Cell thickness: 0.165 cm, Diameter = 6.35 cm, Length = 8.9 cm, View factor= 0.1027, Condenser emissivity = 0.02,
Hot end temperature = 873 K, Cold end temperature = 573 K.
Conclusions The analysis predicts that the DRC concept can work to reduce significantly the parasitic
heat losses from the hot zone of an AMTEC cell to the condenser for well chosen converter configurations.
It appears to do so by a combination of reduction in direct radiative heat transfer and a reduction in the
secondary transfer (via conduction) of the radiation which impinges on the cell walls. Based on a simple
extrapolation of the analysis done, the maximum reduction in parasitic heat loss that could possibly be gained
appears to be approximately 20% for a large view factor from the hot zone to condenser. View factors for
some advanced cell designs are such that reductions of 12% appear to be feasible.
Phase I Experiments
Two principal experiments were carried out to examine the performance potential of the DRC concept.
1. A mock-up cell without BASE tubes was designed to use interchangeable 'condenser' end plates. Two
plates were prepared, one as a simple flat copper plate and the other a machined copper array of right angle
corners forming a DRC surface. While an
impractical approach for a production scheme, the
DRC end cap was assembled from a set of machined,
notched, Cu strips with the thickness chosen to
produce the corner cube reflectors desired. A
drawing of an array of the type used is shown in
Figure 6. This cell was operated in several modes to
exhibit any changes in the heat transfer from the hot
zone to the 'condenser' end.
2. A standard TX' series AMTEC cell was
assembled with a machined copper DRC in place of
the conventional condenser. This cell was run in
standard operational modes and its performance
measured for comparison with cells having a
conventional condenser.
Assembled Elements
Mock-Up Cell A mock up cell based on the actual
AMTEC cell dimensions was built and investigated
to conduct a separate effects test without side view
complications due to sodium handling. A photograph
of directed reflectivity condenser (DRC) dummy test,
cell is shown in Figure 7. The cell was made out of k Elements
stainless steel and the wall thickness was 0.165 cm.
The condenser end cap had an O-ring on the inside Figure 6 DRC Perspective View also Showing Component
Stack View.


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Hunt, Thomas K. Directed reflectivity, long life AMTEC condenser (DRC). Final report of Phase II SBIR program[Alkali Metal ThermoElectric Converter], report, September 10, 2001; United States. ( accessed May 19, 2019), University of North Texas Libraries, Digital Library,; crediting UNT Libraries Government Documents Department.

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