Mass Requirements Water Inventory The water inventory is calculated for three major radiator elements: the steam line, the radiators, and the collection gutters and condensate return line. The layout is shown in Fig. 12 along with a weight breakdown. The calculational technique is similar for the pipes and plates. The difference is in the separation of the collection gutters or pipes. It is desirable to maintain the liquid film as thin as possible. This is done by sloping the plates at 30° slope and bringing them to a drip point where the film drips directly into a collection gutter. The film thickness varies across the plate between the top and bottom of each indentation, but the average thickness is consistent across the plate. Similarly the depth in the collection gutter increases down the gutter as more condensate drips in. The gutter was divided into ten sections to do this calculation accurately. In the pipe the film flows round the walls to the bottom where it then flows down to the collection gutter. The collection gutter is divided into 30 sections in this case to accurately model this flow. An increase in slope was evaluated but it was not as beneficial as reducing the width to 5 m from 10 m. Should it prove desirable to increase the tube length for fabrication reasons while maintaining the same water inventory, the slope could be increased. A disadvantage of this technique is that the effective radiating area varies as the cosine of the angle of slope. Thus a radiator on a 5° slope is 99.7% efficient whereas at 10° slope it is only 98.4% efficient. Thus at a 5° slope we need an extra 85 m2 whereas at 10° slope we need 342. Mass of the Radiator The area of the radiator equals the load of 10 MW divided by the radiating power of the selected radiator. For the horizontal radiator with a vertical sun screen, this is 444 W/m2. The area is thus 22 522 m2. For a pipe radiator it is desirable to separate the pipes by three times their diameter which de-rates the radiating power by a view factor of 0.72 to 320 W/m2 thus the radiating area is 31250 m2. The pipe area per unit radiator area is equal to the circumference divided by the pipe separation (i.e. Tt/d or 3.142/3=1.05). Thus the pipe weight equals the radiator areaX 1.05XthicknessX density. For pipe with a 3 mm wall thickness and a density of 2.2 g/cc the total mass is 220 000 kg, for 4 mm pipe it is 290 000 kg, for 5 mm it is 360 000 kg. Thus the radiator mass can vary between 220 000 and 360 000 kg depending on the degree of protection desired against micrometeorite damage and the amount of temperature gradient that the glass wall can tolerate. The imported mass is not particularly dependent on the radiator mass since there is a certain minimum mass required. In this case a 2000 kg facility can produce between 100000 and 150000 kg per year of pipe. The pipe can be produced in a two year time span—a reasonable construction time—and construction of the radiators can begin as soon as some pipe is available. The mining and beneficiation facility is not well defined. Preliminary mass estimates have been made for ilmenite beneficiation, where a plant handling 100000 tons of regolith was estimated to have a mass of 10.8 tons [1]. The majority of the regolith should be usable for matrix or fiber. Conservatively assuming only 10% usable product means processing at most 1500 tons per year. Using a scale factor of 0.62 (which is conservative for solids handling equipment) gives 704 kg. Two cases have been shown, a conservative one where the mining and beneficiation is assumed to be
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