tilting the experiment from the vertical is shown in Figure 18(a). Also 

 shown are the effects on these critical metal tenparatures of shrouding 

 the modules with a vertical steel chimney in what might be expected to 

 be the worst case; when the experiment is tilted 60 degrees froa the 

 vertical. There was some increase in temperature at all three points of 

 neasureraent , but no great change which would predict dif f iculty--the 

 presence of the shroud merely impeded the vertical flow of water in 

 this partially prone position. The effects are, in fact, similar to 

 placing the shroud on the unit when in the vertical position, Figure 18(b). 

 Here, there was some indication of reduced flow to the lower parts of 

 the modules, but essentially no effect at the tcp, T1 . The small decrease 

 in temperature of T1 with the shroud added can be almost exactly accounted 

 for by slightly lower water temperatures. 



The efficacy of a shroud is almost universally assumed, because 

 of the apparent 'chimney' effect that might be gained. However, a convec- 

 tor has one major difference from a chimney. In a typical chinney used 

 to produce draft in a furnace, all of the heat is introduced below the 

 chimney, and the draft produced arises from the difference in density 

 between the heated stack gases and the surrounding cool air. There is, 

 of course, a stack effect with the shrouded convector. However, there 

 is what appears to be a more important second effect common to plumes. 

 Without the shroud, cold fluid (water in this case) can be continually 

 entrained- -the higher metal surfaces do not see the warmed water, hut 

 rather cold water drawn in by the vertical convection currei.e. 



Our consideration of the use of a shroud for this application arose 

 not from a desire to enhance the flow and produce marginally lover metal 

 temperatures, Dut to provide protection for the convection modules from 

 cables, etc, as will be necessary in the ocean. Its usefulness in this 

 function may well justify the small loss in cooling effect caused by the 

 inhibition of inflowing cold water. A schematic of a shroud as it might 

 be utilized on a large RTG is shown in Figure 19. 



In assessing the foregoing, it should be remembered that with the 

 cold water typical of the deep ocean (36 to 40°F) , all of the csetal 

 temperatures would be reduced in proportion. Critical metal temperatures 

 of the order to 70°F or lower would be expected. 



A discussion of metal selection based on heat transfer, fouling, 

 and corrosion considerations is contained in Appendix A. 



The results of a 30-day immersion in Port Haeneme Harboi at nominal 

 full power are discussed in Appendix B. 



It should be noted here that in neither the Laboratory tank tests 

 nor those in the harbor was bare copper exposed, as would be expected 

 with high velocities. The use of copper is satisfactory on that basis. 



