by hillzabilly » Wed Mar 14, 2018 3:08 pm
Venturi effect ifn the dowmcomer is in the riser,plus its a higher pressure and temp in the riser, the returning liquid from the plate above is a higher ABV with a lower boiling point moveing to a higher temp area esspecially on the bottom plate were the boiler could be close to 95-100'c and the returning liquid may boil up stopping the flow and flooding ya plates,anyhooo just my thoughts and observations ,as with my thumper I fitted a sight glass over the downcomer as Mac advised so as you can prime the downcomer befor a run and keep an eye on it during a run,and with the sight glass in the boiler I could observe the downcomer cap during a run ,at first I ran the down comer up the riser but it failed badly ,and after several changes validated with test runs ended up with what I have now,I did observe boiling up in the downcomer were the downcomer met and went thru the bubble cap and slowly increased the pipe size until it worked very well ,4inch single cap 1 1/2inch upper downcomer and 1inch lower downcomer with a drop of about 180mm and a 2inch cap that is 70mm long,running a bath depth of 100mm,I think the deeper plate bath depth the harder it is ta get it to work,wich increases the pressure slightly makeing it harder to get your downcomer working well .cheers hillzabilly ;-)
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