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Hi everyone. As I am not a thermodynamics guy, but an electronics guy, I beg for your asistance on this forum on my lack of heat transfer thinking. Planning to drill a ~100m deep well in my backyard, it is supposed to reach well beyond a stable ~20°C thermal layer; circulate water trough a long 2" U shaped polyethilene pipe to provide home cooling in ~30°C summers and help warming in ~0°C winters : A convection geothermal heat pump. What are the effects of the water velocity on amount-of-heat transfer ? From analogies on internal combustion engines, the faster the flow the greater the heat transfer - that is why racing engines have high flow coolant pumps- . On the other side, a slow flow speed allows the circulating water to reach the stable temperature and deliver all its potential temperature. What is more convenient ? A small mass flowing at a higher temperature differential or a larger mass flowing at a lesser temperature differential ? Seems to my ignorance that any will work equally, as the amount-of-heat would by Q=mass x (t2-t1) ; leaving good convection radiators, low losses, proper insulation of pipes, system efficiency to determine its effectivity. Is the ideal flow speed the one that will allow the flow to reach within a couple of degrees to ensure there will be heat transfer at all times? Thanks, Miguel

Hello YT2095 Would had been a nice try if some results were obtained. The aperture is narrow, yes. Solar stills with plain flat glass do produce a respectable amount of drinking water with the same temperature differential. No bottlenecks there. The intention is to find a distilling application recycling the zero cost PET disposable beverage bottles, for the third or fourth world to get some drinking water using many of these contraptions. The bottom sun exposed bottle is flat flack, the necks mating has a condensate collection ring and aquarium hose outlet. All that seems fine. Ideas to make the vapors rise to the upper bottle are needed. Maybe venting the top bottle as in distilling colums would help by producing a tiny agitation of the water surface ¿? Miguel

Thanks. I should had said room temperature, about 25°C for the upside-down cool bottle. Miguel

Hello everyone. Simple condensation does not happen : A bottle ¾ filled with water kept hot (~60°C). On top of it, another bottle upside down kept at ambient temperature, coupled neck to neck with adhesive tape, forming a shape sort of an hourglass. No condensation happens in the internal walls of the upside down top cool bottle, even after hours. Why ? What is missing ? How can condensation be achieved ? VERY easy to try and confirm by yourself ! Miguel