Question:

I am about to intex pool solar water heater start designing a thermo siphon system for my house heating project and realise I know little or nothing about water flow.  Could anyone point me to a web site or books from which I might obtain information relating pipe diameter; pressure differences; temperature; flow rates; height differences; water density variation with temperature and so on. I will do a Google search but I know that several of you experts out there already have this sort of information and I am basically lazy.  intex pool solar water heater

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I am about to start designing a thermo siphon system for my house heating project and realise I know little or nothing about water flow.  Could anyone point me to a web site or books from which I might obtain information relating pipe diameter; pressure differences; temperature; flow rates; height differences; water density variation with temperature and so on. I will do a Google search but I know that several of you experts out there already have this sort of information and I am basically lazy. intex pool solar water heater

One of the best practical applications references I know of for fluid flow and the like is ‘Crane Technical Publication No. 410′  Available from intex pool solar water heater

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I am about to start designing a thermo siphon system for my house heating project and realise I know little or nothing about water flow.  Could anyone point me to a web site or books from which I might obtain information relating pipe diameter; pressure differences; temperature; flow rates; height differences; water density variation with temperature and so on.

Isn’t circulation a tiny fraction of the energy needed?            There are homes in the southern US that use natural drafts for cooling, but I don’t see where water circulation would be worth the effort unless it would reduce installation costs.     intex pool solar water heater

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I am about to start designing a thermo siphon system for my house heating project and realise I know little or nothing about water flow.  Could anyone point me to a web site or books from which I might obtain information relating pipe diameter; pressure differences; temperature; flow rates; height differences; water density variation with temperature and so on. I will do a Google search but I know that several of you experts out there already have this sort of information and I am basically lazy.

I’d also be interested in this information.  I went ahead and simply built a heat exchanger for my solar domestic hot water system.  It consists of 15′ of 1/2″ soft copper inside 15′ of 3/4″ soft copper (don’t ask what it takes to get the one inside the other…).  It’s coiled up around the storage tank, and thermo-siphoning takes care of getting heat into the tank when the pump circulates warm water from the panel through the outside pipe.  It does work, but I think it would work a lot better if the flow rate through the inner pipe were greater than what is produced by thermo-siphoning.  I hope to collect some numbers on this in the near future.intex pool solar water heater

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Daestrom,   Many thanks.  It looks great and I will buy it.  You deserve a commissionintex pool solar water heater    I’m sure you are right and I don’t expect that the thermo-siphon effect will be very significant for circulating hot water in the house but it just might be of some practical use in moving heated water from panel to tank or even in shifting heat into and out of some sort of Stirling engine.  I don’t know, which is why I want the information. Alan C

I am about to start designing a thermo siphon system for my house heating

intex pool solar water heater

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Joe,  I’m sure you are right and I don’t expect that the thermo-siphon effect will be very significant for circulating hot water in the house but it just might be of some practical use in moving heated water from panel to tank or even in shifting heat into and out of some sort of Stirling engine.  I don’t know, which is why I want the information.

I don’t doubt that it works well, it just seems the warm water tank would need to be above the solar panels, which seems to be a serious problem to me, if it is to be inside.           I know there are lots of solar water heaters installed, but I don’t know if any have two tanks, one for cooled water and one for hot water.    This seems to me to be something to consider, with the hot water tank inside and well insulated.   intex pool solar water heater        The overall design seems more important than the few watt  hours a small circulating pump would use, in many systems the flow rate needs to be very slow to get higher temperatures, but for a swimming pool the flow rate can be greater.  intex pool solar water heater

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I am about to start designing a thermo siphon system for my house heating project… Could anyone point me to a web site or books from which I might obtain information relating pipe diameter; pressure differences; temperature; flow rates; height differences; water density variation with temperature and so on.

Water weighs about 63.74-0.0158T lb/ft^3, with T in degrees F. The density difference caused by the average temperature difference between up and down pipes causes a pressure difference dP proportional to the height of the water column, which makes the water flow through the resistance of the pipe loop. With an H foot height difference and a dT (F) temperature difference, dP = 0.0158HdT lb/ft^2. Here’s a formula for laminar flow in a pipe with radius r and total length L in feet and pressure difference dP: Q = Pir^4dP/8MuL ft^3/s. Mu is the viscosity, about 9.8×10^-6 lb-s/ft^2 for 140 F water, from Table B-3 on page 352 of the $14.95 2nd edition of Schaum’s Outline on Heat Transfer by Donald Pitts and Leighton Sissom intex pool solar water heater

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Thanks (again) Nick,   It isn’t much pressure, of course, but it might be useful.  Still investigating.   Alan C

intex pool solar water heater Water weighs about 63.74-0.0158T lb/ft^3, with T in degrees F. The density difference caused by the average temperature difference between up and down pipes causes a pressure difference dP proportional to the height of the water column, which makes the water flow through the resistance of the pipe loop. With an H foot height difference and a dT (F) temperature difference, dP = 0.0158HdT lb/ft^2. Here’s a formula for laminar flow in a pipe with radius r and total length L in feet and pressure difference dP: Q = Pir^4dP/8MuL ft^3/s. Mu is the viscosity, about 9.8×10^-6 lb-s/ft^2 for 140 F water, from Table B-3 on page 352 of the $14.95 2nd edition of Schaum’s Outline on Heat Transfer by Donald Pitts and Leighton Sissom intex pool solar water heater

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