thermo siphon

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Thermosiphon

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Solar heating system featuring a thermosiphon

Warm water supply system with thermosiphon (schematically):

1: water tap

2: isolated container

3: warm water inlet

4: solar thermal collector

5: fresh water supply

Thermosiphon (alt. thermosyphon) refers to a method of passive heat exchange

based on natural convectionwhich circulates liquid in a vertical closed-loop circuit

without requiring a conventional pump. Its intended purpose is to simplify thepumping of liquid and/or heat transfer, by avoiding the cost and complexity of a

conventional liquid pump.

Contents

[hide]

1 Simple thermosiphon

2 Phase-change (heat pipe) thermosiphon

o 2.1 Heat Pipe

o

2.2 "heat pipe thermosiphon"o 2.3 A thermosiphon is not a heat pipe

3 Solar energy

4 Computing

o 4.1 Uses

o 4.2 Drawbacks

5 Ground cooling

6 See also

7 References

[edit] Simple thermosiphon
http://en.wikipedia.org/wiki/Thermosiphon#column-one%23column-onehttp://en.wikipedia.org/wiki/Thermosiphon#column-one%23column-onehttp://en.wikipedia.org/wiki/Thermosiphon#searchInput%23searchInputhttp://en.wikipedia.org/wiki/Heat_exchangehttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Convectionhttp://toggletoc%28%29/http://en.wikipedia.org/wiki/Thermosiphon#Simple_thermosiphon%23Simple_thermosiphonhttp://en.wikipedia.org/wiki/Thermosiphon#Phase-change_.28heat_pipe.29_thermosiphon%23Phase-change_.28heat_pipe.29_thermosiphonhttp://en.wikipedia.org/wiki/Thermosiphon#Heat_Pipe%23Heat_Pipehttp://en.wikipedia.org/wiki/Thermosiphon#.22heat_pipe_thermosiphon.22%23.22heat_pipe_thermosiphon.22http://en.wikipedia.org/wiki/Thermosiphon#A_thermosiphon_is_not_a_heat_pipe%23A_thermosiphon_is_not_a_heat_pipehttp://en.wikipedia.org/wiki/Thermosiphon#Solar_energy%23Solar_energyhttp://en.wikipedia.org/wiki/Thermosiphon#Computing%23Computinghttp://en.wikipedia.org/wiki/Thermosiphon#Uses%23Useshttp://en.wikipedia.org/wiki/Thermosiphon#Drawbacks%23Drawbackshttp://en.wikipedia.org/wiki/Thermosiphon#Ground_cooling%23Ground_coolinghttp://en.wikipedia.org/wiki/Thermosiphon#See_also%23See_alsohttp://en.wikipedia.org/wiki/Thermosiphon#References%23Referenceshttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=1http://en.wikipedia.org/wiki/File:Solar_heater_dsc00632.jpghttp://en.wikipedia.org/wiki/Thermosiphon#column-one%23column-onehttp://en.wikipedia.org/wiki/Thermosiphon#searchInput%23searchInputhttp://en.wikipedia.org/wiki/Heat_exchangehttp://en.wikipedia.org/wiki/Convectionhttp://toggletoc%28%29/http://en.wikipedia.org/wiki/Thermosiphon#Simple_thermosiphon%23Simple_thermosiphonhttp://en.wikipedia.org/wiki/Thermosiphon#Phase-change_.28heat_pipe.29_thermosiphon%23Phase-change_.28heat_pipe.29_thermosiphonhttp://en.wikipedia.org/wiki/Thermosiphon#Heat_Pipe%23Heat_Pipehttp://en.wikipedia.org/wiki/Thermosiphon#.22heat_pipe_thermosiphon.22%23.22heat_pipe_thermosiphon.22http://en.wikipedia.org/wiki/Thermosiphon#A_thermosiphon_is_not_a_heat_pipe%23A_thermosiphon_is_not_a_heat_pipehttp://en.wikipedia.org/wiki/Thermosiphon#Solar_energy%23Solar_energyhttp://en.wikipedia.org/wiki/Thermosiphon#Computing%23Computinghttp://en.wikipedia.org/wiki/Thermosiphon#Uses%23Useshttp://en.wikipedia.org/wiki/Thermosiphon#Drawbacks%23Drawbackshttp://en.wikipedia.org/wiki/Thermosiphon#Ground_cooling%23Ground_coolinghttp://en.wikipedia.org/wiki/Thermosiphon#See_also%23See_alsohttp://en.wikipedia.org/wiki/Thermosiphon#References%23Referenceshttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=1


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Convective movement of the liquid starts when liquid in the loop is heated, causing it

to expand and become less dense, and thus morebuoyant than the cooler water in the

bottom of the loop. Convection moves heated liquid upwards in the system as it is

simultaneously replaced by cooler liquid returning by gravity. In many cases the

liquid flows easily because the thermosiphon is designed to have very little hydraulic

resistance.

[edit] Phase-change (heat pipe) thermosiphon

[edit] Heat Pipe

Main article: heat pipe

A heat pipecontains a phase change fluid, which transfers heat by evaporation and

condensation. A heat pipe does not use a siphonnor does it rely onconvection. This

makes a heat pipe distinct from a thermosiphon. The term "phase changethermosiphon" is a misnomer and should be avoided. When phase change occurs in a

thermosiphon, it means that the system either does not have enough fluid, or it is not

big enough to transfer all of the heat that is being applied to it using convection alone.

To improve the performance in such a situation, either more fluid should be added

(possibly in a larger thermosiphon), or all other fluids (including air) should be

pumped out of the loop, in order to create a trueheat pipe. In the case of the heat pipe,

less fluid is needed.

[edit] "heat pipe thermosiphon"

(Note: This term should be used with care, since the terms "thermosiphon" and "heatpipe" refer to very different things.)

In cases when the thermosiphon fluid incurs excessive resistance to flow, or excessive

heat is applied, the liquid may be heated beyond its boiling point (assuming it is a

liquid that boils), thus causing aphase change as the liquid evaporates to a gas(vapor)

(such as steam). Since the gas is much less dense than the hot liquid, and thus much

more buoyant, the convective pressure is increased considerably. This is may be

referred to as a "heat pipethermosiphon". In addition to thermosiphon convection,

heat transfer is somewhat increased by thephase change of a fluid inside aclosed

system. It operates on the principles ofbuoyancyto move the fluid through thesystem.

In some situations the flow of liquid may be reduced further, or stopped, perhaps

because the loop is not entirely full of liquid. In this case, then the system no longer

operates on convection principles, so it is no longer a simple "thermosiphon". Heat

can still be transferred in this system by theevaporationandcondensation of vapor;

however, the system is properly classified as aheat pipe. If the system also contains

other fluids, such as air, then the heat flux density will be less than in a real heat pipe,

which only contains a single fluid.

A thermosiphon reboileris also called a calandria.
http://en.wikipedia.org/wiki/Buoyancyhttp://en.wikipedia.org/wiki/Hydraulichttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=2http://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=3http://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Siphonhttp://en.wikipedia.org/wiki/Siphonhttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=4http://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Phase_changehttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Phase_(matter)http://en.wikipedia.org/wiki/Closed_systemhttp://en.wikipedia.org/wiki/Closed_systemhttp://en.wikipedia.org/wiki/Closed_systemhttp://en.wikipedia.org/wiki/Buoyancyhttp://en.wikipedia.org/wiki/Buoyancyhttp://en.wikipedia.org/wiki/Evaporationhttp://en.wikipedia.org/wiki/Evaporationhttp://en.wikipedia.org/wiki/Evaporationhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Reboilerhttp://en.wikipedia.org/wiki/Calandriahttp://en.wikipedia.org/wiki/Calandriahttp://en.wikipedia.org/wiki/Buoyancyhttp://en.wikipedia.org/wiki/Hydraulichttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=2http://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=3http://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Siphonhttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=4http://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Phase_changehttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Phase_(matter)http://en.wikipedia.org/wiki/Closed_systemhttp://en.wikipedia.org/wiki/Closed_systemhttp://en.wikipedia.org/wiki/Buoyancyhttp://en.wikipedia.org/wiki/Evaporationhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Reboilerhttp://en.wikipedia.org/wiki/Calandria


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[edit] A thermosiphon is not a heat pipe

The thermosiphon has been sometimes incorrectly described as a 'gravity return heat

pipe'[1]. A wick is usually a necessary feature of a heat pipe to allow the return of

condensateto the evaporatorvia capillary action, whereas this function is not needed

in a thermosiphon as gravity allows the movement of the liquids[2]. The wick allowsheat pipes to transfer heat in the absence of gravity, which is useful for space

applications. A thermosiphon is, in a sense, "simpler" than a heat pipe [3]. (Single-

phase) thermosiphons can only transfer heat "upward", or away from the acceleration

vector. Thus, orientation is much more important for thermosiphons than for

heatpipes.

[edit] Solar energy

Thermosiphons are used in some liquid-based solar heating systems to heat a liquid

such as water. The water is heatedpassively by solar energy and relies on heat energybeing transferred from the sun to a solar collector. The heat from the collector can be

transferred to water in two ways: directly where water circulates through the collector,

orindirectly where an anti-freeze solution carries the heat from the collector and

transfers it to water in the tank via aheat exchanger. Convection allows for the

movement of the heated liquid out of thesolar collectorto be replaced by colder

liquid which is in turn heated. Due to this principle, it is necessary for the water to be

stored in a tank above the collector.

[edit] Computing

Thermosiphons are used in computing to describe a system forwatercooling the

internal computer components, most commonly referring to theprocessor. While any

suitable liquid can be used, water is the easiest liquid to use in thermosiphon systems.

Unlike traditional watercooling systems, thermosiphon systems do not rely on a water

pump (or a pump for other liquids) but rely on convection for the movement of heated

water (which may become vapour) from the components upwards to a heat exchanger.

There the water is cooled and is ready to be recirculated. The most commonly used

heat exchanger is aradiatorwhere air is blown actively through a fan system to

condense the vapour to a liquid. The liquid is recirculated through the system, thus

repeating the process. No pump is required - the vaporization and condensation cycle

is self sustaining.

[edit] Uses

Modern processors get relatively hot. Even with a common heat sink and fan cooling

the processor, operating temperatures may still reach up to 70 C (160 F). A

thermosiphon can handle heat output at a much wider temperature range than any heat

sink and fan, and can maintain the processor 1020 C cooler. In some cases a

thermosiphon may also be less bulky than a normal heat sink and fan.

[edit] Drawbacks
http://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=5http://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://www.btfsolar.com/specifications.htmhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Evaporatorhttp://en.wikipedia.org/wiki/Capillary_actionhttp://cipco.apogee.net/ces/library/twhtherm.asphttp://cipco.apogee.net/ces/library/twhtherm.asphttp://www.cheresources.com/htpipes.shtmlhttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=6http://en.wikipedia.org/wiki/Solar_heatinghttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Passivehttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Heat_energyhttp://en.wikipedia.org/wiki/Solar_collectorhttp://en.wikipedia.org/wiki/Solar_collectorhttp://en.wikipedia.org/wiki/Anti-freezehttp://en.wikipedia.org/wiki/Heat_exchangerhttp://en.wikipedia.org/wiki/Heat_exchangerhttp://en.wikipedia.org/wiki/Solar_collectorhttp://en.wikipedia.org/wiki/Solar_collectorhttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=7http://en.wikipedia.org/wiki/Watercoolinghttp://en.wikipedia.org/wiki/CPUhttp://en.wikipedia.org/wiki/CPUhttp://en.wikipedia.org/wiki/Watercoolinghttp://en.wikipedia.org/wiki/Radiatorhttp://en.wikipedia.org/wiki/Radiatorhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=8http://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=9http://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=5http://en.wikipedia.org/wiki/Heat_pipehttp://en.wikipedia.org/wiki/Heat_pipehttp://www.btfsolar.com/specifications.htmhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Evaporatorhttp://en.wikipedia.org/wiki/Capillary_actionhttp://cipco.apogee.net/ces/library/twhtherm.asphttp://www.cheresources.com/htpipes.shtmlhttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=6http://en.wikipedia.org/wiki/Solar_heatinghttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Passivehttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Heat_energyhttp://en.wikipedia.org/wiki/Solar_collectorhttp://en.wikipedia.org/wiki/Anti-freezehttp://en.wikipedia.org/wiki/Heat_exchangerhttp://en.wikipedia.org/wiki/Solar_collectorhttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=7http://en.wikipedia.org/wiki/Watercoolinghttp://en.wikipedia.org/wiki/CPUhttp://en.wikipedia.org/wiki/Watercoolinghttp://en.wikipedia.org/wiki/Radiatorhttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=8http://en.wikipedia.org/w/index.php?title=Thermosiphon&action=edit&section=9


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Thermosiphons must be mounted such that vapor rises up and liquid flows down to

the boiler with no bends in the tubing for liquid to pool. Also, the thermosiphons fan

that cools the gas needs cool air to operate.

Ground cooling

Heat pipes are used at locations in higher latitudes like northern Alaska and Canada to

prevent ice-richpermafrost from melting below buildings and other infrastructure

such as schools, air hangars, community water tanks, and even some stretches of

highway. Heat pipes are also a common feature along the length of the Trans-Alaska

Pipeline System. In these applications the solution in the pipes is oftencarbon dioxide

orammonia. At the bottom of the heat pipe, heat from the ground warms the liquid

and converts it to a vapor. Cooling from the heat sink fins above ground releases this

heat to the atmosphere and causes the vapor to condense on the outer pipe wall, which

then drains back into the liquid pool at the bottom of the heat pump.

Thermosyphon Solar WaterHeating

Find out how a Thermosyphon SolarWater Heating System works

heating| solar |water

Printer Friendly Version

A Thermosyphon Solar Water Heating System takes advantage of the factthat hot water rises and cool water sinks. As water is heated it expands and so, asgravity pulls down the relatively heavier cool water molecules, the warmermolecules rise up.

The diagram below shows how this works in a real world thermosysphon solarwater heating system. Such a system offers the advantage that no pump orcontroller is required to run everything and so it is very simple and less liable to

failure.
http://en.wikipedia.org/wiki/Permafrosthttp://en.wikipedia.org/wiki/Trans-Alaska_Pipeline_Systemhttp://en.wikipedia.org/wiki/Trans-Alaska_Pipeline_Systemhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Ammoniahttp://www.reuk.co.uk/heating.htmhttp://www.reuk.co.uk/heating.htmhttp://www.reuk.co.uk/solar.htmhttp://www.reuk.co.uk/water.htmhttp://www.reuk.co.uk/water.htmhttp://www.reuk.co.uk/print.php?article=Thermosyphon-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Introduction-to-Solar-Water-Heating.htmhttp://en.wikipedia.org/wiki/Permafrosthttp://en.wikipedia.org/wiki/Trans-Alaska_Pipeline_Systemhttp://en.wikipedia.org/wiki/Trans-Alaska_Pipeline_Systemhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Ammoniahttp://www.reuk.co.uk/heating.htmhttp://www.reuk.co.uk/solar.htmhttp://www.reuk.co.uk/water.htmhttp://www.reuk.co.uk/print.php?article=Thermosyphon-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Introduction-to-Solar-Water-Heating.htm


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During the day water in the solar collector (flat panel or evacuated tube) isheated by the sun. As the water heats up, it rises pushing up into the insulatedtank. Cooler water at the bottom of the tank is then pushed down to re-enter thebottom of the solar collector where it is heated further. This cycle continuesthroughout the day with the water stored in the tank getting hotter and hotter.

Pictured above is a shematic of a more advanced type ofthermosyphon solarwater heater which couples a standard electric immersion element heated hotwater tank together with the solar heating system and its tank. Therefore, whenthere is not enough sunshine to meet your hot water requirements, the electricheater will turn on and heat up the water (in the backup tank) further.
http://www.reuk.co.uk/Evacuated-Tube-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Evacuated-Tube-Solar-Water-Heating.htm


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image from Home Power magazine.

To keep this a purely renewable energy water heating system, a wind turbinecan be used as described in our article: Wind Turbine Water Heating using a low

voltage immersion heater element. When it is cold and windy the water will beheated by wind power, and when it is still and sunny the water will be heated by

solar power. (A second, mains powered, heating element could be added toguarantee unlimited hot water in all seasons and weather conditions(.

Simple Solar Water Heating

Make a simple solar water heater witheasy to find materials

heating| solar |water


Solar Water Heating is a fantastic way to obtain free hot water and to savefossil fuels. The following simple design for a solar water heater requires no pumpor difficult to find materials, and it can be built in just a few hours by anyone with

basic DIY skills.
http://www.homepower.com/basics/hotwater/http://www.homepower.com/basics/hotwater/http://www.reuk.co.uk/wind.htmhttp://www.reuk.co.uk/Wind-Turbine-Water-Heating.htmhttp://www.reuk.co.uk/200W-12V-Immersion-Heater.htmhttp://www.reuk.co.uk/heating.htmhttp://www.reuk.co.uk/heating.htmhttp://www.reuk.co.uk/solar.htmhttp://www.reuk.co.uk/water.htmhttp://www.reuk.co.uk/water.htmhttp://www.reuk.co.uk/print.php?article=Simple-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Introduction-to-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Pumps-for-Solar-Water-Heating.htmhttp://www.homepower.com/basics/hotwater/http://www.reuk.co.uk/wind.htmhttp://www.reuk.co.uk/wind.htmhttp://www.reuk.co.uk/Wind-Turbine-Water-Heating.htmhttp://www.reuk.co.uk/200W-12V-Immersion-Heater.htmhttp://www.reuk.co.uk/heating.htmhttp://www.reuk.co.uk/solar.htmhttp://www.reuk.co.uk/water.htmhttp://www.reuk.co.uk/print.php?article=Simple-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Introduction-to-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Pumps-for-Solar-Water-Heating.htm


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Build a Simple Solar Water Heater

All you need is some black pond liner, plywood, a plexiglass sheet, a big bucket,and some hoses and clamps. In total it will cost around 30 assuming that youhave to buy all of the materials you use (rather than recycling junk). For yourefforts you will have a solar water heater which will heat up a 5 gallon bucket ofwater to well over 40 degrees celcius (the temperature of a hot bath).

The solar panel is made as pictured toward the top of this article. It is backedwith black pond liner which is both waterproof and an excellent solar absorber.

The panel is sealed with plexiglass and so it is water tight. A tube connects thebottom of the bucket to the bottom of the panel, and another tube connects thetop of the panel to the top of the bucket.

As the sun shines on the panel water heats up and rises up the path until itreaches the top and passes over into the bucket thanks to thermosyphoning(click here for more details).

As the warm water leaves the panel, more water is sucked back into the bottomof the panel. This is colder water from the bucket, and so the cycle continues ad

infinitum: hot water passing from the panel into the bucket, and cooler waterbeing passed from the bucket into the panel to be heated further.

Ideally the bucket should be well insulated and kept sheltered from the wind sothat heat is not wasted.

More Information
http://www.reuk.co.uk/recycling.htmhttp://www.reuk.co.uk/Thermosyphon-Solar-Water-Heating.htmhttp://www.reuk.co.uk/recycling.htmhttp://www.reuk.co.uk/Thermosyphon-Solar-Water-Heating.htm


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Details of a more advanced DIY Solar Water Heating Prototypeare availablehere, or click here to view more details plans for the construction of the basic

Solar Water Heater described in this article.

DIY Solar Water HeatingPrototype

Follow the construction of a successfulDIY solar water heating prototype

solar | heating |water


Solar water heating is probably the easiest way to use less energy and savemoney. Payback time - i.e. the time taken for the capital cost of the completesystem to be offset by reduced energy bills - can be under a year for DIY systemsmade from salvaged parts, and as little as 5 years even for the latest commercialevacuated tube solar water heaters.

In previous articles we have looked at DIY concentrated solar water heating,and a very basic solar water heaterwhich can be put together by anyone in justa couple of hours using easy to find parts.

In this article we will expand on our article DIY Solar Water Heating bydescribing the steps involved in putting together a flat plate collector solarwater heating system.

DIY Flat Plate Collector Solar WaterHeater

This system was put together by Stephen and John in Wiltshire as a workingprototype to test the concept before building a system which will eventually heatsufficient water for a whole household. The prototype is pump driven using a 12Vcar windscreen washer pump (the final system will probably be a pumpless

thermosyphon system to keep it simple and to reduce costs and latermaintenance).
http://www.reuk.co.uk/DIY-Solar-Water-Heating-Prototype.htmhttp://www.reuk.co.uk/DIY-Solar-Water-Heating-Prototype.htmhttp://www.cleanpower.thesietch.org/projects/solarthermalpanel/index.htmhttp://www.reuk.co.uk/solar.htmhttp://www.reuk.co.uk/heating.htmhttp://www.reuk.co.uk/water.htmhttp://www.reuk.co.uk/water.htmhttp://www.reuk.co.uk/print.php?article=DIY-Solar-Water-Heating-Prototype.htmhttp://www.reuk.co.uk/Introduction-to-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Evacuated-Tube-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Concentrated-Solar-Power.htmhttp://www.reuk.co.uk/Concentrated-Solar-Power.htmhttp://www.reuk.co.uk/Concentrated-Solar-Power.htmhttp://www.reuk.co.uk/Simple-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Simple-Solar-Water-Heating.htmhttp://www.reuk.co.uk/DIY-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Thermosyphon-Solar-Water-Heating.htmhttp://www.reuk.co.uk/DIY-Solar-Water-Heating-Prototype.htmhttp://www.cleanpower.thesietch.org/projects/solarthermalpanel/index.htmhttp://www.reuk.co.uk/solar.htmhttp://www.reuk.co.uk/heating.htmhttp://www.reuk.co.uk/water.htmhttp://www.reuk.co.uk/print.php?article=DIY-Solar-Water-Heating-Prototype.htmhttp://www.reuk.co.uk/Introduction-to-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Evacuated-Tube-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Concentrated-Solar-Power.htmhttp://www.reuk.co.uk/Simple-Solar-Water-Heating.htmhttp://www.reuk.co.uk/DIY-Solar-Water-Heating.htmhttp://www.reuk.co.uk/Thermosyphon-Solar-Water-Heating.htm


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Pictured above is the pipework for the flat plate collector. A mixture of 22mmand 15mm diameter copper pipes were fitted in a wooden frame and mountedonto heavy duty aluminium sheeting. The top and bottom pipes of the array were

22mm diameter, and the vertical pipes were 15mm diameter connecting to the22mm pipes with reducing Tee joints (22-15-22). Heat sink compound was usedbetween the copper and aluminimum to help heat conduction.NEW Click here to read our new introductory guide to Soldering Copper Pipe.

To prevent heat from escaping from the back of the collector, it was heavilyinsulated in layers. The first layer of insulation was covered with foil and then heldin place with rip stop nylon (1) - the internal piping (2) was insulated seperately.Four polythene bags of fibre-glass insulation (3) were then added and taped inplace before the foil covered backboard (4) was fitted.

(1)

(2) (3)(4)

The back board was made from industry cast-off 3 ply 6mm hardwood. The rest ofthe frame was made from timber reclaimed from an discarded staircase - somepine and West Indian mahogany.

Hammerite was then painted onto the wooden exterior of the solar collector toprotect it from the weather, and the heat sinkwas painted with heat resistantblack paint (Very High Temperature Engine Enamel Paintfrom Halfords) tomaximise heat absorption.
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A flat sheet of dimpled toughened glass (33 fromRoman Glass) was fixed onthe front of the panel with silicon sealant (A) and aluminium angle strips thenadded (B) and sealed with silicon sealant to keep the rain out and the hot air in.

(A) (B)

The finished flat plate solar collector was then ready to be tested in thesunshine.

The Heat Exchanger
http://www.romanglass.co.uk/http://www.romanglass.co.uk/http://www.romanglass.co.uk/


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This prototype solar water heater is a closed system. Water is pumped aroundthrough the solar collector and then to the heat exchanger. As the solarheated water flows through the heat exchanger (which sits in an insulated tank),the water in the tank gets hotter, and the water in the heat exchanger getscolder. The water in the heat exchanger then continues its journey back throughthe pump and onto the solar collector again, so in time the water in the bucket

gets hotter and hotter.

The heat exchanger (pictured above) was made up of 15 metres of10mmcopper pipe coiled around. That gives the heat exchanger a total surface area ofalmost 0.5 square metres of copper transferring heat from the solar heated waterin the pipe to the bucket of water to be heated.

A set ofpipe bending springs (lubricated with light silicon grease) was used toenable the pipe to be bent around (without it folding). The pipe is simply insertedinto the spring and bent as required. The 10mm pipe bending spring picturedabove is available for just 2.25 plus postage on eBay (click here to search eBayfor pipe bending springs - 10mm, 15mm, and 22mm springs are all available)

The image above shows the pipework entering and leaving the top of the 15 litrebucket of water to be heated. A car windscreen washer pump was used tocirculate water around the prototype solar heating system. A PV solar poweredfan is shown stuck to the pump to prevent it from overheating.

To slow the pump down, the input voltage was reduced to 8 Volts (rather than the

rated 12V), and it was operated in manual short bursts to give the water in thesolar panel the chance to heat up. Using the pump in this manner it never gothotter than the water it was pumping. Ideally a thermostat would have been
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used to automatically trigger the pump when the water in the solar panel reacheda chosen temperature.

A digital indoor/outdoor thermometer was used to display the ambient airtemperature (27.8 degrees C in May in the UK) and the temperature of the 15litres of water in the bucket (36.9 degrees C in this image). The water in the

bucket heated by the 0.8 square metre solar flat plate collector eventuallyreached 41 degrees (hot bath temperature) in just over one hour starting fromjust 16 degrees C and despite the bucket not being insulated (though sitting on apiece of polystyrene).

Bleed Valve

A bleed valve is an essential component of any closed system. Bleed valvesare found on domestic radiators amongst other things and enable trapped air tobe removed from the system. When filling the system the first time the bleedvalve needs to be left open until water starts to come out. At this point you knowthat the system is full of water with no trapped air, and so the bleed valve can beclosed tight.

Every now and then - how frequently depends on the integrity of the system - it is

necessary to bleed the system to release any air bubbles. At the same time thewater (or anti-freeze) in the system can be topped up.

Note in the images above how a small glassjam jar was used in this prototypesystem to protect the bleed valve from the weather while still enabling easyaccess (by unscrewing the jar from its lid).

Filling the Closed System

In order to fill the closed circulation system before first use liquid was pouredthrough a funnel (held above the highest point of the system), down throughtransparent plastic pipe (so the flow and level of fluid taken up by the systemcould be seen), and through a standard radiator tap into the system just beforethe heat exchanger. When full and bled for air, and with the pump running, the


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radiator tap was closed to seal the circulation system.

The prototype system was filled with tap water dyed with blue food colouring (soleaks could be identified), however anti-freeze will be used in the final system.

Time and CostAltogether John and Stephen have so far spent 24 working hours together as ateam on this project. The total cost of items purchased (excluding the PV solarsystem used to power the fan and pump) is 240. Of that, 100 was spent onpipe and fittings, 33 on glass, and 25 on paint and primer. While there weresome items obtained free of charge or recycled(such as the bucket, insulation,aluminimum sheet and pump) it would certainly have been possible to puttogether a similar solar water heating system for under 100 building thesystem entirely around scrounged junk.

Future Developments

Stephen and John plan to put together a second prototype solar collector, thistime using microbore copper pipe (pictured above) in a snake configuration to

compare how effective it is in comparison with the existing prototype. It will

certainly be cheaper and easier to assemble since there will be far less fittings(and associated soldering) required. At current (July 2008) copper prices, a 25

metre length of 10mm microbore can be purchased for under 30 in the UK. It isalso commonly available in 6mm, 8mm and 12mm diameters.

Evacuated Tube Solar WaterHeating

Learn about the most efficient way touse the sun to heat water

heating| solar


Solar Water Heatinghas been used for hundreds if not thousands of years to heatwater. With advances in technology solar water heating systems have becomemore and more efficient, with Evacuated Tube Solar Water Heatings offeringefficiencies of well over 90%. That means that more than 90% of the sun's energylanding on a surface is converted into heat which can be used to heat water. This

is also one of the cheapest renewables, with costs starting from pennies perWatt required comparing to pounds per Watt for PV Solar and Wind Turbine powergeneration.
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Vacuum or Evacuated Tubes are made from glass - typically ultra-strong andheat resistant Pyrex with a double wall construction. The glass on the inner tubeis coated on its outer surface with an absorbant coating, and on its inner surfacewith a reflective coating. Inside each tube all air is removed making a vacuum anda copper heat pipe is located through the centre of the tubes. Most of the infra-red radiation (i.e heat) from the sun is absorbed by this sealed heat pipe whichcontains an anti-freeze type liquid.

As heat rises, hot vapours from the antifreeze rise up to the top of the heat pipewhere its copper tip connects with a header pipe through which more antifreezeflows. This hot antifreeze is then pumped through pipes inside the hot water tank

with the end result that the water gets hotter and the antifreeze cooler. Theantifreeze then continues its journey around the system and back out to the solarwater heater to be reheated.

The copper at the tip of the heat tube can reach well over 200 degrees easilyheating water to 90 degrees celcius on hot days and to 60 degrees celcius even inthe winter. This simple system is completely sealed and needs minimalmaintenance over its 20+ years life.


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The advantage of using evacuated tubes is that they will work even during thecoldest winter months unlike old style Flat Plate Solar Collectors. The vacuumprevents the heat tube from being cooled much by the ambient temperaturewhich can be well below freezing, and so winter sun can easily heat water to 50+degrees even in the depths of the coldest season. Even if it is very cloudy and

very cold, enough sunlight gets through to keep the tubes well above freezing andso they will be still be pre-heating the water which can then be heated further bya standard immersion heater or gas burner reducing the costs of heating thewater.

The fitting of a Solar Water Heating system using evacuated tubes can becarried out by any able DIY enthusiast with basic plumbing skills. The solar tubesare usually put on modules of 10 or 20 tubes which are then connected viainsulated copper piping to a suitable hot water cylinder. Pictured above is aschematic showing the installation of a modular evacuated tube solar waterheating system.

Buy an Evacuated Tube Water Heating

System

Until recently it was difficult for the

amateur to get their hands on an

economical array of evacuated tubes

in order to install a DIY solar water

heating system. That has now all


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changed thanks to eBay. Click here to

search eBay for Evacuated Tube now to view

a list of what's available for saletoday.

The "Thermosyphonic Family Unit" is the most compact, simple,economic, efficient and maintenance free solar unit. No need for a pump,no control unit and no auxiliary components.

The basic components are:

Solar CollectorHighly-efficient selective coated absorption plate, galvanized steel or aluminum

case, tempered solar glass.Net area: 1.5 - 2.6 m2

Solar Storage Tank3mm steel, enamel coated interior, polyester coated exterior, polyurethaneinsulation, electric back-up, regular or with heat exchanger (double jacket).Capacity 80 to 300 liters.

Connecting Kit:Including fittings, no-return and safety valves and U.V. protected pipes.

Stand:

Polyester coated, galvanized steel.An especially elegant look with our low-silhouette configuration for flat roofs. Onpitched roofs the collector lays flat on the tiles and the tank is on or under theroof.

Thermosiphonic System Configuration

There are two kinds of thermosyphonic systems which may varyaccording to the climate:

1. Open loop system for non-freezing warm climates:Cold water runs to the tank, from there to the lower part of the

collector, warms up and ascends in the collector and is stored in thetank ready for use. Simplicity and economy are this system's

advantages.
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2. Closed loop

systems for

continental

climates:

Based on largesurface heat-

exchanger. A closed

circuit where hot

water from the

collector passes to

the outer jacket of

the tank (external

heat exchanger) and

after heat-exchanging returns to the collector to be heated again.

Simultaneously, cold water from the city water connection runs intothe tank, warms up by the heat exchanging process and from thereto the user.

The main advantages of the system lay in:

a. the option to add an anti-freeze solution.

b. no build-up of scaling in the collector.

ALL THERMOSYPHONIC SYSTEMS ARE SIMPLE, COMPACT AND EFFICIENT.

Performance study of thermosyphonic circulation solar water heaters

using packed bed collectorsC. B. Mishra, A. K. BhatDepartment of Mechanical Engineering, Birla Institute of Technology, Mesra, Ranchi, Bihar, India

KEYWORDSSolar water heater Packed bed collectors

ABSTRACTIn the present investigation the performance behaviour of thermosyphonic circulation solar water heatersusing packed bed collectors has been analysed. Iron chips, gravels and stones have been used aspacking materials. Average tank water temperature, collector as well as system efficiency and mony pay-back for these packed bed solar water heaters are compared with those for solar water heater using aplane collector. Experimental results reveal that the performance of solar water heater improvesappreciably by packing its collector with packing material. Among the packed-bed solar water heaters

tested the iron chips packed-bed solar water heater gives the overall best performance.

Experimental Study of a Novel

Thermosyphonic Mhd Electric

Generator

Document Number: 1999-01-2509

Date Published: August 1999


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Author(s):

F. B. Chaaban - American University of Beirut

N. Ghaddar - American University of Beirut

A. Nahle - University of Sharjah

Abstract:A direct energy conversion from thermal to electrical is experimentally verified in

using a thermosyphonic hydromagnetic closed loop flow as an electrical generator.

Magnetohydrodynamic (MHD) generators are typically based on pressure-driven

electrically conducting liquid flow in a channel passing between poles of a magnet.

The generator in this work differs in using thermosyphon-driven motion in a bottom-

heated closed loop, thus eliminating the use of a pump while permitting operation at

high temperatures. A workable model of the generator is designed and built using salt

and water solution as the working fluid. The design calculations of the MHD

generator and the range of parameters involved are based on the analytical results

obtained from previous work, which allowed prediction of the optimal range of the

magnetic field strength as related to the driving temperature difference.

The loop is constructed from glass, with platinum-coated electrodes placed vertically

opposite to each other on each side of the loop walls. A transverse magnetic field is

imposed through a careful design of a set of electromagnets with minimum circuit

reluctance. The lower part of the loop is heated using a hot water bath with thermostat

control, while the upper part of the loop is cooled using a cold water jacket through

which water is recirculated from a water chill unit. The electromagnet provided a

magnetic field strength from 0.01-0.2 T, where as the driving temperature difference

between the hot and cold portion of the loop ranged from 20-80\mDC.

The induced electric voltage from the proposed MHD generator was measured in the

laminar flow range. Preliminary results show that the induced voltage increases with

increased temperature difference between the hot and cold parts of the loop and also

increases with increased electrical conductivity of the salt and water solution.

Thermo syphonic system

The thermo syphonic system is the compactest, easiest and most econic slor system for small

consumer. You can use solar thermo sysphonic systems when you need small amount of hot

water e.g. in household, pare time, summer residence.

This system works in a closed circuit on the thermo syphonic priciple, without pump or control.

With added anti-freeze the system can also be used under cold climates all year round.

Advantages in a nutshell:

low procurement costs

easy istallation and simple design

electricity free operations

no service costs


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Attic central heating

The storage tank can be packed out of the way under the roof. The collectors are mounted on

the roof, above the storage tank.

Stand alone mounting

This is the standard solution for recreational and weekend systems, and for operation in sunny

countries.

thermo siphon

Documents