On this page I'll try to explain how I made a small budget built solar water heater, as usual the idea was to use the cheapest and readily available materials that were lying around.
The main component of the water heater is the car's air conditioner radiator core, , plus the box was made out of thin sheets of stainless steel, plus pink bats heat insulating material - home renovation leftovers, pieces of glass, some silicon hermetic for sealing and glass gluing, the only thing that I had bought for this project is the tube of silicon hermetic.
I will not give you the actual sizes of materials that I used, but will tell you how I built it. The heater was built around the radiator core so all sizes are relating to the radiator, and in your particular case all sizes can be and will be different plus in you case it could have two radiators connected in series in one common box.
All this idea was complete experiment and everything I did were relying on my imagination only plus this solar heater is the first I have ever built, all I knew that the box must be big and deep enough to feet the layer of heat insulation, heat absorbing metal screen, and double glazing.
On pictures below you can see the sheet metal (stainless 0.7mm thick) radiator core and the shape of the future box.
The box is assembled by tick welding - the only fast and safe way for this thin metal, on pictures below you can see the box and the radiator together.
I used silicon sealant that used for bath and shower gaps sealing.
To keep the radiator core in place I welded to the box lower wall two square tubes:
On pictures below you can see the heat insulation.
Here you can see the metal angle was welded around the inner side of the box to make the construction more rigid plus to support the radiator and also the glass in the future.
The thin metal screen was made and installed between the radiator core and heat insulation - for better heat absorption.
The screen was spray painted black and placed to absorb the sun light and to dry :-)
Test run with the single layer of glass.
The pieces of glass of different shape - are off cuts from home renovation were cut to fit into the frame, the gaps were sealed with transparent sealant to let the sun light to get trough the glass, and not let any moisture to get into the solar heater and also not let any heat to escape from the heater.
Solar heater is constructed, built and finished in one day, this small unit can be installed to heat the water for the 200L drum with application of convection method, or connected to the constant water supply and collect the amount of warm water that needed for certain needs, (to wash your car or hands ) though the speed of water flow is not that fast, in my case at water flow speed of 10L per hour I had constant water temperature over 40 degrees Celsius, water coming from the main water supply and no warmer than 10 degrees Celsius plus there is only 12 degrees outside, and remember this is solar heater and works best when there is direct sun light.