Hydronic Heating Systems

hydronic heating systems

hydronic heating systems
Northeast Technical Institute Partners with E-Conn to offer HVAC/R Students Real-World Field Experience
Internship program allows NTI students to gain valuable on-site experience with heating and air-conditioning/refrigeration while attending school. (PRWeb January 15, 2011) Read the full story at http://www.prweb.com/releases/2011/01/prweb4969944.htm
solar concentrator idea?

I plan on making a Solar Water Heater, for a hydronic heating system. Would it be efficient to take a satellite dish (like a dish network or direct tv), attach small mirrors on the face of it to concentrate the sun’s heat? I would feed flexible copper tubing through the arm, out to where the receiver would normally be, and twist it around a few times and then bring it back through the arm. I would pump water through the tubing, which would would then circulate through the house and back to the concentrator. I would more than likely put more than one of these in series with each other.
the glass covered box would work, but it wouldn’t be as fun to build, but I’m wondering how efficiently the dish idea would work.

Sound’s like a tracking solar collector. You want to place the heating tube on the focus of the dish

They work very well with direct sunlight (ie clear sky with no clouds) but not all with diffuse sunlight, because diffuse sunlight can’t be focused. Thermal solar panels (ie pipes in cold frames) work with any kind of sunlight. Solar concentrators tend to be used to produce moderate quantities of high temperature steam, where as Thermal solar panels tend to run with higher flows of liquid water and output hot water rather than steam

Controlling the tracking of the mirror is very important with solar concentrators. IF the mirror is pointing in the wrong direction then it’ll not focus the light on the boiler, and the boiler wont heat up.Some controllers have a program which compute where the sun will be at a particular time, but IMHO it’s much simply to have a scan and “lock” system. When it’s light enough for the solar collector to function, simply rotate the mirror through all possibilities until it “fires up”, and then move to a tracking mode.LDRS/photodetectors around the boiler detect when the focus point isn’t right on the boiler, and instruct the mirror to move in an appropriate correcting direction. When it gets dark, device shuts down for the night.

Copper tubing work softens and so it’ll eventually break if you keep flexing it.
Instead of having the boiler/heater moving with the mirror it might be better to arrange things so that the mirror bounces light at a stationary boiler that accepts light/IR by facing the mirror. and the mirror points half way between the boiler and the sun..

I’ve come across a figure for the flux of energy falling on a surface perpendicular to the sun’s rays of about 41.67 W/m².

Don’t know how correct/appropriate that figure is and remember clouds etc will reduce that figure.
A mirror should bounce most of that (especially if the radiation doesn’t pass through glass). Think albedo is an appropriate measure of how reflective a mirror is. If the mirror focuses light on the boiler of smaller area then it’ll increase the energy flux per unit area (but remember the area of the boiler will be less)

P_density=power density at boiler [W][m^-2]
I=Direct insolation [W][m^-2]
T=Transmisivity of atmosphere [dimensionless fraction]
Alb_mirror=Albedo of mirror [dimensionless fraction]
A_mirror=area of mirror perpendicuar to sun beams [m^2]
A_boiler=cross section of boiler perpendicular to light from mirror [m^2]

P_density =I*T*Alb_mirror*A_mirror/A_boiler

The working section of the heater, should function like a heat exchanger with a more or less constant HOT side temperature. It too will have an albedo, and will only be able to absorb a fraction of the heat it is given. As the surface of temperature of the boiler is likely to be high it may be approprate to consider Black body radiation in calculating “albedo”. Newton’s law of cooling might be accurate enough.
Thermal circuit’s should allow calculation of how much heat eventually ends up in the water.

Hydronic Radiant Heat