Heat Pipe Collectors
Solar Heat Exchange Manufacturing is proud to represent Sun Task heat pipes.
Sun Task's product has one of the highest SRCC ratings in the industry. The product is reliable and durable, backed by a 10 year warranty. Installation is straightforward and relatively easy. Their compact size allows for a wide range of applications.
Heat pipe collectors introduce new aethstetic possibilities in design. The balcony to the left is one example of a growing trend to incorporate heat pipe technology as a visual element of design.
The Sun Task SRCC evaluation provides an excellent comparitive overview of the product.
From Evacuated Tubes to Heat Pipes
SHEM's early experience with evacuated tubes was most unsatisfactory. When evacuated tubes first hit the market, they were touted as the next generation solar thermal collector technology. Early production failed to meet promise of technical reports and marketing promises. In short, early evacuated tube production was problematic to the point of failure. To the right is a picture of SHEM's first set of evacuated tubes. Tubes broke in mild hail storms. Vacuum was lost for no particular known reason. When tubes were intact and operating, high stagnation temperatures lead to steam flashing. The problems were legend.
That was then, this is now.
The vacuum tube industry reponded to early problems with a new generation of heat pipe evacuated tubes. Problems associated with early production were addressed. The heat pipe of today is highly competent, boasting a vastly superior function and design than that of the early evacuated tube.
Sun Task Heat Pipes
Technically, Sun Task uses the lastest German Borosilicate glass technologies for the evacuated tube. Each evacuated tube consists of two glass tubes made from extremely strong borosilicate glass. The outer tube is transparent allowing light rays to pass through with minimal reflection. The inner tube is coated with a special selective coating (Al-N/Al) which features excellent solar radiation absorption and minimal reflection properties. The tops of the two tubes are fused together and the air contained in the space between the two layers of glass is pumped out while exposing the tube to high temperatures. This "evacuation" of the gasses forms a vacuum, which is an important factor in the performance of the evacuated tubes.
If you have used a glass lined thermos, you've experienced the excellent insulating properties of a vacuum. Vacuum helps to prevent the loss of heat collected by the absorber plate. Vacuum insulation properties are so good that while the inside of the tube may be 150oC / 304oF , the outer tube is cold to touch. Evacuated tube water heaters can perform well even in cold or cloudy weather, while flat plate collectors perform poorly in similar conditions due to heat loss (during high Delta-T conditions).
In order to maintain the vacuum between the two glass layers, a barium getter is used (the same as in television tubes). During manufacture of the evacuated tube this getter is exposed to high temperatures which causes the bottom of the evacuated tube to be coated with a pure layer of barium. This barium layer actively absorbs any CO, CO2, N2, O2, H2O and H2 out-gassed from the evacuated tube during storage and operation, thus helping to maintaining the vacuum. The barium layer also provides a clear visual indicator of the vacuum status. The silver coloured barium layer will turn white if the vacuum is ever lost. This makes it easy to determine whether or not a tube is in good condition.
The heat pipe plays a very important role in this solar collecting system. The heat pipe is composed of a heat energy absorption unit and a condenser unit, which is hollow with the space inside evacuated then filled with a heat transfer medium. Under vacuum, the air pressure inside heat pipe is very low, thus the heat transfer medium is evaporated easily when absorbing the sun's energy. This vapor rapidly rises to the condenser zone in the bulb of the heat pipe, where it transfers heat to the collector loop fluid. The heat transfer medium cools and liquifies, returning to the bottom of the heat pipe once the heat is lost. This process repeats again and again, continuously tranferring solar energy.
The condenser zone (the bulb) of the heat pipe is inserted into copper sleeves which are evenly distributed on the maniforld at the top of the collector. After solar energy is absorbed by the vacuum tubes, it is transferred to the heat pipe through an aluminum fin. Heated by the sun's energy, the medium in the heat-pipe rises and transfers heat energy to the condenser zone. Heat is transferred from the heat pipe when water or glycol in the manifold flows across the copper sleeves which were heated by the condenser zone bulb.
In cooperation with heat pipe factory engineers, Solar Heat Exchange Manufacturing can design, install and maintain commercial or industrial hot water systems, at any scale.
For more ordering information, please contact us.
Back to top^