- To measure the Outlet and Inlet Temperatures, and mass flow rate of the evacuvated tube collector with Water as the heat transfer medium.
- To plot the Inlet and Outlet temperatures, and flow rates versus Time.
- To calculate the Efficiency of the compound parabolic concentrator.
Background and theory
After determining a suitable site with ambient or maximum solar radiation I,e where we have the amount of solar energy ready for use, we would require a suitable method to convert this energy into useful form or products like power generation, hot water, solar air-conditioning.
One of the method to do the same is by means of flat plate collector, which absorbs the solar radiation( heat energy ) and the output generated by this apparatus is hot water or hot working fluid, which can be used for appropriate purposes.
The main parts of typical flat plate collector are
1. Absorber plate- Absorbs the solar energy form the solar radiation and is made of great heat absorbing material and they are painted dark in colour to have good thermal absorption. Main functions are: absorb the maximum possible amount of solar irradiance, conduct this heat into the working fluid at a minimum temperature difference, and lose a minimum amount of heat back to the surroundings
2. Transparent cover – Reduces convective heat loss, natural convective air current created because the absorber is hotter than ambient air. This may be also due to the thermal resistance of the added air space.
3. Heat transport fluid - Fluid circulating through tubes(glass or polycarbonate) absorb the heat from the plate, this hot fluid is then utilised for our required purpose.
4. Heat insulating backing.
Evacuvated tube collector is not so commonly used solar collector as a flat plate collecor. This is now commonly available technology which is widely used in air- conditioning and other water heating applications.
The evacuvated tubes are made from low emissivity borosilicate glass with glass covering on the top and they are coated with aluminium or copper to absorb whole radiation to generate heat. This technology works well even in diffused sunlight.
Evacuated Tube Collectors
In this type the absorber plate is fused to the tube (Heat pipes) through which the transport fluid flows, making the solar energy absorption direct.
To the transfer fluid the heat is given by heat exchanger of the heating system (manifold).
fig- glassevacuated tube
Pic of single evacuvated tube
fig - Cross Section of ETC
Experiment Setup and working
We are using water as the heat transfer fluid in this experiment. Cold water is circulated through a series of these evacuated tubes. When water passes through these narrow copper tubes, it absorbs heat energy from these copper tubes. Temperature of the water is thus increased.
Flow rate of water can be varied by controlling the pumping pressure of the motor. Inlet and outlet water temperature is constantly monitored. At any given time the outlet temperature will be greater than or equal to the inlet temperature. In this experiment, user can vary the flow rate of water and analyze the inlet, outlet and tank temperature variations. Solar radiation intensity of the location is also constantly monitored, which can impart the user with the insight of the heat energy absorbed by the heat transfer fluid with a given solar radiation intensity
For any study of the thermal behaviour of the water circulating in FPC we can use the data obtained from this experiment, that is one could know about the different temperature of water circulating in the tubes for different flow rate.
One can study the different phenomena happening in solar energy conversion or flat plate collector system, ie, conduction, absorption of solar radiation, thermal effectiveness of a material, convection and re-radiation
Solar AC is a great application of the flat plate collector setup. For designing an efficient solar AC we need certain parameters, and some main parameters required for the same can be obtained from the result or observation of this particular experiment.