Heat sink for 2 collectors of 2 to 2.5 m2. Remove excess heat generated by the solar hot water installation.

 

 

 

Heat sink for 2 collectors of 2 to 2.5 m2. Remove excess heat generated by the solar hot water installation.

 

Gravity heat sinks are protection systems without electrical components, which eliminate excess heat generated by solar thermal energy systems, both with flat panels and with vacuum tubes.

The gravity heat sinks are made up of a thermostatic valve pre-set at 90 ºC, equipped with a mechanical expansion actuator, a heat exchanger by natural convection and circulation by gravity.

They meet, with total reliability, the requirements of the technical building code, HE4 section 3.2.2.3.1; the RITE, the Barcelona Solar Ordinance OST Inspection Guide, V 2.0.-July 11, 2007, the UNE EN 12828 standard to limit the outlet temperature of the solar collectors to 105 ºC and the rest of the ordinances applied in the Spanish territory.

Its operation does not depend on solenoid valves, motor pumps, fans or electrical supply.

Gravity heat sinks extend the useful life of installations and eliminate corrective maintenance interventions, since they avoid problems of:

• - Corrosions and incrustations inside the collectors due to air inlets
• - Cavitation of electric pumps
• - Degradation of the selective surfaces of the collectors
• - Degradation of the heat-bearing fluid
• - High pressures and losses of the heat-bearing fluid
• - Aging of the facility
• - Thermal stress of the installation (avoiding large thermal jumps between the ambient temperature and that of the collector)
• - To a large extent, the maintenance of the installation is carried out by the static dissipation itself.

DESCRIPTION OF THE OPERATION OF THE GRAVITY HEAT SINKS:

The temperature of 90 ° C has been considered as the limit conditions for operation of a solar thermal energy system with flat collectors. The system is composed of: 4-way thermostatic valve with cyclonic air separator and by-pass tube, finned copper heat exchanger in 3- and 6-tube coils, check valve. It allows three different possibilities of operation:

Normal functioning:

• The heat-carrying fluid passes exclusively through the collector field. The check valve prevents circulation through the heat exchanger. At temperatures below 90 ° C the valve opens the passage of water to the installation and keeps the path to the heat exchanger closed.

Partial dissipation with pump (low energy demand):

• In times of high solar input and low heat demand, a typical summer situation, and when the collector outlet temperature is around 90 ° C, the valve starts to open the path to the heatsink and occurs fluid cooling. From this moment on, the valve will pass more or less towards the heatsink, depending on the outlet temperature. The by-pass tube plays the return role of the heat exchanger. The higher the temperature, the larger the outlet section to the exchanger and the smaller the passage to the installation, and vice versa. The double plunger of the valve will position itself automatically, maintaining the set temperature limit of 90 ° C at all times.

Dissipation by gravity (pump stop):

• When the electric pump set is disconnected (failure, power supply interruption, absence due to school holidays, etc.) quickly, the fluid in the collectors reaches the maximum setpoint temperature, 90 ° C. The check valve, which is always open when the pump stops working, automatically establishes the circulation by gravity, THERMOSIPHON, between the collector flow, the by-pass pipe and the collector return. The water circulates through the by-pass pipe in the opposite direction and transmits the highest temperature of the fluid to the valve sensor. The valve opens the way to the exchanger and it will cool its entire surface. As in the previous case, the valve will position itself automatically limiting the approximate thermal jump of 60 ° C between the fluid in the collectors and the ambient temperature. The cold return water from the exchanger, with a higher specific weight than the hot water from the collectors, generates enough pressure to establish the circulation of the fluid, so that dissipation is regulated without more energy than that due to gravity.