Apricus Quality

Material quality and cleaning is extremely important to the creation of a quality product.

Heat pipe

Impurities inside the heat pipe it will effect the performance. The purity of the copper must be very high, containing only trace amounts of oxygen and other elements. Copper containing excess oxygen or other elements, will leach into the vacuum reducing the efficiency of the heat pipe.

Heat pipes used in Apricus solar collectors do not require use a wick or capillary system to aid the flow of the liquid as the interior surface of the copper is extremely smooth, allowing efficient flow of the liquid back to the bottom.

Apricus solar heat pipe collectors are comprised of two copper components, the shaft and the condenser. Prior to evacuation, the condenser is brazed to the shaft. The condenser has a much larger diameter than the shaft to provide a larger surface area over which heat transfer to the header can occur.

Each heat pipe is tested for heat transfer performance and exposed to 250^oC (482^oF) temperatures prior to being approved for use. For this tempers the copper heat pipes to a relatively soft state.

Freeze Protection

The freezing point of water remains the same as water at sea level, 0^oC (32^oF) regardless of vacuum. Because the heat pipe is located within the insulated evacuated glass tube, brief overnight temperatures as low as -20^oC (14^oF) will not cause the heat pipe to freeze. The water used in Apricus while treated with a proprietary chemical will still freeze in cold conditions. However, but it freezes in a controlled way that does not cause swelling of the copper pipe.

Glass

Apricus Evacuated Tube Basic Specifications

Length (nominal)	1500mm/1800mm
Outer tube diameter	58mm
Inner tube diameter	47mm
Glass thickness	1.6mm
Thermal expansion	3.3x10-6 ^oC
Material	Borosilicate Glass
Absorptive Coating	Graded Al-N/Al
Absorption	>92% (AM1.5)
Emittance	<8% (80^oC)
Vacuum	P<5x10-3 Pa
Stagnation Temperature	>200oC
Heat Loss	<0.8W/( m2^oC )
Maximum Strength	0.8 MPa