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   TRX Evacuated Tubes   with TRX Selective Coating
Descriptions Specifications Accelerated Aging Test Aging Test Report Conclusions
   

Descriptions

 

 

 

 

 

 

   

  • Made of high strength boron silicate glass tubes with high vacuum in between the tubes .  The outer wall of the inner tube is coated with TRX's proprietary CU-N/AL selective coating . Mo-Al2O3 is available for higher temperature application ,

  • Cu-A/AL selective coating allows 94 to96% of solar radiation energy to be absorbed while emit less than 7% of heat through Black body radiation.

  • Life span of coating is much longer than other equivalent system .

  • Efficiency of energy conversion maintains throughout the working life

 

  Specifications

 

 

 

 

 

 

 

 

Coating type

Cu-N/AL

Mo-Al2O3

Absorptionam=1.5

92-96%

92-96%

Emissivity150C

7%

6%

Inner & outer tube size (mm)

37/47      47/58     54/65

Tube length (mm)

Factory standard: 300、500、1000、1200、1500、1800、2000

Odd size tubes may be produced .

Suggested working temperature C

330

450

Vacuum in the tube

2.510-3 Pa

Coefficient of heat loss

0.8W/m2*K
Material of glass Very high strength well tempered Boron Silicate glass
Transmittance of light 91%
Life expectancy >15 years >30 years

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Accelerated Aging Test

 

 

 

 

 

 

Test Procedures

1.  Place the evacuated tube horizontally , insert a hot air heating tube in the middle  with the hot air blowing at  temperature capable of above 500 deg C ( 932 deg F ). The temperature of the tube is measured by placing  3 thermocouples in inner wall of the tubes and one at the outlet . 

2.  Temperature of the tube were raised to a constant 420 deg C (788 deg F )  It is maintained for the duration of the test ( 30 minutes and 60 minutes )

3. Any change in the color of the thin film coated tube  was recorded , as well as the color of the end of the evacuated tube ( Silver color Barium coating  , the silver color will turn white if the vacuum of the tube is lost .)

4. At the end of high temperature exposure , the evacuated tube was cracked to retrieve the inner Thin Film coated tube .  Heat Absorption and Emission tests were carried out  .  Test data of before and after heat exposure were recorded and compared .

5. 30 minutes of 420 deg C ( 788 deg F ) high heat exposure is equivalent to 8 years of normal operating life ( under normal operation the inner tube wall temperature is about 250 deg C, or 482 deg F   )                                                                                                       Go Top 

  Aging Test Results

 

 

 

 

 

 

 

TRX        with CU-N/AL

TRX      with CU-N/AL

Other maker with      Al-N/AL

Test sample markings

200407020103

200409250117

China made evacuated tube

Test date

2004 07 03 

2004 09 28 

2005 03 03 

Heat Exposure Time(420 C)

60 minutes

60 minutes

30 minutes

Observation

After

Before

After

Before

After

Before

Color of Barium coating

 No Change

 No Change

 No Change , but the barrier coating was reduced by 10 mm

Color of inner coated tube

 No Change

 No Change

 No Change

Heat Absorption

94.5% 

95.9%

95.2% 

95.2%

82.0% 

93.6%

Heat Emissivity       ( loss)

6.9%  

5.3%

5.9%  

5.6%

22 %

8.5%

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  Conclusions

 

 

 

  1.  After 60 minutes exposure to 420 deg C , ( equivalent to 16 years of working life ) TRX evacuated tubes shows little degradation of thermal absorption and heat emission efficiency.

2.  Competitive evacuated tubes with AL-N/AL coating suffers significant degradation of efficiency after just 30 minutes of exposure . ( 8 years of working life ) . The heat absorption efficiency drops by 13 percents and the heat loss through emission increased by 250 percents .

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