Introduction to heat shock in solar water heating projects
Thermal shock resistance refers to the thermal shock resistance of solar collectors and solar hot water engineering systems. It indicates the resistance of solar collectors and solar water heating systems to the dramatic changes in internal and external working fluids and ambient temperature, respectively according to national standards. GB/T 6424—1997 “Technical conditions for flat-plate solar collectors”, GB/T 17049-2005 “All-glass vacuum solar collectors” and GB/T 19141—2003 “Technical conditions for domestic solar water heating systems” The test conditions are determined and divided into an internal thermal shock test and an external thermal shock test.
1 Internal thermal shock test
a• Flat-plate solar collectors when the solar irradiance of the collector plane reaches 750W/m2 or more, air drying for 30min, then water is passed through the heat absorber for 5min, the water temperature is 15°C ± 10C, and the flow rate is not less than 60kg/( M2*h).
b•All-glass vacuum solar collector tube Insert the collector tube opening into the ice-water mixture of not less than 0 °C, the insertion depth is not less than 100mm, and after stopping for lmin, immediately remove and insert the hot water above 90X: the insertion depth is not Less than 100mm, take it after lmin and take it out and insert it no less than. In the ice-water mixture of C, it is repeated three times.
c• Solar hot water engineering system solar water heating engineering system should be under the quasi-steady state of solar irradiance ≥800W/ m2, air drying for lh, then pass cold water for 5min, water temperature <25°C, flow M>72kgA m2. h), ambient temperature > 15 °C.
2 External thermal shock test
a•Slab type solar collector, when the solar irradiance of the collector plane reaches 750W/m2, it is aired for 30min, then sprayed to the collector for 5min, and the direction of water spray is sandwiched between the transparent cover of the collector. The angle should be greater than 20 °, the water temperature is 15 ° C ± 10 C, and the flow rate is greater than 200 kg A m2.h).
b•Solar hot water engineering system The solar hot water system should be air-dried for 1 hour under the quasi-steady state of solar irradiance ≥800W/m2, then sprayed with water for 15min, water temperature <25°C, flow rate is 180~216IV (m2 .h), Ambient Temperature" 15t:> Two external thermal shock tests shall be carried out.