All-glass vacuum tube solar panel water heater to run in the winter

I. Introduction



The variety is very early all-glass vacuum tube solar panel collector (hereinafter referred to as the vacuum tube) single to the late 1990s, the main products are long 1.2m, cover glass tube outside diameter 47mm tubes. But precisely made of all-glass vacuum tube solar panel water heater (hereinafter referred to as the vacuum tube water heater), normal winter running, and gradually replaced the winter can not run flat-type water heater, so it is to the rapid development . Variety of vacuum tube, vacuum tube water heater industry, the situation is excellent. But over the years has been spreading some ambiguous statement, such as pipe length is shorter than 1.8m vacuum tube water heater in the winter "bad", will "hibernate", will "strike". In this paper, a vacuum tube water heater in the winter run test data, hoping to play a valuable role in recognize these claims.



Second, the vacuum tube thermal performance test



Vacuum tube to the technical requirements of the national standard nine, three of which related to the thermal properties, they are: air drying performance parameters Y (m2 ° C / kW) the Y larger the value, the better; amount of stuffy sun irradiation H (MJ / m2), H values ​​the smaller the better; Average heat loss coefficient ULT (W/m2 ℃), ULT smaller the value, the better. Table 1 lists the different length of the tube of the same manufacturer, different diameter vacuum collector tube test parameters (Note: they are to meet the technical requirements, where Y ≥ 190m2 ° C / kW, H ≤ 3.7MJ/m2 and the H ≤ 4.7MJ/m2 the cover glass tube diameter of 47mm and 58mm two kinds ULT ≤ 0.85W/m2 ° C), table 37/47-1500 37/47 said inner tube, cover glass tube diameter 37mm and 47mm, 1500 said pipe length 1.5m, the rest and so on.



Can be seen from Table 1, regardless of the length of the tube is 1.5m, 1.6m, 1.8m, cover glass tube diameter is 47mm, 58mm, strict production process, the production of different length, different diameter vacuum collector tube hot Performance does not have significant differences.



Vacuum tube water heater thermal performance test



Vacuum tube water heater according to the technical requirements of the national standard of 17, which is a thermal performance, thermal performance is divided into day useful energy q (q value is excellent) and the average heat loss factor USL (USL smaller). Table 2 lists the different length of the tube of the same manufacturer,power inverter different diameters,grid tie inverter different types of water heaters thermal performance parameters (Note: they are able to meet the technical requirements, where q ≥ 7.5MJ/m2 USL ≤ 22W/m3 · K ), Table 2 Ф47 Ф58 cover glass tube diameter, L1500, L1800, said the length of the tube. L1500 4 L1800 6.



Seen from Table 2, any collector tube consisting of 10 models of the water heater, as long as the quality assurance, its thermal properties, and no significant differences.



1. Water heater in a single day in the winter



Vacuum tube water heater JB4715-21-150/45, it is composed by 21 pipe length 1.5m, cover the collector tube of glass tube diameter 47mm, the center of the tube spacing 70mm, water 150kg, collector inclination 45 °, lighting area 2.04 m2, with the ginning aluminum reflector. A year tracking test this model of water heater, place in Beijing. Table 3 is a water heater in the winter under three different climatic conditions results run from 8:00 to 16:00.



In the three-day average daily temperature below 0 ℃, if a sufficient amount of solar panel radiation, water heater running day to a hot water bath, such as 12, 26 May; hearing amount of solar panel radiation, water heater running day reach the bath water temperature from the hot water temperature required auxiliary heating, add a point of heat, as December 14; snow, such as December 19, the amount of solar panel radiation are undetectable, the water heater warming 0.2 ℃ (can be negligible), the vacuum tube water heater only play the holding role, have to thanks to the auxiliary heating bath water, even so, it will continue to work, not "dormant", not "strike". Solar panel water heaters are generally equipped with electronic instruments to control the electric auxiliary heating device, under the conditions of insufficient sunshine timing to provide auxiliary heating, and electric water heaters are not very different. Case of snow days, nor auxiliary heating,grid tie inverter pipe length 1.8m vacuum tube water heater temperature to reach the bath temperature, then the tube long at 1.8m vacuum tube water heater will be able to reach the bath water temperature? From a scientific point of view, the expert in this field did not dare to jump to conclusions.



2 runs continuously for many days in the winter, the water heater



To sum up, the vacuum tube water heater has the advantage of "dormant" in the cold winter weather,power inverter insufficient light conditions nor auxiliary heating, for this reason, it can continuous multi-day run. Table 4 shows the vacuum tube water heater running continuously for many days in Daqing in JB4715-24-150/45 test results. The water heater by 24 pipe length 1.5m,power inverter cover the glass tube diameter 47mm tubes, pipe center spacing of 61mm, water 150kg, the collector is inclination of 45 °, daylighting area 2.042m2, without the reflector plate.