Water-in-glass evacuated tube solar water heaters

Solar Energy ◽  
2004 ◽  
Vol 76 (1-3) ◽  
pp. 135-140 ◽  
Author(s):  
G.L. Morrison ◽  
I. Budihardjo ◽  
M. Behnia
Keyword(s):  
Solar Water ◽  
Water Heaters ◽  
Solar Water Heaters ◽  
Evacuated Tube

Numerical Simulation of Evacuated Tube Solar Water Heaters

2012 ◽  
Author(s):  
Michele Pinelli ◽  
Alessio Suman ◽  
Michele Vanti
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Circulation Rate ◽  
Heat Distribution ◽  
Solar Water ◽  
Water Heaters ◽  
Reference Parameters ◽  
Solar Water Heaters ◽  
Evacuated Tube ◽  
Rayleigh Numbers

This paper evaluates the characteristics of water-in-glass evacuated tube solar water heaters including assessment of the circulation rate through single ended tubes. A numerical model of the fluid flow inside a single ended evacuated tube has been developed assuming no interaction between adjacent tubes in the collector array. The numerical model is firstly validated by means of literature data. Then, the performance in terms of circulation mass flow rate in different heat flux condition and at different inclination angle of the collector are evaluated. Moreover, a sensitivity analysis on the effect of the assumptions of different reference parameters and of the choice of the values of the fluid thermophysical properties is carried out and a quantitative analysis of the expected uncertainty is presented. Finally, an extension of previous literature correlations in terms of non-dimensional Reynolds and Rayleigh numbers is proposed. Regarding heating boundary conditions, the circumferential heat distribution was found to be an important parameter influencing the flow structure and circulation rate through the tube.

Experimental Investigation of Evacuated Tube Solar Collector with Annular Heat Exchanger

2014 ◽  
Vol 592-594 ◽  
pp. 2355-2359
Author(s):  
Narasimhe Gowda ◽  
B. Putta Bore Gowda ◽  
R. Chandrashekar ◽  
G. Ugrasen ◽  
R. Keshavamurthy
Keyword(s):  
Closed System ◽  
Single Phase ◽  
Working Fluid ◽  
Maintenance Cost ◽  
Phase System ◽  
Two Phase ◽  
Solar Water ◽  
Water Heaters ◽  
Solar Water Heaters ◽  
Evacuated Tube

Now-a-days evacuated tubes solar water heaters are increasingly use in South India because of good thermal efficiency and high water temperature could be achievable as compared to flat plate solar collectors. Low manufacturing and maintenance cost also attract people to go for evacuated tube solar water heaters. This paper reports experimental results of two types of evacuated tube solar water heaters. To evaluate the performance of evacuated tube solar water heater, single-phase forced system and two-phase closed forced systems were considered. In two-phase closed system sunflower oil was used as working fluid to heat water. Throughout the study two-phase closed system shows better performance compared to single-phase open collector system and their efficiency almost 10 to 12% higher. But, because of high initial cost of two-phase system, the pay back periods of both collector systems is almost same. In two phased closed system higher temperature of water could be achieved, which is very useful to operate advanced system.

Effects of Tube Space on the Thermal Performance of Water-in-Glass Evacuated Tube Solar Water Heaters

2013 ◽  
Vol 860-863 ◽  
pp. 81-87
Author(s):  
Yu Qin Yang ◽  
Run Sheng Tang
Keyword(s):  
Thermal Performance ◽  
Theoretical Calculations ◽  
Technical Specification ◽  
Water Heater ◽  
Solar Water ◽  
Water Heaters ◽  
Solar Water Heaters ◽  
Evacuated Tube ◽  
Tube Space ◽  
Tube Distance

In the present specification of domestic solar water heating systems (GB/T19141), regardless of the type of collectors used in the systems, Q17, the daily heat gain corresponding to the daily radiation of 17MJ/m2 on the collector surface, is a key indication to rate the thermal performance of a domestic solar water heaters. In this work, an attempt was made to investigate effect of the distance between two adjacent tubes in solar tube collectors of a water-in-glass evacuated tube solar water heater (ETSWH) on by theoretical calculations and experimental measurements. Results obtained by simulations and experimental test showed that the tube space had a significant effect on of the ETSWH, the shorter the tube distance, the higher the Q17, thus better the ETSWH performs. However, the actual situation is the case, the shorter the tube distance, the lower the real daily solar gain of the system, thus worse it performs. This implied that Q17 as the indication of thermal performance of the ETSWH is not reasonable, and specifying the tube distance in solar tube collectors of the ETSWH in the technical specification of GB/T19141 is advisable so as to eliminate effect of the tube distance on Q17.

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