Investigation on the Optimum Volume-Filling Ratio of a Loop Thermosyphon Solar Water-Heating System

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Tao Zhang ◽  
Gang Pei ◽  
Qunzhi Zhu ◽  
Jie Ji
Keyword(s):  
Temperature Distribution ◽  
Thermal Performance ◽  
Solar Collector ◽  
Filling Ratio ◽  
Working Fluid ◽  
Water Heating ◽  
Solar Water Heating ◽  
Volume Filling ◽  
Solar Water ◽  
Optimum Volume

Volume-filling ratio of the working fluid has a predominant effect on the system performance of a closed two-phase solar water-heating (SWH) system. To study this effect, a prototype of a loop thermosyphon SWH system, which uses remolded flat-plate solar collector as the evaporator and the coil pipe in the water tank as the condenser, was set up. A set of long-term outdoor experiments under 10%, 20%, 30%, 50%, and 70% volume-filling ratios were conducted in this paper. R600a was used as working fluid. Loop thermosyphon solar collector thermal performance and system thermal performance under different volume-filling ratios, including the temperature distribution of loop thermosyphon evaporator, were presented. It is shown that the loop thermosyphon solar collector and the system had a better thermal performance than the conventional ones under 30% and 50% volume-filling ratio, and the loop thermosyphon evaporator had an even temperature distribution when the volume-filling ratio was higher than 30%. The optimum volume filing ratio lies in between 30% and 50% of the whole system volume.

scholarly journals Experimental Study on a Forced-Circulation Loop Thermosiphon Solar Water Heating System

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Tao Zhang
Keyword(s):  
Solar Collector ◽  
Working Fluid ◽  
Water Tank ◽  
Water Heating ◽  
Long Distance ◽  
Reduced Pressure ◽  
Forced Circulation ◽  
Solar Water Heating ◽  
Solar Water ◽  
Condensation Section

Wickless gravity loop thermosiphons (LTs) have been widely used in heat collection for distances up to several meters. This two-phase closed device, which is operating under reduced pressure, is useful in solar water heating (SWH) systems because it could address the freezing problem during winter. Compared to the normal type, forced-circulation wickless LTs have significant advantages in the long-distance heat transfer and installation freedom of condensation section. In this study, a pump-forced wickless LT-SWH system with a remolded flat-plate solar collector was put forward. Solar collector acted as the evaporation section of the wickless LT, while the spiral heat exchanger in the water tank acted as the condensation section. R600a was employed as the working fluid, and long-term outdoor experiments were carried out. Results show that the instantaneous and daily average photothermal efficiency of the proposed system can reach 69.54% and 58.22%, respectively. Temperature differences between the top and bottom and the middle and bottom of the evaporation section of the wickless LT were small, and it usually ranged between 1.1 and 3.9°C. Linear fittings of the collector and system overall performance of the pump-forced wickless LT-SWH system demonstrate the promising potential application of the system.

Experimental Studies on the Thermal Performance of the Balcony-Type Flat-Plate Solar Water Heater

2014 ◽  
Vol 953-954 ◽  
pp. 111-114
Author(s):  
Sheng Xian Wei ◽  
Fen E Hu ◽  
Dong Yu Li ◽  
Hui Li
Keyword(s):  
Water Temperature ◽  
Flat Plate ◽  
Temperature Rise ◽  
Thermal Efficiency ◽  
Solar Collector ◽  
Water Heating ◽  
Solar Water Heating ◽  
Solar Water ◽  
Daily Water Temperature ◽  
Daily Water

Based on the test methods for solar water heating systems, the unsteady thermal efficiency, the daily thermal efficiency and the daily water temperature rise of the balcony-type solar water heating system with a flat-plate solar collector fixed at a large tilt angle (≥60o) have been discussed by the experimental test in Kunming. The results indicate that the average daily thermal efficiencies of the solar collector installed at 60o, 70o, 80o and 90o are around 0.35, 0.39, 0.34 and 0.40. The intercept and the slope of the unsteady thermal efficiency equations are about 0.36~0.44 and 1.62~4.01W·°C-1·m-2. The average daily water temperature rise is 25.2°C, 20.1°C, 18.2°C and 17.4°C for the solar collector fixed at 60o, 70o, 80o and 90o.

scholarly journals COMPARATIVE ANALYSIS OF A PASSIVE SYSTEM WITH AN ACTIVE WATER HEATING SYSTEM BY MEANS OF VACUUM SOLAR COLLECTOR GLASS TUBES

2016 ◽  
Vol 15 (1) ◽  
pp. 15
Author(s):  
J. D. Naranjo ◽  
C. A. Ancines ◽  
C. F. Dos Santos ◽  
A. Krenzinger
Keyword(s):  
Comparative Analysis ◽  
Solar Collector ◽  
Clean Energy ◽  
Heating System ◽  
Circulation System ◽  
Solar Collectors ◽  
Water Heating ◽  
Forced Circulation ◽  
Solar Water Heating ◽  
Solar Water

The importance of renewable energy conversion in heat generation systems is increasing. Being a form of clean energy production, solar water heating systems can substitute part of the electricity consumption in Brazilian energy matrix. Beyond the environmental benefits, the use of such systems brings economic benefits to the country and especially those who use them, saving the use of other energy sources for water heating. In Brazil, the solar water heating is carried out mainly by flat solar collectors, a widely known technology produced in the country at low prices. Nowadays another technology is being used: the evacuated solar collectors. These collectors are being worldwide produced on a large scale and they are imported and inserted at competitive prices in the domestic market. Therefore, it is necessary to understand these systems and their operation to avoid errors in their installation and optimize their use. This work accomplishes a comparative analysis of a solar water heating system composed by a water- in-glass evacuated tube solar collector working in forced circulation, varying the flow, with the same system working in thermosyphon circulation. This comparison was performed by determining the annual energy the system can produce for each type of circulation, which was calculated based on the ISO 9459-2 standard and the climatic data of Porto Alegre city, Rio Grande Do Sul State. To perform these measures, a testing bench was mounted with sensors and measuring instruments which were calibrated before use. The results show that the system with thermosyphon circulation produces more annual energy than the forced circulation system where the water temperature stratification in the thermal reservoir was lower.

A Second Law Approach to Characterising Thermally Stratified Hot Water Storage With Application to Solar Water Heaters

1999 ◽  
Vol 121 (4) ◽  
pp. 194-200 ◽  
Author(s):  
G. Rosengarten ◽  
G. Morrison ◽  
M. Behnia
Keyword(s):  
Temperature Distribution ◽  
Heat Exchangers ◽  
Water Storage ◽  
Heating System ◽  
Hot Water ◽  
Effect Of Temperature ◽  
Storage Efficiency ◽  
Water Heating ◽  
Solar Water Heating ◽  
Solar Water

This paper presents a method of characterising and evaluating the performance of hot water storage systems in terms of their temperature distribution. The change in exergy from the stratified state to the delivery state depends on the stored energy and the stratification. It can thus he used to define the storage efficiency for sensible heat storage devices. A new parameter that isolates the stratification component of the exergy is defined and called the stratification efficiency. The effect of temperature distribution, delivery temperature and tank cross-section on exergy and stratification efficiency is investigated. The advantage that stratification offers over a mixed tank is examined in terms of the storage efficiency and overall solar water heating system performance. Exergy is used to assess the operation of mantle heat exchangers in solar water heating systems and it is shown that exergy and stratification efficiency, as well as energy, should be used to ascertain the performance of such heat exchangers.

Sign in / Sign up

Export Citation Format

Share Document