scholarly journals Long-Term Performance of Anti-Freeze Protection System of a Solar Thermal System

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1286
Author(s):  
Sebastian Pater
Keyword(s):  
Winter Season ◽  
Heating System ◽  
Protection System ◽  
Solar Thermal ◽  
Long Term Results ◽  
Solar Collectors ◽  
Evacuated Tube Collectors ◽  
Term Performance ◽  
Freeze Protection

In a moderate, transitory climate, to prevent freezing of outdoor pipes and collectors in solar thermal systems, anti-freezing fluids are commonly used. There is little experience of using water without any additives as a solar thermal fluid in such a climate. Based on these findings, to fill the knowledge gap this article presents the long-term results of thermal performance and anti-freeze protection of a solar heating system with heat pipe evacuated tube collectors with water as a solar thermal fluid. The operation of this system under real conditions was analysed for five years in southern Poland. The annual value of solar insolation ranged from 839 to almost 1000 kWh/m2. The monthly efficiency of the solar collectors from March to October was usually higher than 25%, and the lowest was between November and January. The anti-freeze protection system consumed annually from 7 to 13% of the heat generated by the collectors in the installation. Supporting the operation of the central heating system in the building during the winter season highly improved the efficiency of the solar collectors. Results show that it is possible to use water without any additives as a solar thermal fluid in a moderate, transitory climate.

A Rating Procedure for Solar Domestic Water Heating Systems

1983 ◽  
Vol 105 (4) ◽  
pp. 430-439 ◽  
Author(s):  
S. A. Klein ◽  
A. H. Fanney
Keyword(s):  
Heating System ◽  
Testing Procedure ◽  
Hot Water ◽  
National Bureau ◽  
Water Heating ◽  
Domestic Water ◽  
Solar Water Heating System ◽  
Long Term Performance ◽  
Term Performance

A rating procedure for solar domestic hot water systems is described which combines the advantages of short-term system tests and correlations of long-term thermal performance. The testing procedure consists of two indoor tests which are in accordance with ASHRAE Standard 95-1981, except for one additional measurement needed only for systems employing a heat exchanger between the collector fluid and the potable water. The test results are plotted in a manner in which they can be used to estimate the long-term performance of the solar water heating system for any location where site-specific, monthly-average meterological data are available. The annual solar function obtained in this manner provides the recommended rating indicator. The validity of this rating procedure is first demonstrated by simulations. Further support is provided by experiments conducted at the National Bureau of Standards.

Long-term performance of flat-plate solar collectors

1980 ◽  
Vol 7 (1-3) ◽  
pp. 119-128 ◽  
Author(s):  
G. Ambrosone ◽  
A. Andretta ◽  
F. Bloisi ◽  
S. Catalanotti ◽  
V. Cuomo ◽  
...  
Keyword(s):  
Flat Plate ◽  
Solar Collectors ◽  
Long Term Performance ◽  
Term Performance

scholarly journals Nanofluids in Solar Thermal Collectors: Review and Limitations

2020 ◽  
Vol 41 (11) ◽  
Author(s):  
Ifeoluwa Wole-osho ◽  
Eric C. Okonkwo ◽  
Serkan Abbasoglu ◽  
Doga Kavaz
Keyword(s):  
Heat Transfer ◽  
Material Science ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Full Potential ◽  
Solar Collectors ◽  
Solar Thermal Collectors ◽  
Overall Efficiency ◽  
The Impact

Abstract Solar thermal collectors are systems that allow for the use of solar energy in thermal applications. These collectors utilize a heat transfer fluid to transport absorbed solar radiation to applications where they are needed. Scientists in a bid to improve the conversion efficiency of solar collectors have suggested different collector designs and improved collector materials. Over the last 25 years, the study of nanofluids and their applications have revolutionized material science, and nanotechnology has found applications in improving solar collector materials. This article reviews the impact of different nanomaterials on the efficiency of solar collectors. The study also outlines the limitations of applying nanofluids and discusses the long-term challenges of their application to solar collectors. Nanofluids have the potential to improve the overall efficiency of most solar collectors, however, the full potential of nanofluids in heat transfer applications cannot be completely achieved until some of the questions regarding hysteresis, stability, and the overall predictability of nanofluids are answered.

scholarly journals Long-Term Results (up to 20 Years) of 19 mm or Smaller Prostheses in the Aortic Position. Does Size Matter? A Propensity-Matched Survival Analysis

2021 ◽  
Vol 10 (10) ◽  
pp. 2055
Author(s):  
Horea Feier ◽  
Andrei Grigorescu ◽  
Lucian Falnita ◽  
Oana Rachita ◽  
Marian Gaspar ◽  
...  
Keyword(s):  
Aortic Root ◽  
Long Term Results ◽  
Original Cohort ◽  
Propensity Matching ◽  
Small Aortic Root ◽  
Long Term Performance ◽  
Term Performance ◽  
Size Matter

Background: The long-term performance of prostheses in the small aortic root is still unclear. Methods: Patients who received a 21 mm or smaller aortic valve between 2000–2018 were retrospectively analyzed. Propensity matching was used in order to account for baseline differences in 19 mm vs. 21 mm valve subgroups. Results: Survival at 10 years was 55.87 ± 5.54% for 19 mm valves vs. 57.17 ± 2.82% for 21 mm ones in the original cohort (p = 0.37), and 58.69 ± 5.61% in 19 mm valve recipients vs. 53.60 ± 5.66% for 21 mm valve subgroups in the matched cohort (p = 0.55). Smaller valves exhibited significantly more patient–prothesis mismatch (PPM) than larger ones (87.30% vs. 57.94%, p < 0.01). All-cause mortality was affected by PPM at 10 years (52.66 ± 3.28% vs. 64.38 ± 3.87%, p = 0.04) in the unmatched population. This difference disappeared, however, after matching: survival at 10 years was 51.82 ± 5.26% in patients with PPM and 63.12 ± 6.43% in patients without PPM. (p = 0.14) Conclusions: There is no survival penalty in using 19 mm prostheses in the small aortic root in the current era. Although PPM is more prevalent in smaller sized valve recipients, this does not translate into reduced survival at 10 years of follow-up.

Intercomparison of Long-Term Performance Prediction Methods for a Flat-Plate Domestic Solar Water Heating System

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Huai S. Xue
Keyword(s):  
Performance Prediction ◽  
Heating System ◽  
Prediction Methods ◽  
Water Heating ◽  
Solar Water Heating ◽  
Solar Water ◽  
Solar Water Heating System ◽  
Long Term Performance ◽  
Term Performance

Long-term performance estimations were performed on a nonstandard domestic solar water heating system by f-Chart, interactive F-Chart software, and φ¯,f-Chart methods. Results of estimations were compared to gain insight of their applicability. Results from F-Chart software and f-Chart agree well and are greater than those from the φ¯,f-Chart method. Energy dumping should be given thorough reconsideration for the refinement of f-Chart and F-Chart software.

scholarly journals Residential Solar Thermal Performance Considering Self-Shading Incidence between Tubes in Evacuated Tube and Flat Plate Collectors

2021 ◽  
Vol 13 (24) ◽  
pp. 13870
Author(s):  
Esteban Zalamea-Leon ◽  
Edgar A. Barragán-Escandón ◽  
John Calle-Sigüencia ◽  
Mateo Astudillo-Flores ◽  
Diego Juela-Quintuña
Keyword(s):  
High Altitude ◽  
Flat Plate ◽  
Energy Requirement ◽  
Solar Thermal ◽  
Complete Analysis ◽  
Solar Collectors ◽  
Climate Conditions ◽  
Real Performance ◽  
Evacuated Tube Collectors ◽  
Evacuated Tube

The performance of solar thermal technology under high-altitude equatorial climatic and solar path conditions has not been determined. Evacuated tube solar collectors are more efficient than flat plate collectors in cold and cloudy regions; however, due to their dependence on orientation, the irradiation incidence between the tubes of these collectors can be blocked. In this study, the performance of these types of collectors was analyzed to determine the implications of their orientation under these specific climate conditions. Four solar thermal systems were installed: two of the systems used evacuated tube collectors, and two used flat plate collectors. Each collector was connected to storage and discharge points to simulate residential consumption when observing the real performance of the four systems in terms of irradiation availability. The evacuated tube collectors were more efficient and reduced the backup energy requirement by up to 20.6% more on average than the flat plate collectors. In addition, the performance of the evacuated tube collectors increased by up to 9.8% when the tubes were arranged parallel to the solar path, compared to when they were arranged perpendicular to the solar path, verifying that the blockage effect is an important parameter to consider for evacuated tube technology. The main novelty of this research is the comparison of these two technologies under different orientations, with perpendicular and parallel dispositions toward the solar path, in a high-altitude equatorial location where solar collectors are not typically oriented in any particular orientation. To the best of our knowledge, this is the first complete analysis of real systems deployed under these conditions.

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