Performance analysis of the evacuated tube counter-flow absorber and direct-flow absorber to optimize the heat extraction rate for high flow rate applications
The evacuated tube collector (ETC) has gained extensive use in low-temperature applications due to its cheapness and high efficiency. The ETC can be used with a concentrator for medium temperature applications, in the range of 140–200 °C. However, the heat extraction rate of the absorber tube is a l...
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| Format: | Article |
| Language: | English |
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Elsevier
2023-03-01
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| Series: | Heliyon |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2405844023014330 |
| _version_ | 1797851828538310656 |
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| author | Shaibu Tambula Downmore Musademba Chido H. Chihobo |
| author_facet | Shaibu Tambula Downmore Musademba Chido H. Chihobo |
| author_sort | Shaibu Tambula |
| collection | DOAJ |
| description | The evacuated tube collector (ETC) has gained extensive use in low-temperature applications due to its cheapness and high efficiency. The ETC can be used with a concentrator for medium temperature applications, in the range of 140–200 °C. However, the heat extraction rate of the absorber tube is a limitation factor, particularly at higher heat flux and high flow rates. The energy gained is not directly proportional to the concentration factor used. This work thus proposes a counter-flow copper absorber for increasing the heat extraction rate and compares its performance to the conventional direct-flow absorber. The designs are both optimized by varying the absorber diameters, and a material property analysis is done. COMSOL Multiphysics is used for the simulations. The performance of the 2 systems is evaluated using a conjugate heat transfer model at flow rate ranges of 0.02–0.2 kg/s and uniform theoretical heat flux of 1000, 2000, and 3000 W/m2. Analysis of the results indicates that the counter-flow with 0.01 and 0.02 m inner and outer diameter respectively has 4 times more energy gain than the direct-flow with a 0.01 m diameter. Increasing the heat flux by 2 at 0.02 and 0.2 kg/s flow rate increases the temperature by 1.5 and 1.1 for the counter-flow absorber and 1.2 and 1.04 for the direct-flow absorber. Tripling the heat flux at the same flow rate range increases the temperature by 2 and 1.4 for the counter-flow absorber and 1.5 and 1.07 for the direct-flow absorber. The counter-flow absorber is thus the best choice at higher heat flux and high flow rates which are typically required for industrial heating. |
| first_indexed | 2024-04-09T19:23:04Z |
| format | Article |
| id | doaj.art-1a89573779fb4162aab91cade3036dea |
| institution | Directory Open Access Journal |
| issn | 2405-8440 |
| language | English |
| last_indexed | 2024-04-09T19:23:04Z |
| publishDate | 2023-03-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Heliyon |
| spelling | doaj.art-1a89573779fb4162aab91cade3036dea2023-04-05T08:21:27ZengElsevierHeliyon2405-84402023-03-0193e14226Performance analysis of the evacuated tube counter-flow absorber and direct-flow absorber to optimize the heat extraction rate for high flow rate applicationsShaibu Tambula0Downmore Musademba1Chido H. Chihobo2Corresponding author. ;; Department of Fuels and Energy Engineering, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, ZimbabweDepartment of Fuels and Energy Engineering, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, ZimbabweDepartment of Fuels and Energy Engineering, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, ZimbabweThe evacuated tube collector (ETC) has gained extensive use in low-temperature applications due to its cheapness and high efficiency. The ETC can be used with a concentrator for medium temperature applications, in the range of 140–200 °C. However, the heat extraction rate of the absorber tube is a limitation factor, particularly at higher heat flux and high flow rates. The energy gained is not directly proportional to the concentration factor used. This work thus proposes a counter-flow copper absorber for increasing the heat extraction rate and compares its performance to the conventional direct-flow absorber. The designs are both optimized by varying the absorber diameters, and a material property analysis is done. COMSOL Multiphysics is used for the simulations. The performance of the 2 systems is evaluated using a conjugate heat transfer model at flow rate ranges of 0.02–0.2 kg/s and uniform theoretical heat flux of 1000, 2000, and 3000 W/m2. Analysis of the results indicates that the counter-flow with 0.01 and 0.02 m inner and outer diameter respectively has 4 times more energy gain than the direct-flow with a 0.01 m diameter. Increasing the heat flux by 2 at 0.02 and 0.2 kg/s flow rate increases the temperature by 1.5 and 1.1 for the counter-flow absorber and 1.2 and 1.04 for the direct-flow absorber. Tripling the heat flux at the same flow rate range increases the temperature by 2 and 1.4 for the counter-flow absorber and 1.5 and 1.07 for the direct-flow absorber. The counter-flow absorber is thus the best choice at higher heat flux and high flow rates which are typically required for industrial heating.http://www.sciencedirect.com/science/article/pii/S2405844023014330Evacuated tube collectorDirect-flow absorberCounter-flow absorbersHeat extraction rateIndustrial solar heating |
| spellingShingle | Shaibu Tambula Downmore Musademba Chido H. Chihobo Performance analysis of the evacuated tube counter-flow absorber and direct-flow absorber to optimize the heat extraction rate for high flow rate applications Heliyon Evacuated tube collector Direct-flow absorber Counter-flow absorbers Heat extraction rate Industrial solar heating |
| title | Performance analysis of the evacuated tube counter-flow absorber and direct-flow absorber to optimize the heat extraction rate for high flow rate applications |
| title_full | Performance analysis of the evacuated tube counter-flow absorber and direct-flow absorber to optimize the heat extraction rate for high flow rate applications |
| title_fullStr | Performance analysis of the evacuated tube counter-flow absorber and direct-flow absorber to optimize the heat extraction rate for high flow rate applications |
| title_full_unstemmed | Performance analysis of the evacuated tube counter-flow absorber and direct-flow absorber to optimize the heat extraction rate for high flow rate applications |
| title_short | Performance analysis of the evacuated tube counter-flow absorber and direct-flow absorber to optimize the heat extraction rate for high flow rate applications |
| title_sort | performance analysis of the evacuated tube counter flow absorber and direct flow absorber to optimize the heat extraction rate for high flow rate applications |
| topic | Evacuated tube collector Direct-flow absorber Counter-flow absorbers Heat extraction rate Industrial solar heating |
| url | http://www.sciencedirect.com/science/article/pii/S2405844023014330 |
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