Thermosyphon heat-pipe evacuated tube solar water heaters for northern maritime climates

David A.G. Redpath

    Research output: Contribution to journalArticle

    28 Citations (Scopus)

    Abstract

    Under transient climatic conditions previous research has reported that evacuated tube solar water heaters (ETSWHs) with heat-pipe absorbers are the most effective solution for collection of solar energy. The cost of such systems is greater than the mass produced “water in glass” evacuated tube solar water heater mainly manufactured in China. Previous studies have reported that the costs of solar water heating can be reduced through the adoption of thermosyphon fluid circulation. Well designed thermosyphon systems are as effective as pumped systems but with lower capital and running costs. To investigate if costs could be reduced and performance levels maintained, outdoor testing of three thermosyphon heat-pipe ETSWHs primarily designed for pumped fluid circulation was carried out under a northern maritime climate. Experimental data from a year’s side by side monitoring of two thermosyphon ETSWHs (both with the same area of 2 m2) was collected and used to validate a correlation based on a modified version of the f-chart design tool between the observed and expected performance for both systems. The R2 value between measured and predicted monthly solar fractions was greater than 0.99 for both systems. The R2 value between measured and predicted diurnal solar fractions was calculated as greater than 0.95 for both systems. The only difference between the two was that one utilised internal heat-pipe condensers whilst the other used external ones. The system with internal condensers was found to be 17% more efficient. A simplifying assumption of a constant temperature rise across the collectors reduced the calculations required to predict the performance of thermosyphon heat-pipe ETSWHs and was also statistically significant. To determine if the assumption was valid for other thermosyphon heat-pipe ETSWHs with different collector parameters a third system with internal condensers an area of 3 m2, a heat removal factor (FR) of 0.816 based on the absorber area and a collector loss coefficient (FRUL) of 2.25 W m−2 K−1 was assembled and its performance monitored, when the same assumption was applied the R2 value between the measured and predicted daily solar fractions was calculated as 0.96 experimentally demonstrating that this relationship was still statistically significant for another heat-pipe thermosyphon ETSWH with different collector parameters.
    LanguageEnglish
    Pages705-715
    JournalSolar Energy
    Volume86
    Issue number2
    DOIs
    Publication statusPublished - Feb 2012

    Fingerprint

    Solar water heaters
    Thermosyphons
    Tubes (components)
    Heat pipes
    Costs
    Condensers (liquefiers)
    Fluids
    Solar energy
    Heating
    Glass
    Water
    Monitoring
    Testing

    Keywords

    • Modified f-chart
    • Thermosyphon design tools
    • Heat-pipe solar collectors
    • Northern maritime climates

    Cite this

    @article{1d9dc849b4d84a6d9a621083f9a8e8df,
    title = "Thermosyphon heat-pipe evacuated tube solar water heaters for northern maritime climates",
    abstract = "Under transient climatic conditions previous research has reported that evacuated tube solar water heaters (ETSWHs) with heat-pipe absorbers are the most effective solution for collection of solar energy. The cost of such systems is greater than the mass produced “water in glass” evacuated tube solar water heater mainly manufactured in China. Previous studies have reported that the costs of solar water heating can be reduced through the adoption of thermosyphon fluid circulation. Well designed thermosyphon systems are as effective as pumped systems but with lower capital and running costs. To investigate if costs could be reduced and performance levels maintained, outdoor testing of three thermosyphon heat-pipe ETSWHs primarily designed for pumped fluid circulation was carried out under a northern maritime climate. Experimental data from a year’s side by side monitoring of two thermosyphon ETSWHs (both with the same area of 2 m2) was collected and used to validate a correlation based on a modified version of the f-chart design tool between the observed and expected performance for both systems. The R2 value between measured and predicted monthly solar fractions was greater than 0.99 for both systems. The R2 value between measured and predicted diurnal solar fractions was calculated as greater than 0.95 for both systems. The only difference between the two was that one utilised internal heat-pipe condensers whilst the other used external ones. The system with internal condensers was found to be 17{\%} more efficient. A simplifying assumption of a constant temperature rise across the collectors reduced the calculations required to predict the performance of thermosyphon heat-pipe ETSWHs and was also statistically significant. To determine if the assumption was valid for other thermosyphon heat-pipe ETSWHs with different collector parameters a third system with internal condensers an area of 3 m2, a heat removal factor (FR) of 0.816 based on the absorber area and a collector loss coefficient (FRUL) of 2.25 W m−2 K−1 was assembled and its performance monitored, when the same assumption was applied the R2 value between the measured and predicted daily solar fractions was calculated as 0.96 experimentally demonstrating that this relationship was still statistically significant for another heat-pipe thermosyphon ETSWH with different collector parameters.",
    keywords = "Modified f-chart, Thermosyphon design tools, Heat-pipe solar collectors, Northern maritime climates",
    author = "Redpath, {David A.G.}",
    note = "Reference text: Beckman et al., 1977 W.A. Beckman, S.A. Klein and J.A. Duffie, Solar Heating Design by the f-chart method, John Wiley & Sons Inc., USA (1977). Budihardjo et al., 2007 I. Budihardjo, G.L. Morrison and M. Behnia, Natural circulation flow through water-in-glass evacuated tube solar collectors. Solar Energy, 81 (2007), pp. 1460–1472. Article | PDF (1618 K) | | View Record in Scopus | | Cited By in Scopus (8) Budihardjo and Morrison, 2009 I. Budihardjo and G.L. Morrison, Performance of water-in-glass evacuated tube solar water heaters. Solar Energy, 83 (2009), pp. 49–56. Article | PDF (467 K) | | View Record in Scopus | | Cited By in Scopus (10) Budihardjo et al., 2002 Budihardjo, I., Morrison, G., Behnia, M., 2002, Performance of a water-in-glass evacuated solar water heater. In: Proceedings of Australian New Zealand Solar Energy Society, Newcastle, Australia.. Close, 1962 D.J. Close, Performance of solar water heaters. Solar Energy, 6 (1962), pp. 33–40. Article | PDF (667 K) | | View Record in Scopus | | Cited By in Scopus (34) DGS, 2005 DGS, 2005, Planning and Installing Solar Thermal Systems: A Guide for Installers, Architects. The German Solar Energy Society, James and James, London, UK.. DeVries et al., 1980 H. DeVries, W. Kamminga and J. Francken, Fluid circulation control in conventional and heat pipe planar solar collectors. Solar Energy, 24 (1980), pp. 209–213. Article | PDF (327 K) | | View Record in Scopus | | Cited By in Scopus (11) Duffie and Beckman, 2006 J. Duffie and W. Beckman, Solar engineering of thermal processes, (third ed.), John Wiley and Sons, New Jersey, USA (2006). Energy Saving Trust, 2011 Energy Saving Trust, 2011. <http://www.energysavingtrust.org.uk/Generate-your-own-energy/Solar-water-heating> (accessed 01.03.11).. Evans et al., 1982 D.L. Evans, T.T. Rule and B.D. Wood, A new look at long term collector performance and utilizability. Solar Energy, 28 (1982), pp. 13–23. Article | PDF (1003 K) | | View Record in Scopus | | Cited By in Scopus (3) Fanney and Klein, 1983 A.H. Fanney and S.A. Klein, Performance of solar domestic hot water systems at the national bureau of standards-measurements and predictions. Journal of Solar Energy Engineering, 105 (1983), pp. 311–322. Full Text via CrossRef Garcia-Valladares et al., 2008 O. Garcia-Valladares, I. Pilatowsky and V. Ruiz, Outdoor test method to determine the thermal behaviour of solar domestic water heating. Solar Energy, 82 (2008), pp. 613–622. Article | PDF (864 K) | | View Record in Scopus | | Cited By in Scopus (4) Hull, 1987 J.R. Hull, Comparison of heat transfer in solar collectors with heat pipe versus flow through absorbers. Journal of Solar Energy Engineering, 109 (1987), pp. 253–258. | View Record in Scopus | | Full Text via CrossRef | Cited By in Scopus (12) Japikse, 1973 D. Japikse, Advances in thermosyphon technology. Advances in Heat Transfer, 9 (1973), pp. 1–111. Article | PDF (5830 K) | | View Record in Scopus | | Cited By in Scopus (27) Jaluria, 1980 Y. Jaluria, Natural Convection Heat and Mass Transfer, Pergamon Press, UK (1980). Kalogirou, 2004 Kalogirou, Solar thermal collectors and applications. Progress in Energy and Combustion Science, 30 (2004), pp. 231–295. Article | PDF (944 K) | | View Record in Scopus | | Cited By in Scopus (203) Klein et al., 1976 S.A. Klein, W.A. Beckman and J.A. Duffie, A design procedure for solar heating systems. Solar Energy, 18 (1976), pp. 113–127. Article | PDF (1262 K) | | View Record in Scopus | | Cited By in Scopus (46) Malkin et al., 1987 M.P. Malkin, S.A. Klein, J.A. Duffie and A.B. Copsey, A design method for thermosyphon solar domestic hot water systems. Journal of Solar Energy Engineering, 109 (1987), pp. 150–155. | View Record in Scopus | | Full Text via CrossRef | Cited By in Scopus (2) Morrison and Braun, 1985 G.L. Morrison and J. Braun, System modelling and operation characteristics of thermosyphon solar water heaters. Solar Energy, 34 (1985), pp. 389–405. Article | PDF (1093 K) | | View Record in Scopus | | Cited By in Scopus (33) Morrison et al., 2004 G. Morrison, I. Budihardjo and M. Behnia, Water-in-glass evacuated tube solar water heaters. Solar Energy, 76 (2004), pp. 135–140. Article | PDF (417 K) | | View Record in Scopus | | Cited By in Scopus (31) Morrison et al., 2005 G. Morrison, I. Budihardjo and M. Behnia, Measurement and simulation of flow rate in a water-in-glass evacuated tube solar water heaters. Solar Energy, 78 (2005), pp. 257–267. Article | PDF (650 K) | | View Record in Scopus | | Cited By in Scopus (25) Morrison and Sapsford, 1983 Morrison and Sapsford, Long term performance of thermosyphon solar water heaters. Solar Energy, 30 (1983), pp. 341–350. Article | PDF (661 K) | | View Record in Scopus | | Cited By in Scopus (8) NASA, 2000 NASA, 2000, NASA Surface Meteorology and Solar Energy Data Set. <http://www.retscreen.net/> (accessed 20.02.11).. Norton et al., 1987 B. Norton, S.D. Probert and J.T. Gidney, Diurnal performance of thermosyphonic solar water heaters-an empirical prediction method. Solar Energy, 39 (1987), pp. 257–265. Article | PDF (560 K) | | View Record in Scopus | | Cited By in Scopus (9) Norton et al., 2001 B. Norton, P.C. Eames and S.N.G. Lo, Alternative approaches to thermosyphon solar energy water heater performance analysis and characterisation. Renewable and Sustainable Energy Reviews, 5 (2001), pp. 79–96. Article | PDF (285 K) | | View Record in Scopus | | Cited By in Scopus (6) Ortabasi and Fehlner, 1980 U. Ortabasi and F.P. Fehlner, Cusp mirror heat-pipe evacuated tubular solar thermal collector. Solar Energy, 24 (1980), pp. 477–489. Article | PDF (991 K) | | View Record in Scopus | | Cited By in Scopus (10) Redpath et al., 2009 D.A.G. Redpath, P.C. Eames, S.N.G. Lo and P.W. Griffiths, Experimental investigation of natural convection heat exchange within a physical model of the manifold chamber of a thermosyphon heat-pipe evacuated tube solar water heater. Solar Energy, (2009), p. 11. | View Record in Scopus | Redpath et al., 2010 D.A.G. Redpath, S.N.G. Lo and P.C. Eames, Experimental investigation and optimisation study of a direct thermosyphon heat-pipe evacuated tube solar water heater subjected to a northern maritime climate. International Journal of Ambient Energy, 31 2 (2010), pp. 91–101. RETscreen, 2011 RETscreen Software, 2011. <http://www.retscreen.net> (accessed 10.02.11).. Singh et al., 2007 Singh, H., Eames, P.C., Peacock, A., 2007. Reducing the carbon footprint of existing UK dwellings-case studies. In: Proceedings Heat-set, Chambery, France.. SPF, 2003a SPF, 2003a, Solar Collector Factsheet Thermomax Mazdon 20-TMA600S. <http://www.solarenergy.ch/fileadmin/daten/reportInterface/kollektoren/factsheets/scf601en.pdf> (accessed 10.02.11).. SPF, 2003b SPF, 2003b, Solar Collector Factsheet Thermomax MS 20-TMO500S. <http://www.solarenergy.ch/fileadmin/daten/reportInterface/kollektoren/factsheets/scf601en.pdf> (accessed 10.02.11).. SPF, 2005 SPF, 2005, Solar Collector Factsheet Thermomax MS30-TMO500. <http://www.solarenergy.ch/fileadmin/daten/reportInterface/kollektoren/factsheets/scf601en.pdf> (accessed 10.02.11)..",
    year = "2012",
    month = "2",
    doi = "10.1016/j.solener.2011.11.015",
    language = "English",
    volume = "86",
    pages = "705--715",
    journal = "Solar Energy",
    issn = "0038-092X",
    publisher = "Elsevier",
    number = "2",

    }

    Thermosyphon heat-pipe evacuated tube solar water heaters for northern maritime climates. / Redpath, David A.G.

    In: Solar Energy, Vol. 86, No. 2, 02.2012, p. 705-715.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Thermosyphon heat-pipe evacuated tube solar water heaters for northern maritime climates

    AU - Redpath, David A.G.

    N1 - Reference text: Beckman et al., 1977 W.A. Beckman, S.A. Klein and J.A. Duffie, Solar Heating Design by the f-chart method, John Wiley & Sons Inc., USA (1977). Budihardjo et al., 2007 I. Budihardjo, G.L. Morrison and M. Behnia, Natural circulation flow through water-in-glass evacuated tube solar collectors. Solar Energy, 81 (2007), pp. 1460–1472. Article | PDF (1618 K) | | View Record in Scopus | | Cited By in Scopus (8) Budihardjo and Morrison, 2009 I. Budihardjo and G.L. Morrison, Performance of water-in-glass evacuated tube solar water heaters. Solar Energy, 83 (2009), pp. 49–56. Article | PDF (467 K) | | View Record in Scopus | | Cited By in Scopus (10) Budihardjo et al., 2002 Budihardjo, I., Morrison, G., Behnia, M., 2002, Performance of a water-in-glass evacuated solar water heater. In: Proceedings of Australian New Zealand Solar Energy Society, Newcastle, Australia.. Close, 1962 D.J. Close, Performance of solar water heaters. Solar Energy, 6 (1962), pp. 33–40. Article | PDF (667 K) | | View Record in Scopus | | Cited By in Scopus (34) DGS, 2005 DGS, 2005, Planning and Installing Solar Thermal Systems: A Guide for Installers, Architects. The German Solar Energy Society, James and James, London, UK.. DeVries et al., 1980 H. DeVries, W. Kamminga and J. Francken, Fluid circulation control in conventional and heat pipe planar solar collectors. Solar Energy, 24 (1980), pp. 209–213. Article | PDF (327 K) | | View Record in Scopus | | Cited By in Scopus (11) Duffie and Beckman, 2006 J. Duffie and W. Beckman, Solar engineering of thermal processes, (third ed.), John Wiley and Sons, New Jersey, USA (2006). Energy Saving Trust, 2011 Energy Saving Trust, 2011. <http://www.energysavingtrust.org.uk/Generate-your-own-energy/Solar-water-heating> (accessed 01.03.11).. Evans et al., 1982 D.L. Evans, T.T. Rule and B.D. Wood, A new look at long term collector performance and utilizability. Solar Energy, 28 (1982), pp. 13–23. Article | PDF (1003 K) | | View Record in Scopus | | Cited By in Scopus (3) Fanney and Klein, 1983 A.H. Fanney and S.A. Klein, Performance of solar domestic hot water systems at the national bureau of standards-measurements and predictions. Journal of Solar Energy Engineering, 105 (1983), pp. 311–322. Full Text via CrossRef Garcia-Valladares et al., 2008 O. Garcia-Valladares, I. Pilatowsky and V. Ruiz, Outdoor test method to determine the thermal behaviour of solar domestic water heating. Solar Energy, 82 (2008), pp. 613–622. Article | PDF (864 K) | | View Record in Scopus | | Cited By in Scopus (4) Hull, 1987 J.R. Hull, Comparison of heat transfer in solar collectors with heat pipe versus flow through absorbers. Journal of Solar Energy Engineering, 109 (1987), pp. 253–258. | View Record in Scopus | | Full Text via CrossRef | Cited By in Scopus (12) Japikse, 1973 D. Japikse, Advances in thermosyphon technology. Advances in Heat Transfer, 9 (1973), pp. 1–111. Article | PDF (5830 K) | | View Record in Scopus | | Cited By in Scopus (27) Jaluria, 1980 Y. Jaluria, Natural Convection Heat and Mass Transfer, Pergamon Press, UK (1980). Kalogirou, 2004 Kalogirou, Solar thermal collectors and applications. Progress in Energy and Combustion Science, 30 (2004), pp. 231–295. Article | PDF (944 K) | | View Record in Scopus | | Cited By in Scopus (203) Klein et al., 1976 S.A. Klein, W.A. Beckman and J.A. Duffie, A design procedure for solar heating systems. Solar Energy, 18 (1976), pp. 113–127. Article | PDF (1262 K) | | View Record in Scopus | | Cited By in Scopus (46) Malkin et al., 1987 M.P. Malkin, S.A. Klein, J.A. Duffie and A.B. Copsey, A design method for thermosyphon solar domestic hot water systems. Journal of Solar Energy Engineering, 109 (1987), pp. 150–155. | View Record in Scopus | | Full Text via CrossRef | Cited By in Scopus (2) Morrison and Braun, 1985 G.L. Morrison and J. Braun, System modelling and operation characteristics of thermosyphon solar water heaters. Solar Energy, 34 (1985), pp. 389–405. Article | PDF (1093 K) | | View Record in Scopus | | Cited By in Scopus (33) Morrison et al., 2004 G. Morrison, I. Budihardjo and M. Behnia, Water-in-glass evacuated tube solar water heaters. Solar Energy, 76 (2004), pp. 135–140. Article | PDF (417 K) | | View Record in Scopus | | Cited By in Scopus (31) Morrison et al., 2005 G. Morrison, I. Budihardjo and M. Behnia, Measurement and simulation of flow rate in a water-in-glass evacuated tube solar water heaters. Solar Energy, 78 (2005), pp. 257–267. Article | PDF (650 K) | | View Record in Scopus | | Cited By in Scopus (25) Morrison and Sapsford, 1983 Morrison and Sapsford, Long term performance of thermosyphon solar water heaters. Solar Energy, 30 (1983), pp. 341–350. Article | PDF (661 K) | | View Record in Scopus | | Cited By in Scopus (8) NASA, 2000 NASA, 2000, NASA Surface Meteorology and Solar Energy Data Set. <http://www.retscreen.net/> (accessed 20.02.11).. Norton et al., 1987 B. Norton, S.D. Probert and J.T. Gidney, Diurnal performance of thermosyphonic solar water heaters-an empirical prediction method. Solar Energy, 39 (1987), pp. 257–265. Article | PDF (560 K) | | View Record in Scopus | | Cited By in Scopus (9) Norton et al., 2001 B. Norton, P.C. Eames and S.N.G. Lo, Alternative approaches to thermosyphon solar energy water heater performance analysis and characterisation. Renewable and Sustainable Energy Reviews, 5 (2001), pp. 79–96. Article | PDF (285 K) | | View Record in Scopus | | Cited By in Scopus (6) Ortabasi and Fehlner, 1980 U. Ortabasi and F.P. Fehlner, Cusp mirror heat-pipe evacuated tubular solar thermal collector. Solar Energy, 24 (1980), pp. 477–489. Article | PDF (991 K) | | View Record in Scopus | | Cited By in Scopus (10) Redpath et al., 2009 D.A.G. Redpath, P.C. Eames, S.N.G. Lo and P.W. Griffiths, Experimental investigation of natural convection heat exchange within a physical model of the manifold chamber of a thermosyphon heat-pipe evacuated tube solar water heater. Solar Energy, (2009), p. 11. | View Record in Scopus | Redpath et al., 2010 D.A.G. Redpath, S.N.G. Lo and P.C. Eames, Experimental investigation and optimisation study of a direct thermosyphon heat-pipe evacuated tube solar water heater subjected to a northern maritime climate. International Journal of Ambient Energy, 31 2 (2010), pp. 91–101. RETscreen, 2011 RETscreen Software, 2011. <http://www.retscreen.net> (accessed 10.02.11).. Singh et al., 2007 Singh, H., Eames, P.C., Peacock, A., 2007. Reducing the carbon footprint of existing UK dwellings-case studies. In: Proceedings Heat-set, Chambery, France.. SPF, 2003a SPF, 2003a, Solar Collector Factsheet Thermomax Mazdon 20-TMA600S. <http://www.solarenergy.ch/fileadmin/daten/reportInterface/kollektoren/factsheets/scf601en.pdf> (accessed 10.02.11).. SPF, 2003b SPF, 2003b, Solar Collector Factsheet Thermomax MS 20-TMO500S. <http://www.solarenergy.ch/fileadmin/daten/reportInterface/kollektoren/factsheets/scf601en.pdf> (accessed 10.02.11).. SPF, 2005 SPF, 2005, Solar Collector Factsheet Thermomax MS30-TMO500. <http://www.solarenergy.ch/fileadmin/daten/reportInterface/kollektoren/factsheets/scf601en.pdf> (accessed 10.02.11)..

    PY - 2012/2

    Y1 - 2012/2

    N2 - Under transient climatic conditions previous research has reported that evacuated tube solar water heaters (ETSWHs) with heat-pipe absorbers are the most effective solution for collection of solar energy. The cost of such systems is greater than the mass produced “water in glass” evacuated tube solar water heater mainly manufactured in China. Previous studies have reported that the costs of solar water heating can be reduced through the adoption of thermosyphon fluid circulation. Well designed thermosyphon systems are as effective as pumped systems but with lower capital and running costs. To investigate if costs could be reduced and performance levels maintained, outdoor testing of three thermosyphon heat-pipe ETSWHs primarily designed for pumped fluid circulation was carried out under a northern maritime climate. Experimental data from a year’s side by side monitoring of two thermosyphon ETSWHs (both with the same area of 2 m2) was collected and used to validate a correlation based on a modified version of the f-chart design tool between the observed and expected performance for both systems. The R2 value between measured and predicted monthly solar fractions was greater than 0.99 for both systems. The R2 value between measured and predicted diurnal solar fractions was calculated as greater than 0.95 for both systems. The only difference between the two was that one utilised internal heat-pipe condensers whilst the other used external ones. The system with internal condensers was found to be 17% more efficient. A simplifying assumption of a constant temperature rise across the collectors reduced the calculations required to predict the performance of thermosyphon heat-pipe ETSWHs and was also statistically significant. To determine if the assumption was valid for other thermosyphon heat-pipe ETSWHs with different collector parameters a third system with internal condensers an area of 3 m2, a heat removal factor (FR) of 0.816 based on the absorber area and a collector loss coefficient (FRUL) of 2.25 W m−2 K−1 was assembled and its performance monitored, when the same assumption was applied the R2 value between the measured and predicted daily solar fractions was calculated as 0.96 experimentally demonstrating that this relationship was still statistically significant for another heat-pipe thermosyphon ETSWH with different collector parameters.

    AB - Under transient climatic conditions previous research has reported that evacuated tube solar water heaters (ETSWHs) with heat-pipe absorbers are the most effective solution for collection of solar energy. The cost of such systems is greater than the mass produced “water in glass” evacuated tube solar water heater mainly manufactured in China. Previous studies have reported that the costs of solar water heating can be reduced through the adoption of thermosyphon fluid circulation. Well designed thermosyphon systems are as effective as pumped systems but with lower capital and running costs. To investigate if costs could be reduced and performance levels maintained, outdoor testing of three thermosyphon heat-pipe ETSWHs primarily designed for pumped fluid circulation was carried out under a northern maritime climate. Experimental data from a year’s side by side monitoring of two thermosyphon ETSWHs (both with the same area of 2 m2) was collected and used to validate a correlation based on a modified version of the f-chart design tool between the observed and expected performance for both systems. The R2 value between measured and predicted monthly solar fractions was greater than 0.99 for both systems. The R2 value between measured and predicted diurnal solar fractions was calculated as greater than 0.95 for both systems. The only difference between the two was that one utilised internal heat-pipe condensers whilst the other used external ones. The system with internal condensers was found to be 17% more efficient. A simplifying assumption of a constant temperature rise across the collectors reduced the calculations required to predict the performance of thermosyphon heat-pipe ETSWHs and was also statistically significant. To determine if the assumption was valid for other thermosyphon heat-pipe ETSWHs with different collector parameters a third system with internal condensers an area of 3 m2, a heat removal factor (FR) of 0.816 based on the absorber area and a collector loss coefficient (FRUL) of 2.25 W m−2 K−1 was assembled and its performance monitored, when the same assumption was applied the R2 value between the measured and predicted daily solar fractions was calculated as 0.96 experimentally demonstrating that this relationship was still statistically significant for another heat-pipe thermosyphon ETSWH with different collector parameters.

    KW - Modified f-chart

    KW - Thermosyphon design tools

    KW - Heat-pipe solar collectors

    KW - Northern maritime climates

    U2 - 10.1016/j.solener.2011.11.015

    DO - 10.1016/j.solener.2011.11.015

    M3 - Article

    VL - 86

    SP - 705

    EP - 715

    JO - Solar Energy

    T2 - Solar Energy

    JF - Solar Energy

    SN - 0038-092X

    IS - 2

    ER -