Heat Pipe and Loop Heat Pipe Technologies and Their Applications in Solar Systems

  • Zhangyuan WangEmail author
  • Haopeng Zhang
  • Fucheng Chen
  • Siming Zheng
  • Zicong Huang
  • Xudong Zhao
Part of the Green Energy and Technology book series (GREEN)


Solar energy is considered as the renewable and carbon-neutral energy source of enough scale to replace fossil fuels. The direct utilisation of solar energy can be categorised into two types, i.e. photovoltaic (PV) and solar thermal. However, some disadvantages, e.g. high thermal losses, low conversion rate, still limit the widespread of the solar systems. The solar systems using the heat pipe (HP) and loop heat pipe (LHP) technologies have been developed to tackle the existing problems of the solar system. In this chapter, the working principle and classification of HPs and LHPs for use in the solar system would be comprehensively introduced. The mathematical methods related to the heat transfers limits (i.e. capillary limit, entrainment limit, viscous limit, boiling limit, sonic limit and filled liquid mass limit) and thermal balance (i.e. heat input into the evaporator, heat transportation from the evaporator to the condenser via evaporation and condensation of the heat transfer fluid in the heat pipes, and heat output from the condenser) will be presented. The research works relating the solar systems using heat pipes and loop heat pipes will also be reviewed and analysed from the aspects of characteristic performance, on-site testing, and economic and social assessment. This chapter potentially revealed the further development of HP and/or LHP for use in the solar system.


Heat pipe Loop heat pipe Solar system 


A [m2]




Cp[J/(kg K)]

Specific heat capacity at a constant pressure

Cv[J/(kg K)]

Specific heat capacity at a constant volume



g [m/s2]

Gravitational acceleration

h[W/(m2 K)]

Convective heat transfer coefficient


Latent heat of evaporation



m [kg or kg/s]

Mass or mass flow rate


Mach number



P [Pa]



Pressure drop


Energy flux


Critical radius of bubble generation

R [K/W]

Thermal resistance

Rv[J/(kg K)]

Vapour constant

T [oC]



Factor relating to the filled liquid mass, 0.8 for evaporation and condensation sections and 1 for adiabatic section


Shape factor, 1 for circular and 0.833 for rectangular shapes


Specific heat ratio







λ [W/(m K)]

Thermal conductivity

μ [Pa s]

Dynamic viscosity

ρ [kg/m3]


σ [N/m or W/(m2 K4)]

Surface tension or Stefan Boltzmann constant





Boiling limit




Compensation chamber


Capillary limit




Entrainment limit


Filled liquid mass limit






Liquid film


Liquid line


Sonic limit




Viscous limit




Adiabatic section


Inner surface or heat input


Heat dispersed to the ambient


Minimum values


Outer surface or heat output


Wick in the solid form



This work was financially supported by the National Key R&D Program of China (2016YFE0133300), Guangdong Provincial Key Country Joint Funding Projects, China (2018A050501002) and EU H2020 Research and Innovation Framework Program (734340-DEW-COOL-4-CDC-MSCA-RIS).


  1. 1.
    Ji J, Wang Y, Yuan W, Sun W, He W, Guo C (2014) Experimental comparison of two PV direct-coupled solar water heating systems with the traditional system. Appl Energy 136:110–118CrossRefGoogle Scholar
  2. 2.
    He W, Hong X, Zhao X, Zhang X, Shen J, Ji J (2015) Operational performance of a novel heat pump assisted solar facade loop-heat-pipe water heating system. Appl Energy 146:371–382CrossRefGoogle Scholar
  3. 3.
    Parida B, Iniyan S, Goic R (2011) A review of solar photovoltaic technologies. Renew Sustain Energy Rev 15(3):1625–1636CrossRefGoogle Scholar
  4. 4.
    Singh GK (2013) Solar power generation by PV (photovoltaic) technology: a review. Energy 53:1–13CrossRefGoogle Scholar
  5. 5.
    Thirugnanasambandam M, Iniyan S, Goic R (2010) A review of solar thermal technologies. Renew Sustain Energy Rev 14(1):312–322CrossRefGoogle Scholar
  6. 6.
    Argirious AA, Mirasgedis S (2003) The solar thermal market in Greece—review and perspective. Renew Sustain Energy Rev 7(5):397–418CrossRefGoogle Scholar
  7. 7.
    Elsheikh AH, Sharshir SW, Mostafa ME, Essa FA, Ali MKA (2018) Applications of nanofluids in solar energy: A review of recent advances. Renew Sustain Energy Rev 82:3483–3502CrossRefGoogle Scholar
  8. 8.
    Hsu PC, Huang BJ, Wu PH, Wu WH, Lee MJ, Yeh JF, Lee KY (2017) Long-term energy generation efficiency of solar PV system for self-consumption. Energy Procedia 141:91–95CrossRefGoogle Scholar
  9. 9.
    Yang T, Athienitis AK (2015) Experimental investigation of a two-inlet air-based building integrated photovoltaic/thermal (BIPV/T) system. Appl Energy 159:70–79CrossRefGoogle Scholar
  10. 10.
    Al-Kharabsheh S, Goswami DY (2003) Experimental study of an innovative solar water desalination system utilizing a passive vacuum technique. Sol Energy 75(5):395–401CrossRefGoogle Scholar
  11. 11.
    Zhang X, Song Q, Bai Q, Yang C (2013) Performance analysis on a new type of solar air conditioning system. Energy Build 60:280–285CrossRefGoogle Scholar
  12. 12.
    Kulkarni GN, Kedare SB, Bandyopadhyay S (2009) Optimization of solar water heating systems through water replenishment. Energy Convers Manag 50(3):837–846CrossRefGoogle Scholar
  13. 13.
    Jouhara H, Anastasov V, Khamis I (2009) Potential of heat pipe technology in nuclear seawater desalination. Desalination 249:1055–1061CrossRefGoogle Scholar
  14. 14.
    Jouhara H, Chauhan A, Nannou T, Almahmoud S, Delpech B, Wrobel LC (2017) Heat pipe-based systems-advances and applications. Energy 128:729–754CrossRefGoogle Scholar
  15. 15.
    Mahdavi M, Tiari S, De Schampheleire S, Qiu S (2018) Experimental study of the thermal characteristics of a heat pipe. Exp Thermal Fluid Sci 93:292–304CrossRefGoogle Scholar
  16. 16.
    Behi H, Ghanbarpour M, Behi M (2017) Investigation of PCM-assisted heat pipe for electronic cooling. Appl Therm Eng 127:1132–1142CrossRefGoogle Scholar
  17. 17.
    Kabeel AE, Dawood MMK, Shehata AI (2017) Augmentation of thermal efficiency of the glass evacuated solar tube collector with coaxial heat pipe with different refrigerants and filling ratio. Energy Convers Manag 138:286–298CrossRefGoogle Scholar
  18. 18.
    Liao Z, Faghri A (2016) Thermal analysis of a heat pipe solar central receiver for concentrated solar power tower. Appl Therm Eng 102:952–960CrossRefGoogle Scholar
  19. 19.
    Albanese MV, Robinson BS, Brehob EG, Sharp MK (2012) Simulated and experimental performance of a heat pipe assisted solar wall. Sol Energy 86(5):1552–1562CrossRefGoogle Scholar
  20. 20.
    DunnPD, Reay, DA (1973) The heat pipes. Phys Technol 4:187–201Google Scholar
  21. 21.
    Reay D, Kew P (2006) Heat pipe, 5th edn. Elsevier, London, UKGoogle Scholar
  22. 22.
    Xu X, Wang S, Wang J, Xiao F (2010) Active pipe-embedded structures in buildings for utilizing low-grade energy sources: a review. Energy Build 42:1567–1581CrossRefGoogle Scholar
  23. 23.
    He W, Hong X, Zhao X, Zhang X, Shen J, Ji J (2015) Operational performance of a novel heat pump assisted solar façade loop-heat-pipe water heating system. Appl Energy 146:371–382CrossRefGoogle Scholar
  24. 24.
    Li H, Sun Y (2018) Operational performance study on a photovoltaic loop heat pipe/solar assisted heat pump water heating system. Energy Build 158:861–872CrossRefGoogle Scholar
  25. 25.
    Vasiliev LL (2005) Heat pipes in modern heat exchangers. Appl Therm Eng 25(1):1–19MathSciNetCrossRefGoogle Scholar
  26. 26.
    Maydanik YF (2005) Review: loop heat pipes. Appl Therm Eng 25:635–657CrossRefGoogle Scholar
  27. 27.
    Groll M, Schneider M, Sartre V, Zaghdoudi MC, Lallemand M (1998) Thermal control of electronic equipment by heat pipes. Rev Gen Therm 37:323–352CrossRefGoogle Scholar
  28. 28.
    Sarraf DB, Anderson WG (2007) Heat pipes for high temperature thermal management. In Proceedings of IPACK2007, ASME InterPACK’07, Vancouver, CanadaGoogle Scholar
  29. 29.
    Rosenfeld J (2006) Ultra-lightweight magnesium heat pipes for spacecraft thermal management, Internal Documentation. Thermacore Inc, Lancaster, PennsylvaniaGoogle Scholar
  30. 30.
    Hwang GS, Kaviany M, Anderson WG, Zuo J (2007) Modulated wick heat pipe. Int J Heat Mass Transf 50:1420–1434CrossRefGoogle Scholar
  31. 31.
    Dunn P, Reay DA (1978) Heat pipes. Pergamon Press, OxfordGoogle Scholar
  32. 32.
    Reay D, Kew P (2006) Heat pipes theory, design and applications, 5th edn. Elsevier, London, UKGoogle Scholar
  33. 33.
    Butler D, Ku F, Swanson T (2002) Loop heat pipes and capillary pumped loops—an applications perspective. Space Technol Appl Int Forum 608:49–56Google Scholar
  34. 34.
    Maydanik YF (2005) Loop heat pipes. Appl Therm Eng 25:635–657CrossRefGoogle Scholar
  35. 35.
    Faghri A, Thomas S (1989) Performance characteristics of a concentric annular heat pipe: Part I-experimental prediction and analysis of the capillary limit. J Heat Transfer 111:844–850CrossRefGoogle Scholar
  36. 36.
    Faghri A (1995) Heat pipe science and technology, 1st edn. Taylor & Francis Group, New YorkGoogle Scholar
  37. 37.
    Riffat SB, Zhao X, Doherty PS (2002) Analytical and numerical simulation of the thermal performance of ‘mini’ gravitational and ‘micro’ gravitational heat pipes. Appl Therm Eng 22:1047–1068CrossRefGoogle Scholar
  38. 38.
    Muraoka I, Ramos FM, Vlassov VV (2001) Analysis of the operating characteristics and limits of a loop heat pipe with porous element in the condenser. Int J Heat Mass Transf 44:2287–2297CrossRefGoogle Scholar
  39. 39.
    US Department of Energy (1992) DOE fundamentals handbook: thermodynamics, heat transfer and fluid flow, Volume 2 of 3, DOE-HDBK-1012/2-92, Washington, DC, USGoogle Scholar
  40. 40.
    Riffat SB, Zhao X, Doherty PS (2005) Developing a theoretical model to investigate thermal performance of a thin membrane heat-pipe solar collector. Appl Therm Eng 25:899–915CrossRefGoogle Scholar
  41. 41.
    Chi SW (1976) Heat pipe theory and practice. McGraw-Hill, New York, USGoogle Scholar
  42. 42.
    Pei G, Fu H, Zhang T, Ji J (2011) A numerical and experimental study on a heat pipe PV/T system. Sol Energy 85:911–921CrossRefGoogle Scholar
  43. 43.
    Zhang B, Lv J, Yang H, Ren S (2015) Performance analysis of a heat pipe PV/T system with different circulation tank capacities. Appl Therm Eng 87:89–97CrossRefGoogle Scholar
  44. 44.
    Jouhara H, Milko J, Danielewicz J, Sayegh MA, Szulgowska-Zgrzywa M, Ramos JB, Lester SP (2016) The performance of a novel flat heat pipe based thermal and PV/T (photovoltaic and thermal systems) solar collector that can be used as an energy-active building envelope material. Energy 108:148–154CrossRefGoogle Scholar
  45. 45.
    Wu SY, Zhang Q-L, Xiao L, Guo F-H (2011) A heat pipe photovoltaic/thermal (PV/T) hybrid system and its performance evaluation. Energy Build 43:3558–3567CrossRefGoogle Scholar
  46. 46.
    Zhang L, Wang W, Yu Z (2012) An experimental investigation of a natural circulation heat pipe system applied to a parabolic trough solar collector steam generation system. Sol Energy 86:911–919CrossRefGoogle Scholar
  47. 47.
    Long H, Chow T-T, Ji J (2017) Building-integrated heat pipe photovoltaic/thermal system for use in Hong Kong. Sol Energy 155:1084–1091CrossRefGoogle Scholar
  48. 48.
    Daghigh R, Shafieian A (2016) Theoretical and experimental analysis of thermal performance of a solar water heating system with evacuated tube heat pipe collector. Appl Therm Eng 103:1219–1227CrossRefGoogle Scholar
  49. 49.
    Zhao X, Wang Z, Tang Q (2010) Theoretical investigation of the performance of a novel loop heat pipe solar water heating system for use in Beijing. China. Appl Therm Eng 30(16):2526–2536CrossRefGoogle Scholar
  50. 50.
    Zhang X, Zhao X, Xu J, Yu X (2013) Characterization of a solar photovoltaic/loop-heat-pipe heat pump water heating system. Appl Energy 102:1229–1245CrossRefGoogle Scholar
  51. 51.
    Zhang X, Zhao X, Shen J, Hu X, Liu X, Xu J (2013) Design, fabrication and experimental study of a solar photovoltaic/loop-heat-pipe based heat pump system. Solar Energy 97:551–568CrossRefGoogle Scholar
  52. 52.
    Wang Z, Qiu F, Yang W, Zhao X, Mei S (2016) Experimental investigation of the thermal and electrical performance of the heat pipe BIPV/T system with metal wires. Appl Energy 170:314–323CrossRefGoogle Scholar
  53. 53.
    Wang Z, Yang W (2014) A review on loop heat pipe for use in solar water heating. Energy Build 79:143–154CrossRefGoogle Scholar

Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Zhangyuan Wang
    • 1
    Email author
  • Haopeng Zhang
    • 1
  • Fucheng Chen
    • 1
  • Siming Zheng
    • 1
  • Zicong Huang
    • 1
  • Xudong Zhao
    • 2
  1. 1.School of Civil and Transportation EngineeringGuangdong University of TechnologyGuangzhouChina
  2. 2.School of Engineering and Computer ScienceUniversity of HullHullUK

Personalised recommendations