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Evaluation of heat transfer correlations for helical coils based on measurements of a solar ORC operating at subcritical conditions

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Abstract
Organic Rankine cycle (ORC) is an acknowledged method for utilizing low temperature heat sources for generating electricity. Among many applications at heat sources such as internal combustion engines and industrial facilities, solar power is a significant energy source. For solar boilers, helical coil heat exchangers are widely used. The design of these heat exchangers are made with conventional methods, which are mostly not validated for ORC conditions, namely larger tube diameters and working fluids. In order to analyse the accuracy of conventional helical coil heat transfer correlations in design, the geometry and performed measurements at subcritical conditions of a helical coil heat exchanger is taken as reference for the off-design. The helical coil is electrically heated for simulating the photovoltaic/thermal (PV/T) collectors, for testing the solar ORC concept. Then the ORC is coupled with the PV/T collectors on the field for the complete solar ORC system. The inlet conditions of the existing installation are used for sizing and rating via 9 two-phase heat transfer correlations existing in the literature for the tube-side of helical coil. The helical coil outer diameter is 33,7 mm, whereas the shell inner and outer diameter are 0,526 m and 0,674 m, respectively. The coil diameter is 0,6 m. Three measurements are made at changing ORC medium (R404a) mass flow rates, namely 0,1 kg/s, 0,17 kg/s and 0,24 kg/s. R404a's inlet temperature changes between 21,9 °C and 33,6 °C at a pressure range of 17,5 - 31,6 bars (representing the saturation temperature). In all three cases, the heating water inlet conditions are fixed at an inlet temperature of 95,3 °C and a mass flow rate of 2,67 kg/s.
Keywords
Organic Rankine Cycles, Helical Coil Heat Exchangers, Heat Transfer

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Chicago
Kaya, Alihan, Marija Lazova, George Kosmadakis, and Michel De Paepe. 2016. “Evaluation of Heat Transfer Correlations for Helical Coils Based on Measurements of a Solar ORC Operating at Subcritical Conditions.” In 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, 955–960.
APA
Kaya, Alihan, Lazova, M., Kosmadakis, G., & De Paepe, M. (2016). Evaluation of heat transfer correlations for helical coils based on measurements of a solar ORC operating at subcritical conditions. 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics (pp. 955–960). Presented at the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics.
Vancouver
1.
Kaya A, Lazova M, Kosmadakis G, De Paepe M. Evaluation of heat transfer correlations for helical coils based on measurements of a solar ORC operating at subcritical conditions. 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics. 2016. p. 955–60.
MLA
Kaya, Alihan, Marija Lazova, George Kosmadakis, et al. “Evaluation of Heat Transfer Correlations for Helical Coils Based on Measurements of a Solar ORC Operating at Subcritical Conditions.” 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics. 2016. 955–960. Print.
@inproceedings{8058877,
  abstract     = {Organic Rankine cycle (ORC) is an acknowledged method for utilizing low temperature heat sources for generating electricity. Among many applications at heat sources such as internal combustion engines and industrial facilities, solar power is a significant energy source. For solar boilers, helical coil heat exchangers are widely used. The design of these heat exchangers are made with conventional methods, which are mostly not validated for ORC conditions, namely larger tube diameters and working fluids. In order to analyse the accuracy of conventional helical coil heat transfer correlations in design, the geometry and performed measurements at subcritical conditions of a helical coil heat exchanger is taken as reference for the off-design. The helical coil is electrically heated for simulating the photovoltaic/thermal (PV/T) collectors, for testing the solar ORC concept. Then the ORC is coupled with the PV/T collectors on the field for the complete solar ORC system. The inlet conditions of the existing installation are used for sizing and rating via 9 two-phase heat transfer correlations existing in the literature for the tube-side of helical coil. The helical coil outer diameter is 33,7 mm, whereas the shell inner and outer diameter are 0,526 m and 0,674 m, respectively. The coil diameter is 0,6 m. Three measurements are made at changing ORC medium (R404a) mass flow rates, namely 0,1 kg/s, 0,17 kg/s and 0,24 kg/s. R404a's inlet temperature changes between 21,9 {\textdegree}C and 33,6 {\textdegree}C at a pressure range of 17,5 - 31,6 bars (representing the saturation temperature). In all three cases, the heating water inlet conditions are fixed at an inlet temperature of 95,3 {\textdegree}C and a mass flow rate of 2,67 kg/s.},
  author       = {Kaya, Alihan and Lazova, Marija and Kosmadakis, George and De Paepe, Michel},
  booktitle    = {12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics},
  isbn         = { 978-1-77592-124-0},
  keyword      = {Organic Rankine Cycles,Helical Coil Heat Exchangers,Heat Transfer},
  language     = {eng},
  location     = {Costa Del Sol, Spain},
  pages        = {955--960},
  title        = {Evaluation of heat transfer correlations for helical coils based on measurements of a solar ORC operating at subcritical conditions},
  year         = {2016},
}