Numerical study on the effects of extended surfaces on the performance of a coaxial geothermal heat exchanger

Document Type : Mechanics article

Authors

1 Department of Energy, Faculty of New Sciences and Technologies, Semnan University, Semnan, Iran

2 Faculty of Mechanical Engineering, Semnan University, Semnan, Iran

Abstract

In this study, the effect of expanded surfaces on the performance of a vertical coaxial geothermal heat exchanger has been investigated. The fluid (water) with an initial temperature of 3.5 ºC and a volumetric flow rate of 0.0008 m3/s enters from the annular area and exits from the middle pipe. The simulation is done for the heat absorption mode. The SST k-ω turbulence model is used for simulation of the turbulent flow. The thermal performance of the heat exchanger has been improved by placing ribs and dimples with several different geometries on the surface of the outer tube. Triangular surfaces showed better temperature output than other geometries. The temperature difference between the inlet and outlet of the fluid in the heat exchanger with a dimple and a triangular rib with a dimple depth of 5 mm has increased by 6.5%. The highest pressure drop is related to the heat exchanger with a dimple and a triangular tooth with a dimple depth of 5 mm, the value of which is 10.9 kPa. Different values of the local Nusselt number in the annular region of the heat exchanger have been calculated for different depths. The simple heat exchanger has the highest average Nusselt number in the studied range, and the average Nusselt number for this type of heat exchanger is 57.15.

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References

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Journal of Modeling in Engineering
Volume 22, Issue 76
May 2024
Pages 167-175

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History

  • Receive Date: 07 April 2023
  • Revise Date: 13 July 2023
  • Accept Date: 26 August 2023

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