Experimental Investigation of Heat Transfer and Pressure Drop of Pipes with Internal Roughness

• Author / Creator

  Raoufi, Abdolreza

• In many industrial heat exchangers, it is desirable to improve the rate of heat transfer from a pipe wall to the fluid flow. This improvement is commonly made by adding some form of roughness to the pipe surface. However, the added roughness often leads to an increase in the pressure drop of the flow. The objective of this study is to experimentally compare the rate of heat transfer enhancement and friction factor for fully developed turbulent pipe flows with different roughness elements.
  The experiments were conducted on a smooth pipe and four pipes with different internal roughness elements manufactured using steel mesh and ball bearings. The nominal diameter of all pipes was two inches. The working fluid was air, and the flow properties were measured at Reynolds numbers of 20,000 to 90,000 in increments of 10,000 under a constant pipe wall temperature of 375℃. The Nusselt number and friction factor of the rough pipes were evaluated, and the results were compared to the smooth pipe. It was found that Nusselt number of the pipes with mesh-type roughness increases by approximately 5%, while the Nusselt number of the pipes with roughness elements made from ball-bearings increased by 23 to 33%. The increase of friction factor was 66% for the pipes covered with mesh and 33 to 43% for pipes with ball bearings. The experimental results indicate that adding ball bearings to the internal surface of the pipe can lead to a significant improvement in the rate of heat-transfer. Adding a mesh-type roughness to the pipes can have marginal improvements in heat transfer and a large increase in frictional losses, and therefore it is not recommended.

• Subjects / Keywords

  • Experimental Investigation
  • Heat Transfer
  • Pressure Drop
  • Pipes
  • Roughness
  • Friction factor
  • Thermohydraulic performance
  • Nusselt

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-dmg7-1v48

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.