CFD Modeling of a LNG Microchannel Heat Exchanger

Mahdian, Ehsan | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43648 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Farhadi, Fathollah
  7. Abstract:
  8. In the present work, the possibility of using a cross flow microchannel heat exchanger in cryogenic service for natural gas liquefaction has been numerically investigated using 3D computational fluid dynamics approach. Microchannels of rectangular and triangular cross section with a hydraulic diameter of 0.667 and 0.472 mm respectively have been constructed in Gambit and Fluent is used as the solver of numerical simulations.For solver’s equations validation, the existing experimental data on flow of water through rectangular microchannels has been modeled by CFD. Comparison of CFD results with experimental data shows a good agreement.Both models are constructed of three distinct layers. In the middle layer, methane is cooled with nitrogen as refrigerant, flowing inside upper and lower layers. The flow direction of fluids is in cross flow arrangement. The Reynolds number ranged from 88 to 470 and laminar flow regime governs in all layers.For multiphase flow simulation, Eulerian model joined with Standard k-ε model are applied. Also, saturation condition and interphase mass transfer are predicted using Clausius-Clapeyron and Hertz Knudsen equations defined as a User Defined Function.Simulation results show similar heat transfer performance for both rectangular and triangular microchannels, but triangular model exhibits lower pressure drops. In triangular model, pressure drop per unit length for methane and nitrogen layers is 1301 and 2427 Pa/m respectively. While in rectangular model, this is 785.6 and 1506.8 Pa/m respectively. The heat exchanger’s average overall heat transfer coefficient is 104.3 W/m2.K which is a reasonable value considering heat exchanger low pressure drop and gas-gas service.
  9. Keywords:
  10. Computational Fluid Dynamics (CFD) ; Microchannel Heat Exchanger ; Triangular Microchannel ; Rectangular Microchannel ; Natural Gas Liquefaction ; Cross Flow

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