Numerical study on flow, heat transfer and entropy generation of supercritical co2 in a heated helical coiled tube

EasyChair Preprint 4772

Abstract

Supercritical carbon dioxide (sCO2) helically coiled gas heaters have received particular interest during the last years due to their compact structure and the preeminent thermal and flow properties of sCO2. Thermophysical properties of sCO2 such as the specific heat capacity, density, viscosity and thermal conductivity undergo significant variations. Previous studies on this topic focused only on the flow and heat transfer characteristics which are not sufficient to quantify real irreversibilities and to provide method to reduce them. This kind of information can be only obtained using the entropy generation analysis method which is a considered as a reliable tool to design and optimize thermal equipments. Indeed, the large temperature difference between the fluid and the hot walls makes the heat transfer process deviating from thermodynamic reversibility, resulting in high entropy generation and poor exergy efficiency. Entropy generation analysis, a second law based method, allows to locate the sources of flow and heat transfer irreversibilities and their magnitude. The reduction of these irreversibilities yields to effective heat transfer process and efficient use of available energy. The present paper aims to numerically investigate the flow, heat transfer and entropy generation of sCO2 in a heated helical coiled tube having an inner diameter of 9.0 mm, a length of 5500 mm and 6 turns of coils with a pitch distance of 32 mm. Computations have been carried out using SST k-ω turbulence model and considering sCO2 as a real gas. Two inlet boundary conditions, mass flow rate inlet and pressure inlet, have been tested with various wall heat flux values. Results, in terms of pressure drop and Nusselt number, showed good agreement with experimental measurements from the literature. Furthermore, results obtained provide detailed flow, heat transfer and irreversibilities information for further design and optimization of sCO2 equipment for industrial applications.

Keyphrases: Entropy generation, Supercritical CO2, heat transfer, helical tube

@booklet{EasyChair:4772,
  author    = {Mohammed Baghdad and Ahmed Ouadha},
  title     = {Numerical study on flow, heat transfer and entropy generation of supercritical co2 in a heated helical coiled tube},
  howpublished = {EasyChair Preprint 4772},
  year      = {EasyChair, 2020}}