Consideration of Double Discrete Inclined Ribs in Low Curvature Coil for GSHP System

Abstract

This article presents an investigation of a low curvature coiled tube with double discrete inclined ribs for an application to ground heat exchanger used in ground heat pump systems. Computational fluid dynamics is employed to analyze the heat transfer and fluid flow with several ribs. The analysis performs detailed study involving flow behavior, pressure drop, heat transfer rate, wall heat flux, absolute vorticity flux for a range of ribs height (0.45 mm, 0.75 mm, and 1 mm) and flowrate (ranging from 6 L/min to 10 L/min) on curvature of coil 2.22 m^-1. COP improvement factor, which is a function of heat transfer enhancement and pressure loss increase, is evaluated. The increasing of ribs height can deviate secondary flow, which contributes to heat transfer and pressure drop enhancement. In the case of higher ribs, circumferential heat flux distribution tends to be more fluctuated. The heat flux distribution also becomes smaller with the increasing of axial distance. The COP improvement factor significantly improves with the increase of ribs height. On the other hand, the COP Improvement factor tends to decrease with the increase in flow rate. The application of ribs in a low curvature coil is attractive and has the potential for Slinky-coil ground heat exchangers.