Abstract
The purpose of this research is to evaluate the effect of twist in the internal tube in a tube-in-tube helical heat exchanger keeping constant one type of ridges. To meet this goal, a Computational Fluid Dynamic (CFD) model was carried out. The effects of the fluid flow rate on the heat transfer were studied in the internal and annular flow. A commercial CFD package was used to predict the flow and thermal development in a tube-in-tube helical heat exchanger. The simulations were carried out in counter-flow mode operation with hot fluid in the internal tube side and cold fluids in the annular flow. The internal tube was modified with a double passive technique to provide high turbulence in the outer region. The numerical results agree with the reported data, the use of only one passive technique in the internal tube increases the heat transfer up to 28.8% compared to smooth tube.
Highlights
According to Li et al [1], two types of techniques have been proposed to improve the heat transfer of heat exchangers: the active and the passive
The passive technique was widely recommended by several authors because it considers bent tubes and its ability to compact the heat exchanger
The contribution of this research is to provide a Computational Fluid Dynamic (CFD) study of a tube-in-tube helical heat exchanger evaluated with two passive techniques implemented
Summary
According to Li et al [1], two types of techniques have been proposed to improve the heat transfer of heat exchangers: the active and the passive. The active techniques require external power, such as vibration or magnetic fields, whereas the passive techniques require deformations on the tube surface, without external power, as well as on any surface where there is heat transfer. The passive technique was widely recommended by several authors because it considers bent tubes and its ability to compact the heat exchanger. When proposing a combination of passive improvements to improve the heat transfer in a piece of equipment, the problem of knowing the hydrodynamics and temperature profile in the fluid is presented. Passive improvements increase the heat transfer and compact equipment is built. Special interest is put in the effects of the fluid flow rate on the heat transfer while the geometry was changing in the analysis
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