Search

This numerical investigation aims to study the turbulent characteristics and thermal enhancement parameter of CuO–water nanofluids through heat exchangers enhanced with double V-cut twisted tapes. The twist ratio of the twisted tapes is 5.25, and the cut ratio (b/c) is varied from 0 (conventional twisted tape) to 1.8. The Reynolds number is in the range of 5000–15,000, and nanoparticles volume fraction is in the range of 0 < ϕ < 1.5 % . The flow is fully turbulent, and (RNG) k − ϵ turbulent model is used for the numerical analysis. The results reveal that strong turbulent kinetic energy and additional vortex flow through the cuts of the modified twisted tapes are the main reason for better fluid mixing and heat transfer enhancement. The heat transfer enhances about 14.5% for the case of ϕ = 1.5 % . Furthermore, using double V-cut twisted tapes improves the Nusselt number of the nanofluid flow inside heat exchangers about 138% compared to conventional twisted tape without cuts. The maximum value of the thermal performance η = 1.99 is achieved by using nanofluid with ϕ = 1.5 % and b/c = 1.8 at Re = 5000. [ABSTRACT FROM AUTHOR]

Entropy generation analysis for the Cu–water nanofluid flow through a heat exchanger tube equipped with perforated conical rings is numerically investigated. Frictional and thermal entropy generation rates are defined as functions of velocity and temperature gradients. Governing equations are solved by using finite volume method, and Reynolds number is in the range of 5000–15,000. The effects of geometrical and physical parameters such as Reynolds number, number of holes and nanoparticles volume fraction on the thermal and viscous entropy generation rates and Bejan number are investigated. The results indicate that the thermal irreversibility is dominant in most part of the tube. But it decreases with increasing the nanoparticle volume fraction. Frictional entropy generation reduces with increasing the number of holes from 4 to 10. This is because of stronger velocity gradient near the perforated holes. Bejan number decreases with augment of Reynolds number. [ABSTRACT FROM AUTHOR]

In this paper, a novel study on the heat transfer characteristics in a shell and tube heat exchanger with wavy cosine corrugated wall in structure of tube bundle is investigated experimentally. The optimization procedure is performed by means of response surface methodology in different wavy starting lengths (0 mm ≤ b ≤ 120 mm), hot water flow rates (7 L min−1 ≤ Qh ≤ 11 L min−1), cold water flow rates (11 L min−1 ≤ Qc ≤ 19 L min−1) and wavy wavelengths (0 mm ≤ λ ≤ 80 mm) to obtain maximum effectiveness and the overall heat transfer coefficient. An exergetic sustainability analysis has been done to show how exergy efficiency affects sustainability. The results show that the effectiveness and the overall heat transfer coefficient increase with the cold water flow rates. Additionally, enhancement of the wavy starting lengths decreases the heat exchanger effectiveness and the overall heat transfer coefficient. From sustainability point of view, the corrugated tube is more sustainable than smooth tube. [ABSTRACT FROM AUTHOR]

Numerical simulations are used to analyze the thermal performance of turbulent flow inside heat exchanger tube fitted with cross-cut twisted tape with alternate axis (CCTA). The design parameters include the Reynolds number (5000