Effect of Twisted-Tape Turbulators and Nanofluid on Heat Transfer in a Double Pipe Heat Exchanger

Heydar Maddah,Khatere Ashtary,Morshed Farokhi,Shabnam Jahanizadeh,Reza Aghayari

doi:10.1155/2014/920970

Abstract

Heat transfer and overall heat transfer in a double pipe heat exchanger fitted with twisted-tape elements and titanium dioxide nanofluid were studied experimentally. The inner and outer diameters of the inner tube were 8 and 16 mm, respectively, and cold and hot water were used as working fluids in shell side and tube side. The twisted tapes were made from aluminum sheet with tape thickness (d) of 1 mm, width (W) of 5 mm, and length of 120 cm. Titanium dioxide nanoparticles with a diameter of 30 nm and a volume concentration of 0.01% (v/v) were prepared. The effects of temperature, mass flow rate, and concentration of nanoparticles on the overall heat transfer coefficient, heat transfer changes in the turbulent flow regimeRe≥2300, and counter current flow were investigated. When using twisted tape and nanofluid, heat transfer coefficient was about 10 to 25 percent higher than when they were not used. It was also observed that the heat transfer coefficient increases with operating temperature and mass flow rate. The experimental results also showed that 0.01% TiO2/water nanofluid with twisted tape has slightly higher friction factor and pressure drop when compared to 0.01% TiO2/water nanofluid without twisted tape. The empirical correlations proposed for friction factor are in good agreement with the experimental data.

Highlights

Lehigh heat exchange devices are used in industry for heat transfer between two fluids
Aghayari et al [2] reported experimental results which illustrated the dispersion of the heat transfer and overall heat transfer coefficient of AL2O3 nanoparticles in liquid for turbulent flow in a double pipe heat exchanger
Experimental results obtained with the TiO2 nanofluid heat exchanger and twisted tape with the pitch of 3.5 can be summarized as follows

Summary

Introduction

Lehigh heat exchange devices are used in industry for heat transfer between two fluids. Thermal efficiency of water and nanofluid with the concentration of 0.1 is 1103842 and 1123123, respectively (in Reynolds of 23000), which is approximately 1.71% higher than the heat transfer of the base fluid This increase can be attributed to the immigration of the particles, nonuniform distribution of the thermal conductivity, and viscosity of the fluid which decreases the boundary layer thickness, resulting in the delay in the development of the thermal boundary layer. Many studies have been done in order to evaluate the heat transfer performance and flow characteristics of various nanofluids in both the laminar and the turbulent flow regimes [4,5,6,7,8,9,10,11,12,13,14] Results of these studies proved that the inclusion of nanoparticles improves the thermal conductivity compared to the conventional fluid and increases heat transfer rate with the nanoparticle concentration. The maximum thermal performance factor of 1.57 was found in counter arrangements at twist ratio of 2.7 and Reynolds number of 6200

Nanofluid Preparation

Apparatus

Data Reduction

Discussion and Results

Conclusion