Using of Multi-Wall Carbon Nanotube (MWCNT) Based Nanofluid in the Heat Pipe to Get Better Thermal Performance

Using of Multi-Wall Carbon Nanotube (MWCNT) Based Nanofluid in the Heat Pipe to Get Better Thermal Performance

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Heat pipe is a device for transferring heat with high heat conduction ratio. It transfers heat energy by vaporization and condensation of a fluid with little temperature reduction. A heat pipe has three section in general including evaporator, adabatic and condenser sections. When heat reaches evaporator, the fluid evaporates and it forms a different pressure in the pipe. The different fluid pressure causes the vapor moves through the pipe and reach condenser. In condenser section, the vapor condenses and its latent heat releases and then the fluid returns from inside wick by capillary pressure to evaporator section. This study has been conducted to show the effect of using three water based nanofluids (water+ Al2O3), (carbon nanotube+water) and (water+diamond) on the heat operation of heat pipe. We also applied a new correlation for viscosity of nanofluids developed by bakhshan et al.[7].Finally the graphs of velocity, temperature, pressure and heat resistance of heat pipe were obtained with using the nanofluids and carbon nanotube and has been compared with conventional operation of heat pipe which uses from pure water.

A mathematical model of a cylindrical heat pipe using TiO2, CuO, and Al2O3 nanofluids was solved analytically by shafahi et al., [1]. The thermal performance of cylindrical heat pipes utilizing the above nanofluids as the working fluid has been investigated. They obtained the velocity, pressure, temperature and maximum heat transfer limit for different nano- particle concentration levels and sizes. Their results show that the thermal performance of a heat pipe is improved and temperature gradient along the heat pipe and thermal resistance across the heat pipe are reduced when nanofluids are utilized as the workin...

... middle of paper ... authors, the numerical simulation of a cylindrical heat pipe has been donned and the liquid pressure, temperature distribution, heat pipe wall temperature, heat pipe temperature difference, heat pipe heat transfer coefficient and thermal resistance of it are extracted.

2. Mathematical modeling

The geometry of problem is shown in Fig.1. A conventional cylindrical heat pipe with a constant conductance coefficient constant of a sealed container and fully saturated annular porous wick material with working fluid have been used. The heat pipe has three zones: evaporator, adiabatic section and condenser. Due to axi-symmetric condition, the simulation field is considered two-dimensional and steady state and the governing equations are: continuity, momentum and energy for both region of vapor and liquid. Also, the fluid flow has been assumed laminar and incompressible.

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