Hamdy Hassan

A Three-Dimensional Study of Electronic Component Cooling Using a Flat Heat Pipe

In this article, a three-dimensional thermal and hydrodynamic numerical model using a flat heat pipe (vapor chamber) is proposed for cooling of electronic components. The heat pipe is composed of a vapor region sandwiched between two wick regions, which are covered by two flat copper plates. A three-dimensional hydrodynamic model was developed to solve the fluid flow through the liquid and vapor regions. The hydrodynamic model is coupled with a three-dimensional thermal model using the energy equation to estimate the model temperature. The hydrodynamic model takes into consideration the return liquid between the two wick regions. An implicit finite-difference method is used to solve the theoretical model. The numerical model was validated by using an experimental work and the results of the literature. Good agreement was found between the numerical results and the experimental work and the literature. The effect of the power input and heat transfer coefficient of the cooling fluid on the performance of the vapor chamber was studied. Our models results illustrate well the movement of the working fluid in the wick and vapor regions. They also indicate that when the power input or the heat transfer coefficient of the cooling fluid increases, the maximum pressure difference between the heat pipe and convection inside the wick regions increases.

An Experimental and Numerical Study on the Effects of the Flat Heat Pipe Wick Structure on Its Thermal Performance

This paper presents an experimental and numerical work on the effect of flat heat pipe construction on the cooling of an electronic component. The flat heat pipe is heated via 1-cm-diameter circular electrical resistance (the evaporator side), and the other side (the condenser side) is cooled by convection through a heat sink. In the experimental work, three types of wick construction are used in the heat pipe: (A) mesh + powder, (B) mesh, and (C) powder. A comparison is performed of the electronic component cooling from the heat pipe, copper block, and open heat pipe constructions. The numerical work studies the effect of wick porosity on the heat pipe performance for different wicks that we could not study experimentally. For forced convection, heat pipe A is more efficient for the electronic component cooling than the copper block and other heat pipe construction. For free convection, the copper block is the most efficient. The maximum variation of the heat pipe temperature is about 19% due to change of the heat pipe construction. When the wick porosity increases, the temperature increases and the pressure decreases. The rectangular groove construction produces the minimum temperature compared to the wrapped screen and packed sphere constructions.

Effect of Operating Parameters on the Heat Transfer and Liquid Film Thickness of Revolving Heat Pipe

ABSTRACT This paper presents a study on the effects of operating parameters on the liquid film thickness and heat transfer of revolving heat pipe. The effects of speed, radius of rotation, evaporator and condenser temperatures, and mass of the working fluid are considered. Also, the effects of these parameters on the maximum heat transfer and minimum mass of the working fluid supplied to the heat pipe are considered. A simplified theoretical model is presented to estimate the heat transfer and the liquid film thickness. The theoretical model is used to determine the driven forces on the control volume. The system of equations associated with the heat pipe model is solved using the fourth-order Runge–Kutta method through a numerical code written in MATLAB. The results show that the heat transfer increases by decreasing the mass of the working fluid and increasing the temperature difference through the heat pipe. They also show that the liquid film thickness increases with the decrease in temperature difference and with increase in the mass of fluid. The maximum heat transfer increases with the increase in the rotation speed. The minimum mass of the working fluid supplied to the heat pipe increases with the increase in temperature difference and with the decrease in the rotation speed.

Effect of Cu-water nanofluid on the heat transfer by rotating heat pipe

This paper presents a study on the effect of using Cu-water nanofluid on the heat transfer by rotating heat pipe (RHP). A mathematical model is presented of the RHP including, vapor velocity, gravity effect and taper angle. The study is carried out at different rotation speeds, RHP temperatures differences (ΔT) and masses of working fluid of the RHP. Using of Cu-water nanofluid with RHP decreases the liquid film thickness adjacent to its walls and increases the heat transfer by RHP compared with ordinary fluid. The heat transfer by RHP increases with increasing ΔT and volume fraction and radius of solid nanoparticles. The maximum heat transfer by RHP at ΔT=20 oC and ω=3000rpm increases by about 56% due to using Cu-water nanofluid with volume fraction 0.04 and nanoparticles radius 5nm.

Optimization the regions thickness of flat heat pipe

A study on the optimization of regions thickness of flat heat pipe (FHP) and its wick porosity to have minimum temperature rise of the FHP is presented. The optimization study is performed by using particle swarm optimization method (PSO). The study is carried out at different thicknesses of the FHP, power inputs and cooling rates. The optimized results show that for minimum temperature of the FHP, the wick region thickness must be minimized. An increase of the total thickness of the FHP from 3mm to 7mm has not great effect on the optimized temperature of the FHP. The total thickness of the FHP has not great effect on the optimum thickness of the wick region. The results show that the optimum thickness of the FHP walls and vapor region increases with increase the total thickness of the FHP.