Herein, a horizontal CPU cooler with a pulsating heat pipe (PHP) for cooling desktop computer was developed. In the experiment, an electric heating block was used to heat a copper plate to simulate the heating process of CPUs. The cooling system consists of a cooling fan and a pulsating heat pipe cooler. The influence of cooling wind speed and heat load on heat transfer performance, start-up performance, and temperature uniformity of the PHP cooler was analyzed by controlling variable method. The wind speed was set to be 0 m/s, 0.1 m/s, 0.3 m/s, 0.5 m/s and 0.7 m/s respectively. The contour plots were used to analyze the uniformity of temperature distribution due to cooler. The results show that the start-up of the PHP led to a decrease in temperature of CPUs. As the cooling wind speed increased, the start-up time of the php dropped, the start-up temperature dropped, and its stability was also improved. The operation at different cooling wind speeds also changed the start-up mode of the PHP. The start-up performance was best at cooling wind speed of 0.3 m/s. The contour plot for temperature showed that the temperature distribution of the PHP cooler became more uniform with increased cooling wind speeds. There was excellent temperature uniformity at the cooling wind speeds of 0.3 m/s and 0.7 m/s. When the cooling wind speed was 0.7 m/s, the minimum average thermal resistance was 0.51 K/W.

No abstract

Here we develop a two-dimensional numerical model of WAAM to determine the relationship between process parameters and deposition geometry, and to reveal the influence mechanism of process parameters on deposition geometry. From the predictive results, a higher wire feed rate matched with a higher current could generate a larger and hotter droplet, and thus transfer more thermal and kinetic energy into melt pool, which results in a wider and lower deposited layer with deeper penetration. Moreover, a higher preheat temperature could enlarge melt pool volume and thus enhance heat and mass convection along both axial and radial directions, which gives rise to a wider and higher deposited layer with deeper penetration. These findings offer theoretical guidelines for the acquirement of acceptable deposition shape and optimal deposition quality through adjusting process parameters in fabricating WAAM components.

To meet the requirement of electronic heat dissipation with high heat flux, a kind of heat dissipation device using pulsating heat pipe (PHP) for CPU heat dissipation was put forward. The heat transfer performance and surface temperature distribution of the radiator are analyzed by analyzing the wall temperature distribution and the distribution of the evaporator and condenser of the PHP. The experimental results show that the change of wind speed has obvious influence on the operation of the PHP radiator. The surface temperature distribution of the PHP radiator is very uniform, which is especially beneficial for CPU cooling. The heat transfer performance of the PHP is better, and the minimum average thermal resistance is 0.19 k/W. In addition, there is no drying phenomenon when the temperature reaches about 120 °C, which indicates that the pulsating heat pipe has a very high heat transfer limit.

The structure and inclination angle of a pulsating heat pipe are critical factors influencing the heat transfer performance and operation mode. In this work, a single-layer double-row pulsating heat pipe is designed, and the start-up and heat transfer characteristics of pulsating heat pipe at limit angles (0?,90?, and 180?) are experimentally investigated. Also, the operation mode and heat transfer characteristics are studied through IR imager and temperature profiles. The study highlighted that the pulsating heat pipe has excellent operation characteristics in the limit angle. When the inclination angle is 0?, the double-row structure improves the start-up performance; at 90? inclination, the pulsating heat pipe starts the fastest, and the heat transfer resistance keeps the smallest in the whole test. When the inclination angle is 180?, the pulsating heat pipe has the best thermal sensitivity but weak working fluid flow capacity during operation.

No abstract

The pulsating heat pipe (PHP) is a passive cooling device, which has the advantages of simple structure, high heat transfer performance and low production cost. The complex vapor-liquid phase change occurs in the in the initial stage of PHP. In this work, we explore the start-up performance of PHP at different inclination angles and the experiment shows that start-up performance is respectively different when the angles are 0°, 45°, 90°, 135° and 180°. Since the gravitational auxiliary function, the working fluid in the communicating pipe which takes longer time to vaporize change phase earlier than that in PHP’s loop when the angles are 0° and 45°. Nevertheless, when the angle is 90°, the phase change of working fluid in communicating pipe and in the loop occurs at the same time. Meanwhile, the oscillating mode affects the stability of the starting and heat transfer performance of the PHP.