Behavior of Corrosion of a Heat Pipe Cooling Device in a Computer

The aim of this study was to perform life testing and to determine the effect of working time on the corrosion of a heat pipe used for cooling in a computer. The heat pipe was made from a copper tube. The heat pipe consists of evaporator and condenser section. It had a specification similar with the use in ordinary computers, the working fluid being distilled water. When the computer starts, the concentration of the copper solution slightly increases. The greater copper concentration was 0.00062 ppm upon 3000-5000 hours of testing. The surface traces of corrosion rises due to the oxidation of the porous material within the working fluid. The test found that oxygen (O) and carbon (C) are component contents

Three-dimensional transient mathematical model to predict the heat transfer rate of a heat pipe

A three-dimensional model was developed to simulate the heat transfer rate on a heat pipe in a transient condition. This article presents the details of a calculation domain consisting of a wall, a wick, and a vapor core. The governing equation based on the shape of the pipe was numerically simulated using the finite element method. The developed three-dimensional model attempted to predict the transient temperature, the velocity, and the heat transfer rate profiles at any domain. The values obtained from the model calculation were then compared with the actual results from the experiments. The experiment showed that the time required to attain a steady state (where transient temperature is constant) was reasonably consistent with the model. The working fluid r134a (tetrafluoroethane) was the quickest to reach the steady state and transferred the greatest amount of heat

Application of silver nanofluid containing oleic acid surfactant in a thermosyphon economizer

This article reports a recent study on the application of a two-phase closed thermosyphon (TPCT) in a thermosyphon for economizer (TPEC). The TPEC had three sections of equal size; the evaporator, the adiabatic section, and the condenser, of 250 mm × 250 mm × 250 mm (W × L × H). The TPCT was a steel tube of 12.7-mm ID. The filling ratios chosen to study were 30, 50, and 80% with respect to the evaporator length. The volumetric flow rates for the coolant (in the condenser) were 1, 2.5, and 5 l/min. Five working fluids investigated were: water, water-based silver nanofluid with silver concentration 0.5 w/v%, and the nanofluid (NF) mixed with 0.5, 1, and 1.5 w/v% of oleic acid (OA). The operating temperatures were 60, 70, and 80°C. Experimental data showed that the TPEC gave the highest heat flux of about 25 kW/m2 and the highest effectiveness of about 0.3 at a filling ratio of 50%, with the nanofluid containing 1 w/v% of OA. It was further found that the effectiveness of nanofluid and the OA containing nanofluids were superior in effectiveness over water in all experimental conditions came under this study. Moreover, the presence of OA had clearly contributed to raise the effectiveness of the nanofluid

Loop Thermosyphon with Vapour Chamber: A Thermodynamic Study

This research presents a case study of the rating heat transfer of a loop thermosyphon with a vapour chamber (LTVC). The dimensions of the evaporator chamber were 200 × 200 × 55, 200 × 200 × 65 and 200 × 200 × 75 mm ( W × L × H ). The adiabatic and condenser section had an 8-loops thermosyphon. The length of the adiabatic and condenser section in each loop was 824 and 800 mm, respectively. The air velocity was 0.5, 1.0, and 1.5 m/s with the heat input being 600, 900, and 1,200 W. The three working fluids were: water, ethanol, and R-11 with filling ratios of 20, 40, and 60% with respect to the chamber volume. The experimental data showed that the LTVC yielded the value of the relative thermal efficiency of about 1 at R-11, a filling ratio of 60%, a velocity of 0.5 m/s, and an aspect ratio of 2.5 in the study conditions. It was further found that the larger vapour chamber was superior in the rating of the heat transfer over other vapour chambers in all experimental conditions in this study

The Helical Oscillating Heat Pipe: Flow Pattern Behaviour Study

This research aims to study the effect of evaporator temperature, pitch distance, and working fluid on the internal flow pattern and the heat transfer characteristics of the helical oscillating heat pipe. A Pyrex tube with an inner diameter of 2.4 mm was used to study the flow pattern in the evaporator section. The pitch distance varied at 1, 1.5, and 2 cm. Water and R-123 were used as working fluid with a filling ratio of 80% by total volume. In the evaporator section, the water temperature varied at 60, 75, and 90°C to supply heat to the heat pipe. In the condenser section, air with a temperature of 25°C was used as heat sink. From the results, it was found that 4 internal flow patterns, bubble flow, slug flow, annular flow, and stratified wavy flow, were observed in the evaporator section for both working fluids. The heat transfer rate decreased when the pitch distance was increased from 1 to 2 cm. The maximum heat flux was 2,132.6 and 1,773.4 W/m 2 for the working fluid of R-123 and water, respectively. Both occurred at a pitch distance of 1 cm and an evaporator temperature of 90°C

Closed-ended oscillating heat-pipe (CEOHP) air-preheater for energy thrift in a dryer

The CEOHP air-preheater consisted of two main parts, i.e. the rectangular house casing and the CEOHP. The house casing was designed to be suitable for the CEOHP. The inside house casing divided the CEOHP into three parts, i.e. the evaporator, the adiabatic section and condenser section. The CEOHP air-preheater design employed copper tubes: thirty-two sets of capillary tubes with an inner diameter of 0.002 m, an evaporator and a condenser length of 0.19 m, and each of which has eight meandering turns. The evaporator section was heated by hot-gas, while the condenser section was cooled by fresh air. In the experiment, the hot-gas temperature was 60, 70 or 80 °C with the hot-gas velocity of 3.3 m/s. The fresh-air temperature was 30 °C. Water and R123 was used as the working fluid with a filling ratio of 50%. It was found that, as the hot-gas temperature increases from 60 to 80 °C, the thermal effectiveness slightly increases. If the working fluid changes from water to R123, the thermal effectiveness slightly increases. The designed CEOHP air-preheater achieves energy thrift.Closed-ended oscillating heat-pipe air-preheater Energy thrift dryer