Thermal Efficiency Of Heat Pipe Research Articles

Experimental investigation on the heat transfer performance of high-temperature potassium heat pipe for nuclear reactor

Heat pipe cooled reactor (HPR) is considered as an excellent candidate for space power systems. As a core cooling method, the operational characteristics of high-temperature heat pipes need to be researched. In this paper, the heat transfer performance of potassium heat pipes (Φ30mm × 800 mm) is studied experimentally. The thermal behavior of heat pipe is tested under various conditions, including heating power (0.2–4 kW), air/water cooling method, inclination angle (0–90°), and filling ratio (20% and 100% of void in wick). And the characteristics of heat transfer limits are analyzed, consisting of dryout, entrainment, and sonic limit. The results show heating power is beneficial to heat transfer within the capillary limit. However, overheating occurs when heating power exceeds the capillary limit. The inclination angle has a strong effect on the thermal efficiency of heat pipe for the competition between gravity and entrainment, and the angle of 30° corresponds to the best thermal performance. Sonic limit and entrainment limit are estimated with a relative error of 38.7% and 17.9%. Dryout is divided into local dryout (<200 °C/m) and integral dryout (>200 °C/m). It is concluded that the high filling ratio (100%) and the small inclination angle (30°) are helpful to realize the optimal thermal performance. This work makes it possible to validate the operation of a high-temperature heat pipe and provides a reference for the design and application of HPR.

Experimental Study of Al2O3 Nanofluids on the Thermal Efficiency of Curved Heat Pipe at Different Tilt Angle

This paper represents an experimental study about the effect of curves related to thermosyphons and heat pipes with different active fluids and inclination angle at the thermal efficiency. The nanofluid utilized in this work is an aqueous soluble of Al2O3 nanoparticles with 35 nm diameter in pure water. The test saturation level of nanoparticles is 0%, 1%, and 3%wt. All the experiments were conducted and repeated at inclination angle of 30°, 60°, and 90° (vertical). The article presents the gravity impacts on the heat transfer characteristics in different angles and the effects of working fluids and tilt angle of heat pipe tube by the addition of nanoparticles and weight fractions on the thermal efficiency of heat pipe at different inclination. According to the experimental results, the heat pipe at the tilt angle of 60° generates the superior results. At a particle volume concentration of 1%, the use of Al2O3/water nanofluid gives significantly higher heat transfer.

Experimental Study of Thermal Performance of Nanofluid-Filled and Nanoparticles-Coated Mesh Wick Heat Pipes

The enhancements in thermal performance of mesh wick heat pipe (HP) using TiO2/H2O nanofluid (0.5, 1.0, and 1.5 vol %) as working fluid for different (50, 100, and 150 W) power input were investigated. Results showed maximum 17.2% reduction in thermal resistance and maximum 13.4% enhancement in thermal efficiency of HP using 1.0 vol % nanofluid as compared to water. The wick surface of the HP was then coated with TiO2 nanoparticles by physical vapor deposition method. The experimental investigation had been also carried out on coated wick HP using water as working fluid. Results showed 12.1% reduction in thermal resistance and 11.9% enhancement in thermal efficiency of the HP as compared to uncoated wick HP using water. Temporal deteriorations in thermal performance during prolonged working (2, 4, and 6 months) of HP were also studied. Temporal deterioration in thermal performance of HP filled with nanofluid depends upon the deterioration in thermophysical properties of nanofluids. The deterioration is due to the agglomeration and sedimentation of nanoparticles with respect to the time. Comparative study shows that after a certain time of operation, thermal performance of HP with nanoparticle coated wick superseded that of the HP filled with nanofluid. Therefore, nanoparticle coating might be a good substitute for nanofluid to avoid the stability issues. The present paper provides incentives for further research to develop nanofluids that avoid the encountered sedimentation or agglomeration.

Contemplation of thermal characteristics by filling ratio of Al2O3 nanofluid in wire mesh heat pipe

An experimental investigation on the thermal efficiency and thermal resistance with respect to the inclined angle using heat pipe was carried out. The working fluids used for this are Al2O3 nanofluid and deionized water. The performance of heat pipe in terms of overall heat transfer coefficient and thermal resistance is quantified by varying the volume of working fluid and the performance parameters are contemplated. For this purpose Al2O3 nanoparticles with a density of 9.8g/cm3 and a volume concentration of 1% are used as the working fluid in experimental heat pipe. The performance of heat pipe was evaluated by conducting experiments with different thermal loads and different angle of inclinations. Thermocouples are used to record the temperature distribution across the experiment. Volume of nanoparticles in the base fluid and the consequence of filling ratio on the thermal resistance of the nanofluids are investigated. The results provide evidence that the suspension of Al2O3 nanoparticles in the base fluid increases the thermal efficiency of heat pipe and can be used in practical heat exchange applications.

Performance analysis of cylindrical heat pipe using nanofluids – An experimental study

The present work analyzes the thermal performance of a cylindrical copper mesh wick heat pipe using water based CuO nanofluids. The studies are extended further by varying the heat pipe inclination angle and heat input. Thermophysical properties of CuO/DI water nanofluids are also effectively analyzed. The reduction in thermal resistance ratio is about 23.83% and 10.43% respectively for 1.0 and 1.5wt.% of CuO nanofluid compared with low concentration. Evaporation and condensation heat transfer coefficient ratios are improved by the use of CuO nanofluid and the maximum enhancement obtained is 30.50% and 23.54% respectively for an optimum tilt angle of 60°. Thermal efficiency of heat pipe tends to increase with the heat load and inclination angle and an improvement of 33.34% is observed for 120W heat load at 60° inclination angle compared with the horizontal heat pipe. After the experimentation, characterizations of mesh wick structures are carried out. It is found that the deposition of CuO nanoparticles creates a thin coating layer on the wick surfaces in evaporator section. This increases the surface wettability and enhances the thermal performance of heat pipe.

Thermal efficiency of heat pipe with alumina nanofluid

The study presents the enhancement of thermal efficiency of heat pipe charged with nanofluid. The Al 2O 3/water nanofluid produced by direct synthesis method is used as the working fluid of experimental heat pipes with three different concentrations (0.5, 1.0 and 3.0 wt.%). The heat pipe is a straight copper tube with inner diameter and length of 8 and 600 mm, respectively. The heat pipes charged with distilled water and nanofluids are tested, respectively. The study discusses about the effects of charge amount of working fluid, tilt angle of heat pipe and weight fraction of nanoparticles on the thermal efficiency of heat pipe. According to the experimental results, the optimum condition of heat pipe is when nanoparticles being at 1.0 wt.%. Under this condition, the thermal efficiency is 16.8%, which is higher than that of heat pipe charged with distilled water. The charge amount can be decreased from 60% to 20%.

Experimental investigation of titanium nanofluids on the heat pipe thermal efficiency

The enhancement heat transfer of the heat transfer devices can be done by changing the fluid transport properties and flow features of working fluids. In the present study, therefore, the enhancement of heat pipe thermal efficiency with nanofluids is presented. The heat pipe is fabricated from the straight copper tube with the outer diameter and length of 15, 600 mm, respectively. The heat pipe with the de-ionic water, alcohol, and nanofluids (alcohol and nanoparticles) are tested. The titanium nanoparticles with diameter of 21 nm are used in the present study which the mixtures of alcohol and nanoparticles are prepared using an ultrasonic homogenizer. Effects of %charge amount of working fluid, heat pipe tilt angle and %nanoparticles volume concentrations on the thermal efficiency of heat pipe are considered. The nanoparticles have a significant effect on the enhancement of thermal efficiency of heat pipe. The thermal efficiency of heat pipe with the nanofluids is compared with that the based fluid.