Thermal Performance Of Two-phase Closed Thermosyphon Research Articles

Experimental Study on the Enhanced Thermal Performance of Two-Phase Closed Thermosyphon Using Mechanical and Chemical Treated MWCNTs Nanofluids

Nowadays the two-phase closed thermosyphon (TPCT) has been widely used as an important heat transfer medium for passive cooling systems. Since the enhancement of the performance of electronic device releases a considerable amount of heat, the development of working fluids which can improve thermal performance of the TPCT is necessary. In this experiment, two different type of MWCNT nanofluids were successfully made by using ball-mill process and alkaline treatment. The morphological and structural analysis were conducted by using transmission electron microscope (TEM), fourier-transform infrared spectroscopy (FT-IR). Also thermal conductivity of modified MWCNT nanofluids were investigated by introducing transient hot wire method. The results of TEM, FT-IR and thermal conductivity showed that the MWCNTs were successfully functionalized as well as had higher thermal conductivity. The TPCT was fabricated with copper tube and total length of the TPCT is 700mm, in which the evaporator section, the adiabatic section and the condenser section are 150mm, 400mm, and 150mm, respectively. The experiment of the thermal performance of the TPCT was evaluated by introducing RMS value of the temperature of the evaporation section, thermal resistance and heat transfer coefficient at five different filling ratios, 10%, 30%, 50% and 70% by ratcheting up heat loads in five levels, 5W, 8W, 10W, 13W and 15W. The overall results showed that the both of modified MWCNT nanofluids can decrease thermal resistance and increase the heat transfer coefficient, especially at 10% filling ratio with 8W. M-CNT nanofluid can even enhance the thermal performance of TPCT at 30% filling ratio with all heat loads.

An experimental investigation on thermal efficiency of two-phase closed thermosyphon (TPCT) filled with CuO/water nanofluid

The purpose of this study is to experimentally investigate thermal performance of Two Phase Closed Thermosyphon (TPCT) using nanofluid containing CuO nanoparticles at a mass concentration of 1% and 2% wt. For this purpose, an experimental setup was designed and manufactured which contains a copper pipe, 100 cm in length and 18 mm in the inner diameter. TPCT consists of three sections: the evaporator section (40 cm), adiabatic section (20 cm) and condenser section (40 cm). The evaporator section was wrapped with electrical spiral heater to apply heat, and whole section of TPCT was insulated. A cooling water circuit was used to remove the heat from condenser section. The temperatures were measured on the TPCT surface and cooling water inlet and outlet. The inclination angle of the TPCT was fixed at 90°. The effects of various parameters such as heat load (ranging from 200 to 800 W), cooling water flow rate (ranging from 18 to 54 l/h) and type of working fluid on the thermal performance of TPCT were examined. The results were plotted graphically and discussed in detail. As a result, the performance enhancement was established by using CuO/water nanofluids instead of pure water in TPCT. Approximately 10% and 18.5% enhancement were found when 1% CuO/water and 2% CuO/water nanofluids were used, respectively. In addition, TPCT thermal resistance was reduced averagely 25% and 35% with the use of 1%CuO/water and 2%CuO/water working fluids, compared to the base fluid pure water.

Numerical Investigation of Regular and Hybrid Nanofluids Application as the Working Fluids on Thermal Performance of TPCT

Two-phase closed thermosyphon (TPCT) is a cost-effective heat transfer device with high thermal efficiency owing to extensive interphase heat and mass transfer. Thus, TPCT has found many industrial applications. Proper selection of the working fluid could further improve efficiency of TPCT, and nanofluids with superior thermal properties are suitable choices. Numerical simulation of boiling and condensation, natural circulation, and hybrid nanofluid modeling in a closed space is a notable challenge and current study is devoted to this subject. In this study, a novel methodology for incorporating the effects of compressibility and thermal expansion into all thermophysical properties of both phases is developed and programmed into a validated computational fluid dynamics (CFD) code. Distilled water, a regular nanofluid, Al2O3/water, and a hybrid nanofluid, TiSiO4/water are selected as the working fluids. Experimental data for wall thermal profile are employed to validate the numerical simulation. Then, overall thermal resistance is evaluated in terms of nanoparticles concentration and input power variations. Results indicate that the numerical methodology developed in this study could evaluate the optimum state of TPCT in an efficient and accurate manner and the optimum state for regular and hybrid nanofluid demonstrates 48% and 54% improvement over distilled water, respectively. Furthermore, a subtle relation between the thermal resistance and the height to which fluid column rises in TPCT has been discerned and quantified, which is used as a supplement to the conventional qualitative method of reasoning to justify the somewhat controversial behaviors of nanofluid application in TPCT.

Experimental investigation of two-phase closed thermosyphon used in heavy duty extrusion pelleting line

Efficient cooling system is an essential part of heavy duty extrusion pelleting line which plays an important role in production engineering of megaton polyolefin. In this paper, a new cooling system based on two-phase closed thermosyphon (TPCT) used in heavy duty extrusion pelleting line was presented. Comparative experimental results show that thermal performance of TPCT is more efficient, and the temperature uniformity is much better than traditional extruder (similar to coiled heat exchanger) in preheating process and extrusion reaction process. The effects of different operation conditions: filling ratio (0.2, 0.35, 0.5, 0.65 and 0.8), flow rate of cooling water (120L/h, 180L/h, 240L/h, 300L/h and 360L/h) and heating power (7kW, 9kW and 11kW) on thermal characteristics were experimental investigated, respectively. The results show that temperature of barrel inner wall increased significantly as filling ratio increased and evaporator appeared dry out when filling ratio is 0.2. The flow rate of cooling water affected the condenser section obviously, but had little influence on evaporation section. With increase of heating power, the start-up time decreases and the heat transfer coefficient increased. An ideal cooling scheme was concluded: the liquid filling ratio was 0.35, the cooling water flow rate was 180L/h and the heating power was 11kW when working medium was water.

An experimental investigation of the thermal performance of two-phase closed thermosyphon using zirconia nanofluid

In this work an avant-garde study is made to find out the thermal performance of two-phase closed thermosyphon (TPCT) using ZrO2 (5 - 25 nm) nanoparticle with base fluid water. The TPCT is fabricated from the copper tube with the outer diameters of 6mm, 8mm and length of 800mm. The concentration of nanofluid is varied from 3% and 4% by weight. The experimental work is carried out under different operating conditions. The input parameters such as effects of input power, fill ratio and nanoparticle concentration on the thermal efficiency and thermal resistance of the TPCT were investigated, compared and discussed. From the results, it is observed that the efficiency of the TPCT increases when ZrO2/water nanofluid was used instead of water.