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n the present study, TiO2-nanofluid with different volume ratio was used as working fluids of thermosyphon and grooved heat pipe to investigate working stability. The stability behavior of system was studied with various parameters such as volume concentration of nanoparticle, orientation, heat flux, and cooling media were investigated. Specially, the present experimental unstable working behaviors between TiO2-nanofluid and pure water were compared. In the present study, the TiO2-nanoparticles were dispersed into pure water with each of cross blended concentrations of 0.05%, 0.1%, 0.5%, and 1%. In the present study, the rate of growth of unstable disturbances is expressed in terms of temperature perturbation. The best stable operation was observed with thermosyphon of 0.5 % TiO2-nanofluid. The best operation state with nanofluidic TS was observed in the 90° inclination and α = 0.5. In the present study, the enhancement of heat pipe performance with TiO2-nanofluid is presented. The both heat pipes were fabricated from the straight stainless pipe with the inner diameter and length of 10, 500 mm, respectively.

n the precision hot plate for wafer processing, the temperature uniformity of upper plate surface is one of the key factors affecting the quality of wafers. Precision hot plates require temperature variations less than ±1.5% during heating to 120°C. In this study, we have manufactured the flat plate heat pipe hot chuck of circle type (300mm) and investigated the operating characteristics of flat plate heat pipe hot chuck experimentally. Various screen mesh (40, 80, 120) were used as the structure and chamber was changed.

Thermoelectric module (TEM) systems proposed in this study adopts loop thermosyphon with TiO2-nanofluid as working fluid. The present experimental study is focused on the optSubscrSubscript textipt textimum operating condition of the TE system proposed to improve energy output and to obtain stable power generation to be used in future hybrid vehicles. The results of the present study indicate a possibility to use such loop thermosyphon TEMs for future thermoelectric hybrid automotive vehicles. The system showed the optimum performance with acetone with 50% charged amount as the working fluid for the TLT. The system with the new working fluid, nanofluids, neither improved its performance nor its stability.

The present study shows the thermal modeling on AMTEC (Alkali-metal thermoelectric power generation) system by analytical 1-D simulation method. In the present study, the unique AMTEC design model which consists of an evaporator, single BASE (Beta-Alumina Solid Electrolyte) tube, condenser and artery cable wick were presented. The operating design target of the present AMTEC system were 700°C in the evaporator section, and 400°C in the condenser section for solar energy conversion. The present AMTEC system operates near 10-15 % efficiency and this can be improved with the optimum design of the system. In case of improved BASE design, the system can reach over 30% efficiency.

This study reports a numerical CFD study concerning the effect of frost thickness on the heat transfer performance of a vertical pipe. Simulation are made under various variables affecting the frost growth such as outer flowing air conditions (temperature, flow velocity, humidity) and inner flow conditions of cryogenic fluid. The frost growth is mainly associated with the outer conditions. The frost thermal conductivity could play an important role in the froth growth. There is no great. The simulation for frost formation carried out with coupling to a commercial CFD code(CFX). The CFD simulation offers the possibility to predict frost formation within vertical geometries. The frost formation is based on the Lewis analogy of heat and mass transfer and it is embedded with CFX. The vertical surface temperature of the freezing body is determined by fluid structure interactive error method.

Abstract: The present study used TiO2-nanofluid with different volume ratios as the working fluids of a therrmosyphon and grooved heat pipe and investigated various parameters such as volume concentration of nanoparticles, orientation, heat flux, and cooling media. Further, the present study used nanofluids and dispersed TiO2-nanoparticles into pure water with each cross-blended concentration of 0.05%, 0.1%, 0.5%, and 1%. The authors observed the best heat transfer performance in the 0.05% concentration with thermosyphon. The present study presents the enhancement of heat transfer performance with TiO2-nanofluids, and fabricated a heat pipe from a straight stainless steel tube with an outer diameter and length of 10 and 500 mm, respectively. At the optimum condition for the pure refrigerant, the thermosyphon with 0.05% TiO2-nanoparticle concentration gave 1.40 times higher efficiency than that of pure water.

Abstract: The temperature uniformity on a heat pipe hot chuck (HPHC) during semiconductor wafer processing has been an important factor to critical dimension (300 mm) uniformity as the feature size of semiconductors decreases and productivity density increases due to the new process of nano size special manufacturing technology. To design the present heat pipe hot chuck system, which has enhanced temperature uniformity for the wafer process, the heat distribution of the system was analyzed experimentally with various working fluids such as water, TiO2, ATO, ITO, Al2O3, and Ag-nanofluids and 8 cell structures. Unlike the conventional solid state chuck, the present heat pipe hot chuck system consists of a heat pipe containing specially charged working fluid. Various working fluids have been tested to find best temperature uniformity feature on the top surface of hot chuck. TiO2-nanofluid was used and tested as the working fluid of the heat pipe hot chuck system in this paper. The temperature uniformity of upper surface was sustained in the range of ±1°C. A nano-porous layer was observed on the surface with the good result of surface temperature uniformity compared with distilled water.

The instability of two-phase loop thermosyphons was investigated experimentally and analytically. Three orifice type inserts were used to study the effect of change in the pressure drop in the flow channel of the TLT on the flow instability and temperature fluctuation. It is observed that a decrease in the size of the orifice insert from 3.7 mm (no insert) to 0.71 mm drastically reduced the fluctuation of the temperature, especially at the evaporator section of the TLT. With the orifice type insert of 0.71 mm for the TLT, the overall temperature fluctuation was almost completely eliminated, especially at higher power input to the TLT. The analysis based on the Kelvin-Helmholtz instability theory seems to predict reasonable well the loop stability state of the TLT with experimentally determined constant factors.