Fumin Shang

Study on Heat Transfer Enhancement of Oscillating-Flow Heat Pipe for Drying

The application of oscillating-flow heat pipe (OFHP) in drying is of great potential. In this article, two methods are proposed to enhance the heat transfer of OFHP: (1) pulse heating is adopted instead of conventional continuous heating; and (2) a tube with a nonuniform cross section is introduced. Experiments on the effects of these two methods have been studied in comparison with ordinary OFHP. Experimental results indicate that using the pulse heating and the nonuniform cross section channel can improve the oscillating process and the heat transport performance in the OFHP. The heat transfer rate of pulse heating OFHP is higher than that of the continuous by 15–38%, and the effective thermal conductivity is higher by 12–63% at the same heating power. The effective thermal conductivity and the heat transfer rate of the nonuniform cross section heat pipe are also higher than that of the uniform cross section heat pipe when the heating power is more than 100 W.

Experiments on Enhanced Heat Transfer of Self-Exciting Mode Oscillating-Flow Heat Pipe with Non-Uniform Structure

Experiments were performed on a closed loop self-exciting mode oscillating flow heat pipe (SEMOS HP) with uniform and non-uniform structures under the same tested conditions. The heat transfer characteristics are analyzed by comparing the temperature of wall of the heat pipe and output power when the heat input of the electric heating board and heating position are changed. The result shows that the heat transfer rate could be improved by using a non-uniform structure under low or middle heat input, and it gives the highest heat transfer performance when the non-uniform diameter section is at the bottom of the heat pipe and the heating source located below the non-uniform section.

Experimental Investigation on the Heat Transferring of Nanofluid in Self-Exciting Mode Oscillating-Flow Heat

In this article, the heat transferring property of the copper-water nanofluids in self-exciting mode oscillating flow heat pipe under different laser heating power is experimented, as well as is compared with that of the distilled water medium in self-exciting mode oscillating flow heat pipe under same heating condition. The objective of this article is to provide the heat transfer characteristics of Cu-H2O nanofluids in self-exciting mode oscillating-flow heat pipe under different laser heating input, and to compare with the heat transfer characteristics of the same heat pipe with distilled water as working fluids.The SEMOS HP used in this experiment is made of brass tube with 2mm interior diameter, which is consisted of 8 straight tubes with 4 turns’ evaporation section and 12 turns’ condensation section. The heat resource for the evaporation zone is eight channel quantum pitfall diode array semi-conductor laser heater with 940nm radiation wave length, while the radiation power of each channel is changeable within 0–50W and the facular size is 1×30mm2. The condensation section is set in a cooling water tank in which water is from another higher tank. The actual transferring rate could be calculated by the flow rate of the cooling water and the change of the temperature. The change of the temperature of the heat pipe wall is measured by those thermo-couple fixed in different section in the heat pipe and data is collected by a data acquisition. In the heat pipe the fluid filling rate is 43%, the pressure is 2.5×10−3Pa, and the heat pipe inclination angle is 55° while the size of the brass particle in the nanofluids is less than 60nm and volume proportion is 0.5%.In this paper, the particularity of heat transfer rate of the SEMOS heat pipe with Cu-H2O fluid has been experimentally confirmed by changing the proportion of working fluid and Cu nonsocial particles in the heat pipe. By comparing the experimental result of these two different medium in the SEMOS HP, it is shown that the heat transferring rate with brass-water nanofluids as medium is much better than that with distilled water as medium under same volume proportion.Copyright