Experimental Investigation On Nucleate Pool Boiling Heat Transfer For Mechanically Fabricated Porous Surface Tube

With the development of our country's industry and agriculture and improvement of people's living standard, requirements for the energy resource increase rapidly. Boiling heat transfer with small temperature difference has greatly economic significance for both the reasonable utilization of available energy and the exploitation of new energy.The energy expense in petro-chemical units accounts for sixty percent of its overall operating cost, so it has great significance to design high efficient and compact heat exchanger both for enhancing heat transfer and for optimizing energy application. Two reasons make enhancement of boiling heat transfer as a key technique for the improvement of petro-chemical equipment's performance. Firstly, there are many boiling heat transfer devices in which smooth tubes are still used, so the heat transfer effects of these equipments are not well. Secondly, alkyl or hydrocarbon, that is widely used in the petro-chemical devices, has relatively lower boiling heat transfer coefficient, not only lower than water, but also less than the medium of another side in heat transfer equipment.Porous surface has been widely used as a component of heat transfer enhancement in evaporators of refrigeration units to improve their heat transfer performance. This technique can also be used in the petro-chemical units. Some progresses have been made in this area in our country, for example, T -tubes are used to replace smooth tubes and thereby great effects have been achieved in effectiveness of heat exchanger. There are still big potential in improving heat transfer performance through changing surface shape of the heat transfer component. Mechanically fabricated porous surface can be widely used because of its simple fabricating technique, regular shape and lower cost.This paper investigated experimentally the nucleate pool boiling heat transfer for three mechanically fabricated porous surface tubes with different openings at 1 bar. Water and alcohol were used as working fluids in the experiments. The experimental results showed that the heat transfer coefficients of these porous surface tubes were 1.8-2.3 times larger than that of smooth tube. The tube with opening of 0.3 mm enhanced the nucleate boiling heat transfer better than other tubes. Based on reduction of the experimental data, the boiling heat transfer mechanism of porous surface was...