\r\nfor a cross flow cylinder of 16 mm diameter in a vertical pipe has

\r\nbeen studied for single-phase flow (water\/oil) and multicomponent

\r\n(non-boiling) flow (water-air, water-oil, oil-air and water-oil-air). The

\r\ncylinder is uniformly heated by electrical heater placed at the centre

\r\nof the element. The results show that the values of average heat

\r\ntransfer coefficients for water are around four times the values for oil

\r\nflow. Introducing air as a second phase with water has very little

\r\neffect on heat transfer rate, while the heat transfer increased by 70%

\r\nin case of oil. For water–oil flow, the heat transfer coefficient values

\r\nare reflecting the percentage of water up to 50%, but increasing the

\r\nwater more than 50% leads to a sharp increase in the heat transfer

\r\ncoefficients to become close to the values of pure water. The

\r\nenhancement of heat transfer by mixing two phases may be attributed

\r\nto the changes in flow structure near to cylinder surface which lead to

\r\nthinner boundary layer and higher turbulence. For three-phase flow,

\r\nthe heat transfer coefficients for all cases fall within the limit of

\r\nsingle-phase flow of water and oil and are very close to pure water

\r\nvalues. The net effect of the turbulence augmentation due to the

\r\nintroduction of air and the attenuation due to the introduction of oil

\r\nleads to a thinner boundary layer of oil over the cylinder surface

\r\ncovered by a mixture of water and air bubbles.", "references": null, "publisher": "World Academy of Science, Engineering and Technology", "index": "International Science Index 123, 2017" }