Study On Heat Transfer Characteristics Of Liquid Film Vaporization In Rotating Pipe

When the liquid flows through the pipe rotating along its axis with a high speed,a liquid film will be formed on the wall due to the centrifugal force,generating a circular flow.The vaporization of liquid film in rotating pipes enables efficient heat transfer in rotating parts,which is a good choice for the thermal management of rotating equipments.Now,this technology has been used in the thermal management of some components and performs well.However,the understanding of the heat transfer mechanism of vaporization of liquid film in rotating pipes is not clear,thus restricting the further development of it.In order to study the influence of key factors on the heat transfer characteristics of liquid film vaporization in rotating pipes,an experimental system was designed and built in this paper.With employment of visualization and temperature monitoring,the effects of heat flux,centripetal acceleration,properties and volume flow rate of working medium were investigated.The results show that:1)When the centripetal acceleration is 20g,a number of rows of long strips bubbles are formed circularly in the water film;2)When the volume flow rate and centripetal acceleration are constant,the increase of heat flux intensifies the boiling of water film,resulting in the increase of the number or a constant number and lager average scale of bubbles;3)When the volume flow rate and the power of heating film are constant,the increase of centripetal acceleration leads to the decrease of the number or a constant number and smaller average scale of bubbles in water film;4)The heat transfer coefficient of water film with volume flow rate of 0.18m~3/h increases and then decreases with elevating centripetal acceleration.As heat flux increases,the heat transfer coefficient peaks appear at centripetal acceleration being 80g,60g and 40g,respectively;5)The heat transfer coefficient of water film with volume flow rate of 0.35m~3/h increases and then changes slightly with increasing centripetal acceleration.With the increase of heat flux,the turning point which makes heat transfer coefficient to be stable lies at centripetal acceleration of 80g,60g and 40g,respectively;6)At the condition of constant power of heating film and volume flow rate,the relationship between heat transfer coefficient and centripetal acceleration of ethanol film is different to that of water film.When the power of heating film is 1300W and 1600W,the lowest heat transfer coefficient appears at the centripetal acceleration of 40g and 60g;7)When the power of heating film is constant(1300W,1600W)and the reference centripetal acceleration is 20-60g,increasing centripetal acceleration alone has a greater influence on the heat transfer coefficient than increasing volume flow alone.In this paper,the effects of heat flux,centripetal acceleration,volume flow rate,and physical parameters on the heat transfer characteristics of liquid film vaporization in a rotating pipe are obtained,and may facilitate the application and further research of this technology.