The Experimental Research On The Direct Contact Heat Exchange

In the trend of the reasonable use and the development of new energy, heat exchanger is the key equipment of the reasonable use and conservation of energy as well as development of new energy, so it has been widely used in the industrial and agricultural production. As a kind of new and more efficient heat exchange equipment, direct contact heat transfer exhibits many advantages over the traditional shell-and-tube units, such as higher thermal efficiency, hard for corrosion, operation in low temperature, hard for incrustation. Heat transfer model of direct contact heat transfer and experimental verification were established by theoretical analyses, which had some guiding significance to design and application of direct contact heat transfer.On the basis of the theoretical research of direct contact heat transfer both home and abroad, a further research of oil-organic fluid direct contact heat transfer was presented, which would be applied in ORC promisingly:(1) Through combination with the first law of thermodynamics, the law of conservation of mass and the momentum theorem, the mathematical model of direct contact heat transfer for the disperse phase R245fa in the continuous phase heat-transfer oil THERMINNOL(?)66was established:①The mathematical model of heat transfer for the dispersed phase single droplet in the continuous phase solution was established, and the calculation formula of heat transfer coefficient for a single dispersed phase of bubble in the continuous phase(in the liquid-vapor interface) and theNusselt number calculation formula were deduced;②The mathematical model of bubble growth for a single dispersed phase of bubble was established. The bubble growth rate for a single dispersed phase of bubble in the evaporation process dR/dτ=a/2R NuJa, the radius ratio and that for the two-phase bubble which was evaporated completely were deduced;③The mathematical model of direct contact heat transfer for the dispersed phase droplet group in the continuous phase solution was established, and the computation relational of the volumetric heat transfer coefficient: was deduced.(2) The performance test device of the oil-organic fluid direct contact heat transfer was designed then set up, and experimental tests R245fa were done—HERMINNOL(?)66heat-transfer oil heat exchange system under different operating conditions. After comparison with the theoretical model, the relative error was less than10%, which verified the prediction accuracy of theoretical model in direct contact heat transfer performance. In addition, the liquid column height, the dispersed phase flow, the dispersed phase evaporation, the initial temperature of heat-transfer oil and the law of orifice diameter on the heat transfer performance were investigated by the experiment, and as follows were concluded:①The volume heat transfer coefficient first increased, then decreased with the rise of liquid level in the tank. This showed that the volume heat transfer coefficient could reflect the heat transfer performance of good or bad in certain refrigerant volume conditions, however, if the fluid column height changed, the analysis should go on according to the actual situation;②The volume heat transfer coefficient increased with the increase of dispersed phase flow and evaporation as well as temperature difference;③The volume heat transfer coefficient decreased with the increase of the orifices diameter.(3) In the same heat transfer conditions, thermal efficiency of direct contact heat was2.13times than that of plate heat exchanger.