A Study on the Heat Transfer Characteristics and Performance of the High Temperature Range Heater Plate Using Liquid-Vapor Phase Change Heat Transfer

Based on pool film boiling, the model of boiling and vaporization to heat transfer is established When droplet jet into cutting zone to cool high temperature wall. Through the transient experiment of cryogenic gas atomization jet cooling high temperature nickel-base alloys and Titanium alloys surface with different water dose. The water dose achieving the best cooling effect is obtained at different temperature on surface of Nickel based alloys and TI-alloy. It is indicated that the water dose to the best cooling effect must be equivalent to the amount of water that materials can vaporize and participate in the phase change heat transfer under certain temperature. When achieving optimal cooling effect, the amount of droplets participating in phase change heat transfer to cool high temperature wall are the most , while comparing the cold air cooling effect and spraying cooling effect at low and high temperature. Result is that either low or high temperature, spraying cooling effect is superior than cold air cooling effect, but at a specific temperature, no lower the temperature of air, the better cooling effect, there is also an optimal air temperature values.

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Experimental Study of Phase-Changeable Water/Polyalphaolefin Nanoemulsion Fluids

Volume 8B: Heat Transfer and Thermal Engineering ◽

10.1115/imece2014-36533 ◽

2014 ◽

Author(s):

Jiajun Xu ◽

B. Hammouda ◽

Fangyu Cao ◽

Bao Yang

Keyword(s):

Heat Transfer ◽

Phase Change ◽

Vapor Phase ◽

Self Assembly ◽

Water Concentration ◽

Heat Transfer Fluid ◽

Structure Transition ◽

Change Behavior ◽

Effective Specific Heat ◽

Phase Change Heat Transfer

In this work, thermal properties especially phase change heat transfer properties of one new type of nanostructured heat transfer fluid: Water/Polyalphaolefin (PAO) nanoemulsion fluid are investigated. Water is added into PAO fluid to form nanoemulsion fluids in which dispersed water nanodroplets are formed by self-assembly. The liquid-to-vapor phase change results, expressed in terms of surface heat flux and heater temperature, have shown that the presence of water nanodroplets has a drastic impact on the liquid-to-vapor phase change behavior of the nanoemulsion fluid studied: the water nanodroplet formed inside can enhance its heat transfer coefficient by over 300% after the incipience of its phase change. In addition to that, the vaporization of the water nanodroplet inside is found to be different depending on the concentration of water inside, which happens to coincide with the structure change with different water concentrations as observed in SANS measurement. On the other hand, the effective specific heat is also found to increase with higher water concentration until reaching a maximum value which also happens to coincide with the structure transition from spherical to cylinder shape with the increasing of water concentrations as observed from SANS measurement. More study is still needed to understand the mechanism behind these phenomena.

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