Formation And Properties Of Phase Change Microemulsions

Phase change microemulsions (PCMs), not only inherit good mobility and goodstability of microemulsions, but also with good performance of heat storage/release asphase change materials. As new functionally thermal fluids, PCMs can be used assubstitutes of traditional refrigeration materials and the cooling effect can be improvedefficiently. They are expected to be applied well in thermal management devices ofmicro channel in high-power apparatus.We choose n-octadecane as phase change materials in the paper, and explore adifferent titrimetric method of forming PCMs: alternate method of water titration andco-surfactant titration. We selected surfactants and the formula by comparing andanalysis of solubilization ability, the area of microemulsions region in the pseudoternary phase diagrams, stability and ultraviolet absorbance of the PCMs samplesprepared. After researching the influence of ingredient and process conditions to thePCMs, the following results are drawn: the best surfactants are octadecylpolyoxyethenyl ether and Tween-60mixed at a weight ratio of1:2; the most suitableco-surfactant is n-pentanol with a best Km=2:1; the additive of salt-inorganic sodiumchloride in the formula is advantageous to improve the stability of samples, and the bestsalinity is0.05g; the PCMs is appropriated to formed at about40℃with a medialagitation rate.After preparing n-octadecane PCMs samples containing different water content,dyeing methods are used to discriminate the different types of samples. The conclusionsdrawn by testing performance of samples are as follows: the spherical particles size ofPCMs is very small and distributes between10nm and100nm. Electro conductivityappears disciplinarian changes with the changes in water content, which is alsorecognized as judgment of types of samples. As the weight ratio of oil, surfactant andco-surfactant is1:2:1, and percentage of water is52%, the PCMS has a best practicalviscosity:25mpa·s. the samples are good in stability at20~60℃, and even after100times cooling and heating cycles, they can still keep uniform and transparent. The phasechange temperature and heat storage ability of PCMs show enhanced tendency with theincrease of oil content, and when the oil percentage is40%, the max phase change latentheat is67.91J/g, which is more than twice of pure water. The simple we prepared hasstronger heat storage ability and better fluid. They perform high efficiency of heattransfer when flow as refrigeration medium and have a perfect potential in thermalmanagement technique.