Preparation And Properties Of Fatty Acid/Alcohol Composite Phase Change Energy Storage Materials

Air conditioners are becoming increasingly popular these days.The condensation heat generated by the air conditioner is directly discharged to the outside.This will result not only in energy waste,but also in thermal pollution of the environment.As a result,recycling the condensation heat of air conditioners is critical.The use of phase change materials in the condensation heat recovery system of air conditioners has grown in recent years.The phase change materials are used to absorb condensation heat when the phase change occurs in order to heat and prepare domestic hot water.This can not only reduce air pollution and greenhouse gas emissions while improving the atmosphere,but it can also play an important role in energy conservation and environmental protection.This paper primarily focuses on the preparation of composite phase change energy storage materials with a phase change temperature range of 40-55°C that are suitable for air conditioning condensation heat recovery.The microstructure,chemical structure,heat transfer properties,and thermal properties of the composite phase change materials were evaluated and characterized.Myristic-palmitic acid/nano-silica/silicon carbide composite phase-change heat storage materials were prepared by porous adsorption method.The myristic-palmitic acid binary eutectic mixture is used as the phase change material,the nano silicon dioxide is used as the porous matrix material for adsorbing the phase change material,and the silicon carbide is used as the thermal conductive nano filler.The optimum mass ratio of myristic-palmitic acid binary eutectic mixture adsorbed in nano-silica was62wt%.The thermal conductivity of the composite phase change material containing9wt% silicon carbide is 0.776W/m K,which is an increase of 83.02% over the thermal conductivity of the composite phase change material without silicon carbide.The melting/solidification temperature of the composite phase change material is 42.96/44.12 °C,and the melting/solidification latent heat is 88.37/82.45 J/g.In general,the prepared composite phase change material has good thermal stability in the working temperature range.The myristic acid/nano-silica composite phase change material was prepared by melt blending method with myristic acid as phase change material and nano-silica as porous matrix material for adsorbing myristic acid.It was filled with graphene and multi-wall carbon nanotube thermal conductive fillers,and the effect of the ratio of graphene and multi-wall carbon nanotube mixed thermal conductive fillers on the thermal conductivity of composite phase change materials was studied and analyzed.A series of experiments show that the thermal conductivity of the composite phase change material is highest when the mass ratio of graphene to multi-walled carbon nanotubes is 3:2.Thermal conductivity is increased by 32.28%,61.13%,and 74.71%when compared to composite phase change materials with mass ratios of 5:0,0:5,and0:0,respectively.The melting/solidification temperature of CPCM3(3:2)is51.98/52.54℃,and the latent heat of melting/solidification is 123.75/109.71J/g.Furthermore,the study discovered that the ratio of various mixed thermal conductive fillers has little effect on thermal stability and thermal storage performance.The stearic acid/nano-silica composite phase change material was prepared by melt blending method with stearic acid as phase change material and nano-silica as porous matrix material for adsorbing stearic acid.Simultaneously,multi-walled carbon nanotubes and mixed boron nitride thermally conductive fillers were added.The synergistic effect of the two mixed thermally conductive fillers on the thermal conductivity of the composite phase change material was investigated by varying the ratio of the two mixed thermally conductive fillers.The test results show that when the mixed thermal conductive filler ratio is 1:1,the thermal conductivity of composite PCMs is the best,demonstrating the most effective synergistic efficiency.The melting/solidification temperature of CPCM4(1:1)was 51.44°C/52.41°C,and the latent heat of melting/solidification was 101.33/94.33 J/g.There is almost no thermal decomposition below 170 °C,indicating that the prepared composite PCMs exhibit good thermal stability in the working temperature range.