Experimental Study On The Properties Of Erythritol-based Composite Phase Change Material

The energy consumed in the industrial sector accounts for a large proportion of China’s total energy consumption.Due to low energy utilization,recycling industrial waste heat is particularly critical in reducing energy consumption and carbon dioxide emissions.At present,the waste heat recovery technology used in industrial production is targeted at medium and high temperature waste heat resources above 350 °C.Attention to low-and mediumtemperature waste heat resources at 350 °C,especially below 200 °C is low,and this part of waste heat is huge.Therefore,in this paper,erythritol is selected as the research object from the aspects of thermal performance,physical properties,chemical properties,economy,etc.,and the following work contents are studied for erythritol-based phase change materials:Tests on the thermophysical properties of erythritol,such as phase transition temperature and latent heat,subcooling,and thermal conductivity were carried out.The results show that erythritol has a crystallization supercooling degree of 34.5 °C,poor subcooling stability,thermal conductivity of 0.7635 W/(m·k),melting point of 118.8 °C,latent heat of melting of374.3 J/g,and exothermic capacity of only 51.86%,which is not conducive to the efficient use of energy.Aiming at the high subcooling degree,subcooling degree instability and low thermal conductivity of erythritol,a step cooling experimental bench was set up to study the subcooling characteristics.The influence of different uv irradiation temperature,cooling temperature,container material,the coupling effect of addition amount of nanoparticles and particle type,ultrasonic power and initial ultrasonic temperature on the crystallization supercooling degree,crystallization process and the instability of supercooling degree was analyzed.Studies have shown that the introduction of ultraviolet light can improve the supercooling stability of erythritol while alleviating the crystallization subcooling degree,which can reduce the maximum by 84.00%.When the initial irradiation temperature is110 ℃,the crystallization effect of erythritol is the best.In the range studied,as the cooling temperature increases,the degree of crystal supercooling decreases,which can be reduced by up to 67.66%.When the cooling temperature is 60 ℃,the crystallization effect of erythritol is the best.The crystallization supercooling of erythritol in stainless steel cups and ceramic cups is 2.26% and 6.55% lower than that of erythritol in glass beakers.In addition,the crystallization effect of erythritol in stainless steel cups is best.The addition of nano-C is most effective in improving the supercooling of erythritol.High-quality nanofluids can be obtained when C,Cu,and Zn O nanoparticles are added in amounts of 0.1%,0.3%,and 0.2%,respectively.Simultaneous introduction of high-concentration nanoparticles and input of high-power ultrasound,or introduction of low-concentration nanoparticles and input of lowpower ultrasound can obtain nanofluids with good crystallization.In the case of low ultrasonic energy,the nanoparticles may have a negative effect on the crystallization of the nanofluid.In addition,a UV-visible spectrophotometer was used to study the dispersion stability of nanofluids.The experimental data revealed that the relationship curves of ultrasonic power/ time-concentration-total absorbance all conformed to the quartic polynomial form.In order to further explore the stability of nanofluids,paraffin was selected as the research object.On the one hand,the best preparation scheme of CuO/paraffin nanofluid with low energy consumption and uniform dispersion was obtained,that is,the concentration is 0.1%,the ultrasonic power is 50 W,the ultrasonic time is 0.5h,and the volume is 15ml;On the other hand,the fractional factor design method was used to study the influence of five factors,including ultrasonic power and time,base fluid volume,particle concentration and type,and their coupling effects on the stability of nanofluids.And the most significant factor was found,which is the coupling effect of ultrasound power-concentration(PC).