Preparation And Research Of Carbon-basic Material/HDPE Thermal Conductive Composites

Liquid dehumidification air conditioning system is popular due to low energyconsumption, high dehumidification efficiency and indoor air quality improvement. In thesystem, the salt solution as hygroscopic agent cause serious corrosion to the metal heatexchangers. Polymer can solve the corrosion problem of mental heat exchangers because ofits good anti-corrosion ability, light weight and easy processing. However, low thermalconductivity of polymer limit its application in heat exchange field. Therefore, high thermalconductive polymer becomes a research focus.In this study, carbon-based filler/high density polyethylene (HDPE) composites havebeen prepared by the melt processing and heat pressing method using carbon fiber (CF),graphite (G), expanded graphite (EG) and carbon nano-tube (CNT) as thermal conductivefiller, respectively. The microstructure, thermal conductivity and mechanical performances ofthe carbon-based filler/HDPE composites are characterized and measured. And the effects offiller type and content, the ratio of binary fillers were investigated on the thermal conductivityof carbon-based filler/HDPE composites.It was found that, as the filler content increases, thermal conductivities of graphite filledHDPE and expanded graphite filled HDPE show increasing trend whereas thermalconductivity of carbon fiber filler HDPE increases slightly. The enhanced heat transfer effectof different fillers is in the order of EG>G>CF under the same content of filler. In the otherhand, the mechanical performances of the as-prepared HDPE composites decrease rapidlywhen the fill content is above20wt%. Considering the thermal conductivity and themechanical performance, the optimized filler content is about20%.In addition, HDPE was blended with binary fillers (EG as main filler, CF and CNT assecondary filler respectively) to prepared binary fillers filled HDPE composites(CF/EG/HDPE composite and CNT/EG/HDPE composite). The optimized mass ratios of EGto CF and EG to CNT are in the range of9:1~5:1and5:1~3:1. Under the condition ofoptimized mass ratio, the prepared composites have2~3times thermal conductivity thanHDPE as well as high tenacity and moderate strength. By comparison, CNT/EG/HDPEcomposite has better thermal and mechanical performance.Finally, three plate heat exchangers are fabricated used pure HDPE,30wt%EG/HDPEand20wt%EG/CF/HDPE composites as matrix material, respectively. The effects of flow rateand temperature on heat transfer of these heat exchangers are also studied in detail. It was found that overall heat transfer coefficient and heat exchange efficiency of modified HDPEheat exchanger are1.5times higher than those of HDPE heat exchanger under the testedoperating condition.