The thermal management of power battery is important to ensure the safety of the electric vehicle. Using phase change material (PCM) coupled with liquid cooling is an efficient cooling and temperature uniformity strategy. In this study, a self-made microencapsulated PCM (MPCM) was used to prepare corresponding MPCM suspension (MPCMS) with different base liquids (water, ethanol, and silicone oil), and it was confirmed that the MPCMS-Si (MPCMS using silicone oil as base liquid) had better stability. Then, MPCMS-Si with different concentrations was prepared and the graphene was introduced to increase its heat transfer rate. Finally, the prepared suspensions were applied to the prismatic lithium-ion battery module to verify its thermal management effect. The results show that the prepared suspension's thermal conductivity, latent heat, and specific heat capacity rose with the increase in MPCM concentration. The suspensions with different mass fractions all have obvious temperature hysteresis, and the suspensions’ viscosity changed little when concentration was below 40 wt.%. Compared with the blank module, GE-MPCMS-Si can reduce the battery module temperature by 14.49 °C and reduce the temperature variance to 3.8 °C2. Besides, the influence of changing the flow rate was further investigated, 6 mL/s is the most economical and efficient flow rate option.
The carbon-coated copper nano-particles were produced by using direct current carbon arc discharge method,which average particle diameter was 25 nm.These particles were suitable for using as recycle fluids for direct absorption solar collector—— carbon-coated copper nanofluids.The composition and pattern were characterized by transmission electron microscopy(TEM) and X-ray diffraction(XRD).Ball milling dispersion was applied to prepare carbon-coated copper nanofluids.The influences of the dispersant content,ball milling time and ball milling rotational speed on the dispersive stability of the carbon-coated copper nanofluids were studied by measuring absorbance and sedimentation time.In addition,the dispersion mechanism was preliminarily dis-cussed.The results show that the optimum dispersive condition is: Gum Arabic is 0.1% in weight,ball milling time is 2 hours,and ball milling rotational speed is 250 r/min.
The copper nanofluid as cycle fluid of solar collector is prepared by ball milling dispersion process with Gum Arabic and sodium hexametaphosphate as dispersants,Ethylene Glycol aqueous solution as dispersion medium,was applied to prepare.The effects of dispersants content and ball milling time on the dispersive stability of the copper nanofluids are studied by measuring absorbance and sedimentation time.The results show that both Gum Arabic and sodium hexametaphosphate can effectively disperse the copper nanofluids into a homogeneous and stable system.The optimum dispersive condition is that the Gum Arabic mass percent is 0.25% and ball milling time is 6h,or the sodium hexametaphosphate mass percent is 0.1% and ball milling time is 2h.The dispersion mechanism of copper nanofluids with Gum Arabic is mainly resulted from steric stabilization,and the dispersion mechanism of copper nanofluids with sodium hexametaphosphate is mainly resulted from electrostatic stabilization.
Thermal switches are a type of heat control devices widely used in electronics, engineering machinery, and other applications. Electrostatically driven thermal switches (EDTS) have received wide attention due to their high specific mass density, precise control of heat flow, and flexibility. However, most of the actuating components of EDTS are made of polymers with a poor thermal conductivity, which seriously affects the effectiveness of the thermal switch. This paper presents a highly efficient, reliable, and easy-to-implement EDTS with a mini-channel cooling, which combines the convective cooling with the electrostatic actuation by adding a cooling module to the radiator. The proposed EDTS controls its ON/OFF state using the electric field, and the water is used as the cooling fluid for absorbing the heat generated from the heat source. The experimental results demonstrated that the proposed EDTS achieves a switch ratio of 2964 ± 135 and a coefficient of performance (COP) of 11.6, indicating that it can effectively regulate the heat flow in the hot path. It demonstrates the prospect of becoming widely used in the thermal management of engineering machinery and electronic devices.
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