Abstract
Heat transfer characteristics of copper sintered heat pipe explored using a modified graphene nanoplatelets (GNP)-containing nanofluid with great dispersion stability as a novel working fluid. Firstly, a water dispersible GNP with specific desire was synthesized by the reaction of GNP sheets with the diazonium salt (DS) of sodium 4-aminoazobenzene-4-sulfonate. An X-ray photoelectron spectroscopy (XPS) test shown successful covalent functionalization of GNP using DS which provided special water dispersibility characteristics. The results indicate that the thermal conductivity enhancement was up to 17% by adding modified GNP sheets in the base fluid. It also, exhibited a maximum sedimentation of 16% after 840 hrs. Further research works were carried on thermal performance of heat pipe by varying nanofluid concentrations, filling ratio, input heating powers and inclination angles of heat pipes. The results proof that the maximum enhancements of the effective thermal conductivity and reduction in thermal resistance for purposed nanofluid atφ = 5% were 105% and 26.4%, respectively. Moreover, these good features of the GNP/DS nanofluid make it a very promising working fluid to enhance the thermal performance and efficiency of the current heat pipe systems.
Highlights
The demand for energy saving is increasing at an enormous rate as the economy of the countries is growing
To synthesize water soluble graphene nanoplatelets (GNP), first diazonium salt (DS) was fabricated from reaction of 1.2 g of Sodium 4-aminoazobenzene-4-sulfonate with the mixture of 11 mL of distilled water (DW), 5.5 mL of HCl and 0.32 g of NaNO2 under continues stirring for 1 h in the 0 °C ice bath environment
The experimental results revealed that the DS functionalized GNP nanofluid has noticeable impact on thermal efficiency of heat pipes irrespective of inclination angle
Summary
The demand for energy saving is increasing at an enormous rate as the economy of the countries is growing. Three main components are important in the design of a heat pipe, including container materials (Some materials are more effective conductors for a heat transfer capacity than the others), the working fluid and the wick (sintered, groove and mesh). The heat pipe working fluid can be selected from different fluids, depending on its compatibility with the shell and wick material, thermal conductivity, latent heat, thermal stability, surface tension and operating temperature. The classical working fluid of heat pipes were replaced with various types of nanofluids, the transferred amount of heat can be increased due to the specific properties of nanofluids including thermal conductivity and specific heat transfer capacity [13,14,18]. Data recording system Temperature data recording Insulation method Heat pipe surface temperatures (T1- T5) Inlet and outlet temperatures (Tin and Tout)
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