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Abstract: Many conventional fluids have low thermal conductivities. Adding thermally conductive nanometer-sized particles to these fluids transforms them into thermally conductive nanofluids that can be used for refrigeration and air conditioning systems. In this paper, the hot disk transient plane source (TPS) method is used to explore the thermal conductivity of multi-walled carbon nanotube (MWCNT) nanofluids in a helically coiled, double-pipe heat exchanger. The thermal conductivities of the MWCNT nanofluids were measured using the thermal constants analyser TPS 2500S. Although each sample had different concentrations of MWCNT nanotubes, the nanofluids performed similarly in the TPS tests. Therefore, the helically coiled tube had an insignificant effect on the thermal conductivity of the nanofluids. Although adding MWCNT increased thermal conductivity, the high viscosity of the fluid caused a loss of heat transfer, which cancelled out the effect of the carbon nanotubes, forming an inefficient cooling medium.  

Reference: Applied Thermal Engineering, 96 (2016) 364-371

DOI: 10.1016/j.applthermaleng.2014.10.096