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 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 ...