Geometrical Optimization of Dimpled Double-Pipe Heat Exchangers for Nanofluid-based Natural Circulation Loops Operating at Lower Temperatures

Excessive use of global energy sources causes negative environmental impacts and a reduction in the available energy resources. Therefore, energy efficiency is the main scope of engineering studies. Since household refrigeration accounts for a large portion of the energy consumption rate in buildings, several innovative techniques have been developed to improve the energy efficiency of vapor compression refrigeration systems. Suction line heat exchangers are considered one of these techniques and they are used to avoid the presence of liquid at the compressor and to prevent sweating on the suction line, as well as increasing enthalpy difference together with superheating the refrigerant at the compressor inlet. Here, a single-phase natural circulation mini loop (SPNCmL) with double pipe heat exchangers (DPHX) at cooling and heating-ends, has been proposed as an alternative to suction line heat exchangers which requires more attention to control the heat exchange process. Locating DPHXs at the low-pressure side and high-pressure sides of a conventional refrigeration cycle forms a thermal bridge with connecting these by vertical legs of the SPNCmL and provides precise control of the heat transfer with a flexible design.