A new test section made via additive manufacturing to perform local heat flux measurements

Recent advancements in the field of additive manufacturing have enabled the realization of products that were previously almost unattainable. In the field of heat transfer, the production of heat exchangers through additive manufacturing is promising because it allows for the creation of more compact heat exchangers that can be tailored to specific requirements with optimized and complex geometries. However, also heat transfer devices that must be specifically realized for heat transfer research purposes can benefit from the characteristics of the additive manufacturing technology. This paper presents an innovative test section created through additive manufacturing technology with the aim to investigate two-phase heat transfer of refrigerants inside a 2.9 mm internal diameter channel. Water is used as a secondary fluid to reject/extract the heat. As a first step, a CFD analysis was performed to design a special geometry for the test section allowing a local measurement of the heat transfer coefficient along the channel. The test section was realized with the DMLS (Direct Metal Laser Sintering) technology using the AlSi10Mg alloy. Despite the benefits introduced by this manufacturing process, DMLS technology can lead to anisotropy in the thermal conductivity of the test section material. Thus, cylindrical samples were produced by DMLS with different building orientations to perform specific measurements of the thermal conductivity by using the Hot Disk technique. Preliminary local heat transfer coefficients were measured with refrigerant R1234ze(E) during condensation at 40 °C saturation temperature and mass flux 150 - 200 kg m−2 s−1. Experimental heat transfer results are compared against predictions obtained from a correlation available in the literature.