Effect of Heat Source Size and Orientation on the Thermal Performance of a Wire Mesh Vapor Chamber

In contemporary densified 5G base stations, different categories of electronic components (power devices, digital ICs) dissipate different levels of heat, inducing challenges in terms of thermal segregation and temperature differences between nominally identical transmission channels. In such cases, a vapor chamber that acts as a passive two-phase heat transfer device represents a potential solution by reducing the temperatures and formation of temperature gradients across the base station. This paper presents a method to accurately determine the thermal performance of a wire mesh-type vapor chamber (56 mm x 56 mm x 3 mm) for orientation angles ranging from 0° (horizontal) to 90° (vertical), and heat source sizes of 10 mm to 20 mm. In this method, an aluminium block is configured as a calorimeter that is in contact with the centre of the vapor chamber’s evaporator, providing input powers ranging from 3 W to 60 W. One-dimensional axial conduction is assumed to occur along the calorimeter, enabling the quantification of heat flow using local temperature measurements. The thermal performance of the vapor chamber is recorded in terms of thermal resistance, R_th, which is a standard metric to measure a material’s ability to resist heat flow. For this experiment, R_th is measured between the evaporator and condenser, as a function of the range of input power levels, for different vapor chamber orientation angles: 0°, 30°, 45° and 90°. Data are obtained for heat source sizes of 10 mm, 16 mm and 20 mm. In order to validate the performance of the vapor chamber, the same tests were carried out on a copper plate (56 mm x 56 mm x 3 mm). The results show that the vapor chamber is highly isothermal at all orientations, for all heat source-sizes. The overall R_th of the vapor chamber reaches its lowest and highest values at ~0.2 K/W and ~3.2 K/W, respectively, throughout the entire experiment. These results set a foundation for the deployment of vapor chambers in densified 5G base stations, providing a solution for effective thermal extraction and isothermalisation of the structures.