Published on: 01 Aug 2021

Facebook (Meta) awards Dr Chadi El Mohtar and Dr Krishna Kumar an industry researh project to improve the heat dissipation in duct banks.

The sizing of duct banks is controlled by the heat generated based on the cable’s load characteristics and the system’s ability to dissipate the heat, dictated by the thermal properties of the cable and the external environment (soil). The heat generated in the data cable has to be dissipated by transferring the heat to the surrounding soil and eventually lost to the air. As per IEC60287:1-1, when calculating the ampacity of a cable, the heat dissipation through soil is accounted for by a single thermal resistance term (T4). However, steady-state heat transfer in porous media consists of both, conduction and convection, albeit at different contributions. Based on the soil’s thermal and hydraulic characteristics, the convection process can be significant, and even dominate, resulting in major heat dissipation and a more realistic duct bank sizing.

The objective of this project is to develop a new more accurate design approach for underground duct banks and cables that can significantly reduce the construction cost and enhance their performance and durability. This objective will be achieved through an applied research approach combining a series of element scale and physical model scale laboratory investigations supplemented by numerical simulations of heat transfer from buried cable lines under a range of systematically varied soil, environmental, and design parameters.

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