HOT|COOL NO.3/2021 - "Don't waste it!"

Pipe dimensions for capacities below 2,000 kW

Pipe dimensions for capacities above 2,000 kW

Figure 2: Impact of the temperature difference on the pipe dimension for a given heat transfer capacity.

we have an additional parameter at play. For dimensions below DN 200, the insulated pipe system can be optimized by incorporating both the supply and the return pipe into the same sleeve, e.g., Twin pipes. The twin-pipe concept has the benefit of reducing the trench requirement compared to two single pipes; see the right side of Figure 3. Additionally, twin pipes significantly reduce heat losses from the distribu- tion pipe network compared to a set of single pipes. This boils down to the following fact: The generally larger pipe dimen- sions required for the 5 th generation and the availability of the Twin pipe concept for the 4th generation reduce the cost-ben- efit of an uninsulated pipe network.

any user operating in a cooling mode is particularly low. The lack of regeneration from cooling leads to the pipe network being dimensioned like traditional district heating systems, from the heat source towards the end-users. The impact of the temperature difference on the required pipe size for capacities of few kilowatts to 10 megawatts is shown in Figure 2. Not particularly surprisingly, the figure shows that the lower the temperature difference, the larger the required pipe dimension is. This is important as the pipe dimension has a direct impact on the trenching cost of the network. The bigger the pipe, the bigger the trench. Secondly, the bigger the pipe is, the more costly it becomes.

All in all, these factors can effectively neutralize the cost-benefit of applying an uninsulated pipe network.

When comparing the 5 th generation with the 4 th generation,

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