The Ability of a Soil Temperature Gradient-Based Methodology to Detect Leaks from Pipelines in Buried District Heating Channels

Matjaž Perpar,Zlatko Rek

doi:10.3390/en14185712

Abstract

We carried out several numerical experiments to analyze how different boundary conditions affect the ability to detect small pipeline leaks. Our method is based on determining the soil temperature gradient above a buried district heating channel. The equivalent thermal conductivity of a wet insulation (λeq) value of 0.5 W/(m·K) was used to mimic a small water leakage. To evaluate the heat loss through the channel cross section, the heat conduction model was used for the pipe insulation, the concrete, and the soil, while the convection model was considered within the channel. The following effects were used to simulate different operating conditions: heat convection at the soil surface, leakage only from the supply or return pipe, soil height above the channel, soil thermal conductivity, and pipe diameter. With the exception of leakage only from the return pipe and low soil thermal conductivity 0.4 W/(m·K), the results showed a doubling of the soil temperature gradient when compared with the no-leakage case. This fact undoubtedly confirms the potential of the method, which is particularly suitable for leak detection in old pipelines that have priority for renovation. A key added value of this research is that the soil temperature gradient-based leak detection technique was found useful in most foreseeable DH operating situations.

Highlights

The purpose of this article is to examine the possibility of detecting small water leaks from district heating (DH) pipes in buried concrete channels under various operating conditions
We deal with the insulation condition, which is still considered a key parameter in methodologies for evaluating heat losses in DH
Minimizing losses in the DH network is an important activity to meet the requirements of the fourth-generation district heating (4GDH) concept [3]

Summary

Introduction

The purpose of this article is to examine the possibility of detecting small water leaks from district heating (DH) pipes in buried concrete channels under various operating conditions. Minimizing losses in the DH network is an important activity to meet the requirements of the fourth-generation district heating (4GDH) concept [3] Within this concept, leakage detection and elimination has been highlighted as an important measure [4]. Successful detection of small leaks and their remediation certainly helps to achieve the target value about 4% of heat losses in the network pipeline of modern district heating systems, achieved above all by the reduction of supply and return temperature [5]. According to the 4GDH concept, a reduction in heat demand and heat density leads to higher relative heat losses in the heating network [6,7] These can be reduced by reducing the supply temperature, for which well-maintained piping is a necessity. Regardless of the concept, this renovation is associated with high investment costs [9] but is important to minimize heat loss and to reduce additional pressure drops in the network

Objectives

Results

Conclusion