scholarly journals Calculation of soil temperature at the intersection of the heating line of the underground gasket and gas pipeline taking into account real operating conditions

2021 ◽  
Vol 274 ◽  
pp. 08009
Author(s):  
Guzel Akhmerova ◽  
Ayrat Sibgatov ◽  
Roman Badrutdinov ◽  
Elza Khaziakhmetova ◽  
Rashid Maksudov
Keyword(s):  
Soil Temperature ◽  
Thermal Insulation ◽  
District Heating ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Heating Condition ◽  
Regulatory Documents ◽  
Polyethylene Pipes ◽  
Soil Temperatures ◽  
Heating Networks

Distances from the insulation shell of pipelines duringchannelless laying to utility networks are recommended by regulatory documents, but in real conditions it is not always possible to comply with these parameters. Calculations have been made to verify that the gas pipeline can be laid next to the supply pipeline of the heating network in the problematic section of the installation where these restrictions are not met. The soil temperature on the wall of the gas pipeline case is determined to exclude the heating condition of polyethylene pipes above 40 °C for the entire period of operation. Soil temperatures at the intersection of the heating line and the gas pipeline were determined taking into account the real operating conditions of the district heating networks, the peculiarities of regulating the coolant parameters of the Russian heat systems and the state of thermal insulation.

scholarly journals Pipe Hydraulic Resistances Identification of District Heating Networks Based on Matrix Analysis

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 3007
Author(s):  
Yongxin Liu ◽  
Peng Wang ◽  
Peng Luo
Keyword(s):  
Matrix Equation ◽  
District Heating ◽  
Coefficient Matrix ◽  
Operating Conditions ◽  
Adverse Impact ◽  
Matrix Analysis ◽  
Critical Step ◽  
The North ◽  
Relative Errors ◽  
Heating Networks

District heating networks (DHNs) are essential municipal infrastructure in the north of China. Obtaining accurate resistance characteristics is a critical step to improve the operating regulation level of DHNs. In this paper, pipe hydraulic resistances (PHRs) are introduced to express the resistance characteristics. A hydraulic model of a DHN can be established by using observed data of pressures and discharges. The boundary nodes are taken as observed sites. After establishing a matrix equation and analyzing the rank of its coefficient matrix, the authors propose a method to determine all the PHRs uniquely, by using a small number of observed sites and operating conditions. Furthermore, when observed errors are introduced, the adverse impact can be weakened by increasing the number of operating conditions and the accuracy of observed devices. When the observed error ranges are 1% and 0.5%, the results show that the average relative errors of identified PHRs are 2.4% and 1.1% respectively, which can be acceptable in engineering. Then, a loop DHN can be transformed into several branch DHNs, which are identified individually.

APPLICATION OF MODERN PRE-INSULATED PIPES TO INCREASE THE ENERGY EFFICIENCY OF CENTRALIZED HEAT SUPPLY SYSTEMS

2020 ◽  
Vol 42 (4) ◽  
pp. 74-82
Author(s):  
I.K. Bozhko
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Thermal Insulation ◽  
Diffusion Barrier ◽  
Thermal Characteristics ◽  
District Heating ◽  
Environmental Parameters ◽  
Heating System ◽  
District Heating System ◽  
Heating Networks

The article is devoted to a review of manufacturing technologies and methods for counteracting the effects of aging and destruction of a ball of thermal insulation in previously insulated pipes (PIP) of heating networks. The thermophysical characteristics of various blowing agents are compared; the superiority of cyclopentane in both thermophysical and environmental parameters is shown. The basic technologies for the production of pre-insulated pipe wires are considered. The advantages of «conti» technology using a diffusion barrier are highlighted. It is shown that for polyurethane foam, the main factor that suppresses heat transfer through PUR type thermal insulation is the low thermal conductivity of the gas mixture, which is "sealed" in the foam cells. The analysis of the influence of “aging” of the heat-insulating shell, namely, the diffusion of oxygen molecules into the structure of polyurethane foam, is carried out, and its negative effect on the thermal characteristics of the heat-insulating material is shown. Oxygen diffusion leads to a gradual increase in the value of the coefficient of thermal conductivity of the heat-insulating shell, and as a result, increases heat loss by the pipeline. The results of predictive calculations confirmed the effectiveness of the use of diffusion barriers in the manufacture of PIP. It is shown that when using PIP with a diffusion barrier, unproductive heat energy losses decrease on average by 20–21%, which, in turn, leads to a decrease in the amount of payments to end consumers and an increase in the quality and efficiency of district heating systems. It is also noted that polymer pre-insulated pipelines are practically not inferior in strength and reliability to steel PIP and at the same time, they have several advantages over steel PIP. It is recommended to increase the use of polymer PIP in the reconstruction of heating networks of the district heating system.

Impacts of Soil Heating Condition on Precipitation Simulations in the Weather Research and Forecasting Model

2009 ◽  
Vol 137 (7) ◽  
pp. 2263-2285 ◽  
Author(s):  
Xingang Fan
Keyword(s):  
Soil Temperature ◽  
Air Temperature ◽  
Land Surface ◽  
Lower Boundary ◽  
Land Surface Model ◽  
Surface Model ◽  
Heating Condition ◽  
Near Surface ◽  
Thermal Fields ◽  
Soil Temperatures

Soil temperature is a major variable in land surface models, representing soil energy status, storage, and transfer. It serves as an important factor indicating the underlying surface heating condition for weather and climate forecasts. This study utilizes the Weather Research and Forecasting (WRF) model to study the impacts of changes to the surface heating condition, derived from soil temperature observations, on regional weather simulations. Large cold biases are found in the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis project (ERA-40) soil temperatures as compared to observations. At the same time, a warm bias is found in the lower boundary assumption adopted by the Noah land surface model. In six heavy rain cases studied herein, observed soil temperatures are used to initialize the land surface model and to provide a lower boundary condition at the bottom of the model soil layer. By analyzing the impacts from the incorporation of observed soil temperatures, the following major conclusions are drawn: 1) A consistent increase in the ground heat flux is found during the day, when the observed soil temperatures are used to correct the cold bias present in ERA-40. Soil temperature changes introduced at the initial time maintain positive values but gradually decrease in magnitude with time. Sensible and latent heat fluxes and the moisture flux experience an increase during the first 6 h. 2) An increase in soil temperature impacts the air temperature through surface exchange, and near-surface moisture through evaporation. During the first two days, an increase in air temperature is seen across the region from the surface up to about 800 hPa (∼1450 m). The maximum near-surface air temperature increase is found to be, averaged over all cases, 0.5 K on the first day and 0.3 K on the second day. 3) The strength of the low-level jet is affected by the changes described above and also by the consequent changes in horizontal gradients of pressure and thermal fields. Thus, the three-dimensional circulation is affected, in addition to changes seen in the humidity and thermal fields and the locations and intensities of precipitating systems. 4) Overall results indicate that the incorporation of observed soil temperatures introduces a persistent soil heating condition that is favorable to convective development and, consequently, improves the simulation of precipitation.

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

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5712
Author(s):  
Matjaž Perpar ◽  
Zlatko Rek
Keyword(s):  
Thermal Conductivity ◽  
Temperature Gradient ◽  
Soil Temperature ◽  
District Heating ◽  
Leak Detection ◽  
Operating Conditions ◽  
Channel Cross Section ◽  
Soil Thermal Conductivity ◽  
Soil Temperature Gradient ◽  
Gradient Based

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.

Adapting the Existing District Heating Systems to Dynamic Operating Conditions

2015 ◽  
Vol 809-810 ◽  
pp. 688-693 ◽  
Author(s):  
Răzvan Corneliu Lefter ◽  
Daniela Popescu
Keyword(s):  
Energy Efficiency ◽  
District Heating ◽  
Point Of View ◽  
Operating Conditions ◽  
Flow Rates ◽  
Heating Systems ◽  
Operation Conditions ◽  
District Heating Systems ◽  
Dynamic Operating ◽  
Heating Networks

District heating systems operating under dynamic conditions without proper hydronic balancing is one of the causes of discomfort for heating consumers. Moreover, from the point of view of producers, unbalanced heating networks generate low energy efficiency. The study analyzes the operation conditions in three cases, on the same network: the first simulates the operating conditions of the network without balancing, the second when just balancing valves set to corresponding nominal flow rate values are used and the third when balancing valves and differential pressure controllers are used, the so-called total balancing method. Results highlight the importance of the hydraulic balancing under steady state and dynamic operating conditions, as a source to increase the energy efficiency and assure thermal comfort by better distribution of fluid flow rates between consumers.

Stress Influence Factor Analysis of Gas Pipeline in the Tunnel

2012 ◽  
Vol 204-208 ◽  
pp. 4264-4269
Author(s):  
Xiao Nan Wu ◽  
Hong Yan Ma ◽  
Ying Zhou ◽  
Mei Lin Hu ◽  
Yan Xian
Keyword(s):  
Factor Analysis ◽  
Soil Temperature ◽  
Stress Analysis ◽  
Influence Factor ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Primary Stress ◽  
Symmetrical Form ◽  
The Impact ◽  
Stress Influence

The laying of gas pipeline with tunnel crossing method, except under the influence of pressure, temperature, and out of gas direction, it also subjected to constraints of soil, soil temperature, terrain conditions and the impact of earthquakes. Also crossing pipes are in the constraints of fixed pier, anchorage pier and pier pipeline deformation, which makes the stress analysis of boundary is difficult to determine. In order to compare the effect of different constraints and out of gas direction on the entire tunnel crossing pipeline under operating conditions, this paper has established three pipe models: the symmetrical form of the direction of access to gas, completely without supporting (do not canceled the fixed pier at both ends)and with supporting form, then the primary stress, secondary stress and compound stress are checked in turn. By comparing their impact on the stress of the whole pipeline, we get the importance and extent of the main constrains on the pipeline stress.

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