An Influencing Parameters Analysis of District Heating Network Time Delays Based on the CFD Method

Abstract

With the expansion of cities, district heating (DH) networks are playing an increasingly important role. The energy consumption due to the time delay caused by the transport of the medium in the DH network is enormous, especially in large networks. The study of time delay is necessary for the operation and optimization of DH networks. Compared with previous studies of constant flow rates and ideal pipeline (without regard to branches, elbows, variable pipe diameters, etc), this paper simulates a DH network in Tianjin University, China, by establishing the actual engineering model in a Computational Fluid Dynamics (CFD) method to analyze the time delay. The CFD model has great advantages in terms of computational cost and application range compared to theoretical calculations. The peak-valley method was used to verify the correctness of the time delay simulation model. Results show that the time delay calculated by the CFD model is consistent with the actual time delay obtained from the measured data. Based on this model, the parameters that affect the time delay are furtherly analyzed. Four key parameters, including flow rate, pipe length, pipe diameter, and water supply temperature are summarized. The results show that the flow rate, pipe length and pipe diameter have a great influence on the time delay of the DH network, while the temperature has little effect on the time delay. The time delay of the DH network system has a significant impact and can provide services for optimal control of the system.

Reduction of Heat Losses in a Pre-Insulated Network Located in Central Poland by Lowering the Operating Temperature of the Water and the Use of Egg-shaped Thermal Insulation: A Case Study

“…Numerical studies of pre-insulated heating networks can be made on the basis of one-dimensional [17][18][19][20], two-dimensional [15,21], and three-dimensional [12,22] analytical or numerical models. For the purpose of this work, in order to perform numerical calculations, a calculation program of stationary two-dimensional heat conduction written in Fortran using the boundary element method was used, the verification of which was presented in References [10,14].…”

Reduction of Heat Losses Using Quadruple Heating Pre-Insulated Networks: A Case Study

“…Reduction of heat loss in heating networks can also be achieved by using thicker layers of thermal insulation or heating networks with a lower thermal conduction coefficient of thermal insulation, which is associated with a higher cost of heating networks. Heat exchange in single pre-insulated heating networks, which are the most commonly used, has been thoroughly studied [7][8][9][10][11]. Heat losses in single pre-insulated pipes can be determined using analytical methods [3,7,9,12,13] as well as using numerical methods in two-dimensional [10,12] and three-dimensional [14] problems.…”