Performant and Simple Numerical Modeling of District Heating Pipes with Heat Accumulation

Abstract

This paper compares approaches for accurate numerical modeling of transients in the pipe element of district heating systems. The distribution grid itself affects the heat flow dynamics of a district heating network, which subsequently governs the heat delays and entire efficiency of the distribution. For an efficient control of the network, a control system must be able to predict how “temperature waves” move through the network. This prediction must be sufficiently accurate for real-time computations of operational parameters. Future control systems may also benefit from the accumulation capabilities of pipes. In this article, the key physical phenomena affecting the transients in pipes were identified, and an efficient numerical model of aboveground district heating pipe with heat accumulation was developed. The model used analytical methods for the evaluation of source terms. Physics of heat transfer in the pipe shells was captured by one-dimensional finite element method that is based on the steady-state solution. Simple advection scheme was used for discretization of the fluid region. Method of lines and time integration was used for marching. The complexity of simulated physical phenomena was highly flexible and allowed to trade accuracy for computational time. In comparison with the very finely discretized model, highly comparable transients were obtained even for the thick accumulation wall.

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].…”

Towards Efficient and Clean Process Integration: Utilisation of Renewable Resources and Energy-Saving Technologies

“…The utilisation of an air-PCM heat exchanger in passive cooling of buildings was presented by a team from the VUT Brno Energy Institute [86]. From the same research group came the contribution presented by Kudela et al [87] stressing heat accumulation, an essential issue in district heating pipes. Leithoid et al [88] dealt with controllability and observability of heat exchanger networks, the key equipment used and studied by Heat Integration.…”

Optimization of Geometric Parameters of Thermal Insulation of Pre-Insulated Double Pipes

“…The results of the calculation of the annual emission of pollutants emitted into the air for a distance s (1) = 0.025 m can be found in Table 2 (E c E f ). The value of energy used for heat losses during the year calculated on the basis of Equations (8) and (9) equals 805.04 GJ and 863.37 GJ for s (2) = 0.03 m and s (3) = 0.035 m, respectively. Table 3 presents emission factors E f and annual emissions of pollutants emitted into the air for two distances between the supply and return pipes s (2) = 0.03 m and s (3) = 0.035 m in common circular thermal insulation.…”

“…Heating networks are the subject of many studies. Kudela et al [2] presented a complex model of heat transfer in the elements of a heating network, which can be used to accurately control district heating networks. Bennet at al.…”