Thermal Transients in District Heating Systems

Chertkov, Michael; Novitsky, Nikolay

doi:10.1016/j.energy.2018.01.049

Cited by 47 publications

(29 citation statements)

References 13 publications

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“…R (conv,ext) = 1 h 2 πD 2 (8) and in the case of no wind, the Churchill and Chu's correlation can be used to estimate the Nusselt number according to [17]:…”

Section: Two-dimensional Tube Modelmentioning

confidence: 99%

“…However, the transient analysis showed differences in the pure delay of temperatures within the network. On the contrary, Chertkov and Novitsky [8] have considered the dynamic/transient advection diffusion-losses equations by keeping the velocity flow steady and adjusting the temperature at the heat-producing source, thus bypassing the computationally expensive partial differential equations (PDEs) solution. An alternative to the FVM is the finite difference method (FDM).…”

Section: Introductionmentioning

confidence: 99%

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Numerical Investigation of Pipelines Modeling in Small-Scale Concentrated Solar Combined Heat and Power Plants

et al. 2020

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In this paper four different detailed models of pipelines are proposed and compared to assess the thermal losses in small-scale concentrated solar combined heat and power plants. Indeed, previous numerical analyses carried out by some of the authors have revealed the high impact of pipelines on the performance of these plants because of their thermal inertia. Hence, in this work the proposed models are firstly compared to each other for varying temperature increase and mass flow rate. Such comparison shows that the one-dimensional (1D) longitudinal model is in good agreement with the results of the more detailed two-dimensional (2D) model at any temperature gradient for heat transfer fluid velocities higher than 0.1 m/s whilst the lumped model agrees only at velocities higher than 1 m/s. Then, the 1D longitudinal model is implemented in a quasi-steady-state Simulink model of an innovative microscale concentrated solar combined heat and power plant and its performances evaluated. Compared to the results obtained using the Simscape library model of the tube, the performances of the plant show appreciable discrepancies during the winter season. Indeed, whenever the longitudinal thermal gradient of the fluid inside the pipeline is high (as at part-load conditions in winter season), the lumped model becomes inaccurate with more than 20% of deviation of the thermal losses and 30% of the organic Rankine cycle (ORC) electric energy output with respect to the 1D longitudinal model. Therefore, the analysis proves that an hybrid model able to switch from a 1D longitudinal model to a zero-dimensional (0D) model with delay based on the fluid flow rate is recommended to obtain results accurate enough whilst limiting the computational efforts.

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“…R (conv,ext) = 1 h 2 πD 2 (8) and in the case of no wind, the Churchill and Chu's correlation can be used to estimate the Nusselt number according to [17]:…”

Section: Two-dimensional Tube Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Pipelines Modeling in Small-Scale Concentrated Solar Combined Heat and Power Plants

et al. 2020

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show abstract

“…Authors of [13] focus on transients in pipes with stable mass flows. They use steady-state axial temperature distributions and convolution with the axial diffusion kernel to arrive at an explicit mathematical function that describes the temporary transient behavior.…”

Section: Introductionmentioning

confidence: 99%

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

2019

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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.

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“…In Ref. [22] Chertkov&Novitsky solve the advection-diffusion-losses equation, introduced and discussed in a setting of a single pipe.…”

Section: Introductionmentioning

confidence: 99%

Minimizing the supply temperature at the district heating plant – dynamic optimization

2019

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The constraint contains two elements, namely the heat losses and the electricity consumption for pumping at the producer. The aim was to achieve the lowest acceptable costs in an operation. The options with the supply temperature at the area starting point set to 80/60, then 60/40, and eventually 50/30 (low temperature, 4th generation district heating) were tested. The balance between the savings due to lower heat losses and the electricity consumption of pumps could be performed to assess the economic viability of the solution. This means that if the electricity price is sufficiently high, the model will always choose to minimize electricity consumption and thereby, maximise the profit from high temperature difference. Results concerning heat losses consider both experiences of proper insulation of pipes with variety of design outdoor temperatures (DOTs) and long term measurements from a pump station for district heating (DH) network in Canberra, Australia. We also noted that the heat energy tariffs and purchase price of electricity affect a lot optimal configuration of a DH system. For the best scenario, solutions are obtained that reach over 12% of the available saving potential after calculating 11 equations. Knowing that the policy is updated on a case study base, this is considered a promising result.

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Thermal Transients in District Heating Systems

Cited by 47 publications

References 13 publications

Numerical Investigation of Pipelines Modeling in Small-Scale Concentrated Solar Combined Heat and Power Plants

Numerical Investigation of Pipelines Modeling in Small-Scale Concentrated Solar Combined Heat and Power Plants

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

Minimizing the supply temperature at the district heating plant – dynamic optimization

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