Summary
This article provides an extensive survey on the modelling and optimisation of district heating systems (DHSs) focused on the heat distribution network. For this purpose, the major components of a DHS have been described and discussed, and their modelling has been briefly reviewed, including numerical simulation models for heat sources, end‐users, and especially the distribution network. The main deterministic and heuristic optimisation techniques are briefly described. Additionally, a single‐objective and multiobjective optimisation problem is generally formulated, and the main optimisation criteria for the design and operation of the distribution network are synthesised and analysed. The state of the art in DHS optimisation has been also reviewed and categorised. Finally, some recommendations for future developments were included.
This work is a study of changes in coolant activity due to corrosion products of extended burn-up cycles of 18-24 months duration, in a typical pressurized water reactor, under pH and boric acid variations. It deals with non-linearly changing corrosion rates coupled with pH effects. The CPAIR-P computer program was modified to accommodate for time-dependent rising corrosion and effects of coolant chemistry. These simulations suggest that the effect of an increase in pH value for an extended 24-month cycle on a specific activity, in the form of a decrease in the said activity, is smeared by the rising corrosion. The new saturation values for activity at the end-of-cycle are lower than with a reactor operated at constant low pH/natural boric acid in the coolant. For a non-linear rise in the corrosion rate coupled with a pH rise from 6.9 to 7.4 and the use of enriched boric acid (30%-40%), coolant activity first rises to a peak value during the cycle and then approaches a much smaller saturation value at the end of the cycle, when compared with the activity for the system having a constant low pH value (6.9) in the coolant. In this work, we have shown that the use of enriched boric acid as a chemical shim actually lowers primary coolant activity when higher pH values, rather than natural boric acid, are employed in the coolant. For multiple long-term operating cycles, the saturation value of corrosion product activity increases in the first two cycles and becomes constant in subsequent ones, due to the high operational pH value for enriched boric acid (40%) as a chemical shim
A diffusion theory based MTR fuel management methodology has been developed for finding superior core loading patterns at any stage for MTR systems, keeping track of burnup of individual fuel assemblies throughout their history. It is based on using burnup dependent group constants obtained by the WIMS-D/4 computer code for standard fuel elements and control fuel elements. This methodology has been implemented in a computer program named BFMTR, which carries out detailed five group diffusion theory calculations using the CITATION code as a subroutine. The core-wide spatial flux and power profiles thus obtained are used for calculating the peak-to-average power and flux-ratios along with the available excess reactivity of the system. The fuel manager can use the BFMTR code for loading pattern optimization for maximizing the excess reactivity, keeping the peak-to-average power as well as flux-ratio within constraints. The results obtained by the BFMTR code have been found to be in good agreement with the corresponding experimental values for the equilibrium core of the Pakistan Research Reactor-1
The energy dependence on the intrinsic efficiency, absolute efficiency, full
energy peak absolute efficiency and peak-to-total ratio have been studied for
various wide band gap semiconductor detectors using the Geant4 based Monte
Carlo simulations. The detector thickness of 1-4 mm and the area in 16-100
mm2 range were considered in this work. In excellent agreement with earlier
work (Rybka et al., [20]), the Geant4 simulated values of detector
efficiencies have been found to decrease with incident g-ray energy. Both for
the detector thickness and the detector area, the increasing trends have been
observed for total efficiency as well as for full-energy peak efficiency in
0.1 MeV-50 MeV range. For Cd1-xZnxTe, the detector response remained
insensitive to changes in relative proportions of Zn. For various wide band
gap detectors studied in this work, the detection efficiency of TlBr was
found highest over the entire range of energy, followed by the HgI2, CdTe,
and then by CZT.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.