Thermodynamics and Energy Conservation

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics".

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 2422

Special Issue Editor


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Guest Editor
University of Aveiro
Interests: adsorption; energy; energy conversion and storage; thermodynamics; heat pump systems; heat and mass transfer; renewable energy

Special Issue Information

Dear Colleagues,

Symmetry is present in many thermodynamic systems and can be applied to concepts such as process reversebility, energy conservation, geometry problems, and molecular symmetry. Several heat and mass transfer problems have symmetric geometries which, in addition to the prescribed boundary conditions, can usually be simplified by assuming symmetries, for example, the invariance of properties and variables, and null gradients along one or more spatial coordinates or over surface planes. In addition, dividing a complex domain into smaller symmetric subdomains is a common practice for the study of complex thermodynamic systems.

This Special Issue of Symmetry will present research in the areas of thermodynamics, heat and mass transfer and energy conservation where any type of symmetry is present or can be assumed. Investigations on the lack of symmetry in these subjects are also welcomed.

Prof. Dr. J. M. S. Dias
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

  • thermodynamics
  • heat
  • energy
  • symmetric geometry

Published Papers (1 paper)

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Research

14 pages, 4065 KiB  
Article
Formation of Thermal Lesions in Tissue and Its Optimal Control during HIFU Scanning Therapy
by Xiao Zou, Shengyou Qian, Qiaolai Tan and Hu Dong
Symmetry 2020, 12(9), 1386; https://doi.org/10.3390/sym12091386 - 19 Aug 2020
Cited by 4 | Viewed by 1781
Abstract
A high intensity focused ultrasound (HIFU) scanning approach is needed to obtain multiple treatment spots for the ablation of large volume tumors, but it will bring some problems such as longer treatment times, the inhomogeneity of temperature and thermal lesions in tissues. Although [...] Read more.
A high intensity focused ultrasound (HIFU) scanning approach is needed to obtain multiple treatment spots for the ablation of large volume tumors, but it will bring some problems such as longer treatment times, the inhomogeneity of temperature and thermal lesions in tissues. Although some optimal control methods have been proposed, it is difficult to take into account the uniformity, efficiency and entirety of thermal lesions. In this study, based on the Helmholtz equation and Pennes’ bio-heat transfer equation, a coupled acoustic-thermal field model is proposed to investigate the relationship between temperature elevation, thermal lesions and neighboring treatment spots, and to analyze the effects of the heating time and acoustic intensity on thermal lesions by the finite element method (FEM). Consequently, optimal control schemes for the heating time and acoustic intensity based on the contribution from neighboring treatment spots to thermal lesions are put forward to reduce treatment times and improve the uniformity of temperature and thermal lesions. The simulation results show that the peak historical temperature elevation on one treatment spot is related to the number, distance and time interval of its neighboring treated spots, and the thermal diffusion from the neighboring untreated spots can slow down the drop of temperature elevation after irradiation, thus both of them affect the final shape of the thermal lesions. In addition, increasing the heating time or acoustic intensity of each treatment spot can expand the overall area of thermal lesions, but it would aggravate the elevation and nonuniformity of the temperature of the treatment region. Through optimizing the heating time, the total treatment time can be reduced from 249 s by 17.4%, and the mean and variance of the peak historical temperature elevation can decrease from 44.64 °C by 13.3% and decrease from 24.6317 by 45%, respectively. While optimizing the acoustic intensity, the total treatment time remains unchanged, and the mean of the peak historical temperature elevation is reduced by 4.3 °C. Under the condition of the same thermal lesions, the optimized schemes can reduce the treatment time, lower the peak of the temperature on treatment spots, and homogenize the temperature distributions. This work is of practical significance for the optimization of a HIFU scanning therapy regimen and the evaluation of its treatment effect. Full article
(This article belongs to the Special Issue Thermodynamics and Energy Conservation)
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