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Determination of latent heats of Vaporization and fusion

Advances in Chemical Engineering and Science 2024年第3期14卷 113-124页

作者： Lahbib Abbas Lahcen Bih Khalid Yamni Abderrahim Elyahyaouy Abdelmalik El Attaoui Zahra Ramzi Chemistry Department Faculty of Science and Technology Moulay Ismail University Meknes Er-Rachidia Morocco Engineering Sciences and Professions Laboratory National School of Arts and Crafts Moulay Ismail University Meknes Meknes Morocco Materials Membranes and Nanotechnology Chemistry Department Faculty of Sciences Moulay Ismail University Meknes Zitoune Mekns Morocco Physics Department Faculty of Sciences Ibn Tofail University Kenitra Morocco Laboratory of Molecular Chemistry Materials and Environment (LCM2E) Multidisciplinary Faculty of Nador Mohamed 1st University Oujda Nador Morocco Laboratory of SCiMATOP Chemistry Department Faculty of Sciences Semlalia Cadi Ayyad University Marrakech Morocco

Water is the most abundant liquid on the surface of the earth. It is a liquid whose properties are quite surprising, both as a pure liquid and as a solvent. Water is a very cohesive liquid: its melting and vaporization temperatures are very high for a liquid that is neither ionic nor metallic, and whose molar mass is low. Thus, water remains liquid at atmospheric pressure up to 100C while similar molecules such as H2S, H2Se, H2Te for example would give a vaporization temperature close to 80C. This cohesion is in fact ensured by hydrogen bonds between water molecules. This type of bonds between neighboring molecules, hydrogen bonds, is quite often found in chemistry [1] [2]. Any change in the state of aggregation of a substance occurs with the absorption or release of a certain amount of latent heat of transformation. latent heat of fusion, vaporization or sublimation is the ratio of the energy supplied as heat to the mass of the substance that is melted, vaporized or sublimated. As a result of the reversibility of the processes, the fusion heat is equal to the heat released in the reverse process: crystallization and solidification heat. And likewise the heat of vaporization is equal to the heat of condensation. This equality of heat is often used to determine experimentally either of these quantities. There are two main measurement methods: 1) Direct measurement using the calorimeter, 2) Indirect measure based on the use of the VantHoff relationship. The objective of this work is to measure the latent heat of water vaporization and verify the compatibility of the experimental values with the values given by the tables using the indirect method.

关键词： latent heat of Vaporization latent heat of fusion Calorimetry Relationship of Vant’Hoff

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APPLICATION OF ENTHAIPY METHOD FOR MOVING BOUNDARY PROBLEM IN LASER SURFACE MELTING

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Acta Mechanica Solida Sinica 1999年第3期12卷 198-205页

作者： Wang Huicai Hong Youshi (Laboratory for Nonlinear Mechanics of Continuous Media,Institute of Mechanics,Chinese Academy of Sciences,Beijing 100080,China)

A numerical analysis was carried out to study the moving boundary problem in the physical process of pulsed Nd-YAG laser surface melting prior to *** enthalpy method was applied to solve this two-phase axisymmetrical mehing *** results of tempera ture fields were obtained,which provide useful information to practical lair treatment processing. The validity of enthalpy method in solving such problems is presented.

关键词： enthalpy method puled Nd-YAG laser Stefan problem temperature field latent heat of fusion

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Al-Si-Mg-Cu heat Storage Alloys and Their heat Storage Properties

Al-Si-Mg-Cu Heat Storage Alloys and Their Heat Storage Prope...

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中国材料大会2012

作者： Sirong Yu Jun Xu Xiaohua Zhang Qiang Yao Shumiao Xu College of Mechanical and Electronic Engineering China University of Petroleum

ISBN: (纸本)9783037856062;3037856068

The problems such as poor oxidation resistant properties at high temperatures and abated thermal storage capacities after repeated thermal cycles still exist in heat storage alloys. In order to alleviate these problems, orthogonal experiment was used to design nine Al-Si-Mg-Cu alloys in this work. An SII TG/DTA6300 differential thermal analyzer was used to determine the heat storage properties of these alloys. After integrating a series of factors, Al-12Si-2Mg-15Cu alloy was selected as the heat storage alloy. The oxidation test of this alloy at the temperature of 650℃ for 300 h was carried out, and the oxidation kinetics curve was obtained. The results showed that the oxide film was of good protection. This alloy exhibited a good thermal stability in view of the latent heat of fusion decreased 3.53%, the initial phase transition temperature decreased 0.1℃, and terminated phase transition temperature increased 3.1℃ after 150 times of thermal cycles. The photomicrograph was used to discuss the reasons of the performance changes of this alloy.

关键词： heat storage alloy latent heat of fusion Phase change temperature High temperature oxidation resistance Thermal stability

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