Papers by Keyword: Heat Exchange

Abstract: Studying the temperature regimes affecting the durability of the metal wall of heat exchanger pipes helps identify ways to enhance efficiency in heat exchange processes. One of the key factors determining the temperature regime of the pipe wall is the heat transfer. One of the main factors contributing to an increase in heat transfer is the intensification of heat exchange.

Abstract: Alloy design allows to define specific compositions of materials having certain technological requirements as boundary conditions. Moreover increasing interest raised in the last decades on materials for Additive Manufacturing (AM). These new technologies consider a new approach, i.e. bottom up, for component manufacturing and suitable materials in different forms, generally liquid or solid (powders, filaments). One of the most interesting advantages of AM is the potentiality of realizing components with complex geometries and in a single or in few pieces to be assembled. For this reason, in this work a ferritic allow has been designed with the scope of realizing heat exchangers for highly corrosive alkaline environments. Water-ammonia solution are in-fact used in absorption machines for refrigeration and several heat exchangers are required for its thermodynamic cycle. After defining a specific composition, also on the base of thermodynamic simulations, the alloy has been produced by Vacuum Induction Melting (VIM). After suitable thermal treatments microstructural, mechanical and thermal characterizations have been carried out.

Abstract: Bamboo building envelope (BBE) is a kind of hygroscopic construction, making it necessary to describe the coupled heat and moisture (H&M) process accurately. In order to clarify the impact of material parameters on the H&M process of BBE, the study sets up BBE comparison model groups in WUFI Plus for annual coupled H&M process simulation, with exterior walls of 3 typical bamboos as boundary conditions and climate data of 24 Chinese representative cities as external conditions. Results quantitatively show the factor impact of hygrothermal properties parameters on the annual moisture content, heat and moisture exchange of the bamboo exterior walls, as well as the HVAC demand and indoor hygrothermal environment of the bamboo enclosed space. The simulation without liquid water-related parameters results in significant underestimation of moisture content and moisture exchange, and causes evident deviation to the heat exchange and HVAC demand. The constant valuation of thermal parameters and hygric parameters lead to deviation in heat process and moisture process of the BBE, respectively. The study highlights the moisture content-dependent bamboo hygrothermal parameters for the application of BBE.

Abstract: As a country of rich bamboo forest and large-scale bamboo processing industry, China is promoting the development of modified bamboo building materials and the bamboo construction systems. In the study on bamboo building envelope (BBE), as a hygroscopic construction, particular attention should be paid to the coupled heat and moisture (H&M) process. However, the parameters basis and the thermal design code in China could not yet support such calculation on coupled H&M process of BBE. In order to clarify the impact of meteorological parameters on the H&M process of BBE, the study prepares 24 representative cities in China with climate data exported from the Meteonorm platform and 3 typical bamboos with complete material properties data tested through experiments, and then sets up comparison BBE model groups in the software WUFI Plus for annual H&M process simulation. Statistical analysis clarifies the correlation law between the H&M process of BBE and the meteorological parameters. The study highlights the importance of hygric meteorological data for the application of BBE.

Abstract: This work focuses on the numerical investigation of different modes of heat exchangebetween the habitat and its environment in an extremely hot climate to optimize thermal comfort.Notably, to optimize habitable comfort, it is essential to model the solar flux and the temperatureabsorbed by the habitat walls. In this context, we have developed an analytical model to predict heatexchange for a habitat in the Adrar region. The heat transfer equations have been established in eachwall of the habitat. These equations were discretized by the finite difference method and solvedusing the Gauss algorithm. The models developed were validated with climatic data measured in theresearch unit ''URER'MS'' in Adrar. The results obtained showed that building materials andextreme weather conditions were the decisive parameters of unwanted overheating.

Abstract: Currently, the technological and hardware base additive production technologies are actively developing. The emergence of new developments in the field of materials science and their possibilities for the creation of products using layer-by-layer method promotes the development of innovative solutions that increase the efficiency of complex technical parts and improves their quality. This paper describes simulation methods based on the Model Voxel Representation part discretization allowing evaluating thermal processes during 3D printing process. The simulation model was extended taking into consideration the following criteria: heat conduction coefficient as a constant; temperature in the center of the elementary volume equals to the temperature at the volume border; temperature of the powder surrounding the item taken as a constant. It was determined that the convergence is affected by numerous factors: temperature in the machine chamber, material properties, heat exchange and the processes running into the chamber of the certain machines.

Abstract: The technology of transportation and storage of gas in a gas-hydrated form under atmospheric pressure and slight cooling – the maximum cooled gas-hydrated blocks of a large size covered with a layer of ice are offered. Large blocks form from pre-cooled mixture of crushed and the granulated mass of gas hydrate. The technology of forced preservation gas hydrates with ice layer under atmospheric pressure has developed to increase it stability. The dependence in dimensionless magnitudes, which describes the correlation-regressive relationship between the temperature of the surface and the center gas hydrate block under its forced preservation, had proposed to facilitate the use of research results. Technology preservation of gas hydrate blocks with the ice layer under atmospheric pressure (at the expense of the gas hydrates energy) has designed to improve their stability. Gas hydrated blocks, thus formed, can are stored and transported during a long time in converted vehicles without further cooling. The high stability of gas hydrate blocks allows to distributed in time (and geographically) the most energy expenditure operations – production and dissociation of gas hydrate. The proposed technical and technological solutions significantly reduce the level of energy and capital costs and, as a result, increase the competitiveness of the stages NGH technology (production, transportation, storage, regasification).

Abstract: The paper presents first stage of research for numerical modelling of heat exchange in counterflow shell-type system with variable dimensions, which is partly placed under the ground level. Mathematical model of heat and mass balance is reduced to 1D case to make numerical calculation faster. Different kinds of boundary conditions (surface temperature, convection) and various physical properties of layer between pipes (from non-insulated to well insulated) are used to check the usability of created model.

Abstract: The effect of high-enthalpy gas flow on transpiration cooling systems is considered. The influence of thermo-physical properties and porosity of some metals on heat transfer of the models is studied.

Abstract: This paper contains the results of research, carried out with financial support from the Ministry of Education and Science of the Russian Federation and dedicated to improving the energy efficiency of Moscow subway facilities and creation of stations with "zero" external sources heat consumption. The paper presents a method of simulation of the thermal conditions for subway tunnels, which allows, overcoming the difficulties associated with the informative uncertainty of baseline data, as well as difficulties associated with the approximation of the external parameters. Advantage of this method is the fact that the usage of so-called "base" experimentally obtained information about the natural soil thermal conditions in this model, can partially take into account the whole range of factors, which have significant influence on the formation of the thermal regime of the tunnel but are almost impossible to be taken into account within the strict formulation of the problem today.