Hội nghị khoa học lần thứ 20 = Proceedings of the 20th scientific conference Hanoi University of technology. Phân ban. Khoa học và công nghệ nhiệt lạnh = Section. Heat engineering and refrigeration. Hanoi, 2006

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A mathemathical model of a small heat pipe and its thermal characteristics

This paper presents the characteristics of a small heat pipe. A mathematical model of a heat pipe is presented with results of calculus compared with experimental data. The maximal value of heat for a small heat pipe, the influence of title angle on temperature and maximal heat of heat pipe are presented.

A study on the combustion and pyrolysis reactions of Vietnamese coal using DSC analysis

Thermoanalytical instrument can be used to investigate several physical characterizations of coal such as moisture, volatile matter, specific heat, ash content, ash melting temperature. In this report, the combustion and pyrolysis of Vietnamese coal were studied. The volatile matter of Dien Bien coal is 15,64% and Vanh Danh coal is 5,95%. The combustion of Quang Ninh coal is heterogeneolts reaction and the combustion of Dien Bien coal is homogenous and heterogeneous process.

A study on transient heat transfer in thermal structures-method and evalustions

Energy consumption for heating and cooling of building accounts for about 30% to 70% of total energy used in offices, in households and extremely that of industrial furnaces. The energy consumption can be reduced if optimum thermal structures and suitable methods of control optimization are applied. Different methods, in order to find out optimum thermal structures and suitable methods of control optomization, for study on transient heat transfer in thermal structures are introduced.

An effectiveness study of heat-pump low temperature drying using exergy method

The report presents results that calculated characteristics of low temperature drying system on basis of exergy method. The experimental results determined characteristics of dehumidification and low temperature drying heat pump system BK - BSH 1.4 based on analyzing exergy of energy and mass processes in the system. The obtained results allow to apply, extend in order to manage and operate dehumidification and drying heat pumps at low temperature used for drying harvested agricultural products.

Applied research of fluidized bed boilers

The anide shows the research concept of fluidized bed combustor (FEC) in the Department of Heat and Refrigeration Technology, at Danang university of Technology. The research focuses on theory and application of FEC for manufacturing some products, using FE technology, such as boiler, thermo oil heater and gasification combustor using low grade solid combustibles.

Comparative combustion behaviour of gaseous fuels from the aspect of conversion from LPG to coal gas in ceramic factories

The article prents difference of characteristics of gaseous fuels before, during and after combustion of old LPG and new converted coal gas. From the analyse of gas characteristics, some estimations of effects, consequences and methods of conversion are given.

Cooling and heating storage for investment, operation and maintenance cost-cutting in heat and refrigeration equipment and systems

In this article, we analyzed and introduced some cooling and heating storage methods to reduce investment and operation cost of refrigeration and heat equipments.

Cooling and heating storage for investment, operation and maintenance cost­cutting in heat and refrigeration equipment and systems

In this article, we analyzed and introduced some cooling and heading storage methods to reduce investment and operation cost of refrigeration and heat equipments.

Design and manufacturing of heat pipe dryers for agricultural products

This article gives some informations about a new model of dryer for agricultural products, which uses heat pipes. This kind of dryer has many properties appropriating for household use.

Determining of thermal properties changing of foods in freezing process

Thermal properties of foods such as heat capacities, thermal conductivities are changed with temperature variation and other parameters. Particularly, the change of thermal properties is very large during freezing process. Determining of thermal properties of foods exactly during freezing process plays an important role not only in designing but also in control optimization of food processing and maintaining. Heat capacities and thermal conductivities depend on many factors. Thus, it is still a need to improve the appropriate values. In order to give out appropriate ways to determine their values, we carried out experimental research and compared the results obtained from experiments with other researcher's data. The experimental and theatrically predicted equation-based values of heat capacities. thermal conductivities of beef, meat and other materials in range of temperature from –30oC to 30oC are introduced in this paper.

Development of coal combustion technology in industry

This paper reviews the potential reserve and the combustibility characteristics of Vietnamese Anthracite, some advanced technical methods for improving combustibility efficiency and reducting environmental pollution. Some applied research results are also given.

Feasibility study of solar heat pipe to operate the H2O-LiBr absorption chiller-1st phase

The research project on the application of solar heat pipe to operate the H2O-LiBr absorption chiller consists of two phases. The first phase is the feasibility study by using the method of computational experiment, the second phase will focuse on the site experiment based on the design data received from the first phase. In this paper, the measured solar data, the mathematical model, the program and the results of computational experiments are presented. The results received from the first phase show that it is possible to operate the H2O-LiBr absorption chiller by using solar heat pipe in the climate condition in the South of Vietnam.

Heat and mass transfer characteristics of a cooling tower under wet and warm climate conditions

This paper presents the results of a mathematical model and an experimental research of the heat and mass transfer, particularity of cooling tower. Influence of the wet and warm climate condition, specific packed-bed, water to air flow rate ratio, water-inlet temperature et... to cooling tower had been concerned. One mathematical model was developed to describe heat and mass transfer process taking place in the cooling tower.

Heat transfer and friction characteristics of slit fin-and-tube heat exchangers

The water condensate accumulated on the surface of a fin-and-tube heat exchanger significantly affects its thermal and hydraulic performances. The purpose of this study is to investigate the effect of condensate retention on the air-side heat transfer performance and flow friction. Total 12 samples of slit and plate fin-and-tube heat exchangers with varying fin spacing and the number of tube rows are tested under dry and wet conditions. The thermal fluid measurements are made using a psychometric calorimeter. Frontal air velocity varies in the range from 0.7 m/s to 1.5 mls. Using the experimental data, heat transfer coefficients in terms of Colburnj-factors and friction factors are presented.

Investigation and applied development of dehumidification and drying technology by low temperature heat pumps in the conditions of Vietnam

This paper presents some main research and development results of a number of scientific project and prototype manufacturing contracts of low-temperature heat pums under Viet Nam hot and humid climate. Four different prototype equipment and systems were successfully designed and fabricated to dehumidify and dry vegetables and post-harvestingfood stuffs.

Method for calculating the dispersion of the refrigerant in the air for assessing the environmental risk caused by refrigerators

Our researches introduce and ability to apply the method to calculate the dispersion of the refrigerant in the air for assessing the environmental risk caused by the refrigerators by using one of the mathematical models in the environmental risk. It is the Pasquill-Gifford model apply for continuous source model and called the plume model. The method can use to calculate the dispersion of the hazard gas in the air to predict the impact of the environmental risk of the refrigerator. Result of our study can use for assessing the environmental risk or predicting the consequence of the environmental risk in using the refrigerators or hazardous chemicals.

Methods for recovering heat in the brewery

In this article, we would like to introduce some methods and equipments for recovering heat from steam slack of mash kettle, rice cooker, worl and mash kettle, and heal dicharged from refrigeralion machine.

Promoting biomass fuels based technologies for energy production in Vietnam

This paper presents major results obtained from a variety of research work in biomass combustion and gasification for energy services. Follow-up activities were also identified for promoting clean and efficient use of biomass fuels for energy production in Vietnam.

Research of heat transmission characteristics of warm clothes at the actually using condition

The report addresses some experimental research models on the heat transmission characteristic of cloth and clothes and some initial results to define impact of on the some parameters factors such as: type of material, structure, stitch, redundance, washing, humidity, coefficient of heat transport of some winter clothes structure, etc.

Research on fruit and vegetables drying with heat-pump principle for agricultural products in Vietnam

The quantity of agricultural products is increasing day by day. the demand of post-harvest processing and preserving also increases. In general. the fruit processing and preserving technique of southern provinces is limited, especially the pre-processing technique considered to be fresh and primitive. It cannot satisfy the demands of qualities as well as local preliminary treatment and this will lead to the problem that it is impossible to deliver all fresh fruits at the time of profuse crop. In order to diversify the agricultural products and enhance the product's qualities to raise the income of farmer, researching in the purpose of increasing the product qualities is an essential demand at the time being. From the real demands, we have researched on the ability of using heat-pump dryer to dry sliced fresh fruits used as the grinded materials in food processing technology. The initial research on some kinds of fruit shows: the color of dried products can be maintained. Bio-chemical analyzing results give: for bitter melon, the post-drying moist is 17.1% compared to 94.7% of pre-drying: the total protein content is well maintained, 2.08% compared to 2.42% of initial. For squashes. the total protein content is 100% maintained; the total carotene content increases from 5.99 mg/g to 24.42 mg/g and 53.34 mg/g to 188.7 mg/g of that for carrot.

Vertical brick kiln technology, success and directional development in Vietnam

This article introduces a brick kiln technology that uses economically fuel and causes less environmental pollution gasses. This kind of kiln has high thermal efficiency, low cost. Furthermore, it is flexible with a variety of products. The technology is now more and more disseminated in many provinces in Vietnam.