Papers by Keyword: Air Gap

Abstract: Heat treatment of concrete is used to speed up its curing. Therefore, this process allows getting complete product in a short time and it is used at the plants for manufacturing of concrete elements. Fossil fuels are used for this purpose. An important task for engineers and scientists is to reduce costs of the manufacturing and make it ecological by introducing energy-saving technologies and renewable energy resources. The employment of solar energy for heat treatment is one of the ways to settle the problem. However, the efficiency of such engineering solution depends on type and construction of the solar energy equipment. The formwork, equipped by transparent cover, is chosen as the object of research. The research work is devoted to determination of optimal thickness of air gap between concrete element and transparent cover of the formwork. The results and methodology, as well as the information about materials and boundary conditions of the experiments are given in the research work. The obtained results allow increasing efficiency of employment of solar energy for manufacturing of concrete elements at the plants.

Abstract: Poly(ethylene-co-trimethylene terephthalate) is an engineering material that has recently gained attention for use in fused filament fabrication (FFF). Although the properties of this thermoplastic are well suited for this process, the porosity of the components made remains a barrier to wider use of this approach in the additive fabrication of tight components for medical and food applications. This study investigated the effects of four tool path parameters of the FFF process – road width, air gap, layer thickness, and outer contours – on the void fraction in the structures made. It was revealed that the porosity was reduced from above 9% to below 2% when the extrusion rate was increased from initially 5.00 mm³/s to at least 5.75 mm³/s. A similar outcome was observed when a negative air gap between two adjacent strands of -15% or less was applied. In addition, these results were obtained without extending the print times. By contrast, altering the layer thickness and number of contours had only marginal or no effects on part porosity.

Abstract: The aerostatic journal bearings are widely used in ultra-precision machine tools. Due to remarkable ability of the porous medium in flow restriction, the porous aerostatic journal bearings are better than other types of aerostatic bearings in load carrying capacity, stiffness, damping and dynamic stability. The partially porous aerostatic journal bearing has the advantages of easy production and low cost. Moreover, the gap between the porous insert and the spindle can be adjusted to reduce the eccentricity due to high speed rotation. In this study, the effects of the size of the porous insert and the thickness of the air gap between the spindle and the housing on the gap pressure, the stiffness and the load carrying capability of the partially porous aerostatic journal bearing were figured out for performance evaluation.

Abstract: Water-cooled casting is a new casting process. It allows even large castings to solidify rapidly, thereby reducing segregation and grain refinement. It has drawn the attention of both domestic and foreign businesses. Heat transfer at the casting/water-cooled mold interface controls the cooling rate of the casting. During the solidification process, because of the contraction that takes place during casting, an air gap can form between the casting and the water-cooled mold. This air gap hinders heat transfer between the casting and the mold, leading to a rapid drop in the interface heat transfer coefficient (IHTC). The purpose of the present study was to assess the effects of the width of the air gap and the duration of gap formation on IHTC. During the experiment, the casting temperature curve was determined in the presence of the interface air gap, and then inverse calculation was performed using PROCAST software to determine the IHTC of casting/water-cooled mold. Results showed that, after the formation of the air gap, IHTC first exhibited a rapid decrease, followed by an increase and then another decrease; IHTC was found to decrease as gap width increased and as the duration of gap formation increased.

Abstract: The society lays stress on today's buildings, particularly in terms of energy-efficient buildings and ecology of buildings. Accordingly, not only from a technical technical point of view, it is important to give sufficient attention to the foundations of building. The popular way of foundation of lightweight buildings is due to the growing interest in timber houses the foundation above a ventilated air gap so called Crawl Space. The article deals with the temperature and humidity field which is located in the air gap under the construction of wooden building in the climatic conditions of the Czech Republic.

Abstract: This paper presents a study of thermal comfort of container for a low income flat in Jakarta. This study was conducted since the population of Jakarta is rapidly growing so that the provision of houses for inhabitants especially for low-income communities is necessary. One solution to resolve this issue is vertical housing that concern the sustainability development process; hence, the use of used container may become a suitable choice. However, the drawback of the container is made of aluminum which has high thermal conductivity and can cause poor indoor thermal comfort. This study, therefore, analysed a used container to investigate its indoor thermal comfort. In order to facilitate that objective, a simulation study was conducted. The simulation study consisted of two steps: (1) to simulate the indoor thermal comfort of the container without insulation and (2) to simulate the container after has been added by insulator materials and air gap between the materials. The results showed that by adding insulator materials and air gap as the second layer, the indoor thermal comfort can be improved up to 26%. This result is in the range of the third level of Standard National Indonesia (SNI) thermal comfort version.

Abstract: In this paper, we have developed transmitter, receiver and 2 structure magnetic resonant couplings. Both of the Transmitter and Receiver couplings are made of copper tubing. Transmitter and Receiver circuits were build by using Multisim software. Transmitter in put by DC source 12 Volt, 0.5 Ampere, with 50 cm Air gap wireless power transfer can reach efficiency 25.2 % with DC 3.02 Volt, 50.01 mA, at Frequency 164.76 kHz.

Abstract: The main function of walling system is to protect from environmental impact and to create favorable climate indoors. At the present time people use such tape of structures, such as: wall with silicate brick veneer, curtain wall system with a thin plaster layer and curtain wall system with air gap as well as without it. The results of the thermomoist calculation of enclosing structures with silicate brick veneer without air gap is presented in article. Technical guidelines for normalization of humidity conditions for data structures are provided in article. The main purpose is to calculate and to develop design consideration for realization enclosing structures with silicate brick veneer without air gap. The results of the calculation show conformity of the walling system to the required energy efficiency, hygiene and comfort standards.

Abstract: Take-up roll is a key component employed in amorphous ribbon production line. The roll should supply enough adhesion fore to take up the flying ribbon with a high speed. In this paper, a novel magnetic take-up roll (MTUR) is proposed. Optimize the structure parameters with a finite element method to obtain enough and stable magnetic adhesion force (MAF). The different simulation models are established to calculate the performances of the MTUR. A prototype of the MTUR was manufactured and tested. Experiments prove that the optimal MTUR can generate MAF to overcome the resistant force that amorphous ribbon suffering in take-up process in certain air gap range

Abstract: The article considers the problem of effective protection of the cooling tower shell using the screen with a ventilated air gap. The aim is to determine the optimal parameters of the air gap. In operation, the calculations were performed showing the effects of temperature conditions and the thickness of the gap on the aerodynamic and thermal modes of operation. The article made conclusions based on the done calculations. The optimum thickness of the gap, provided heating air inlet, which provides the ability to assimilate air moisture throughout the layer and delete it in the atmosphere, which in the future will eliminate condensation on the cold surface of a concrete shell.