Papers by Keyword: Boiling

Abstract: The practice shows availability of an electro plasma method polishing. The lack of a method, namely impossibility of its application for processing extended grooves and apertures is known. Creation of a special equipment and revealing of optimum modes have allowed to receive the given roughness on the named surfaces on products from cuprum.

Abstract: This study experimentally investigated two-phase flow pressure drop of propane as refrigerant in horizontal small tube. Inner diameter and length of the tube were 7.6 mm and 1.07 m, respectively. In order to get pressure drop data, the experiment was conducted in various conditions of 10 to 25 kW m^-2 heat flux, 200 to 628 kg m^-2 s^-1 mass flux, and 4.0 to 11.7°C saturation temperature. This study clearly showed the effect of heat flux, mass flux, and saturation temperature on the pressure drop of propane. This study also investigated which fluid properties gave higher effect on the frictional pressure drop due to its change over the process based on the recent experiment data. The existing pressure drop correlations were evaluated against the experimental result.

Abstract: In the present work we report the investigation of heat exchange processes at stationary boiling regime of magnetic fluid on a horizontal surface under magnetic field H ≤ 4.2 kA/m. In the presence of uniform magnetic field the specific thermal flow arriving to boiling magnetic fluid increases by 1.5 - 2 times. We offer the mechanism of magnetic field influence on heat exchange intensity in boiling magnetic fluid. The volume, shape and contact area of steam bubbles in horizontal heating surface in magnetic field is studied. The equation, connecting a specific thermal flow, magnetic field gradient and magnetic fluid magnetization in bubble boiling regime of magnetic fluid is written.

Abstract: Experimental and numerical simulation of heat transfer and flow regimes for vertical flow across horizontal tubes are presented for mass flow rate in the range 0.03 – 0.17 kg/s and heat fluxes in the range 1.07–1.35 kW/m². The tubes had a diameter of 9.75 mm and a pitch to diameter ratio of 1.85. The CFX version 14.0 from ANSYS was used to predict the flow regimes and the temperature distribution in the tube bundles. These data and the predictions from numerical simulation were compared with the data available in the literature. It is found that the circulation zone in the shell becomes bigger as the mass flow rate is increases. The flow patterns identified in this experiment are bubbly, intermittent and annular flow. These data agrees well with the published data.

Abstract: This paper studies thermal and electrochemical approaches on micro bubble generation, which have been commonly used in microelectromechanical system. The size and shape effects of micro-bubble actuators are reported in detail.The rate of bubble generation and energy conversion efficiency of the two mapproaches were compared. The micro bubble generation process of the two approaches were analyzed theoretically. By comparing with the experimental results, the micro bubble actuators were optimized.

Abstract: A numerical investigation is conducted to understand the factors of influence on a pool boiling in a micro system. The nucleation activities within microlayer were captured clearly to provide details of phase change process. Boiling curve of water under ambient pressure at 1atm is obtained, numerically, which makes good agreements with several experimental results. The effects of ambient pressure, contact angle and surface roughness on heat transfer were also studied, systematically

Abstract: A model of boiling heat transfer system was established by introducing disjoining pressure produced by three phase molecular interactions and Lie algebra analysis for a developed bubble in micro channel and simulation of chaotic movement of the obtained interface dynamic system was carried out in this paper. Experiments for 0.6 mm2 mm rectangular micro channel were carried out to obtain the pressure time serials. Power spectrum density analysis for this serials shows that the system is in chaotic state if the frequency is above 7.39Hz.The result indicates that high heat transfer performance of micro channel phase change system may relate to the characteristics of chaos.

Abstract: Nanofluids have attracted great interest from researchers worldwide because of their reported superior thermal performance and many potential applications. However, there are many controversies and inconsistencies in reported experimental results of thermal conductivity, convective heat transfer coefficient and critical heat flux of nanofluids. In this paper, two major features of nanofluids, which are boiling and convective heat transfer characteristics are presented besides critically reviewing recent research and development on these areas of nanofluids.

Abstract: An experimental study has been carried out using a tube bank representing a section of a tube bundle. The bank comprised 3 columns each of 10 stainless steel electrically heated tubes of 3mm outside diameter with pitch to diameter ratio of 1.5 in an in-line arrangement. Flow rate through the test section was controlled. Each tube in the central column was instrumented to permit determination of the tube temperature and heat flux, hence permitting calculation of the heat transfer coefficient. These tests were carried out using distilled water at nominal atmospheric pressure over a range of heat fluxes between 6 - 21 kW/m2. Results of the heat transfer tests are presented and compared with correlations used for conventionally sized bundles. Correlations developed for large tube bundle overestimate the experimental results.

Abstract: Tomago Aluminium experienced problems with the boiling of cooling water in ingot casting machines, where water splashed onto molten aluminium after mould filling. The boiling problem was particularly severe when new standard moulds were installed. This paper describes the experiments and modelling employed to analyse and identify the cause of the problem and based on the results, modifications to mould geometry were suggested. Subsequent testing in lab and field trials showed that the boiling was suppressed. The first set of modified moulds in service at Tomago Aluminium showed mould life was improved as predicted. Other issues with the modified mould design, which arose in service, are also discussed.