Assessment of thermal dispersion of elements of ship technical means of sea vessels

статья посвящена экспериментальному исследованию и оценке теплового рассеивания элементов судовых технических средств при помощи тепловизора: силиконового демпфера и водоводяного охладителя высокооборотного двигателя, дейдвудного подшипника. Для дейдвудного подшипника представлены также вибрационные параметры контроля. Применяемые в экспериментальных исследованиях переносные приборы неразрушающего контроля допущены к применению в РФ, проходят систематическую поверку и калибровку. Результаты экспериментальных исследований показывают, что при накоплении статистических данных по оценке теплового рассеивания судовых технических средств можно разработать рекомендации по нормированию и прогнозированию их состояния. Полученные экспериментальные данные могут быть предметом рассмотрения Классификационным обществом для улучшения качества наблюдения за технической эксплуатацией судовых технических средств. Доказано, что применение такого метода позволяет определить, температурное распределение в судовых технических средствах с учетом режимов эксплуатации пропульсивного комплекса и дополнить представление о техническом состоянии сочетания с другими методами контроля для оценки и прогнозирования технического состояния судовых технических средств. Накопленный опыт в проведении экспериментальных исследований контроля технического состояния безразборным методом диагностики позволит перейти от классических подходов технической эксплуатации до новых, входящих в систему удаленного контроля и управления судовых технических средств автономных судов в эксплуатации. the article is devoted to the experimental study and evaluation of the thermal dispersion of elements of ship technical means using a thermal imager: a silicone damper and a water-water cooler of a high-speed engine, a deadwood bearing. For the deadwood bearing, the vibration control parameters are also presented. Portable non-destructive testing devices used in experimental studies are approved for use in the Russian Federation, undergo systematic verification and calibration. The results of experimental studies show that with the accumulation of statistical data on the assessment of the thermal dissipation of ship technical equipment, it is possible to develop recommendations for rationing and forecasting their condition. The experimental data obtained can be the subject of consideration by the Classification Society for improving the quality of monitoring the technical operation of ship technical equipment. It is proved that the use of such a method allows us to determine the temperature distribution in ship technical means, taking into account the operating modes of the propulsive complex, and to supplement the idea of the technical condition of the combination with other control methods for assessing and predicting the technical condition of ship technical means The accumulated experience in conducting experimental studies of technical condition monitoring by the non-disassembled diagnostic method will allow us to move from classical approaches of technical operation to new ones included in the system of remote control and management of ship technical means of autonomous vessels in operation

Double-Layer Metal Foams for Further Heat Transfer Enhancement in a Channel: An Analytical Study

A local thermal non-equilibrium analysis of heat and fluid flow in a channel fully filled with aluminum foam is performed for three cases: (a) pore density of 5 PPI (pore per inch), (b) pore density of 40 PPI, and (c) two different layers of 5 and 40 PPI. The dimensionless forms of fully developed heat and fluid flow equations for the fluid phase and heat conduction equation for the solid phase are solved analytically. The effects of interfacial heat transfer coefficient and thermal dispersion conductivity are considered. Analytical expressions for temperature profile of solid and fluid phases, and also the channel Nusselt number (NuH) are obtained. The obtained results are discussed in terms of the channel-based Reynolds number (ReH) changing from 10 to 2000, and thickness ratio between the channel height and sublayers. The Nusselt number of the channel with 40 PPI is always greater than that of the 5 PPI channel. It is also greater than the channel with two-layer aluminum foams until a specific Reynolds number then the Nusselt number of the channel with two-layer aluminum foams becomes greater than the uniform channels due to the higher velocity in the outer region and considerable increase in thermal dispersion.

Investigation of transient and steady heat transfer in saturated porous medium filled in a vertical cylinder with thermal dispersion and radiation

In this study, the influence of thermal radiation and dispersion on a porous medium which was filled in a vertical cylinder was numerically solved. A finite-difference method was used to solve the non-dimensional equations by applying a Crank-Nicolson implicit numerical technique. Moreover, an experimental setup has been initially built to investigate the effect of three different grain sizes of the porous materials on the heat transfer process. The numerical results indicated that the thermal radiation increased the momentum and the thickness of the thermal boundary layer during the natural convection heat transfer process. Whereas, the thermal dispersion factor decreased the momentum and the thickness of the boundary layer during the natural convection heat transfer process, which enabled a steady and transient heat transfer. The experimental results indicated that the pore size of the medium significantly affected the rate of the heat transfer process. A smaller pore size showed a greater effect and could be used in different applications that involve a higher heat transfer rate, while a larger pore size can potentially be used as an insulating material.

Macroscale modeling of solid-liquid phase change in metal foam/paraffin composite: Effects of paraffin density treatment, thermal dispersion and interstitial heat transfer

This work focuses on macroscale modeling of solid-liquid phase change in metal foam/paraffin composite (MFPC), addressing the treatment of paraffin density (under distinct paraffin filling conditions in metal foam), thermal dispersion effect and influence of thermal diffusion dominated interstitial heat transfer. To this end, a macroscale thermal non-equilibrium model for melting in MFPC with fluid convection is developed by employing the enthalpy-porosity technique and volume averaging approach. Meanwhile, visualized experiments on melting of MFPC sample are carried out to validate the modeling results. Comparing the numerical modeling and experimental visualization results, it is found that for MFPC with an initially saturated filling condition in metal foam using solid paraffin, the varied paraffin density is preferred to be employed for developing accurate phase change model. However, for MFPC that can be just filled with liquid paraffin after melting (i.e., non-saturated filling condition using solid paraffin), Boussinesq approximation is preferred to achieve satisfying phase change simulation. Thermal dispersion effect in MFPC is proved to be negligible, which should not be overvalued to avoid inducing physical distortions of heat transfer and fluid flow. Consideration of diffusion dominated interstitial heat transfer in the thermal non-equilibrium model is vital to accurately capture phase interface evolutions as well as to reasonably simulate the mushy zone of paraffin; and the model only incorporating the convection induced interstitial heat transfer will predict quite inaccurate phase change process. This study can provide useful guidance in macroscale modeling of phase change in MFPC.