Applying the scalability apparatus to estimate the thermal efficiency of a single finned tube

The paper explores the possibility of scaling the integral parameters of the cooling system operation using the working elements with the length from 0.01 to 0.5 m. Numerical solution of the conjugate problem of external aeromechanics, internal hydrodynamics and heat exchange is carried out. Parametric studies of the cooling process and aerodynamic resistance of finned tubular elements of various lengths are performed. As a result of generalization and unification of the computational experimental data, a numerical coefficient has been obtained to calculate the necessary integral characteristics for a cooling element of the assigned length.

A Novel Stator Cooling Structure for Yokeless and Segmented Armature Axial Flux Machine with Heat Pipe

The yokeless and segmented armature axial flux machine is considered an excellent topology for electric vehicles application. However, its performance is severely limited by the stator cooling system. The heat pipe, as the small size, lightweight, but highly efficient passive phase-change cooling element, has been attracting more and more attention in the thermal management methods of electric motors. Therefore, the relationship between the thermal performance of the heat pipe with temperature is measured in detail through an experimental test platform in this paper. Further, a novel stator cooling structure that combines the heat pipe with the housing water-cooling method is introduced to improve the temperature distribution of the stator. Computational fluid dynamics (CFD) simulation verifies that the proposed cooling structure can accelerate the release of heat from the stator and reduce the temperature of the stator significantly.

MILK COOLING UNIT BASED ON THERMOELECTRIC MODULES

The tendency to increase the consumption of personalized nutrition opens up new prospects for the industrial production of milk from an individual cow with preserved useful components inherent in a specifi c animal species, the composition of fat, protein, lactose, and taste. A milking installation is composed of robots for individual milking of cows with automatic control of milk quality indicators. At the same time, milk corresponding to the parameters of high quality enters the thermoelectric plate-type cooler – heater, then into the packing machine, where it is bottled into containers to further proceed to the refrigerator. Thermal modules as a cooling element are chosen due to their high speed and the ability to accurately control the set temperature. At the same time, water is heated through the hot heating system of the thermal module, which is used for the technological needs of the farm. The work aims at developing and justifying the parameters of an energy-saving thermoelectric system for cooling native individual milk from a cow and heating water in milking robots for the production of personalized food products. The authors present a technological line scheme with milk cooling directly during the milking process. Analytical relationships are given for calculating the parameters of a thermoelectric cooling system according to two options – the milk fl ow rate and the parameters of the cyclic supply of one-time equal portions of milk. The proposed technology and method for milk cooling in the fl ow using thermoelectric modules as part of milking robots makes it possible to develop a new technology for the production of high-quality dairy products according to individual orders of consumers.

Modeling and Validation of the Cool Summer Microclimate Formed by Passive Cooling Elements in a Semi-Outdoor Building Space

Previous measurements (Del Rio et al. 2019) have confirmed the formation of cool summer microclimates through a combination of passive cooling elements (i.e., evaporative cooling louver, vegetation, and sunscreen) in semi-outdoor building spaces in Japan. Computational fluid dynamics (CFD) simulation is useful to understand the contribution of each element to semi-outdoor and indoor microclimates with natural ventilation, and to determine their effective combination. To date, there have not been sufficient studies on the modeling and validation for the CFD simulation of microclimates by such elements. This study demonstrates the modeling method using literature-based values and field measurements. It also demonstrates model validity by comparing the obtained results with field measurements. The results show that CFD simulation with detailed modeling of these elements can replicate vertical temperature distributions at four different positions across the semi-outdoor space and indoor space. The maximum difference in air temperature between the measurements and simulation results was 0.7–1 °C. The sensitivities of each passive cooling element on the microclimates formed in both spaces were confirmed. The watered louver condition and shorter louver–window distance were most effective in cooling both spaces. These results indicate that the modeling method could be effectively applied to assess cool microclimates and formulate a passive cooling design.

IMPROVING THE CLEANING EFFICIENCY OF THE DIESEL ENGINE PURGE AIR COOLER

In order to increase the mass of the air charge, one has to increase its density. Therefore, the density of the air may be increased by increasing the air pressure and reducing its temperature. The temperature of the purge air is being decreased in the air cooler. With the lapse of time, its performance efficiency drops due to the contaminant pollution of heat transfer elements, which as a consequence, leads to the diesel engine power reduction. The established procedure for cleaning the air cooler does not ensure a complete cleaning of heat exchangers, especially in hard-to-reach places, and manual mechanical cleaning is rather time consuming and requires engine cutoff over a protracted period of time. Thus, improving the efficiency and simplifying the complexity of the air cooler cleaning procedure is considered to be an urgent task to complete. In order to reduce those shortcomings, the modernization of the air cooler cleaning system is being considered. The upgrade being suggested involves an installation of auxiliary atomizing devices on both sides of the cooling element, i.e., in those places where the air cooler is being polluted the most. The purge air temperature increase leads to a decrease in the engine power, increased fuel consumption and accumulation of deposits in the exhaust manifold and flue pass, which consequently may contribute to a spontaneous combustion. Taking into consideration the demand for regular cleaning procedure of the cooling element, the serial system is time consuming. In addition to cleaning by means of atomizers, it also involves systematic disassembly of the cooler and manual cleaning of the elements. The modernization being suggested allows to increase the cleaning efficiency of the blower air cooler of the diesel engine by installing additional atomizers of detergent near the side surfaces of the cooling element. Modernization procedure is not a complicated one and its implementation is possible on existing vessels by the engine crew taking into account the necessity of a long-term stopover of the vessel for maintenance and repair. The solution is universal and may be implemented on ships with the gas-turbocharged engines with purge air cooling system. The application of an upgraded system will also reduce the complexity of the cleaning procedure of the air cooler cooling elements by avoiding manual mechanical cleaning of hard-to-reach cooling surfaces.

Numerical study of the effect of surface tension on the flow structure in a cylindrical vessel, taking into account the maximum density of water

A convective flow of water near the density inversion point in a cylindrical vessel, in the center of which a cylindrical cooling element is vertically located, was numerically investigated. The effect of the maximum density of water on the structure of convective flows without taking into account the surface tension and taking into account the surface tension at the upper boundary was studied. The significant effect of the surface tension at the interface between the phases(of phases) on the formation of a convective flow. The analysis of temperature and velocity fields shows that when taking into account the influence of surface tension, the convective flow of the liquid grows in intensity and average flow rates, which leads to a faster cooling of the liquid in the vessel.

The Importance of Viscous Dissipation in Micro-Tube and Micro-Gap Flows

Increasing heat flux density of modern micro-electronic devices has promoted a transition to liquid-based forced convection cooling. The miniaturization and maldistribution of micro-electronic heat generating elements (e.g. transistors and laser diodes) has promoted a similar decrease in size of cooling flow elements, specifically, micro-channels, micro-gaps and micro-jets. Convection heat transfer scaling laws do not contain a scale-factor in dimensionless form, and heat transfer coefficient (HTC) should continually increase with a decrease in size, as h∝1/d. However, extremely high HTCs are not found at tens of microns, which can be explained by the emergence of a typically neglected effect — heating by viscous dissipation. Traditionally, dissipation is only associated with high-Mach gas flows or high-viscosity oil flows. Nonetheless, it reemerges in micro-cooling, as shown here through theoretical analysis of simple cases. The extreme near-wall gradients and high L/d ratios, of these flows reintroduce dissipation as significant. When flow diameters reach a critical size, on the scale of tens of microns at Re = 2,000, depending on flow configuration, rate and liquid properties, the energy generated by dissipation is sufficient to counteract the inherent increase of HTC and the trend reverses. This maximum in HTC is the absolute lower limit to the cooling element size, a matter which has not been properly addressed. The present study lays a framework of recommendations and limitations for future cooling studies, thereby curbing the ongoing trend of flow miniaturization.

The Influences of Film Hole Size and Coolant Ejection Angle on Overall Cooling Effectiveness of Laminated Cooling

The laminated cooling or the layered cooling configuration with integrated impingement, rib-roughed and film cooling can result in a high overall cooling effectiveness and is believed to be a promising cooling technology for the next generation of advanced gas turbines. Previous studies found that the relative locations among the film hole, impingement hole and the pin-fin (i.e., cooling element arrangement) have strong impacts on the cooling effectiveness of the laminated configuration. The laminated configurations with staggered arrangement were investigated in the present paper. Two measures were used to enhance the overall cooling effectiveness, including increasing the area ratio of film hole to cooling area and employing angled film hole. Fluid-thermal coupled computations (conjugate heat transfer) were performed for assessing the overall cooling effectiveness and the pressure coefficient, and the computation method was validated by the experimental data. The computational results for the baseline design show that the area-averaged cooling effectiveness is 0.717 at BR = 1.77 and the film cooling needs to be further enhanced. Through enlarging the diameter of the film hole from 0.8mm to 1.2mm, the lift-off of film coolant is restrained and the cooling effectiveness is increased at the downstream of film hole. By employing angled film hole, the area-averaged cooling effectiveness is increased and the coolant flow resistance is also reduced.