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The housing of totally enclosed fan-cooled electrical machines is usually finned to maximize the heat dissipation over its surface. Complex models involving heat and fluid flow simultaneously are necessary to evaluate a single design. An optimization over a wide parameter range is, therefore, not possible. In this paper, a novel approach on how to model this particular conjugate heat transfer problem in 2-D without the help of lumped circuits is presented. The proposed method is applied to an optimization process controlled by an evolutionary algorithm. Comparative, more detailed simulations in computational fluid dynamic (CFD) verify the tendencies obtained in the optimization. In another case, the method is used to evaluate the allowable degree of engineering tolerance for a given design. Although the method does not provide results as accurate as CFD, it is very helpful to study a large parameter set and determine the CFD candidates. [ABSTRACT FROM PUBLISHER]

Abstract: Freezing process efficiency is affected by the required conditions to keep the air flow and temperature at the product surface. The objective of this work was to obtain results on comparative studies with air exhaustion and blowing using an experimental portable forced-air freezing tunnel. The device was designed to improve cooling rates inside storage room without the need for a cooling/freezing tunnel. A heterogeneity factor was proposed for air circulation evaluation and compared with convective heat transfer coefficient (h ef) values. Lower modules of heterogeneity factor values represent smaller temperature differences among samples. Comparing two different air flow processes, heterogeneity factor values were similar for regions where the cooling air could flow without obstructions. However, larger differences were observed for regions with hampered air circulation. Results indicated that the air distribution, as well as the heat transfer, occurs more uniformly around the products in the exhausting process than in the blowing system. [Copyright &y& Elsevier]

The noise produced by cooling air passing through electronics packages arises from two sources. One source is the noise of the air-moving fan of either an axial or centrifugal type. This noise may have both tonal and random components and is strongly dependent on the way that the fan is placed in the unit and on where its operation is on the fan's operating curve. Often, fans are the dominant noise sources. The flow of air produces random noise due to the turbulence generated throughout the unit. Because the turbulent airflow is also responsible for heat transfer between the components and the air stream, we can regard this part of the noise as the irreducible noise due to cooling. If fan noise were eliminated, this part of the noise would remain. There is a relation, therefore, between the irreducible noise and the cooling of the unit. But the fan noise must also be considered. The relation between total airflow related noise and cooling requirements is developed in this paper for the irreducible noise. [ABSTRACT FROM AUTHOR]

Improving cooling performance is a key factor when developing induction motors in smaller sizes with larger capacities and higher rotational speeds. Doing so, however, requires thermal analysis to discover the major parameters in the cooling design. This study investigates temperature distributions and heat transfer rates in a small, totally enclosed, fan-cooled induction motor with both numerical and experimental methods. Parametric studies show that (1) the frame is of the utmost importance in the design and (2) that cooling the motor close to stator coils is the most effective method for cooling. Quantitative analyses show the relationship between the size of the motor and the rise in coil temperature. The results from transient and steady-state experiments using a real motor show that (1) the hottest spot is in the rotor surface, and (2) the load-side surface has a higher temperature than that of the fan-side. The hottest spot in the stator coils is the outer surface of the load-side endwinding. The coil temperature is also significantly affected by the attached components of the frame, as well as the contact state between the stator iron and the frame. It is recommended that the current outer fan be redesigned to improve cooling performance. [ABSTRACT FROM AUTHOR]