Free Convective Cooling of Cabinets Containing Heat Dissipating Components
01 Jun 1964-Vol. 179, Iss: 1, pp 439-452
TL;DR: In this article, a theory has been developed based on the accepted heat transfer theories of Fishenden, Saunders, Weise and others, together with the results of the author's experiments.
Abstract: A theory has been developed based on the accepted heat transfer theories of Fishenden, Saunders, Weise and others, together with the results of the author's experiments. From this theory it is possible to evolve a design sheet which can be used to predict ambient temperatures within cabinets for predetermined areas of ventilation. Hence, design curves of temperature, in relation to areas of ventilation, can be obtained for specific cabinets and methods of cooling. From these curves, it should be possible to select the method of ventilation and the optimum cooling area and hence ensure that the maximum tolerable ambient temperature in which the components are required to operate shall not be exceeded.The effects on the hottest component, when the methods of ventilation are altered, the ventilating area is varied and the main heat source is progressively raised, are studied. The results of these experiments and the comparisons between predicted and observed ambient temperatures are discussed. Recommendation...
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TL;DR: The chapter summarizes analytical, numerical, and experimental work in literature, in order to facilitate the improvement of existing schemes and provide a basis for the development of new ones on the thermal control of semiconductor devices, modules, and total systems.
Abstract: Publisher Summary Thermal control of electronic components has one principal objective, to maintain relatively constant component temperature equal to or below the manufacturer's maximum specified service temperature, typically between 85 and 100°C. It is noted that even a single component operating 10°C beyond this temperature can reduce the reliability of certain systems by as much as 50%. Therefore, it is important for the new thermal control schemes to be capable of eliminating hot spots within the electronic devices, removing heat from these devices and dissipating this heat to the surrounding environment. Several strategies have developed over the years for controlling and removing the heat generated in multichip modules, which include advanced air-cooling schemes, direct cooling, and miniature thermosyphons or free-falling liquid films. The chapter summarizes analytical, numerical, and experimental work in literature, in order to facilitate the improvement of existing schemes and provide a basis for the development of new ones. The chapter focuses on investigations performed over the past decade and includes information on the thermal control of semiconductor devices, modules, and total systems.
285 citations
TL;DR: In this article, a mathematical model was developed to predict the hottest spot temperature rises in ventilated dry type transformers using test data from six layer type test windings and a 2500 kVA prototype.
Abstract: Test data indicates that hottest spot allowances used in IEEE standards for ventilated dry type transformers above 500 kVA are too low. A mathematical model to predict hottest spot temperature rises in ventilated dry type transformers was developed. Data from six layer type test windings and a 2500 kVA prototype was used to refine the model. A correlation for the local heat transfer coefficient in the cooling ducts was developed. The model was used to study the effect of various parameters on the ratio of hottest spot to average winding temperature rise. The number of conductor layers, insulation thickness, and conductor strand size were found to have only a minor effect on the ratio. Winding height was found to be the main parameter influencing. The ratio of hottest spot to average winding temperature rise. The study based on the mathematical model confirmed previous conclusions based on test data that the hottest spot allowances used in IEEE standards for ventilated dry type transformers above 500 kVA should be revised. >
58 citations
TL;DR: In this article, the authors present design criteria for free convection cooling c,f electronic systems with card spacing, channel flow restrictions, staggered cards, and baffles, respectively.
Abstract: Design criteria for free convection cooling c,f electronic systems are considered, The primary emphasis is on electronic equipment in which vertically oriented circuit cards are aligned to form vertical channels. Results of an experimental study utilizing a simulated electronic cabinet are discussed and compared with theoretical solutions obtained by numerical integration of the partial differential equations governing the heat transfer. Good agreement is shown between predicted and measured card temperatures for several different card spacings. Parametric effects on the maximum card temperature are given for card spacing, heat dissipation, and channel height. Nomograms are developed for rapid estimation of card temperatures and for choosing optimum card spacings. The effects of channel flow restrictions, staggered cards, and baffles are also discussed.
27 citations
01 Aug 1998
TL;DR: In this paper, a set of simplified equations for the thermal design of natural air-cooled electronic equipment casings has been proposed, which satisfied the demand of practical air cooling systems, since it took account of factors such as the stack effect, the air flow resistance and the heat transfer due to natural convection.
Abstract: This paper describes a practical thermal design approach to natural air-cooled electronic equipment casings. A set of simplified equations for the thermal design of natural air-cooled electronic equipment casings has been proposed. The proposed set of equations satisfied the demand of practical air-cooling systems, since it takes account of factors such as the stack effect, the air flow resistance and the heat transfer due to natural convection. The effects of the outlet area and the location of the main power supply unit on the natural cooling capability of electronic equipment casings were studied using a set of equations. The results have shown that a uniform temperature distribution could be achieved when the main power supply unit was placed at the bottom of the casing. It has also been suggested that the value of the heat removed from the casing surface could be more significant than that from the outlet vent in the thermal design of natural air-cooled electronic equipment casings.
7 citations
TL;DR: In this article, an experimental heat transfer study was performed to obtain design criteria for totally enclosed electronic equipment, and results indicated that improving exterior wall emissivity from 0.2 to 0.98 drops the temperature for both cabinet wall and internal ambient air by 25°F.
Abstract: An experimental heat-transfer study was performed to obtain design criteria for totally enclosed electronic equipment. Tests were performed on an experimental cabinet containing nine sources simulating electronic devices, and results were obtained for different distributions of source locations and heat-flux levels. Results indicate that 1) improving exterior wall emissivity from 0.2 to 0.98 drops the temperature for both cabinet wall and internal ambient air by 25°F: 2) the difference between internal ambient-air and cabinet-wall temperatures at a given power level remains nearly constant despite variations in cabinet-wall temperature; and 3) concentrating sources near the cabinet top produces extreme gradients in the local ambient while the air below remains considerably cooler whereas dissipation only in the lower levels produces near isothermal ambient temperatures throughout.
5 citations
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01 May 1956
TL;DR: A brief review of the methods of cooling electrical equipment and machines at present used in aircraft is given in this paper, where the theoretical aspects of natural and forced convective air cooling and the flow of air through machines are examined, and the limitations of forced cooling on high speed and high altitude aircraft are determined.
Abstract: A brief review is given of the methods of cooling electrical equipment and machines at present used in aircraft. Natural cooling, comprising radiation and natural convection, augmented where necessary by the use of fins, is much used, but where a greater amount of cooling is required forced convective air cooling must be employed, the air being circulated either by fan or by the use of blast air obtained from an external air intake. The theoretical aspects of natural and forced convective air cooling and the flow of air through machines are examined, and the limitations of forced cooling on high-speed and high-altitude aircraft are determined. Assuming a hot-spot temperature of 200°C, it is shown that cooling by blast air becomes inadequate at speeds in excess of about 1 000 m.h.p. owing to kinetic heating, and at altitudes in excess of about 60000ft owing to reduction of mass flow. The introduction of an efficient local cooling circuit and a blast-cooled radiator is shown to improve the altitude performance. Alternative methods of cooling to be used in the local circuit such as air at constant pressure, liquid cooling and evaporative cooling are discussed. Finally, methods of surmounting the thermal barrier so that effective cooling at very high speeds may be achieved are reviewed.
3 citations