Heat Dissipation Limit Research Articles

Limits to sustained energy intake. XI. A test of the heat dissipation limitation hypothesis in lactating Brandt's voles (Lasiopodomys brandtii)

The maximum rate of sustained energy intake (SusEI) may limit reproductive effort, thermoregulatory capability and other aspects of an animal's energy expenditure. Consequently, factors that limit SusEI are of interest. The ;heat dissipation limitation hypothesis' suggests that maximum SusEI during lactation is limited by the capacity to dissipate body heat generated as a by-product of processing food and producing milk. In the present study, we tested the heat dissipation limitation hypothesis in lactating Brandt's voles (Lasiopodomys brandtii). Female voles were mated and pregnant at 21(+/-1) degrees C. A random sample of animals was transferred into a hot room 30(+/-1) degrees C on the day of parturition. The energy intake of lactating voles at 30 degrees C was always lower than that at 21 degrees C. At peak lactation food intake was 3.3 g day(-1) lower at 30 degrees C than at 21 degrees C. There was no significant difference in digestibility. With similar mean litter sizes (7.26+/-0.46 pups at 21 degrees C and 7.78+/-0.39 pups at 30 degrees C at the beginning of parturition, 6.83+/-0.51 pups at 21 degrees C and 7.73+/-0.50 pups at 30 degrees C at weaning), the milk energy output of mothers, evaluated from the difference between metabolizable energy intake and daily energy expenditure measured by doubly labelled water, at 30 degrees C was 23.3 kJ day(-1) lower than that at 21 degrees C on days 14-16 of lactation. As for reproductive performance, there was a difference in the response to the higher temperature between mothers raising large and those raising small litters. For small litters (<7) there was no significant change in litter mass, but for large litters (<or=7) there was a significant decrease at the higher temperature. On average, in larger litters the pups were 15.5 g heavier on day 12 of lactation when raised at 21 degrees C. Our data from Brandt's voles support the suggestion that SusEI at peak lactation is limited by heat dissipation capacity, particularly for those voles raising large litters. In smaller litters the peripheral limitation hypothesis may be more relevant. The importance of heat dissipation limits in species raising exclusively small litters needs to be investigated.

Passive cooling assembly for flat panel displays with integrated high power components

Passive cooling of flat panel display designs with integrated high power components is investigated with the help of recently available semi-empirical and CFD based heat transfer correlations. A heat-spreader-heat-sink assembly is proposed for effective external natural convection cooling of the display panel. A flat vertical surface and plate finned heat sinks with various fin heights are considered as heat sinks in the assembly. Heat dissipation limits for both types of heat sinks are determined for various panel dimensions. It is shown that for large panels, it is feasible to use passive cooling even when integrated computer components are used in panels for demanding applications such as video games, high definition video processing and 2- D to 3-D conversion.

Effect of fur removal on the thermal conductance and energy budget in lactating Swiss mice

The limits to sustained energy intake (SusEI) are important because they determine the ceiling restricting all the competing physiological processes. A recent hypothesis is that SusEI is constrained by the capacity to dissipate heat. However some previous data for Swiss mice are inconsistent with this hypothesis. To examine the role of limits to heat dissipation on SusEI, the body temperature, thermal conductance and lactation performance were measured in dorsally shaved Swiss mice. Shaving reduces external insulation and the heat dissipation limitation hypothesis predicts such animals should be capable of eating more food and raising heavier litters. Shaved mice had a significantly higher thermal conductance and a faster reduction in body temperature following noradrenaline injection. At peak lactation, shaved mice spent more time in feeding behaviour, and increased food intake above that observed in non-shaved controls, indicating that limits on SusEI might be imposed by the capacity to dissipate heat. However, shaved females did not spend more time suckling their pups, and did not raise heavier litters, which is inconsistent with the expectations of the heat dissipation limitation hypothesis. The strong correlations between resting, feeding and suckling behaviour at peak lactation suggested that there might be a trade-off in the time distribution between the behavioural patterns. These data suggest that limits on performance may be set at different levels in different strains or species. In MF1 mice studied previously the limit on milk production imposed by maximal mammary secretion capability may lie above that for heat dissipation, hence when the latter was increased the mice produced more milk and raised heavier litters. In Swiss mice the opposite might be the case. Hence when the heat dissipation capacity was increased this did not translate into heavier litters, i.e. supporting the peripheral limitation hypothesis. Further work in a range of additional species or strains will be necessary to establish whether the more normal condition is for SusEI in animals during late lactation to be set by combined peripheral demands or by the heat dissipation capacity.

Lactating red squirrels experiencing high heat load occupy less insulated nests

The heat dissipation limit hypothesis suggests that the capacity for lactating mammals to transfer energy to their offspring through milk may be constrained by limits on heat dissipation, particularly in species that raise offspring in well-insulated nests. We tested a prediction of this hypothesis by evaluating whether lactating free-ranging red squirrels (Tamiasciurus hudsonicus) occupy less insulated nests when experiencing conditions that increase heat load. In support of the hypothesis, when climate normal ambient temperatures were warm, squirrels supporting large litter masses of furred offspring occupied nests of lower insulative value. These results support the heat dissipation limit hypothesis and suggest that free-ranging mammals may select nests based on their insulative value, not only to reduce heat loss in cold conditions but also to dissipate heat during periods of heat stress.

Parametric Studies on Dynamic Performance of Hybrid Airfoil Bearing

Airfoil bearings offer many advantages over oil-lubricated bearings, but they have reliability issues during start∕stops (wear) and limited heat dissipation capability. To address these issues, a hybrid airfoil bearing (HAFB) combining hydrodynamic airfoil bearing with hydrostatic lift was introduced previously by one of the authors of this paper. Their studies show that HAFB has superior performance compared to its hydrodynamic counterpart in load capacity and cooling performance. In this article, the bearing stiffness and damping coefficients of HAFB are calculated using a linear perturbation method developed for HAFB. Simulations showed that feed parameter and supply pressure affect the dynamic characteristics of HAFB. With an increase in either the supply pressure or the feed parameter, the rotor centers itself and hence one sees a decrease in direct stiffness. Simulations showed that the cross-coupled stiffness could be reduced by increasing either the supply pressure or the feed parameter. Direct damping showed increasing trend with the supply pressure and the feed parameter. Frequency-domain analysis of the bearing coefficients was also performed. The direct damping showed marginal changes with supply pressure but showed rapid increase with increasing excitation frequencies. The damping converged to null values for all the pressures for supersynchronous excitations. The loss in damping with high stiffness values for high frequency excitation is a typical hardening effect of gas bearings. In almost all the cases, there are rapid decreases in cross-coupled stiffness and damping and the values show converging trends in supersynchronous regime.

Limits to sustained energy intake. X. Effects of fur removal on reproductive performance in laboratory mice

The maximum rate of sustained energy intake (SusEI) may limit reproductive effort and other aspects of animal performance. We have previously suggested that lactating mice are not limited centrally by the alimentary tract or peripherally by the mammary glands, but that the limits to SusEI are imposed by the capacity of the animal to dissipate body heat generated as a by-product of processing food and producing milk. To explore the nature of the limits to SusEI, we bred MF1 laboratory mice at 21 degrees C and then dorsally shaved lactating females to reduce their external insulation and thereby elevate their capacity to dissipate body heat. These mice increased their food intake by 12.0% and assimilated on average 30.9 kJ day(-1) more energy than unshaved animals. With nearly identical mean litter sizes (11.4 pups for shaved and 11.3 pups for unshaved mice), shaved mothers exported 15.2% (22.0 kJ day(-1)) more energy as milk than control individuals. The elevated milk production of shaved mice enabled them to wean litters that were 15.4% (12.2 g) heavier than offspring produced by unshaved mice. Our results argue against central, peripheral or extrinsic limits to SusEI at peak lactation and provide strong support for the heat dissipation limit hypothesis. More generally, we see many situations where heat dissipation may be a previously unrecognised factor constraining the evolution of endothermic animals - for example, the latitudinal and altitudinal trends in clutch and litter sizes and the migration patterns of birds.

Towards a Thermal Moore's Law

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Thermal design power trends and power densities for present and future single-core microprocessors are investigated. These trends are derived based on Moore's law and scaling theory. Both active and stand-by power are discussed and accounted for in the calculations. A brief discussion of various leakage power components and their impact on the power density trends is provided. Two different lower limits of heat dissipation for irreversible logic computers that have previously appeared in the literature are discussed. These are based on the irreversibility of logic to represent one bit of information, and on the distribution of electrons to represent a bit. These limits are found to be two or more orders of magnitude lower than present-day microprocessor thermal design power trends. Further, these thermal demand trends are compared to the projected trends for the desktop product sector from the International Technology Roadmap for Semiconductors (ITRS). To evaluate the thermal impact of projected power densities, heat sink thermal resistances are calculated for a given technology target. Based on the heat sink thermal resistance trends, the evolution of a consistent air-cooling limit is predicted. One viable alternative to air-cooling, i.e., the use of high-efficiency solid-state thermoelectric coolers (TECs), is explored in detail. The impact of different parasitics on the thermoelectric figure of merit (ZT) is quantified. </para>

Microfluidic cooling of semiconductor light emission diodes

Optical properties of GaN-based light emission diode (LED) cooled with microfluidics have been studied as a function of injection currents at different water flow rates. Without cooling, the quantum efficiency of the LED emission degrades for large injection currents because of the limited heat dissipation. With microfluidic cooling, the maximum achievable injection current and the maximum light emission intensity increase with the water flow rate. Correspondingly, the red-shifts of the emission peaks are reduced in the whole range of the injection currents when the LED is cooled. Such a simple technique should also be applicable to other types of LEDs or high density LED arrays.

Embedded Digital Signal Processing Systems

With continuing progress in VLSI and ASIC technologies, digital signal processing (DSP) algorithms have continued to find great use in increasingly wide application areas. DSP has gained popularity also in embedded systems although these systems set challenging constraints for implementations. Embedded systems contain limited resources, thus embedded DSP systems must balance tradeoffs between the requirements on computational power and computational resources. Energy efficiency has been important in batterypowered devices, but nowadays also the limited heat dissipation in small devices calls for low-power consumption. Successful implementation of DSP applications in embedded systems requires tailoring, which in turn sets challenges for design methodologies. For this special issue, we received 14 submissions and a collection of seven papers was finally accepted. The special issue is opened by “Observations on power-efficiency trends in mobile communication devices,” where the authors O. Silven and K. Jyrkka analyze the power consumption in the current mobile communication devices. Several bottlenecks in the current implementation style have been identified, thus the paper provides a good motivation for the following papers. In “The Sandbridge SB3011 platform,” the authors John Glossner et al. describe a system-on-a-chip (SoC) multiprocessor targeted as a software-defined radio platform. The platform provides solutions to the challenges in future mobile devices given in the previous paper. “A shared memory module for asynchronous arrays of processors” authored byMichael J. Meeuwsen et al. considers also chip multiprocessors. The presented shared memory module can be used for interprocess communication or to increase application performance by parallelizing computation. In “Implementing a WLAN video terminal using UML and fully automated design flow” by Petri Kukkala et al., an automated design flow for multiprocessor SoC is presented. The flow is based on UML descriptions and the authors demonstrate their design flow with a design case. Programming of chip multiprocessor platforms is considered in “pn: a tool for improved derivation of process networks” by Sven Verdoolaege et al. The paper discusses conversion of sequential programs to process networks allowing optimization of communication channels and buffers. In “A SystemC-based design methodology for digital signal processing systems,” the authors Christian Haubelt et al. describe a design flow for SoC designs containing automatic design space exploration, performance evaluation, and automatic platform-based system generation. The design flow is based on SystemC descriptions and the presented tools can automatically detect the underlying model of computation. Application-specific implementations are often used to speedup certain DSP tasks in embedded systems. In “Priority-based heading one detector in H.264/AVC decoding,” the authors Ke Xu et al. consider such implementations to speed up video decoding applications. The authors present a low-power decoder implementation for context-adaptive variable length coding defined in H.264 standard.

More MIPS per slot (ATCA or not)

Embedded system designers have always had different targets and constraints from their desktop and server computing counterparts. Power management has a higher priority in embedded systems, a requirement driven either by battery life in portable devices or by heat dissipation limits in compact infrastructure equipment. Today, more than ever, power management is dictating system design and driving trends in electronic components. System architects working on communications infrastructure applications are adopting new approaches to managing power, particularly heat dissipation. One method is to build physically bigger systems, as conveyed by the advanced telecom computing architecture (advanced TCA or ATCA) specification, which can dissipate more heat. An alternative approach consists of maximising the processing power (or MIPS, million instructions per second) within stringent power dissipation limits of each board slot. Smart use of new processor features and technology is enabling low power, small form factor, low-cost and reliable systems. The article describes how chipmakers are using these methods to increase performance while keeping power consumption low.

Evaluation of Single Phase Flow in Microchannels for High Heat Flux Chip Cooling—Thermohydraulic Performance Enhancement and Fabrication Technology

The increased circuit density on today's computer chips is reaching the heat dissipation limits for air-cooling technology. The direct liquid cooling of chips is being considered as a viable alternative. This paper reviews liquid cooling with internal flow channels in terms of technological options and challenges. The possibilities presented herein indicate a four- to ten-fold increase in heat flux over the air-cooled systems. The roadmap for single-phase cooling technology is presented to identify research opportunities in meeting the cooling demands of future IC chips. The use of three-dimensional microchannels that incorporate either microstructures in the channel or grooves in the channel surfaces may lead to significant enhancements in single-phase cooling. A simplified and well-established fabrication process is described to fabricate both classes of three-dimensional microchannels. Proof-of-concept microchannels are presented to demonstrate the efficacy of the fabrication process in fabricating complex microstructures within a microchannel.

Limits to sustained energy intake. VIII. Resting metabolic rate and organ morphology of laboratory mice lactating at thermoneutrality.

We have previously shown that the food intake and milk production of MF1 laboratory mice lactating at 30 degrees C, 21 degrees C and 8 degrees C increase as temperature declines. These data suggest that mice are not limited peripherally by the capacity of the mammary glands to produce milk but are limited by the capacity of the animal to dissipate body heat generated as a by-product of food processing and milk production. Here, we measure resting metabolic rate (RMR; prior to breeding and at peak lactation) and organ morphology (at peak lactation) in MF1 mice exposed to 30 degrees C (thermoneutrality) and compare these traits with the same parameters measured previously in mice at 21 degrees C and 8 degrees C. The masses of visceral organs primarily responsible for energy flux (heart, lungs, stomach, small intestine, large intestine, liver, pancreas, spleen and kidneys) increased as temperature declined. The masses of all these organs differed between mice exposed to 8 degrees C and 21 degrees C, whereas only the masses of heart, liver and kidneys differed between mice at 21 degrees C and 30 degrees C. The increases in organ masses were paralleled by increases in RMR at peak lactation above the levels measured prior to breeding, with mice at 8 degrees C and 21 degrees C having significantly higher increases in RMR than mice at 30 degrees C (29.6 kJ day(-1), 25.5 kJ day(-1) and 8.1 kJ day(-1), respectively). The observed changes in visceral organs and RMR are consistent with both the heat dissipation and peripheral limit hypotheses. However, mice exposed to 8 degrees C had substantially larger mammary glands than mice at 21 degrees C or 30 degrees C (2.450 g, 1.115 g and 0.956 g dry mass, respectively), which argues against the peripheral limitation hypothesis and is consistent with the heat dissipation limit hypothesis. In addition, cold exposure resulted in greater masses of brown adipose tissue, white adipose tissue, pelage and tail. We discuss these changes in the context of the potential thermoregulatory benefits from use of the heat generated as a by-product of milk synthesis.

Limits to sustained energy intake. VI. Energetics of lactation in laboratory mice at thermoneutrality.

The limits to sustained energy intake are important because of their implications for reproductive output, foraging behaviour and thermoregulatory capabilities. Recent attempts to elucidate the nature of the limits to sustained energy intake have focused on peak lactation, which is the most energetically demanding period for female mammals. The hypothesis that performance of lactating animals is limited peripherally by the capacity of mammary glands to produce milk has received the most attention. However, some empirical data cannot be explained by the peripheral limitation hypothesis. Here, we present a novel hypothesis that the limits to sustained energy intake at peak lactation are imposed by the capacity of the animal to dissipate body heat generated as a by-product of processing food and producing milk. To test the heat dissipation limit hypothesis we challenged reproducing MF1 laboratory mice (N=67) with a reduced potential heat flow between the animal and the environment by exposing them to 30 degrees C (thermoneutral zone). We compared their food intake and reproductive output at peak lactation with animals studied previously at 21 degrees C (N=71) and 8 degrees C (N=15). Mice lactating at 30 degrees C had a significantly lower mean asymptotic food intake (12.4 g day(-1)) than those at 21 degrees C (23.5 g day(-1)) and 8 degrees C (28.6 g day(-1)). On average, mice at 30 degrees C raised significantly fewer (9.8) and smaller (6.1 g) pups than those at 21 degrees C (11.3 pups; 7.0 g per pup) and smaller pups than those at 8 degrees C (9.6 pups; 7.3 g per pup). Consequently, mean litter mass at 30 degrees C (56.0 g) was significantly lower than at 21 degrees C (77.1 g) and at 8 degrees C (68.7 g). The mean rate of litter mass increase at 30 degrees C (2.1 g day(-1)) was also lower than at 21 degrees C (3.1 g day(-1)). The reduced food intake and low reproductive output in mice lactating at 30 degrees C are consistent with the heat dissipation limit hypothesis.

Limits to sustained energy intake. VII. Milk energy output in laboratory mice at thermoneutrality.

The limits to sustained energy intake at peak lactation could be imposed peripherally, by the capacity of the mammary glands, or centrally, by the capacity of the animal to dissipate body heat generated as a by-product of processing food and producing milk. To distinguish between the two hypotheses, we examined milk energy output at peak lactation in MF1 laboratory mice exposed to 30 degrees C (N=12), 21 degrees C (N=10; published data) and 8 degrees C (N=10; published data). The peripheral limitation hypothesis predicts that milk energy output will remain constant at different temperatures, while the heat dissipation limit hypothesis predicts a decline in milk energy output as temperature increases. Since estimates of milk energy output in small mammals can vary depending on the calculation method used, we evaluated the milk energy output of mice (N=24) using four different methods: (1) as the difference between metabolizable energy intake and daily energy expenditure of the female, (2) from female water turnover, (3) from pup water turnover and (4) from the energy budget of the litter. We assessed these four methods by comparing their accuracy, precision and sensitivity to changes in parameters involved in the calculations. Methods 1, 3 and 4 produced similar estimates of milk energy output, while those derived from female water turnover were significantly lower and more variable. On average, mice at 30 degrees C exported significantly less energy as milk (87.7 kJ day(-1)) than mice at 21 degrees C (166.7 kJ day(-1)) and 8 degrees C (288.0 kJ day(-1)). This reduction in milk energy output at 30 degrees C was caused by a significant decline in both milk flow (20.0 g day(-1), 12.9 g day(-1) and 8.5 g day(-1) at 8 degrees C, 21 degrees C and 30 degrees C, respectively) and gross energy content of milk (14.6 kJ g(-1), 13.1 kJ g(-1) and 10.5 kJ g(-1) at 8 degrees C, 21 degrees C and 30 degrees C, respectively). Milk produced at 30 degrees C contained significantly less total solids (34.4%) than milk at 21 degrees C (40.9%) and 8 degrees C (41.5%) and significantly less fat (20.0%) than milk at 21 degrees C (26.4%) and 8 degrees C (30.3%). The reduced milk energy output in mice exposed to 30 degrees C, paralleled by their reduced food intake and low reproductive output, argues against the peripheral limitation hypothesis and provides strong support for the heat dissipation limit hypothesis.

Physiological criteria of regulating the duration of physical work with submaximal power under conditions of limited heat dissipation

The authors studied the influence of exercise with a submaximal intensity on the thermal state, gas and energy exchange, cardiovascular system, exercise capacity, and subjective status in 11 track-and-field athletes in two microclimatic regimens (temperature and relative humidity of the air 21 ± 1°C and 78 ± 3% vs. 31 ± 1°C and 80 ± 2%). The character and manifestation of functional shifts in the subjects' bodies highly depended on the conditions of heat exchange with the environment. Based on these results, the authors recommended a minimum complex of physiological criteria for regulating the duration of work with preset intensity under conditions of impeded heat dissipation.

Permanent magnet linear motors for short strokes

The use of new powerful permanent magnet materials such as neodymium-iron-boron alloys can greatly improve the performance of electrical machines. The paper analyzes the impact of their use on linear motors with particular emphasis on fast action over strokes on the order of 5 to 20 mm. Closed-form formulae, which link the travel time to the stroke and heat dissipation limit of the device, are established. These formulae are used to compare various machine configurations, some of which were devised specifically for this application. It is shown that permanent magnet linear motors feature very fast travel times, but can do so only at low duty cycles. For that reason, two-spring actuators, though not as fast for single motion are superior when higher frequencies of operation, are required.

Using a free-standing thermistor array to measure VUV emission from a tokamak plasma

A compact 15-channel bolometer array composed of discrete thermistors has been installed on the Princeton Beta Experiment tokamak. The response time, fastest for detectors with low thermal capacities, has been optimized by using ‘‘free-standing’’ detectors. The detector is supported only by thin electrical leads and no thermal substrate is employed. Overheating due to limited heat dissipation is controlled with careful detector biasing. The sensitivity is limited by the systematic errors in the model of the heat transfer from the detector to the electrodes and leads. A two-pole cooling model was found to characterize the detector’s thermal decay far better than a simple exponential and resulted in an NEP≊3×10−7 W/√Hz with a 300-Hz bandwidth.

Gaseous Metabolism and Water Relations of the Zebra Finch, Taeniopygia castanotis

Gaseous Metabolism and Water Relations of the Zebra Finch, Taeniopygia castanotis

Physikalische Grundlagen der Röntgendiagnostik

HomeRadiologyVol. 71, No. 3 PreviousNext Announcements and Book ReviewsBook ReviewsPhysikalische Grundlagen der RöntgendiagnostikPublished Online:Sep 1 1958https://doi.org/10.1148/71.3.432cMoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In AbstractBy Dr. Phil. G. Spiegler, F. Inst. P., F. R. P. S., London, England. With a Foreword by Prof. Dr. H. R. Schinz, Zurich. A volume of 94 pages, with 71 figures. Published by Georg Thieme Verlag, Herdweg 63, (14a) Stuttgart, Germany, 1957. Distributed in United States and Canada by Intercontinental Medical Book Corporation, New York, N. Y. Price DM 18.—($4.30).The author has joined the ranks of those physicists who, after exploring the field of therapy suecessfully, have turned their investigative interest toward the physical aspects of roentgen diagnosis, “the newest frontier.” The reader is asked to do likewise, for many of the complex factors in image formation are explained in terms of radiotherapy. The problems of radiographic exposure, patient absorption, absorptional contrast, scattered radiation, tube output, filters, etc., are expressed in terms of half-value layers, absorption coefficient, field size, loss and gain of depth dose by scattering, and other concepts which are mainly familiar to the radiotherapist. Even the heat dissipation and instantaneous load limit of x-ray tubes for rapid sequence exposures are likened to fractionation in radiotherapy whereby minutes of tube cooling are made equivalent to weeks of biologic recovery.In similar fashion, use is made of analogies with events occurring in our daily lives for the purpose of explaining problems of vision, contrast, sharpness, density, brightness range, blurring, motion, grid effect, superimposition of patterns, dominance of one pattern over another, and related features. Thus the text is enlivened by frequent allusions to hunting, sailing, mountain climbing, night driving, etc.The main purpose of the book is to explain the phenomena of taking and reading radiographs and not merely to present facts in a dry non-directional manner. It requires of the reader practically no prior knowledge in this field. Any radi-ologist who reads films and fluoroscopes can follow the discussion without difficulty (though he will be aided by experience in radiotherapy). The author has not, however, in his readability sacrified scientific accuracy to oversimplification; he supports most of his statements by curves, which preponderate over tables and mathematical formulae.The emphasis is on qualitative relationships of various factors to each other and on their effect upon the formation of radiographic images. Quantitative relationships are used mainly as examples to illustrate a qualitative trend. Thus the book is not intended to serve as a collection of “useful” formulae and tables. It does contain, however, some valuable observations on radiation protection, with examples of dosages (particularly those of scattered radiation).It is natural that such a treatise cannot be complete. Much has been omitted—as it appears—by intent in order to give the book didactic unity.Article HistoryPublished in print: Sept 1958 FiguresReferencesRelatedDetailsRecommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 71, No. 3 Metrics Altmetric Score PDF download

Radio Rack Cooling in Present Commercial Aircraft

Limited heat dissipation from the necessarily compact electronic equipment installations of airline aircraft has been a problem to commercial air carriers for many years. To deal with this problem, United Air Lines, in August, 1955, began equipping fleet aircraft with a forced air electronic equipment cooling system, with the following objectives: 1) improvement of electronic equipment reliability, 2) reduction of crew discomfort caused by electronic-equipment generated heat in the flight deck area, and 3) evacuation of any smoke from the flight deck area which might arise from electronic equipment failure. Observation of electronic equipment maintenance records during the subsequent transition period from convection to forced air equipment cooling shows characteristic failure rate trends which indicate the dependence of equipment reliability on operating temperature. These patterns occur independently in fleet records for the Convair 340, and DC-6 and DC-6B fleets, in time phase with the progress of conversion to forced air cooling in the fleet. These records, in conjunction with other comparative testing of forced cooled and convective cooled equipment installations indicate that forced air cooling provides an effective answer to airline equipment heat problems.