Optimum Sized Air Channels for Natural Convection Cooling
14 Jun 1987-pp 573-576
TL;DR: In this paper, the authors present the optimal fin spacing for PCB:s in cabinets cooled by natural convection will depend on the pattern of air flow through the cabinet and the air flow pattern is also very important for the possibilities to improve heat dissipation with component coolers.
Abstract: Natural convection cooling is widely used for temperature control in electronic equipment. The amount of heat that can be removed is determined by three factors: the temperature difference, the cooling area and the heat transfer coefficient. Heat transfer calculations for idealized cases are relatively easy and the results of these often give a good lead for the mechanical design of electronic equipment. As it is a general desire to keep the volume of an equipment at a minimum, one of the most important aims is to maximize the heat dissipation in a volume for a given temperature difference. The optimum spacing for PCB:s in cabinets cooled by natural convection will depend on the pattern of air flow through the cabinet. The air flow pattern is also very important for the possibilities to improve heat dissipation with component coolers. The optimum fin spacing for component coolers used with natural convection will vary with many factors but is generally between 5-15 mm.
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02 Jul 2014
TL;DR: In this paper, the authors investigated the effects of a synthetic jet emanating from a heated surface, and found that the synthetic jets decreased the thermal boundary layer thickness resulting in a more effective convective heat transfer process.
Abstract: Direct impinging synthetic jets are a proven method for heat transfer enhancement, and have been subject to extensive research. However, despite the vast amount of research into direct synthetic jet impingement, there has been little research investigating the effects of a synthetic jet emanating from a heated surface, this forms the basis of the current research investigation. Both single and multiple orifices are integrated into a planar heat sink forming a synthetic jet, thus allowing the heat transfer enhancement and flow structures to be assessed. The heat transfer analysis highlighted that the multiple orifice synthetic jet resulted in the greatest heat transfer enhancements. The flow structures responsible for these enhancements were identified using a combination of flow visualisation, thermal imaging and thermal boundary layer analysis. The flow structure analysis identified that the synthetic jets decreased the thermal boundary layer thickness resulting in a more effective convective heat transfer process. Flow visualisation revealed entrainment of local air adjacent to the heated surface; this occurred from vortex roll-up at the surface of the heat sink and from the highly sheared jet flow. Furthermore, a secondary entrainment was identified which created a surface impingement effect. It is proposed that all three flow features enhance the heat transfer characteristics of the system.
2 citations
15 Oct 1989
TL;DR: In this paper, a small 1.5 kW switch-mode rectifier is developed for use in 48 V or 24 V rack power systems, which is only 143 mm wide, 260 mm high, and 250 mm deep, and weighs only 6 kg.
Abstract: A small 1.5 kW off-line switch-mode rectifier has been developed for use in 48 V or 24 V rack power systems. The convection cooled rectifier is only 143 mm wide, 260 mm high, and 250 mm deep, and weighs only 6 kg. Two-thirds of the rectifier volume is heatsink. This has been achieved by using relatively high switching frequencies, 200 to 450 kHz for the main isolating converter and 70 kHz for the sinewave input current boost converter. Sinewave input current maximizes the use of standby generator capacity and minimizes main noise injection into the telecommunication network. The switch-mode components are housed on one printed circuit board, allowing easy access to all componentry for service. All user-required adjustments are accessible via holes through the rectifier front panel and can be adjusted without removing the rectifier from the rack. >
2 citations
02 Jul 2014
TL;DR: In this article, an outdoor wireless device with two segregated heat sink structures arranged vertically within a shielded chimney structure is considered, where a primary sink is used to cool temperature sensitive components and a secondary sink for high power devices.
Abstract: Environmental standards which govern outdoor wireless equipment can stipulate stringent conditions: high solar loads (up to 1 kW/m2), ambient temperatures as high as 55°C and negligible wind speeds (0 m/s). These challenges result in restrictions on power dissipation within a given envelope, due to the limited heat transfer rates achievable with passive cooling. This paper addresses an outdoor wireless device which features two segregated heat sink structures arranged vertically within a shielded chimney structure: a primary sink to cool temperature-sensitive components; and a secondary sink for high power devices. Enhanced convective cooling of the primary sink is achieved due to the increased mass flow within the chimney generated by the secondary sink. An unshielded heat sink was examined numerically, theoretically and experimentally, to verify the applicability of the methods employed. Nusselt numbers were compared for three cases: an unshielded heat sink; a sink located at the inlet of a shield; and a primary heat sink in a segregated structure. The heat sink, when placed at the inlet of a shield three times the length of the sink, augmented the Nusselt number by an average of 64% compared to the unshielded case. The Nusselt number of the primary was found to increase proportionally with the temperature of the secondary sink, and the optimum vertical spacing between the primary and secondary sinks was found to be close to zero, provided that conductive transfer between the sinks was suppressed.
2 citations
Cites background or methods from "Optimum Sized Air Channels for Natu..."
...Equation (4) [11] is used to calculate the optimum spacing for the parallel plates of a heat sink, with equation (5) [3] applied to incorporate the influence of the base plate:...
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...Malhammer [3] built upon this correlation, incorporating the effect of the base plate on the optimum spacing....
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TL;DR: In this paper, a simple mathematical PV/T model to design the cooling system using plate-pin fin extended surface heat exchanger model is presented and a relationship between the heat dissipated and the number of fins along with its dependence on individual fin area is also developed.
Abstract: Solar photovoltaic (PV) plays a major role in the renewable energy sector in the field of power production. Production of electricity from solar PV is gaining rapid importance due to its cleaner energy production capacity and it’s adaptability to various climatic conditions. PV cells suffer noticeable drop in efficiency as their operating temperature increases beyond a certain limit. In such cases cooling of the PV cells becomes mandatory. Since the efficiencies of PV cells are in the lower range (a maximum of 18%), a highly effective, inexpensive cooling system is necessary to be employed. Air cooling provides a solution to this cause and is meant to be an better counterpart to water cooling since it overcomes the problems of water cooling such as silt formation, evaporation, soiling and reflection losses. This paper presents a simple mathematical PV/T model to design the cooling system using plate-pin fin extended surface heat exchanger model. A relationship between the heat dissipated and the number of fins along with its dependence on individual fin area is also developed. This model will provide the researchers to design their cooling system according to their PV system geometry.
Dissertation•
01 Jan 2017
TL;DR: In this article, the authors present a Table of Table of contents for the paper "Acknowledgements and acknowledgements of the authors of this paper: https://github.com/
Abstract: ................................................................................................ i Acknowledgements .............................................................................. ii Table of
References
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TL;DR: In this article, the warmeabgabe bei freier Konvektion in Luft von vertikalen quadratischen parallelen Platten of h × h cm2 im gegenseitigen Abstand b wird gemessen.
535 citations
01 Jan 1981
TL;DR: In this article, the authors developed composite relations for the variation of the heat transfer coefficient along the plate surfaces, and the mathematical development and verification of such composite relations as well as the formulation and solution of the optimizing equations for the various boundary conditions of interest constitute the core of the presentation.
Abstract: While component dissipation patterns and system operating modes vary widely, many electronic packaging configurations can be modeled by symmetrically or asymmetrically isothermal or isoflux plates. The idealized configurations are amenable to analytic optimization based on maximizing total heat transfer per unit volume or unit primary area. To achieve this anlaytic optimization, however, it is necessary to develop composite relations for the variation of the heat transfer coefficient along the plate surfaces. The mathematical development and verification of such composite relations as well as the formulation and solution of the optimizing equations for the various boundary conditions of interest constitute the core of this presentation.
481 citations
TL;DR: In this paper, the authors developed composite relations for the variation of the heat transfer coefficient along the plate surfaces, and the mathematical development and verification of such composite relations as well as the formulation and solution of the optimizing equations for the various boundary conditions of interest constitute the core of the presentation.
Abstract: While component dissipation patterns and system operating modes vary widely, many electronic packaging configurations can be modeled by symmetrically or asymmetrically isothermal or isoflux plates. The idealized configurations are amenable to analytic optimization based on maximizing total heat transfer per unit volume or unit primary area. To achieve this anlaytic optimization, however, it is necessary to develop composite relations for the variation of the heat transfer coefficient along the plate surfaces. The mathematical development and verification of such composite relations as well as the formulation and solution of the optimizing equations for the various boundary conditions of interest constitute the core of this presentation.
462 citations
01 Sep 1985
TL;DR: In this paper, the maximum surface temperature of integrated circuit packages mounted on PCBs can often lie between two analytical bounds: an upper, "asymmetric isoflux," bound based on heat transfer from just one side of the PCB and a lower, "symmetricisoflux" bound based upon identical thermal transport from both sides of each PCB.
Abstract: The simplicity and convenience of direct cooling with freely circulating air, as well as the ubiquity of such systems in the marketplace, make this the technique of choice for many thermal packaging tasks. While standard heat transfer correlations are generally unsuitable for determining the detailed thermal behavior of individual components, the maximum surface temperature of integrated circuit packages mounted on PCBs can often be shown to lie between two analytical bounds: an upper, "asymmetric isoflux," bound based on heat transfer from just one side of the PCB and a lower, "symmetric isoflux," bound based on identical thermal transport from both sides of each PCB. Following a brief review of the development and validation of the theoretical symmetric and asymmetric isoflux relations for smooth-plate channels, this study focuses on the application of the proposed bounding relations to widely and closely spaced component-carrying PCBs. Successful comparison with much of the available data demonstrates the acceptable accuracy of these analytical expressions, for all except the narrowest spacings, and their utility to the thermal designer of air-cooled PCBs.
13 citations