The Experts below are selected from a list of 21210 Experts worldwide ranked by ideXlab platform
Jukka P. Pekola - One of the best experts on this subject based on the ideXlab platform.
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High-performance Electronic Cooling with superconducting tunnel junctions
Comptes Rendus Physique, 2016Co-Authors: Hervé Courtois, Hung Nguyen, Clemens Winkelmann, Jukka P. PekolaAbstract:Abstract When biased at a voltage just below a superconductor's energy gap, a tunnel junction between this superconductor and a normal metal cools the latter. While the study of such devices has long been focused to structures of submicron size and consequently Cooling power in the picowatt range, we have led a thorough study of devices with a large Cooling power up to the nanowatt range. Here we describe how their performance can be optimized by using a quasi-particle drain and tuning the Cooling junctions' tunnel barrier.
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Sub-50-mK Electronic Cooling with Large-Area Superconducting Tunnel Junctions
Physical Review Applied, 2014Co-Authors: Hung Nguyen, Matthias Meschke, Hervé Courtois, Jukka P. PekolaAbstract:In Electronic Cooling with superconducting tunnel junctions, the Cooling power is counterbalanced by the interaction with phonons and by the heat flow from the overheated leads. We study aluminium based coolers that are equipped with a suspended normal metal and an efficient quasi-particle drain. At intermediate temperatures, the phonon bath of the suspended normal metal is cooled. At lower temperatures, by adjusting the junction transparency, we control the injection current, and thus the superconductor temperature. The device shows a strong Cooling from 150 mK down to about 30 mK, a factor of five in temperature. We suggest that spatial non-uniformity in the superconductor gap limits the Cooling toward lower temperatures.
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Electronic Cooling of a submicron-sized metallic beam
Applied Physics Letters, 2009Co-Authors: Juha Muhonen, Antti O. Niskanen, Matthias Meschke, Y.-u. A. Pashkin, Jaw-shen Tsai, L. Sainiemi, Sami Franssila, Jukka P. PekolaAbstract:We demonstrate Electronic Cooling of a suspended AuPd island using superconductor-insulator-normal metal tunnel junctions. This was achieved by developing a simple fabrication method for reliably releasing narrow submicron-sized metal beams. The process is based on reactive ion etching and uses a conducting substrate to avoid charge-up damage and is compatible with, e.g., conventional e-beam lithography, shadow-angle metal deposition, and oxide tunnel junctions. The devices function well and exhibit clear Cooling, up to a factor of 2 at sub-Kelvin temperatures.
Tilak T Chandratilleke - One of the best experts on this subject based on the ideXlab platform.
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A synthetic jet heat sink with cross-flow for Electronic Cooling
2013 14th International Conference on Electronic Packaging Technology, 2013Co-Authors: Tilak T Chandratilleke, Dibakar RakshitAbstract:This paper presents an investigation on the operational characteristics and thermal effectiveness of a pulsed (or synthetic) jet mechanism that periodically cools at a heated surface while acting in cross-flow fluid stream. The study uses a test rig having a variable-frequency pulsed air jet impinging at a heated surface that emulates an Electronic device to be cooled. The Cooling characteristics of the jet are observed over a wide parametric range. The results show that the pulsed jet mechanism delivers outstanding Cooling performance that is primarily dependent on the jet-impinging distance and operating frequency. Without cross flow, the pulsed jet provides about 11 K temperature reduction and 7 times more heat removal rate compared to natural convection at the heated surface. The jet impingement height indicates a strong dependency with an optimum on the heat removal rate. With cross-flow fluid stream, the pulsed jet Cooling is enhanced. This combined fluid action achieves about 13 K temperature drop and delivers 2.2 times more Cooling compare to pulsed jet operating alone. The pulsed jet operation is numerically simulated to understand the associated flow characteristics leading to thermal enhancement. It is recognised that the pulsed jet arrangement has the unique surface Cooling ability without additional fluid circuits, making it particularly desirable for high-capacity Electronic Cooling applications.
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Thermal performance evaluation of a synthetic jet heat sink for Electronic Cooling
2011 IEEE 13th Electronics Packaging Technology Conference, 2011Co-Authors: Tilak T Chandratilleke, Radhika Narayanaswamy, D JagannathaAbstract:This paper presents a performance investigation on a highly effective heat removal technique for heat sinks in Electronic Cooling applications. This arrangement utilises a pulsating fluid jet mechanism known as synthetic jet, which is characterised by zero net fluid discharge through the jet orifice. The study uses an experimental rig comprising a high-frequency pulsating air jet that impinges on a heated surface to emulate the heat sink operation attached to an Electronic device. The Cooling characteristics of this jet are examined for a range of parametric conditions, including jet-impinging distance while evaluating the heat removal rates. The results indicate that the pulsating jet produces outstanding Cooling performance at the heated surface with significant dependency of it on the jet-impinging distance. The study also assesses the interaction of a cross-flow fluid stream on the pulsed jet operation. It is observed that the cross-flow somewhat impedes the pulsed jet thermal performance. However, the pulsed jet, with or without cross flow, delivers an overall Cooling ability that supersedes the standard flow-through heat sink performance. This technique provides highly enhanced surface Cooling potential without incurring increased fluid pressure drop or requiring additional fluid circuit, which are significant advantages for high-powered heat sink design.
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Analysis of a Synthetic Jet-Based Electronic Cooling Module
Numerical Heat Transfer Part A: Applications, 2009Co-Authors: D Jagannatha, Ramesh Narayanaswamy, Tilak T ChandratillekeAbstract:This article presents a numerical study of an Electronic Cooling module using a periodic jet flow at an orifice with net zero mass flux, known as a synthetic jet. The two-dimensional time-dependant numerical simulation models the unsteady synthetic jet behavior, the flow within the cavity and the diaphragm movement while accounting for fluid turbulence using the shear-stress-transport (SST) k-ω turbulence model. Computations are performed for a selected range of parameters and the boundary conditions to obtain the heat and fluid flow characteristics of the entire synthetic jet module. The numerical simulation aptly predicts the sequential formation of the synthetic jet and its intrinsic vortex shedding process while accurately illustrating the flow within the cavity. It is indicated that the thermal performance of the synthetic jet is highly dependant on the oscillating diaphragm amplitude and frequency. At the heated surface, this jet impingement mechanism produces a very intense localized periodic cooli...
Guanming Huang - One of the best experts on this subject based on the ideXlab platform.
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Thermoelectric cooler application in Electronic Cooling
Applied Thermal Engineering, 2004Co-Authors: Reiyu Chein, Guanming HuangAbstract:Abstract This study addresses thermoelectric cooler (TEC) applications in the Electronic Cooling. The cold side temperature (Tc) and temperature difference between TEC cold and hot sides (ΔT=Th−Tc, Th=temperature of hot side of TEC) were used as the parameters. The Cooling capacity, junction temperature, coefficient of performance (COP) of TEC and the required heat sink thermal resistance at the TEC hot side were computed. The results indicated that the Cooling capacity could be increased as Tc increased and ΔT was reduced. The maximum Cooling capacity and chip junction temperature obtained were 207 W and 88 °C, respectively. The required heat sink thermal resistance on TEC hot side was 0.054 °C/W. Larger Cooling capacity and higher COP could be obtained when the TEC was operated in the enforced regimes (ΔT
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Thermoelectric cooler application in Electronic Cooling
Applied Thermal Engineering, 2004Co-Authors: Reiyu Chein, Guanming HuangAbstract:This study addresses thermoelectric cooler (TEC) applications in the Electronic Cooling. The cold side temperature (T(c)) and temperature difference between TEC cold and hot sides (DeltaT=T(h)-T(c), T(h)=temperature of hot side of TEC) were used as the parameters. The Cooling capacity, junction temperature, coefficient of performance (COP) of TEC and the required heat sink thermal resistance at the TEC hot side were computed. The results indicated that the Cooling capacity could be increased as T(c) increased and DeltaT was reduced. The maximum Cooling capacity and chip junction temperature obtained were 207 W and 88 degreesC, respectively. The required heat sink thermal resistance on TEC hot side was 0.054degreesC/W. Larger Cooling capacity and higher COP could be obtained when the TEC was operated in the enforced regimes (DeltaT
Sih-li Chen - One of the best experts on this subject based on the ideXlab platform.
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Bubble pump in a closed-loop system for Electronic Cooling
Applied Thermal Engineering, 2013Co-Authors: Sy-chi Kuo, Chih-chung Chang, Chao-chi Shih, Sih-li ChenAbstract:Abstract This study experimentally and theoretically investigates bubble pump performance in a closed-loop system for Electronic Cooling. The system consists of a vertical flat evaporator acting as a bubble pump, a condenser, a rising tube, a falling tube and a reservoir, and is completely filled with working fluid. As the bubble pump absorbs heat, the differences in the working fluid density between the rising and falling tubes induce flow motion. The effects of the input heating power, the pump inlet temperature and the boiling surfaces are determined experimentally. There are three heat-transfer regions inside the pump, including natural convection, subcooled boiling and saturated boiling. A theoretical pressure drop model and a thermal resistance network are constructed to describe the performance of the bubble pump. The results indicate that the bubble pump performs better at saturated boiling conditions. When the pump inlet temperature is the saturated temperature, the maximum flow rate is 200 ml/min at 30 W and the maximum driving pressure of the pump is 962 Pa at 80 W. The results also show that the sudden contraction between the pump and the rising tube, inducing a pressure drop, will reduce the system flow rate. In addition, the results demonstrate that the fins on the boiling surface can effectively diminish the center temperature of the basic plate of the pump and of pump resistance.
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heat pipe with pcm for Electronic Cooling
Applied Energy, 2011Co-Authors: Yingche Weng, Chih-chung Chang, Sih-li ChenAbstract:This article experimentally investigates the thermal performances of a heat pipe with phase change material for Electronic Cooling. The adiabatic section of heat pipe is covered by a storage container with phase change material (PCM), which can store and release thermal energy depending upon the heating powers of evaporator and fan speeds of condenser. Experimental investigations are conducted to obtain the system temperature distributions from the charge, discharge and simultaneous charge/discharge performance tests. The parameters in this study include three kinds of PCMs, different filling PCM volumes, fan speeds, and heating powers in the PCM Cooling module. The Cooling module with tricosane as PCM can save 46% of the fan power consumption compared with the traditional heat pipe.
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Two-Phase Closed-Loop Thermosyphon for Electronic Cooling
Experimental Heat Transfer, 2010Co-Authors: Chih-chung Chang, Sy-chi Kuo, Sih-li ChenAbstract:This study experimentally investigated the thermal performance of a two-phase closed-loop thermosyphon with a thermal resistance model for Electronic Cooling. The evaporator, rising tube, condenser, and falling tube, which are the four main devices, formed a closed-loop system with water as the working fluid. The experimental parameters were the evaporator surface type, fill ratio of working fluid, and input heating power. The results indicated that the evaporator and condenser thermal resistance decrease with increasing input heating power. The condenser thermal resistance clearly increased with increasing fill ratio. A groove-type evaporator surface with 0.2 mm height and 1 mm width had the best performance, decreasing the evaporator thermal resistance about 15.5% compared to a smooth surface. Correlations for evaporator and condenser thermal resistance were also developed, and their precisions, when compared with the experimental data, were about 9.6 and 11.6%, respectively. Because of the intermittent...
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Miniature Vapor Compressor Refrigeration System for Electronic Cooling
IEEE Transactions on Components and Packaging Technologies, 2010Co-Authors: Chih-chung Chang, Nai-wen Liang, Sih-li ChenAbstract:This paper experimentally investigated the thermal performance of a miniature vapor compressor refrigeration system using a thermal resistance model for Electronic Cooling. The evaporator, compressor, expansion valve, and condenser are the four main devices forming the refrigeration system with R-134a as a working fluid. The experimental parameters considered were the openings of the expansion valve and input heating power. The results indicated that the system in this paper had the largest Cooling capacity of 150 W and coefficient of performance of 4.25 at the 8th and 9th openings of the expansion valve, respectively. The results also showed that correlations of the thermal resistance of the evaporator and the condenser are developed with experimental data and their precision, compared with the experimental data, was about 4.42% and 12%, respectively. Besides the adjustment of the compressor speed could decrease the possibility of the occurrence of condensation phenomena near the inlet and outlet of the evaporator. Also, the smallest dimension of the combination of the evaporator and condenser is presented at the input heating power of 150 W and the 8th opening of the expansion valve.
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Two-phase closed thermosyphon vapor-chamber system for Electronic Cooling
International Communications in Heat and Mass Transfer, 2010Co-Authors: Te-en Tsai, Chih-chung Chang, Sih-li ChenAbstract:Abstract This article experimentally investigates a two-phase closed thermosyphon vapor-chamber system for Electronic Cooling. A thermal resistance net work is developed in order to study the effects of heating power, fill ratio of working fluid, and evaporator surface structure on the thermal performance of the system. The results indicate that either a growing heating power or a decreasing fill ratio decreases the total thermal resistance, and the surface structure also influences the evaporator function prominently. A reasonable agreement with Rohesnow's empirical correlation is found for the evaporator. An optimum overall performance exists at 140 W heating power and 20% fill ratio with sintered surface, and the corresponding total thermal resistance is 0.495 °C W − 1 .
D Jagannatha - One of the best experts on this subject based on the ideXlab platform.
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Thermal performance evaluation of a synthetic jet heat sink for Electronic Cooling
2011 IEEE 13th Electronics Packaging Technology Conference, 2011Co-Authors: Tilak T Chandratilleke, Radhika Narayanaswamy, D JagannathaAbstract:This paper presents a performance investigation on a highly effective heat removal technique for heat sinks in Electronic Cooling applications. This arrangement utilises a pulsating fluid jet mechanism known as synthetic jet, which is characterised by zero net fluid discharge through the jet orifice. The study uses an experimental rig comprising a high-frequency pulsating air jet that impinges on a heated surface to emulate the heat sink operation attached to an Electronic device. The Cooling characteristics of this jet are examined for a range of parametric conditions, including jet-impinging distance while evaluating the heat removal rates. The results indicate that the pulsating jet produces outstanding Cooling performance at the heated surface with significant dependency of it on the jet-impinging distance. The study also assesses the interaction of a cross-flow fluid stream on the pulsed jet operation. It is observed that the cross-flow somewhat impedes the pulsed jet thermal performance. However, the pulsed jet, with or without cross flow, delivers an overall Cooling ability that supersedes the standard flow-through heat sink performance. This technique provides highly enhanced surface Cooling potential without incurring increased fluid pressure drop or requiring additional fluid circuit, which are significant advantages for high-powered heat sink design.
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Analysis of a Synthetic Jet-Based Electronic Cooling Module
Numerical Heat Transfer Part A: Applications, 2009Co-Authors: D Jagannatha, Ramesh Narayanaswamy, Tilak T ChandratillekeAbstract:This article presents a numerical study of an Electronic Cooling module using a periodic jet flow at an orifice with net zero mass flux, known as a synthetic jet. The two-dimensional time-dependant numerical simulation models the unsteady synthetic jet behavior, the flow within the cavity and the diaphragm movement while accounting for fluid turbulence using the shear-stress-transport (SST) k-ω turbulence model. Computations are performed for a selected range of parameters and the boundary conditions to obtain the heat and fluid flow characteristics of the entire synthetic jet module. The numerical simulation aptly predicts the sequential formation of the synthetic jet and its intrinsic vortex shedding process while accurately illustrating the flow within the cavity. It is indicated that the thermal performance of the synthetic jet is highly dependant on the oscillating diaphragm amplitude and frequency. At the heated surface, this jet impingement mechanism produces a very intense localized periodic cooli...