Thermal management device

Details Thermal management device Thermal management device

2001-06-04

2003-07-29

Wayner, William (Department: 3744)

Refrigeration

Processes

Compressing, condensing and evaporating

C417S413100

Reexamination Certificate

active

06598409

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally concerns a vapor compression refrigeration cycle thermal management devices and more particularly a modularized, high energy transfer rate, and gravity insensitive heat transfer device.
BACKGROUND OF THE INVENTION
More efficient and scalable thermal management systems are required in many applications ranging from electronics cooling to medical practice where localized cooling is needed as differentiated from macrocooling of a large environment.
For example, the drive for increased performance has led to smaller, faster transistors and consequently, integrated circuits with larger transistor density, higher Input/Output count, and faster clock frequency. The larger transistor density at nearly constant supply voltage and ever increasing clock frequencies has resulted in increased dynamic power dissipation. This increasing power must be dissipated by the thermal management scheme employed in the package. These trends are evidenced by the exponential increase of power density over time for state-of-the-art integrated circuits. In the latest projections of the Semiconductor Industry Association (1999), the total power dissipation is expected to push the present state-of-knowledge for thermal management. The challenge for the identification of a future thermal management technology arises from the requirement of the package to provide a robust mechanical support, a low-distortion electrical conduit for the incoming and outgoing signals, environmental protection, and thermal dissipation at low cost and high reliability.
Currently, several approaches to thermal management are used in production chip packages. For example, buoyancy-driven convective heat transfer from the heat sink to the ambient is employed for portable integrated circuit (IC) applications, while forced convection is used for high-performance IC applications. In the past, mainframe computers and supercomputers have employed complex and expensive closed-loop cooling systems using liquids. Most microprocessor and microelectronic systems have avoided closed-loop thermal management approaches due to their high cost, high power, high acoustic noise, and low reliability. These macro-scale techniques employing bulky refrigeration units are not compatible with many future microelectronic applications in high performance markets.
Efficient two-phase boiling and condensing systems capable of transferring more energy across a smaller temperature gradient can significantly help meet performance requirements for high power density and minaturized physical dimensions. Even though dropwise condensation offers heat transfer coefficients at least an order of magnitude higher than filmwise condensation, conventionally, filmwise condensation has been used in industrial condensers but not in miniaturized applications.
With the rapid advances in the area of micro-electro-mechanical systems (MEMS) in recent years, miniaturized devices are achieving higher energy effectiveness. Membranes are of particular interests in MEMS for their use as valves, pumps, and compressors in micro-fluidic devices. Membranes can use electrostatic, piezo-electric or thermal actuation to pressurize a fluid in a cavity. More recently, design concepts of miniaturized cooling systems have been proposed based on the refrigeration vapor-compression cycle (Shannon et al., 1999, and Ashraf et al., 1999). In particular, Shannon et al. (1999) have used an electrostatic diaphragm with valves to perform compression, whereas Ashraf et al. (1999) have used a centrifugal compressor. However both used conventional heat exchanger condenser and evaporator. The herein cyclic thermal management system is also based on the refrigeration vapor compression cycle, however possesses original components. In the herein system an actuated-membrane is adopted as the condensing surface as well as the ejecting device. Therefore the droplets ejected serve the dual purpose for maintaining dropwise condensation and creating a spray for highly efficient cooling.
Thus, there is a strong need for a compact, highly energy efficient device. Such a device could be connected with other similar devices to form arrays and could be incorporated in many useful devices.
SUMMARY OF THE INVENTION
These and other needs are met or exceeded by the present vapor compression cycle heat transfer device with a dropwise condenser. High efficiency cooling available in conventional large mechanical compressor vapor compression heat transfer devices is produced by the present invention in a substantially different physical embodiment similar to integrated circuit packagings, and which may be constructed using traditional and microfabrication techniques. Heating is also available from the device of the invention, since a portion of the device will expel heat into an adjacent atmosphere, fluid or object while another portion of the device will absorb heat from an adjacent atmosphere, fluid or object. Individual, self-contained devices of the invention draw little electrical power and may be interconnected with like devices to satisfy localized cooling or heating over a desired area of atmosphere, fluid or object.
A device of the invention includes a housing having integrated compressor, condenser, expansion, and evaporator structures, with the evaporator structure removing heat from an adjacent atmosphere, fluid or object and the condenser structure expelling heat into an adjacent atmosphere, fluid or object. The compressor structure includes a compressor body defining a compressor cavity and a flexible compressor diaphragm mounted in the compressor cavity that compresses refrigerant within the cavity and promotes circulation of the refrigerant through a closed path defined through the compressor, condenser, expansion, and evaporator structures.
The condenser structure is in fluid communication with the compressor structure and includes a flexible condenser diaphragm that promotes growth of a plurality of droplets to form upon a cooled condenser surface and propels the droplets from the condenser surface of the condenser diaphragm into the expansion structure. The expansion structure includes an expansion chamber in fluid communication with the condenser structure and which is in expansive receipt of the droplets propelled from the condenser diaphragm. Finally, the evaporator structure includes an evaporator chamber which is proximate a top end of the expansion chamber and which is in fluid communication with the expansion chamber and the compressor structure.
The device is modularized, energy efficient and gravity insensitive. It provides high cooling rates for electronic instruments, and offers a novel means for thermal management. It can also be scaled to accommodate different types of applications.


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Article entitled “A Micro-Scale Membrane-Actuated Condenser/Evaporator For Enhanced Thermal Management” by Marianne M. Francois, Wei Shyy and Jacob N. Chung, Printed in the American Society of Mechanical Engineers, Proceedings of the ASME Heat Transfer Division—2000, International Mechanical Congress and Exposition, Nov. 5-10, 2000, Orlando, Florida, HDT-vol. 366-2, pp. 1-7.

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