778results about How to "Increase heat transfer rate" patented technology

A device for measuring fluid flow rates over a wide range of flow rates (<1 nL / min to >10 μL / min) and at pressures at least as great as 2,000 psi. The invention is particularly adapted for use in microfluidic systems. The device operates by producing compositional variations in the fluid, or pulses, that are subsequently detected downstream from the point of creation to derive a flow rate. Each pulse, comprising a small fluid volume, whose composition is different from the mean composition of the fluid, can be created by electrochemical means, such as by electrolysis of a solvent, electrolysis of a dissolved species, or electrodialysis of a dissolved ionic species. Measurements of the conductivity of the fluid can be used to detect the arrival time of the pulses, from which the fluid flow rate can be determined. A pair of spaced apart electrodes can be used to produce the electrochemical pulse. In those instances where it is desired to measure a wide range of fluid flow rates a three electrode configuration in which the electrodes are spaced at unequal distances has been found to be desirable.

A heat spreader includes a bottom wall (12) and a cover (14) hermetically connected to the bottom wall. Cooperatively the bottom wall and the cover define a space (11) therebetween for receiving a working fluid therein. A wick structure (15) is received in the space and thermally interconnects the bottom wall and the cover. The wick structure includes at least a carbon nanotube array, which can conduct heat from the bottom wall to the cover and draw condensed liquid of the working fluid from the cover toward the bottom wall.

A finned tube includes channels defined between adjacent fins on the tube body outer surface. Wings extend from side walls of the adjacent fins between the fin top and the fin base such that the wings form a barrier which splits the channel into an upper channel and a lower channel. A plurality of holes penetrate the barrier where the wings meet, so liquids and gases can pass into and out of the enclosed area defined by the lower channel. The wings can include alternating upper wings and lower wings, and there can be depressions formed in the fin top.

This invention provides heat engines based on various structures of internal combustion engines, such as a four-stroke piston-type combustion engine, two-stroke piston-type combustion engine, rotary combustion engine, or a free-piston type combustion engine. Said heat engine is provided with at least a heating chamber per piston or rotor, a heat exchanger unit disposed within said heating chamber through which thermal energy is extracted from a heat source and at least a port leading to a working chamber space from said heating chamber, and has a significantly increased heat transfer duration from the heat source to the working fluid within said heating chamber without increasing the number of strokes per power stroke in a cycle. Additionally, said heat engine is provided with an over expansion mechanism in conjunction with a compression means for intake charge. Thereby many of the operational characteristics of an Otto power cycle may be attained in said heat engine, and a heat source with a relatively low temperature may be accommodated through the combination of a lower compression ratio, the over expansion mechanism, and the boost of the intake charge.Another major objective of this invention is to provide a refrigerator based on the structures of the various heat engines disclosed in this invention and having a reversed operation of the heat engine. The invention combines the compression functionality of a compressor and the expansion functionality of a turbine in an air cycle machine into a single refrigerator unit having a simple mechanical structure, and provides a significantly increased heat removal rate or duration before the expansion stroke to reduce the temperature of the working fluid without increasing the number of strokes per discharge stroke of cooled working fluid in the cycle. Said refrigerator may include the over expansion mechanism or working fluid pressurization to increase the coefficient of performance and cooling load. In particular, said refrigerator uses a gas as the working fluid to avoid the negative impact of a conventional refrigerant on the environment.

A heat exchanger for a heating, ventilating and air conditioning system comprises a plurality of heat exchange tubes extending between a pair of spaced header tanks and arranged in groups of tubes with varying number of tubes in each group to cause a refrigerant to flow in multiple passes in the interior of the tubes across another fluid flowing on the exterior of the tubes. The heat exchange tubes comprise a plurality of flow passages having at least one corner formed by a pair of straight or arcuate sides with an included angle of less than or equal to ninety degrees, more preferably less than or equal to thirty degrees, to promote intense pool boiling within the flow passages. In addition to at least one corner region, the flow passage has a passage-specific optimal hydraulic diameter determined by the relationship between the optimal hydraulic diameter of the passage and the optimal hydraulic diameter of a baseline circular passage.