A nucleate boiling surface is formed on at least one side of a strip by roll forming. A first pattern of grooves separated by ridges in the form of a double helix is rolled into a strip. A second pattern of more shallow grooves is then machined into the ridges. The ridges are then deformed so that the fin ends extend over the first pattern of grooves forming subsurface channels. Concomitantly, the second pattern of grooves forms a plurality of pores intersecting the subsurface channels.

1. Field of the Invention
This invention relates to a method for forming an improved heat exchange surface. More particularly, a nucleate boiling surface is formed on at least one side of a deformable strip by roll forming. The strip can then be formed into a tube having an enhanced nucleate boiling surface.
2. Background of the Invention
In certain refrigeration applications such as a chiller or an evaporator, the liquid to be cooled is passed through a tube while liquid refrigerant is in contact with the outside of the tube. The refrigerant changes state from a liquid to a vapor absorbing heat from the fluid within the tube. The selection of the external configuration of the tube is extremely influential in determining the boiling characteristics and overall heat transfer rate of the tube. As disclosed in U.S. Pat. Nos. 4,050,507 to Chu et al, 4,474,231 to Staub et al. and 5,054,548 to Zoller, the transfer of heat to a boiling liquid is enhanced by the creation of nucleate boiling sites.
In nucleate boiling, liquid adjacent to a trapped vapor bubble is super heated by the heat exchanger surface. Heat is transferred to the bubble at the liquid vapor interface. The bubble grows in size until surface tension forces are overcome by buoyancy and the bubble breaks free from the surface. As the bubble leaves the surface, fresh liquid wets the now vacated area. The remaining vapor absorbs heat from the fresh liquid to form the next bubble. The vaporization of liquid and continuous stripping of the heated liquid adjacent to the heat transfer surface, together with the convection effect due to the agitation of the liquid pool by the bubbles result in an improved heat transfer rate for the heat exchanger surface.
U.S. Pat. No. 5,054,548, as well as U.S. Pat. Nos. 3,696,861 to Webb and 4,653,163 to Kuwahara et al. disclose manufacturing a nucleate boiling surface on the exterior side of a heat exchange pipe. External fin convolutions are formed on the outside surface of a tube using a fin forming disk. The tip portions of fins are bent toward adjacent fins, producing a substantially confined, elongated space which extends around the outside of the tubing forming a plurality of subsurface channels.
The fins are frequently notched prior to being bent over. When the fins are bent over, the fin tips contact the adjacent fin. The notched portion does not contact an adjacent fin and forms a pore intersecting the subsurface channels. During nucleate boiling, a stream of vapor exits through the pores and fresh liquid flows within the subsurface channels to occupy the space vacated by the streaming vapor. The notched fins may be formed by knurling helical notches on the surface of the tube prior to finning.
A method to form a nucleate boiling surface on the inside wall of a heat exchanger pipe is disclosed in U.S. Pat. No. 5,052,476 to Sukumoda et al. A deformable strip of metal is passed through a sequence of forming rolls. The first roll forms a plurality of U-shaped grooves. The undeformed metal separating the U-shaped grooves forms a plurality of fins. A second forming roll forms a V-shaped notch part way through each fin. Flaring the halves of the split fins towards one another brings adjacent split fins in close proximity. The base of the U-shaped groove forms a subsurface channel with the pore an exit means for vapor in accordance with nucleate boiling practice.
Roll forming has been used to enhance either the inside or outside surface of a strip prior to forming into a tube. For example, U.S. Pat. Nos. 3,861,462, 3,885,622 and 3,906,605 all to McLain and all incorporated by reference in their entireties herein, disclose the use of textured rolls to form a desired pattern on either one or both surfaces of a metallic strip. The strip is formed into a tubular shape by passing through a plurality of tube forming rolls. A welding station then joins longitudinally extending edges of the strip to form a complete tube.
Roll forming has been used to form a continuous groove pattern or diamond shaped pattern as disclosed in the McLain patents. A plurality of discrete roughness elements on the internal surface of a tube in the form of flattened pyramids is disclosed in U.S. Pat. No. 5,070,937 to Mougin et al.
Grooves, diamond shaped patterns and roughness elements increase the surface area of the tube and influence the flow of liquid. However, the patterns do not encourage nucleate boiling. Accordingly, it is an object of the present invention to provide a method for forming a nucleate boiling surface by roll forming. It is a feature of the invention that the nucleate boiling surface is formed by a combination of roll forming and machining operations. It is an advantage of the method of the invention that the nucleate surface is formed prior to conversion of the strip into tube and the nucleate surface may be located on either the inside or outside surface. Another advantage of the invention is that both the size of the subsurface channels and the pores are easily controlled. Yet another advantage is that in addition to forming a nucleate surface by roll forming, the opposing side of the strip may be enhanced. Yet another advantage of the invention is that the strip width is limited only by the capacity of the forming rolls. The strip may be slit to a desired width prior to tube forming.

Method of forming a nucleate boiling surface by a roll forming


In accordance with embodiments of the present disclosure, a method may include determining individual spectrum requirements for each of a plurality of signals to be communicated in an optical network, wherein a first signal of the plurality of signals has a first spectrum requirement and a second signal of the plurality of signals has a second spectrum requirement. The method may also include calculating a minimum spectrum granularity based on the individual spectrum requirements. The method may further include assigning each particular signal a channel spectrum equal to an integer multiple of the minimum spectrum granularity.

Telecommunications systems, cable television systems and data communication networks use optical networks to rapidly convey large amounts of information between remote points. In an optical network, information is conveyed in the form of optical signals through optical fibers. Optical fibers comprise thin strands of glass capable of communicating the signals over long distances with very low loss. An optical network may be configured to combine modulated signals at various wavelengths or optical frequencies (also known as "channels") into a single optical fiber. Each disparate channel may include optically encoded information to be communicated throughout the optical network. Such combining of various channels into a single fiber is known as wavelength-division multiplexing (WDM). Dense wavelength division multiplexing (DWDM) refers to multiplexing a larger (denser) number of wavelengths, usually greater than forty, into a fiber. WDM, DWDM, or other multi-wavelength transmission techniques are employed in optical networks to increase the aggregate bandwidth per optical fiber. Without WDM or DWDM, the bandwidth in networks would be limited to the bit rate of solely one wavelength. With more bandwidth, optical networks are capable of transmitting greater amounts of information.
Most of the presently-existing optical networks today are operated at 10 gigabit-per-second (Gbps) or 40 Gbps signal rates with 50 gigahertz (GHz) of channel spacing in accordance with International Telecommunications Union (ITU) standard wavelength grids, also known as fixed-grid spacing. However, as data rates increase to 100 Gbps and beyond, the wider spectrum requirements of such higher data rate signals often require increasing channel spacing. In traditional fixed grid networking systems supporting signals of different rates, the entire network system typically must be operated with the coarsest channel spacing (100 GHz, 200 GHz, etc.) that can accommodate the highest rate signals. This may lead to an over-provisioned channel spectrum for lower-rate signals and lower overall spectrum utilization.

Method and system for calculating spectrum granularity in flexible grid optical networks


A door module for a refrigerated case includes a central panel with a peripheral flange. A first panel is disposed on one side of the central panel and is supported by the flange. A second panel is disposed on another side of the central panel and is supported by the flange. A first seal is disposed between the first side of the flange and the first panel, and a second seal is disposed between the second side of the flange and the second panel. A channel with a desiccant material is disposed within the flange. A first opening extends from the channel to a first space between the first panel and the central panel, and a second opening extends from the channel to a second space between the second panel and the central panel. A frame is coupled to the flange and overlaps the first and second panels.

The present invention relates generally to the field of temperature controlled display devices (e.g. refrigerated cases, etc.) for storing and displaying refrigerated or frozen objects. More specifically, the present invention relates to a door for refrigerated cases. More specifically still, the present invention relates to a door module having a central transparent panel with a peripheral flange that supports first and second lateral panels disposed on opposite sides of the central panel. The central panel serves as the structural backbone of the door module, and the remaining components of the door module are supported by the central panel via its peripheral flange.
It is well known to provide a temperature controlled display device such as a refrigerator, freezer, refrigerated merchandiser, refrigerated display case, etc., that may be used in commercial, institutional, and residential applications for storing or displaying refrigerated or frozen objects. For example, it is known to provide self-service type refrigerated display cases or merchandisers having doors that are intended for operation by consumers to access refrigerated or frozen objects (e.g. food products and the like, etc.) within the temperature controlled interior space. However, such known doors for temperature controlled display devices have a number of disadvantages. For example, the transparent panels used to provide a see-through thermal barrier are typically assembled into 'glass-packs' having complicated edge treatments for holding, sealing, and structurally supporting the glass panels together as an assembled unit. Such typical glass packs tend to be relatively fragile, and difficult and costly to assemble, and often rely on an external frame to provide structural stability for the transparent panel portion of the door.
Accordingly, it would be desirable to provide a door module for a temperature controlled display device that overcomes these and/or other disadvantages.


The present application provides a low carbon martensitic high temperature strength steel and a preparation method thereof, wherein the chemical composition of the low carbon martensitic high temperature strength steel are: C: 0.10-0.25 wt %, Cr: 10.0-13.0 wt %, Ni: 2.0-3.2 wt %, Mo: 1.50-2.50 wt %, Si≤0.60 wt %, Mn≤0.60 wt %, W: 0.4-0.8 wt %, V: 0.1-0.5 wt %, Co: 0.3-0.6 wt %, Al: 0.3-1.0 wt %, Nb: 0.01-0.2 wt %, and a balance of Fe. The high temperature strength steel of the present application achieves high strength at high temperature by simultaneously precipitating both nano-coherent carbides and intermetallic compounds. It has an excellent toughness, and can be used for certain structural parts under special working conditions, such as aero-engines to increase its service life and service temperature.

The aero-engine is one of the precise mechanical structures in the aircraft. Because the aero-engine is usually operated under complex conditions at work, it requires very high reliability to meet the safety of flight. Among them, the aero-engine pylon is a structural part of aero-engine used to bear the weight of aero-engines, which is often exposed to harsh working environments such as high temperature, humidity, high stress and corrosive media. Therefore, there are higher requirements for the performance at high temperature, toughness and corrosion resistance and the like of the structural parts used in special working conditions, such as aero-engine pylon.
The commonly used steel for aero-engine structural parts in the prior art is mainly martensitic steel with a Cr content of 12%, which has the advantages of high strength, good heat resistance, high temperature oxidation resistance and the like. High temperature strength steel is a kind of steel with a good oxidation resistance and a relative high strength at high temperature, wherein 1Cr12Ni2WMoVNb (hereinafter referred to as GX-8 high temperature strength steel) and 1Cr11Ni2W2MoV (hereinafter referred to as 961 high temperature strength steel) are the martensitic high temperature strength steel having good performances, which can be used to manufacture aero-engine pylon and other load-bearing components working in humid environments below 600° C. Although GX-8 high temperature strength steel has a high strength and high toughness, its working temperature is limited to a maximum of 600° C. With the continuous increase of the thrust of modern advanced aero-engines, the service temperature of load-bearing components such as aero-engine pylon can reach above 600° C. At that time, the strength at high temperature of GX-8 and 961 high temperature strength steel are seriously insufficient with the tensile strength at 700° C. being only about 200 MPa, which is difficult to meet the strength and safety requirements of load-bearing components.
Therefore, there is an urgent need for martensitic steel with higher strength at high temperature and higher service temperature, as well as a good plastic toughness at room temperature, which can be used in the structural parts of aero-engines.

Low carbon martensitic high temperature strength steel and preparation method thereof

University of Science and Technology Beijing