HDD Regenerator 2011 DC 12.11.2013-TeamGBZ 64 Bit
Anna Pybus
Some of us on the JavaScript Infrastructure team at Facebook got restless waiting for the future to get here, so we developed a tool called regenerator to replace generator functions with efficient JavaScript-of-today (ECMAScript 5 or ES5 for short) that behaves the same way. Since the tool itself is implemented in ES5, you can try it right now, in this web browser, without leaving this web page.
Regenerator relies heavily on the Esprima JavaScript parser and two libraries that we maintain for manipulating abstract syntax trees, ast-types and recast. It is similar in spirit to Google's Traceur Compiler, which supports generators and many other ES6 features through source transformation, but we would argue it compares favorably to Traceur in several ways.
- Traceur supports yield expressions only on the right-hand sides of assignment statements and variable declarations, or as standalone statements, whereas regenerator allows a yield expression to appear anywhere an expression is permitted to appear.
- Regenerator aims to generate as little boilerplate as possible, whereas Traceur generates twice as much code for the simplest of generators.
- Regenerator transforms generator functions and nothing else, so you don't have to buy into the entire Traceur runtime just to get support for generators.
A regenerative heat exchanger, or more commonly a regenerator, is a type of heat exchanger where heat from the hot fluid is intermittently stored in a thermal storage medium before it is transferred to the cold fluid. To accomplish this the hot fluid is brought into contact with the heat storage medium, then the fluid is displaced with the cold fluid, which absorbs the heat.[1]
The first regenerator was invented by Rev. Robert Stirling in 1816, and is also found as a component of some examples of his Stirling engine. The simplest Stirling engines, including most models, use the walls of the cylinder and displacer as a rudimentary regenerator, which is simpler and cheaper to construct but far less efficient.
In rotary regenerators, or thermal wheels, the heat storage "matrix" in the form of a wheel or drum, that rotates continuously through two counter-flowing streams of fluid. In this way, the two streams are mostly separated. Only one stream flows through each section of the matrix at a time; however, over the course of a rotation, both streams eventually flow through all sections of the matrix in succession. The heat storage medium can be a relatively fine-grained set of metal plates or wire mesh, made of some resistant alloy or coated to resist chemical attack by the process fluids, or made of ceramics in high temperature applications. A large amount of heat transfer area can be provided in each unit volume of the rotary regenerator, compared to a shell-and-tube heat exchanger - up to 1000 square feet of surface can be contained in each cubic foot of regenerator matrix, compared to about 30 square feet in each cubic foot of a shell-and-tube exchanger.[4]
Each portion of the matrix will be nearly isothermal, since the rotation is perpendicular to both the temperature gradient and flow direction, and not through them. The two fluid streams flow counter-current. The fluid temperatures vary across the flow area; however the local stream temperatures are not a function of time. The seals between the two streams are not perfect, so some cross contamination will occur. The allowable pressure level of a rotary regenerator is relatively low, compared to heat exchangers.
In a fixed matrix regenerator, a single fluid stream has cyclical, reversible flow; it is said to flow "counter-current". This regenerator may be part of a valveless system, such as a Stirling engine. In another configuration, the fluid is ducted through valves to different matrices in alternate operating periods resulting in outlet temperatures that vary with time. For example, a blast furnace may have several "stoves" or "checkers" full of refractory fire brick. The hot gas from the furnace is ducted through the brickwork for some interval, say one hour, until the brick reaches a high temperature. Valves then operate and switch the cold intake air through the brick, recovering the heat for use in the furnace. Practical installations will have multiple stoves and arrangements of valves to gradually transfer flow between a "hot" stove and an adjacent "cold" stove, so that the variations in the outlet air temperature are reduced.[5]
Another type of regenerator is called a micro scale regenerative heat exchanger. It has a multilayer grating structure in which each layer is offset from the adjacent layer by half a cell which has an opening along both axes perpendicular to the flow axis. Each layer is a composite structure of two sublayers, one of a high thermal conductivity material and another of a low thermal conductivity material. When a hot fluid flows through the cell, heat from the fluid is transferred to the cell wells, and stored there. When the fluid flow reverses direction, heat is transferred from the cell walls back to the fluid.
A third type of regenerator is called a "Rothemühle" regenerator. This type has a fixed matrix in a disk shape, and streams of fluid are ducted through rotating hoods. The Rothemühle regenerator is used as an air preheater in power generating plants. The thermal design of this regenerator is the same as of other types of regenerators.[citation needed]
Regenerative heat exchangers are made up of materials with high volumetric heat capacity and low thermal conductivity in the longitudinal (flow) direction. At cryogenic (very low) temperatures around 20 K, the specific heat of metals is low, and so a regenerator must be larger for a given heat load.[citation needed]
The advantages of a regenerator over a recuperating (counter-flowing) heat exchanger is that it has a much higher surface area for a given volume, which provides a reduced exchanger volume for a given energy density, effectiveness and pressure drop. This makes a regenerator more economical in terms of materials and manufacturing, compared to an equivalent recuperator.[citation needed]
The design of inlet and outlet headers used to distribute hot and cold fluids in the matrix is much simpler in counter flow regenerators than recuperators. The reason behind this is that both streams flow in different sections for a rotary regenerator and one fluid enters and leaves one matrix at a time in a fixed-matrix regenerator. Furthermore, flow sectors for hot and cold fluids in rotary regenerators can be designed to optimize pressure drop in the fluids. The matrix surfaces of regenerators also have self-cleaning characteristics, reducing fluid-side fouling and corrosion. Finally properties such as small surface density and counter-flow arrangement of regenerators make it ideal for gas-gas heat exchange applications requiring effectiveness exceeding 85%. The heat transfer coefficient is much lower for gases than for liquids, thus the enormous surface area in a regenerator greatly increases heat transfer.[citation needed]
The major disadvantage of rotary and fixed-matrix regenerators is that there is always some mixing of the fluid streams, and they can not be completely separated. There is an unavoidable carryover of a small fraction of one fluid stream into the other. In the rotary regenerator, the carryover fluid is trapped inside the radial seal and in the matrix, and in a fixed-matrix regenerator, the carryover fluid is the fluid that remains in the void volume of the matrix. This small fraction will mix with the other stream in the following half-cycle. Therefore, rotary and fixed-matrix regenerators are only used when it is acceptable for the two fluid streams to be mixed. Mixed flow is common for gas-to-gas heat and/or energy transfer applications, and less common in liquid or phase-changing fluids since fluid contamination is often prohibited with liquid flows.[citation needed]
The dermal regenerator was a common, easily operable medical tool used by several civilizations to heal minor skin wounds, such as cuts and burns. The dermal regenerator could also be used to revert surgically modified skin to its normal state, as well as to remove scars. It could also be used to simulate wounds or burns.
In the book Star Trek: Aliens & Artifacts, Alan Sims describes how you can make your own Dermal Regenerator. The regenerator that it refers to is actually made from an electric hair brush, and was seen in VOY: "Workforce". (Seen above, version 2377)
A prop dermal regenerator was sold in week 1 of the It's A Wrap! sale and auction for US$1,275.00. According to the listing, it was seen in the Voyager episode "State of Flux". The item is the 2376 version from the picture above. [1]
We study the performance of a multichannel version [M. Vasilyev and T.I. Lakoba, Opt. Lett. 30, 1458 (2005)] of the all-optical Mamyshev regenerator in a practically important situation where one of its key components - a periodic-group-delay device - has a realistic amplitude characteristic of a bandpass filter. We show that in this case, the regenerator can no longer operate in the regime reported in our original paper. Instead, we have found a new regime in which the regenerator's performance is robust not only to such filtering, but also to considerable variations of regenerator parameters. In this regime, the average dispersion of the regenerator must be (relatively) large and anomalous, in constrast to what was considered in all earlier studies of such (single-channel) regenerators based on spectral broadening followed by off-center filtering. In addition, hardware implementation of a regenerator in the new regime is somewhat simpler than that in the original regime.
A solar liquid desiccant air cooling system cools air in two stages: dehumidification followed by sensible cooling. It uses concentrated liquid desiccant to dehumidify the process air and reject the absorbed moisture to the ambient air through solar thermal heating in a solar collector cum regenerator (C/R). For the dehumidifier the liquid desiccant must be cold and strong in desiccant to reduce tendency of evaporation of water in the solution so that it can absorb water vapor from the process air. But, in the solar regenerator the solution must be hot to enhance evaporation of water from the solution to the regeneration air which requires thermal energy. The solar collector cum regenerator performance decides the overall cooling performance because for every kilogram of water dehumidified, at least the same amount must be rejected in the solar regenerator. Direct coupling of the solar regenerator with the dehumidifier may not be possible since the moisture removed in the dehumidifier may not get evaporated in the solar regenerator simultaneously. The solar thermal energy collection and the operating conditions decide the regeneration capacity of the solar collector cum regenerator. This paper presents experimental solar regeneration performance of CaCl2-H2O and LiCl-H2O solutions using two different sized solar C/R of absorber area 1.47 and 4 m2 inclined at 14o from the horizontal. The diurnal mass of water evaporated from LiCl and CaCl2 solutions at different concentrations is reported. The water evaporation per unit absorber area was found to be independent of C/R size for experiments carried out on the two regenerators for both LiCl and CaCl2 solutions for similar levels of irradiance and initial desiccant concentration. In addition, the paper discusses some basic solar C/R design issues and explores the coupling possibility of a solar C/R with a liquid desiccant cooling system. The results presented are useful in deciding the size of a solar C/R for coupling with a liquid desiccant cooling system of desired capacity.
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