A new energy-efficient approach to high vacuum pumping

Recent experiments have shown that an efficienty trapped mechanical rotary pump operating with completely degassed oil is capable of pressures in the 10^?7 mbar range. By greatly enlarging the zeolite trap and mounting it immediately adjacent to the work chamber it can be made to funtion simultaneously as a high speed sorption pump for vapours. Outgassed vapours from the work chamber and vapours originating from the pump oil are both pumped by the zeolite. The zeolite is operated at room temperature except during bakeout and is maintained at very low surface coverages to obtain corresponding low equilibrium pressures of water and hydrocarbons. Gases which are not sorbed by the zeolite are pumped by the mechanical pump. Vapour pumping continues for periods of months even when all power to the system is shut down. High vacuum is attainable within a few minutes after reapplying power. If desired, the zeolite can be cooled to raise the pumping speeds for all gases to approximately those for vapours, and to reduce ultimate pressures to the 10^?8 mbar range. This principle can be used as the basis for practical pumping systems which provide clean high vacua with low power consumption. Two pumping stations with speeds for vapours in the 12/s^?1 and 400ls^?1 range, respectively, are discussed.     

Selbsttrocknende Membran‐ Vakuumpumpen für feuchte Gase

Diaphragm vacuum pumps have proved their superiority as dry‐running systems over other types of vacuum pumps in many applications, and in particular in the medical, analysis, and process engineering sectors, as well as in the chemical industry. These pumps deliver the media without any contamination of content, have a high gas tightness, and can be designed as chemically resistant with regard to those parts which come in contact with the media. Although they are in principle relatively insensitive towards condensates which may be formed or conveyed with the media, liquids in the vapor or gas flow may be the cause for the prolongation of a vacuum process, which can be considerable and is certainly undesirable. This applies in particular to applications involving multi‐user vacuum systems in chemical laboratories, which under certain circumstances may contain very substantial volumes of condensates, and to the use of pumps in steam sterilizers (autoclaves) and vacuum drying cabinets. These examples of applications will be considered in greater detail hereinafter. The condensates which occur in the pump head of a diaphragm vacuum pump cause interference in that — due to re‐evaporation during the suction cycle — they incur a substantial reduction in the usable suction capacity of the pump. This problem can be resolved by means of a drying system for diaphragm vac uum pump heads. The drying system makes use in this case of the pressure differential which pertains between the pump chamber and the atmosphere outside the pump. The function of the drying system can be described as follows: A solenoid valve vents the pump head in a cyclic manner, with the result that liquid in the pump head will be blown out, while the process vacuum in the process engineering system will continue to be maintained. Diaphragm vacuum pumps equipped with this drying system have provided excellent results, for example in the chem ical laboratory, both in individual diaphragm vacuum pumps as well as in multi‐user vacuum systems. Extremely good experience has also been gained in the evacuation of sterilizer autoclaves and vacuum drying cabinets with the use of diaphragm vacuum pumps fitted with the drying system. When using the drying system on steam sterilizer autoclaves, another favorable effect is also encountered: The vapor fraction in the pumping medium is cooled in the diaphragm pump head to below the evaporation or boiling temperature, with the result that the vapour condenses. This reduces its volume to a fraction of the initial value, which is the equivalent of an additional suction capacity, in the same manner as with a condenser. The condensate which occurs with this process is blown out of the pump heads by the drying system, and, as a result, can no longer cause interference due to re‐evaporation.     

Local thermal effect at luminescent spot on upconversion luminescence in Y2O3:Er,Yb nanoparticles

Y₂O₃:Er³⁺,Yb³⁺ nanoparticles were synthesized using Pechini type sol-gel method and then characterized by XRD, TEM, SEM, Raman spectroscopy, and fluorescence spectrophotometer. Local temperature effect on upconversion luminescence intensities was theoretically analyzed and experimentally tested. These results indicate that a competition process between local temperature at luminescent spot and laser pump power density decides the development trend of upconversion luminescence intensity. Therefore, it can be concluded that the most intensive upconversion luminescence in Y₂O₃:Er³⁺,Yb³⁺ nanoparticles can be achieved at a certain pump power density, which should be slightly below a given constant value (the corresponding threshold of temperature).     

光学玻璃精密模压成形设备密封设计

目的研究高温情况下光学玻璃精密成形设备加热系统的密封性能。方法通过数值模拟分析,得到加热系统的温度场分布以及密封圈的温度变化规律,利用热电偶及红外测温仪对加热系统加热性能及安全性进行检测,在此基础上,对加热系统进行改进。结果随着加热时间和功率的增加,密封圈的温度随之上升。模压温度过高,橡胶圈存在破坏的可能。结论通过对密封处进行改良,橡胶圈在安全工作范围内,加热效率得到了改善。在机械泵和分子泵的共同作用下,模压腔内的真空度达到1 Pa以下。     

多层PET/PE复合膜的大尺度间歇热封工艺能耗研究

目的 分析热封设备连续加热热封工艺的能耗模型,优化设计适合大尺度热封设备的间歇加热热封工艺。方法 首先通过电热特性试验了解镍铬合金的升降温规律,拟合得到镍铬合金的升降温模型。其次分析连续加热热封工艺能耗模型,提出适用于大尺度热封设备的间歇加热热封工艺流程,并建立能耗模型。结果 以多层聚对苯二甲酸乙二醇酯/聚乙烯（PET/PE）复合膜为热封对象,以最小能耗为优化目标,计算得到最优的热封工艺流程。结论 大尺度热封设备采用间歇加热热封工艺加工可以有效减少能量损耗。     

Untersuchung des Wärmeausdehnungsverhaltens elektronenstrahlgeschweißter sowie hochtemperaturgelöteter NiCr20TiAl-Verbindungen

Investigations of the thermal expansion behaviour of electron beam welded and high temperature brazed NICr20TiAl-joints Thermal elongation of NiCr20TiAl-joints is greatly determined by thermal influence during the joining process or after heat treatment. The coefficients of thermal expansion (10^?6 · K^?1) between 20 and 900°C are for NiCr20TiAl solution treated, α = 16,74, electron beam welded, α = 17,33 and high temperature brazed joints with B-Ni5, α = 15,63. During the cooling period, α differs which can be assumed due to the γ′-precipitation hardening.     

Etude des facteurs d'intensification de l'échange de chaleur dans le refroidissement des fruits et légumes

Increasing the rate of fruit and vegetable cooling is of economic significance for the following reasons: biochemical and microbiological processes are quickly suppressed; surface mass-exchange with ambient air is slowed down; power consumption is reduced, and the freezing output of cooling equipment and installations is increased.It was assumed that the fruits and vegetables in crates were arranged regularly and covered with thin paper of a negligible small thermal resistance in order to eliminate the infiltration of cold air within the layers. Crates were arranged on a pallet so that they touched horizontally. Thus, the packages form plates above and below the cooling air flow. Heat-exchange with a one-dimensional temperature field is established.It was found that intensification of cooling can be achieved by increasing the speed of cooling air as well as by stopping the process at a higher final temperature. Increasing the speed up to 5 m s⁻¹ shortens the time of the process by a factor of two compared with the low speeds (0.3–0.5 m s⁻¹) which are normally used. The product can be cooled until the temperature in the layer centre reaches 5°C, and the surface temperature about 2°C, which is low enough. Afterwards the cooled product is transferred to a freezing chamber or to a van-freezer. This factor results in a further halving of the cooling time. The combined effect of the two factors shortens the duration of the process by about 75% and increases the output of the cooling equipment from 3.5 to 4 times.     

Effect of nano-sized TiO<Subscript>2</Subscript> powder addition on characteristics of silver–palladium electrodes

This study presents the sintering behavior of silver/palladium electrode powders to which have been added TiO₂ nanoparticles, and the effect this additive has on the ability of the electrode to match the characteristics of piezoelectric ceramics, Pb(Zr, Ti)O₃. The densification (shrinkage) of the electrodes was investigated as a function of sintering temperature, and the reaction between the ceramic matrix and the electrodes was studied. The densification of the TiO₂-enhanced electrode paste during the sintering process was explained with reference to a solid-state diffusion mechanism which integrated the TiO₂ into the ceramic. Reactions occurred between the ceramic and electrode layers, resulting in reduced internal stress and enhanced mechanical adhesion. Based on these results, it is clear that high adhesive strength and good electrical conductivity of more than 10⁴/Ω cm can be obtained in multilayer ferroelectric devices composed of stacks of ceramic and electrode layers provided the contain these nanoparticles. In the sintering process, interfacial diffusion of TiO₂ occurred and, as a consequence, coarse grains of PZT were formed at the interface.     

Phase‐Engineered Type‐II Multimetal–Selenide Heterostructures toward Low‐Power Consumption,Flexible, Transparent,and Wide‐Spectrum Photoresponse Photodetectors

Phase‐engineered type‐II metal–selenide heterostructures are demonstrated by directly selenizing indium‐tin oxide to form multimetal selenides in a single step. The utilization of a plasma system to assist the selenization facilitates a low‐temperature process, which results in large‐area films with high uniformity. Compared to single‐metal–selenide‐based photodetectors, the multimetal–selenide photodetectors exhibit obviously improved performance, which can be attributed to the Schottky contact at the interface for tuning the carrier transport, as well as the type‐II heterostructure that is beneficial for the separation of the electron–hole pairs. The multimetal–selenide photodetectors exhibit a response to light over a broad spectrum from UV to visible light with a high responsivity of 0.8 A W^?1 and an on/off current ratio of up to 10². Interestingly, all‐transparent photodetectors are successfully produced in this work. Moreover, the possibility of fabricating devices on flexible substrates is also demonstrated with sustainable performance, high strain tolerance, and high durability during bending tests.     

Kompakt-Vakuum-Meßgeräte mit PC-Anschluß – Windows-Software zur Prozeß-Auswertung

Personal computers, which are almost omnipresent nowadays, offer an economic way for storage, analysis and documentation of measurement data. In the following paragraph a new concept of vacuum gauges together with a corresponding Windows®®-software is presented, that enables the user to analyze various pressure measurements, such as pump diagrams and other process curves. The first group of instruments contains digital vacuum transmitters with an integrated display unit (VTA). They cover pressure ranges from 1600 mbar down to 10^?5 mbar. The second group consists of digital vacuum transmitters with logging capability (VTS). These pressure loggers have appropriately sealed housings and are suitable for being directly inserted into the evacuation volume, e. g. into vacuum packs. After the evacuation process has finished, the pressure data, that have been stored internally by the gauge, can be easily read out and analyzed via PC.     

Transfert de chaleur et de masse au cours du refroidissement des denrées périssables à bord des navires-durée minimale de refroidissement des cargaisons de fruits et légumes (dans les cales ou à l'intérieur des conteneurs)

Perishable goods (mainly fruit) are usually loaded aboard ships without precooling¹. The first phase of transport is therefore to cool the cargo down to the contractual carrying temperature as rapidly as possible. A priori, this implies that the ship's equipment can do this and in particular that the air distributing arrangement has been fitted for this purpose. The paper mainly deals with homogeneous cargoes having an even air permeability.In this Paper, the author adopts the conditions (extremely favourable) where the goods are directly exposed to the cooling fluid (with or without any protection against their drying out). These are conditions resulting in the minimum cooling time. The same calculation is applicable to any homogeneous cargo provided that the air distribution is properly balanced including that inside the packages (cases, boxes, etc). It may be locally applicable as well with the same conditions taking into account an unbalanced cooling air distribution system.The problems of cooling goods in large packages which the cooling air moves around is not dealt with: it leads moreover to prohibitive cooling durations and this case is to be avoided. This case is roughly approximated by a similar problem: the cooling of bodies with comparable sizes and shapes (plates, cylinders, spheres) with equivalent apparent conductivity which are suddenly put in a cold air flow maintained at an even and steady temperature. With such optimistic assumptions (where the heating is assumed to be negligible), the core and surface temperatures can be determined from the set of curves by Jacob⁹.The minimum cooling duration contemplated is the time needed to achieve a temperature in the whole cargo not too far from the carrying temperature. That temperature may exceed the latter by 2 or 3°C. In order to obtain it, all the basic cargo features are taken into account: breathing and, if necessary, desiccation as well as the rate of air circulation in horizontal and vertical ventilation.The functioning capabilities of the ship's equipment are also considered, on the one hand when starting and during the cooling down, if the available refrigerating capacity does not allow a step function as an initial condition, and, on the other hand, when the cooling air distributing system brings about a well known unbalance in the overall air flow distribution.     

Etude des facteurs d'intensification de l'échange de chaleur dans le refroidissement des fruits et légumesInvestigating the factors for intensifying fruit and vegetable cooling

Increasing the rate of fruit and vegetable cooling is of economic significance for the following reasons: biochemical and microbiological processes are quickly suppressed; surface mass-exchange with ambient air is slowed down; power consumption is reduced, and the freezing output of cooling equipment and installations is increased.It was assumed that the fruits and vegetables in crates were arranged regularly and covered with thin paper of a negligible small thermal resistance in order to eliminate the infiltration of cold air within the layers. Crates were arranged on a pallet so that they touched horizontally. Thus, the packages form plates above and below the cooling air flow. Heat-exchange with a one-dimensional temperature field is established.It was found that intensification of cooling can be achieved by increasing the speed of cooling air as well as by stopping the process at a higher final temperature. Increasing the speed up to 5 m s^?1 shortens the time of the process by a factor of two compared with the low speeds (0.3–0.5 m s^?1) which are normally used. The product can be cooled until the temperature in the layer centre reaches 5°C, and the surface temperature about 2°C, which is low enough. Afterwards the cooled product is transferred to a freezing chamber or to a van-freezer. This factor results in a further halving of the cooling time. The combined effect of the two factors shortens the duration of the process by about 75% and increases the output of the cooling equipment from 3.5 to 4 times.     

Characterization for water vapour barrier and heat sealability properties of heat‐treated paperboard/polylactide structure

The moisture barrier and heat sealability properties of polylactide (PLA) extrusion‐coated paperboard were investigated. The first part of the study focused on the influences of coating weight and surroundings temperature and relative humidity on the water vapour transmission rate (WVTR) of the structure. The outcome arising from this part was a simple and practical equation that allows calculating the WVTR as a function of PLA coating weight under specific thermo‐hygrometric conditions. The second part of the study investigated the effect of heat treatments between 100 and 150°C on the WVTR and heat sealability of a 20 g/m² PLA‐coated paperboard. According to the results, the lowest WVTR values achieved were about 2.5 times lower than the WVTR of the untreated structure. Presumably, the PLA coating experienced two types of reordering mechanisms: crystalline growth and packing of the amorphous structure. The greatest barrier improvement was achieved when both of these mechanisms were accumulated effectively. This was observed from the samples after a 40 min treatment at 130°C. Ultimately, the crystalline growth was experienced by PLA at 100–130°C temperatures. The packing of the amorphous section, which was also accumulated at higher temperatures, was suggested to be the decisive factor influencing WVTR. According to the heat sealing results, the heat treatments causing crystalline growth resulted in considerably increased sealing temperatures and reduced applicability of the material in high‐speed packaging applications. The treatments at 140–150°C caused only a slight increase in the sealing temperature and maintained the sealing performance of PLA. Copyright © 2009 John Wiley & Sons, Ltd.     

Manufacturing and Microstructural Evolution of Mechanuically Alloyed Oxide Dispersion Strengthened Superalloys

Mechanical alloying is a process in which mixtures of powders are severely deformed until they form atomic solutions. Inert oxides can also be introduced to form a dispersion of fine particles which help strengthen the consolidated product. Significant quantities of iron and nickel‐base alloys, with unusual properties, are produced commercially using this process. The total true strain during mechanical alloying can be as large as 9; there is proof that this leads to mixing on an atomic scale and to the development of a uniform grain structure which is sub‐micrometer in size. Following mechanical alloying, the particles are consolidated using standard powder metallurgical techniques. The consolidated metal has a large stored energy, approaching 1 J g^–1. This ought to make it easy to induce recrystallisation, but in practice the alloys fail to recrystallise except at very high temperatures close to melting. On the other hand, the recrystallisation temperature can be reduced dramatically by slightly deforming the consolidated product prior to heat treatment. It is in this context that the solution formation, microstructure and mechanical properties of such alloys are reviewed here.     

Numerical simulation of the temperature dependence of photoluminescence in strained-Si1−xGex/Si heterostructures

In previous work it has been shown that the decay in photoluminescence from Si/strained-Si_1–xGe_x/Si quantum wells at temperatures over 100 K is controlled by surface recombination and that the photoluminescence intensity can be increased by over an order of magnitude by surface passivation. These results had been explained only by a simple phenomenological model, which could not explain why at high pump power density the observed luminescence was constant from 77 to 250 K. This paper uses a two-carrier heterojunction device simulator to determine the carrier profiles during optical pumping. The profiles are used to understand quantitatively luminescence as a function of temperature and pump power density without making the over-simplifying assumptions required for analytical modeling. Surface recombination velocities over 10³ cm/s drastically affect the results, and Auger recombination plays an important role at high pump power density.     

Active Metamaterials with Negative Static Electric Susceptibility

Although well-established textbook arguments suggest that static electric susceptibility χ⁽⁰⁾ must be positive in “all bodies,” it has been pointed out that materials that are not in thermodynamic equilibrium are not necessarily subject to this restriction. Media with inverted populations of atomic and molecular energy levels have been predicted theoretically to exhibit a χ⁽⁰⁾ < 0 state, however the systems envisioned require reduced temperature, reduced pressure, and an external pump laser to maintain the population inversion. Further, the existence of χ⁽⁰⁾ < 0 has never been confirmed experimentally. Here, a completely different approach is taken to the question of χ⁽⁰⁾ < 0 and a design concept to achieve “true” χ⁽⁰⁾ < 0 is proposed based on active metamaterials with internal power sources. Two active metamaterial structures are fabricated that, despite still having their power sources implemented externally for reasons of practical convenience, provide evidence in support of the general concept. Effective values are readily achieved at room temperature and pressure and are tunable throughout the range of stability −1 < χ⁽⁰⁾ < 0, resulting in experimentally-determined magnitudes that are over one thousand times greater than those predicted previously. Since χ⁽⁰⁾ < 0 is the missing electric analog of diamagnetism, this work opens the door to new technological capabilities such as stable electrostatic levitation.     

Ultrasonic Sealing of Flexible Packaging Films – Principle and Characteristics of an Alternative Sealing Method

The closure process for packaging is a key process. It ensures the protective function of packaging and assures the packaged goods a long life. In this context, efficient and reliable sealing processes are essential for the production of sustainable packages. In this paper, several characteristics of the ultrasonic sealing process will be discussed and accompanied by experimental results. The introduction provides an insight into the ultrasonic sealing process, its heating mechanisms and the process steps. A comparison is made with conduction sealing. Furthermore, basic principles of heating and energy dissipation are related to the influences of the sealing parameters on the seam strength. The experimental studies were carried out on typical packaging films, such as polyamide‐polyethylene laminates. The seam strength in ultrasonic sealing is compared with that in conductive sealing. A lower seam strength was found for ultrasonic sealing in all the tested films. Furthermore, the sealing behaviour of the packaging films contaminated with different kinds of foods was analysed for both sealing methods. Although the ultrasonic sealing method has marginal advantages for bulk materials such as wheat flour, conduction sealing was shown to be better for other products. A comparison of the energy consumption during the ultrasonic and conduction sealing verified the advantages of ultrasonic sealing. In particular for thick packaging films, the amount of energy required for bonding is significantly lower than for conduction sealing. In summary, this paper provides a survey of the characteristics of the ultrasonic sealing method in packaging applications – its advantages and limitations. Copyright © 2011 John Wiley & Sons, Ltd.     

Conditionnements thermiques par fluide intermédiaire et accumulation d'énergie latente

As a result of direct automation of the industrial refrigerating plants the efficiency is generally reduced by: (1) not limiting the peaks of refrigeration demand; (2) not profiting by the permissible temperature variations of the stored goods; (3) allowing unstable cycles of production and distribution. From this ascertainment the authors investigate the advantages of the different forms of storing thermal energy.The conventional thermal energy storage methods are compared such as: (1) the most popular sensible heat storage by means of water or chilled water tank: (2) the storage below freezing by means of liquid solutions (salt, alcohol, glycerol, glycol…); (3) the ice accumulation systems; (4) the eutectic-plate systems. Moreover, temperature fluctuations of the stored goods in a cold store are contemplated as a posible method of storing sensible heat, if moderate (4K for frozen and 2K for fresh goods).The above-mentioned methods, using either sensible or latent heat, are compared in terms of: utilization temperature, accumulation temperature range, and storage capacity per unit mass and unit volume. Loading and unloading rates of the storage device are also significant characteristics.The development of new storage methods are then investigated mainly in respect of energy savings in the field of agro-industries requiring both refrigeration and heating. (1) The accumulation of warm water, using either electric supply during low-fare periods, or heat pumps associated to heat rejection recovery of refrigerating plants, or any combination of both sources; (2) the latent heat accumulation which allows an important space saving compared to sensible heat accumulation.The most important recent improvements are mentioned: (1) physico-chemical (supercooling, non-reversibility of the change-of-phase process, crystallizing rate and heterogeneous crystallization); (2) heat exchange problems; (3) technological constraints; (4) financial amortization.As an illustration of the advantages of heat storage, the authors present a possible application for slaughter houses aiming at energy savings by means of: (1) heat recovery from refrigerant condensation for preheating of process water, with or without thermodynamical amplification (heat pump); (2) optimization of the running cycles of the compressors and adjustment of condensing and evaporating temperature levels. The example of a 10,000 t/year slaughterhouse is presented where an eutectic accumulation device is included in the glycol-water distribution system, allowing for the transfer of a 1250 kWh refrigeration capacity from peak to low level demand periods, with a reduced volume of 25 m³.As a conclusion, the authors review the main types of application of heat storage.     

Development of a 3He Refrigerator for Possible Experiments of Solid 4He on a Small Jet Plane

The gravity on the Earth (g _E) has not been taken seriously to mask the fundamental phenomena on quantum solids, though there are some important studies on the critical phenomena of superfluid ⁴He under microgravity. We are planning to investigate the effect of gravity on the equilibrium shape of solid ⁴He. Since we had a chance to do such an experiment on a small jet plane through the ground based program by JAXA, we got started to construct a cryostat which could cool down as low as 500?mK and meet severe restrictions of experiments on a jet plane. The main part of the refrigerator was a usual ³He-evaporator pumped by a scroll pump. A?small GM refrigerator was installed to provide 4?K stage. 1?K pot was also put in which was also pumped by another scroll pump to condense ³He gas and sample ⁴He. The cryostat was designed to have two optical windows to be able to observe solid ⁴He under microgravity. In the test flight for the refrigerator, the minimum temperature of 690?mK was kept during the entire flight of two hours in which 7 to 8 times parabolic flight was performed. Each parabolic flight includes about 20?seconds microgravity and 20?seconds 1.5 to 2.0?g _E period before and after the microgravity. We did some preliminary experiments with bcc solid ⁴He under microgravity. The crystal remained stuck to the bottom of the sample cell even in the 20 seconds microgravity condition.     

Development of a proof of concept low temperature 4He Superfluid Magnetic Pump

We describe the development and experimental results of a proof of concept Superfluid Magnetic Pump in this work. This novel low temperature, no moving part pump can replace the existing bellows-piston driven ⁴He or ³He-⁴He mixture compressor/circulators used in various sub Kelvin refrigeration systems such as dilution, Superfluid pulse tube, Stirling, or active magnetic regenerative refrigerators. Due to the superior thermal transport properties of sub-Lambda ⁴He this pump can also be used as a simple circulator to distribute cooling over large surface areas. Our pump was experimentally shown to produce a maximum flow rate of 440 mg/s (averaged over cycle), 665 mg/s (peak) and produced a maximum pressure difference of 2323 Pa using only the more common isotope of helium, ⁴He. This pump worked in an “ideal” thermodynamic state: The experimental results matched with the theoretical values predicted by a computer model. Pump curves were developed to map the performance of this pump. This successful demonstration will enable this novel pump to be implemented in suitable sub Kelvin refrigeration systems.