Hasil untuk "Low temperature engineering. Cryogenic engineering. Refrigeration"

T. Tritt, M. A. Subramanian

Li Guangye, Zhao Songsong, Liu Bin et al.

A novel intelligent defrosting control strategy based on the parallel-plate capacitor principle was investigated to address the issue of the “erroneous defrosting” of an evaporator. A mathematical model of a parallel-plate capacitor was established in the process of frosting and defrosting of the evaporator, and a theoretical analysis of the effects of the air/frost/water intermediate medium proportions on the capacitance value was conducted. The capacitance value showed a gradual linear growth during the frosting process, whereas it first rose and then fell during the defrosting process. This study considered a cold storage evaporator as the research object and constructed a capacitance defrosting control system. The experimental results were consistent with the theoretical analysis results for the capacitance variation trend. The results showed that 32.0 pF and 19.0 pF could be used as the start and stop points for intelligent defrosting control, respectively. The fluctuation range for the central temperature in the cold storage was reduced by 12.0 ℃. The defrosting cycle time was shortened by approximately 4 min. The defrosting efficiency increased by approximately 22%. The defrosting power consumption was reduced by 36.74%, and the total power consumption of the refrigeration system was reduced by 19.8%.

Zhou Yujue, Huang Zhaobin, Xu Zhenkun et al.

To address the issues of poor air quality and the lack of fresh air in traditional variable refrigerant flow （VRF） systems， VRF systems and fresh air units are commonly used in combination in practical engineering applications. However， these systems are typically controlled independently. To achieve coordinated operation between VRF systems and heat-recovery fresh-air units， a new integrated VRF fresh-air system was developed， with the aim of reducing system energy consumption and improving indoor comfort and air quality. Based on the full-condition performance model of the VRF system and the characteristics of the heat-recovery unit， simulation analyses were conducted to evaluate the energy-saving effects of conventional VRF systems and of three types of integrated VRF fresh-air systems in residential buildings in Nanjing and Beijing. The results indicate that， compared with conventional residential VRF fresh-air systems， the system equipped with a constant air volume heat-recovery unit significantly reduced the operational energy consumption， achieving annual energy savings of 20.7% and 30.6% in Nanjing and Beijing， respectively. The energy-saving performance was positively correlated with the severity of cold-climate conditions. During the heating season， the new integrated system prioritizes the use of the heat-recovery mode and minimizes the fresh air volume. During the cooling season， the energy-saving performance can be further improved by introducing a bypass branch and combining it with a variable air-volume control strategy. Compared to the primary baseline system， the combined VRF fresh-air system achieved cooling-season energy-saving rates of 2.77% and 15.31% for Nanjing and Beijing， respectively.

Y. Ohki

Measurement of the complex permittivity of a substance in a wide frequency range, for example, from 10 mHz to 100 kHz, provides useful information on the dielectric properties of the substance. In this regard, some of such dielectric properties can be analyzed more clearly if we pay attention to the frequency spectra of electric modulus, which is a reciprocal of complex relative permittivity. Especially, the imaginary part of the electric modulus can be a powerful tool for dielectric materials research. In this paper, this fact is demonstrated clearly by showing abundant examples acquired by the author's laboratory. First, the equations of electric modulus that hold for various dielectric relaxation processes, including their derivation, are shown in an easy‐to‐understand manner. After that, for several insulating polymers, actual measurement examples of broadband complex permittivity spectra are shown, up to frequencies of about 100 kHz and a much broader range up to several THz. In the first example of showing permittivity spectra, polyamide exhibits an incredibly high relative permittivity value of 106 at high temperatures such as 200 °C at a frequency as low as 10 mHz. This is a result of the phenomenon often called electrode polarization. In other words, if electric charge carriers accumulate in an insulator facing a nearby electrode and have the polarity opposite to that of the electrode, the permittivity of the insulator goes up. In such a case, the dielectric loss factor usually shows a very high value in the low‐frequency range and decreases in inverse proportion to the frequency. This reflects the fact that the charge carriers are transported, and the conductivity can be derived from this frequency dependence much more easily with apparently higher reliability than measuring the dc leakage current. Furthermore, it is shown that the coefficient of thermal expansion can be estimated from the permittivity spectra relatively accurately for several polymers that satisfy the necessary condition. Next, taking examples in electric modulus spectra measured in important insulating polymers such as engineering ones, it is demonstrated that the processes of dielectric polarization and relaxation, which are difficult to see in permittivity spectra, can be recognized obviously. Moreover, the effects of the addition of nanosized or microsized fillers to epoxy resin on its thermal property and filler‐induced inhomogeneity are analyzed using the electric modulus spectra measured in these samples. The effects of thermal aging treatment and simultaneous aging treatment with heat and radiation on the degradation of cross‐linked polyethylene are also analyzed by paying attention to the frequency spectra of its imaginary electric modulus. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Jens O. M. Karlsson, M. Toner

Ekejiuba Aib

The first in the series of Azuberths Game Changer publications “Synergy of the Conventional Crude Oil and the FT-GTL Processes for Sustainable Synfuels Production: The Game Changer Approach-Phase One Category” a.k.a. (DOI: 10.23880/ppej16000330) is targeted at reducing 80 per cent CO2 emissions from the internal combustion engines by upgrading from the conventional crude oil refinery products to the synthetic fuels products (ultra-low-carbon fuels). This paper will focus on the complete elimination of the remaining 20 per cent CO2 emissions (i.e. to achieve zero- CO2 emissions) in transportation and power generating internal combustion engines as well as in the other centralized emissions/emitters such as petroleum industry flare lines, industrial process and big technology industries scrubber flue gas, et cetera. This invention stems from similar biblical quote {Isaiah 6:8-New International Version (NIV)} which states, and then I heard the voice of the Lord saying, “Whom shall I send? And who will go for us?” And I (Isaiah) said, “Here am I. Send me!” Laterally, in this case I (Azunna) said, “Here am I. Please use me”. Hence the aftermath, IJN-Universal Emissions Liquefiers is a plug and play units for all categories of pollutants discharge into the atmosphere. The work is motivated by the scientific facts that (i) The release of CO2 from automotive exhaust effluents, industry vents and flue gas emissions into the atmosphere contributes to greenhouse gas (GHG) accumulation causing global warming hence climate changes issues such as flooding of coastlines/sea-rising, melting of the glaciers, disrupted weather patterns, bushburning/wildfire, depletion of Ozone layer, smog and air pollution, acidification of water bodies, runaway greenhouse effect, etc. (ii) Every gas stream (e.g., flue gas) can be made liquid by e.g. a series of compression, cooling and expansion steps and once in liquid form, the components of the gas can be separated in a distillation column. (iii) Captured liquefied gases can be put to various uses, especially carbon dioxide (CO2 ), which can be used for the production of renewable energy via Synfuels such as the e-fuel/solar fuel. The natural atmosphere is composed of 78% nitrogen, 21% oxygen, 0.9% argon, and only about 0.1% natural greenhouse gases, which include carbon dioxide, organic chemicals called chlorofluorocarbons (CFCs), methane, nitrous oxide, ozone, and many others. Although a small amount, these greenhouse gases make a big difference - they are the gases that allow the greenhouse effect to exist by trapping in some heat that would otherwise escape to space. Carbon dioxide, although not the most potent of the greenhouse gases, is the most important because of the huge volumes emitted into the air by combustion of fossil fuels (e.g., gasoline, diesel, fuel oil, coal, natural gas). In general, the major contributors to the greenhouse effect are: Burning of fossil fuels in automobiles, deforestation, farming processing and manufacturing factories, industrial waste and landfills, increasing animal and human respiration, etc. The increased number of factories, automobiles, and population increases the amount of these gases in the atmosphere. The greenhouse gases never let the radiations to escape from the earth atmosphere and increase the surface temperature of the earth. This then leads to global warming. The petroleum industry well sites vent/flare gases (methane, ethane, propane, butanes, H2 O (g), O2 , N2 , etc.). Internal combustion engines (automobiles-cars, vehicles, ships, trains, planes, etc.) release exhaust effluents (containing H2 O (g), CO2 , O2 , and N2 ); steam generators in large power plants and the process furnaces in large refineries, petrochemical and chemical plants, and incinerators burn considerable amounts of fossil fuels and therefore emit large amounts of flue gas to the ambient atmosphere. In general, Flue gas is the gas exiting to the atmosphere via a “flue”, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. The emitted flue gas contains carbon dioxide CO2 , carbon monoxide CO, sulphur oxide SO2 , nitrous oxide NO and particulates. Furthermore, GTL plants produce CO2 , H2 O and waste heat, while both pyrolysis and gasification plant generate gaseous products consisting of (a mixture of non-condensable gases such as H2 , CO2 , and CO and light hydrocarbons “e.g. CH4 ” at room temperature, as well as H2 O (g), O2 and complex hydrocarbons e.g. C2 H2 , C2 H4 , etc.). In general, all combustion is as a result of air-fuel mixture burning (i.e. air or oxygen mixing directly with biomass/ coal or with liquid/gaseous hydrocarbon inside internal combustion engines), releases carbon dioxide and steam (H2 O) back into the atmosphere as well as producing energy for work. Specifically, during combustion, carbon combines with oxygen to produce carbon dioxide (CO2 ). The principal emission from transportation and power generating internal combustion engines is carbon dioxide (CO2 ). The level of CO2 emission is linked to the amount of fuel consumed and the type of fuel used as well as the individual engine’s operating characteristics. For instance, diesel-powered engines have higher emission than petrol/gasoline-powered engines. Although emphasis is places more on CO2 , this investigation is ultimately concerned with the real-time liquefaction of all the components of gaseous release/emissions -related to air pollution/health problem. It is believed that the mortality rate from air pollution is eight times larger than the mortality caused by car accidents each year. Pollutants with the strongest evidence for public health concern include particulate matter (PM), ozone (O3 ), nitrogen dioxide (NO2 ) and sulphur dioxide (SO2 ). All the exhaust effluents gases/flue gas and vent/flare gases are captured by liquefying them and then put to various uses, to achieve “Net zero” emissions. Fundamentally, the objective of the present invention is to develop a compact device (Universal Emissions Liquefiers) that can be retro-fitted onto the exhaust tailpipe-end of the internal combustion engines (diesel-powered, gasoline-powered, and hybrid automobiles-cars, vehicles, SUV’s, trucks, motor cycles, tri-cycles, portable electric generators, sea and cargo ships/ boats, trains, planes, rockets, etc.) and outlet of industrial machines that release flue gases through exhaust/scrubber channels, as well as crude oil, refined products storage tanks that vent greenhouse gases into the atmosphere, coal processing units/ plants and turn them into liquid { CO2 (l), N2 (l), O2 (l), etc.} or powdered components or chemically transform them in realtime with selective catalysts to any other specific compound, e.g. treating CO2 with hydrogen gas (H2) can produce methanol (CH3 OH), methane (CH4 ), or formic acid (HCOOH), while reaction of CO2 with alkali (e.g. NaOH) can give carbonates (NaHCO3 ) and bicarbonates (Na2 CO3 ). Nitrogen (N2 ) to ammonia (NH3 ) or Hydrazine (N2 H4 ), and molecular oxygen (O2 ) to hydrogen peroxide (H2 O2 ), et cetera. Alternatively, in new automobiles designs, the universal emissions liquefiers’ device can be directly net-worked on the floor alongside the catalytic converters and may eliminate the need for muffler/silencer/resonator. This is achieved by the application of any of the five main gas capture/separation technologies: Liquid absorption, Solid adsorption, Membrane separation (with and without solvent- organic or inorganic), Cryogenic refrigeration/distillation, and Electrochemical pH-swing separation or their combination to selectively trap and liquefy the individual pollutants. According to the fact from CarBuster, almost 0.009 metric tons of carbon dioxide is produced from every gallon of gasoline burned, which means that the average car user makes about 11.7 tons of carbon dioxide each year from their cars alone

Yuan Fang, K. Bakian-Dogaheh, J. Stang et al.

Objective: To develop a new class of emulsions using a protein-based emulsifier as the coupling fluid for microwave imaging systems. Methods: In this paper, we provide a theoretical basis for engineering shelf-stable dielectric fluids, a step-by-step formulation method, and measurements of complex dielectric properties in the frequency range of 0.5-3 GHz, which can be applicable for many of the recent microwave imaging systems. Results: This medium was primarily designed for long-term stability while providing a controllable range of complex dielectric permittivities given different fractions of its constituents. Consequently, this emulsion shows dielectric stability in open air throughout a 7-day experiment and temperature insensitivity over the range of 0${\,^\circ }$C to 60${^\circ }$. Conclusions: This control over dielectric permittivity enables formulations that tune the background-to-target contrast to the linearizable regime of iterative inverse scattering algorithms. Accordingly, the emulsion conductivity can also be controlled and reduced to maintain the required signal-to-noise ratio within the dynamic range of the imaging system. The new formulation overcomes the practical challenges of engineering coupling fluids for microwave imaging systems, e.g., temporal stability, non-toxic, low sensitivity to temperature variation, and easy formulation from readily available and inexpensive materials. Significance: The achieved properties associated with this new fluid are of particular benefit to microwave imaging systems used in thermal therapy monitoring.

A. Mehmanparast, Azenor Vidament

Abstract Offshore wind turbines are subjected to cyclic loading conditions during their operational lifespan which is typically between 20 and 25 years. An important issue in fatigue design and integrity assessment of offshore wind turbine foundations is the examination of the long-term fatigue and corrosion-fatigue behaviour of steel structures in the high cycle region. High cycle fatigue tests, particularly at low frequencies in a seawater environment, are time-consuming and costly. Therefore, there is an essential need to perform accelerated tests to predict the long-term behaviour of the structures under realistic operational loading conditions. In this work, the existing fatigue acceleration mechanisms have been reviewed and a novel methodology has been proposed for accelerated testing and analysis of fatigue data in different environments (i.e. air, salt-spray and seawater) at higher temperatures. Two distinct equations have been developed and proposed for the calibration and prediction of S-N fatigue life and crack growth behaviour of steels in different environments. The proposed methodology has been validated through comparison with the existing data in the literature and predictions have been made at operational temperatures using high temperature data. The proposed approach is relatively simple to calibrate for a material of interest and enables accelerating S-N fatigue and crack growth testing of the examined materials by a factor of two and three, respectively. The proposed methodology and the obtained results have been discussed in terms of the need for accelerated testing for fatigue design and integrity assessment of offshore wind monopiles, especially those which are close to the end of initial design life and need a comprehensive engineering analysis for life extension or decommissioning.

I. A. Korotkiy, E. Neverov, P. Korotkikh et al.

The article presents the results of developing a system for utilization of condensation heat from refrigerating units and air-conditioning systems of ice fields to decrease the dependency of engineering and technical systems of the objects on municipal systems of heating and hot water supply. The proposed solution provides saving of heat and electric energy consumed by both the refrigeration supply system and other systems of the object. When compressed gas overheating is used, an addition heat exchanger is added to the revegetating circuit allowing to utilize up to 20 % of heat released by the unit. As the temperature of refrigerating medium may be above 100 °C in the end of compression process, the environment (water or air) is heated up to 80–90 °C. The technology has been developed for Small Ice Hockey Arena and Ice Hockey Training Rink in Sochi Olympic Park. The IIR conference series on Sustainability and the Cold Chain is recognised as a cutting-edge event on the cold chain which addresses the ever-increasing demand for knowledge-sharing in this essential sector. This prestigious biennial conference attracts international audiences of researchers and industrialists, providing an opportunity to showcase the latest developments in sustainability, retail refrigeration and the cold chain.

Cao Xiang, Zhang Chunlu

A stepped pressure cycle is proposed to improve the energy efficiency of refrigeration and heat pump cycles. By constructing multiple suction and discharge pressures, the refrigerant temperatures in the evaporators and condensers underwent step changes and approached the heat source temperatures. This helps to improve heat transfer efficiency and reduce the compression ratio. However, we found that the conclusion of energy savings for the stepped pressure cycle is conditional. Over 6.5% of the energy-saving potential is reduced because of inefficient heat exchangers or a small temperature glide of the heat transfer fluid. Moreover, an excessive subcooling degree will lead to a worse COP than a simple cycle. Finally, in this study, some application cases are summarized to demonstrate the energy-saving potential of the stepped pressure cycle.

S. Gredeskul, L. Pastur, Y. Freĭman

The paper describes the decisive role by B. I. Verkin, the founder of the Institute for Low Temperature Physics and Engineering (ILTPE) and the journal Low Temperature Physics, in the return from the near 50-year oblivion the name of L. V. Shubnikov, an outstanding Soviet physicist arrested and executed in 1937. We begin with a brief survey of Shubnikov’s works, several of them are of the Nobel prize level. Then we briefly describe the foundation by B. I. Verkin of the Institute for Low Temperature Physics and Engineering. Finally, we outline the history of writing the book about Shubnikov and the outstanding efforts by B. I. Verkin in the realization of this last, according to him, achievement of his life.

K. Hart, R. Dunn, E. Wetzel

Fused filament fabrication (FFF) is the most common additive manufacturing technology, but parts fabricated using FFF lack sufficient mechanical integrity for most engineering applications. Herein, a dual material (DM) filament comprising acrylonitrile butadiene styrene (ABS) with a star‐shaped polycarbonate (PC) core is fabricated using a novel thermal draw process. This DM filament is then used as feedstock in a conventional FFF printer to create 3D solid bodies with a composite ABS/PC meso‐structure. Subjecting these parts to annealing temperatures intermediate between the glass‐transition temperatures of ABS and PC produces a solid body with ductility comparable to injection‐molded ABS and fracture toughness values 15 × higher than comparable as‐printed ABS structures. The PC skeleton of specimens fabricated using the DM filament resists creep and polymer relaxation to maintain accurate part geometry during annealing. This novel DM filament can revolutionize additive manufacturing allowing low‐cost printers to produce parts with mechanical properties competitive with injection‐molded plastics.

Meiling Fan, Chunhong Nie, Huan Du et al.

Abstract Facing increasing challenges to oil field production and energy utilization, tertiary oil recovery technologies, exemplified by alkali-surfactant-polymer (ASP) flooding, can significantly improve the oil recovery. However, it has produced an enormous amount of highly emulsified water to increase the tough water treatment in the oilfield. Currently, the dominated treatments have been focused on the traditional treatment methods, such as the thermal demulsification, electric demulsification and gas flotation demulsification. These technologies have high energy consumption and low efficiency, which blocks their wide applications in engineering. In this paper, we first performed a solar-driven sustainable demulsification by adopting the highly emulsified water produced from ASP flooding in the oilfield. The solar energy has three-fold effects, i.e. the photo, thermo and electrochemical action, on the demulsification. The solar thermal and electrochemical process serves as controlling domains for the thermo-aided electrochemical oxidation and separation to break the organic surfactants and polymers in the O/W interface. For an insight into solar demulsification, we monitored the variation of the viscosity, zeta potential, particle size, rheology and percent removal of the highly emulsified water in the real time. The results show the achievements of the solar O/W demulsification and separation via the five measurable parameters dominated by three solar based fields. The viscosity of the highly emulsified emulsion was decreased from 1.41 mPa s to 1.0 mPa s. The negative zeta potential was increased, which means that the repulsive electrostatic force among oil droplets was reduced. The viscoelasticity of the O/W interface was decreased, so the strength of the interface film was decreased. By monitoring the variation of the oil droplet size and distribution, it can be concluded that the mechanism of solar demulsification is a process in which the oil droplets conduct to continuously flocculate and coalesce, finally creaming or sedimentation. The percent removal reached 82.84% at a 60 °C temperature under the condition of 7 V potential driven by the light radiation. Further characterizations show that solar energy has a great effect on treating highly emulsified water produced from oilfields with low energy consumption and environmental protection.

A. Cunha, Sandi Souza

The analysis of organic regenerative cycles is necessary to verify the possibilities of increasing the work and efficiency of a thermodynamic cycle according to some control parameters. The results obtained from this work can be beneficial in several areas such as solar thermal energy. Simulations of an organic regenerative cycle with up to 4 extractions were carried out in order to analyze the behavior of maximum efficiency and the work generated in the turbine. R134a was used as an organic fluid, used in low temperature cycles. Evaporation temperature data between 60°C and 100°C and superheat temperatures equal to 120°C, 200°C and 300°C were tested for cycle analysis. Thus, it was possible to verify the work behavior and maximum efficiency depending on the number of extractions, superheating temperature and evaporation temperature. The models and simulations were made using the Engineering Equation Solver (EES) software and the results were analyzed in Excel. It was concluded that the maximum efficiency increases with the increase of the evaporation temperature and the number of extractions and decreases with the increase of the superheat temperature. The turbine work grows by increasing the evaporation and superheat temperatures, but decreases with the increase in extractions.

A. Sidiqa, Andri Hardiansyah, E. R. Chaldun et al.

Various bioceramic materials including zirconia and hydroxyapatite have been developed for various applications. Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is one of the most interesting features of calcium phosphate-based bioceramic that widely used in various applications especially for bio-application, bone engineering, and dentistry. However, the applications of pristine HAp have limited due to low load bearing applications. The wet chemical precipitation techniques was used to synthesize the solids based on zirconia. Hydroxyapatite and zirconia powder (0-30 weight %) were mixed homogeneously. Structure and morphological were characterized by SEM JEOL-JSM-T330A. The presence of functional group was observed by FTIR. Hardness value of material was measured by using Vickers hardness test measurement. Through this techniques, pure hydroxyapatite precipitate was obtained. Sintering temperature is an important factor that could influence the hardness of zirconia-doped hydroxyapatite. Based on the SEM observation, zirconia-doped hydroxyapatite were developed in blended morphology. FTIR results shows the interaction between hydroxyapatite and zirconia. Increasing zirconia increased the hardness value of zirconia-doped hydroxyapatite. Eventually, these ceramic-based materials could be developed for dental materials applications.

F. Millet, L. Tavian, U. Cardella et al.

In the framework of an international collaboration, a 100 TeV hadron collider in a 100-km long tunnel is under study as a future circular collider beyond LHC at CERN. Its design is based on 16-T superconducting magnets cooled at 1.9 K by 10 cryoplants with a unit equivalent capacity of 100 kW at 4.5 K, up to 4 times larger than the present state-of-the-art. Half of the entropic refrigeration load is due to the synchrotron radiation produced by the high-energy proton beams and deposited on beam screens cooled between 40 and 60 K. This non-conventional thermal load distribution is an additional challenge for the cryogenic system. An engineering study on FCC-hh cryoplants is in progress with world-leader industries to define the preliminary conceptual design of industrial solutions and to confirm innovative technologies. The paper recalls the FCC-hh cryogenic requirements, presents the main results of Linde Kryotechnik study and highlights some identified R&D efforts.

Kai Wang, Mao-zheng Chen, B. Xiang et al.

Microwave receiver system is signal receiving equipment in radio astronomical observation. Through refrigeration, we can greatly reduce the noise temperature of receiver, but the dewar has more than 200 K temperature difference between inside and outside, and the vapor will freeze on the surface of vacuum window to effect observation. The aerating system is a pneumatic control system, it supplies dry air and exhausts old for dry air cavity of receiver. Three cryogenic receivers of Nanshan 26 m radio telescope were equipped with aerating systems, but they were independent each other. The public aerating system could not only realize to supply dry air for three cavities, but also had a simpler structure with only one inflator. Compared with the test results of original systems, the public aerating system could make the pressure of each cavity more stable, and keep dry for each vacuum window of cryogenic receivers very well. Introduction The microwave receiver is a device which collects the electromagnetic wave signal from the telescope and amplifies the radio frequency(RF) signal through a low noise amplifier(LNA) [1,2], and then outputs it to backend after mixing, intermediate frequency(IF) amplification and filtering[3]. Because the signals received in radio astronomical observation are extremely weak, the sensitivity of receiver is highly demanded for radio telescope[4]. The noise temperature is an important parameter to measure the sensitivity of receiver. The lower the noise temperature, the higher the sensitivity. Because refrigeration can reduce the noise and enhance the sensitivity of microwave devices, it is necessary to provide a low temperature environment for microwave devices of the receiver, so that the temperature of these devices can be reduced to below 20K. A common method is to design a special dewar cavity for refrigeration to install and place these cryogenic microwave devices. A kind of cryogenic receiver with external feed is shown in Fig. 1(a). This design is generally due to the large feed size of the long cm band receiver, which cannot be cooled as a whole, so the receiver feed is placed outside the dewar. The RF signal first passes through the normal temperature feed to the vacuum window, and then passes through the vacuum window to the low temperature ortho-mode transducer(OMT) [5] and LNA in the dewar. The other kind is shown in Fig. 1(b). This design is due to the small feed size of the short cm or mm band receiver, which is convenient to place the feed and other microwave devices in the dewar as a whole to be cooled together. Regardless of whether the feed of the receiver is refrigerant, there are three points to consider. First, the vacuum window needs to be sealed to ensure the vacuum in the dewar cavity; secondly, the sealing material needs to hold the pressure of an atmospheric pressure; finally, the sealing material needs to have as little insertion loss as possible to the incident signal [6]. Because the temperature of sealing material is between 80 K and 300 K during the operation of cryogenic receiver, if it is exposed directly in the air, the water vapor in the air will adhere to the surface of cryogenic sealing material and be frozen. This will not only corrode the sealing material, but also increase the insertion loss and standing wave of the receiver, thus affecting the performance of the receiver.

S. Upadhyaya, V. Gumtapure

This paper presents the analysis of organic Rankine cycle (ORC) using hydrofluoroethers (HFEs) such as HFE7000, HFE7100 and HFE7500 as working fluids under external conditions. HFE's has been chosen over chlorofluorocarbons (CFC's) and hydro chlorofluorocarbons (HCFC's) as it is environmentally friendly. Both the CFC's and the HCFC's possess ozone depletion potential (ODP), while the hydrofluorocarbons (HFC's) have relatively significant global warming potential (GWP). The HFE's that have excellent thermophysical properties and low toxicity can be recommended as a long term solution to the environmental issues. The HFE's have zero ODP and very low GWP compared to the CFC's, HCFC's and HFC's. A thermodynamic model has been developed using Engineering Equation Solver (EES) software to simulate the system under steady state conditions. Parametric analysis is conducted to examine the effects of some thermodynamic parameters on the system performance using different working fluids. When turbine inlet temperature was varied from 70°C to 110 °C keeping condensation temperature fixed at 28 °C, HFE7000 produces the maximum thermodynamic efficiency and performs better in view of the net work output under the given working conditions. However, when evaporation pressure was kept constant at 1.2 bar and condensation temperature was varied from 20°C to 30 °C, HFE7500 produced the maximum efficiency of 12.3% in comparison with 7.6% for HFE7100 and 4.1% for HFE7000. The work demonstrates the use of hydrofluoroethers as working fluid in ORC.

Peng Liu, Yuntao Song, Yuntao Song et al.

Abstract Monoblock technology with CuCrZr as the structural material is the standard divertor target design for the initial phase of the China Fusion Engineering Test Reactor (CFETR). The design concept with China Low Activation Martensitic (CLAM) steel as the structural material provides another candidate solution for the CFETR divertor target. This paper presents a design study of an optimized monoblock to meet the requirements for CFETR operating conditions, which establishes a good basis for engineering design of CFETR. The monoblock uses tungsten as armour and CLAM steel as the structural material, with a copper interlayer. The operating temperature window of CLAM steel was determined by irradiation embrittlement, softening, and other aging effects. Initial design rules for the W/CLAM monoblock were checked; thermal results by finite element analysis (FEA) show that the design concept is able to withstand a heat flux of 10 MW/m2 after examining the temperature for each material and the margin to the wall critical heat flux (WCHF) on the tube. Mechanical results indicate that the CLAM steel meets the ITER SDC-IC elastic rules under potential irradiation level of CFETR, irrespective of residual stress. Also the fatigue criteria were checked for unirradiated conditions with a reasonable life time of 16,000 cycles.

Zhou You, Zhang Xinqiang, Wang Shuangfeng

Elliptical tube heat exchanger has been widely used in heat exchange equipment due to its good flow and heat transfer characteristics. In this paper we use computational fluid dynamics method to simulate the flow field and sound field generated by the indoor unit of air conditioner with elliptical finned tube heat exchanger , and make comparison with circular tube heat exchanger. The results show that for the inside the cross-flow, the structure of tubes in heat exchangers has no effect on the location and size of the eccentric vortex; compared with the circular tube finned heat exchanger with the same cross-sectional area, the air conditioners using elliptical tubes work better on increasing the air volume, improving cooling effect and reducing noise especially low-frequency noise under the same conditions. Above all, the conditioner using elliptical tubes in which the ratio of the long axis and short axis is 2.0 can reduce noise 4 dB.