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1.
As an environmentally harmless and feasible alternate refrigerant, CO2 has attracted worldwide attention, especially in the area of automobile air-conditioning (AAC). The thermal property of CO2 and its trans-critical refrigeration cycle is very different from that of the traditional CFC or HCFC system. The detailed
process of CO2 system thermal cycle design and optimization is described in this paper. System prototype and performance test bench were
developed to analyze the performance of the CO2 AAC system. 相似文献
2.
A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results show that CO2 Brayton cycle proves to be superior to the air Brayton cycle in terms of the system net output power, thermal efficiency and recovery efficiency. In most cases, the recovery efficiency of CO2 Brayton cycle can be higher than 9% and the system has a better performance at the engine’s high operating load. The thermal efficiency can be as large as 24.83% under 100% operating load, accordingly, the net output power of 14.86 kW is obtained. 相似文献
3.
Mechanicalvapourcompressioncyclesaremainlyemployedinmostrefrigerationsystems .Chlorofluoro carbons(CFCs)orhydrochlorofluorocarbons(HCFCs)aregenerallyusedasrefrigerantsinthesesystemsdrivenbyelectricityfromburningfossilfuels ,whichresultsino zonedepletionduetotheleakageandpoorrecoveryofthoseman maderefrigerants,andglobalwarmingowingtoCO2 emissionfrom powerstationsandthereasonisthatCFCsorHCFCsarepowerfulgreenhousegases.Inaddition,otherenvironmentalissuesarealsocausedbytheNOx,SO2 andpartic… 相似文献
4.
针对二氧化碳热泵性能改进问题,设计了一个基于循环模拟模型开展仿真模拟研究。通过改变该模型的输入参数和运行条件,研究模型的最佳工作条件及性能提高的途径。提出了采用中间冷却器的双级压缩机和带有膨胀箱的双级压缩机的工作模型,并对该模型进行仿真测试,结果表明最多可以比传统的工作系统提高跨临界二氧化碳循环20%的加热性能和28%的制冷性能。 相似文献
5.
在汽车空调中，具有对环境友好性和优良的热物理特性的天然工质CO2与其他制冷剂相比有独特优势。近年来，美国、欧洲和日本等发达国家和地区的研究者们不断尝试将CO2应用于各种可能的制冷、空调和热泵系统，本文从制冷剂的替代、跨临界循环以及汽车空调特点上阐明无毒、不可燃的二氧化碳制冷剂将是下一代汽车空调的首选。 相似文献
6.
Intheapplicationsofindustrialandcommercialrefrig erationsystem ,iftherequiredrefrigerationtemperatureisverylow ,theconventionalvaporcompressionsystemisdiffi culttomeettherequirementbecausewhenthedifferencebe tweentheevaporatingtemperatureandthecondensingtemper atureissohighthatitishardtofindarefrigeranttomeettheneedsasthecondensingpressureisnottoohighandtheevap oratingpressureisnottoolow .Whentherefrigeratingtemper atureisverylow ,thecascaderefrigerationcycleissuitabletobeused .Itcannotonlysat… 相似文献
7.
Attheendoftheyear2000,annualglobalfluo rocarbonrefrigerantemissionfrommobileandunitaryairconditioningequipmentsislikelytosurpass100000tons,correspondingtoaglobalwarmingim pactofmorethan150milliontonsofCO2.Evenlar gerindirectCO2emissionresultsfromthegeneration ofpowerconsumedtodrivethesystems[1].Within creasingfocusongreenhousegasemissionreductions,strictregulationsontheuseofsynthesizedrefrigerants suchasHCFCsandHFCsmaybeexpected,possiblyfollowedbyphase outtargetsanddates.Theinterna tionale… 相似文献
8.
文章分析了温度和CO2浓度实时控制原理和实现的方法，介绍了以单片机为基础的一个实时控制电路。 相似文献
9.
随着CFC和HCFC类物质淘汰进度的加快,液氨毒性和安全性的限制,CO2作为制冷剂的使用也越来越被人们看好。CO2／NH3复叠式制冷技术的提出和应用在国内虽然做了不少的研究和试验,但是大多集中在系统循环的分析和系统的优化。本文从CO2／NH3复叠式在冷冻冷藏工程中的应用方面对有关技术问题进行了分析。 相似文献
10.
对光自差阵列探测CO2激光相干雷达进行了研究，通过对大量红外光学系统的分析，提出了一种适用于光自差阵列探测激光相干成像的光学头系统，并对该光学头系统进行了设计和实验性能测试，该光学头系统可实现光束的一维扩展，其纵横向扩展比为1：32。 相似文献
11.
研究前驱物浓度、超重力大小、反应时间、反应温度和反应介质体系的条件对Co3O4前驱物形貌的影响,发现制备花状Co3O4前驱物的最优条件是Co(NO3)2·6H2O和CO(NH2)2在1000/g超重力场、溴苯/水溶液体系、100℃条件下水热反应反应30min,通过前驱物的热分解制得Co3O4,采用SEM和XRD对样品的形貌和物相进行表征。将Co3O4粉末分别与乙炔黑、聚四氟乙烯(PTFE)按一定质量比混合压在镍网上,制成电极片,通过CV测试其电性能,结果发现超重力越大,制备的材料的交流阻抗值越小。 相似文献
12.
In order to utilize solar energy effectively and to achieve a higher electrical efficiency by limiting the operating temperature of the photovoltaic （PV） panel, a novel photovoltaic/thermal solar-assisted heat pump （PV/T-SAHP） system was proposed and constructed. The hybrid solar system generates electricity and thermal energy simultaneously. A distributed parameters model of the PWT-SAHP system was developed and applied to analyze the system dynamic performance in terms of PV action, photothermal action and Rankine cycle processes. The simulation results indicated that the coefficient of performance （COP） of the proposed PV/T-SAHP can be much better than that of the conventional heat pump. Both PV-efficiency and photothermic efficiency have been improved considerably. The results also showed that the performance of this PV/T-SAHP system was strongly influenced by the evaporator area, tube pitch and tilt angle of the PV/T evaporator, which are the key factors in PV/T-SAHP system optimization and PV/T evaporator design. 相似文献
13.
方金湘 《岳阳职业技术学院学报》2007,22(1):64-66
随着对环境问题的关注,CO2以其优良的热物性,成为制冷剂中具有良好发展前景的天然工质。本文通过介绍CO2制冷剂组成的热泵系统采用跨临界循环的方式为汽车冬季供暖的分析,讨论此种方式的优缺点及改进方法。此外,还对汽车空调冬季供暖节能方法进行了可行性探讨。 相似文献
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15.
Jun-chun ZHANG Le-ming CHENG Cheng-hang ZHENG Zhong-yang LUO Ming-jiang NI 《浙江大学学报(A卷英文版)》2013,14(9):671-678
In this study, a porous inserted regenerative thermal oxidizer （PRTO） system was developed for a 125 kW industrial copper-melting furnace, due to its advantages of low NOr emissions and high radiant efficiency. Zirconium dioxide （ZrOz） ce- ramic foams were placed into the combustion zone of a regenerative thermal oxidizer （RTO）. Different performance characteris- tics of the RTO and PRTO systems, including pressure drop, temperature distribution, emissions, and energy efficiency, were evaluated to study the effects of the porous inserts on non-premixed CH4 combustion. It was found that the PRTO system achieved a significant reduction in the NOx emission level and a fuel saving of approximately 30% compared to the RTO system. It is most suitable for a lean combustion process at an equivalence ratio 〈0.4 with NOx and CO emission levels within 0.002%~）.003% and 0.001%q3.002%, respectively. 相似文献
16.
A proportion of children with physical impairments experience significant difficulties in communicating with others and may be recommended augmentative and alternative communication (AAC) systems such as speech synthesizers and symbol charts to support ‘natural’ communication skills. However, AAC systems are often under-utilized. Parents have identified barriers to AAC system use to include the organization of speech and language therapy. Speech and language therapists are developing services to school-aged children in response to changes in education, health reforms and models of speech and language development. However, there is little evidence for commissioners of children's services about what constitutes ‘enough’ or ‘good’ speech and language therapy. This paper examines speech and language therapy provision to 23 children using AAC systems in six London authorities. Research strategies include documenting the amount, type, organization and objectives of provision. Evidence for collaboration between school staff and therapists is explored, analysis is made of child characteristics associated with provision and criteria for decision-making documented through interviews with therapists. However, little conjunction exists between what therapists said guided their decision-making concerning provision and observed provision. For the children surveyed in this study it seems that that provision in amount of therapy is related to educational placement rather than individual needs. 相似文献
17.
基于质子交换膜燃料电池的天然气微型热电联产系统的核心单元是重整制氢反应器．设计研发了一种集蒸汽发生和天然气水蒸汽氧化重整于一体的制氢反应器,实验测试了典型工况下反应器的性能,以及操作条件（水碳比、空碳比、空速）对反应器性能的影响．在典型操作条件下,反应器平均床层温度为630℃,反应器出口合成气的物质的量组成为H。40．61％、N。37．63％、CO5．56％、CH43．62％、C0212．58％,甲烷的转化率为92．56％,反应器能量利用效率88．3％．实验表明这种制氢反应器可用干微型天蚨气执由群声桑缔 相似文献
18.
The characteristics of friendships among children who use augmentative and alternative communication (AAC) are not well understood. Research on friendships among children without disabilities has identified similarity to each other as a key characteristic among friends. The aim of this study was to identify and describe the friendships between students using AAC and fellow students in Norwegian mainstream public schools. Participants were students using AAC in first to fourth class, fellow students, parents, and staff. Data were analysed using a constructive grounded theory approach. The participants provided diverse reports about the friendships, although all students using AAC reported having friendships at school. The friendships were described by parents and staff as superficial and students using AAC were seldom perceived as playmates by fellow students. The results indicated that friendships between students using AAC and fellow students were often unilateral. The results are discussed along with the implications for future research. 相似文献
19.
Lauran Doak 《Journal of Research in Special Educational Needs》2021,21(3):198-210
Augmentative and Alternative Communication (AAC) is a core component of special education for many children with learning disabilities and/or autism who have minimal or no speech. Much literature focuses on implementation of AAC in the classroom or therapy setting, but less is known about how AAC is used in the family home. Few studies are authored by an AAC parent/researcher with reflection on positionality, power and the advantages conferred by ‘insider’ status. This paper addresses this gap by exploring the perspectives of five families of minimally verbal children on the place of AAC in their child’s home communication. Semi-structured family interviews were transcribed and subjected to Thematic Analysis. Formal AAC practices such as Picture Exchange Communication System (PECS) and Makaton were found to play a limited role in the children’s home communication. Findings indicate three possible explanations: the emotional and relationship-building dimensions of family communication; the competing priorities of family life with a disabled child; and the child’s existing multimodal communication strategies including the use of household objects. These findings offer a preliminary starting point for understanding the emic perspectives of AAC families and reasons for their convergence/divergence with professional attitudes to AAC, and warrant further investigation in larger-scale studies. 相似文献
20.
Katie Norburn Abigail Levin Sally Morgan Celia Harding 《British Journal of Special Education》2016,43(3):289-306
This study surveyed staff use of augmentative and alternative communication (AAC) within a large inner city special school for children with complex needs and learning disabilities. A questionnaire asked 72 staff members about the range of AAC strategies they typically used during the working day and how often they used it; training they had received about AAC; and which AAC approaches they found easy to use and those they found difficult. A range of AAC approaches were identified by staff. Participant confidence and understanding of the reasons for using identified AAC strategies was reported to be one of the key barriers to implementing AAC effectively. The implications in relation to how children with complex needs receive support for their receptive and expressive communication within an education environment are discussed. 相似文献