常压核供热——技术现实经济可行的清洁能源

为治理城市的燃煤污染和降低二氧化碳的排放量,我国需要开发大型清洁能源。核能是可供选择的清洁能源之一,核能不仅可以用于发电,而且可以替代燃煤为城市供热。在我国现在池式研究堆技术的基础上,设计出的常压供热反应堆,可以满足城市供热的需要,具有高度的安全性和可靠性,是一种技术现实和经济可行的解决方案。在我国发展城市集中供热的条件下,采用这种大型热源,将会以较大的规模来改善大气环境和降低温室气体的排放。     

Numerical simulation of an advanced energy storage system using H2O–LiBr as working fluid, Part 1: System design and modeling

The advanced energy storage technology proposed and patented by authors can be applied for cooling, heating, dehumidifying, combined cooling and heating, and so on. It is also called the variable mass energy transformation and storage (VMETS) technology in which the masses in one or two storage tanks change continuously during the energy charging and discharging processes. This paper presents an advanced energy storage system using aqueous lithium bromide (H₂O–LiBr) as working fluid. As one of VMETS systems, this system is a closed system using two storage tanks. It is used to shift electrical load and store energy for cooling, heating or combined cooling and heating. It is environmental friendly because the water is used as refrigerant in the system. Its working principle and process of energy transformation and storage are totally different from those of the traditional thermal energy storage (TES) systems. The electric energy in off-peak time is mostly transformed into the chemical potential of the working fluid and stored in the system firstly. And then the potential is transformed into cold or heat energy by absorption refrigeration or heat pump mode when the consumers need the cold or heat energy. The key to the system is to regulate the chemical potential by controlling the absorbent (LiBr) mass fraction or concentration in the working fluid with respect to time. As a result, by using a solution storage tank and a water storage tank, the energy transformation and storage can be carried out at the desirable time to shift electric load efficiently. Since the concentration of the working solution in the VMETS cycle varies continuously, the working process of the VMETS system is dynamic. As the first part of our study, the working principle and flow of the VMETS system were introduced first, and then the system dynamic models were developed. To investigate the system characteristics and performances under full-storage and partial-storage strategies, the numerical simulation will be performed in the subsequent paper. The simulation results will be very helpful for guiding the actual system and device design.     

Business community views

Three tasks must be included when considering the broad topic of urban security. The first is to define the term “critical infrastructure.” Second, security must be viewed from a systems perspective when looking at cities and the infrastructure that serves them. Third, careful scrutiny must be given to heretofore not-considered vulnerabilities that exist in every major city.In the hours and days immediately following the attacks on September 11, everything from foot bridges to tall buildings were considered to be critical infrastructure. But, clearly, not everything in such a broad definition can be defended. So then, what is today’s definition of critical infrastructure? One might be a new version of the “3 R’s”—resist, respond, recover. In those terms, “critical infrastructure” could be defined as: (a) systems whose rapid failure would lead to a catastrophic loss of life; (b) systems whose failure or significant degradation would lead to unacceptable economic consequences; (c) systems whose rapid failure would significantly impact rescue and response efforts; and (d) systems whose significant degradation severely impact recovery efforts.Resist? It would be impossible for a city to resist everything, everywhere. The ability to respond to some events would require efforts that are above and beyond the realistic capability of any city. That moves the scenario to recovery and rebuilding.     

The saving of energy when cooling milk and heating water on farms

The heat generated in the condenser of a refrigerated farm tank can be used for heating the water, needed for cleaning the milking equipment, to 60°C.Some experimental results (rise in water temperature, consumption of electricity), are discussed for one of the systems, in which a so-called boiler-condenser is used for the heating of water. If, in addition, a precooler is used, the total consumption of electricity for cooling and heating can be reduced by about 50%.It is expected in the Netherlands that in future 50% of milk will be produced on farms with 60 or more cows. At most of them the use of precoolers and heat pumps will be economically justified.     

Regional report Europe: “heat pumps — status and trends”

By 1997 about 90 million heat pumps have been installed worldwide, only less than 5% are located in Europe, historically the cradle of this “thermodynamic heating and cooling process”. The majority of the approximately 4 million installed heat pumps are imported reversible air-to-air systems in southern Europe and only 30% represent the typical European-made heating only electric driven compression systems for space and water heating in buildings in central and northern Europe. The first and second oil crises has been the main cause for a first European heat pump “boom” at the end of the seventies. Consequently the following drop in energy prices negatively influenced the market in some countries. The new renaissance in Europe in the middle of the nineties was initiated by the understanding of sustainable development for a more efficient energy use and the related protection of the environment.     

燃气发动机热泵及性能分析

介绍了燃气发动机热泵系统的构成及其工作原理，说明燃气发动机热泵的使用可减少空调／供热的用电量，缓解由空调／供热引起的电力紧张状况，降低电网的峰谷差，同时可调节燃气消耗量的季节不均衡性，并有利于环境保护。根据空调／供热系统的不同方式，给出了比较这些系统能源利用率的统一指标——次能源利用率，并利用一次能源利用率分析了六种供热系统的能源利用率，分析结果表明燃气发动机热泵的一次能源利用率最高，可节省能源。文章对燃气发动机热泵的性能进行了测试，一次能源利用率达到1．76。     

Ethics of family planning

The expression, “ethics of family planning,” it is argued, has no firm meaning, and should not be taken to imply that a full set of moral rules and principles governing family planning has been or is likely to be established. A survey is made of recent views on population and economic and social development, and it is argued that, although there is, indeed, no “universal problem” of population, the optimistic — as well as the pessimistic — view of this relationship is open to doubt. It is further argued that “ethics” cannot be imposed on subject matter of population from without: The very identification of a “problem” of population is evaluative from the start. A scheme of analysis to appraise the ethical status of measures to arrest or promote population growth is proposed, and a number of such measures are critically analyzed.     

Electricity generation: options for reduction in carbon emissions

Historically, the bulk production of electricity has been achieved by burning fossil fuels, with unavoidable gaseous emissions, including large quantities of carbon dioxide: an average-sized modern coal-burning power station is responsible for more than 10 Mt of CO(2) each year. This paper details typical emissions from present-day power stations and discusses the options for their reduction. Acknowledging that the cuts achieved in the past decade in the UK CO(2) emissions have been achieved largely by fuel switching, the remaining possibilities offered by this method are discussed. Switching to less-polluting fossil fuels will achieve some measure of reduction, but the basic problem of CO(2) emissions continues. Of the alternatives to fossil fuels, only nuclear power represents a zero-carbon large-scale energy source. Unfortunately, public concerns over safety and radioactive waste have still to be assuaged. Other approaches include the application of improved combustion technology, the removal of harmful gases from power-station flues and the use of waste heat to improve overall power-station efficiency. These all have a part to play, but many consider our best hope for emissions reduction to be the use of renewable energy. The main renewable energy contenders are assessed in this paper and realistic estimates of the contribution that each could provide are indicated. It appears that, in the time-scale envisaged by planners for reduction in CO(2) emission, in many countries renewable energy will be unlikely to deliver. At the same time, it is worth commenting that, again in many countries, the level of penetration of renewable energy will fall short of the present somewhat optimistic targets. Of renewable options, wind energy could be used in the short to medium term to cover for thermal plant closures, but for wind energy to be successful, the network will have to be modified to cope with wind's intermittent nature. Globally, hydroelectricity is currently the largest developed source of renewable electricity, but future large-scale projects will probably be limited to the less-developed world: the best schemes in the developed countries have already been exploited. Wave and tidal can be looked on as medium- to long-term generators of electricity, as their respective industries are not as mature as competing renewable resources. Municipal solid-waste combustion and landfill gas technologies can also be seen as short term, as can their rural equivalents, agriculture and forestry waste. Any widespread exploitation of renewable energy will depend on being able to transmit the energy from source to point of use, so the implications for the electrical network from the penetration of substantial levels of renewable energy are presented. Effective management of renewable energy installations will require technical assessment of the range of exploitation strategies, to compare local production of, say, hydrogen and the more traditional transmission of electricity. Such resources will have to compete with others in any national, or grid, system and detailed economic analysis will be necessary to determine the deployment that best fits the trading regime under which the energy will be sold. Consideration will also be necessary to determine how best to control the introduction of this radically new resource such that it does not attract punitive cost overheads until it is mature enough to cope. Finally, it is inescapable that nuclear power is a proven technology that could take its place in any future generation portfolio. Unfortunately, suspicion and mistrust surround waste management and radioactivity release. Unless this is overcome, the lack of confidence engendered by this public mistrust may result in few, if any, new nuclear power stations being built. In the event of that decision, it is difficult to see how CO(2) levels can be significantly reduced: the irony is that nuclear energy may emerge as environmentally essential.     

A conservation and rescue service?

The Concept May Now Constitute a Valid and Viable Response to Youth Unemployment, Soil Depletion, and the Impacts of Exogenous Disasters. It might, in several “advanced” countries, be implemented without costing governments or taxpayers a penny. The article discusses the intellectual and institutional history of the concept, and reviews the reasons for — and the considerable difficulties of — implementation. A new instrumentality to provide both jobs and training for the young will require political decisions at the highest level as well as a sweeping re-allocation of resources and a leadership cadre that is both astute and charismatic. Properly organized and led, the proposed Service could play a major role in re-interesting Third-World youth in the prospects offered by science and technology for a more prosperous and adventurous future, and thus contribute tangibly to the reduction of North-South tensions.     

“The ‘De-materialisation’ Myth” and the Limits to Growth: a Commentary on Dr. Trainer's Paper

Dr. Ted Trainer's paper in this issue contends that “de-materialisation” (decreasing energy and material inputs per unit of output) is a “myth” that must now be dropped from arguments against the “limits to growth” thesis. His specific arguments against de-materialisation are questioned in this commentary. This paper goes on to argue that even if de-materialisation has not taken place, it does not follow that near-term “zero growth” becomes necessary. On the contrary, the “limits to growth” position rests on erroneous Malthusian projections, and if the scarcity and spillover effects of growth are appropriately priced, conservation and substitution will be induced. Economic growth will facilitate technological and economic solutions to pollution and depletion. Institutional arrangements that will structure incentives, such as making better use of markets to set appropriate prices, are at the heart of the sustainability problem.     

Methodology for thermal design of novel combined refrigeration/power binary fluid systems

Refrigeration cogeneration systems which generate power alongside with cooling improve energy utilization significantly, because such systems offer a more reasonable arrangement of energy and exergy “flows” within the system, which results in lower fuel consumption as compared to the separate generation of power and cooling or heating. This paper proposes several novel systems of that type, based on ammonia–water working fluid. Importantly, general principles for integration of refrigeration and power systems to produce better energy and exergy efficiencies are summarized, based primarily on the reduction of exergy destruction. The proposed plants analyzed here operate in a fully-integrated combined cycle mode with ammonia–water Rankine cycle(s) and an ammonia refrigeration cycle, interconnected by absorption, separation and heat transfer processes. It was found that the cogeneration systems have good performance, with energy and exergy efficiencies of 28% and 55–60%, respectively, for the base-case studied (at maximum heat input temperature of 450 °C). That efficiency is, by itself, excellent for cogeneration cycles using heat sources at these temperatures, with the exergy efficiency comparable to that of nuclear power plants. When using exhaust heat from topping gas turbine power plants, the total plant energy efficiency can rise to the remarkable value of about 57%. The hardware proposed for use is conventional and commercially available; no hardware additional to that needed in conventional power and absorption cycles is needed.     

Evaluation of the mean ice ratio as a function of temperature in a heterogeneous food: Application to the determination of the target temperature at the end of freezing

The freezing process is widely used in the food industry. In the 70s, French regulation authorities have created in collaboration with the food industry the concept of «surgélation» process with the objective of improving the image of high quality frozen foods. The process of “surgélation” which could be translated as “super freezing” corresponds to a freezing process for which a final temperature of −18 °C must be reached “as fast as possible”. This concept was proposed in opposition to a conventionally “freezing” process for which no specific freezing rate is expected and the final storage temperature can be of −12 °C only. The objective of this work is to propose a methodology to evaluate the mean amount of frozen ice in a complex food as a function of temperature and to deduce a target temperature that must be considered as the temperature for which the food may be considered as “frozen”. Based on the definition proposed by the IIF-IIR red book, this target temperature has been defined as the temperature for which 80% of the freezable water is frozen. A case study is proposed with a model food made of two constituents.     

Agricultural research in flux : Experiments in university-industry ties

Dramatic advances in agricultural technology and management are changing the institutional structure of agricultural research in business, academia and government. A range of “experiments” aimed at improving the transfer of information from academia to industry are being run; some will work and some will not. Overall, these experiments are facilitating information exchange, and enhance—rather than pose a threat to—openness.     

Stripping efficiency and lifetime of carbon foils

Charge-exchange injection by means of carbon foils is a widely used method in accelerators. This paper discusses two critical issues concerning the use of carbon foils: efficiency and lifetime. An energy scaling of stripping efficiency was suggested and compared with measurements. Several factors that determine the foil lifetime—energy deposition, heating, stress and buckling—were studied by using the simulation codes MARS and ANSYS.     

Hydrogen trapping phenomena in carbon steel

Hydrogen trapping phenomena in carbon steel with different amounts of trapping sites were investigated by thermal analysis and permeation experiments. In thermal analysis, the relative amount of trapped hydrogen and the activation energy for evolution from various lattice defects were calculated by monitoring the pressure change caused by the release of hydrogen from hydrogen-charged specimens heated at a uniform rate. Hydrogen release peaks were observed at 116, 205 and 387° C, respectively, when the hydrogen-charged specimens with various defects were heated at a constant heating rate of 2.6° C min^–1. Analysis suggested that the peak at 116° C corresponded to release from ferrite-cementite interfaces and the peak at 205° C corresponded to release from dislocations. The activation energy for evolution of trapped hydrogen determined experimentally from the measured peak temperature at different heating rates was found to be 18.4 kJ mol^–1 in the ferrite-cementite interface. The hydrogen energy level around the trapping site was suggested from the trap activation energy and expected saddle-point energy. It was observed that most of the hydrogen is trapped in dislocations in spheroidized 0.49 wt% carbon steel.     

The observation of compliance change in the transition from hydrogen to air environment during the fatigue test

A compliance change was observed during fatigue testing of ASTM A710 HSLA steel using constant “K” CDCB specimen. The compliance decreased from 1.296 × 10⁻⁵ mm/N to 1.235× 10⁻⁵ mm/N when the environment was changed from hydrogen to air under the fatigue test conditions of f = 0.2 Hz, R = 0.1 and Δ K = 10 MPa✓m. The compliance change was observed in all fatigue testing while changing the environment from hydrogen to air. This compliance change can be explained numerically using the differential method for the design factors of the CDCB specimen. It was found from the calculation that the compliance change corresponded to a 6.3% change in Young’s modulus. It is proposed that the increased compliance resulted from the decreased Young’s modulus, the reduced Young’s modulus resulted from the increased lattice dilation which in turn resulted from a significantly increased hydrogen concentration at the crack tip region. The increased hydrogen concentration at the crack tip resulted from stress-induced hydrogen diffusion at the crack tip region.This work was conducted at Illinois institute of Technology (IIT).     

The CNPM thermal heat pump. Part 1 — general description and thermodynamic analysis

A research programme, funded by CNR (National Research Council), has been undertaken by CNPM since 1973. The aim of the programme is the construction and testing of a prototype thermal heat pump. The most significant component is an organic Rankine cycle engine, driving the compressor of a heat pump. Since the heat rejected by the engine is supplied to the user — water for domestic heating — the whole system performs as a ‘heat multiplier’, converting the high temperature heat given to the engine into a larger amount of low temperature heat, to be used for domestic heating.In this paper, the selection criteria for the working fluid — a completely fluoro-substituted hydrocarbon — and the main thermodynamic data of both power and heat pump cycles, are discussed; the finally adopted plant configuration is described, with particular emphasis on the influence exterted by the working fluid nature on the heat exchangers and turbo-machinery dimensions and performance. A discussion on the merits of the single fluid solution (ie the same working fluid in the power and the heat pump cycle) and dual fluid solution is also carried out. The feasibility of a low-temperature heat distribution, based on compact-surface, natural-draft convectors, with the relevant advantages on the Rankine and heat-pump cycles, is also investigated.Finally, the expected overal; system performance is given, both at design and part-load conditions. As a premium for the rather complex but efficient thermodynamicscv of the system, significant energy savings are obtained in all situations.     

Extended block diagram method for a multi-state system reliability assessment

The presented method extends the classical reliability block diagram method to a repairable multi-state system. It is very suitable for engineering applications since the procedure is well formalized and based on the natural decomposition of the entire multi-state system (the system is represented as a collection of its elements). Until now, the classical block diagram method did not provide the reliability assessment for the repairable multi-state system. The straightforward stochastic process methods are very difficult for engineering application in such cases due to the “dimension damnation”—huge number of system states. The suggested method is based on the combined random processes and the universal generating function technique and drastically reduces the number of states in the multi-state model.     

CHP planning for Newcastle upon Tyne

This article covers the development of a combined heat and power scheme, with an associated community heating network, in the centre of the city of Newcastle upon Tyne. The proposed scheme would comprise a gas-fired gas-turbine-driven electricity generator to provide electrical energy to a major hospital complex and the adjacent university. Waste heat from the gas turbine would be used to displace or supplement existing boiler plant in the hospital and university and also in those municipal buildings (including a second university) in the centre of the city connected to the community heating network. The technical and financial evaluation work carried out during the first phase of the project is described. The stages in the development process which would lead to the establishment of the necessary agreements with the heat and electricity consumers are discussed     

Economic possibilities and limitations of heat pumps with electric drive

The principles of the heat pump are analysed with special reference to the heating of homes and buildings, use being made of the concepts ‘Exergy’ and ‘Anergy’.Economic criteria are introduced to take account of capital and installation costs and the rates of amortization and interest to be applied to both heat pumps and conventional fuel systems. Also, the relative costs of fossil fuels and electricity are used, together with a mean coefficient of performance of the heat pump. A comparison is made not only between the two systems but also for composite systems in which the output of the heat pump is supplemented or replaced by direct heating (electrical resistance or fossil fuel) during winter peaks. The effect of the electricity tariff on the attractiveness of a heat pump system is examined, together with the potential advantage of heat storage systems.It is concluded that the most attractive application of heat pumps arises with district heating schemes due to the lower capital charges associated with large installations. In certain cases, however, the combination of a small heat pump designed to meet say 70% of winter demand, supplemented by burning stored fuel at times of peak demand, could be economic for individual installations, especially if the capital cost of the supplemental system could be reduced. The scope for improving the coefficient of performance of heat pumps is outlined.