Synergism between chemical and physical fire-suppressant agents

A pronounced synergism is reported for mixtures of physical and chemical agents used in flame extinguishment. Mixtures containing approximately 90% (by volume) of either carbon dioxide or nitrogen and 10% of CF₃Br or CF₂ClBr are much more effective in suppressing fires (in cup-burner tests) than would be predicted by an additivity of effects. A method is proposed for delivering solutions of chemical agents dissolved in liquid CO₂ to obtain cooperative fire-suppression effects, while simultaneously reducing the danger to humans and the environment. A simple model has been developed to give very good predictions of the extinguishment concentrations of mixtures of physical and chemical agents.     

Determination of cup-burner extinguishing concentration using the perfectly stirred reactor model

A model based on the perfectly stirred reactor (PSR) concept is developed and utilized in the prediction of the minimum extinguishing concentration (MEC) of inert fire suppression agents established in the standard cup-burner test. Both physical and chemical mechanisms of fire suppression are considered in PSR modeling. Transport mechanisms are not modeled. Results are contrasted to experimental data and to a semi-analytical approach that assumes heat absorption by the agent is the primary extinguishing mechanism. Good agreement is achieved validating both the PSR approach and the conclusion that agent heat capacity has the first-order effect in the determination of the MEC. PSR results further capture a second-order chemical effect of oxygen depletion on the MEC. The PSR model is also used in a parametric assessment of the impact of test conditions on the MEC. Results show that cooling of the agent or heating of the fuel have a minor effect on the MEC. Variations on atmosphere conditions, such as temperature, pressure and humidity, have a more pronounced effect on the MEC. These results are interpreted in terms of the changing heat capacity of the inerting atmosphere and the altered chemical reactivity of the combustible mixture.     

A computational study of extinguishment and enhancement of propane cup-burner flames by halon and alternative agents

Computations of cup-burner flames in normal gravity have been performed using propane as the fuel to reveal the combustion inhibition and enhancement by the CF₃Br (halon 1301) and potential alternative fire-extinguishing agents (C₂HF₅, C₂HF₃Cl₂, and C₃H₂F₃Br). The time-dependent, two-dimensional numerical code used includes a detailed kinetic model (up to 241 species and 3918 reactions), diffusive transport, and a gray-gas radiation model. The peak reactivity spot (i.e., reaction kernel) at the flame base stabilizes a trailing flame, which is inclined inwardly by a buoyancy-induced entrainment flow. As the volume fraction of agent in the coflow increases gradually, the premixed-like reaction kernel weakens, thus inducing the flame base detachment from the burner rim and blowoff-type extinguishment eventually. The two-zone flame structure (with two heat-release-rate peaks) is formed in the trailing diffusion flame. The H₂O formed in the inner zone is converted further, primarily in the outer zone, to HF and CF₂O through exothermic reactions most significantly with the C₂HF₅ addition. The total heat release of the entire flame decreases (inhibiting) for CF₃Br but increases (enhancing) for the halon alternative agents, particularly C₂HF₅ and C₂HF₃Cl₂. Addition of C₂HF₅ results in unusual (non-chain branching) reactions.     

Locational disadvantage of the hub

We show how spatial evolution is different between the two representative models of economic geography: [Krugman 99:483–499, 1991] and [Ottaviano et al. 43:409–436, 2002]. We analyze the impacts of falling transport costs on the spatial distribution of economic activities and welfare for a network economy consisting of three regions located on a line. It is normally considered that a hub city, i.e., a central region, always has locational advantage and manufacturing workers gain from trade. This is true in the former model, but not in the latter when markets are opened up to trade. This is because the price competition is so keen in the central region that the manufacturing sector moves to the peripheral regions, which aggravates the social welfare. We then show that when goods are close substitutes and share of manufacturing is of an intermediate level, the manufacturing activities completely disappear from the central region leading to a full agglomeration in one peripheral region.

Incentive consistency and the choice of a spatial pricing mode

This paper extends Gronberg and Meyer’s results (1981 21:541–549) and studies the problem that occurs when transportation costs are different between a firm and consumers: The firm (based on a profit-maximizing consideration) may adopt discriminatory pricing with an inefficient transport mode. This inefficient pricing behavior may not be consistent with the social optimum, whereby the problem of incentive inconsistency thus occurs. When dealing with endogenous pricing modes having asymmetric transportation costs, one should pay more attention to the distortion caused by the inconsistency problem.

以有机酸钾盐为可燃剂的气溶胶灭火剂试验

用1 m3密闭试验箱进行灭火性能试验,采用半分法得出两种以有机酸钾盐为主要可燃剂的气溶胶灭火剂的配方,并对比其灭火时间。在热气溶胶灭火剂中添加碳酸钾作为热耗散剂,以降低反应速度,减小火焰外喷。用兰利法进行试验,得出了两种灭火剂的99%概率灭火效能,在70~75 g/m3之间。经测量,气溶胶灭火剂的燃烧产物是低毒的。气溶胶灭火剂在灭火时的不确定度很大,应以概率论的方法研究其灭火能力。     

Tax competition, spillovers, and subsidies

In the literature of local public finance, one of the well-known properties of optimal matching grant programs is that the matching grant rate should increase as the degree of benefit spillovers of public goods increases. This paper presents the reexamination of properties of optimal matching grant programs using the model of Bjorvatn and Schjelderup (Int Tax Public Financ 9:111–120, 2002). The result formally captures a property of matching grants that the optimal matching grant rate might decrease with the degree of spillover externalities.

Flame-extinguishing concentrations and peak concentrations of N2, Ar,CO2 and their mixtures for hydrocarbon fuels

Fire-extinguishing efficiency of inert gas mixtures was investigated by measuring flame-extinguishing concentrations and peak concentrations for hydrocarbon fuels, because new fire-extinguishing agents composed of inert gas mixtures have been developed as halon alternatives. The flame-extinguishing concentrations of nitrogen, argon, carbon dioxide and their mixtures for n-heptane were measured with the FRI glass cup burner. The peak concentrations of the agents for methane-air and propane-air mixtures were also measured with the tubular flame burner. Chemical equilibrium calculations showed that the adiabatic flame temperatures of the cup burner flames at the extinction condition were almost constant for all the agents. The adiabatic flame temperatures at the flammability limit of the tubular flame for each fuel were also independent of the inert gas agent if the mixtures had the same equivalence ratio. The flame-extinguishing concentrations of the inert gas mixtures were predicted by a simple equation averaging over the flame-extinguishing concentrations of all component gases weighted by mole fraction. The equation has the same form as Le Chatelier's law. For the flammability limits of the hydrocarbon-air mixtures, the same relation was also recognized in the effect of the mixed agents. The facts show clearly that this simple equation for the flame extinction concentrations is useful to estimate the fire suppression efficiency of any mixed agents of the inert gases. At the same time, it appears that the flame-extinguishing concentrations and the flammability limits reported in the paper are consistent.     

The building process as a tool towards an all-inclusive school. A Swedish example focusing on children with defined concentration difficulties such as ADHD, autism and Down’s syndrome

Professionals who take part in the building process have long been concerned with the same environmental factors, e.g. spatial layout, capacity, and function, as well as user demography. Through the knowledge gained on the ways environmental factors affect users of buildings, the need to understand how to handle these factors has grown, due to their influence on the building process. It will be shown how research on the influence of environmental factors found in the school environment can be applied to the building process. The purpose is to increase the accessibility to education through prolonged concentration ability among extra-sensitive children who have defined concentration difficulties such as Autism Spectrum Disorders (autism), Attention Deficit Hyperactivity Disorder (ADHD), and Down’s syndrome. This is a direct attempt to implement Swedish legislation (The Swedish Education Act, SFS 1985, p. 1100) regarding children’s accessibility to education, including the aims of the Swedish National Action Plan for Disability Policy (“From Patient to Citizen”, Swedish Government Bill 1999/2000, p. 79), which is based on the United Nations’ Universal Declaration of Human Rights (1948), where it is stated that all children should have equal access to education. The Swedish Work Environment Authority also declares that the work environment, in this case the school, should be adjusted to the physical and psychological needs of the users of the building (The Work Environment Act, AFS 2000, p. 42).

Experimental studies on the extinction of methane/air cup-burner flames with gas–solid composite particles

Fire suppression effectiveness of gas–solid composite particles consisting of 2-bromo-3,3,3-trifluoropropene (BTP) and zeolite 13X was evaluated on a cup-burner apparatus with coflowing methane/air flame. A series of composite samples with the weight concentration of BTP (ω) varying from 1.0 to 12.0% were tested. For comparison, extinction measurements were also conducted using neat BTP and zeolite 13X, respectively. Results indicated that the composite particles on a mass basis were much more effective than that of BTP and zeolite 13X used alone. A synergistic effect was exhibited by the BTP/zeolite 13X composites, which was affected by the ω values. Furthermore, significantly reduced HF concentrations (<70 ppm) were detected in the suppression tests with the composite particles, in comparison to that of neat BTP (1436 ppm). The composite particles extinguished the flame through a blowoff process, in which the flame base oscillated, detached from the cup-burner rim and extinguished eventually. Mechanism of the composite particles in suppressing the cup burner flame was studied.     

高分子水凝胶灭火剂扑救建筑火灾研究

为测试高分子水凝胶灭火剂扑救建筑火灾的灭火效果,以GB 17835-2008《水系灭火剂》中A类火灭火试验相关规定为参照,搭建木垛实验平台,模拟火灾荷载密度为2 395.008 MJ/m2（相当于一家服装店的火灾荷载）的建筑火灾,且在相同条件下,对比测试高分子水凝胶与水两种灭火剂的灭火效果,并利用车泵压、流量等相关关系计算得出高分子水凝胶灭火剂在建筑火灾扑救中的灭火强度。试验对比分析结果表明,高分子水凝胶灭火剂的灭火时间比水灭火剂的灭火时间短,其灭火效果优于水;同时依据相关计算得出高分子水凝胶灭火剂扑救建筑火灾的灭火强度约为0.059 L/（s.m2）。     

Examining the location factors of R&D labor in the regions of Greece

In this paper two models are developed in an attempt to elucidate the factors that influence the regional distribution of R&D labor across the regions of Greece. The first one is based on an adaptation of the [Guerrero and Seró (1997) Regional Studies 31:381–390] model to the Greek context treating the regional distribution of R&D labor as a function of the extent of agglomeration and the prevailing economic conditions. The second model extends the first one by taking into account two additional factors, viz. the production structure and infrastructure. The econometric results indicate the superior performance of the extended model in the context of Greece as well as attribute the location of R&D labor mainly on the diversification of industrial activity and the number of establishments in innovation-intensive sectors. It is therefore suggested that the stimulation of the regional production structure and infrastructure is essential for ‘knowledge-lagging’ regions.

A comparative study of the effects of chemical additives on the suppression efficiency of water mist

This paper reports the results of a comparative study of the effects of various salt additives on the flame extinguishing efficiency of fine water sprays. The relative suppression efficiencies are gauged by comparing the extinguishment time of a heptane flame. Preliminary tests are performed in a reduced scale cup-burner; major results are obtained using the closed reduced compartment set-up.The addition of NaCl, KCl or KHCO₃ resulted in large improvements of the suppression efficiency of the water mist. Potassium compounds show the greatest effect as 10% solution of KHCO₃ reduces the average extinction time by up to 96% compared to pure water. The other additives tested have a less noticeable effects, with aqueous solutions of MnCl₂, ZnCl₂ and CuCl₂ showing minimal improvement over water, whereas (NH₄)₂HPO₄, (NH₂)₂CO and FeSO₄·7H₂O actually increasing the time taken to extinguish the flame.     

Refugee integration and access to housing: a network management perspective

Studies of refugee integration in the UK have tended to focus either on integration as a concept or on the experiences of individuals or communities (cf. Ager and Strang, Indicators of integration: Final report, Home Office, London, 2004; Phillimore and Goodson in Urban Stud 43(10): 1715–1776, 2006). This article adopts a different, meso level of analysis, exploring the role of institutional networks in mediating integration. It draws on an evaluation and Ph.D. study of a project involving refugee community organisations in partnerships with housing providers and local authorities. This project adopted an implicit network management approach, with a funder/lead partner steering a set of local partnerships towards common outcomes—including empowerment of refugee organisations, changing policies and practices of larger partners—whilst at the same time improving access to housing and support services for refugees. The article establishes that network management was a theory in use and outlines concepts drawn from the network management literature to reflect on a comprehensive 3-year evaluation of the project. It draws evidence from a set of reflective interviews and a workshop for project partners held in the final stages of the evaluation, and from partnership interviews held as part of the Ph.D. study. It explores the cognitive and social dimensions of these networks, the types of steering used, power differences between actors and how network games played out. In conclusion it reflects on wider implications for the evaluation of networks, in particular the need to distinguish between a priori and emergent goals and between joint and multiple outcomes.

Inhibition of counterflow methane/air diffusion flame by water mist with varying mist diameter

In the present study, the effect of fine water mist on extinguishment of a methane–air counterflow diffusion flame was investigated to understand the underlying physics of fire extinguishment of highly stretched diffusion flame by water mist. Twin-fluid atomizers were used to generate polydisperse water mist of which Sauter mean diameters were 10, 20, 40, and 60 μm. When water mist is not added, the critical stretch rate at extinguishment is 439 s⁻¹ as compared to the theoretical value of 460 s⁻¹. For the case with water mist addition, when the stretch rate is small enough, almost all the water mist evaporates within the flame zone. On the other hand, for high stretch rate case, large mist droplets pass through the flame zone and can reach the stagnation plane. However, no oscillatory motion was found around the stagnation plane. Critical stretch rate at extinguishment decreases monotonously with the mass fraction of water mist independently of the mist diameter within the range of D₃₂ from 10 μm to 60 μm. On the other hand, with increase in the surface area parameter, the critical stretch rate at extinguishment decreases rapidly and becomes less sensitive at large surface area parameter, of which tendency is qualitatively in good agreement with theoretical predictions. For a constant surface area parameter, the critical stretch rate decreases with mist diameter because the mass fraction of water mist should increase in proportion to the mist diameter to keep the surface area parameter constant. When the water mist evaporates completely in the flame zone as in the present study, the mass fraction of the water mist is the dominant factor for fire extinguishment, rather than the surface area parameter. Therefore, an appropriate combination of stretch rate and water mist mass fraction should be provided to suppress effectively a given fire with a small amount of water mist.     

Chemical Composition of Overhaul Smoke After Use of Three Extinguishing Agents

The effect of extinguishing agents on the composition of smoke from wood fires of different intensities was studied. Three agents were examined: water, a protein-based water additive, and a sulfonate detergent-based compressed air foam (CAF). Air samples were analyzed for volatile organic compounds (USEPA 502 list), aldehydes, polyaromatic hydrocarbons, acid gasses, CO, CO₂, SO _x , and total volatile hydrocarbons. Air concentrations of levoglucosan and methoxyphenols, which are specific products from burning cellulose and lignin, respectively, were also measured. Levoglucosan, methoxyphenols, and many of the polyaromatic compounds have not been previously reported in overhaul smoke. A solitary test with water extinguishment was repeated for an assessment of variability. HCN and acid gases were not present in significant concentrations. The principal components that contributed appreciably to short-term occupational exposure hazards were formaldehyde, acrolein, benzene, polyaromatic hydrocarbons, and carbon monoxide. When a flocculation effect that cleared air particulate occurred during the use of the protein-based water additive, air concentrations of most chemicals in the air samples were reduced.     

含氟烯烃HFO-1336mzz(E)的协同灭火效应研究

基于燃烧杯实验获得的火焰高度、火焰温度及火焰形态等参数，探究了反式-1,1,1,4,4,4-六氟-2-丁烯（HFO-1336 mzz（E）,以下简称1336）与N2、六氟丙烷的协同灭火作用。在1336/N2的灭火过程中，1336体积分数小于15%时为正协同作用，最佳配比为5%∶95%。1336/六氟丙烷所有比例均为正协同作用，最佳配比为87%∶13%。六氟丙烷在一定程度上会增加火焰高度，并提高火焰温度，这是因为六氟丙烷的化学反应提供了额外的热量。     

Metal fire extinguishment

Four sets of experiments were conducted in order to find the most efficient extinguishing agent for use on fires of metal dusts such as aluminum and magnesium. Parameters considered included time before application of agent, ratio of applied agent to metal dust, time to extinguishment, and active versus inert chemical composition of agents. A 30% active, 70% inert mixture of zinc stearate and sand was found to be an effective and economical extinguishing agent for metal dust fires. Reference: T. P. Sharma, B. B. Lal, and J. Singh, Metal Fire Extinguishment,Fire Technology, Vol. 23, May 1987, pp.     

Analysis of Hold Time Models for Total Flooding Clean Extinguishing Agents

This study documents the experimental results of a research program designed to evaluate the validity of the widely published hold time prediction models found in NFPA 2001, Annex C and ISO 14520-1, Annex E. The models discussed in these standards obtain a measure of the equivalent leakage area, which, when coupled with ‘worst case’ assumptions, can be used to determine the minimum hold time. Three hold time prediction theories are adopted from these standards for validation; a wide descending interface model as implemented in ISO 14520-1 and two sharp descending interface models from the 2004 and 2008 publications of NFPA 2001. The experimental program is comprised of 15 tests conducted in a 103 m³ test enclosure. Three commercially available clean agents are selected to span a wide range of agent vapor densities including FK-5-1-12, HFC-125, and IG-541. A series of holes were drilled through enclosure boundaries at upper and lower elevations which were opened or closed as a means of regulating the amount of leakage area for any given test. Vertical profiles of agent concentration and ambient pressure are used to evaluate the agent concentration distribution, rates of agent draining, and the effective lower leakage fraction. A non-dimensional hold time is used to compare experimental results involving differing agent types and leakage areas. Results show that empirical values of the hold time are up to 50% longer than the theoretical hold time predictions when evaluated as the time to reduce the agent concentration to half its initial value. When evaluated as a 15% drop in concentration the model validity is significantly reduced. Under this condition, empirical hold time values are up to 50% shorter than the predictions of the sharp descending interface models and up to 100% longer than the wide descending interface model.

Berlin and Warsaw: in search of a new role in the European urban system

After 1989, the cities of Central and Eastern Europe were engaged in an inter-urban competition, a process characteristic of the urban scene since the beginning of European integration. Being a topic of great interest to researchers, a large body of literature has accumulated on the observed role of capital cities in the region as well as on their potential role in the future. Several researchers have focused on the position as well as the interdependence of Berlin and Warsaw—two urban nodes in what is hypothesized as a future West–East development trajectory (see Domański, 1999). The present paper deals with the emergence and development of metropolitan functions in these two cities. It is based on a comparative research project, which involved a series of structured, in-depth interviews with planners and policy-makers in Germany and Poland conducted by the author during the period 2001–2003. The paper discusses the development factors and their contributions to the metropolitan potential of Berlin and Warsaw. The identification of these factors is a starting point for determining the future position and rank of these two capital cities in the European urban system. The analysis is complemented by a comparison of trends in the employment structure of Berlin and Warsaw during the period 1994–2002. The results allow the author to evaluate some hypotheses posed in strategic planning documents concerning Berlin and Warsaw.