Environment friendly alternatives to halogenated refrigerants—A review

In developing country like India, most of the vapor compression based refrigeration, air conditioning and heat pump systems continue to run on halogenated refrigerants due to its excellent thermodynamic and thermo-physical properties apart from the low cost. However, the halogenated refrigerants have adverse environmental impacts such as ozone depletion potential (ODP) and global warming potential (GWP). Hence, it is necessary to look for alternative refrigerants to full fill the objectives of the international protocols (Montreal and Kyoto) and to satisfy the growing worldwide demand. This paper reviews the various experimental and theoretical studies carried out around the globe with environment friendly alternatives such as hydrocarbons (HC), hydroflurocarbons (HFC) and their mixtures, which are going to be the promising long-term alternatives. In addition, the technical difficulties of mixed refrigerants and future challenges of the alternatives are discussed. The problems pertaining to the usage of environment friendly refrigerants are also analyzed.     

Development and Experimental Study of CO2 Expander in CO2 Supercritical Refrigeration Cycles

Abstract

As one of the natural working fluids for the refrigeration system, CO₂ has been attracting increasing attention over the last ten years. But CO₂ has to work at the supercritical region for the so-called “condensation” process regarding the conventional refrigerants and evaporate at the two-phase region, and therefore results in larger throttling loss for the practical refrigeration application. Consequently, new technologies must be developed to improve the performance efficiency of the CO₂ transcritical cycle, and make it to be equal or closer to that of the refrigeration system with the conventional refrigerants. In this study, an expander is employed in the CO₂ transcritical cycle to replace the throttling valve, and as a result the throttling loss can be decreased significantly. The paper presents the development of a rolling piston expander and the activity items in the expander design, including the seal technology, the contact friction control, the suction design, etc. The performance experiments for the expander are conducted in the present testing system for the CO₂ transcritical cycle. The results show that the recovery power of the expander is related to the revolution speed of the expander. The efficiency of the expander prototype is observed to be about 32%.     

含油污泥资源化利用技术研究

含油污泥是油田企业生产过程中的主要污染源之一,通过对含油污泥的组成及潜在能量的分析,研究了一种新型含油污泥处理剂,该剂能达到“一剂多效”,它既能迅速使含油污泥破乳、絮凝,使油包水中的水游离出来易于干燥,又能使脱去水后的泥渣彼此不粘连、不结块,还可使干燥后的泥渣易于燃烧且有较高的热值。该技术在充分利用其热能的基础上实现了含油污泥的无害化处理,在解决环境问题的同时又实现了废物的资源化利用。     

Comparison of refrigerated warehouse energy demand with R-717 and R-507 using eQUEST model

Natural refrigerant ammonia R-717 and synthetic azeotropic refrigerant R-507 (a blend containing 50% R-143a and 5% R-125 by weight) are used in a wide range of refrigeration systems especially in low-temperature applications. R-717 and R-507 are ozone friendly refrigerants, which have no Ozone Depletion Potential (ODP). Global Warming Potential (GWP) of R-717 and R-507 is equal to zero and 3300, respectively. The high amount of R-507 GWP demonstrates its negative effect on the Earth’s climate change. In this study, a refrigerated warehouse located in Cincinnati, Ohio was modeled and the total energy demand and Coefficient of Performance (COP) was evaluated by eQUEST using two scenarios. The R-717 and R-507 were used as refrigerant in the first and second scenarios, respectively. The results showed that using R-717 in the refrigeration system leads to a 15% energy saving and a higher COP compared to R-507 in all working conditions. The only exception is that at an evaporating temperature below ?35°C which COP values of both refrigerants are approximately equal.     

Recent developments of safer formulations of agrochemicals

The primary objectives of formulation technology are to optimise the biological activity of the pesticide, and to give a product which is safe and convenient for use. However, because of the wide variety of pesticide active ingredients which are available, many different types of formulations have been developed depending mainly on the physico-chemical properties of the active ingredients. In the past most formulations were based on simple solutions in water (SL), emulsifiable concentrates in a petroleum-based solvent (EC), or dusts (DP) and wettable powders (WP). The presence of petroleum-based solvents in EC formulations and dusty powders in DP and WP formulations can lead to safety hazards in use and a negative impact on the envirnoment generally. Most government and regulatory authorities are now demanding formulations which are cleaner and safer for the user, have minimal impact on the environment, and can be applied at the lowest dose rate. Developments in formulation technology and novel formulation types, sometimes in special packaging such as water-soluble packs, can also give products a competitive advantage, add value or extend the lif-cycle of active ingredients. There is also a demand from government authorities and consumer groups to use safer formulation additives and adjuvants, and to minimise the residues of pesticides on food crops after spraying. All of these aspects are putting increasing pressure on the development of improved formulation and adjuvant technologies. Pesticide formulations for spray application and for seed treatment are discussed, along with developments in bioenchancement.     

Pesticide Risk Indicators: Unidentified Inert Ingredients Compromise Their Integrity and Utility

Pesticide Risk Indicators (PRIs) are widely used to evaluate and compare the potential health and environmental risks of pesticide use and to guide pest control policies and practices. They are applied to agricultural, landscape and structural pest management by governmental agencies, private institutions and individuals. PRIs typically assess only the potential risks associated with the active ingredients because, with few exceptions, pesticide manufacturers disclose only the identity of the active ingredients which generally comprise only a minor portion of pesticide products. We show that when inert ingredients are identified and assessed by the same process as the active ingredient, the product specific risk can be much greater than that calculated for the active ingredient alone. To maintain transparency in risk assessment, all those who develop and apply PRIs or make decisions based on their output, should clearly disclose and discuss the limitations of the method.     

铁合金电炉烟尘的性质与低温固结研究

本文研究了硅铁电炉布袋除尘收集的烟尘性能，烟尘低温固结球团的性能和工艺方法。研究结果表明，硅铁电炉烟尘中ＳｉＯ２ 约占９０ － ９５ ％ ，其它组分含量较低，有利于进行回收利用。烟尘密度小、粒度细、表面活性差、成球性能差。采用添加粘结剂进行自然养护和低温固结处理，均能获得强度较好的固结球团，能够加入铁合金炉回收利用。     

A Successful Pilot Project of Decentralized Household Waste Management in Brazil

Summary Present municipal waste management paradigms in Brazil do not allow for flexible approaches to solving an extremely dynamic problem. This paper discusses the basic flaws in present thinking models of residents and municipal administrators. Fundamental arguments presented on municipal solid waste relate to nomenclature, destinations, definitions, logistics, social dynamics, social assistance programs, education and employment philosophies. In each case, the consequences of the stalemate are explained in terms of the unsustainable situation of constantly growing landfills. In sequence, a proactive thinking model is presented and explained that has the potential of drastically reducing landfill size. It is called Municipal Transit Material Processing. The model has been tested successfully in small communities and is now available for scale-up. The landfill diversion achieved stands at 62% of household waste in comparison with 15% theoretically possible in Brazil with selective collection models. Although of necessity the arguments apply directly to Brazil, the basic ideas behind the reasoning may be extrapolated to other Southern countries. The following simple example will illustrate to the reader the type of paradigm inversion the paper proposes to convey. The classical political slogan in Brazil is “get children out of garbage dumps”. The inversion proposed and explained is “do away with garbage dumps”.     

Investigation of Environmental Effects Based on Exergetic Irreversibility for Display Cases’ Units in Commercial Cooling

This study examines energetic and exergetic performances of display cases’ units used in market applications depending on different refrigerants. Besides CO₂ emission potential of each refrigerant based on exergetic irreversibility obtained from analyses is calculated by the method of Total Equivalent Warming Impact (TEWI). In this study, 1 kW cooling capacity and vapor compression cooling cycle is taken as reference and refrigerants of R-22, R-134a, R-404A, and R-507 together with alternative refrigerant R-407C and R152a are examined separately. According to analyses, R-404A gas, used widely in market applications, has low performance with average COP 3.89 and average exergy efficiency 55.20%. R-152a gas has the best performance by the thermodynamics parameters including COP 4.49, exergy efficiency 63.79%, and 0.23 kW power consumption and emission parameter 14097.490 ton CO₂/year. Although COP is used as a criterion to evaluate the systems, this study finally emphasizes the importance of exergy analysis and TEWI method which are important methods to determine irreversibility and emission potential of the systems.     

针对大型振动试验辅助支撑系统的结构设计与技术改进

对振动台辅助支撑系统进行了结构改进,增加了空气弹簧和导向轴。并且针对偏心问题,采用多个气源对不同位置分布的空气弹簧施加不同的气压进一步增强振动台的抗倾覆能力。建立了一套可以应用于轨道交通等大型设备的具有较大承载能力(14 t),较大抗倾覆能力的振动台辅助支撑系统。     

MULTIPLE CRITERIA SCREENING OF A LARGE WATER POLICY SUBSET SELECTION PROBLEM1

ABSTRACT: A new screening approach is applied to a large‐scale multiple criteria water management problem to remove actions that cannot possibly be in the best subset. An inherent advantage of the approach is its ability to identify inferior actions by examining them individually, rather than within subsets. In a case study involving the selection of actions to address high water levels in the Great Lakes‐St. Lawrence Basin, two statistical indicators, the mode and the mean, are used to aggregate the opinions of experts and representatives of interest groups on the impacts of actions according to various criteria. Application of the screening approach shows that some of the proposed actions can be removed as they can never be in the optimal subset, thereby reducing the size of the problem.     

LONGITUDINAL DISPERSION IN RWERS: A DEAD-ZONE MODEL SOLUTION

ABSTRACT: The longitudinal dispersion of tracer material in rivers is simulated by a dead-zone model that involves two coupled differential equations. For an instantaneous injection of tracer material, the problem is solved by the Laplace. Transform and numerical inversion to obtain the time-concentration curve at any sampling station. The optimal values of the model parameters are estimated from field measurements. Applications of the model to three different rivers generally show that the model reproduces the longitudinal dispersion characteristics in natural streams with sufficient accuracy.     

Floodplain management: Land acquisition versus preservation of historic buildings in Cambridge,Ontario, Canada

Non-structural adjustments in floodplain management are often avoided because they are seen to infringe on personal rights, adversely affect property values and restrict local tax bases. Land acquisition programs in urban areas encounter a further problem when they lead to demolition of buildings and other structures considered to have historical or architectural value. An experience in Cambridge, Ontario demonstrates that the potential conflict between flood damage reduction and historical preservation objectives can be exacerbated as a result of uncoordinated planning efforts, inflexibility in interpreting mandates, unclear roles for participating agencies, and lack of cooperation Many of these dilemmas can be resolved through consultation and discussion early in the planning process as well as through a willingness to be flexible and to search for a compromise     

Effects of deodorants on treatment of boat holding-tank waste

A literature search and survey of Virginia, USA, campgrounds with RV pump-out stations were used to determine whether boat holding-tank deodorant chemicals would have deleterious effects on marina septic systems or package treatment plants. Laboratory studies reported in the literature indicate that these chemical additives could affect septic system function in three ways: (1) active ingredients in the additives can impair sewage degradation in septic tanks, causing sludge buildup and overflow of solids into the drainfield, (2) additive chemicals might enter the drainfield and, in high enough concentrations, reduce the drainfield's ability to degrade waste, or (3) toxic additive chemicals might migrate from the drainfield to ground or surface water. Laboratory studies also show that some ingredients added to holding tanks interfere with functioning of activated sludge treatment process. Experience in the field and in other laboratory studies suggests that factors such as dilution of treated waste with untreated waste and the characteristics of the sewage to be treated can reduce the possibility of damage to septic and activated sludge systems. The campground owners surveyed indicated that they have few problems with their septic systems in spite of the presence of chemical additives in the RV waste. However, most of them practice good septic system maintenance and have devised other means of ensuring that their systems function efficiently. In addition, the survey indicates that most Virginia campgrounds get only seasonal use (as would marinas in Virginia), allowing their systems to recover between peak seasons.     

Back-alley sustainability and the role of environmental education

Environmental education can be a catalyst for sustainable development in local communities as long as it is recognised that communities have different challenges and needs. From a perspective of social change and sustainable development, environmental education can be broadly defined as the process that enables students and teachers to participate in the planning, implementation, and evaluation of educational activities aimed at resolving an environmental issue that they themselves have identified. What an 'environmental issue' is, then, depends on the perceptions and earlier experiences of the learner as well as the context in which education takes place. An illustration of such a participatory approach to environmental education is provided by the case of Pistons Middle School in Detroit, Michigan where teachers, students and outside facilitators combined action research and community problem solving.     

Investigation on working fluids selection for organic rankine cycles with low-temperature heat sources

The Influence of mixed and pure working fluids on the performance of organic Rankine cycles (ORCs) is discussed. Specifically, the performance of mixed and pure working fluids is analyzed based on certain characteristics of low-temperature heat source and heat sink. A method of selecting binary zeotropic mixed working fluids that match with different heat sinks is introduced. Thermodynamic processes of ORCs for various heat sources are simulated in Matlab. The performance characteristics of pure and mixed working fluids are compared under different inlet temperatures and temperature gradients of sensible heat sources. The results demonstrate that when the initial temperature of a heat source is lower and its temperature gradient is higher, and the temperature gradient of the heat sink is higher, mixed working fluids have better performance than pure working fluids. However, for the opposite heat source and heat sink situations, pure working fluids perform better. Mixtures with low critical temperature components exhibit the best performance among all working fluids when the temperature gradient of the heat source is large. The analysis also shows that introduction of a recuperator may reduce the cycle efficiency when the heat source temperature is low and the temperature gradient of the heat source is large.     

河流污染带特征参数预测模型及其软件化研究

本文建立了连续点源和瞬时点源两种常见排污工况下河流污染带的特征参数预测模型，模型预测的污染带特征参数包括污染物达到全断面均匀混合的距离、污染带最大长度、最大宽度及其出现的位置、污染带面积等，并能利用污染带的特征参数反演推算允许排污量和削减量。模型所用方法简便易行，且具有较高精度，可用于常规连续排污和突发事故排污情况下的河流污染带预测。在此基础上，研制开发了河流污染带特征参数预测系统（RPZS），方便实用。     

Petroleum exploitation and contract terms in developing countries after the oil price collapse

In resource taxation the critical fiscal requirement is a scheme which performs the twin functions of ensuring that projects which are viable on a pre-tax basis remain so post-tax, and that the host government obtains a reasonable share of the economic rent. Royalty, income tax, production-sharing and the resource rent tax are examined in the light of their efficiency at meeting these two criteria. The resource rent tax is probably the most appropriate fiscal instrument because this tax permits a threshold rate of return to be earned before the tax becomes payable. One drawback is that during the early years of a project the host government may receive little or no revenue. An advance resource rent tax can be used to eliminate this shortcoming. A further problem is the disincentive to exploration which can be produced.     

塑料和橡胶类废弃物的热物理特性及焚烧特性的研究

塑料和橡胶类的废弃物是城市垃圾的重要组成。本文在新式焚烧炉中对它们的焚烧特性、污染特性进行了研究。这将有助于进一步优化新型转式焚烧炉，完善低染、低腐蚀、低粘结的废弃物的焚烧工艺。     

A geophysical perspective of value of information: examples of spatial decisions for groundwater sustainability

The value of information (VOI) can be used to determine what kind of spatial information maybe relevant and useful for groundwater sustainability decisions. In this paper, the unique challenges for applying VoI to spatial information from geophysical data are described. The uncertainty regarding the spatial structure or continuity of the subsurface properties can be described with geostatistical sample models. Using these models, one can quantify the prior value given our present state of uncertainty and a set of decision alternatives and outcomes. Because geophysical techniques are a type of remote-sensing data, assuming “perfect” information is not realistic since the techniques usually are indirectly sampling the aquifer properties. Therefore, the focus of this paper is describing how the data reliability (the measure of imperfectness) can be quantified. One of the foremost considerations is the non-unique relationship between geological parameters (which determine groundwater flow) and geophysical observables (what determines the response of the technique). Another is to have the information in a form such that it is useful for spatial decisions. This will often require inversion and interpretation of the geophysical data. Inversion reconstructs an image of the subsurface from the raw geophysical data. How closely the image reproduces the true subsurface structure or property of interest depends on the particular technique’s resolution, depth of investigation and sensor locations. Lastly, in some cases, interpretation of the geophysical data or inversion will be necessary to link the data to the variables that determine the outcome of the decision. Three examples are provided that illustrate different approaches and methods for addressing these challenges. In the examples, time-domain electromagnetic and electrical resistivity techniques are evaluated for their ability to assist in spatial decisions for aquifer management. The examples considered address these three situations: aquifer vulnerability to surface–borne contaminants, managed aquifer recharge and CO₂/brine leakage (related to CO₂ geologic sequestration activities). The methods presented here are transferable to other subsurface sciences and decisions that involve risk. Recent work has been applied to geothermal well-siting using electromagnetic techniques. These approaches can also be applied for oil and mining spatial decisions, and they offer advantages over previous VOI work done for oil applications: they explicitly include the geologic uncertainty modeling and simulate the physics of the considered geophysical technique.