Polymer Heat Exchangers—History,Opportunities, and Challenges

For the past 40 years considerable attention has been devoted to the innovation, characterization, and implementation of polymer heat exchanger technology, driven by the corrosion resistance, low density, low cost, and ease of manufacture of many polymeric materials. Moreover, new polymer composites, with higher impact and yield strengths, higher temperature limits, and higher thermal conductivities, promise to bridge the performance gap that exists between polymers and corrosion-resistant metals. This paper begins by reviewing the history of polymer heat exchangers and the technical limitations that have motivated much of the research on this technology. The notable developments that have taken place in the last decade and primary potential applications for polymer heat exchangers are then discussed, including solar water heaters, heat recovery systems, and seawater heat exchangers, in particular, for the desalination industry. The paper closes with a review of compact polymer heat exchangers, with millimeter-sized passages, and thoughts on future applications of this most promising technology.     

Lead oxide technology—Past,present, and future

In the earliest lead/acid battery, active material was formed electrochemically on the surface of a sheet of lead, which also served as the plate itself. Since that time, lead compounds (i.e., litharge, red lead, leady oxide) have been used to form the active mass, with better efficiency and performance. Many lead oxide production methods have existed, the predominant two are the `ball mill' and the `Barton pot' processes. These, and other methods, produce oxides with characteristics which are unique to each. The oxide properties of particle size and shape, surface area, crystal structure, purity, and degree of oxidation, can potentially, individually or in combinations affect the battery. With today's manufacturers making mixed product lines that range from deep cycle to automotive lead acid to valve-regulated lead/acid (VRLA) batteries and everything in between, lead oxidation machinery and processes must be able to respond accordingly to produce materials that meet appropriate specifications. Oxide equipment and operating technique is improving in response to those characteristics that the ongoing research by industry indicates are or will, in the future, be beneficial to overall battery performance.     

Weak Tangency, Weak Invariance, and Carathéodory Mappings

New results on weak invariance in Hilbert spaces, both in autonomous and nonautonomous case, are given. Applications to weakly decreasing systems and to strong invariance are presented.     

Sondhauss and Rijke oscillations—thermodynamic analysis,possible applications and analogies

The phenomena of acoustical pressure oscillations generated in a gas by a steady heat source may be separated into two distinct types: (i) Sondhauss oscillations which occur in a pipe having one end closed and one open; (ii) Rijke oscillations which occur in a pipe with both ends open. After reviewing representative literature, actual and possible applications are described. Analogies and differences among these and similar systems are considered from a thermodynamic point of view.     

Iterated Integrals, Gelfand—Leray Residue, and First Return Mapping

Recently, one of the authors gave an algorithm for calculating the first nonzero Poincaré-Pontryagin function of a small polynomial perturbation of a polynomial Hamiltonian, under a generic hypothesis. We generalize this algorithm and show that any Poincaré-Pontryagin function of order l, denoted by M _l, can be written as a sum of an iterated integral of length at most l and of a combination of all previous Poincaré-Pontryagin functions, M ₁, M ₂, …, M _l-1, and their derivatives. This extends some results obtained recently and allows to identify the Bautin ideal with the ideal generated by iterated integrals. 2000 Mathematics Subject Classification. 34C35, 34D30.     

Climate change,nuclear power,and the adaptation–mitigation dilemma

Many policy-makers view nuclear power as a mitigation for climate change. Efforts to mitigate and adapt to climate change, however, interact with existing and new nuclear power plants, and these installations must contend with dilemmas between adaptation and mitigation. This paper develops five criteria to assess the adaptation–mitigation dilemma on two major points: (1) the ability of nuclear power to adapt to climate change and (2) the potential for nuclear power operation to hinder climate change adaptation. Sea level rise models for nine coastal sites in the United States, a review of US Nuclear Regulatory Commission documents, and reports from France’s nuclear regulatory agency provided insights into issues that have arisen from sea level rise, shoreline erosion, coastal storms, floods, and heat waves. Applying the criteria to inland and coastal nuclear power plants reveals several weaknesses. Safety stands out as the primary concern at coastal locations, while inland locations encounter greater problems with interrupted operation. Adapting nuclear power to climate change entails either increased expenses for construction and operation or incurs significant costs to the environment and public health and welfare. Mere absence of greenhouse gas emissions is not sufficient to assess nuclear power as a mitigation for climate change.     

Comparison of the renewable transportation fuels,liquid hydrogen and methanol,with gasoline—Energetic and economic aspects

In this paper, the renewable energy vectors liquid hydrogen (LH₂) and methanol generated from atmospheric CO₂ are compared with the conventional crude oil-gasoline system. Both renewable concepts, liquid hydrogen and methanol, lead to a drastic CO₂ reduction compared to the fossil-based system. The comparison between the LH₂ and methanol vector for the transport sector shows nearly the same fuel cost and energy efficiency but strong infrastructure advantages for methanol.     

Heat pipes—concepts,materials and applications

The heat pipe is an innovative engineering structure characterized by its capacity to transfer large quantities of heat through relatively small cross-sectional areas with very small temperature differences; it also possesses high thermal conductance and low thermal impedance. In recent times, heat pipes in various forms and designs have found a wide variety of applications. This paper briefly presents the basic concepts of heat pipes, recent innovations in design and their applications.     

A comparative study of catalytic behaviors of Mn,Fe, Co,Ni, Cu and Zn–Based catalysts in steam reforming of methanol,acetic acid and acetone

This study investigated the distinct catalytic behaviors of mono Mn, Fe, Co, Ni, Cu and Zn catalysts in the reforming of the small organics including methanol, acetic acid and acetone. The results showed that Mn, Fe or Zn-based catalysts showed almost no activity for steam reforming of either methanol, acetic acid or acetone, due to their low capacity to break the chemical bonds of the organics or to activate steam. Co and Cu-based catalysts were generally active for steam reforming of methanol. Nevertheless, Co-based catalysts promoted methanol decomposition to form a substantial amount of CO. Alumina as a support remarkably influenced catalytic stability of the catalyst. The unsupported Cu catalyst showed a much lower stability than Cu/Al₂O₃. Nevertheless, the unsupported Ni was more stable than Ni/Al₂O₃ catalyst, due to its high resistivity towards coking. The unsupported Co, however, was prone to coking. The C/H ratios in the coke formed over the unsupported and alumina-supported Ni or Co catalysts were distinct, indicating the involvement of alumina in the coking process. In addition, Ni and Co catalysts behaved differently. Ni/Al₂O₃ showed a superior stability than Co/Al₂O₃ in steam reforming of acetone. The coke formed on Ni/Al₂O₃ was more aromatic than that over Co/Al₂O₃ catalysts while morphologies of coke (nanotubes over Ni/Al₂O₃ versus fibrous coke over Co/Al₂O₃) were also different.     

The Effect of Ductile-Lithic Sand Grains,Overpressure and Secondary Dissolution on Porosity and Permeability and Their Relevance to Hydrocarbon Exploration in Aşkale Sub-Basin,East Anatolia,Turkey

Ductile lithic grain, secondary porosity, temperature, and overpressure control porosity and permeability in the Mio-Pliocene and Upper Oligocene sandstones of the A?kale sub-basin in East Anatolia. Ductile lithic grains account for between approximately 60–90% of the original sand grain population. There is a pronounced loss of porosity with increasing bruial depth in this sub-basin. At depths of less than 3000 m, this is due solely to ductile-lithic grain compaction where the rate of porosity loss of with depth increases with increasing ductile-lithic grain content. But at depths greater than 3000 m, the steep porosity increases with depth due to secondary solution activities and overpressure in the A?kale sub-basin in East Anatolia. Secondary porosity is a common diagenetic feature in the more deeply buried (> 3000 m) sediments in the A?kale sub-basin. The secondary porosity arises principally from dissolution of feldspar, to a lesser extent, of the quartz (approximately 10–30%). Overpressure is due to tectonic stress. Reservoir quality is thus controlled by secondary solution activities, overpressure, temperature (geothermal gradient) and depth of burial in the A?kale sub-basin in East Anatolia Basin.     

Solar-driven steam-based gasification of sugarcane bagasse in a combined drop-tube and fixed-bed reactor – Thermodynamic,kinetic, and experimental analyses

Syngas production via steam-based thermochemical gasification of Brazilian sugarcane bagasse, using concentrated solar energy for process heat, was thermodynamically and experimentally investigated. Energy and exergy analyses revealed the potential benefits of solar-driven over conventional autothermal gasification that included superior quality of syngas composition and higher yield per unit of feedstock. Reaction rates for the gasification of fast pyrolyzed bagasse char were measured by thermogravimetric analysis and a rate law based on the oxygen exchange mechanism was formulated. In order to provide residence times long enough for adequate char conversion, a laboratory-scale entrained flow reactor that combines drop-tube and fixed-bed concepts was developed. Testing was performed in an electric furnace with the final aim to supply heat by concentrated solar radiation. Experimental runs at reactor temperatures of 1073–1573 K and a biomass feed rate of 0.48 g/min yielded high-quality syngas of molar ratios H₂/CO = 1.6 and CO₂/CO = 0.31, and with heating values of 15.3–16.9 MJ/kg, resulting in an upgrade factor (ratio of heating value of syngas produced over that of the feedstock) of 112%. Theoretical upgrade factors of up to 126%, along with the treatment of wet feedstock and elimination of the air separation unit, support the potential benefits of solar-driven over autothermal gasification.     

How can the integration of renewable energy and power-to-gas benefit industrial facilities? From techno-economic,policy, and environmental assessment

This paper applies a mixed integer linear programming model developed in GAMS to simulate the integration of Power-to-Gas infrastructure into an industrial manufacturer's energy system subject to the existing thermal and electrical energy demands, as well as a third hydrogen energy profile. This work is novel in that it assesses the challenges and economic incentives available to make feasible the installation of a hydrogen-based energy storage systems within the Province of Ontario from a techno-economic, policy and environmental perspectives.The energy hub analyzed in this work uses electricity from the power grid and solar PVs to meet the manufacturer's demands, while converting the excess to hydrogen gas, which is used across an array of pathways to generate revenue. ThisThis includes a blend ofof hydrogen for fuel cell vehicles (FCVs), hydrogen for forklifts, and the direct injection of hydrogen into the facility's natural gas, adding renewable content to the heating, and manufacturing processes. Our primary objective was to implement a safe design that minimizes capital and operating costs, resulting in a favorable business case for producing hydrogen, and providing ancillary grid services. However, Power-to-Gas creates a net-emission reduction that can be used not only to sell emission allowances in the provincial carboncarbon tax program for up to $30/t-CO_2eq but to assist the Company in achieving their strategic emission reduction targets.Installation of the selected Power-to-Gas system would require a total capital investment of $2,620,448 with the electrolyzers and solar panels accounting for 41% and 17% of the capital costs, respectively. The compressors will account for most of the operating costs which total $237,653 annually. Within the energy hub, 76,073 kg-H₂ has been produced per year for end-use applications. A sensitivity analysis was performed by varying both hydrogen and carbon credit price which predicted a potentialpotential CO₂ offset of 2359.7 tonne/yr with a payback period of as little as 2.8 years.