Yang Zhou

Bio: Yang Zhou is an academic researcher from University of Science and Technology of China. The author has contributed to research in topics: Flame spread & Heat transfer. The author has an hindex of 10, co-authored 12 publications receiving 303 citations. Previous affiliations of Yang Zhou include Central South University.

Pyrolytic behavior of waste extruded polystyrene and rigid polyurethane by multi kinetics methods and Py-GC/MS

Abstract: The utilization of polymer wastes for volatile fuel production has been considered as a sustainable and environmental-friendly approach for achieving better waste management, pollution protection, and renewable energy security. Polymer pyrolysis, as an ideal method for polymer waste converted into storable fuel, was explored thoroughly in this study from pyrolysis kinetics to evolved gas analysis. Two typical building-used polymer wastes, extruded polystyrene (XPS) and rigid polyurethane (RPU), were selected to conduct a series of thermogravimetry (TG) experiments. Then commonly-used isoconversional methods were employed to calculate the kinetic parameters of the pyrolysis during the whole conversion. Kinetic models of XPS and RPU thermal degradations were identified from nineteen reaction models by Coats-Redfern and masterplots methods. Then accommodation function was employed to adjust the theoretical model for reconstruction. Considering the complexities of RPU component and degradation process, Py-GC/MS was used to identify the volatile product component at 250, 340, and 460 °C, respectively. Results showed that there are large parts of volatile alcohols and ethers escaped during RPU pyrolysis process. The results of this study have implications concerning kinetic triplet determination method and escaped gas analysis during polymer waste pyrolysis process.

Correlation study between flammability and the width of organic thermal insulation materials for building exterior walls

Abstract: Considering the sustainable energy strategy for buildings, external wall insulation system is expected to play an important role in building energy conversation. And higher energy efficiency drives our demands for much thicker thermal insulation materials. However, it does not mean that the thicker the better, especially considering various requirements and properties. Among these are materials mechanical strength, aging durability, water resistance, construction difficulty and even fire safety performance. In the following paper to explore fire safety of organic thermal insulation, polyurethane foam (PUF) and extruded polystyrene (XPS) were selected to carry out a series of lab-scale tests over a wide range of widths. What is more, some fire safety aspects have been studied and compared: temperature variation in solid and gas phase, heat and mass transfer process, flame propagation over material surface, flame height, material melting and charring, etc. The aim of exploring relationship between material flammability and width is to help to select a proper width when considering fire safety, and lay a foundation for us to conduct real fire disaster of external insulation system in following study.

Theoretical and experimental study of width effects on horizontal flame spread over extruded and expanded polystyrene foam surfaces

Abstract: In order to explore the mechanisms of horizontal flame spread over thermal insulation foam surfaces, extruded polystyrene and expanded polystyrene foams were selected to carry out a series of experiments with different sample widths ranging from 4 to 16 cm. Temperatures in both the solid phase and the gas phase were measured, with considerable differences being found between extruded polystyrene and expanded polystyrene in their temperature profiles. Extruded polystyrene also showed a distinct pyrolysis stage, while expanded polystyrene showed a lengthy melting stage differences that may be explained from their different thermal properties. The flame spread rates of both materials first decreased and then increased with increasing sample widths. The minimum flame spread rates were at widths of 8 and 10 cm for extruded polystyrene and expanded polystyrene, respectively, resulting from the relative differences between convection and radiation heat flux, which were different for the two foams. Numerical equa...

Orientation effect on upward flame propagation over rigid polyurethane foam

Abstract: Inclined upward (concurrent) flame spread over rigid polyurethane (RPU) foam which can exhibit great fire hazard in real high-rise building fire disasters has attracted more and more attentions in the previous studies. In this work, a series of bench-scale experiments and theoretical analyses were conducted to explore the orientation effect on upward flame spread of RPU foam with sample inclination ranging from 10° to 85°. Results show that the fitted correlations between flame length and pyrolysis length are different due to the increasing inclinations, and can be categorized by a modified Rayleigh number. Meanwhile, the power exponents of the fitted expressions between flame length and heat release rate per unit width can also be classified: the power exponent n = 1, n 1, when 10° ≤ θ ≤ 40°, 50° ≤ θ ≤ 70°, and θ ≥ 80°, respectively. Furthermore, the dimensionless mass loss rate is approximately proportional to the quarter power of the modified Rayleigh number. The relationship between upward flame spread rate and sine of inclined angle is approximately exponential, and a critical modified Rayleigh number at which no flame spread can be sustained is proposed. The results of this study can provide a reference to high-rise building fire risk assessment and energy conservation system design.

Experimental study on the width and pressure effect on the horizontal flame spread of insulation material

Abstract: Organic insulation materials such as polyurethane foams are widely used as buildings' facade wall insulation materials in China. However, they are highly flammable and of great fire hazard by the chemical nature. In this paper, a series of laboratory scale experiments using rigid polyurethane foam were conducted and theoretical analysis was applied to evaluate the real fire performance of such materials under different situations. Temperature profiles in both solid and gas phases were obtained. This work provides basic correlations of flame spread characteristic of polyurethane foams regarding to width and pressure changes. Theoretical analysis on heat transfer of width and pressure effects was also provided. Good agreement of changing trends was found between experimental results and theoretical calculation.

Polyurethane Foams: Past, Present, and Future

Abstract: Polymeric foams can be found virtually everywhere due to their advantageous properties compared with counterparts materials. Possibly the most important class of polymeric foams are polyurethane foams (PUFs), as their low density and thermal conductivity combined with their interesting mechanical properties make them excellent thermal and sound insulators, as well as structural and comfort materials. Despite the broad range of applications, the production of PUFs is still highly petroleum-dependent, so this industry must adapt to ever more strict regulations and rigorous consumers. In that sense, the well-established raw materials and process technologies can face a turning point in the near future, due to the need of using renewable raw materials and new process technologies, such as three-dimensional (3D) printing. In this work, the fundamental aspects of the production of PUFs are reviewed, the new challenges that the PUFs industry are expected to confront regarding process methodologies in the near future are outlined, and some alternatives are also presented. Then, the strategies for the improvement of PUFs sustainability, including recycling, and the enhancement of their properties are discussed.

Traditional, state-of-the-art and renewable thermal building insulation materials: An overview

Abstract: Energy saving has become a strategic goal in the whole world, that will lead to protect the environment and conserve natural resources. The energy consumption in buildings for heating and cooling is considered as one of the major sources of energy consumption in a lot of countries. Therefore, there is an ongoing search for finding the proper alternatives to preserve energy and minimize energy losses. Subsequently, heat insulators, part of building materials, are steadily getting their importance as a means of saving energy. Although, a lot of insulation materials are used commercially, this part of building construction still faces different difficulties and challenges such as the cost, thermal and mechanical properties, health problems, etc. Current insulation materials used in construction industry are generally polymer based materials such as polystyrene and polyurethane foam. Although these materials have a high performance in thermal insulation, but the environmental impacts in their production processes are significant. Consequently, the researchers find that there is a necessity to develop and come up with insulating materials that possess excellent properties and at the same time, they have less environmental impacts, and are relatively cheap. In this review paper, the researches carried out in the formulation and development of different kinds of thermal insulation in the last decades are presented. The focus was placed on researches utilized of renewable resources and wastes in thermal insulations development. In addition, the light was shed on the composites materials which was developed as a construction material with high thermal insulation capacity.

The accuracy and efficiency of GA and PSO optimization schemes on estimating reaction kinetic parameters of biomass pyrolysis

Abstract: Reaction kinetic parameters estimation of biomass pyrolysis is a relatively difficult optimization problem due to the complexity of pyrolysis model. Two common heuristic algorithms, Genetic Algorithm (GA) and Particle Swarm Optimization (PSO), are applied to estimate the kinetic parameters of three-component parallel reaction mechanism based on the thermogravimetric experiment in wide heating rates. The accuracy and efficiency of GA and PSO algorithms are compared with each other under the identical optimization conditions. The results indicate the better optimization abilities of PSO with the closer convergence solution to the global optimum and quicker convergence to the solution than GA based on the three-component parallel reaction mechanism of biomass pyrolysis. Especially, the improvement of best fitting value of PSO reaches up to 30% compared with that of GA. Furthermore, 14 estimated kinetic parameters of best fitting value are obtained and the mass loss rate predicted results including three separate components (hemicellulose, cellulose and lignin) are compared with experimental data.

Pyrolytic kinetics, reaction mechanisms and products of waste tea via TG-FTIR and Py-GC/MS

Abstract: The present study experimentally quantified the pyrolysis behaviors of waste tea (WT) as a function of four heating rates using thermogravimetric-Fourier transform infrared spectrometry and pyrolysis-gas chromatography-mass spectrometry analyses. The maximum weight loss of WT (66.79%) occurred at the main stage of devolatilization between 187.0 and 536.5 °C. The average activation energy estimates of three sub-stages of devolatilization were slightly higher (161.81, 193.19 and 224.99 kJ/mol, respectively) by the Flynn-Wall-Ozawa than Kissinger-Akahira-Sunose method. Kinetic reaction mechanisms predicted using the master-plots were f (α) = (3/2)(1 − α)2/3[1 − (1 − α)1/3]−1, f (α) = (1 − α)2, and f (α) = (1 − α)2.5 for the three sub-stages, respectively. The prominent volatiles of the WT pyrolysis were CO2 > C O > phenol > CH4 > C O > NH3 > H2O > CO. A total of 33 organic compounds were identified including alkene, acid, benzene, furan, ketone, phenol, nitride, alcohol, aldehyde, alkyl, and ester. This study provides a theoretical and practical guideline to meeting the engineering challenges of introducing WT residues in the bioenergy sector.

Eco-friendly geopolymer materials: A review of performance improvement, potential application and sustainability assessment

Abstract: The traditional cement production wastes a large amount of natural resources and energy, and causes environmental pollution, which cannot meet the green and sustainable development needs of modern building materials. Geopolymer is an environmentally friendly materials that can utilize industrial solid wastes and have low environmental load and energy consumption, which is expected to become a substitute for OPC. However, geopolymers also have shortcomings in some properties that need to be improved. This paper reviews the recent research progress on the performance improvement, potential new applicationw and sustainability assessment of geopolymer materials. Discussion from this paper showed that the properties of geopolymer materials, including rheology, hardening properties, toughness, etc., can be significantly improved by some methods such as chemical additives, mineral admixtures, nanoparticles, fibers, etc. Furthermore, this paper proves that geopolymers have great application potential as porous thermal insulation materials and 3D printing building materials, and points out some performance optimization methods for geopolymer-based porous materials and 3D printing materials. In this work, it was also concluded that geopolymer shows significant advantages over OPC in sustainable analysis index such as E-energy and E-CO2 (Energy and CO2 emission) based on LCA method. Finally, a few potential opportunities and development directions have been suggested for future research on geopolymer materials.