Average Heat Release Research Articles

Experimental investigation on storage-type heat pump system for efficient supply in cold region

Application of air source heat pump systems in cold region is severely limited by the low-temperature inadaptability. Utilizing latent heat storage to store condensation heat of heat pump during the day for nighttime heating maybe a potential solution. But continuous heat supply in both charging and discharging process hasn’t been completely achieved, which is also crucial for cold region. To fill this research gap, this paper proposes storage-type heat pump system using waste heat of subcooler for heat supply in the charging process. Besides, discontinuous heat storage and release are carried out to further verify the adaptability of the system. Experimental results demonstrate that heat from subcooler reaches 16.79 kW·h and the average heat release power of condensation thermal accumulator is 5.24 kW, and the output heat of subcooler can meet the daytime heating demand of a 100 m2 room. In this case, condensation heat utilization efficiency could reach 89.1 % and the average COP of system is 3.65. Also effective heating can be supplied within 48 h after heat storage. The results validate the feasibility of cogeneration of the subcooler and condensation thermal accumulator for continuous heat supply, which provides a guidance for its application at extremely low temperature.

Unsaturated polyester resin modified with a novel reactive flame retardant: effects on thermal stability and flammability

Abstract A new reactive flame retardant (DTA), containing phosphaphenanthrene and triazine-trione groups was synthesized and applied to improve the flame retardancy of unsaturated polyester resin. The thermal stability, flame retardancy and combustion behaviors of UP/DTA thermosets were detected by thermogravimeric analysis (TG), limited oxygen index (LOI), vertical burning (UL94) test and cone calorimeter test. According to the research results, the addition of DTA contributed to improving the flame retardancy of UP. After adding 20 wt% DTA, the LOI of UP composite increased from 19.0% of the neat UP to 26.6%, and UL94 rating reached V-0. In addition, compared with pure UP, the peak heat release rate (pk-HRR), average heat release rate (av-HRR) and total heat release rate (THR) of UP/DTA-20 thermosetting material decreased by 44.0, 26.2 and 29.5%, respectively. In the gaseous phase, DTA decomposed to generate nitrogen-containing fragments with diluting effect and phosphorus-containing free radicals with quenching effect to inhibit the combustion. In the condensed phase, phosphaphenanthrene group of DTA decomposed to generate phosphorus-based compounds, which promoted the carbonization of the UP matrix and cooperated with triazine-trione group to increase the char yield. Therefore, DTA plays an important role in flame retardancy in the gas and condensed phases.

Crack-Resistant Amino Resin Flame-Retardant Coatings Using Waterborne Polyurethane as a Co-Binder Resin.

Surface cracking is a major issue in amino resin-based flame-retardant coatings, which can be reduced by mixing flexible resins into the coatings. In this study, flexible waterborne polyurethane (WPU) was added into a melamine-modified, urea-formaldehyde, resin-based intumescent flame retardant (MUF-IFR) coating. A molecular chain of WPU was inserted into the MUF network and formed a WPU/MUF-semi-IPN structure. The cracking resistance of the coating was gradually enhanced with the increase in WPU content. When the WPU content exceeded 25% of the total resin, there were no cracks in the coatings after crack-resistance tests. The coatings before and after toughening showed good transparency on wood surfaces. The influence of WPU on char formation and flame retardant properties were explored by TGA, SEM, and cone calorimetry. The results showed that the decomposition of WPU occurred before char formation, which decreased the integrity of the coating and damaged the compactness of the char. Therefore, the addition of WPU reduced the expansion height and the barrier capacity of the char as well as the flame retardant properties of the coating. When the amount of WPU was 25% of the total resin, compared to the non-WPU coating, the average heat release rate in 300 s (AveHRR300s) and the total heat release at 300 s (THR300s) of the samples were increased by 45.8% and 35.7%, respectively. However, compared to the naked wood, the peak heat release rate (pHRR1), AveHRR300s, and THR300s of the samples with the coating containing 25% WPU were decreased by 64.2%, 39.0%, and 39.7%, respectively. Therefore, the thermal stability of WPU affected char formation. The amount of WPU added should be chosen to be the amount that was added just before the coating cracked.

Impact of wind speed on urban heat and pollution islands

Large urban areas are typically subjected to excessive levels of heat and pollution. The formation of an urban-scale plume would arise from releasing heat in a stable atmosphere. The presence of wind may disrupt the pattern of the plume. This study explores the effect of wind intensity and ambient stability on the plume structure and pollution dispersion numerically. A metropolitan has been selected as the urban, and the average heat and pollution release rate is calculated based on a typical megacity. It has been found that for buoyancy ratios (the ratio between the horizontal velocity of the urban plume to wind speed) smaller than 0.5, the wind is the governing mechanism. For buoyancy ratio higher than 2, the urban heat island is governing mechanism. In stable conditions and the ratios smaller than 0.5, the urban average temperature difference reduces by about 0.125 K for a unit increase in wind speed. When the ratios are less than 0.2, there are 0.5 K temperature differences between urban and rural, and 0.072 μg/m3 averaged pollution for all stability conditions. It is also found that for ratios higher than 0.5, any increase in wind velocity does not reduce the pollution concentration significantly. For values smaller than 0.5, any increase in wind speed would result in a considerable drop in pollution concentration if the radiative effect of pollutants is ignored.

Effect of borax-boric acid and ammonium polyphosphate on flame retardancy of natural fiber polyethylene composites

Wood fiber filled high density polyethylene composites (WPCs) were prepared using twin screw extruder and maleated polyethylene as a coupling agent. Bamboo fibers were initially treated with alkali (NaOH), boric acid - borax (Ba-Bx) and borax (Bx). The treated and untreated fibers were used in combination with ammonium polyphosphate (APP) to investigate their synergistic effects on thermal stability, flame retardancy and mechanical properties. Alkali pretreatment (5 % NaOH) of fibers showed significant improvement in performance of APP by increasing thermal stability in WPCs. The derivative thermogravimetric (DTG) results indicate significance of Ba-Bx in promoting char induction at lower temperatures (340 ºC) and thereby, improved the thermal stability in WPCs. Flammability decreased with addition of flame retardant additives. As compared to pure WPCs, composites containing APP 10 % / Ba-Bx 5 % exhibited maximum reduction in average heat release rate (HRR) by 69 %, peak heat release rate (PHRR) by 59 %, total heat released rate (THR) by 48 % and also increased time to ignition (TTI) by 62 %. However, no significant difference was found among the combinations i.e., APP with or without compounds towards reducing the flammability of WPCs. The strength properties also reduced significantly when boron compounds were added along with APP. In general, APP alone (15 %) is enough for imparting thermal stability and flame retardancy in WPCs.

Impact of compression ratio on combustion, performance and exhaust emissions of diesel engine fueled with Undi methyl ester-diesel and Undi ethyl ester-diesel blends

The current study emphasizes on the influence of nonedible, easily accessible Undi ester blended diesel in single-cylinder, four-stroke, naturally aspirated, direct-injection variable compression ratio diesel engine. All tests were accomplished by varying volumetric proportions of Undi methyl ester (UME) and Undi ethyl ester by 10%, 20%, 30%, 40%, and 50% and compression ratio (CR) from 16:1–20:1. The Undi esters consolidation to diesel, especially enhances brake thermal efficiency (BTE) and decreases brake specific energy consumption (BSEC) of the engine. In comparison with Diesel, ester fuel blends produce lower unburnt hydrocarbons (UHC), carbon monoxide (CO), and particulate matter (PM) emissions with the cost of higher oxides of nitrogen (NOX). With the increase in compression ratio from 16 to 20. All Undi ethyl ester diesel blends have on an average of 1.44% slightly improved brake thermal efficiency, 1.41% lower brake specific fuel consumption and it emits comparatively on an average 7.90% lesser carbon monoxide, 7.21% lower unburnt hydrocarbon, 0.59% lower particulate matter and 1.94% higher oxides of nitrogen emission than UME diesel blends with an increment in CR from 16 to 20. In addition, ester blends showed higher maximum In-cylinder pressure and heat release rate than commercial diesel. Undi ethyl ester blends show 0.82%, 1.08% on an average higher maximum In-cylinder pressure and heat release rate than UME Diesel blends when CR increased from 16 to 20. Undi ester Diesel blends are found to be utmost substitute to commercial diesel fuel in all features such as combustion, performance and emissions characteristics.

Experimental analysis on combustion characteristics of diesel and kerosene under different radiation intensity of heat source

With the help of cone calorimeter, combustion experiments of 0# diesel and kerosene (3# jet fuel) under external heat radiation were completed, and the main combustion performance parameters, such as heat release rate, specific mass loss rate, effective heat of combustion, time to ignition, combustion duration and fire spread risk, were obtained under different heat source radiation intensities. The change rules of the main combustion characteristics of these tow fuels with the increase of heat source radiation intensity were discussed, and the differences of the main combustion characteristics between the diesel and kerosene were compared and analyzed. The results show that the average heat release rate, peak heat release rate and specific weight loss rate of the diesel and kerosene increase linearly with the increase of heat source radiation intensity, and the increasing trend (slope) of kerosene is larger than that of diesel. The time to reach the peak heat release rate, ignition time and combustion duration of the both fuels decreased exponentially with the increase of heat source radiation intensity. Under the same radiation intensity, the heat release rate, specific mass loss rate and effective heat combustion of kerosene are higher than those of diesel, while the time to reach the peak heat release rate, ignition time and combustion duration of kerosene are lower than those of diesel. The total heat release of kerosene is higher than that of diesel under different heat source radiation intensities, and the average total heat release of kerosene is about 6.17% higher than that of diesel. THR/tlast and pkHRR/TTI of the two fuels showed an exponential relationship, and the fire spread risk of diesel was less than that of kerosene.

Burning Characteristics of Ancient Wood from Traditional Buildings in Shanxi Province, China

Due to long-term natural degradation, the surface morphology of traditional building wood differs significantly from that of modern wood. It is more combustible than modern wood and its combustion characteristics are important evaluation indicators for fire simulation and fire protection of traditional buildings. In this paper, ancient wood from six traditional buildings were tested by a surface morphology fractal method and conical calorimeter. Additionally, their combustion properties such as ignition time, heat release rate, total heat release and charring time were analyzed to determine the combustion behavior of ancient wood and their differences with modern wood. The results showed that the ignition time of the specimens was significantly influenced by the surface morphological features. The higher the fractal dimension grade of the morphological features, the shorter the ignition time. The ignition time of Ulm wood with fractal dimension class 3 was 15 s, while that of Ulm wood with fractal dimension class 1 was 23 s. Under the same fractal dimension class, the total heat release per unit time of ancient softwood was higher than that of ancient hardwood. The average heat release rates of Larch wood and Ulm wood were 66.21 kw·m−2, 72.07 kw·m−2 and 57.26 kw·m−2, 67.30 kw·m−2. The basic charring rate of ancient wood of the same species was mostly higher than that of modern wood by more than 6%, with the basic charring rate of ancient Larch wood being 0.8559 mm/min, which was 15.66% higher than that of modern Larch wood, 22.27% higher than that recommended in the European EC5 standard, and 6.87% higher than that calculated in the American AFPA. The results of the study are important guidelines for fire risk assessment and fire protection of traditional buildings.

Critical condition and transient evolution of methane detonation extinction by fine water droplet curtains

Two-dimensional numerical simulations with Eulerian–Lagrangian method and reduced chemical reaction model are conducted to study the methane detonation propagation across a water curtain with finite thickness. The critical length of the water curtain with sprayed droplets is determined through parametric simulations with different water mass loadings and droplet sizes. The influence of water curtain length on the methane detonation is examined by the trajectories of peak pressure and time history of average heat release rate. The results indicate that the water curtain not only inhibit the incident detonation wave, but also prevent the detonation re-ignition after the incident wave is quenched. Moreover, unsteady response of gaseous methane detonation to water curtain are analyzed. The detonation re-initiation process behind the water curtain near the critical loading is also captured. In addition, mechanism of detonation inhibition with fine water droplets are discussed. It is found that energy and momentum exchanges start immediately when the detonation wave enters the water curtain area, but the mass transfer starts well behind the detonation wave due to the finitely long droplet heating duration. It is shown that the convective heat transfer by water droplets plays a significant role in quenching a detonation.

A green COPD flame retardant for improving poly(l-lactic acid)

A green flame retardant COPD is synthesized by using chitosan oligosacc- haride (COS), p-hydroxybenzaldehyde and 9,10-dihydro-9-oxa-10-phospho-10-oxide (DOPO) as raw materials according to two-step reaction. The synthesized product is confirmed with FTIR, UV and NMR. When the COPD is inserted into poly(l-lactic acid) (PLLA) via solution blending, the flame retardation of PLLA is improved. As the blend ratio of COPD/PLLA is 20/80, the limit oxygen index (LOI) and UL-94 vertical burning grade 25% and V-1, respectively. The heat release rate (HRR), total heat release (THR), and average effective heat release (av-EHR) decrease in conical calorimetry. The composite also exhibits good carbon forming capacity. The flame retardation mainly originates from cooperation of condensation phase with gas phase process. Since the poor miscibility limit the dispersibility of COPD in PLLA matrix, the flame resistance and mechanical performance of composite are to compromised. The flame retardation for PLLA is anticipated due to green raw material is used and alternative process such as melt blending and adding compatibility can be adopted.

INVESTIGATION THE FIRE HAZARD OF PLYWOODS USING A CONE CALORIMETER

A high-efficiency fire retardant composition was prepared with dicyandiamide, phosphoric acid, boric acid, borax, urea and magnesium sulfate and it was used to process veneers which were then to prepare the plywood. Meanwhile, heat release and smoke release from combustion of plywood were tested by a cone calorimeter, including heat release rate, mass loss rate, CO yield, CO2 yield and oxygen consumption. Results showed that the plywood with this fire retardant treatment had the better flame-retardant performance and smoke suppression effect as well as the stronger char-forming capability compared to plywood without fire retardant treatment. The average heat release rate, total heat release, average effective heat of combustion, total smoke release, CO yield and oxygen consumption of the plywood with fire retardant treatment were decreased by 63.72%, 91.94%, 53.70%, 76.81%, 84.99% and 91.86%, respectively. Moreover, the fire growth index of plywood treated by fire retardant was relatively low (3.454 kW·m-2·s-1) and it took longer time to reach the peak heat release rate, accompanied with slow fire spreading. The fire performance index was relatively high (0.136 s·m2·kW-1) and it took longer time to be ignited, thus leaving a long time for escaping at fire accidents. The fire hazard of plywood with fire retardant treatment was low, and its safety level was high.

Modified hemp fiber combined with melamine cyanurate for enhancing fire safety and mechanical properties of unsaturated polyester resins for automobile parts

The application of flame retardants in automobiles is extensive, and the existing flame retardants will cause some pollution to the environment. Therefore, environmentally friendly flame retardants need wide exploration. Natural fibers have been used in various fields for their environmentally friendly features. Thus, in this paper, hemp fiber (HF) was modified with phytic acid and then combined with melamine cyanurate to improve the fire safety of unsaturated polyester resins (UPRs). The fire behavior and thermal stability of UPR composites were evaluated using the limiting oxygen index (LOI), cone calorimeter test, and thermo-gravimetric analysis (TGA). With 3 wt. % modified HF (HF-P) incorporation, the LOI value of UPR/HF-P-3 composites increased from 18.9% of pure UPR to 22.1%, and the average heat release rate (AHRR) and total heat release were reduced to 401.9 kW/m2 and 150.6 MJ/m2, respectively. TGA revealed that UPR/HF-P-3 composites led to the increased amount of residual char and better thermal stability compared to UPR/HF composites. In addition, HF-P endowed a better enhancement on the flexural strength of UPR composites.

Co-based metal-organic framework with phosphonate and triazole structures for enhancing fire retardancy of epoxy resin

A phosphonate and triazole containing binary carboxylic acid ligand was synthesized via azide-alkyne “click” reaction, which was further coordinated with cobalt nodes to form metal-organic framework (MOF) containing two important fire retardant elements, phosphorus and nitrogen (PN-MOF). With the loading of 6 wt% PN-MOF in epoxy resin (EP), the peak heat release rate, average heat release rate, total heat release, and total smoke production of EP/PN-MOF composites dramatically decreased by 44.6%, 52.9%, 44.0% and 36.2%, respectively. Meanwhile, the limiting oxygen index increased from 24.3% to 29.8%. Thanks to the excellent catalytic activity of PN-MOF in carbonation and oxidation, the release of toxic gasses from the composites was significantly reduced, particularly, the production of CO was decreased by 48% in comparison with neat EP. In addition, the glass transition temperature and modulus of EP/PN-MOF composites were increased, suggesting a strong interfacial interaction between PN-MOF and EP matrix. Overall, this research provides an efficient strategy for the preparation of MOF-type flame retardant to simultaneously enhance the flame retardancy and physical properties of polymeric materials.

Performance investigation on an air source heat pump system with latent heat thermal energy storage

This paper proposes an air source heat pump (ASHP) system integrated with a latent heat thermal energy storage (LTES) unit based on a specially-designed heat exchanger, condensing heat storage unit, to further improve system performance in cold region. The innovation of this device is that heat is transferred directly between refrigerant and phase change material (PCM), which significantly reduces heat loss. Experimental investigation on thermal performance of the system is carried out. Besides, a mathematical model of condensing heat storage unit is developed to investigate charging/discharging characteristics and validated by experimental data. Experimental results show that heat storage capacity reaches 31.83 kWh and average heat release power is 4.73 kW. Simulation results indicate that both smaller fin pitch and larger fin thickness accelerate the melting rate of PCM, but variations of tube diameter show little impact on it. In order to maintain heat release power, circulating water flow rate should be increased with discharging time. Three-stage PCM improves both energy and exergy performance compared to single-stage PCM. COP improvement could reach 4.01% and overall exergy efficiency is increased by 4.65%. Therefore, ASHP system combined with LTES unit is a potential approach to expand its application under extremely low temperature.

Numerical simulation of two-dimensional detonation propagation in partially pre-vaporized n-heptane sprays

In this paper, two dimensional detonation propagation in partially prevaporized n-heptane sprays is studied by using Eulerian/Lagrangian methods. The effects of droplet preevaporation on the detonation propagation are investigated. The general features and detailed structures of two-phase detonations are well captured with the present numerical methods. The results show that the detonation propagation speed and detonation structures are significantly affected by the preevaporated gas equivalence ratio. The numerical soot foils are used to characterize the influence of preevaporated gas equivalence ratio on the detonation propagation. Regular detonation cellular structures are observed for large preevaporated gas equivalence ratios, but when decreasing the preevaporated gas equivalence ratio, the detonation cellular structures become much more unstable and the average cell width also increases. It is also found that the preevaporated gas equivalence ratio has little effects on the volume averaged heat release when the detonation propagates stably. Moreover, the results also suggest that the detonation can propagate in the two-phase heptane and air mixture without preevaporation, but the detonation would be first quenched and then re-ignited when the preevaporated gas equivalence ratio is small or equal to zero.

Fabrication of Anisotropic Polyphosphazene/Bio-based Poly(urethane-acrylate) composite foams with High Thermal Insulation and Flame Retardancy

Developing renewable porous materials with low thermal conductivity and high flame retardancy is of great significance in energy saving and fire safety. Herein, a series of bio-based anisotropic composite foams were fabricated from oil-in-water (o/w) high internal phase Pickering emulsions (Pickering HIPEs) stabilized by both bio-based poly (urethane-acrylate) (PUA) and poly (cyclotriphosphazene-co-4,4ʹ-sulfonyldiphenol) (PZS) particles. All Pickering HIPEs have good stability originated from the two kinds of particles irreversible adsorption at the oil-water interface and the formation of a “3D networks” of PUA particles aggregates in the aqueous phase. The microstructures and rheology of the double-particles stabilized HIPEs were adjusted by changing the contents of particles and the internal phase volume fractions. Then the anisotropic PZS/PUA composite foams with high porosity (up to 93.9%) and low thermal conductivity (down to 48.4 mW m−1∙K−1) were prepared by unidirectional freeze-drying these Pickering HIPEs. The anisotropic structure enhanced the mechanical strength in axial direction and thermal insulation property in radial direction. Compared with the PUA foam, loading only PZS of 10.7 wt%, the values of average heat release rate, total heat release and average effective heat of combustion of the composite foams were reduced by 19.3%, 12.8%, and 40.2%, respectively. Meanwhile, the value of limiting oxygen index was also increased from 16.3% to 18.2%, which was resulted from PZS functioned in the condensed phases during the combustion process. This work provides a strategy to prepare a kind of bio-based anisotropic foams which would find uses in the fields of fire safety and thermal insulation.

Comparing the ignition and burning hazards of sugar‐cane bagasse and hemp epoxy composites

SummaryThe feasibility of using sugar‐cane bagasse as a reinforcement for natural fiber composites and the performance of these composites under fire conditions was investigated. Plies were manufactured using a process, which involved alkali‐treating bagasse, blending, pressing, and drying. Soaking durations of 30 minutes and 24 hours were compared. Composites were then made with these plies using a light resin transfer molding process. The composites were characterized and compared to a commercial hemp fabric using thermogravimetric analysis for thermal stability and char yield, isotropic hot disc method for thermal conductivity and specific heat capacity, and cone calorimeter for flammability. The investigation found that bagasse plies could be successfully used in composite manufacture, but posed a greater ignition hazard, and a comparable burning behavior hazard to the commercial product when tested at a radiant heat flux of 35 kW/m2. Thirty minutes treating resulted in a ply, which resulted in a char yield of 28%. Although in the composite form, there were no significant differences between all sample groups. With regards to ignition, the hemp composite had the latest time‐to‐ignition of 137 seconds. Comparison of the thermal properties to the ignition times showed that higher values of thermal properties resulted in later ignition times. The composite with the 30‐minute treated bagasse had a total heat release of 159 MJ/m2 and average heat release rate of 263 kW/m2, while the peak heat release rate was lower for the 24‐hour treated bagasse at 537 kW/m2. Overall, no significant differences in the two treatment durations were observed.

High thermal stability and low flammability for Ethylene‐Vinyl acetate Monomer/Ethylene‐Propylene‐Diene Monomer by incorporating macromolecular charring agent

The intumescent flame retardant (IFR) compounded with triazine charcoal‐forming agent (CFA) and ammonium polyphosphate (APP) was applied to the flame‐retardant modification of EVM/EPDM. The effect of APP‐CFA on the flame‐retardant performance of the composite was studied. The results showed that APP‐CFA effectively enhanced the flame‐retardant performance of EVM/EPDM. Compared with the control sample, when the APP–CFA ratio was 4:1, the limit oxygen index of EVM/EPDM with APP–CFA was up to 27.1%, which was increased by about 40%, and the average heat release rate was 110.1 kW/m2, which was reduced by about 29%. Moreover, it passed the UL‐94 V‐0 test. TGA results showed that after the addition of APP/CFA, the amount of residue significantly increased. SEM test showed that the char layer formed by the composite containing APP/CFA during combustion was denser and more uniform. In addition, compared with the traditional intumescent flame‐retardant ammonium polyphosphate–dipentaerythritol–melamine (APP‐DPER‐MN), the new flame‐retardant APP–CFA has better flame‐retardant and comprehensive performances.

Study of Burning Behaviors and Fire Risk of Flame Retardant Plywood by Cone Calorimeter and TG Test

A flame retardant composition was prepared by using phosphoguanidine, guanidine sulfamate, disodium octaborate tetrahydrate and dodecyl dimethyl benzyl ammonium chloride. Veneers were immersed in such flame retardant mixture to prepare plywood. The combustion characteristics and thermal stability of plywood were assessed using a cone calorimeter and TG. Results showed that: (1) High concentration and loading of flame retardant were beneficial for the fire resistance of the plywood. (2) The limiting oxygen index (LOI) and residual mass of plywood processed using the flame retardant was increased by 87.52% and 58.66% compared to those of the untreated plywood, while the average heat release rate (av-HRR), total heat release (THR), effective heat of combustion (EHC), total smoke release (TSR), CO yield (COY), CO2 yield (CO2Y) and oxygen consumption were decreased by 44.3%, 82.9%, 47.0%, 86.0%, 89.9%, 50.1% and 83.1%, respectively. (3) Treated plywood which had a low fire growth index (FGI) displayed a later combustion heat release rate peak and slower flame spread than observed for the untreated material. Combustion of treated plywood displayed a higher fire performance index (FPI), indicating a longer time to ignition. This suggests that burning structures from this material would be subject to a longer time for escape from the structure and would present lower fire risk than similar structures containing treated plywood. (4) TG results demonstrated that the presence of the flame retardant can decrease the pyrolysis temperature for hemicellulose and cellulose, change the decomposition and reaction progress for plywood degradation and promote dehydration carbonization and accelerated charformation. Moreover, the formed char was more stable than that combustion of untreated plywood. (5) The flame retardant contains nitrogen (N), phosphorus (P), boron (B), chlorine (Cl) and guanidine (Gu) compounds. The adhesive also contains N and P compounds. These substances display flame resistance and supplement each other to generate flame retardance than any one used alone. By changing the thermolysis and thermal decomposition processes, the heat release and smoke release from plywood, undergoing combustion was reduced. This controlled generation of combustible substances and promoted dehydration and carbonization to form char. As a result, the flame resistance of plywood was improved significantly. The probability of smoke asphyxia or poisoning death of those trapped in structures containing treated plywood during fire accidents can be decreased dramatically.

Performance study of phase change charging/discharging processes of condensing heat storage in cold regions based on a mathematical model

This paper firstly proposed and investigated a single-stage air source heat pump (ASHP) system combined with a novel phase change material (PCM) based storage device, also named as condensing heat storage, to solve the problems of poor heating performance of ASHP system under extreme conditions in cold regions. A mathematical model of the novel system was established and validated to comprehensively investigate the operating characteristics under initial conditions. The simulation results suggested that the PCM temperature in two-phase zone of condensing heat storage should not exceed its phase change end temperature during the charging process under initial conditions by controlling the charging time, in order to avoid damage to the system. The proposed system could achieve its steady state under initial conditions after operating time for 6 days. In addition, the results showed that the heat storage capacity of condensing heat storage was able to reach 100.59 kW·h and the average heat storage rate was 7.19 kW during the charging process under steady state. The heat storage capacity was sufficient to be provided for a 164 m2 room for 10 h theoretically with an average heat release rate of 10.06 kW, which achieved all-day continuous heat supply by the proposed system. Besides, the model was adopted to analyze the effects of some structural parameters of condensing heat storage on system heat storage performance. The system performed well in smaller fin pitch and smaller tube pitch, since both heat storage capacity and supply water temperature were increased under these circumstances.