Showing papers in "Journal of Thermal Science and Technology in 2010"

Heat Transfer Capacity of Lotus-type Porous Copper Heat Sink for Air Cooling

Abstract: Lotus-type porous metal with many straight pores is attractive as a heat sink because larger heat transfer capacity is obtained due to the small diameter of the pores. The heat transfer capacity of the lotus-type porous copper heat sink was calculated using the model with the pores of uniform diameters. However, actual lotus-type porous metals have a distribution of pore diameter. In the present work, we investigated the lotus-type porous copper fin model (non-uniform pore model) by considering size distribution of measured on the actual measurement of the pore diameters on a cross-section of the lotus-type porous copper fin. Prediction of the heat transfer characteristics for the lotus-type porous copper heat sink shows a good agreement with the experimental data. In addition, the predicted heat transfer coefficient of non-uniform pore model also shows a good agreement with the uniform pore models. Thus, it is clarified that the heat transfer characteristic of the lotus-type porous copper heat sink can be predicted by the uniform pore model.

Thermochemical Conversion of Sugarcane Bagasse into Bio-Crude Oils by Fluidized-Bed Pyrolysis Technology

Abstract: Thermochemical conversion of sugarcane bagasse into bio-crude oils by fluidized-bed reactor has been taken into consideration in this study. The bagasse in particle form was pyrolyzed in an externally heated 7cm diameter and 37.5cm high fluidized-bed reactor with nitrogen as a carrier gas. The reactor chamber and gas-preheater were heated by means of a renewable energy biomass source cylindrical heater. At a reactor bed temperature of 450°C for a feed particle size of 420-600µm and at a gas flow rate of 30 l/min, an oil yield of 48wt% of dry feed was obtained. The pyrolysis process temperature was found to have influenced on the product yields. Characterization of the whole pyrolysis liquids obtained at optimum operating conditions has been carried out including physical properties, elemental analyses, GCV, FT-IR, and 1H NMR analysis. The results show that pyrolysis of sugarcane bagasse waste is a good option for producing bio-crude oils to be used as alternative to petroleum fuels and valuable chemical feedstocks.

Heat Transfer Characteristics and Reynolds Stress Budgets in Single-Rib Mounting Channel

Abstract: Heat transfer and fluid flow in a single-rib mounting channel were investigated by directly solving Navier-Stokes and energy equations. Flow and thermal fields were considered to be fully developed at the inlet of the channel, and the simulation was made for spatial advancement of turbulent heat transfer. Keeping the frictional Reynolds number, Reτ0, at 150, the rib height ratio was changed in four steps from H/δ = 0.05 to H/δ = 0.4. Computational results were confirmed to be nearly independent of grid meshes. In addition, numerical accuracy was confirmed through close agreement between computed mean pressure and the experiment by Yao et al. (1995). The numerical results revealed that the highest value of the mean Nusslet number was as large as 1.3 times the smooth surface consuming the same pumping power, and the local enhancement of heat transfer was correlated with the turbulence increase near the rib front and the reattachment point. According to the Reynolds stress budgets for H/δ = 0.2, there were mechanisms to induce powerful fluctuations: (1) Streamwise fluctuation was increased through production by flow deceleration in the upstream of the rib; (2) Redistribution to wall-normal and spanwise fluctuations was fortified by the fluid splattering to the rib front. Therefore, excellent performance of heat transfer was concluded to occur due to flow structures, which induce the strong disturbance near the rib front triggering smooth transition of the separated shear layer.

Submicroscale Flow Sensor Employing Suspended Hot Film with Carbon Nanotube Fins

Abstract: A submicroscale flow sensor has been developed that consists of a suspended hot film and carbon nanotube (CNT) fins. Flow measurement experiments, together with a theoretical model, revealed the advantages of the use of CNT fins. The suspended metal film reduces heat loss and the CNT fins enhance the heat transfer to the fluid flow. Herein, the working principle of the CNT fins is presented in detail, together with a description of the micro electro mechanical systems (MEMS) / nano electro mechanical systems (NEMS) techniques used to fabricate the sensor. The CNTs were deposited by a manipulation method that is based on dielectrophoresis.

Optimal Shape Design of Compact Heat Exchangers Based on Adjoint Analysis of Momentum and Heat Transfer

Abstract: An adjoint-based shape optimization method of heat exchangers, which takes into account the heat transfer performance with the pressure loss penalty, is proposed, and its effectiveness is examined through a series of numerical simulation. Undulated heat transfer surface is optimized under an isothermal heated condition based on the variational method with the first derivative of the cost function, which is determined by an adjoint analysis of momentum and heat transfer. When applied to a modeled heat-exchanger passage with a pair of oblique wavy walls, the present optimization method refines the duct shape so as to enhance the heat transfer while suppressing the flow separation. It is shown that the j/f factor is further increased by 4% from the best value of the initial obliquely wavy duct. The effects of the initial wave amplitude upon the shape evolution process are also investigated.

Performance Analysis of Waste Heat Driven Pressurized Adsorption Chiller

Abstract: This article presents the transient modeling and performance of waste heat driven pressurized adsorption chillers for refrigeration at subzero applications. This innovative adsorption chiller employs pitch-based activated carbon of type Maxsorb III (adsorbent) with refrigerant R134a as the adsorbent-adsorbate pair. It consists of an evaporator, a condenser and two adsorber/desorber beds, and it utilizes a low-grade heat source to power the batch-operated cycle. The ranges of heat source temperatures are between 55 to 90 °C whilst the cooling water temperature needed to reject heat is at 30 °C. A parametric analysis is presented in the study where the effects of inlet temperature, adsorption/desorption cycle time and switching time on the system performance are reported in terms of cooling capacity and coefficient of performance.

Evaluation of the Flame Lift-off Length in Diesel Spray Combustion Based on Flame Extinction

Abstract: The interaction of spray and combustion processes forms a complex system of physical phenomena undergoing in IC engines. Studying this interaction is important to determine strategies for simultaneously reducing soot and NOx emissions from diesel engines. Spray combustion interactions are evaluated by the flame lift-off length - the distance from the injector orifice to the location of hydroxyl luminescence closest to the injector in the flame jet. Various works have been dedicated to successful simulations of lifted flames of a diesel jet by use of various combustion modeling approaches. In this work, flame surface density and flamelet concepts were used to model the diesel lift-off length. Numerical studies have been performed with the ECFM3Z model and n-Heptane fuel to determine the flame lift-off length under quiescent conditions. The numerical results showed good agreement with experimental data, which were obtained from an optically accessible constant volume chamber and presented at the Engine Combustion Network (ECN) of Sandia National Laboratories. It was shown that at a certain distance downstream from the injector orifice, stoichiometric scalar dissipation rate matched the extinction scalar dissipation rate. This computed extinction scalar dissipation rate correlated well with the flame lift-off length. For the range of conditions investigated, adequate quantitative agreement was obtained with the experimental measurements of lift-off length under various ambient gas O2 concentrations and ambient gas densities.

Experimental study of permeability of porous medium containing methane hydrate

Abstract: An experimental system which is suitable for measuring permeability under a certain condition,was established to study the effect of Methane Hydrate contained in porous medium on permeability.The relationship between porosity and permeability of porous medium was studied.Several experiments were carried out to test the permeability with different saturation of Methane Hydrate in the porous medium which was substituted by BZ-01 or BZ-02 glass beads.The result showed that the existence of Methane Hydrate in the porous medium would result in an sharp drop in permeability.The relationship between saturation and permeability is exponential.Based on the experimental data,a function of porous medium-saturation was derived to get the corresponding permeability.By comparing the modeling result with the experimental result,It is found that the Methane Hydrate that grew under the experimental condition fit the parallel-capillary model,that means Hydrate took up the centre of the capillary while the flow in the porous medium developed into annular flow.

Thermodynamic Analysis of Expansion Profile for Displacement-type Expander in Low-temperature Rankine Cycle

Abstract: Thermodynamic analysis of the isentropic and polytropic expansion profiles of typical working fluids was carried out in order to design a highly efficient displacement-type expander for a low-temperature Rankine cycle. First, expansion profiles were analyzed for three typical working fluids: HFC245fa, ammonia, and supercritical CO 2. The hot-side temperature ranged from 60 ° to 120 °C, and the cold-side temperature was 10 °C. In the analysis, isentropic and polytropic expansion processes were assumed to behave thermodynamically. In the analysis results, we noted similarities among the expansion profiles for different hot-side temperatures. This similarity allowed us to introduce the unique concept of a variable mechanism for expansion profile fitting in displacement-type expanders. This variable expansion mechanism can be achieved by simply adjusting the position of the inlet and/or outlet port of the expander. © 2010 by JSME.

Development of an Ethanol Reduced Kinetic Mechanism Based on the Quasi-Steady State Assumption and Feasibility Evaluation for Multi-Dimensional Flame Analysis

Abstract: A 20-step reduced kinetic mechanism of ethanol, a potential sustainable energy source as a biofuel, was developed based on the detailed reaction mechanism proposed by Saxena and Williams using the Computational Singular Perturbation (CSP) method based on the Quasi-steady State Assumption (QSSA). Feasibility evaluation of the reduced kinetic mechanism for multi-dimensional flame analysis, i.e., the difference in numerical results and convergence time between the detailed reaction mechanism and the reduced kinetic mechanism, was also performed to investigate the applicability of the ethanol reduced kinetic mechanism to the development of practical combustors. To consider further industrial applications, the reduced kinetic mechanism was incorporated into the commercial computational fluid dynamics (CFD) code FLUENT 6.3.26 using the User Defined Function (UDF) code developed in the present study. Numerical results calculated with the detailed reaction mechanism and the reduced kinetic mechanism, i.e., temperature profiles, chemical species profiles and laminar burning velocities, were in good agreement for both two-dimensional premixed and non-premixed flame calculations. Convergence time using the reduced kinetic mechanism was considerably reduced compared to that using the detailed reaction mechanism, indicating the applicability and advantage of a reduced kinetic mechanism based on QSSA for multi-dimensional flame analysis. An additional reduction of the computational time was achieved by using both the reduced kinetic mechanism and In Situ Adaptive Tabulation (ISAT) solver by Pope et al.

Propagation and Extinction of a Cylindrical Premixed Flame Undergoing Equivalence Ratio Fluctuation Near the Lean Limit

Abstract: Experimental study was made to investigate the propagation and extinction characteristics of a stretched cylindrical flame undergoing periodic fluctuation of equivalence ratio near the lean limit. With a lean methane-air and a lean propane-air mixture, burning velocity, flame luminosity and flame stretch rate were measured or evaluated for the fluctuation frequencies of 5Hz and 20Hz. The results were summarized as follows: (1) In some part of a period, burning velocity and flame luminosity of the dynamic flame near the lean limit were possible to become lower than those at the lean flammability limit of the static flame. (2) At the high frequency of 20Hz, the burning velocity took a negative value in a certain time range. In spite of this loss of propagation ability, the flame was not extinguished but sustained, indicating the recovery of the flame intensity due to the dynamic effect of fluctuating flame. (3) Flame recovery phenomenon could occur more easily for the methane flame which was strengthened by the Lewis number effect than the propane flame which was weakened by that effect.

Numerical Analysis of Extremely-rich CH4/O2/H2O Premixed Flames at High Pressure and High Temperature Considering Production of Higher Hydrocarbons

Abstract: Numerical analysis of CH4/O2/H2O laminar premixed flame under various conditions of pressure, equivalence ratio and steam concentration was performed using GRI-Mech 3.0 and the mechanism proposed by Davis and Law, which consists of C1 to C6 hydrocarbons in addition to GRI-Mech 3.0. The pressure dependence of laminar burning velocity and flame structure under fuel-rich conditions was focused on. Effects of the formation of higher hydrocarbons under fuel-rich conditions were also clarified using the mechanism proposed by Davis and Law. Results showed that for extremely fuel-rich conditions, laminar burning velocity increases as pressure increases for both mechanisms. The increase of laminar burning velocity is caused by the shift of the oxidation pathway of CH3 radical from the C2 Route to the C1 Route. The formation of C3-C6 hydrocarbons has only a small effect on laminar burning velocity. Under fuel-rich conditions, super-adiabatic flame temperature (SAFT) occurs and its pressure dependency was clarified.

Characterization of the Spray of the DISI Multi-hole Injector by Means of Phase Doppler Anemometer

Abstract: The spray from a multi-hole injector applied to direct injection spark ignition (DISI) engine was investigated. In order to understand the detailed structure of the transient spray near the nozzle a combined LDA/PDA system was used. PDA system was optimized in order to detect relative smaller droplets. Size-classified technique was used to get deep information about the spray characterizations near nozzle. The experiments were performed at 7 MPa of injection pressure. At early stage of spray the droplet velocity distribution in the centre of the spray showed high value. Smaller droplets under 15 µm showing followability to air flow, while larger droplets over 20 µm will have drag due to momentum decay. Droplets of 15

Transient Shock Formation of Pulsed Electrothermal Plasma Discharge Confined in an Extended Bore

Abstract: An electrothermal gun possesses a great potential to be an efficient source of pulsed plasma discharge for nanomaterials production or thermal plasma spray coatings. A plasma discharge by intense pulsed power is numerically studied utilizing time-dependent gas dynamics equations which are solved by FCT (flux-corrected transport) algorithm in two-dimensional domain of the interior capillary bore region and the external region of extended bore. Plasma conditions at the bore exit, mass ablation of polycarbonate bore wall, and degree of ionization are determined at different levels of transient arc current profile. As a way to controlling the plasma discharge, the extended bore at the capillary exit is considered and the flow pattern of pulsed plasma discharge in the extended bore exhibit complex shock structure from slightly to highly underexpanded jet depending on the level of arc current profiles. Flow instability of oscillating Mach disk is found at higher level of arc current profile cases.

Asymptotic Analysis on High-temperature Premixed Flames: Instability of Flame Fronts under the Constant-enthalpy Conditions

Abstract: Asymptotic analysis on premixed flames with high-temperature combustible mixtures was performed to elucidate the instability of flame fronts. Planar premixed flames with sufficiently low Mach numbers were treated, and a one-step irreversible chemical reaction with sufficiently high activation energy was assumed. Through the asymptotic analysis, we obtained the formula for the burning velocity, depending on the temperature of burned and unburned gases and on the mass fraction of fuel. To investigate the instability of high-temperature premixed flames under the constant-enthalpy conditions, we obtained the instability intensity which depended on the burning velocity and on the temperature ratio of burned and unburned gases, where the burned-gas temperature was constant. As the unburned-gas temperature became higher, the instability intensity became higher, except for premixed flames with low reaction exponents under the conditions of constant-density unburned gases. This was because that the instability intensity was determined by the competition between the increase of the burning velocity and the decrease of the temperature ratio.

An Experimental Study on Combustion Dynamics and NOx Emission of a Swirl Stabilized Combustor with Secondary Fuel Injection

Abstract: To study the relations between the amounts of NO x emission, noise level, and level of pressure fluctuations as the output quantities of an experimental swirl-stabilised combustor and two variables of overall equivalence ratio (ϕ) and secondary fuel injection rate (Q sec), as its input quantities, two different data mining approaches were employed in the present work (i.e., artificial neural network (ANN) and multiple polynomial regression (MPR) techniques). The related experiments were already carried out using four different types of secondary fuel injectors with an overall equivalence ratio (ϕ) in the range of 0.7~0.9. The results indicate that both the ANN and MPR methods have lower predicting capability for estimation of noise level and the level of pressure fluctuations compared with that of the emission index. Also the results show that the ANN has better predicting capability, for estimation of various combustor parameters, than the MPR method.

Analysis of Dehumidification Effects on Cooling Capacity of an Evaporative Cooler

Abstract: In this study, effect of desiccant wheel, heat exchanger and cooling coil will be evaluated on decreasing the wet bulb temperature of entering air to cooling tower and decreasing the outlet cold water temperature. For this purpose, change effect of desiccant wheel parameters will be investigated on wet bulb temperature of outlet air from heat exchanger. After that, optimum parameters and minimum wet bulb temperature will be selected. Then, outlet cold water temperature will be achieved for various cooling coil surface temperature with definition of by pass factor and also by using optimum desiccant wheel parameters and entrance air wet bulb temperature to tower related to cooling coil surface temperature. To calculate wet bulb temperature, a mathematical model will be used that shows physical properties of air. After that a nomograph will be used to predict effect of decrease of entrance air wet bulb temperature on reducing the outlet water temperature and it will be done for several cities in Iran. At the end, an equation will be used to calculate required water to air mass flow rate for each outlet cold water temperature. With considering of known circulating water mass flow rate, required air for tower would be calculated and suitable desiccant wheel can be selected.

Viscosity Correlation for 2,3,3,3-Tetrafluoropropene (HFO-1234yf) Based on the Extended Corresponding States Model

Abstract: The viscosity of 2,3,3,3-tetrafluoropropene (HFO-1234yf) has been successfully correlated with the extended corresponding states (ECS) model for transport properties. The thermodynamic equation of state developed in our earlier work forms the basis of this work. The viscosity correlation presented here is valid for temperatures from 260 K to 340 K and for pressures up to 20 MPa. The correlation can be applied to both liquid and gas phases in a single procedure. The estimated uncertainties are 2 % for liquid phase and 2.5 % for gas phase, which roughly correspond to experimental uncertainties.

Diagnostic Technique for Deterioration Inspection of Metallic Products through the In situ Measurement Using a Thermophysical Handy Tester

Abstract: This paper proposes a non-destructive technique using a thermophysical handy tester to inspect the deterioration of metallic products. In the early stage of fatigue in a metallic body, many micro-cracks appear on the surface of the stressed body. As fatigue progresses, these micro-cracks multiply and grow, while the apparent thermal conductivity of the surface layer spontaneously decreases. This phenomenon introduces the possibility of determining the progress of deterioration through in situ measurement of thermophysical properties. To estimate the degree of deterioration of materials, a dimensionless deterioration factor α is introduced. In order to corroborate this technique, several fatigue tests using carbon steels were conducted herein. Throughout the tests, apparent thermal conductivities and deterioration factors up to the limit of fatigue were periodically measured using a thermophysical handy tester. Furthermore, microscopic observations to investigate the evolution of micro-cracks were performed for stage-assessment during the period of fatigue tests. The results clearly demonstrate that this technique is useful for the non-destructive diagnosis of such deterioration.

Direct Transition Phenomena in Pool Boiling of FC-72

Abstract: The direct transition boiling process from non-boiling to film boiling at critical heat flux (CHF) by exponentially increasing heat input, Q0exp(t/τ), was investigated in a pool of FC-72. Investigations were made on a 1.0 mm diameter gold horizontal cylinder heater under a wide range of system pressures for saturated condition. Direct transition predominantly occurs from heat conduction process in the non-boiling regime by rapid increasing heat input and then followed by incipient boiling and CHF simultaneously. However, during quasi-steady-state heat transfer, it was observed that the direct transition also occurs from single phase natural convection at around atmospheric pressure and by an extent of pre-pressure, which was given to the cylinder surface at atmospheric pressure. Direct transition phenomena were confirmed to exist due to the explosive-like heterogeneous spontaneous nucleation (HSN) in originally flooded cavities on surface. The predictions of direct transition phenomena were also derived from typical incipient boiling superheat and CHF.

Experimental study on pressure drop and heat transfer characteristics of plate heat exchanger

Abstract: The heat transfer correlation was fitted by qualitative Reynolds number method based on the experimental data obtained from the experimental system of the liquid-liquid type plate heat exchanger.Meanwhile,the general relationship between Reynolds number and friction factor was found.All of these provide a basis for the design and calculation of plate heat exchanger.The performance of plate heat exchanger was evaluated based on heat transfer and power consumption ratio and the main factors which affect its performance were identified.It is clarified that it is not an economical way to increase the heat transfer performance by improving the flow only.

Numerical simulation on phase change heat transfer of paraffin in metal foams

Abstract: The melting process of phase change materials(PCMs) in high porosity metal foams was studied.A two-temperature model was used because of the large thermal difference between metal frame and PCMs.Apparent heat capacity method was used to simulate the melting heat transfer process of paraffin.The simulation results indicate that metal foams makes the temperature distribution of the phase change material more even;There is big temperature difference between metal frame and PCM during phase change,and local thermal non-equilibrium is obvious;Melting speed becomes fast with the decreasing of metal foams porosity.

Analysis on features of power plant cold-end system and optimization

Abstract: On the basis of the performance analysis of the power plant cold-end system,the main factors influencing the performance of the cold-end were presented and the optimization of operating principle was analyzedA mathematical model for the optimal operation of the cold-end system was established by analyzing the operating performance of the systemAn optimal software,based on this optimal model,was developed for the cold-end systemCase study of the optimal operation of the cold-end system and the economic analysis were carried out by using the software developed and the optimal curvesResult has validated the efficiency and accuracy of the model and the softwareThe result shows that the model and software are of great importance for the optimal operation and energy saving of the power plant both theoretically and practically

Application of cone calorimeter on study of burning performance of liquorice

Abstract: Burning performance of liquorice were tested by cone calorimeter.The results indicates that liquorice is easy to ignite,the minimum ignition heat flux is 5.882 2 kW/m2.During the early time of the ignition of liquorice,because the carbonized layer is thick,the peak HRR under lower heat flux is larger,the average HRR increase with the increase of heat flux,which indicates that the early fire risk of liquorice can't be ignored.During the early time of the ignition of liquorice,SEA and CO production is larger,which decrease with the increase of heat flux.

Theoretical analysis and experimental study on backdraft

Abstract: Backdraft is one of special behaviors of enclosure fires with strong concealment and suddennessOnce backdraft occurs in an enclosure,the fire will quickly engulf the entire enclosure and form a huge extrusive fireball out of the vent openingsIn the circumstance,it is very difficult for people in the enclosure to evacuate and for firemen to extinguishThe experimental investigations on backdraft in enclosure fires caused by solid fuels were carried out,and the phenomenon of backdraft was reproduced in the small-scale enclosure fire testsAccording to the theories of heat transfer and fire dynamics,the theoretical model of conditions that backdraft occurs in enclosure fires was established,and the critical condition expressions wss deducedCombining the results of theoretical analyses with ones of experimental studies,a new backdraft criterion expressed by β,which is the ration between the combustible gas volume fraction and the lower explosive limit of mixture,was put forward

Some considerations of pyrometry optimization based on measurement uncertainties

Abstract: Three-color pyrometry with the non-calibration mode was used as an extension of two-color pyrometry.Based on the inherent measurement uncertainties,the analyses of pyrometry optimization were carried out.The optimization purpose was to investigate the effects of inverse algorithms and wavelengths combinations on temperature measurements.Through numerical simulations based on the measurement uncertainties,different iterative algorithms for three-color method and traditional two-color method were compared to determine the optimum iterative algorithm.The choice of wavelengths combination is another important optimization issue.Due to the coupling characteristics of data processing of three wavelength channels,the effects of spectrum wavelengths to measurements greatly differed from the disposals of single-color method and two-color method.Through numerical analyses,the optimization combinations of three wavelengths under the specified measurement conditions were also obtained.The above discussions are necessary for the actual measurement applications of pyrometry.

Investigation on Impact of Separator Structure on In-Plane Distribution of Coupling Phenomena in Single Cell of PEFC to Realize Uniform Distribution

Abstract: To point out the dominant factor of mass, heat and electric charge transfer phenomena in a single cell of PEFC for the promotion of power generation performance, the impact of gas channel pitch on in-plane distribution of mass concentration and temperature on reaction surface is investigated by simulation and experiment. Two-dimensional model of single cell which has the different gas channel pitch is simulated by CFD software. In the experiment using the separators which have different gas channel pitches, the data of power generation and in-plane distribution of temperature measured by thermograph are acquired to verify the simulation result. As a result, the in-plane distribution of gas, water and temperature on the reaction surface becomes more even with decreasing gas channel pitch under the condition investigated in this study, resulting that the power generation performance is promoted. With decreasing gas channel pitch, the temperature in observation area is dropped and total voltage is elevated. To enhance the power generation performance of PEFC under the conditions investigated in this study, the flow rate of supply gas of stoichiometric ratio of 1.00 and the gas channel pitch of 0.5 mm can be proposed.

Study of fire characteristics of vertical-adherent Thermoplastic materials

Abstract: The combustion characteristics and the effect on fire development and spread of Thermoplastic building decoration materials in fire was studied.Changes of mass loss rate,fire spread rate,and CO concentration of two kinds of typical thermoplastic materials were analyzed.In vertical-adherent and top-down combustion cases,the thickness,liquidity and thermal properties are the main factors affecting the combustion characteristics.The mass loss rate and CO concentration changes in the same order.The mass loss rate and CO concentration of PMMA increase with the increasing of thickness and the impact of thickness decreases with the increase of thickness.

Experimental study of effects of inhibitors on coal oxidation based on cone calorimeter

Abstract: The effect of the inhibitors on the temperature oxidation of coal was studied by cone calorimeter multi-angle experiments.The results maybe helpful in choosing of the coal inhibitor.Effects on coal ignition time;heat release rate and CO2 production rate of the inhibitor of MgCl2 and water-absorbent resin were investigated.The results showed that inhibited coal adding MgCl2 has the longest ignition time that can be up to 369s,and has the least heat release rate;Inhibited coal adding MgCl2 in the middle period of combustion has the highest CO release rate;Inhibited coals adding antioxidant in the later period of combustion,have larger CO release rate;Inhibited coal adding MgCl2 has the least specific extinction area;Inhibited coals adding antioxidant has larger specific extinction area in the prior period and diminish in the later period.The study indicates that the same inhibited coal sample has not identical effect with different experiment parameter;MgCl2 has the best effect on inhibiting coal oxidation;antioxidant has greater effect on inhibiting coal oxidation in the later stages.