Five different methods were used to calculate the critical temperatures and critical pressures of four kinds of binary mixtures, and the accuracy of different methods in estimating critical properties of binary mixtures were studied. It is found that the critical properties calculated by the Peng-Robinson (PR) equation and the Soave-Redlich-Kwong (SRK) equation combined with critical judgement, which was proposed by Heidemann and Khalil, showed a good agreement with experimental data. And results calculated by the modified Chueh-Prausnitz (MCP) method, the Redlich-Kister method and the Radial Basis Function Neural Networks (RBFNN) were also in good agreement with experimental data. The maximum absolute deviations of the critical temperatures calculated by the PR equation, the SRK equation, the MCP method, the Redlich-Kister method, and the RBFNN are 1.82%, 1.73%, 0.95%, 0.17% and 0.20%, respectively. The maximum absolute deviations of the critical pressures calculated by the PR equation, the SRK equation, the MCP method, the Redlich-Kister method, and the RBFNN are 6.07%, 5.04%, 3.49%, 1.90% and 0.67%, respectively.

The equation of radiation temperature measurement is put forward, and the functional relationship between the object and the instrument is established. By analyzing the radiation temperature measurement model, the conditions to realize radiation measurement for the real temperature is found, that is, using the specific wavelength at the intersection point of the emissivity curve of the object and the instrument, the real temperature can be obtained by closed solution of the specific instrument temperature. Waveband radiation sensing and primary spectrum function clusters are two key technologies to obtain the real temperature. The former is to “cover” specific wavelength with uncertain numerical value, while the latter provides wavelength coordinate axis to identify specific wavelength with different numerical value. Taking tungsten as an example, the influence of the number of specific wavelengths on temperature solution is analyzed, and the error formula of temperature measurement by primary spectrum pyrometry is given.

The biodiesel, comprised of fatty acid methyl ester and ethyl ester, is considered as an environment-friendly and promising alternative of fuel. The thermophysical properties of biodiesels as well as their components are essential information for the better knowledge of their industrial applications. For instance, in the spray and combustion processes of engine, isobaric specific heat capacity (c_p) of fuel has a significant influence on its heat-transfer characteristic. In this work, the c_p of methyl myristate are investigated using a flow calorimeter at the temperature range of 323.20—393.26 K and pressures up to 25.12 MPa. The expanded uncertainties of temperature and pressure are decided to be 0.02 K and 5 kPa respectively, while the relative expanded uncertainty of c_p is 1.45%. Then based on the experimental data, a correlation is proposed for calculating the c_p of methyl myristate, and a satisfactory agreement between calculated results and experimental values can be observed, with the average absolute relative deviation and maximum deviation of 0.13% and 0.38% respectively.

As one of the most important thermodynamic properties, isochoric specific heat capacity is related to the calculation of internal energy and entropy, is the key parameter of engineering design. What is more, isochoric specific heat capacity is derived by the second derivative of pressure with respect to temperature and is important for verifying the accuracy of equation of state. An adiabatic calorimeter was developed to measure the isochoric specific heat capacity. A spherical bomb with platinum resistance thermometer inserted was used to hold the measured liquid. The cooling capacity was provided by a mixed-refrigerant Joule-Thomson refrigerator. In view of the difficult problem of heat insulation in a wide temperature range, two adiabatic shields were arranged and the PID temperature control method was designed independently to reduce the temperature difference between the bomb and the adiabatic shield. The temperature difference between the bomb and the inner adiabatic shield was less than 0.2 K throughout the experiment. In order to verify the reliability of the experimental setup, the isochoric specific heat capacity data of isobutane were measured over temperatures from 279.10 K to 323.68 K. Satisfactory agreement with published heat capacity data is found and the average absolute relative deviation between this data and the values calculated from REFPROP 9.1 is 0.88%.

On the basis of the original solubility experimental system, a new experimental system using the visual isochoric method was developed to measure the solubility for a refrigerant and a lubricant. In new experimental system, visual experimental cell was added, thermostatic system was adjusted, and magnetic stirring system was modified. Solubilities of HFO1234yf in squalane was measured between 283.15 K and 348.15 K. The experimental data were correlated by PR equation of state with HVOS mixing rule in which the excess Gibbs free energy was represented by the NRTL equation. The absolute average deviation between experimental and calculated data was 1.22 %. Moreover, the immiscibility between HFO134yf and squalane was found from 283.15 K to 323.15 K.

Ethyl decanoate, as a member of fatty acid ethyl esters (FAEEs), is one of the main component of biodiesels. In order to obtain the thermophysical properties for the components of the biodiesels, this paper measured the the speed of sound in ethyl decanoate in the temperature range from 298.15 K to 508.15 K along four isobaric lines at p = (0.1, 2, 4 and 6) MPa by the Brillouin light scattering (BLS) method. The correlation for the speed of sound as a function of temperature and pressure is presented based on the experimental data, which provides convenience for engineering applications. The absolute average of relative deviation between the experimental data and the calculated results is 0.28% in the experimental p-T region. Besides, the experimental data of the speed of sound at atmosphere pressure were also used to assess the predictive ability of Wada’s model and the result shows that Wada’s model can be used to predict the speed of sound at atmosphere pressure for ethyl decanoate within a certain temperature range.

By establishing a theoretical model, the density of the molten salt is calculated and compared with the experimental data. The error analysis shows that the quadratic polynomial model is the best calculation method. Low-temperature eutectic region (LTER) of mixed molten salts is defined as the temperature range between the melting temperature of mixed salts and the highest melting temperature of component salts. The molten salt is a solid-liquid coexistence state in LTER, and the thermal properties cannot be directly measured. It must be obtained by a combination of theoretical research and experimental verification. Using the quadratic polynomial model,the density of the mixed molten salts in LTER is calculated by extrapolation method. The density in the whole temperature range is obtained with little error, which proves that the theoretical calculation method is feasible. In order to reduce the error in the molten salt density, the experimental data are from the same literature or the same research group.

R1233zd (E) has the advantages of non-toxic, environmentally friendly, non-flammable, and the ionic liquid has a wide liquid temperature range and good physicochemical properties. The combination of R1233zd(E) and ionic liquids can be an excellent pair of absorption refrigeration. In this paper, the solubility and diffusion coefficient of R1233zd (E) in [HMIM][PF₆] ionic liquid were measured. The temperature measurement range was 303.2—343.2 K, and the pressure measurement range was 23—140 kPa. In order to facilitate industrial application, the experimental results were correlated by NRTL equation and Arrhenius equation. The average deviation and maximum deviation between the calculated results and experimental data were 2.45% and 6.13%, respectively.

The state-of-the-art ab initio potentials and polarizabilities in the literature were used in this work to compute the second dielectric virial coefficient of pure light noble gases. The systems considered here are helium-4, helium-3, neon, and argon. The second dielectric virial coefficient was calculated using the classical statistical-mechanics formulas with quantum corrections up to the second order and the [1/1] Padé approximant was applied to extend the temperature range of the calculated values down to T = 25 K. The possible uncertainty sources of the present predictions and the uncertainty of the theoretical values estimated from the uncertainties of potentials and polarizabilities were identified. The critical assessment of the computed values and the experimental data in the literature with a relative larger uncertainty shows that the calculated values in this work can be used with confidence in research areas relating to the second dielectric virial coefficient of light noble gases.

Tetrahydrofuran (THF) hydrate is a typical cage structure hydrate, and there are few reports on the thermal conductivity of THF, meanwhile, there are many problems such as the measurement sample is not a single phase and the hydrate is decomposed during the measurement process. In this paper, time domain thermal reflectance (TDTR) technique based on femtosecond pulse laser is employed to measure the thermal conductivity of tetrahydrofuran hydrate. According to the characteristic that the sample is fluid at room temperature, a temperature control platform which can be used for both sample preparation and TDTR measurement is designed to realize the non-contact in-situ measurement of THF thermal conductivity. The result of THF thermal conductivity is 0.6 W/(m?K), and interface thermal conductivity between Al and THF is 90.3 MW/(m²·K). The experimental results obtained in this paper have great significance on understanding the microcosmic heat conduction mechanism of solid hydrates and clarifying the coupling relationship between the water molecules cage and guest molecules.

A molecular-thermodynamic theory has been developed for predicting the solubility of a sparingly soluble gas in a complex binary liquid mixture at 0.101325 MPa. The binary liquid mixtures contain associating and solvating components whose molecules form weak chemical compounds. The Gibbs energy for the mixing process is the sum of three isothermal steps. The partial molar excess Gibbs energy of the solute is represented by two contributions, chemical and physical. When experimental uncertainties are taken into account, the predicted solubility of nitrogen in the binary solvent is in good agreement with previously published experimental solubility data.

The influence of pulse heating duration on measurement and the f coefficient in the formula for calculating thermal parameters in the experiment of plane source-pulse transient method are theoretically analyzed. The corresponding experimental apparatus is established and some commonly used materials are measured in practice. The uncertainty of thermal conductivity, thermal diffusivity and volume heat capacity measurement are systematically analyzed.

Graphite film is widely used in heat dissipation of heat-generating devices in electronic equipment. In-plane thermal conductivity is the key parameter which describes the heat transfer performance. However, currently only the graphite bare material data is provided in the industry, and the glued graphite film cannot be tested. It brings great inconvenience to thermal design and product quality management. In this paper, a thermal imaging-based steady-state test method for the thermal conductivity of glued graphite film is proposed. The sample is directly adhered to the flat surface which is heated by electric heating film. The temperature gradient is integrated along a loop to eliminate the influence of non-uniform thermal flow, and the thermal loss on the surface and bypass are reduced by calibration. Experiments based on a variety of glued graphite film products and metal sheets with reference data verified the validity of the method. The comparison between the test data of the glued graphite film and the bare graphite material parameters showed that great difference may exist, indicating that the nominal performance and actual performance of the graphite film product may be significantly different, and that test on glued graphite film rather than bare material is necessary.

The protic ionic liquid (PIL) comprising with hexylethylenediaminium (HHex) cation and trifluoromethane sulfonate (TFS) anion forming [HHex][TFS] is hydrophilic and highly miscible with water ( H₂O /PIL above 90%(mass)) as there are two amines in the polar group. Therefore, in this study, the hydrogen bonding interaction between [HHex][TFS] and water molecules was investigated using the density functional theory (DFT) at M06-2X/6-311G (d,p) level, the configurations of [HHex][TFS]-nH₂O (n= 1, 2, 6) S1-S8 were designed and optimized . The results of molecular interaction (ΔE ₀ ^BSSE), vibration spectra (Δν), the second-order perturbation (E ⁽²⁾), and electron density (ρ _c) and Laplace value (?² ρ _c) show that the hydrogen bonding interaction increase with increasing the water content: S4 (n= 1)＜S6 (n= 2)＜S8 (n= 6).

Gravity-driven granular flowing across inverted drop-shaped tubes is investigated, with the aim to enhance flow and heat transfer performance and avoid particle stagnant. The discrete element method was used to simulate the flow and heat transfer of a gravity-driven particle flow across a circular tube and a drop-shaped tube with different ellipticities (e= 1.0, 1.5, 2.0, 2.5) was analyzed.t The effect of ellipticity on the size of the stagnation zone, the normal and tangential force on the pipe, and the effective heat transfer coefficient was compared with the circular tube. The main conclusions are as follows: compared with circular tube, granular flow drop-shaped tubes perform better in flow and stagnation avoidance. The stagnation area and the void area of the drop-shaped tube are smaller than the circular tube. As the ellipticity increases, the particle flow velocity at the top of the tube increases, and the flow upward the tube becomes better. The drop-shaped tube is subjected to the normal force and the tangential force of the granular flow and both are smaller than the circular tube. After the ellipticity is more than 1.0, the ellipticity is increased, and the two forces are no longer reduced. The effective heat transfer coefficient of the drop-shaped tube is smaller than that of the circular tube, and the effective heat transfer coefficient decreases as the ellipticity increases.

In order to investigate the pressure control behavior of cryogenic propellant tank and operating performance of thermodynamic vent system (TVS), a set of high-efficiency cryogenic fluid storage platform with liquid nitrogen as storage medium was set up, to simulate the pressure variations of liquid oxygen tank under the operation of TVS. The single variable control method was used to carry out the experimental research, which concentrate on the pressure control of TVS in a liquid nitrogen (LN₂) tank with different throttle rates and modes. The pressure, temperature variations and vent mass loss of LN₂ tank under different throttling parameters were analyzed. It was found that the duty rate of TVS decreases significantly with the increase of throttle rate, and the cooling capacity of the system is increased, which greatly reduces the TVS operating time. Based on the principle of reducing the working time and fluid mass loss, the optimal throttling ratio of TVS is obtained. On the other hand, the throttle opening has a remarkable influence on the cooling power of TVS, the large pressure difference helps to improve the cooling power.

Drag force model which characterized by the drag coefficient, acting as a crucial interface force model, was generally applied into the momentum equation of continuous phase and dispersed phase in Euler-Euler approach and Euler-Lagrange approach. Previous drag coefficient models of bubbles are required to sufficiently estimated due to the different forms and limited applicability. Optimal model is selected considered the applicability of exist models and the influence of bubble shape deformation, which is partitioned and characterized by Reynolds number and Weber number according to the related parameters adopted in previous models. The drag coefficient predicted by the present model generally perform better than previous models by comparing with experimental data. A more physically and accurate predictions of bubble motions can be achieved by adopting the present model in numerical simulations to track the locations of various size of bubbles.

Experimental study on mixing dynamic characteristics during down-flow spraying water into air at different speeds was carried out. The spray pressure varied between 0.1—1.5 MPa, and air speed between 14.6 m?s^-1 and 46.2 m?s^-1. The mix chamber was a transparent rectangle channel with cross section of 70 mm×70 mm. The velocity field and initial droplets size distribution were respectively measured by high speed photography and Malvern particle size meter. Results suggested that spray pressure mainly affected radial velocity and the axial velocity alongside spray axis. While the air speed mainly affected the axial velocity at outside boundary of plume. The mean axial velocity was introduced and used as the reference velocity for mixing. It was found increased with increasing spray distance or spray pressure. The initial particle size decreased with decreasing spray pressure or increasing relative velocity between air and water at nozzle exit. According to above experimental results, correlations for the mean axial velocity and initial droplet size was set up. The relative error between calculated and experimental results mainly fell within ±15%.

A thin film thermal sensor based on mica was fabricated by vacuum evaporation coating technology, which comprises a thermopile for heat flow measurement and a thermocouple for temperature measurement. Comprehensive test results show that mica substrate sensor perform satisfactorily. The static calibration fitting linear correlation coefficient of encapsulated film thermocouple can reach 0.999. Correlation coefficient of static calibration fitting line for film heat flow meter was 0.99439, probe coefficient was 8.78886 W/(m²?μV), and sensitivity of film heat flow meter was 0.11378 μV/(W/m²). Dynamic response time of the film thermocouple measured twice was 0.446 s. As the loading heat flow increased, the dynamic response time of film heat flow meter increased. Response time was 0.483 s when the step heat flow value was 600 W/m².

In this paper, a square cavity with mass and heat source was studied with the background of fire. According to the different Rayleigh number(Ra) and buoyance ratio Nc, S_rand D_f, the heat and mass transfer law and nonlinear characteristics of the fluid in the cavity are discussed. The results show that the critical Ra_c causes the fluid flow to change from the heat-induced driving flow to the convection-driven flow. As Ra increases the heat and mass transfer of the surface of the heat and mass source, the fluid changes from steady-state flow to oscillating state. When Nc>-1, the convective heat transfer coefficient and the convective mass transfer coefficient increase, and the fluid transforms from steady state to double-period oscillation, and finally to chaos. Increasing S_r and D_f can increase flow and heat and mass transfer.

Heat transfer performance of a finned oval tube heat exchanger with various air inlet angles (30°,45°,60° and 90°, respectively) were experimentally investigated in this study. Experimental results showed that heat transfer performance decreased with decreasing air inlet angle, and the experimental correlation of the air-side Nusselt number was obtained in the studied range of Reynolds numbers and air inlet angles. Heat transfer performance of various air inlet angles was simulated by using CFD software Ansys Fluent, and the simulated results agreed well with the experimental results. The numerical results indicated that with the decrease of air inlet angle, the uniformity of air velocity distribution in z-direction became worse, therefore, the comprehensive heat transfer performance was worse than that of the case with uniform flow distribution.

Proton exchange membrane fuel cells (PEMFC) show great potential to be considered as a renewable power system for future automobile applications due to their high power density and low operating temperature. However, a successful startup from subfreezing temperatures is a major challenge for the commercialization of PEMFC. In this research, a three-dimensional electrochemical-transport coupled model is developed. The model accounts the flow and heat transfer of the coolant during the cold start process. A detailed visualization analysis is conducted to illustrate the effects of a coolant system on the cold start performance. Our results include reactants concentration profiles, voltage curves, temperature distribution, and ice formation. The model validation results show good agreement between the model prediction and experimental data. Therefore, the model can be used to achieve a better understanding of PEMFCs cold start behavior.

The existence of hot spots on the surface of pebbles in pebble reactors affects the safety of the reactor and its formation is closely related to the local flow of coolant at the pebble scale. In order to ensure the accuracy and physical reality of the solution, the large eddy simulation (LES) method and the fully structured grid are applied to conduct the numerical analysis of the local flow and heat transfer of the face-centered cubic (FCC) unit in the area contact arrangement mode. The characteristics of unsteady flow and its effect on convective heat transfer are analyzed. The time-averaged temperature distribution indicates that there are stable hot spots on the surface of pebbles, and it is also found that the instantaneous temperature fluctuation on the surface of pebble is large, and there are also instantaneous hot spots where the temperature is significantly higher than the time-averaged temperature.

Reducing the reaction temperature during the raw liquid injection stage will lead to different viscosities of liquid, and result in particles adhesion forming agglomeration in different sizes, this hinders heat transfer to reacting liquid and slows the cracking reactions. Therefore, particles agglomeration is an important and challenging problem for thermal cracking in fluid cokers. In the present study, the gas shroud attachment was used to improve nozzle structure, and the particles agglomeration process during nozzle injection of multi-viscosity liquid was investigated in a fluidized bed operated at different conditions based on a conductance method using a water-sand system to simulate the hot bitumen-coke system at room temperature. The results show that the porous gas shroud attachment can create an ideal dilute phase environment for liquid injection and avoid the droplets accumulation in the injection cavity and particles exchange area. Different stages can be observed during the liquid injection dispersion throughout the bed, i.e., the wetting stage, the agglomerate formation stage, and the agglomerate segregation stage. A higher gas-liquid ratio (GLR) of the nozzle provides a method to prevent particles agglomeration, and the conditions at a high gas velocity allow a higher concentration of sucrose in the liquid injection compared with that at a low fluidizing gas velocity. This study provides a theoretical basis for on-line monitoring of particles agglomeration during liquid injection to guarantee perfect contact between the atomized droplets and the bed particles.

The micro particles’suspension and sedimentation processes were quantitatively studied by using a self-developed micro particle real-time online analyzer. After verifying the accuracy and reliability of the self-developed micro particle analyzer, three micro particles of different densities, the latex particle reference material, Al₂O₃ and ZrO₂, were selected to conduct experiments. Through monitoring the suspension and gravity sedimentation processes, the particles’concentration and granularity distribution information were then obtained. The results show that the Al₂O₃ particles exhibit non-uniform distribution state even under super-critical suspension speed. And the particles’granularity and density play a significant role in solid-liquor separation during the transient process of gravity deposition.

A horizontal sleeve tube heat exchanger filled with three-layer phase change materials is proposed, and a comprehensive storage density evaluation criterion of the heat storage device is established. Based on the criterion, the effects of separated walls, fin arrangements and direction are numerically predicted and investigated. The results show that the natural convection of PCM (phase change material) is significantly suppressed by separated walls, and the higher the phase change temperature, the more significant the suppression effect. Compared with the sleeve tube heat exchanger without fins, the comprehensive thermal storage efficiency for the exchanger with fins in each layer PCM is improved by 2.27 times. The variations of PCM liquid fraction can be divided into two different stages under various fin arrangement directions, and the evenly arranged fin structure (Case2) has superior thermal storage performance. The non-uniformity of the PCM melting rate in each layer is a key factor that restricts the overall system performance of the thermal storage characteristics. Compared with Case2, the uniformity of the melting rate between different-layer PCMs can be significantly improved by Case5, and the comprehensive thermal storage efficiency is improved by 28.30%.

This paper presents a numerical investigation on the condensation characteristics of vapor with non-condensable gas in corrugated tubes. Several 2D examples with different corrugated structures, air contents and Reynolds numbers are studied and compared. Results show that along with the increase of air content, the wall average heat transfer coefficient decreases in the corrugated tube. The oscillation of fluid flow and heat transfer is generated due to the corrugated structure. With the increasing of wave height, the skin friction coefficient increased, and the wall average heat transfer coefficient first increased, and then decreased, the maximum of wall average heat transfer coefficient in this paper is in 0.032 m. The influence of wave height on the flow and heat transfer characteristics is more obvious than the width of the wave node and the space between two waves. The effect of inlet fluid flow-rate on the skin friction coefficient is also evaluated and discussed to provide some guidelines for future engineering applications.

The formation of intracellular ice of cells can cause severe cellular damage leading to many problems in cryopreservation. The broad bean was used as the research object, and the cytoskeleton was dissolved by cytochalasin B, and the freezing experiment was carried out at different cooling rates using a low temperature microscopic system. The experimental results show that the cells treated with cytochalasin B have higher crystallization temperature and shorter crystallization time during the freezing process, but the cytoskeleton has little effect on the growth process of intracellular ice. The external conditions play a key role, and the inoculation of ice crystals affects the formation temperature of ice crystals in the cells and the growth rate of ice crystals. Finally, the degree of damage to the cells was analyzed by light intensity map. It was found that the growth process of intracellular ice without cytoskeleton was similar to that of normal cells, but the crystallization rate was different, indicating that the cytoskeleton inside the cells affected the initiation of intracellular ice. Therefore, keeping the cytoskeleton intact before cryopreserving the plant sample can reduce the formation of intracellular ice and maintain cell morphology after rewarming.

Water content of natural gas affects the quality and safety of pipeline transportation. As one of the main methods of gas concentration detection, non-contact laser detection has been widely used. In order to solve the problem of stray radiation on high temperature wall during laser detection, an on-line laser detection optical path for water content of natural gas pipeline was designed. The influence of stray radiation on the received signal of detector was simulated by TracePro. The optical characteristics of the process were analyzed based on the principle of spectral absorption. The results show that there is obvious stray radiation in the process of measuring water content of natural gas in pipeline by laser, and the stray radiation effect is stronger in high temperature environment.

The heating performance of space heating heat pump (SHHP) with dual-cylinder rotary compressor was tested at low ambient temperature (T_od) in the range of -30—0℃, and water outlet temperature (T_wo) in the range of 41—50℃. The results show that ambient temperature has great influence on its discharge temperature and evaporating temperature, but little on condensing temperature; hot water outlet temperature has great influence on its condensing temperature, and little influence on its discharge temperature and evaporating temperature. With the decrease of ambient temperature, the heat capacity of SHHP decreases sharply, when T_wo = 41℃, T_od decreases from 0℃ to -30℃, and the heat capacity decreases by 62.16%. With the increase of outlet temperature, the heat capacity of SHHP decreases slowly, when T_od = 0℃, T_wo rises from 41℃ to 45℃, the heat capacity decreases by only 5.61%. The influence of ambient temperature on COP_h value is also obvious, when T_wo = 41℃, T_od decreases from 0℃ to -30℃, COP_h decreases from 2.94 to 1.38, a drop of 53.06%. The SHHP with dual-cylinder rotary compressor has good practical value to be applied in low temperature condition of -30—0℃.

The agglomeration processes and fluidization behavior of cohesive particles in a turbulent agglomerator were simulated based on the coupled model of population balance method (PBM) and computational fluid dynamics (CFD). The agglomeration collision frequency model was improved by introducing the collision agglomeration efficiency and fractal dimension. The agglomeration collision efficiency was introduced by considering the influence of hydrodynamic force and van der Waals force on particle agglomeration. At the same time, the fractal dimension were introduced by considering the influence of the local porosity of non-spherical particle agglomeration increasing gradually in the radial direction. Thus the results of the simulation using the improved model compared with the EDEM simulation results and the experimental results. The volume fraction results show that the average relative error between the EDEM simulation results and the experimental results was 16.34%, while the average relative error between the improved model and the experimental results was only 7.39%. In terms of fraction of the agglomeration number, the average absolute error between the EDEM simulation results and the experimental results was 5.36%, while the average absolute error between the improved model and the experimental results was only 2.28%. Therefore, the improved model simulation results were closer to the experimental results.

In order to construct a universal prediction method for complete melting time, a concept of dimensionless heat storage time is introduced, which is defined as the ratio of actual melting time to referenced melting time. The referenced melting time obtained by static approximation method can basically reflect the non-linear relationship between the melting time and its influencing parameters, which effectively reduces the non-linearity of dimensionless melting time fitting correlation and enlarges its application scope. The influence of Stefan number, dimensionless length and ratio of outer diameter to inner diameter on dimensionless melting time of shell-and-tube latent heat thermal energy storage unit was analyzed by numerical simulation method, and the correlation equation was fitted. The results show that the empirical correlation has a wide application range and high prediction accuracy. Within the parameters considered in this paper, the error of fast prediction results is no more than 10%. The dimensionless heat storage time and its correlation method proposed in this paper can be popularized to other forms of solid-liquid phase change thermal energy storage devices.

The pulsating heat pipe (PHP) has achieved remarkable results in heat dissipation field of electronic devices for its unique advantages in heat transfer. Therefore, this paper proposed a novel saw-tooth corrugated structure PHP with two-bends. Besides, the impact of arrangement position of saw-tooth corrugated section on the operation performance of PHP was investigated by numerical simulation. The results indicate that the heat transfer performance and start-up characters of saw-tooth corrugated PHP are much better than that with traditional structure of PHP. Additionally, the PHP has the lowest start-up timing with the serrated corrugated section in both ends of the heat pipe. Especially, the novel structure PHP with serrated corrugated part in condensation section has lower thermal resistance and higher heat exchange. Thus, it could conclude that the novel saw-tooth corrugated PHP has the best operation performance as new structure is arranged in condensation section.

Based on the Euler two-phase flow model, a subcooled boiling heat transfer RPI (Rensselaer polytechnic institute) model of flow and heat transfer for internal combustion engines was established. Compared with the experimental results of Robinson’s rectangular channel, and the applicability and accuracy of the RPI model are verified. The model is applied to the calculation of direct coupled heat transfer in the cylinder head and cooling water jacket of an actual internal combustion engine, and the results of single-phase flow and two-phase flow are compared and analyzed. The results show that boiling heat transfer can obviously improve the heat transfer efficiency of cooling water jacket and reduce the high temperature of local area such as bridge passages, the error between calculation results and experiment results is smaller by using two-phase flow model considering boiling, and the error of measuring point temperature is reduced by 1.78% compared with that calculated by using convection heat transfer model.

An all-atom model of the ionic liquid 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([bmim] [Tf₂N]) was established. Molecular dynamics simulations were carried out at five different temperatures and five different pressures. The simulation results of [bmim][Tf₂N] density were in good agreement with the experimental results, which verified the accuracy of the model. In addition, the interaction energy of [bmim][Tf₂N] changes with temperature and pressure is analyzed. The results show that the Coulomb energy, van der Waals energy and long-range energy in the ionic liquid increase with temperature and the time required for the system to reach equilibrium becomes shorter. Relative to temperature, pressure has less influence on the internal interaction energy of the ionic liquid. Among various interaction energies, van der Waals has maximum energy change varing with temperature and pressure. Temperature and pressure have no effect on the configuration of the ionic liquid.

The quantitative analysis and amplification of the catalytic depolymerization process of low rank coal need a macroscopic dynmaic model to describe the process reasonably. In this work, the chemical percolation devolatilization (CPD) model was used to quantitatively analyze the catalytic depolymerization process of low-rank coal, combining with the corresponding catalytic depolymerization experiment which was carried out with Shaanxi long-flame coal. According to the experimental results, the reaction kinetic parameters were obtained based on the mechanism of the catalytic depolymerization. The simulated results showed a good agreement with the experimental data and can better reflect the difference of different stages of pyrolysis process, i.e., at lower temperature, the yield of catalytic depolymerization was also lower, and with further increasing the reaction temperature, the yield of products will be sharply increased and higher than that of raw coal pyrolysis. In this model, the effect of the catalyst on the yield of pyrolysis tar was reflected by the composite rate constant and the crosslinking reaction activation energy, and the tar yield increased with the increase of these two parameters. For the Fe-based catalysts, it can promote the cleavage of side chain resulting in the increase of gas yield. As for the Zn-based catalysts, it can inhibit the crosslink reaction. However, when the activation energy of the crosslink reaction was too higher, the increase of the tar yield was increased slowedown due to the restriction of reaction temperature.

To clarify the differences in parameters selection of different pyrolysis models and evaluate the adaptability of different models to pyrolysis reaction, the segmented single scanning rate method, iso-conversion kinetic method and the 3-stage Gaussian distribution activation energy model (3-DAEM) were applied to analyze the thermogravimetric experimental data of two low-rank coal. The results show that the kinetic parameters obtained by single scanning rate method cannot reveal the pyrolysis reaction mechanism well. The iso-conversion kinetic method can better obtain the activation energy and pre-exponential factor distribution. The data simulated by 3-DAEM fits best with experimental data, and only one TGA curve is needed to obtain the kinetic parameters suitable for the TGA curve at other heating rates. According to the activation energy distribution, coal pyrolysis can be divided into three stages corresponding to the three classes of dominant chemical bonds.

Esterification is one of the most important organic reactions and widely used in medicine, material, food and perfume etc. The traditional synthesis process of esters have the disadvantages such as long reaction time, low yield, serious pollution, side reaction and difficult separation. Microwave assisted synthesis of esters catalysized by ionic liquids have the advantages such as less time, efficiency, convenient separation and safety. The ionic liquid 1-butyl-3-methylimidazolium hydrogen was used as the catalytic to synthesize tributyl citrate. The process conditions of catalytic esterification of TBC were studied by microwave reaction technology. The effects of alkyd ratio, amount of catalyst and reaction time on the final conversion of reaction were investigated. The process conditions of microwave synthesis of TBC were optimized by orthogonal design, and microwave synthesis under the catalysis of ionic liquid was obtained. The optimum conditions are as follows: the amount of catalyst is 15%, the reaction material alkyd ratio is 6.2∶1, the microwave reaction time is 4 h, the reaction temperature is 118℃, the microwave power is 600 W, and the conversion rate is 71.78%. The results of orthogonal analysis showed that the catalyst dosage had the greatest influence on the conversion rate and the reaction time was the second, and the influence of the alkyd ratio of the reaction material was relatively small. Compared with conventional heating and microwave radiation, the results show that microwave irradiation can effectively shorten the reaction time and reduce the reaction time from 7 h to 4 h. The reaction product was confirmed by Fourier transform infrared spectroscopy (FTIR), which confirmed that the target product was three butyl citrate. Viscosity analysis and other tests, all data are up to the standard.

At present, about 80% of rolling bearings are greased. The rheological properties of grease have an extremely important influence on the lubrication of rolling bearings. The rheological properties of grease cause the migration of base oil. The essence of this migration is the mass transfer process of the base oil in the grease. The mass transfer process of the grease in the rolling bearing has a very important influence on the lubrication of the bearing. In this process, due to the migration of the base oil in the grease, the distribution of the base oil in the grease is uneven, which causes the appearance of local areas with rich or lean oil. In this paper, the ash analysis method is used to study the mass transfer of grease at different rotation speeds and positions. The experimental conditions of different rotation speeds at different positions are experimentally studied by setting up the mass transfer separation characteristics test bench. The experimental rotation speeds of the separator are 100, 200, 400, 600, 800, 1000 r/min. At each rotation speed, the separation time was 0.5, 1 and 2 h. The grease is subjected to high-temperature sintering in a crucible to completely burn and decompose the grease, and the specific gravity of the ash and the grease is analyzed to determine the content of the base oil in the grease. The mass transfer phenomenon of grease is experimentally analyzed in detail. The research results show that when the rotation speed is 100 r/min, the mass transfer phenomenon of the base oil is obvious after a long time operation. When the rotation speed is 200—800 r/min, the base oil content in the internal position is higher, and the base oil content near the edge position is low and there is a lean state. When the rotation speed is 1000 r/min, the base oil undergoes a process of high to low and then high, and excessive migration of the base oil causes a lean condition. In the internal and intermediate positions, when the rotation speed is 800 r/min, the oil-poor state will be more obvious. At the edge position, the rotation speed is 100, 400 and 600 r/min will be more obvious. As a result of basic research, these results will lay the foundation for further research on rolling bearing grease lubrication.

Furnace temperature is an important parameter which can reflect boiler combustion status. However, furnace temperature is affected by many parameters and the mechanism is complicated. Therefore, it is difficult to establish accurate prediction model. To solve this problem, a multi-model intelligent combination algorithm (MICA) is proposed to construct an accurate prediction model. First, the actual production data is pre-processed by wavelet denoising algorithm, and the model input variables were selected based on classification and regression trees algorithm and mechanism analysis. Then, several furnace temperature prediction models are constructed by many data-driven algorithms. Finally, a C4.5 algorithm is applied to combine these models into a multi-model intelligent combination model. The experimental results illustrate that the proposed algorithm can construct an accurate furnace temperature prediction model through actual operating data.

Dynamic liquid level is an important parameter to reflect the liquid supply capacity of oil deposit. In the actual production site, dynamic liquid level is usually detected by the echo meter. This method is limited by the low detection efficiency, discrete measurement, and safety hazards. In addition to this, the existing prediction methods based on data-driven have difficulties in modeling due to the lack of historical data caused by various reasons. In response to the problem about lack of historical data, the multi-scale state characteristics which are closely connected with dynamic liquid level by analyzing the mechanism has been found out in this paper. Further, the state characteristics have been generated by using generative adversarial network (GAN). Simulation experiments have shown that the generated data can be used to establish dynamic liquid level prediction model and solve the problem about lack of historical data. On this basis, support vector regression (SVR) has been adopted as the modeling method and used in oil field production. Finally, the actual prediction results show that the proposed method is effective and meets the application requirements of oilfield engineering.

Sodium citrate (Na₃C₆H₅O₇) is widely used for food, medicine, chemical industry and many other fields due to its excellent performance. The extensive application has resulted in an increase of sodium citrate in industrial and municipal sewage and it aggravates the eutrophication of the water body. In this study, sodium citrate is applied as substrate for the anode electricigens and with which microbial fuel cell (MFC) represents good electricity generation performance. The results show that Na₃C₆H₅O₇-MFC achieves a maximum power density of 742.96 mW·m^-2, which is 1.77 and 1.12 times of that of sodium acetate (NaAc-MFC) and glucose (Glu-MFC), respectively. The start-up time of NaAc-MFC and Glu-MFC are about 1.8 and 2.9 times of that of Na₃C₆H₅O₇-MFC (57 h). The Coulombic efficiency of Na₃C₆H₅O₇-MFC is 61.31%, which is obviously superior to NaAc-MFC and Glu-MFC. This indicates that MFC can degrade sodium citrate in wastewater effectively, which provides a possibility of sodium citrate alone as substrate for MFC research.

The biggest technical difficulty in developing small drones is to solve the problems of their power systems. In order to maintain the flight of aircraft, the power system of small drone also provides energy for the airborne equipment. Therefore, the unmanned aerial vehicle (UAV) power unit requires a small volume with high energy density, and can be easily and efficiently converted into thrust force. In this paper, proton exchange membrane fuel cell (PEMFC) is used as the power source candidate of the UAV. Based on the PEMFC stack model and the environmental model, numerical simulations were conducted by Matlab to investigate the effect of altitude on operation status and thermodynamic performance of PEMFC system. The results indicated that as the height increases, the variations of system output voltage, output electric power and system electrical efficiency exhibit a downward trend. When the height is constant, the output power of the system has the highest value with the rise of current density, but the output voltage of the stack and the output efficiency of the system decrease. Moreover, it has been found that the increase of the hydrogen inlet pressure intensifies the output voltage, electric power and electrical efficiency of the system. For the purpose of performance improvement of PEMFC system at a certain height, it is necessary to select a suitable current density and a high hydrogen inlet pressure.

Direct absorption solar thermal collectors (DASC) explore the photo-thermal conversion characteristics of fluids to convert solar radiation into thermal energy. Plasmonic nanofluids have been used to improve the efficiency of DASC as working fluids, because of the localized surface plasmon resonance (LSPR) effect excited on the surface of metallic nanoparticles. Recently, Janus materials have witnessed fast development due to their diversified promising performances and practical applications. Compared with their spherical counterparts, Janus nanosheets have gained more concerns for their highly anisotropic shape. Herein, the discrete dipole approximation (DDA) is employed to calculate the extinction characteristics of Janus triangular nanosheets and sandwich-structured triangular nanosheets with different sizes. The results show that the LSPR of Janus nanosheets and sandwich-structured nanosheets can be improved by tuning the size. For Janus nanosheets, the thickness plays an important role on the resonance strength, whereas it has little effect on resonance frequency. On the contrary, the resonance strength and resonance frequency of sandwich-structured nanosheets can be influenced by the thickness evidently. Effective control of extinction characteristics can be achieved by varying the relative thickness of each layer of nanosheets, to adjust the extinction peak to the desired band. Optimizing the thickness of the Janus nanosheets and sandwich-structured nanosheets, or combining different sizes of nanosheets, will broaden the effective absorption band, thereby improve the photo-thermal conversion efficiency and the efficiency of direct absorption solar thermal collectors.

Due to the magnetoresistance effect, the temperature signal was different from the real one under high intensity magnetic field. Accurate temperature measurement is the key for preparation of materials or the measurement of material properties under magnetic environment. In this work, the temperature signal of E-type thermocouple and a PT100 platinum resistor were measured, with temperature range from -190℃ to 700℃ and magnetic field range from 0 to 5 T. The results show that, the temperature signal increases with magnetic field intensity increasing. However, the difference of temperature signal decreased with increasing heat power. Furthermore, the temperature rate was curve relation with temperature difference under different magnetic field.

In order to study the spectral radiation characteristics of carbon fiber, the finite difference time-domain method is used to investigate the radiation characteristics of carbon fiber in different configurations. The results show that the scattering factor of carbon fiber with the same radius in 2D random distribution decreases with the decrease in content of carbon fiber. When the content decreased by 17.12%, the maximum value of the scattering factor is decreased by 35%. Under the 2D random distribution of non-uniform radius carbon fiber, besides of the influence of carbon fiber content on the material’s radiation characteristics, the number of carbon fiber particles with small radius under the same content will increase the scattering factor by 20% in the 2.5—3.5 μm band. Compared with 2D random arrangement, 3D random arrangement can significantly enhance the radiation characteristics of carbon fiber.

The modified solution of SiO₂ aerogel was prepared by selecting anhydrous ethanol as solvent and SiO₂ aerogel as solute and was used to improve the thermal insulation performance of glass wool. Glass wool/SiO₂ aerogel combined boards were prepared by infiltration and prevailing pressure drying. The influence of the mass fraction of SiO₂ aerogel and the infiltration time on its performance was studied, and compared with the glass wool/SiO₂ aerogel combined board prepared by sol-gel method. The results show that the mass fraction of SiO₂ aerogel and infiltration time have significant influence on the properties of glass wool/SiO₂ aerogel combined board. When the mass fraction of SiO₂ aerogel reached 8% and the infiltration time was 20 min，the short-term water absorption and thermal conductivity of glass wool/SiO₂ aerogel combined board decreased by 38.09% and 18.32% respectively, and the compressive strength increased by 102.89%. Compared with sol-gel method, this method has the advantages of shorter preparation cycle, simpler process and lower cost, and is more suitable for large-scale production.

In recent years, fires have often occurred, such as the Notre Dame in Paris. Fire poses a great threat to human production and life and causes great losses to human life and property. In a fire, flashover is a special phenomenon. When an indoor fire occurs, all combustible surfaces in the building will ignite rapidly in a very short period of time, which greatly increases the difficulty of firefighting and rescue. In order to study the effect of fractal parameters of temperature on flashover discrimination in building fire, this paper uses fire dynamics simulator and direct numerical simulation method to calculate the situation of fire in a room with the corridor. According to the calculated results, the temperature field and flow field diagram of the physical model is obtained. On this basis, according to the basic principle of fractal theory, the nonlinearity of the temperature change process of the fire model is obtained. The characteristics of mutagenicity and fractal dimension reduction are analyzed and studied in depth. The temperature Hurst index of the fractal dynamic parameters of temperature sequence is determined by using the fractal theory R/S analysis method, and the Hurst index of the flashover occurs in the fire is calculated by taking the temperature of some point in the room as an example. The relationship between temperature Hurst index and flashover is analyzed and evaluated. It is found that with the occurrence of flashover, the Hurst index has obvious law of decreasing dimension and sudden change, and the time of dimensionality reduction is basically consistent with the time of flashover. This indicates that the temperature Hurst index is an effective nonlinear fractal dynamic parameter for evaluating the occurrence of fire flashover. The results show that the flame jet phenomenon is formed at the middle gate in 100 s and 200 s, and the temperature Hurst index is 0.22089 and 0.26781 at the corresponding time, respectively, which is in the state of anti-persistent series. In 300 seconds and after time, the temperature measured by a thermocouple in the room is in stable fluctuation state, and the Hurst index of temperature in the corresponding time is in a continuous series state. The fractal dimension of 100 s, 200 s and 300 s and later time is obviously reduced, that is, the Hurst index has a sudden change with the occurrence of flashover, and the time of dimensionality reduction is basically consistent with the time of flashover.