In this work, volume translation Soave-Redlich-Kwong (VTSRK) equation of state was applied to 2,3,3,3-tetrafluoroprop-1-ene (R1234yf), trans-1,3,3,3-tetrafluoro-1-prpene (R1234ze(E)), and their binary mixtures with CO₂.A temperature-dependent volume translation term was utilized to improve high density region representation.van der Waals mixing rules was applied for mixture representation.The binary interaction coefficient was regressed from literature experiment pressure-volume-temperature-component (pvTx) data.For the pure substances, single phase densities, vapor pressure, and saturated vapor and liquid densities were compared with reference equations of state (EOS).For R1234yf, vapor phase density relative root mean square deviation (RMSD) of the calculations from reference EOS was 0.74%, liquid phase density relative RMSD was 2.86%, saturation pressure relative RMSD was 1.20%, saturation vapor density relative RMSD was 2.51%, and saturation liquid density relative RMSD was 1.05%; while for R1234ze(E), vapor phase density relative RMSD was 0.59%, liquid phase density relative RMSD was 2.48%, vapor pressure relative RMSD was 1.14%, saturation vapor density relative RMSD was 2.37%, and saturation liquid density relative RMSD was 0.63%.Compared with the original Soave-Redlich-Kwong (SRK) equation of state, the VTSRK equation of state significantly improved the density representation in the liquid region and the saturation liquid line.For mixture density calculation, the equation was compared with literature experimental pvTx data in the vapor phase.For the binary mixture of R1234yf+CO₂, the relative RMS was 1.17%; for the binary mixture of R1234ze(E)+CO₂, the relative RMS was 0.82%.The result was much better than the original SRK EOS.The result showed that the VTSRK equation of state with the temperature-dependent volume translation term was accurate within 3% for the density representation of pure substances R1234yf and R1234ze(E), as well as of the binary mixture of R1234yf+CO₂ and R1234ze(E)+CO₂.

Molecular dynamic simulations were performed for the structural dynamics of cellobiose in the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl) under 1 atm and 800 atm.Results show that the interaction between cellobiose and ionic liquid is enhanced due to the formation of intermolecuar hydrogen bond, and thus break the intramolecular hydrogen bonding network within cellobiose under high pressure.Spatial distribution functions were calculated for the visualization of the solvation environments of cellobiose under 1 atm and 800 atm, and the intra- and intermolecular hydrogen bonding effect were quantitatively investigated by using radial distribution functions.The results would be helpful for understanding about the mechanism of dissolving cellobiose in ionic liquid at chemical bond level.

The solid composite sorbents based on the matrix of expanded natural graphite treated with sulfuric acid are developed, and a MnCl₂/CaCl₂-NH₃ resorption refrigeration system driven by low-grade thermal energy is established and experimentally investigated.Results indicate that 160℃ heat source temperature is the inflection temperature of coefficient of performance for refrigeration (COP), and a maximum cooling power of 2.98 kW is achieved.When the heating temperature is higher than 160℃, sensible heat load of the system increases which means keeping heating high temperature salt (HTS) sorption bed will reduce the overall refrigeration efficiency.For refrigeration temperature of 15℃, COP of the system ranges from 0.284 to 0.396 while specific cooling power (SCP) ranges from 100.3 to 338.8 W·kg^-1.SCP increases with the increment of heat source temperature.

Based on the sorption and desorption cycle to realize fresh water production from the atmosphere, the sorption air-to-water device is designed and experimental research on this device is carried out.The device is mainly composed of solar collector, sorbent bed and condenser.In night the water in the air is sorbed by the sorbents and in the daytime the composite sorbents desorb the water vapor using solar energy.Four kinds of novel composite sorbents are prepared and several tests on this device are carried out, which are SC (type C silica-gel)-CaCl₂, SC-LiCl, ACF (active carbon felt)-CaCl₂ and ACF-LiCl.The experimental results show that:the performance of composite sorbents whose host material is ACF is better than sorbents whose host material is SC.The sorption and desorption performance of ACF-LiCl is the best, when the outlet temperature of sorbent bed is 90℃,the freshwater yield is 0.412 kg water·(kg sorbent)^-1 after six hours desorption.

The traditional air source heat pump(ASHP) space cooling system adopts 45℃ outlet water temperature(OWT) and 40℃ inlet water temperature(IWT).Reducing the IWT can enhance the unit efficiency leading to decreasing heat capacity.So adopting small-delta temperature terminal is necessary.Considering the modern building comes equipped with ventilator, the ventilator can support part load so that lower IWT strategy can be used to enhance unit efficiency.The IWT can be reduced to 30℃ under the premise of satisfying the indoor thermal load.This kind of system with higher COP and lower power consumption is an energy saving system.The Dymola model is established to verify the experimental results, then conducting the simulation of system energy consumption of actual air conditioning system.

Pressure, temperature, vapor-liquid interface and other parameters of a liquid oxygen tank for long-term storage in orbit are simulated through CFD (computational fluid dynamics) method.The average heat leak of the tank in orbit is calculated, and it is 6.84 W·m^-2.The tank is simulated for 5 days, and the result indicates that the vapor region formed at the top of the tank is unstable, and the temperature of the liquid region is uniform as the thermal stratification is weakened by the high-speed vapor mass inside the liquid region.During the storage process in orbit, the temperature increase rate of the liquid is 1.18 K·d^-1, and the pressure increase rate of the tank is 23.7 kPa·d^-1.According to the flow field inside the tank, the homogeneous model is established, and results calculated by the model are coincided with the CFD method.Therefore, the homogeneous model is favorable for the prediction of pressure, evaporation and other parameters in the cryogenic propellant tank for long-term storage in orbit.

Slush hydrogen is a mixture of solid hydrogen and liquid hydrogen.It can be used as the fuel of rocket and space booster compared with the liquid hydrogen due to the higher density and heat capacity.In the present study, a numerical model was built based on the Eulerian-Eulerian model and kinetic theory of granular flow to investigate the flow and heat transfer characteristics of slush hydrogen in a horizontal pipe.For different heat fluxes, flow velocities and particle diameters of the slush hydrogen, it was found that the temperature of fluid can be decreased while using slush hydrogen instead of liquid hydrogen so that the vaporization of liquid hydrogen can be suppressed.The increase of flow velocity can make the distribution of particle more uniform and enhance the average heat transfer coefficient of slush hydrogen along the tube.Small diameter particle can improve the heat transfer between the solid phase and liquid phase and the melting of slush hydrogen can be accelerated.

This paper mainly simulates liquid nitrogen cavitating flow over a three-dimensional twisted hydrofoil (Twist-11N) based on large eddy simulation (LES) turbulence model.The period of shedding cavitation is observed according to pressure fluctuation characteristics at specific monitoring points.Compared with cavitation of water, cryogenics cavitation shows distinctness.Are-entrant jet and a pair of side-entrant jets are observed during cavitating evolution, which is unrevealed in two-dimensional cavitation.The vortex analysis of the interaction between shedding cavitation and the flowing field is performed.It is indicated that the occurrence of cavitation first leads to the unsteady of flow and thus vortexes occur, which further causes the boundary layer separation and cavity shedding.

An experimental investigation of falling-film generation outside vertical tube with lithium chloride aqueous solution was conducted.For the purpose of the development of a high performance of heat and mass transfer utilizing a lithium chloride aqueous solution as the working pair in solar absorption refrigeration system which use the low grade source, an experimental apparatus is set up to study the process of heat and mass transfer in generator using low temperature source.The experiments show that how the operation conditions such as the flow rate of hot water and the solution, the temperature of the heat source, the concentration of the solution and the system pressure influent the generation process.Some contrast experiments at the same condition with lithium bromide are carried on.The variation trend of the vertical falling film generation with lithium chloride aqueous solution is similar with that with lithium bromide aqueous solution.Although the mass rate of falling film generation with lithium chloride aqueous solution is slightly lower than that using lithium bromide aqueous solution, it has little difference in the effect of heat and mass transfer, and it is good for the performance of the system cycle which using the two working pairs becoming higher at the same condition because of the low operation concentration of lithium chloride aqueous solution.

Ground temperature distribution around vertical borehole heat exchangers (BHEs) has significant impacts on the performance of ground source heat pumps (GSHPs).It is essential to predict the long-term ground temperature distribution in the design and application of GSHPs.This study develops a three-dimensional numerical model for predicting the ground temperature distribution and GSHP operating performance.Air boundary, groundwater seepage and soil stratification have been taken into account.In order to minimize the computational load, the whole BHE is regarded as a linear heat source.The top boundary condition is set to the Cauchy boundary condition.The unsteady energy equation is calculated to improve the computational stability using the Alternating Direction Implicit method.Finally, this model is validated against data in literatures.Results have shown that absolute errors are all less than ±1.00℃.Predicted temperatures inside the soil are highly accurate (errors less than ±0.20℃) while the biggest error occurs at the outer wall of BHE.Therefore, this model can accurately and quickly predict the long-term ground temperature distribution and GSHP operating performance, especially in areas where complex seepages and apparent soil stratifications exist.

Theoretical analyses on auto-cascade ejector refrigeration cycle with one-step dephlegmation and two-step dephlegmation were performed to discuss the influence of mixed refrigerant composition, condensing temperature and refrigeration temperature on the cycle performance using zeotropic mixture refrigerant R23/R134a.The results show that when the mass fraction of the low boiling point component in the mixed refrigerant increases, the ejector pressure ratios decrease and the cycle COP increases, when condensing temperature increases, the ejector pressure ratios increase and COP decreases significantly, and when evaporating temperature increases, the ejector pressure ratios decrease, and the cycle COP increases.Under the same working conditions, COP of two-step dephlegmation cycle is greater than that of one-step dephlegmation cycle.Two-step dephlegmation cycle can obtain lower refrigeration temperature at -15℃ under the pressure ratio of ejector is about 1.8.

Stable aqueous suspensions of multi-walled carbon nanotubes (MWCNTs) with mass fractions ranging from 0.0015% to 0.1% were prepared via two-step method.The impacts of mass fraction, setting time, and heating times on the optical absorption property of MWCNT-H₂O nanofluid were investigated according to the transmittance measured by UV-VIS-NIR spectrophotometer over the wavelength from 200 to 2000 nm.Furthermore, an insolation experiment was performed to investigate the effects of mass fraction and light irradiation times on the photo-thermal property of MWCNT-H₂O nanofluids.Results show that the transmittance of MWCNT-H₂O nanofluid was decreased evidently after the addition of MWCNTs in deionized (DI) water, and long setting time leads to smaller transmittance.Heating is beneficial to improve light-absorption property of nanofluids.An optimal mass fraction of 0.01% with respect to the best photo-thermal conversion was found.Compared to DI water, the temperature of MWCNT-H₂O nanofluid at the optimal mass fraction was increased by about 15.1℃ (or 22.7%) after a lighting time of 45 min.Additionally, photo-thermal conversion performance is enhanced with increasing the lighting time at a low concentration of nanofluid, while it is just opposite at higher concentrations.The nanoparticle agglomeration may account for the above results.

The convection heat transfer characteristics of supercritical CO₂ cooled in horizontal helically coiled tube is studied experimentally and numerically.The effects of mass flux, heat flux and pressure on heat transfer for helically coiled tube are analyzed.The comparisons of the heat transfer coefficients are made between the straight tube and the helically coiled tube.And, the heating and cooling conditions for the helically coiled tube are compared.Results show that the heat transfer coefficient is lager in helically coiled tube than straight tube under the same condition.With the decrease of the mass flux and the increase of pressure, the heat transfer enhancement of the helically coiled tube is improved compared to the straight tube.For a given heat flux, the heat transfer coefficients are larger at cooling conditions than that at heating conditions in helically coiled tube.Furthermore, the heat transfer coefficients at heating conditions experience drastically oscillation due to the buoyancy force.

By discretizing the population equation into different size groups, a method was established for solving the population balance equation coupled with multiphase flow field.A computational fluid dynamics simulation with population balance model was performed for the scraped surface freezer.The algorithm considering nucleation rate, growth rate, crystal aggregation and breakage was used for describing the water dynamic ice-making crystallization process.By using this model, the key role of crystal aggregation and breakage was reappraised, and the ice crystals number density distributions were obtained in the scraped surface freezer.Then the influence of temperature, scraping speed and the crystallization time on the dynamic crystallization process of the water was studied.The results show that the crystal size distribution would be more centralized and uniform with the crystals aggregation and breakage; if the supercold temperature difference is less than 20℃ and the scraping speed is not more than 10 r·s^-1, the crystallization process would be accelerated by reducing the wall temperature or increasing the scraping speed.

Rhombus heat transfer surface with staggered circular tubes bundles (CTB)performed high heat transfer capacity, large fluid flow resistance and high efficiency in ash blowing.Based on that, a new rhombus heat transfer surface with staggered elliptical tube bundles (ETB)was proposed.The new heat transfer surface maintained the high heat transfer coefficient and efficiency in ash blowing of CTB, which also showed lower resistance characteristic.2D numerical simulations of rhombus heat transfer surface with CTB and ETB were presented to conduct improving the performance in heat transfer and fluid flow.The effects of different upwind angels (-45°, 0°, 45°)of ETB were discussed.To obtain an understanding of the physical behavior of thermal and fluid flow, different Reynolds numbers ranging from 3000 to 21000 were calculated.Entropy generation principle was used to investigate the heat transfer performance.Results showed that compared with CTB and other ETB, ETB with 0° upwind angel had higher heat transfer coefficient and lower flow resistance, comprehensive properties of which was better.

The phase-change refrigeration system of cascade pump-compressor is aimed at high heat flux components heat radiation cooling technology.The characteristics of starting and stable operation and the adaptability on high-temperature environment are investigated in this paper.The results show that at the first stage of the mechanical pump starting,because of the flow characteristics of the refrigerant and the inlet suction effect, the pressure increased firstly and then decreased.At the start time of the heat source, less pressure and temperature fluctuations, heat source starts stably.At stable operation stage, not only the flow rate of system increases from 2.22 g·s^-1 to 5.56 g·s^-1,but also the dryness of the evaporator' outlet declines, pressure drop of the evaporator' outlet increases and the surface temperature of evaporator declines.In the high temperature environment, the refrigeration system can meet the demand of the cooling requirement of heat source, and the fluctuation of pressure and outlet temperature rises.

1-(Propyl amine)ethyl-3-methyl chloride ionic liquid ([N₂C₃MIM]Cl) was prepared on the base of N-methylimidazole by 1,2-dichloroethane to obtain the intermediates 1-chloro-ethyl-3-methyl chloride ionic liquid ([CeMIM]Cl)and then reacting with 1,3-propanediamine.The chemical structure of [N₂C₃MIM]Cl was confirmed by FT-IR and ¹H NMR.[N₂C₃MIM]Cl possessed a lower REDOX potential (-0.522 V) through cyclic voltammetry measurement,[N₂C₃MIM]Cl presented a perfect coordination property compared with organic ligands.The obtained ionic liquid[N₂C₃MIM]Cl coordinated with CuBr was used to catalyze atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA)and it indicated by gel permeation chromatography (GPC) that the coordination ionic liquid[N₂C₃MIM]Cl presented the perfect controllability to the ATRP reactions.The residues of Cu²⁺ in polymerization product PMMA was only 270 mg·kg^-1 by atomic absorption spectrometry determination.It showed that[N₂C₃MIM]Cl was conducive to the separation of catalyst from the obtained product compared with the traditional organic ligands.

Ionic liquid 1-allyl-3-methyl-imidazole chloride ([Amim]Cl) as reaction medium,the microcrystalline cellulose graft poly methylacrylic acid (MCC-g-P4VP) polymer with pH-sensitivity were synthesized by atom transfer radical polymerization (ATRP).The model drug Aspirin was entrapped in polymeric micelles by dialysis method.The release mechanism of drug loaded micelle in vitro was analyzed.The polymer structure,micellar morphology,performance of aspirin loading and drug releasing were characterized by means of FT-IR,¹H NMR,TEM,XRD and UV-Vis.The results showed that the micelle could form spherical morphology micelles by self-assembly in aqueous solution, it presented a perfect encapsulation about Aspirin.It was found that the cumulant release of Aspirin in basic environment was higher than that in acidic environment.The drug loaded micelle showed excellent properties of pH-sensitivity and drug sustained-release.

The narrow molecular weight distribution of poly methyl methacrylate (PMMA) was synthesized by atom transfer radical polymerization (ATRP) in the ionic liquid 1-allyl-3-methylimidazolium chloride ([AMIM]Cl). Dibromo ethyl isobutyrate(2-Ebib) was used as the initiator and CuBr/ethanediamine was the catalytic system.Polymerization conditions were explored on molecular weight and distribution of PMMA.Molecular weight size and molecular weight size distribution were determined by GPC.The results showed that the molecular weight size of PMMA was mainly controlled by reaction time and the molecular weight size distribution of PMMA was controlled by catalyst system.Design of the molecular weight size and distribution of polymer could carry out by optimizing the reaction conditions to achieve precise control of polymers molecular weight.It has a perfect application potential in the field of chemical medicine.

The solid base catalyst KOH/ZrO₂was prepared by impregnation method,in which KOH was loaded onto a new support,ZrO₂,and followed by drying and high temperature calcinations.The catalyst was characterized by XRD,TGA-DSC and FT-IR respectively.The results show that KOH has been loaded on ZrO₂ successfully,which can be proved by the appearance of coordinated hydroxyls on the surface of ZrO₂.However,the crystal structure of KOH/ZrO₂ does not change significantly when compared with the structure of carrier.The preparation conditions for catalysts of different loading amount were determined via transesterification reaction.The optimal preparation conditions are as follows:loading amount of KOH 20%, calcination temperature 600℃,calcination time 2 h.The solid base catalyst KOH/ZrO₂ was applied in catalyzing the transesterification of soybean oil with methanol,and the maximum yield of biodiesel can be higher than 90%.The influence of the reaction variables on the conversion was also investigated,and the optimal reaction conditions are as follows:reaction temperature 75℃,oil/methanol molar ratio 9:1,reaction time 3 h,catalyst dosage 4.0%(mass).

A new type of consolidated composite sorbent for NH₄Cl/CaCl₂/MnCl₂ is developed by the mixture of ENG-TSA (expanded natural graphite treated by the sulfuric acid),and its sorption/desorption process is tested under non-equilibrium conditions.Compared with the theoretical Clapeyron curves under equilibrium conditions of three kinds of salt,the consolidated composite sorbent shows combining properties of three salts but there are also some differences.The consolidated composite sorbent shows some properties of the three metal chlorides respectively during the sorption/desorption experiments under non-equilibrium conditions.However,there is almost no sorption hysteresis which is prevalent in single salt-ammonia complexing process.On this basis,the COP and SCP of a single-stage sorption refrigeration cycle using the composite sorbent is calculated.The experiments prove that the performance of the consolidated composite multi-salt sorbent is better than single salt sorbents.

In this paper, one of the agent of alkaloid was extracted from the dry seeds of Holarrhena antidysenterica Wall.ex A.DC by ethanol, purified by silica gel chromatography and recrystallization.The structures of it was established on the basis of NMR techniques and mass spectrometry.The results showed that the optimum conditions of extraction were as follows:the Holarrhena antidysenterica Wall.ex A.DC was extracted under 60℃ for 6 h by 70% ethanol, and the getting rate of total alkaloid reached to 0.244%.By silica gel chromatography and recrystallization, the purity of one sample of compound 2 reached to 94.89%.The compound 2 was obtained as white crystal and its molecular formula C₂₄H₄₀N₂was established by mass spectrometry (m/z 356.59[M+H]⁺).From the NMR data, the structure of compound 2 was deduced as conessine and its ¹³C NMR data were consistent with those of literature.

Polyvinyl alcohol (PVA)is swelling and poor stability when it is made of membrane material, however, graphene oxide (GO)has good chemical stability. PVA/GO composite membranes with different GO content are prepared in this research, and PVA as the main raw material, GO for additives, PEG as the pore,adopting blending method. The hydrophilicity and pure water flux of the membrane are measured by the optical contact angle measuring instrument and the ultra filtration cup, and morphology, thermal and mechanical properties are characterized by SEM, IR, TGA and so on. The results showed that:addition of GO improve the internal channel, the hydrophilicity,anti-fouling property and the pure water flux, meanwhile, the thermal stability and mechanical properties of the membrane are improved. When the content of GO was 2%, the comprehensive performance of the membrane is optimized.

A model of air source heat pump air conditioning system is built based on TRNSYS.Based on the model, the operation of air source heat pump air conditioning system is simulated using the meteorological data of five climatic regions in China.The result shows that air source heat pump air conditioning system can be applied to most areas in China except severe cold regions, and the COP can reach to 3.2-3.5.Besides, the effect of heat transfer coefficient of building's exterior wall on the performance of air source heat pump air conditioning system is analyzed.It shows that the load of building and the energy consumption of the air conditioning system are linearly related to the heat transfer coefficient of building's exterior wall, and reducing the heat transfer coefficient of the external wall can effectively reduce the energy consumption.

Refrigerators with microchannel condenser is widely used recently.As for the dynamic simulation of this kind of refrigerators, a fast and accurate prediction model for microchannel condenser is needed.In this paper, several flat tubes in a flow path are simplified as one tube and each flow path is simplified as an element.With the simplification, a lumped parameter model for microchannel condenser is developed and the model is solved with iterations based on energy convergence criteria.The developed model is added into existing refrigerator system simulation platform and is used to predict the performance of one type of fridge with microchannel condenser on a mainstream PC.Computation time for the 24 h dynamic simulation of a refrigerator is less than 3 min.Results of simulation instances show that error between simulation results and experiments data for refrigerator total energy consumption is less than 9.5%.

To study the dynamic characteristics of double steam accumulators system.The mathematical models are based on the lumped parameter theory.The study has been carried out two different charging ways.One of them is the direct alternate and the other is the indirect alternate.The simulation results show as follows.The direct alternate charging way than the indirect alternate charging way less time 2.6 s.The pressure fluctuation of the direct alternate charging way is less than the pressure fluctuation of the indirect alternate charging way.In the same charging way,the fluctuation of drum pressure is less than the fluctuation of superheated steam pressure,and the fluctuation of superheated steam pressure is less than the fluctuation of steam supplying pipe pressure.The direct alternate charging way than the indirect alternate charging way fuel oil saving rate is 7.45%.Through data analysis can know.The advantage of the direct alternate charging way is charging faster and pressure fluctuation smaller and less fuel oil consumption.

As a new functional oil, the medium-chain triacylglycerols (MCTs) hold promising applications in diverse areas such as food, cosmetics and other fields.Several methods have been developed for the synthesis of MCTs, including traditional chemical processes and lipase-catalyzed, both them have great drawbacks such as the long reaction time.As a new alternative method, microwave irradiation on the esterification of caprylic/capric acids with glycerol was investigated in this study.Subsequently, Fourier-transform infrared spectrometry (FTIR) and gas chromatography mass spectrometry (GC/MS) were used to determine the structure and compositions of the liquid products, respectively.Compared to the conventional heating method, microwave assisted synthesis of MCTs shortened the reaction time greatly when achieving the same conversion.Response surface methodology (RSM) with a 3-level-3-factor central composite design (CCD) was applied to model and optimize the reaction conditions and, a quadratic model was developed as consequence, in order to correlate the preparation variable to the response.The optimum conditions for the synthesis of MCTs were as follows:reaction temperature of 190℃, substrate mole ratio (fatty acid:glycerol) of 3.33:1 and PTSA loading of 4.30%(mass).Under these conditions, the actual hydroxyl value 1.12 mg KOH·g^-1 was obtained, which is comparably well with the minimum predicted value of 1.03 mg KOH·g^-1, corresponding to the conversion yield was 99.7%.

The corrosion behavior of Incoloy 825 alloy was investigated in the different concentration of NH₄Cl solution by electrochemical impedance spectroscopy(EIS),polarization curve measurement and immersion corrosion test.The results show that the open circuit potential shifts negatively with the increase of concentration of NH₄Cl solution,i.e.,the corrosion tendency increases.The equivalent circuit of R_S(Q₁R₁)(Q_dlR_t)is used to fit the electrochemical impedance spectra.The EIS result reveals that the charge transfer resistance R_t decreases with the increasing of NH₄Cl solution concentration,meanwhile the passive current density and corrosion rate of Incoloy 825 alloy increases.The corrosion morphologies of the alloy are mainly localized corrosion,the intensity and size of pits increase with the increase of solution concentration.The results of EDS show that Cl^-involves in the electrochemical reaction process.

Using heat and mass recovery processes is a common way to improve system performance in the field of adsorption refrigeration.In this paper, an adsorption refrigeration system with serial heat recovery and mass recovery-like processes has been numerical studied and its dynamic simulation was made.Mathematical models of main components (including the evaporator which works as reservoir)are built, based on the characteristics of heat transfer in three layers.Simulation results indicate that when cooling time increases, coefficient of performance (COP) monotonically increases but specific cooling power (SCP) monotonically decreases.When heat time increases, both COP and SCP increase first and then drop and the optimal heat recovery time is 10 s.Both COP and SCP reduce while mass recovery time enlarges, meaning that the mass recovery does not make any improvement on system performance.When temperatures of hot water and chilled water increase and temperature of cooling water decreases, both COP and SCP rise.The curves of SCP vs hot water temperature, COP vs cooling water temperature and SCP vs cooling water temperature are nearly linear.The curve of COP vs hot water temperature is quadric.

Theoretical analysis shows that, for the cascade pulse tube configuration, its ideal cooling efficiency could possibly approach Carnot efficiency.A cascade pulse tube cooler with a built-in transmission tube between stages for energy recovery is suggested in this paper, the transmission tube is able to reverse the phase relation between mass flow and pressure wave and to transfer the acoustic power as much as possible to drive a secondary cooler.Theoretical analysis of an ideal transmission tube is carried out, which shows that it is possible to recover the acoustic power from the former stage to drive a secondary stage by choosing proper size of the tube.To verify this idea, a two stage cascade pulse tube cooler was designed, fabricated and tested.Experimental results show that the efficiency can be improved by 33% when the machine works at 233 K.

Liquid desiccant evaporative cooling air-conditioning system (LDECS),which combines both advantages of liquid desiccant and evaporative cooling technology,is a very promising alternative to the non-vapor-compression air-conditioning system.In this paper,a LDECS driven by low-grade heat is proposed,which consists of a liquid desiccant system with self-cycles that handles the total latent load and a regenerative evaporative cooler that removes the sensible heat.Mathematical models of the major components of the system are established to investigate the effects of four key parameters,namely,regenerator inlet solution temperature T_s,reg,in,solution-to-solution heat exchanger effectiveness ε_SSHX,ambient air temperature and relative humidity on steady-state thermal performance of the LDECS used as a dedicated outdoor air system.The results show that the supply air of 17.9℃ and 9.2 g·kg^-1 with the thermal coefficient of performance TCOP of 0.56 can be achieved under the typical summer condition of Nanjing. The T_s,reg,in of about 70℃ can achieve a high TCOP with the qualified supply air condition. The impacts of ε_SSHX on TCOP and the capacities of solution heater and cooler are more significant when the value of self-cycle ratio is smaller.Besides,the proposed LDECS is suitable for the application in hot-humid zone.

In southern China,photovoltaic air-conditioner(PVAC)has a great climate suitability since the energy consumption of air-conditioners is high while the sunshine is abundant there in summer.At present,researches on PVAC are mainly based on small-scale system.Study on commercial and large-scale PVAC is still lacking.The paper introduces the performance experiment and analysis of a photovoltaic direct-driven centrifugal water-cooled chiller in Zhuhai.Analysis index like grid-connected solar fraction is used.The part-load working condition,coefficient of performance and thermodynamical perfectness of the water chillers are also studied.The result shows that,in a typical day,the values of solar fraction,COP and thermodynamical perfectness of the system are 63.20%,6.64 and 65.94% respectively.The photovoltaic direct-driven centrifugal water-cooled chiller can work reliably and has a great energy-saving performance.

Solar photovoltaic/thermal integrated heat pump(PV/T-HP) is expected to realize comprehensive utilization of photovoltaics and thermal.To analyze the performance of PV/T-HP,mathematical models of PV/T evaporator,compressor,water tank and thermal expansion valve are established respectively and linked to form a complete thermodynamic cycle based on energy conservation,mass conservation equation.Simulation is carried out through MATLAB.The model accuracy is validated through direct expansion solar assisted heat pump(DX-SHAP) experiments.The result shows that the simulation error is about 5%,which is acceptable.Comparing the performance of PV/T-HP and DX-SHAP,with the rise in solar radiation intensity,COP both increases.With high solar radiation intensity,COP of PV/T-HP can be more than 5.The comprehensive COP of PV/T-HP is 7.4 on average,which is higher than that of DX-SHAP.The result shows that,PV/T-HP is conductive to reduce energy consumption of the system and improve the photoelectric conversion efficiency of photovoltaic modules,so it has more benefit on energy-saving.

Thermoacoustic heat engine is a type of energy conversion machine with the merits of high reliability and environmental friendliness.The present work focuses on a looped travelling-wave thermoacoustic refrigerator with one thermoacoustic engine stage and one thermoacoustic refrigerator stage,connected by resonators.The required acoustic field for an efficient travelling-wave thermoacoustic system is featured by high acoustic impedance and appropriate phase relation close to travelling wave in the regenerator.In the presented thermoacoustic refrigerator,the installation positions of the regenerators could dramatically affect the acoustic field inside them,due to the fact that the acoustic field is highly sensitive to the variation in acoustic impedance.In order to investigate the effect of the installation locations of the thermoacoustic cores on the performance of the thermoacoustic refrigerator,the looped travelling-wave thermoacoustic refrigerator is simulated with DeltaEC,which is a software widely used for the simulation of thermoacoustic systems.In the simulation,the working fluid is helium at a mean pressure of 3 MPa,and the heating temperature and the cooling temperature are 227℃ and 0℃,respectively.The overall coefficient of performance of the whole system,the efficiency of the engine stage,the coefficient of performance of the refrigerator stage,the acoustic impedance and the phase difference in the two regenerators with different installation positions of the two regenerators have been analyzed.According to the simulation results,when the ratio of the distance from the engine's regenerator to the refrigerator's regenerator in the direction of the acoustic wave to the loop length is 0.24,the maximum overall coefficient of performance can be reached,corresponding to a relative Carnot overall coefficient of 0.13.When the ratio is within 0.21-0.26,the two regenerators can both achieve efficient thermoacoustic conversion,leading to high performance of the whole system.However,when it is larger than 0.26 or smaller than 0.21,the performance of the two regenerators will deteriorate,leading to poor performance of the whole system.

R41 was selected to substitute for R23 in an auto-cascade refrigeration cycle with a rectifying column at-60℃.Performance comparisons and analyses were conducted when R1234ze(E) was selected as the less volatile component.An experimental apparatus was designed and established to compare the performances of R23/R1234ze(E) and R41/R1234ze(E) in the system.Both theoretical and experimental results showed that when adopting R1234ze(E) as the less volatile component,COP values decreased slightly and the compression work per unit volume decreased by 1/3-1/2 after the substitution of R41 for R23.Besides,the refrigeration capacity per unit volume also decreased slightly,but the refrigeration capacity per unit mass showed an obvious increase,which would result in significant refrigerant charge reduction.More importantly,the reduction in GWP of R41 would bring obvious environmental protection effect.

A novel thermochemical composite sorption heat storage cycle was described using reversible solid-gas chemical reaction.The thermal energy storage and energy upgrade characteristics for the low-grade thermal energy was analyzed theoretically.Meanwhile,the experimental research was carried out by employing the MnCl₂/SrCl₂/NH₃ as the working pair.The theoretical analysis suggested the thermochemical composite sorption heat storage cycle not only reduces the driving temperature of external heat source,but also can enhance significantly energy upgrade capacity compared to the thermochemical adsorption heat storage cycle.Compared to the thermochemical resorption energy storage cycle,it can provide the stable heat output temperature and further improve the thermal energy grade.Under the operation condition of charging temperature of 135℃ for the desorption of MnCl₂ and temperature of 12℃ for the adsorption of SrCl₂,desorption temperature of 90℃ for the regeneration of SrCl₂,condensation/evaporation temperature of 12℃,discharging temperature of 40℃ for MnCl₂ and SrCl₂,the obtained thermal energy storage efficiency is 93.31%.The heat storage density of MnCl₂-based composite sorbents is 4393.36 kJ·kg^-1 MnCl₂ or 3734.36 kJ·kg^-1 composite sorbents.Meanwhile,the heat storage density of SrCl₂-based composite sorbents is 1947.28 kJ·kg^-1 SrCl₂ or 1655.19 kJ·kg^-1 composite sorbents.The heat storage density of materials is as 10 to 20 times as that of the sensible heat storage and phase change heat storage materials.Therefore,thermochemical composite sorption heat storage is feasible and a very potential way in storing heat.It can be used for recovering the low-grade thermal energy to promote the highly efficient utilization of thermal energy.

A novel fin-tube collector/evaporator was used in a direct expansion solar assisted heat pump(DX-SAHP)water heater.The test rig was tested and several optimization schemes were proposed.The temperature of the collector is usually lower than ambient temperature,which means the collector can absorb heat not only from the solar radiation but also from the environment,so the collector efficiency is high.This novel collector has a bigger heat exchanger area compared with the same-sized roll-board collector.Experimental results show that the average COP of the DX-SAHP water heater can reach 5.37 when the temperature of 150-liter water is increased from 20℃ to 50℃ on sunny days in autumn.And the average COP can reach 3.43 even if on a rainy day with 18.6℃ average ambient temperature.A numerical model of the test rig was established and some optimization schemes for the collector were proposed.The computer simulation results show that the average COP of the DX-SAHP system can reach 6 when the temperature of 150L water is increased from 20℃ to 50℃ on sunny days after the optimization.

A novel closed type heat-power conversion system was proposed by integrating the essential principles of both reverse electrodialysis(RED)power generation technology and absorption refrigeration/heating technology.Besides,the working mediums solutions(consisted of solute and solvent) were found to be one of the vital factors for energy conversion efficiency of this new power generation system.Altogether,nine solutes(monovalent inorganic salts) and seventeen solvents(with the normal bubble point temperature within 40-150℃) have been selected as the focused substances,and their thirteen crucial properties(bubble point temperature,latent heat of vaporization,specific heat capacity,solubility,acentric factor,dipole moment,relative dielectric constant,electric conductance,viscosity,thermal conductance,auto-ignition temperature,flammability limit,and toxicity),have beencompared and analyzed.Further,methodology of comprehensively assessing the availability of working mediums for this new heat-power conversion system has been established after finishing a series of discussions that were carried out from the aspects of their fundamental thermophysical properties,transport features,electrochemistry characteristics,and dangerousness.Finally,it is ternary type working mediums that consisted of inorganic salt-solute-modifier,are deduced to be in bright prospect.

The mixing heating process of supplement water and original hot water in heat pump water heating system with single water storage tank results in the descend of water temperature in the tank,the high circulating heating temperature and the low efficiency of heat pump units.For this reason,the heat pump water heating system of double tanks(heating water-tank and heat storage tank) is introduced.The cold supplement water is heated to the setting temperature in the heating water-tank.Then it is sent to the heat storage tank by the recycling pump to supply users.It analyzes the system configuration and working principle of heat pump water system with double tanks.It is used in an air-source heat pumps heating water system of a university.The experimental study of this system results showed that the lower supplement water temperature and higher setting heating water temperature results in better energy saving effect compared with the heating pump system of single water tank.When the initial heating temperature and setting heating temperature is 14℃ and 55℃,the efficiency of double tanks system is increased by at least 19.31% than that of single tank system.

Too high temperature of a lithium-ion battery pack will reduce the discharge efficiency and accelerate the decay of battery life.In order to lower the temperature of the battery pack,a cooling system which inserted heat pipes among the batteries was designed.Based on the actual speed of electric vehicle,the temperature distribution of the battery pack under different speeds was numerically calculated.The results showed that the discharge current and the heat production increased sharply with the increase of vehicle speed,the discharge current reached up to 143 A at a vehicle speed of 120 km·h^-1,and the battery pack temperature exceeded 50℃ when the batteries discharged ending.Compared with the natural convection cooling system,the heat pipe cooling system made the average temperature of the battery pack reduce 4.6℃ and the temperature difference reduce 2.2℃.The temperature of battery pack was effectively reduced with the increase in length of condensation section of heat pipes.A satisfactory cooling requirement of the battery pack was obtained when the length of heat pipe condensing section was 50 mm.

A novel high performance composite heat storage material is prepared by using 13X zeolite as the porous substrate,using magnesium chloride as reactive salts.Its adsorption performance and heat storage properties are researched experimentally.Scanning electron microscope(SEM) is utilized to characterize the microstructure and morphology of composite materials.Automatic specific surface and porosity analyzer(ASAP 2460) is utilized to measure pore volume of the composite materials.Adsorption performance of composite materials is measured in constant temperature humidity chamber.Experimental data show adsorbance of the composite material with 29%(mass) MgCl₂ reached 0.75 g·g^-1.The influence of salt contents and relative humidity on the absorption performance of the composites is analyzed.Laser flash diffusivity apparatus(LFA)is used to measure the thermal diffusivities of pure zeolite and composites.Synchronous thermal analyzer(STA,one kind of TG-DSC instrument)is utilized to measure energy storage density of composites,results showed the composite material with 29% MgCl₂ reached 1628 kJ·kg^-1 and its volume storage density reached 412 kW·h·m^-3.Heat storage density of three kinds of adsorption processes(physical adsorption,chemical absorption and absorption of zeolite/MgCl₂ composite material) are quantitatively analyzed.

A multi-functional direct-expansion type of solar-air source heat pump system was developed,and the system performance was analyzed in theory and compared with the experiment result.The evaporator temperature is raised through solar energy input,which in return,translates into improvement in the thermal performance of the heat pump.An experimental prototype was investigated in spring and winter.In spring,when the solar radiation intensity is 856 W·m^-2,the average COP of the system produced hot-water is 5.78; when the heating performance of the system was tested in the sunny day of winter,the variation tendency of the COP went the same with that of solar radiation.But the collector efficiency moved in the opposite direction.The mean values of the COP and the efficiency were 5.8 and 0.64,respectively.By the contrast analysis,the relationship of the major parameters of the system was investigated in this paper.

The solar jet refrigeration system has the off-design characteristics of intermittent operation.In order to extend the operating time of the solar jet refrigeration system and achieve the optimal operating characteristics of the solar jet refrigeration system, the solar heat storage subsystem has been modified.Based on the thermodynamic model of the solar jet refrigeration system, the off-design thermodynamic characteristic of the system using R161 as refrigerants was studied.The results indicated that the improvement of the solar heat storage heating system can increase the operating time range of the solar jet refrigeration system and refrigerating efficiency.As compared to the conventional solar jet refrigeration system,the modified solar jet refrigeration system started to refrigerate two hours earlier, and its operating time was increased by 12.5%, and the coefficient of performance (COP) of the system was increased by 8.5%.The research results provide theoretical reference for the engineering design of the modified solar jet refrigeration system.

To utilize the renewable energy source from landfill gas(LFG) and reduce the consumption of fossil fuels,an LFG fueled biogas engine driven air source heat pump heating system was presented and its heating performance was studied.The type of the LFG collecting system and the LFG purifying process suitable for this system were determined.The experimental platform established can experimentally test two operating modes respectively,i.e.,the waste heat recovery from biogas engine exhaust fume alone or from both cylinder liner cooling water and exhaust fume simultaneously,by shifting the switching valves.The heating performance of the system was tested,and factors such as biogas engine speed,condenser water flow rate and condenser inlet water temperature,which have effect on the heating performance,were analyzed.Results of the experiment indicated that the total heating output of the system increased with biogas engine speed and condenser water flow rate,but it decreased with condenser water inlet temperature rise.Although the coefficient of performance(COP)and the primary energy ratio(PER) of the system reduced with condenser water inlet temperature rise as well,but their relationship with condenser water flow rate was not monotonic one.The study also revealed that the heating performance of the system was in its maximum when the condenser water flow rate ran at 1.45-1.65 kg·s^-1,and the COP and PER of the system reached their maximum of 4.3 and 1.48 respectively when the condenser water inlet temperature was 35-45℃.

Under low-temperature climate conditions,the compressor suction pressure and temperature are reduced owning to the decrease of the temperature of the inlet water and the outlet CO₂of the gas cooler in the trans-critical cycle CO₂ heat pump system.When the compressor suction pressure is less than the lower limit of the suction pressure,it leads to the unstable operation of the system.In order to overcome this drawback,a method of mixing water at the inlet of cold water in the gas cooler is presented.Proper quantities hot water in hot water tank is supplied to the cold water inlet of the gas cooler by a by-pass pipe.Adjusting the three-way valve to change the proportion of mixing water,the inlet temperature of gas cooler is increased to make the system run steadily under low-temperature climate conditions.Test results show that the method of mixing water could not only ensure the system of CO₂ air source heat pump hot water system works steadily under low-temperature conditions,but also increase operation time of the system and reduce the frequency of frosting.However,the heating power and COP(coefficient of performance)of the system declines slightly.Considering the operation stability and thermal performance simultaneously,the suitable temperature of mixing water for this system is 12-18℃ when ambient temperature is -20℃ and heating temperature is 60℃.

The preparation of nano nickel powder by solution reduction method in stirred reactor was proposed.The effects of different operating conditions including reactant concentration,reactant ratio,initiator concentration,sodium hydroxide concentration,reaction temperature,stirring speed on the characteristic of nano nickel powder were systematically investigated to obtain the optimal operating conditions.Nano nickel powder with a face centered cubic structure and an average particle size of 107 nm was obtained under the optimal operating conditions of a NiSO₄ concentration of 0.8 mol·L^-1,a reactant ratio(N₂H₄:NiSO₄) of 6:1,a initiator concentration of 0.01 mol·L^-1,sodium hydroxide concentration of 1 mol·L^-1,a reaction temperature of 80℃,a stirring speed of 2400 r·min^-1.

Most phase change materials have the problem of supercooling,which affects the wide use of phase change materials.Therefore,it is very important to figure out the temperature variations during the solidifying process of phase change material.The numerical model of step cooling process of phase change material was built based on the lumped parameter method and the effective heat capacity method,and the model was verified by the experimental results.Meanwhile,the influences of the supercooling degree and the amount of latent heat of the phase change material on its temperature during the solidifying process were studied.It was found that the starting solidifying time of the phase change material and the total time of solidifying process both had the exponential relationship with the supercooling degree.The starting solidifying time was delayed with the increase of the supercooling degree,and the total time of solidifying process was decreased with the increase of the supercooling degree.The amount of latent heat had no influence on the starting solidifying time,but there was a linear relationship between the amount of latent heat and the total time of solidifying process.