Experimental evaluation of a variable effect LiBr–water absorption chiller designed for high-efficient solar cooling system

A variable effect LiBr–water absorption chiller is studied in this paper based on a real developed 50 kW prototype. The chiller is designed specifically for the high-efficient utilization of the solar power with variable temperature. It can obtain the optimized COP and cooling power under different heat source temperatures. The construction, circulation and testing system of the chiller were introduced. A typical running condition of the chiller from the starting to the steady operating was given to show the dynamic performance. Several groups of the temperatures and COPs were given to show the steady state performance. These data showed that the COP increased from 0.69 to 1.08 under generation temperature from 95 °C to 120 °C. Besides, the effects of chilled water temperature, cooling water temperature, pump frequency and opening of valve on COP and cooling power were analyzed respectively.     

Experimental investigation on the performance of a solar powered lithium bromide–water absorption cooling system

The performance of solar cooling absorption system needs further research, due to its poor coefficient of performance (COP). Therefore, this study investigated the performance of a 23 kW solar powered single-effect lithium bromide–water (LiBr–H₂O) absorption cooling system. Furthermore, the space heating mode was also investigated and the improvement methods were analyzed and discussed. The cooling system was driven by a parabolic trough collector of 56 m² aperture area and used for cooling a 102 m² meeting room. Research results revealed that the chiller's maximum instantaneous refrigeration coefficient (chiller efficiency) could be up to 0.6. Most of the time, in sunny and clear sky days the daily solar heat fraction ranged from 0.33 to 0.41 and the collectors field efficiency ranged from 0.35 to 0.45. At the same time, chiller efficiency was varied from 0.25 to 0.7 and the daily cooling COP was varied from 0.11 to 0.27, respectively.     

Energy consumption of cold climate heat pumps in different climates – Comparison of single-stage and two-stage systems

The aim of the study presented in this paper is the comparison of different possibilities to reduce the power consumption and environmental impact of barrack buildings of the US army. For this purpose different building standards, different heating and cooling appliances and a cold storage concept are compared using annual building simulations. These simulations are carried out for central and northern locations in the US. The focus of this paper is the applicability of cold climate heat pumps in these climates. A coupled building and appliance model has been established to allow a fair comparison based on first energy usage and CO₂ emissions. Altogether seven different building configurations in six different locations have been investigated. Simulation results show the most significant energy savings (up to 90%) can be achieved by improving building insulation and heat recovery of the ventilation system. Second major improvement is the usage of two-stage heat pump systems, which drastically reduces the need for backup heating systems and lead to seasonal efficiencies (SCOPs) in the area of 3.0, or in other words an energy saving of 20–35%. Thermal storage and control concepts such as night setback in comparison show little effect. The simulation results also showed that primary energy demand or greenhouse gas emissions are better measures for the comparison of environmental impact than COP and SCOP.     

Theoretical evaluation of equilibrium partition coefficients of solute elements in Fe–C–base quaternary and muIticomponent systems

Abstract

The coefficients of equilibrium partition of solute elements between austenite and liquid iron were evaluated thermodynamically for Fe–C–base quaternary systems. The validity of the calculation was examined in comparison with the measured coefficients of solute elements in some quaternary systems. The equilibrium partition coefficient of the third element i in an Fe–C–base quaternary system is affected by two factors: the effects of the fourth element j on the interaction between carbon and the third element and the interaction between the third and fourth elements. Most of the combinations of the third and fourth elements in Fe–C–i–j quaternary systems showed a relatively small interaction between the elements i and j except the combination of chromium and titanium, which exhibited an explicit influence of titanium on the partition coefficient of chromium. It was concluded that the partition coefficients in Fe–C–base multicomponent systems differed little from those in Fe–C–base ternary systems, with a few exceptions.

MST/220     

Synthesis of bridged β-cyclodextrin–polyethylene glycol and evaluation of its inhibition performance in oilfield wastewater

The bridged β-cyclodextrin–polyethylene glycol (β-CD–PEG) is synthesized through reaction of β-CD with PEG, which has been characterized by Fourier transform infrared spectroscope. The inhibition efficiency of bridged β-CD–PEG on corrosion of Q235 carbon steel in 0.5 M HCl solution has been investigated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and weight loss measurements. The results show that β-CD–PEG acted as a mixed-type inhibitor and performed excellent inhibiting effect for the corrosion of the Q235 carbon steel. The steel surface morphologies are analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) and then an adsorption mechanism model is proposed. The high inhibitory efficiency of β-CD–PEG is related with the adsorption of polymer molecules at the steel surface and a protective film formation. Finally, these results present a novel corrosion inhibitor works in oil-gas field.     

Enhancement of heat transfer by water–Al2O3 and water–TiO2 nanofluids jet impingement in cooling hot steel surface

Two different nanofluids, namely water–Al₂O₃ and water–TiO₂, were impinged in the form of jet on hot steel surface to remove high heat flux, and their performance was compared. The dimension of the test steel sample was 120 mm × 120 mm and 4 mm thickness. Four K-type thermocouples were embedded on the bottom surface of the plate to measure the transient temperature distribution. The time-temperature data were recorded by the help of a data acquisition system (make: CHINO, model: KR2000), and the results were analysed by ZAILA application software. Effect of impinging nanofluids with weight concentrations of 0.01%, 0.03%, 0.05% and 0.07% Al₂O₃ and TiO₂ nanoparticles on heat transfer from the hot surface was tested. The surface heat transfer coefficient (HTC) was computed from the time-temperature history recorded during experimentation. Experimental results revealed that addition of nanoparticles to the base fluid (water) surprisingly enhanced the heat transfer rate and HTC as expected. The heat transfer rate increased up to certain limit of nanoparticle concentrations, and then declined. Application of nanofluids for the steel strip cooling was found very effective in terms of heat transfer phenomena as compared to the conventional fluid cooling methods.     

Design,construction and operation of a solar powered ammonia–water absorption refrigeration system in Saudi Arabia

This study presents an experimental investigation of a solar thermal powered ammonia–water absorption refrigeration system. The focus of this study lies on the design of the components of the absorption chiller, the ice storages and the solar collector field as well as the integration of the data acquisition and control unit. An ammonia–water (NH₃/H₂O) absorption chiller was developed in the laboratory of the Institute of Thermodynamics & Thermal Engineering (ITW) at the University of Stuttgart (Germany). A demonstration plant was built in the laboratory of the CoRE-RE at King Fahd University of Petroleum & Minerals (KFUPM – Saudi Arabia). The whole system was tested successfully. The results of the experiments indicated a chiller coefficient of performance (COP) of 0.69 and a cooling capacity of 10.1 kW at 114/23/−2 (°C) representing the temperatures of the generator inlet, the condenser/absorber inlet and the evaporator outlet respectively. Even at 140/45/−4 (°C), the chiller was running with a cooling capacity of 4.5 kW and a COP of 0.42.     

Numerical study of solid–liquid two-phase flow and erosion in ball valves with different openings

In the coal chemical industry, petrochemical industry, and other industries, ball valve is a common and important valve due to its reliable structure. The conveying medium has particles that affect the valve surface under the drive of water flow, thereby making the ball valve face the risk of erosion and damage. In this study, the CFD-DEM method was adopted to study the influence of different openings and particle diameters on the two-phase flow and erosion characteristics inside the ball valve. The two-phase flow and particle distribution of the ball valve were analyzed, and the main erosion wall surfaces were determined. The erosion distribution of these walls was obtained. The variation rule of particle number with erosion rate was analyzed, which shows that particle number played a dominant role in erosion degree. Result also showed that in the case of small opening, the erosion decreased with the increase in particle diameter.     

Hydraulic design and operation of variable-speed pumps as the water–energy saving strategies in pressurized irrigation systems

Clean Technologies and Environmental Policy - Low efficiencies of irrigation pumping stations usually stem from their improper designing, operation, and maintenance of such systems. In the present...     

Cyclic behavior of 9–12% Cr steel under different control modes in low cycle regime: A comparative study

Cyclic behavior of 9–12% Cr steel under both stress and strain control modes was investigated at 873 K. Significant asymmetric deformation and cyclic softening were observed for both modes. Under the strain-controlled fatigue, a strain level-independent softening factor (SF) was observed. The SF was dependent on applied stress under the stress-controlled fatigue. For the strain-controlled fatigue, the magnitude of cyclic asymmetry decreases with the increase of strain amplitude, while under the stress-controlled fatigue, the asymmetry increases with the increase of stress amplitude. The anomalous ratcheting strain resulted from the asymmetry under the stress-controlled mode has a detrimental effect on fatigue life.     

Enhanced water resistance and energy performance of core–shell aluminum nanoparticles via in situ grafting of energetic glycidyl azide polymer

The application of aluminum nanoparticle is limited due to its passivation Al₂O₃ layer even though it owns extreme specific surface and high reaction activity. In this work, the aluminum nanoparticles were modified via in situ grafting onto energetic glycidyl azide polymer (GAP) to improve the stability and energy-releasing performance. The results showed that GAP was grafted on the nano-aluminum surface with chemical bonds of –O–(CO–NH)– formed, and the thickness of shell layer of GAP could be tuned by changing the relative ratio of reactants. Furthermore, modified nanoparticles show hydrophobicity with static water contact angle changing from 20.2° to 142.4°. Significant increasing stability of aluminum nanoparticles is obtained in hot water, which is evidenced by that around 10 wt% of modified aluminum is reacted after 210 min. Based on the core–shell configurations, (Al@GAP)/fluorine composites were prepared. The violent combustion phenomenon and high release rate profiles revealed high energy-releasing performance with the assistance of GAP. This synthetic strategy may provide an effective approach to prepare other metal nanoparticles, and possess potential application value in the fields of metallized explosives and high-energy structure with energy release.     

Role of MnO in manganese–borate binary glass systems: a study on structure and thermal properties

Structural and thermal properties of \(x\hbox {MnO}-(100-x)\hbox {B}_{2}\hbox {O}_{3}\) (where \(x=40\), 50 and 60 mol%) glass samples have been investigated with the employment of various techniques. Fourier transform infrared spectroscopy results revealed the influence of MnO on glass matrix. Decrease of B–O bond-related band intensities has been observed. MnO addition was found to introduce broken [\(\hbox {BO}_{2}\hbox {O}^{-}\)]\(_{{n}}\) chains. Differential scanning calorimetry (DSC) measurements presented decreasing \(T_{\mathrm{g}}\) that indicates depolymerization of glass matrix in the considered compositional range. Moreover, thermal stability (TS) parameter has been evaluated using the DSC technique. It slightly decreased with MnO content. X-ray photoelectron spectroscopy results provided the evidence for \(\hbox {Mn}^{2+}\) and \(\hbox {Mn}^{3+}\) presence. Multiplet splitting, close to that of MnO, has been observed. It has been concluded that most of the manganese ions existed in the divalent state. Photoluminescence study revealed that manganese ions are tetragonally co-ordinated in a glassy matrix.     

A comparative study of research performance in nanotechnology for China’s inventor–authors and their non-inventing peers

This paper explores the relationship between patenting and publishing in the field of nanotechnology for Chinese universities. With their growing patents, Chinese universities are becoming main technological source for nanotechnology development that is extremely important in China. Matching names of patentees to names of research paper authors in Chinese universities, we find 6,321 authors with patents, i.e. inventor–authors, and 65,001 without any patent. Research performance is measured using three indicators—publication counts, total citations and h-index received by each researcher. It is found that research performance of authors who are also inventors holding patents is better than that of those authors who do not have a patent, and that most of high quality research is performed by inventor–authors. Our findings indicate that patent-oriented research may produce better results.     

Effect of different concentration Li-doping on the morphology,defect and photovoltaic performance of Li–ZnO nanofibers in the dye-sensitized solar cells

Low concentrations of Li in Li-doped ZnO nanofibers prepared using hydrothermal method at low temperature can introduce oxygen vacancies and intrinsic Zn ions into the structure. Photo-luminance (PL) was used to investigate oxygen vacancies in the structure of ZnO nanofibers prepared by lower annealing temperature, and the XPS technique was also employed to satisfy the PL analysis results. PL analysis showed that oxygen vacancies increase in conjunction with Li concentrations. A shift in the lower angle of XRD patterns also demonstrates the defect in ZnO structure related to Li doping. Higher-efficiency DSSCs were obtained from the lower Li concentration of 0.01 M in ZnO nanofibers. Higher concentrations of Li tended to produce large amounts of cross-like nanofibers, which increase the open circuit voltage of the DSSCs. The highest open circuit voltage (V_oc) obtained was 750 mV, which was higher than the best reported ZnO nanofibers-based DSSCs. Intensity modulation photocurrent spectroscopy (IMPS) and intensity modulation photo-voltage spectroscopy (IMVS) analysis showed that low amounts of Li-doping improved the electron injection efficiency of ZnO nanofibers in DSSCs. Lower recombination rates with higher electron transfer efficiency for 0.01 M Li-doped DSSCs exhibited higher efficiency of 0.59% than non-doped ZnO nanofibers DSSCs.     

Numerical and experimental investigations of the effects of the breakup of oil droplets on the performance of oil–gas cyclone separators in oil-injected compressor systems

A numerical simulation was conducted of the dynamic trajectories and the separation performance of oil droplets, with a focus on the breakup of oil droplets in an oil–gas cyclone separator. The separation efficiency was also studied experimentally, and the oil droplets' diameter distributions before and after the separator were measured with a Malvern particle size analyser to verify the simulation model. Both the experimental and simulation results showed that the breakup of oil droplets occurred in the separation process, clearly influencing the separation efficiency. In addition, the results indicated that inlet velocity played an important role in separation efficiency, as it not only significantly affected the tangential velocity inside the separator, but also determined the possibility and degree of the breakup of oil droplets.     

In vitro and in vivo performance of Ti6Al4V implants with plasma-sprayed osteoconductive hydroxylapatite–bioinert titania bond coat “duplex” systems: an experimental study in sheep

To evaluate the in vivo performance of "duplex" hydroxylapatite top coat/TiO(2) bond coat systems, cylindrical Ti6Al4V rods of 130 mm in length and 11-13 mm in diameter were coated by atmospheric plasma spray (APS) technique with both a standard hydroxylapatite (HAp) layer and a HAp+TiO(2) bond coat "duplex" layer. In this pilot study coated and uncoated rods serving as controls were implanted into the femur of sheep so that their distal ends were freely suspended in the medulla of the femur. After an observation time of six months it was found that bone apposition and bone ingrowth were considerably increased in the presence of a osteoconductive coating. In particular, in vivo spalling and delamination frequently observed with HAp coatings was virtually absent in duplex coatings owing to the strong adhesion of the bond coat to the HAp top coat that anchored the latter solidly to the metallic surface of the implant. Some tentative mechanisms leading to this improved coating adhesion will be discussed.     

Effects of La3+ or Ti4+ doping on dielectric and microwave absorption performance of CaMnO3 in the 8.2–18 GHz

In this paper, CaMnO₃ and Ca_0.97La (or Ti)_0.03MnO₃ powders were synthesized using mechanical ball milling technique and sintered at 1100°C for 12 h in an air atmosphere. Results showed that all the samples are single phase with an orthorhombic symmetry. Compared with the pure CaMnO₃ sample, the Ca_0.97La_0.03MnO₃ and Ca_0.97Ti_0.03MnO₃ samples have higher complex permittivity and better microwave absorbing properties. These changes are caused by the doping-ion incorporating in CaMnO₃ lattice and Ca vacancies, which could result in abundant dipoles and the local charge accumulation. The Ca_0.97Ti_0.03MnO₃ sample exhibited the best microwave absorption performance, i.e. the minimum reflection loss was -46.9 dB with a matching thickness of 2.2 mm and effective absorption bandwidth reached 5.2 GHz with a thickness of only 1.8 mm. This study demonstrates that the CaMnO₃ would be a potential material in the microwave absorbing field and needs further research.