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[en] Highlights: • Typical lithium chloride liquid desiccants were concerned. • Up to date heat capacity data of high quality were measured. • Scanning calorimetry technology was applied. • A universal empirical formula was correlated for the heat capacity of solutions. -- Abstract: Three kinds of lithium chloride desiccants were selected, which are considered to be potential and interesting working fluids for a desiccant/dehumidification or absorption refrigeration system, and their isobaric specific heat capacities were determined in this context. Experiments were conducted at a high accuracy twin-cell scanning calorimeter. The temperature accuracy and heat flux resolution of the calorimeter are ±0.05 K and 0.1 μW respectively. The data of lithium chloride + water and lithium chloride + triethylene glycol (TEG)/propylene glycol (PG) + water systems were achieved at temperatures from 308.15 K to 343.15 K and atmospheric pressure. The mass fraction of LiCl ranged from 15% to 45% in the LiCl + H2O system, and the mass fraction of LiCl and glycol ranged from 10% to 23.3% and 20% to 46.7% in the ternary systems respectively. Based on the experimental heat capacity data, a universal empirical formula was correlated as a function of temperature and solute mass fraction. In the experimental mass fractions and temperatures range, the average absolute deviation (AAD) between experiment results and calculated values is no more than 0.15%, and maximum absolute deviation (MAD) is within 0.38%. These thermodynamic data of lithium chloride solutions can be effectively used for analysis and design of desiccant/dehumidification systems and absorption refrigeration systems in both refrigeration and chemical industry
[en] Highlights: • A new absorption chiller utilizing heat with a large temperature glide is proposed. • Thermodynamic calculations are conducted to analyze the system performance. • Steady-state parametric studies are conducted for this system. • ω of the new cycle is much higher than that of a single effect cycle. • The new cycle can obtain lower temperature and use lower grade heat. - Abstract: To make full utilization of waste heat with large temperature glide, a new absorption refrigeration cycle with a simple construction is proposed. In this cycle, the solution flowing out from a low-pressure and high-temperature absorber absorbs refrigerant vapor in a low-pressure and low-temperature absorber which is cooled by evaporating refrigerant in a high-pressure evaporator. The refrigerant vapor to be absorbed in the low-pressure and low-temperature absorber comes from a low-pressure evaporator. The vapor flowing out from the high-pressure evaporator is absorbed by solution in a high-pressure absorber. This solution sent to a liquid pump comes from a low-pressure and low-temperature absorber. Compared to a single-effect absorption cycle, the molar fraction of refrigerant of the solution into generator is much greater, resulting in drastic temperature decline for the displaced exhaust gas/water of this cycle, which means the new cycle can effectively utilize waste heat with large temperature glide. Theoretical simulation results show that the cooling capacity per unit mass of exhaust gas of the proposed cycle is about 20% higher than that of a single-effect absorption cycle, especially for the situation that temperature of supplied waste heat is lower and/or refrigeration temperature is lower.
[en] This paper presents a novel absorption–compression cascade refrigeration system, which can reach an evaporating temperature of −170 °C. In the cascade system, the refrigerant of compression subsystem (CS) is subcooled by the refrigerant of low-grade heat driven absorption subsystem (AS) to reduce the electric power consumption. Theoretical and experimental investigations were carried out over the CS evaporating temperature ranging from −100 to −170 °C and operating parameters were given. At the CS evaporating temperature of −170 °C, when AS provided a low-grade cooling capacity of 164.8 W to CS, a decrease of 2.5 °C in CS evaporating temperature or an increase of 32.3 W in high-grade cooling capacity of CS were observed. Meanwhile, in CS, the discharge temperature and pressure decreased, while the suction pressure increased. These beneficial results not only verified the feasibility of the system, but also revealed the application potential of the system in the future. - Highlights: • A low-temperature absorption–compression cascade refrigeration system is presented. • Thermodynamic calculations are conducted to analyze the system performance. • An experimental rig is developed and experimental investigations are carried out. • Dynamic and steady-state parametric studies are conducted for this system
[en] Initiating events at nuclear power plants such as human errors or components failures may lead to a nuclear accident. The study of the frequency of these events or the distribution of the failure rate is necessary in probabilistic risk assessment for nuclear power plants. This paper presents Bayesian modelling methods for the analysis of the distribution of the failure rate. The method can also be utilized in other related fields especially where the data is sparse. An application of the Bayesian modelling in the analysis of distribution of the time to recover Loss of Off-Site Power ( LOSP) is discussed in the paper
[en] Objective: To investigate whether recombinant human endostatin can create a time window of vascular normalization prior to vascular pruning to alleviate hypoxia in Lewis lung carcinoma in mice. Methods: Kinetic changes in morphology of tumor vasculature in response to recombinant human endostatin were detected under a confocal microscope with immunofluorescent staining in Lewis lung carcinomas in mice. The hypoxic cell fraction of different time was assessed with immunohistochemical staining . Effects on tumor growth were monitored as indicated in the growth curve of tumors . Results: Compared with the control group vascularity of the tumors was reduced over time by recombinant human endostatin treatment and significantly regressed for 9 days. During the treatment, pericyte coverage increased at day 3, increased markedly at day 5, and fell again at day 7. The vascular basement membrane was thin and closely associated with endothelial cells after recombinant human endostatin treatment, but appeared thickened, loosely associated with endothelial cells in control tumors. The decrease in hypoxic cell fraction at day 5 after treatment was also found. Tumor growth was not accelerated 5 days after recombinant human endostatin treatment. Conclusions: Recombinant human endostatin can normalize tumor vasculature within day 3 to 7, leading to improved tumor oxygenation. The results provide important experimental basis for combining recombinant human endostatin with radiation therapy in human tumors. (authors)
[en] Highlights: • Isobaric heat capacity for compressed liquid R245fa and R236fa were measured. • Experimental data was correlated to an empirical equation. • Comparison was carried out between present data and latest equation of states. - Abstract: Isobaric heat capacities of compressed liquid 1,1,1,3,3-pentafluoropropane (R245fa) and 1,1,1,3,3,3-hexafluoropropane (R236fa) were measured by scanning calorimetry. The experimental system basically consists of a calvet calorimeter (Setaram C80) and a pressure balance unit. A total of 55 data points for liquid R245fa and 52 data points for liquid R236fa were obtained at temperatures from (315 to 365) K and pressures up to 5.5 MPa. The uncertainties for the heat capacity of R245fa and R236fa were estimated to be (1.8 and 1.6)%, respectively. The experimental data was correlated to an empirical equation, the form of which was decided by stepwise fit method. The average absolute percentage deviations between the data points and the equation were (0.23 and 0.10)% for R245fa and R236fa
[en] Highlights: •Application of heat driven refrigeration systems to fishing vessel is reviewed. •Techniques for improving efficiency and stability for onboard application are detailed. •In addition to three basic types of systems, hybrid system is also introduced. •An overall table to summarize and compare the features of various systems is provided. -- Abstract: For a fishing vessel, its diesel engine’s energy efficiency is only at 35–40%, with more than half of the energy being wasted as exhaust heat taken away by jacket water, cooling air and exhaust gas. Fishing vessel refrigeration systems driven by the exhaust heat from engines can therefore help achieve energy saving. However, to improve the COP/EER of these heat driven refrigeration systems and to ensure their operational stability under severe conditions on ocean are of challenges. In this paper, the progress and prospect of utilizing three different kinds of heat driven fishing vessel refrigeration systems, i.e., adsorption refrigeration system, absorption refrigeration system and ejection refrigeration system, are reviewed with a special focus on the techniques for improving system efficiency and stability. A hybrid heat driven refrigeration system, which combines merits of different types of systems, is then introduced. A summary table is provided to summarize and compare the features of adsorption refrigeration systems, absorption refrigeration systems and ejection refrigeration systems used in fishing vessels, followed by conclusions and suggestions for future works.
[en] To increase the use efficiency of available thermal energy in the waste gas/water, a novel high-efficient absorption refrigeration cycle regarded as an improved single-effect/double-lift configuration is proposed. The improved cycle using an evaporator/absorber (E/A) promotes the coefficient of performance and reduces the irreversible loss. Water–lithium bromide is used as the working pair and a simulation study under the steady working conditions is conducted. The results show that the temperature of waste gas discharged is about 20 °C lower than that of the conventional single-effect cycle and the novel cycle we proposed can achieve more cooling capacity per unit mass of waste gas/water at the simulated working conditions. -- Graphical abstract: Pressure – temperature diagram for water – lithium bromide. Highlights: ► A novel waste heat-driven absorption refrigeration cycle is presented. ► The novel cycle can reject heat at much lower temperature. ► The available temperature range of heat source of the proposed cycle is wider. ► Multiple heat sources with different temperatures can be used in the novel cycle
[en] Highlights: • Multi-heat driven absorption chiller experimental rig was tested. • Simulated solar heat at 80 °C works as secondary heat source. • The system’s external parameters were experimentally studied. • A similar COP with double-effect cycle, with lower driven temperature. - Abstract: This paper proposes a new ejector-absorption refrigeration cycle driven by two heat sources at different temperature levels to realize the economic optimization in low-grade heat recovery application. The cycle uses the exergy of steam from a high-pressure generator and entrains the steam out of a low-pressure generator. The quantity of the steam that comes out of the low-pressure generator for the new cycle is greater than that of a conventional double-effect cycle, which means that more low-temperature-level heat, such as non-focused solar thermal heat, can be used. Therefore, the heat required to input into the system and the temperature level required to drive the cycle declines. In this study, water-lithium bromide as the working pair and a hot air temperature level ranging from 185 °C to 215 °C is used as the high level driving heat source, while the hot water heated by a solar energy collector is the low level driving heat source. In some conditions of the new cycle’s COP, 0.95 can be achieved for refrigeration, which is about 20% higher than that of the single-effect cycle. Besides this, the proposed chiller requires lower driven temperature than that of a conventional double-effect cycle.
[en] Highlights: • A new open absorption heat pump system was proposed. • The new system aims at recovering latent heat from low-temperature moist gas. • The new system can utilize a lower temperature range of heat source. • COP_h and heat recovery efficiency is high with the production of high-temperature steam. • Increasing generation temperature and humidity of gas is beneficial for the new system. - Abstract: Conventional drying processes discharge high humidity gas to the atmosphere. The exhaust gas contains large amount of energy. The direct discharging would result in relatively large energy waste. In order to improve the thermal efficiency of drying process, in this paper, a new open absorption heat pump system was proposed, which aims at recovering the latent heat from exhausted moist gas and producing steam for reutilization. The working principle was discussed in detail and thermodynamic models were established to analyze the performance of the new system. The new system can work under both single-stage and double-stage modes. Simulation results showed that the new system could utilize a heat source with lower generation temperature compared with that utilized by a traditional open absorption system. The temperature range of heat source for the double-stage mode is 130–160 °C, and that for the single-stage mode is 160–175 °C. The new system also eliminates the limitation of traditional close absorption system, whose evaporation temperature has to be lower than the dew point temperature of discharged moist gas to recover the latent heat of water steam. Simulation results also indicated an improved COP_h of the new system compared with that of double-stage close absorption heat pump system. The COP_h of the new system varied from 1.52 to 1.97 and the efficiency of heat recovery varied from 15.1% to 54.8% when the temperature of heat source varied from 135 °C to 175 °C and saturated steam of 100 °C was produced