Discharging Temperature Research Articles

Manufacturing and performance of eco-efficient cementitious blocks for thermal cycling in thermal energy storage

Solar energy is a promising renewable option to provide energy demands in combination with conventional energy sources. However, to enhance the integration of renewable energies into the industrial section, it is necessary to employ thermal energy storage media. Among different thermal energy storage options, concrete has proven to be a very effective sensible thermal energy storage solution. However, its main raw material (i.e., the Portland cement), is the cause of huge CO2 emissions to the environment. This study focuses on the design, manufacture, assembly and experimentation of thermal energy storage blocks made of alternative binders in substitution of Portland cement: i.e., hybrid materials and alkaline activated materials. The thermal energy storage blocks have been thermally cycled, with a charging temperature of 228 °C and a discharging temperature of 30 °C, in order to analyze the operational times and temperatures. The results obtained are very promising and comparable to those of the Portland cement system. Charging times have improved, with the alternative materials achieving temperature increases of up to 4%, while greater stabilization has been achieved during discharge, with the fluid reaching temperatures up to 6% higher than the reference system. These advancements support efficient, sustainable thermal energy storage technologies.

EXPERIMENTAL STUDIES ON Li-ION BATTERY PACK FOR TEMPERATURE DISTRIBUTION ANALYSIS DURING FAST DISCHARGING AND VARIOUS AMBIENT TEMPERATURE CONDITIONS

Lithium-ion batteries are the primary energy source for electric vehicles (EVs), which were developed to address environmental issues and the lack of energy resources. The temperature is a key factor in Li-ion batteries which affects their degradation and life span. In this study, the thermal performance characteristics of a 4S2P Li-ion battery pack are analyzed according to the change in the environmental temperatures of 25°C, 40°C, and 60°C and the discharge rates of 0.5C, 1C, 2C, and 3C of the battery. In the experiment, the maximum temperature rises in the battery pack at 0.5C discharge rate is within the optimum operation range with respect to all tested ambient temperature conditions. Meanwhile, it is higher at an ambient temperature of 25°C than at ambient temperatures of 40°C and 60°C during high-current discharge (1C, 2C, and 3C) operations. The results prove that the environmental temperature of 40°C provides better thermal performance than 25°C and 60°C operating levels. Also, the temperature distribution between neighboring cells in the pack increases as the C-rate increases from 0.5C to 3C, and this nonuniformity causing high heat generation can lead to a performance reduction of the module. This article primarily proposed a correlation between heat transfer and ambient temperatures in terms of discharge rate. The correlation is significant when designing thermal management systems for battery-powered devices.

Theoretical Study and Experimental Validation on the Applicable Refrigerant for Space Heating Air Source Heat Pump

The air source heat pump (ASHP) is developing rapidly and is widely used for space heating due to its potential for increasing energy efficiency and reducing greenhouse gas emissions. The choice of appropriate low global warming potential (GWP) alternative refrigerants is one of the challenges that ASHP systems face. Alternative refrigerants also affect the energy performance of these systems. Thus, it is essential to evaluate the performance of ASHP using environmentally friendly refrigerants to facilitate reasonable refrigerant selection. A theoretical model for simulating ASHP performance with different refrigerants is developed in this study. Experiments are conducted to validate the theoretical model. The simulation and the experimental results are found to be in good agreement. The ASHP performance indices, such as compression ratio (CR), discharging temperature (DT) and coefficients of performance (COP), are investigated using R22, R417A, R410A, R134a, R152a, R161 and R1234yf as working fluids. The results show that R152a has an average COP of 2.7% higher than R22, and R161 has an average COP of 1.4% higher than R22. R152a and R161 also have a higher CR but a lower DT than R22 under the same design conditions. In addition, R152a and R161 have ozone depletion potentials (ODP) of zero and extremely low GWPs; thus, they can be candidates to replace R22 in ASHP heating systems. This research provides a reference on refrigerant replacements for ASHP heating systems in North China.

Optimizing the discharge process of a seasonal sorption storage system by means of design and control approach

Sorption thermal energy storage systems have higher energy densities and low long-term thermal losses compared to traditional energy storage technologies, which makes them very attractive for seasonal heat storage application. Although they have a lot of potential at material level, its operation and system implementation for residential application requires further study. The performance of a seasonal sorption thermal energy storage system strongly depends on the discharging process during the cold season. The present study analysed through numerical simulations different scenarios to enhance the thermal performance of a solar-driven seasonal water-based sorption storage, which supplied space heating and domestic hot water to a single-family house in a cold climate region. All studied scenarios were analysed under optimal control policy. The results indicated that the sorption storage could increase by 9 % its energy density if conservative and constant discharging temperature set points are considered, due to fewer interruptions during the discharge. The energy density of the sorption storage driven by solar energy was highly impacted by the weather conditions, and by the type and availability of low-temperature heat source. Indeed, the energy density of the sorption storage increased by 22 % using a water tank to assist the evaporator of the sorption storage, instead of a latent storage tank. The use of a dry-heater to assist the evaporator with environmental heat was not suitable for the climate studied due to the low hours of operation. The sorption storage system composed of 20 modules of LiCl-silica gel could obtain an energy density and a COP of 139 kWh/m3 and 0.39, respectively, if a constant low-temperature heat source (i.e, geothermal or waste energy) was available.

Remaining Useful Life Prediction for Lithium-Ion Batteries Based on the Partial Voltage and Temperature

Remaining useful life (RUL) prediction is vital to provide accurate decision support for a safe power system. In order to solve capacity measurement difficulties and provide a precise and credible RUL prediction for lithium-ion batteries, two health indicators (HIs), the discharging voltage difference of an equal time interval (DVDETI) and the discharging temperature difference of an equal time interval (DTDETI), are extracted from the partial discharging voltage and temperature. Box-Cox transformation, which is data processing, is used to improve the relation grade of HIs. In addition, the Pearson correlation is employed to evaluate the relationship degree between HIs and capacity. On this basis, a local Gaussian function and a global sigmoid function are utilized to improve the multi-kernel relevance vector machine (MKRVM), whose weights are optimized by applying a whale optimization algorithm (WOA). The availability of the extracted HIs as well as the accuracy of the RUL prediction are verified with the battery data from NASA.

Performance prediction and optimization of a three-layer thermocline tank using the response surface method

The majority of prior experimental and computational studies of the energy tank system employed in solar power plant systems have been focused on parametric studies. The interaction effects of several input factors on the thermal behavior of the TTES tank configuration using RSM have not yet been addressed. A predictive approach depending on the response surface method (RSM) is built in this work to demonstrate the link between the independent and dependent parameters of the thermocline storage tank structure. The two-phase dispersion-concentric numerical model equations were calculated and solved using MATLAB software. RSM is used for both single and multi-objective optimization to suggest appropriate control parameters for various optimization purposes. Four response factors are considered: charging/discharging time, efficiency, and recovered energy. The analysis of variance check and perturbation assessment is as well used to assess the model's appropriateness and statistical significance. Based on the findings, it is recommended to choose a capsule diameter of 0.015 m, a charging cycle inlet temperature of 400°C, a discharging cycle inlet temperature of 250°C, and a molten salt mass flow rate of 100 kg/s to minimize charging and discharging time while also maximizing overall efficiency and recovered energy.

Sorption based long-term thermal energy storage with strontium chloride/ammonia

Thermal energy storage takes a pivotal role in the renewable energy application and waste heat recovery through adjusting the instability and discrepancy between energy supply and demand. For the purpose of the long-duration storage application based on thermochemical sorption, SrCl2 composite materials were prepared and a demonstrative prototype has been constructed. The long-duration storage capacity of thermochemical sorption heat storage was investigated with SrCl2/NH3 as the working pair. The experimental results show that the maximum heat storage density of SrCl2/NH3 thermochemical sorption heat storage system is about 1630.8 kJ kg−1 SrCl2 (or 1386.2 kJ kg−1 composite sorbent) under the operation condition of the charging temperature of 92 °C, the condensation/evaporation temperature of −5 °C and the discharging temperature of 40 °C. The heat storage efficiency of thermochemical sorption system decreases when the discharging temperature increases, whilst the coefficient of performance is raised with the increasing discharging temperature. Under the experimental conditions, the highest values of sorption heat storage efficiency and coefficient of performance are 0.687 and 0.405, respectively. Experimental results reveal that the thermochemical sorption heat storage is an effective method for the long-duration heat storage applications. It can facilitate the large-scale solar thermal energy harvesting and the industrial waste heat recovery.

Experimental investigation on discharging characteristics of supercooled CH3COONa·3H2O-Na2S2O3·5H2O mixtures triggered by local cooling with Peltier effect

Latent heat stored in the supercooled salt hydrate liquid can be released at the desired time by triggered crystallization. In this paper, the melted sodium acetate trihydrate (SAT, melting point Tm = 55.7 °C) and sodium thiosulfate pentahydrate (STP, Tm = 48.9 °C) are cooled by natural convection of room air with respective supercooling degrees of 33 °C and 28 °C. Experiments are performed on the effect of local cooling by semiconductor refrigerator on triggering crystallization of supercooled SAT, STP and their binary mixtures with different mass ratios. The results show that SAT has higher discharging temperature and longer discharging time than STP; but STP has less phase separation, better cycling stability and shorter induction period during the crystallization than SAT after repeated melting-freezing cycles. Moreover, the phase separation problem of SAT could be significantly alleviated with the addition of STP. With the increase of SAT content in the SAT-STP mixtures, the induction period during the crystallization tends to firstly increase and then decrease. The tested curve of the maximum discharging temperatures presents as a V-shaped trend and roughly corresponds with the binary phase diagram. The eutectic mixture of SAT-STP (mSAT:mSTP = 28:72, the eutectic temperature of 40.8 °C) can be triggered in 4 min and shows a discharging temperature peak measured at 39 °C. The discharging time of 3.3 h with temperature above 30 °C is longer than that of single-component salt hydrates. The obtained results are helpful for system design and practical application of solar energy storage based on supercooled phase change materials.

Double-effect/two-stage compression-assisted absorption thermal energy storage using LiNO3-ionic liquids/H2O working fluids

A novel double-effect/two-stage compression-assisted absorption thermal energy storage system using LiNO3-[BMIM] (1-butyl-3-methylimidazolium) NO3/H2O for combined cooling and heating is proposed to enhance thermal performance under a larger concentration glide without crystallization. The thermodynamic calculation is conducted by Matlab based on the measured thermophysical properties, and its performance is compared with that of a system using other working fluids. The results show that this proposed system using LiNO3-ionic liquids/H2O with compressor assistance achieves a higher coefficient of performance and energy storage density at a larger concentration glide without crystallization. In comparison to LiBr/H2O, the generation temperature of this system using LiNO3-ionic liquids/H2O is reduced by over 50 K at a larger concentration f, which is beneficial for the utilization of solar energy. As the discharging temperature increases from 321.15 K to 333.15 K and f from 0.08 to 0.20, this novel system using LiNO3-[BMIM]NO3/H2O obtains the largest coefficient of performance of 1.36 and exergetic coefficient of performance of 0.46 at generation temperature below 354.2 K, compared to LiNO3/H2O and LiNO3-[DMIM][DMP]/H2O. Moreover, the maximum energy storage density based on LiNO3-[BMIM]NO3/H2O reaches 695.4 kJ/kg at a discharging temperature of 333.15 K and a f of 0.20. In comparison to the existing absorption thermal energy storage systems, the proposed system using LiNO3-[BMIM]NO3/H2O also shows outstanding performance in various aspects. This new system with the LiNO3-[BMIM]NO3/H2O alternative working fluid has a great potential for utilizing solar energy for combined cooling and heating.

CO2,gas-H2Oliquid isotope exchange rates up to 150 °C – Experimental study and application to hydrothermal CO2

CO2 isotopologues of hydrothermal origin may yield unique information about the hydrothermal system such as the reservoir temperature or advection velocities. The full understanding of the isotopic signal of CO2 from hydrothermal systems, however, is linked to a good knowledge of the isotopic re-equilibration behaviour. In the last decade multiply-substituted isotopologues of CO2 (i.e. Δ47) emerged as a new tracer that is particularly promising for determining equilibration or source temperatures.Using Δ47 values as proxy for hydrothermal systems relies on the assumption that Δ47 reflects the temperature of the CO2 source at equilibrium conditions. In cases where isotope values change with time, such as during fluid advection across a temperature gradient, the precise knowledge of isotope re-equilibration time scales is a fundamental requirement for the correct evaluation and interpretation of transient signals. Re-equilibration smoothes or even erases the original source signal.We conducted a suite of laboratory experiments on CO2 in contact with liquid water and determined the re-equilibration rate constants between 25 °C and 150 °C for oxygen (δ18O) and clumped isotopes (Δ47) of CO2. The rate constants k for both isotope tracers are indistinguishable within the studied temperature range and are used as basis for the case study on CO2 of hydrothermal origin.The Δ47 values of the investigated hydrothermal waters generally correspond to the discharge temperature. Δ47 values of CO2 from water at a deep geothermal system were higher than expected for bottom hole temperatures and lower than for the well head discharging water temperature and reflect the continuous re-equilibration during the ascent of the water.

A combination of fins-nanoparticle for enhancing the discharging of phase-change material used for liquid desiccant air conditioning unite

Abstract A combination of fins-nanoparticle is essential for enhancing the Thermal Energy Storage (TES) that reduces the mismatch between energy supply and energy demand and this employs for Liquid Desiccant Air Conditioning Unite. Major problem is that most Phase-Change Materials (PCMs) have low thermal conductivity (k≤ 0.2 W/m K), resulting in an incomplete charging and discharging processes. Triplex-Tube Heat Exchanger (TTHX) was numerically and experimentally designed, adopted and tested with Alumina nanoparticle (Al2O3) and Paraffin (RT82) that has a discharging temperature of 65 ° C . The both-sides freezing was used as a major method and the experimental findings displayed the influence of mass flow rates on the PCM discharging basing on the change in these rates of 16.2, 29.4 and 37.5 kg/min, respectively. The solidification rate was minimized as the angle direction increased from θ = 90° to θ = 270°. Other important findings were that with fins-nanoparticle, an enhancement for the cooling rate of the PCM, compared with these without nanoparticle. Furthermore, the PCM model was solved by the enthalpy-porosity and the finite-volume methods with the Software Ansys Fluent. The solidification time was reduced for TTHX with longitudinal fins and TTHX with triangular fins to 33% and 34% under the effect of 10% nanoparticle, compared with pure Paraffin, respectively. The total energy released for the PCM and nano-PCM was considered. Close agreement obtained between numerical and experimental findings.

The Effect of Charging and Discharging Lithium Iron Phosphate-graphite Cells at Different Temperatures on Degradation

The effect of charging and discharging lithium iron phosphate-graphite cells at different temperatures on their degradation is evaluated systematically. The degradation of the cells is assessed by using 10 charging and discharging temperature permutations ranging from -20 °C to 30 °C. This allows an analysis of the effect of charge and discharge temperatures on aging, and their associations. A total of 100 charge/discharge cycles were carried out. Every 25 cycles a reference cycle was performed to assess the reversible and irreversible capacity degradation. A multi-factor analysis of variance was used, and the experimental results were fitted showing: i) a quadratic relationship between the rate of degradation and the temperature of charge, ii) a linear relationship with the temperature of discharge, and iii) a correlation between the temperature of charge and discharge. It was found that the temperature combination for charging at +30 °C and discharging at -5 °C led to the highest rate of degradation. On the other hand, the cycling in a temperature range from -20 °C to 15 °C (with various combinations of temperatures of charge and discharge), led to a much lower degradation. Additionally, when the temperature of charge is 15 °C, it was found that the degradation rate is nondependent on the temperature of discharge.

The Effect of Charging and Discharging Lithium Iron Phosphate-graphite Cells at Different Temperatures on Degradation.

The effect of charging and discharging lithium iron phosphate-graphite cells at different temperatures on their degradation is evaluated systematically. The degradation of the cells is assessed by using 10 charging and discharging temperature permutations ranging from -20 °C to 30 °C. This allows an analysis of the effect of charge and discharge temperatures on aging, and their associations. A total of 100 charge/discharge cycles were carried out. Every 25 cycles a reference cycle was performed to assess the reversible and irreversible capacity degradation. A multi-factor analysis of variance was used, and the experimental results were fitted showing: i) a quadratic relationship between the rate of degradation and the temperature of charge, ii) a linear relationship with the temperature of discharge, and iii) a correlation between the temperature of charge and discharge. It was found that the temperature combination for charging at +30 °C and discharging at -5 °C led to the highest rate of degradation. On the other hand, the cycling in a temperature range from -20 °C to 15 °C (with various combinations of temperatures of charge and discharge), led to a much lower degradation. Additionally, when the temperature of charge is 15 °C, it was found that the degradation rate is nondependent on the temperature of discharge.

A New Mixture Refrigerant for Space Heating Air Source Heat Pump: Theoretical Modelling and Performance Analysis

Air source heat pump (ASHP) is becoming a substitute for small coal boilers in rural residential buildings of North China. However, the application of ASHP faces challenges of heating capacity, energy efficiency, ozone depletion potential (ODP) and global warming potential (GWP). Proper refrigerant is a key factor influences the performance of ASHP. In this paper, a new mixture refrigerant named RHR-1 is proposed, which aimed to improve energy efficiency, eliminate ODP and reduce GWP of ASHP refrigerant. The performance of RHR-1 was analyzed and compared with commonly used refrigerants including R134a, R410A, R407C and R22 in terms of heating coefficient of performance (COPh), compression ratio (CR) and discharging temperature (DT). The results show that, under the design cases, where supply water temperatures vary from 35 °C to 50 °C and outdoor air temperatures vary from −15 °C to 15 °C, the COPh of RHR-1 are in the range of 2.43–4.93. The COPh of RHR-1 is higher than other candidates when the supply water temperature is above 40 °C. The CR and DT of RHR-1 are in medium levels of the compared samples. A logarithmic regression equation was deduced to get the relationship of COPh with temperature difference between supply water and outdoor air which suggested the temperature difference should be controlled within 47.5 °C to get reasonable COPh. In addition, RHR-1 has no ODP, and its GWP is 279, which is much lower than other candidates. RHR-1 could be a reasonable refrigerant used in ASHP for space heating in North China.

The Effect of Electrolyte Composition and Additives on Lithium Plating during Low Temperature Charging

There is considerable international interest in the exploration of the icy moons of Jupiter and Saturn, particularly Europa, Enceladus, Ganymede, Titan and Calisto. NASA is currently considering a mission to the surface of Europa, where the average temperature is approximately -170 °C (for comparison, Mars has an average surface temperature of -63 °C). Such extreme temperatures pose serious challenges for batteries which are used either as the primary power source or to store energy from photovoltaics (PVs) or radioisotope thermoelectric generators (RTGs). Additionally, low temperature rechargeable battery operation is of considerable interest to the automotive and aviation industries, where low temperature performance and decreased lifetime still remain as significant hurdles to overcome. To enable these potential missions to icy moons, the Electrochemical Technologies Group (ETG) at the Jet Propulsion Laboratory (JPL) has engaged in development of long-life rechargeable batteries for continuous operation at low temperatures. All-carbonate based lithium-ion electrolytes, as well as solutions containing ester co-solvents, were evaluated after drawing from experience of developing cell chemistries for past and present missions, including the Mars Exploration Rovers (MER) and the Mars InSight program. One major issue to overcome for long life low temperature battery is to prevent lithium plating during charging. Here, we study the effects of electrolyte composition and electrolyte additives on the low temperature charging in three-electrode laboratory cells. Additives, such as vinylene carbonate (VC), are generally added to the electrolyte to form protective films on the electrodes which prolong life at ambient temperatures, however, these protective films can impede lithium intercalation kinetics and cause significant problems during charging at low temperatures. Most additives that were studied lowered cathode film resistance but increased anode SEI resistance, leading to an imbalance between the electrodes. This led to a substantial increase in lithium plating at low temperatures. Electrolyte compositions were investigated using three-electrode experimental cells consisting of MCMB carbon anodes, LiNiCoAlO2 cathodes (electrodes fabricated by Enersys-Quallion, LLC), and lithium reference electrodes, at different temperatures using a combination of tests, including electrochemical impedance spectroscopy (EIS), linear micro-polarization and Tafel polarization. Low temperature cycling was carefully studied using differential analysis (dQ(mAh)/dV) as a means to estimate the amount of lithium that was plated during the charge. The effect of charge rate and charge voltage upon this behavior, pulse discharging, and low temperature discharge after room temperature charging were also investigated. Using a methyl propionate-based electrolyte formulation containing a beneficial additive, we did not observe the presence of lithium plating during charging at -30 °C using C/5 rates and were able to suppress lithium plating to an estimated 11% of the total capacity at -50 °C. ACKNOWLEDGEMENT The work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA) and supported by the NASA Game Changing Development Program.

Theoretical and experimental investigation of a closed sorption thermal storage prototype using LiCl/water

A 1 kWh lab-scale sorption prototype using LiCl-water was theoretically and experimentally investigated for sorption thermal energy storage. A type of consolidated composite matrix is developed for the system by using AC (activated carbon), LiCl, expanded natural graphite treated with sulphuric acid (ENG-TSA) to increase heat transfer and SS (silica solution) to enhance mechanical strength. Thermal conductivity and permeability were measured first. A two-dimensional model considering the combined heat and mass transfer was developed to predict the sorption kinetics of the reactor. Under the operation condition of a charging temperature of 85 °C and a discharging temperature of 40 °C, the experimentally recovered heat is 2517 kJ, resulting a heat storage efficiency of 93%. The heat storage density is 874 kJ/kg consolidated sorbent or 2622 kJ/kg LiCl. The experimental results of the prototype were compared with the simulated results. The established two-dimensional model proves to be effective since the general evolution trends of experimental and simulated outlet fluid temperatures are in good agreement. An average gap of about 0.4 °C between the experimental and simulated outlet temperature may be caused by the heat loss and the constant pressure assumption.

A systematic multi-step screening of numerous salt hydrates for low temperature thermochemical energy storage

In this paper, the potential energy storage density and the storage efficiency of salt hydrates as thermochemical storage materials for the storage of heat generated by a micro-combined heat and power (micro-CHP) have been assessed. Because salt hydrates used in various thermochemical heat storage processes fail to meet the expectations, a systematic evaluation of the suitability of 125 salt hydrates has been performed in a three-step approach. In the first step general issues such as toxicity and risk of explosion have been considered. In the second and third steps, the authors implement a combined approach consisting of theoretical calculations and experimental measurements using Thermogravimetric Analysis (TGA). Thus, application-oriented comparison criteria, among which the net energy storage density of the material and the thermal efficiency, have been used to evaluate the potential of 45 preselected salt hydrates for a low temperature thermochemical heat storage application. For an application that requires a discharging temperature above 60°C, SrBr2·6H2O and LaCl3·7H2O appear to be the most promising, only from thermodynamic point of view. However, the maximum net energy storage density including the water in the water storage tank that they offer (respectively 133kWhm−3 and 89kWhm−3) for a classical thermochemical heat storage process are not attractive for the intended application. Furthermore, the thermal efficiency that would result from the storage process based on salt hydrates without condensation heat recovery appears also to be very low (lower than 40% and typically 25%). Even for application requiring lower discharging temperature like 35°C, the expectable efficiency and net energy storage density including the water storage remain low. Alternative processes are needed to implement for salt hydrates in low temperature thermochemical heat storage applications.

Energy analysis of thermal energy storages with grid configurations

In some thermal networks like district energy systems, there can exist conditions, depending on space availability, economics, project requirements, insulation, storing media type and other issues, for which it may be advantageous to utilize several thermal energy storages (TESs) instead of one. Here, various configurations for multiple TESs are proposed and investigated. Significant parameters for a TES, or a set of TESs, include discharging temperature and recovered energy. First, one TES is modeled to determine the final temperature, energy recovery, and energy efficiency. Next, characteristics for various grid configurations of multiple TESs are developed as functions of TES characteristics (e.g., charging and discharging temperatures and energy quantities). Series, parallel and comprehensive grid TES configurations are considered. In the parallel configuration, the TESs behave independently. This suggests that the TES can consist of different storage media types and sizes, and that there is no restriction on initial temperature of the TES. In the series configuration, the situation is different because the TESs are connected directly or indirectly through a heat exchanger. If there is no heat exchanger between the TESs, the TES storage media should be the same, because the outlet of one TES in the series is the inlet to the next. The initial temperature of the second TES must be smaller than the discharge temperature of the first. There is no restriction on the TES size for series configurations. The general grid configuration is observed to exhibit characteristics of both series and parallel configurations.

Cycle performance studies on HFC-161 in a small-scale refrigeration system as an alternative refrigerant to HFC-410A

In this paper, the refrigerant HFC-161 as an alternative refrigerant to HFC-410A is presented in a small scale refrigeration system. Theoretical cycle performances of HFC-410A, HFC-32 and HFC-161 are calculated and analyzed under the rated working condition. The results show that the COP of HFC-161 is 10.0% and 17.8% higher than that of HFC-32 and HFC-410A, respectively, and the discharge temperature of HFC-161 is the lowest among these refrigerants. Experimental tests were also performed on a vapor-compression refrigeration system with a rotor compressor which was originally designed for HFC-410A to compare the cycle performance of the HFC-410A, HFC-32 and HFC-161 under different working conditions. Experimental results show that the HFC-161 can achieve higher COP by 15–25% than HFC-410A and HFC-32, and the discharging temperature of HFC-161 is much lower than that of HFC-410A and HFC-32. The power consumption and cooling capacity of HFC-161 are the smallest among these refrigerants. The cooling capacity and COP of HFC-32 is very similar to those of HFC-410A, but discharging temperature and power consumption of HFC-32 are slightly higher those of HFC-410A under most working conditions. These results show that HFC-161 is a promising alternative refrigerant to HFC-410A for small-scale refrigeration systems, which supply a very valuable reference for the actual system of HFC-161.

Geological nvestigations in the Chukchi Sea and the adjacent areas of the Arctic Ocean during the RUSALCA-2009 expedition

The Joint Russian-American LongTerm Census of the Arctic Project (RUSALCA) started in Novem� ber of 2003 for the longterm monitoring of the Arctic environment. The studied region comprises poorly studied areas of the Chukchi Sea and the adjacent seg� ment of the Arctic Ocean near the Russia-United States boundary. This area is characterized by maximal rates of the environmental changes in the Arctic dur� ing the last decades, which is expressed, for example, in the enhanced ice melting (Fig. 1). Therefore, this project was aimed at the longterm monitoring of the Arctic environment and searching for the factors responsible for these changes. In this connection, of importance is the testing of different hypotheses explaining such significant environmental changes in the region under consideration. The main of these hypotheses are the increased water and heat exchange via the Bering Strait, the strengthened air heat transfer in the northern direction, and the upwelling of rela� tively warm intermediate Atlantic waters, which pene� trate into the eastern Arctic Ocean along the Eurasian continental slope. There is also an assumption con� cerning the activated geological processes in this region based on the development of a graben-rift sys� tem of nearmeridional and nearlatitudinal riftogenic structures in the Chukchi Sea (Fig. 1) formed in the Mesozoic and activated in the Late Cenozoic. This system is best studied in the socalled Chukchi Gra� ben, a neotectonic structure extending from eastern Chukotka in the south to at least the Herald Trench in the Chukchi Sea in the north (Fig. 1). Its onshore part studied in eastern Chukotka (the Kolyuchino- Mechigment zone) hosts Late Cenozoic volcanics and many hydrothermal vents with a discharging water temperature up to 97