1,721,045 research outputs found
On the optimisation of a direct current (dc) hot-wall refrigerator
No full textThis study presents an experimental investigation conducted on a refrigerator powered by direct current and composed of a 166L cabinet, a condenser embedded in the external wall of the compartment (hot-wall), an internal static evaporator, a hermetic variable speed compressor. The refrigerant fluid used is the R290a, a natural fluid. By placing the refrigerator in a temperature-controlled environment, four external temperatures have experimented: 22, 25, 29 and 32 °C. Three different temperature setpoints have been set for each temperature:-5,-10,-20 °C. In this way, 12 test conditions were defined, and each of them was repeated by imposing four different compressor rotation speeds: 2000, 2500, 3000, 3500 rpm. The set of tests allowed to identify for each operating condition the optimal number of operating revolutions aimed at minimising the energy consumption of the analysed device
Pilot study on isolated thoracic perfusion for the treatment of non-small cell lung cancer stage IIIb and IV.
No full textEnhancing the heat transfer in an active barocaloric cooling system using ethylene-glycol based nanofluids as secondary medium
No full textBarocaloric cooling is classified as environmentally friendly because of the employment of solid-state materials as refrigerants. The reference and well-established processes are based on the active barocaloric regenerative refrigeration cycle, where the solid-state material acts both as refrigerant and regenerator; an auxiliary fluid (generally water of water/glycol mixtures) is used to transfer the heat fluxes with the final purpose of subtracting heat from the cold heat exchanger coupled with the cold cell. In this paper, we numerically investigate the effect on heat transfer of working with nanofluids as auxiliary fluids in an active barocaloric refrigerator operating with a vulcanizing rubber. The results reveal that, as a general trend, adding 10% of copper nanoparticles in the water/ethylene-glycol mixture carries to +30% as medium heat transfer enhancement
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A flexible top-down numerical modeling of an air-cooled finned-tube CO2 trans-critical gas cooler
No full textCarbon dioxide trans-critical refrigeration systems have been deeply investigated over the last years, with the aim to improve their performance by using several possible technical solutions. However, most of them lead to a more complex and expensive system, and therefore a trade-off is always needed to identify the best viable solution. Therefore, many efforts have also been focused on the study of a critical component of the basic carbon dioxide trans-critical cycle, which is the gas cooler, especially by numerical simulations. This work shows a new flexible approach to numeri-cally model an air-cooled finned-tube CO2 trans-critical gas cooler integrating a Top-Down meth-odology with a Finite Difference Method to solve the governing equation of the thermodynamic processes involved. The model was developed to reproduce the behavior of an experimental CO2 refrigeration system, which provided the experimental data used for its validation. In detail, the model showed a good agreement with the experimental data, with average deviations of 1 K (0.3%), 0.9 bar (1%) and 0.15 kW (2.8%) regarding the refrigerant outlet temperature, the refrigerant outlet pressure and the rejected heat, respectively. The Top-Down numerical approach slightly outper-formed the performance of previous numerical models available in the literature. Furthermore, the analysis of the refrigerant temperature and pressure along the tubes and rows also shows that the model can reproduce their behavior consistently and accordingly to data reported in the literature. The proposed approach can be used for detailed thermo-economic analysis of the whole refrigeration system, with the aim to optimize the design of the gas cooler
Biped Robots With Compliant Joints for Walking and Running Performance Growing
Full text linkThis paper deals with the problem of compliance in biped robots locomotion. After a first literature review, we designed and simulated a 3D virtual model of a biped robot conceived with the same link dimensions (and weights) of a standard man. In all simulation, the same input to the robot actuators are proposed, modifying only the compliance of the attached links. We first validated the model and then compared results increasing and reducing compliance on hip, knee and ankle joints. The very good results underline how the robot performances may be increased including the compliant element in the knee. In particular, we noted how including a proper value of the compliance in the knee, power and torque of the actuators may be reduced increasing robot speed
A review on thermal management of battery packs for electric vehicles
Full text linkThe development of efficient Electric Vehicles (EVs) is related to the management of different parts of the powertrain, as the Lithium-ion (Li-ion) batteries. An important feature which affects their safety, performance, and useful life is the average temperature which must be included in an optimal range to prevent several dangerous phenomena. For this reason, Thermal Management Systems (TMSs) of battery packs of EVs are necessary to guarantee correct functioning in all environments and operating conditions. This review has the intention to divulge the recent developments in the thermal management of Li-ion batteries of EVs reached by researchers and car manufacturers to compare academic studies to the state of the art of the automotive industry from a thermal engineering point of view. Several experimental and numerical studies published in literature have been reported, and nine EV models have been analysed to explain how car manufacturers have developed their new models launched on the market. The choice of the models has been made since the quantity and the quality of data available on the official sites of manufacturers and specialist journals. In conclusion, the future perspectives of thermal management of battery packs are resumed to understand which path research and car manufacturers are following for the next generation of EVs
The use of barocaloric effect for energy saving in a domestic refrigerator with ethylene-glycol based nanofluids: A numerical analysis and a comparison with a vapor compression cooler
No full textThis paper focuses on barocaloric refrigeration that could represent a practicable environmentally friendly alternative to vapor compression. The energy performances of an active barocaloric refrigerator working as a domestic cooler are evaluated by means of a 2-Dimensional model, already validated in previous investigations. The energy performances are also compared with experimental data referred to a household vapor compression refrigerator working with HFC134a. The active barocaloric regenerative refrigeration cycle is supposed to work as a domestic refrigerator in temperature range of 255 ÷ 290 K. The heat-transfer fluid is a mixture of 50%ethylene-glycol-50%water, whereas acetoxy silicone rubber is the solid-state refrigerant. In order to enhance the energy performances of the solid-state refrigerator the use of Cu-based nanofluids in the anti-freezing mixture was tested. The addition of Cu-nanoparticles to the 50%ethylene-glycol- 50%water mixture ensures a moderate enhancement of the energy performances (the maximum temperature span, cooling power and coefficient of performance enhancements are +4.0%, +7.3% and +6.7%, respectively). The analysis shows that barocaloric refrigeration can be a promising new technology in the field of domestic refrigeration for energy saving because it always overperforms vapor compression
- …
