A comparative study on the performances of flat plate and evacuated tube collectors deployable in domestic solar water heating systems in different climate areas

Using TRNSYS software, a comparison of the energy performances of flat-plate collectors (FPCs) and evacuated-tube collectors (ETCs) in domestic solar water heating systems located in different climate areas was carried out in order to ascertain solar energy utilization. Investigations were carried out on single FPCs and ETCs and also for strings of four panels connected in series. Tests were conducted using simulations for water as heat transfer fluid with a fixed fluid flow rate and varying the temperature of the collector's returning fluid. The maximum power peak decreases with the increase in the inlet temperature of the fluid to the collector in the FPC. The maximum outlet temperature of the FPC is higher than the ETC, most of the time. The evacuated-tube collector performs better only in cold climate areas. Simulations suggest that the use of the FPC is strongly discouraged in cold climatic areas due to thermal losses, whereas the ETC works well with reduced dispersion of heat. In warm seasons, on the contrary, the FPC takes advantage of the high environmental temperature which heats the fluid. The maximum yearly outlet temperature and useful power peak predicted in different climatic areas were investigated by varying the temperature of the fluid inlet fed to the two strings of four FPCs and ETCs. In all cases, the outlet temperature is higher in the ETC technology

Mechanical and metallurgical properties of co2 laser beam inconel 625 welded joints

In the frame of the circular economy, welding of Ni‐based superalloys has gained increasing importance when applied, for instance, to repairing highly expensive components widely used in strategical sectors, such as the defense and aerospace industries. However, correct process parameters avoiding metallurgical defects and premature failures need to be known. To reach this goal, Inconel 625 butt‐welded joints were produced by CO2 laser beam welding and different combinations of process parameters. The experimental investigation was carried out with three parameters in two levels with an L4 orthogonal array. Laser power, welding speed, and shielding gas flow rate were varied, and the results were reported in terms of mechanical properties, such as microhardness, tensile strength, distortion, residual stress, and weld bead geometry, and metallurgy. At a lower welding speed of 1 m/min, the full penetration was observed for 3.0 kW and 3.3 kW laser powers. However, sound welds (porosity‐free) were produced with a laser power of 3.3 kW. Overall, the obtained full‐penetration specimens showed a tensile strength comparable with that of the parent material with residual stresses and distortions increasing with the increase in heat input

Thermal and Residual Stress Distributions in Inconel 625 Butt-Welded Plates: Simulation and Experimental Validation

Thermal and residual stress distributions induced by the gas tungsten arc welding (GTAW) process on Inconel 625 were studied using numerical simulation and experiments. A multi-pass welding model was developed that uses a volumetric heat source. Thermomechanical analysis is carried out to assess the Thermal and residual stress distributions. Experiments were carried out with 5 mm thick Inconel 625 plates. X-ray diffraction techniques were used to measure residual stresses, and IR thermometry was employed to capture the temperature values on the welded joints. Simulations were performed with ANSYS numerical code, and a close agreement was found between the predicted and experimentally measured residual stress. Thermal measurements were collected pass by pass from the analysis, and the agreement was 9.08%. The agreement between the measured and analysed residual stress was 11%

A Review on Geothermal Renewable Energy Systems for Eco-Friendly Air-Conditioning

Nowadays, air conditioning consumes, on average, around one-fifth of the total power used in buildings globally. The present paper aims to provide the present status on the employment of Earth-to-Air Heat eXchangers (EAHX) to contain the consumption of energy and to reduce the effect on the environment in response to the Montreal and Kyoto protocols in a way to achieve cleaner energy production with a low Global Warming Potential (GWP) and a low ozone depletion potential (ODP). Different peculiarities and applications (direct or hybrid) are critically analyzed and reviewed. Specifically, in this paper, the different hybrid applications presented in the literature, where the Earth-to-Air Heat eXchangers are coupled to advanced systems, are reviewed. Finally, an IoT-based EAHX control system plan is reported and discussed to optimize energy efficiency and thermal comfort to suit operating conditions under different time zones

A review on methods to reduce weight and to increase efficiency of electric motors using lightweight materials, novel manufacturing processes, magnetic materials and cooling methods

The electric motor is the mechanism that transforms electrical energy into mechanical energy. Nowadays, electric motors are the cause of a considerable share of the use of electricity and therefore of the energy consumptions (70% in the industrial sector and 25- 30% in the tertiary sector). Faced with ever-increasing energy demand and with a view to adhering to the all-over-the world imperative of adopting measures to reduce energy consumption in all the involved sectors, the use of efficiency enhanced electric motors is required. Generally, the efficiency of an electric motor depends on the type of motor, the size of the motor, the utilization factor, but also on the quality and quantity of the materials employed. Therefore, from all these aspects the need of using energy and costefficient components for developing electric motors arises. This review paper aims to draw a general framework on the methods of increasing efficiency and of reducing weight of the electric motors

Improving the energy performances of the refrigeration systems with subcooling using the eco-friendly refrigerant R600A: Initial experimental results

In this paper the attention is focused on introducing the initial experimental results of a comparative experimental investigation on the energy performances of R600a tested as drop-in of R134a in a test-bench refrigeration system developed at the School of Mechanical Engineering of VIT University located in Vellore (India). Moreover, a comparison of the energy performances was pursued also with the system working with and without sub-cooling. The initial experimental investigation is performed respecting the requirement that the two fluids occupy the same volume. The initial energy performances are carried out in terms of evaporator temperature, coefficient of performance and refrigeration effect. The effect of drop-in with R600 a system previously working with R134a, carries an enhancement of the energy performances in terms of COP and refrigeration effect. Moreover, subcooling carries to an additional benefit on the refrigeration effect. The introduced initial experimental results constitute just the first step of a bigger investigation to be conducted in India, focused on analyzing the impact of the drop-in of HFC with new eco-friendly refrigerants