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The preservation of perishable food items within the cold chain is a critical aspect of modern food logistics. Traditional refrigeration systems consume large amounts of energy, without an optimal temperature distribution, leading to potential food spoilage and economic losses. In recent years, the integration of Phase Change Materials (PCMs) into cold chain systems has emerged as a promising solution to address these challenges. This article presents a comprehensive analysis of the utilization of PCMs for food preservation in a refrigerated truck, focusing on the impact on temperature control, phase change fraction, costs, and energy savings. The effectiveness of PCM-based refrigeration system to maintain the refrigerated truck at a temperature of −18 °C under various scenarios and environmental conditions using a transient model was evaluated. The TRNSYS model includes a representation of a conventional refrigerated van's system, with simulations conducted in a Mediterranean climate (Naples). The model's core components consist of Type 56 for cooling load estimation and Type 1270a for the new PCM component. Results indicate that for guaranteeing −18 °C for 10 h, 96.4 kg and 102.2 kg of E-26 and E-29 PCM are needed, respectively, for scenarios with 10 door openings during transportation and for two different velocities of the truck: 30 and 80 km h−1. Results indicate that the incorporation of PCMs in the refrigerated van leads to significant improvements in temperature stability and uniformity, thereby extending the shelf life of perishable food products and reducing the risk of spoilage. Furthermore, the analysis shows that, using the PCMs, a significant reduction of the energy costs can be obtained (up to a maximum of around 79%). [ABSTRACT FROM AUTHOR]

In this paper, the application of solid-state cooling based on the barocaloric effect in the cold food supply chain is investigated. Barocaloric solid-state technology is applied to the final links of the cold food supply chain regarding the steps of retail and domestic conservation. In this context, effective barocaloric cooling entails the refrigeration of food at 5 °C (273 K) and as such is a promising cooling technology due to its energy efficiency and environmental friendliness. The categories of food involved in this investigation are meat and fresh food products like soft cheese, yogurt, and milk. The energy performance of the barocaloric system is analyzed and compared with a commercial vapor compression refrigerator of a similar size, both operating using R600a under the same working conditions. Based on the results of this comparison, it is concluded that barocaloric cooling is a favorable technology for application in the final links of the cold food supply chain if the system operates in an ABR cycle at frequencies between 1.25 and 1.50 Hz with a regenerator comprising acetoxy silicone rubber as the solid-state refrigerant and a 50%EG–50% water mixture as the heat transfer fluid flowing at an optimal velocity of 0.15 m s−1. Thus, an appropriate tradeoff between the temperature span, cooling power, and coefficient of performance is guaranteed. Under these conditions, the barocaloric system outperforms the domestic vapor compression cooler operating using R600a. [ABSTRACT FROM AUTHOR]

Solid-state caloric cooling is a viable route toward a more sustainable way of refrigerating. The refrigerants are solid-state materials with a caloric effect detectable by measuring a temperature variation through an external-field intensity change. The caloric effect could be particularized depending on the properties of the material and the type of field. Magnetocaloric is the effect occurring in ferromagnetic materials through the variation of an external field. Thermodynamically, two are the possible cycles regulating the cooling process in the system: the Active Caloric Regenerative cooling cycle and the solid-to-solid heat transfer (SSHT). The former requires the involvement of an auxiliary fluid for the heat transfer processes; in the latter, the heat transfer can be regulated by thermal diodes with the capability of changing their thermal conductivity depending on the intensity of an external field. The investigation introduced is focused on an SSHT system employing magnetocaloric materials as refrigerants and thermal diodes as the vehiculation elements. The two-dimensionality of the model allows the optimization of the dimensions of both the magnetocaloric and the thermal diode elements to achieve elevated operative frequencies. A comparison between two magnetocaloric materials was performed, Gadolinium and LaFe11.384Mn0.356Si1.26H1.52. Encouraging results on the system, suitably employable in the field of electronic circuit cooling, have been found. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Italy has not yet presented to the scientific community any elastocaloric prototype suitable for refrigeration/air conditioning. The SUSSTAINEBLE project was born from the idea to build a demonstrative elastocaloric prototype for environmental conditioning. The prototype is planned to be rotary and composed by a few bunches of elastocaloric wires crossed by air as heat transfer fluid. Many are the parameters to be investigated before the realization of the device. A numerical practical tool would help to easily optimize the prototype. In this paper a two-dimensional tool of a single bunch of elastocaloric wires based on finite-element method is introduced; it can reproduce step by step the velocity and the pressure field of fluid to predict more accurately the solid-to-fluid heat exchange. The results of a test campaign mostly focused on the optimization of the frequency of the cycle, fluid velocity and the distance between the elastocaloric wires are presented. The results reveal that: (i) 0.12 Hz as frequency; (ii) 7 m s-1 as velocity; (iii) 1.0 mm as optimal wire distance, would better satisfy the trade-off existing in the maximization of temperature span and cooling power per mass unit: 23.7 K and 311.97W kg-1 are the values achieved, respectively. [ABSTRACT FROM AUTHOR]

Electrocaloric is a novel emerging not-in-kind cooling technology based on solid-state materials exhibiting the electrocaloric effect, i.e., the property of changing their temperature because of an adiabatic change in the intensity of the electric field applied. This technology has only attracted the interests of the scientific community in the last two decades, even though it has the main feature of being based on eco-friendly materials that, because of their solid-state nature, do not provide a direct contribution in global warming. Even if some steps have already been taken, the research fields connected to electrocaloric cooling are still open: The identification of the most appropriated thermodynamic cycle, electrocaloric refrigerants, as well as the development of efficient cooling systems. To this purpose, this review paper provides a snapshot of the electrocaloric world and compares the progress made by the inherent scientific community in all the connected fields: the thermodynamic cycles, materials, experimental devices, numerical models, energy performances and prospective cooling applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The aim of this paper is to research the parameters that optimize the thermal performances of a horizontal single-duct Earth to Air Heat eXchanger (EAHX). In this analysis, the EAHX is intended to be installed in the city of Naples (Italy). The study is conducted by varying the most crucial parameters influencing the heat exchange between the air flowing in the duct and the ground. The effect of the geometrical characteristics of the duct (pipe length, diameter, burial depth), and the thermal and flow parameter of humid air (inlet temperature and velocity) has been studied in order to optimize the operation of this geothermal system. The results reveal that the thermal performance increases with length until the saturation distance is reached. Moreover, if the pipe is designed with smaller diameters and slower air flows, if other conditions remain equal, the outlet temperatures come closer to the ground temperature. The combination that optimizes the performance of the system, carried out by forcing the EAHX with the design conditions for cooling and heating, is: D = 0.1 m s−1; v = 1.5 m s−1; L = 50 m. This solution could also be extended to horizontal multi-tube EAHX systems. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper is focused on the resort to geothermal energy, through the employment of an Earth-to-Air-Heat Exchanger (EAHX) positioned upstream of the air-handling unit of an air conditioning system, for an office building in Naples (South Italy). The aim is to evaluate the energy performances of this unusual system compared to the common solution of external air directly entering the air-handling unit. The EAHX is extensively designed and two-dimensionally modeled, and the analysis is solved with finite element method. The model is validated with experimental data and this comparison shows good agreement. With the requirement of providing the building with 1300 m3 h−1 of external airflow, different design solutions for the EAHX are studied, by varying the diameter (in the range 0.2–0.5 m) and length (between 20 and 140 m) of the buried pipes. The results indicate that: smaller tube diameters enhance the heat transfer; a tube length between 80 and 100 m is recommended. Using the EAHX, the reduction of the thermal power of the coils in the air-handling unit is greater than 40% in most cases. Finally, the efficiency of the EAHX is assessed as a function of the tube length and diameter, reaching values up to 0.9. [ABSTRACT FROM AUTHOR]

In this paper the energy performances carried out by an investigation conducted on a Heating, Ventilation and Air Conditioning (HVAC) system, composed by an Air Handling Unit (AHU) for the primary air coupled with a horizontal-pipes Ground-to-Air Heat eXchanger (GAHX) and fan-coil units, for an office building, supposed to be placed in four different cities (Rio de Janeiro, Dubai, Naples, Ottawa) belonging to four different worldwide climatic areas, according to the Köppen climate classification. The investigation is performed by means of a two dimensional numerical model, experimentally validated, of an GAHX solved with finite element method. The results introduced in this paper are carried out by varying the length of the pipes and the air flow velocity; thus, also the number of tubes forming the GAHX is varied since the volumetric flow rate to be provided to the AHU must be kept constant. The energy performances of the above-mentioned HVAC system are analyzed, both in summer and in winter operation modes. Specifically, the reduction of the power of the heating and cooling coils in the AHU due to the pre-treatment of the air operated by the GAHX, the efficiency of the GAHX and the inlet-outlet temperature span are evaluated through a sensitivity analysis. These results lead to say that an GAHX for the geothermal pre-treatment of the air to be introduced into the AHU is energetically very convenient since it leads total thermal power savings in all the investigated cities, that makes this solution competitive. Specifically the best value of power reduction (61.5%) for a 100 m pipe-length GAHX is obtained in Ottawa, a city belonging to continental climate zone. The worst results in terms of power reduction are registered in Rio de Janeiro, a city belonging to the tropical or equatorial climates: this reduction, for a 100 m pipe-length ground to air heat exchanger, is 23.9%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Barocaloric is a solid-state not-in-kind technology, for cooling and heat pumping, rising as an alternative to the vapor compression systems. The former is based on solid-state refrigerants and the latter on fluid ones. The reference thermodynamical cycle is called active barocaloric regenerative refrigeration (or heat pumping cycle). The main advantage of this technology is to not employ greenhouse gases, which can be toxic or damaging for the environment and that can contribute to increasing global warming. In this paper, the environmental impact of barocaloric technology was evaluated through a Total Equivalent Warming Impact (TEWI) analysis carried out with the help of a numerical 2D model solved through a finite element method. Specifically, we propose a wide investigation on the environmental impact of barocaloric technology in terms of TEWI index, also making a comparison with a vapor compression plant. The analysis focuses on both the cooling and heat pump operation modes, under different working conditions and auxiliary fluids. The results revealed that a barocaloric system based on ABR cycle could provide a reduction of the environmental impact with respect to a vapor compression system. The addition of nanofluids contributes in reducing the environmental impact up to −62%. [ABSTRACT FROM AUTHOR]

Barocaloric 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. [ABSTRACT FROM AUTHOR]