1,721,009 research outputs found
Energy and exergy analysis of a HVAC system having a ground source heat pump as generation system
No full textThis study reports on a dynamic simulation of the annual performance of a HVAC system consisting of a ground coupled heat pump (GCHP), which has which has a ground heat exchanger with horizontal pipes for winter and summer seasons. The simulations are performed by employing the software Trnsys. The HVAC system is connected to a thermal storage tank containing warm water in winter and cold water in summer, which serves a single-family dwelling located in the city of Rome, Italy. A first- and second-law analysis of the yearly performance of the entire system and of the single components was carried out, highlighting the components with the lowest exergy efficiency
Energetic Optimisation of the Domestic Hot Water System in a Residential Building by Means of Dynamic Simulations
No full textThe present study deals with the energetic optimisation of Domestic Hot Water (DHW) system in a residential building located in Catania, Italy. Each dwelling is equipped with a specific decentralised tank with an internal heat exchanger which is connected to a 2-pipe hot water network system for tank charging. The technical water is produced by an Electrical Heat Pump (EHP) coupled to a central storage tank. The energy performance analysis of the DHW model is evaluated by means of dynamic simulations under three different scenarios of charging the decentralised storage tanks by circulating pump unit: Pump activated during daytime, activated twice a day, and activated three times per day. The results obtained allow an evaluation of the DHW consumption profile, temperature variation in central storage and decentralised tanks, and the annual electrical/thermal energy analysis. The results indicate that the activation of the circulating pump during the day leads to an achievement of the highest amount of thermal energy, as well as having minimum temperature oscillation in both central storage and decentralised tanks. However, these advantages are at the cost of consuming much more electrical energy by the heat pump and up to 29 % higher emissions of CO2. The best scenario in terms of energy-saving and CO2 emission is the case in which the circulating pump works twice a day, consuming annually 5,832 kWh less electrical energy, compared to the case of an activated pump during the day
A concentrated-parameter model for the validation of a tractor heating system during artificial winter conditions
Full text linkIn the present paper, a concentrated-parameter model is presented, in order to simulate the behavior of a climatic chamber suitably designed for testing tracked and wheeled tractors. Reference is made to standard-severe winter conditions (–18°C), i.e., the tractor dissipates thermal power in a climatic chamber that reproduces winter temperature and humidity conditions. The software package Matlab-Simulink is utilized and the system under investigation consists of 5 blocks. The dynamic modeling first covers a 10 hours period to reach the prescribed conditions for the climatic test chamber. Then, after this preparation period, the tractor’s engine is supposed to work. The simulations show that higher values of the adduction coefficient are preferable since they allow obtaining quickly, and with a lower heating power, the desired comfort conditions for the machine’s cabin
Energetic Optimisation of the Domestic Hot Water System in a Residential Building by Means of Dynamic Simulations
No full textThe present study deals with the energetic optimisation of Domestic Hot Water (DHW) system in a residential building located in Catania, Italy. Each dwelling is equipped with a specific decentralised tank with an internal heat exchanger which is connected to a 2-pipe hot water network system for tank charging. The technical water is produced by an Electrical Heat Pump (EHP) coupled to a central storage tank. The energy performance analysis of the DHW model is evaluated by means of dynamic simulations under three different scenarios of charging the decentralised storage tanks by circulating pump unit: Pump activated during daytime, activated twice a day, and activated three times per day. The results obtained allow an evaluation of the DHW consumption profile, temperature variation in central storage and decentralised tanks, and the annual electrical/thermal energy analysis. The results indicate that the activation of the circulating pump during the day leads to an achievement of the highest amount of thermal energy, as well as having minimum temperature oscillation in both central storage and decentralised tanks. However, these advantages are at the cost of consuming much more electrical energy by the heat pump and up to 29 % higher emissions of CO2. The best scenario in terms of energy-saving and CO2 emission is the case in which the circulating pump works twice a day, consuming annually 5,832 kWh less electrical energy, compared to the case of an activated pump during the day
Experimental data and simulations of performance and thermal comfort in a patient room equipped with radiant ceiling panels
Full text linkHospitals require the highest energy demands in non-residential buildings. They provide healthcare 24/7/365 and, at the same time, they ensure indoor air quality, thermal comfort and sterility. However, several studies reveal that high indoor temperatures and low relative humidity (RH) are often perceived in patient rooms during the heating season, suggesting an important energy saving potential. Against this background, radiant ceiling panel (RCP) systems result to be one of the most appropriate solutions as they allow to achieve significant energy savings while providing the highest level of thermal and acoustic comfort, as well as of infection control. In the present study the microclimatic survey of a patient room at Maggiore Hospital in Bologna, Italy, equipped with an air conditioning system integrated with RCP, has reported occupant thermal discomfort. Experimental data were used to calibrate a building model and dynamic building energy simulations were carried out to analyse indoor air temperature, relative humidity, predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) indexes under different inlet air temperatures, to identify the best design conditions for energy efficiency and thermal comfort improvement. It was found that the highest advantages can be obtained when neutral air is supplied
Dynamic Modelling of a Heat Exchanger Network for a Dairy Plant
Full text linkIn co-and trigeneration plants with internal combustion engines, waste heat from their cooling system can be fed to a heat exchanger network for office heating, hot water production, or used in industrial processes. At the same time, care must be exerted not to cool the return fluid below a threshold, in order to avoid piston seizure. In this work, the heat exchanger network is that of a gas-engine trigeneration system for a large dairy plant in Rome. Since its daily and weekly production schedule is subject to several changes, temperature control must be both precise and efficient. A thermal-hydraulic, dynamic (i.e. time-dependent) model of the heat exchanger network was developed in Matlab/Simulink, to obtain the instantaneous pressure, mass flowrate and temperature of the fluids along the network. The approach is mixed, a lumped-parameter description of the hydraulic and thermal networ, and finite volumes for the heat exchangers. The model has been verified and validated with experimental, steady-state data from the dairy plant and the results found satisfactory
Hourly data for evaluating the carbon dioxide emission factor of heat pumps or other devices connected to the Italian grid
Full text linkThis data article includes an elaboration of carbon dioxide data available from three different online sources in the years from 2016 to 2019. The data article refers to the paper “Interpolating functions for CO2 emission factors in dynamic simulations: the special case of a heat pump” by the same authors. The data are provided on an hourly basis and are useful to determine the carbon dioxide emission of an electric heat pump or other devices connected to the Italian grid. The importance of the provided data is related to the possibility of having an accurate estimation of the CO2 emission when the device works for only a limited period of time during the year or day. Moreover, since the given data are provided in electronic format (.txt file or .xlsx spreadsheet) they are very useful to perform dynamic simulation using self-made or commercial software such as Trnsys, Energy Plus etc
Thermal Characterization of Textile Waste Materials for Reuse in the Energy Refurbishing of Buildings
Full text linkThe study’s findings suggest new applications for End-of-Life Household Materials (EoLHMs), with a focus on new materials derived from textile wastes. The aim is twofold: explore innovative methods to promote the circular economy by reusing EoLHMs in the building sector and refurbishing buildings with particular attention to home-made panels, to favour disadvantaged contexts. Three different materials were tested, and their thermal conductivity was measured according to the ISO 8301 standard. The thermal conductivity as a function of the density was also investigated for a material derived from hemp. Comparisons with other textile materials are presented as well. As a result, the thermal conductivity of the materials ranged from 0.035 to 0.049 W/(m K), typical for insulating materials used in refurbishing applications
The energy saving potential of wide windows in hospital patient rooms, optimizing the type of glazing and lighting control strategy under different climatic conditions
Full text linkIf not properly designed, the adoption of large windows can sometimes have a negative impact on building energy demand. For this reason, aggravated by the outdated building envelope of the healthcare building stock, large fenestration systems are usually avoided in hospitals, especially in old structures. However, with appropriate glazing specifications, the adoption of wider openings can result into significant energy savings, lower costs and strong positive effects on patients and staff well-being. The present study investigates how different window sizes and types of glazing affect heating, cooling and lighting energy demand in a hospital patient room. The objective is to evaluate the energy savings that may be obtained when installing larger windows and to identify the glazing properties allowing one to reach the maximum energy reductions. Simulations were carried out using nine diverse glazing systems, already available on the market, and their energy performance was evaluated in relation to two different window areas: a common size opening, characterized by a 25% Window-to-Wall Ratio (WWR), and a floor to ceiling window, with 77% WWR. The analysis was conducted taking into consideration four different orientations in four Italian cities, supposing two artificial lighting control strategies. The results highlighted how the adoption of wider windows with appropriate glazings and a daylight-linked dimming lighting control strategy may lower the primary energy demand up to 17%
Photovoltaic-thermal solar-assisted heat pump systems for building applications: A technical review on direct expansion systems
Full text linkBuildings have a crucial role in global energy consumption and the release of greenhouse gases, especially due to their heating, cooling, and hot water systems. This study examines the incorporation of photovoltaic thermal (PV/T) and heat pump (HP) technologies, with a specific emphasis on their joint utilization in solar-assisted heat pump (SAHP) systems for enhancing building energy efficiency. The study conducts a thorough examination of contemporary literature to evaluate the effectiveness, feasibility, and performance metrics of PV/T-SAHP systems. Notable progress has been made by incorporating hybrid PV/T collectors, which can produce both electricity and thermal energy at the same time. This has led to enhanced system efficiency and increased reliability in operation. SAHP systems can be classified into numerous configurations, including direct expansion (DX) and indirect expansion (IDX) systems. Their performance under various climatic situations is thoroughly assessed. Concerning the direct expansion systems, the key numerical findings from the papers available in the scientific literature are summarized and discussed. The review highlights the capacity of PV/T-SAHP systems to improve energy efficiency, diminish carbon footprints, and promote sustainability in building applications. Identify future research directions to enhance system design, integration, and performance for wider implementation in low-carbon building initiatives
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