Aminhossein Jahanbin | Politecnico di Bari (original) (raw)

Papers by Aminhossein Jahanbin

Energy Conversion and Management, 2023

The retrofit solution for domestic hot water (DHW) system in existing buildings requires to ensur... more The retrofit solution for domestic hot water (DHW) system in existing buildings requires to ensure the long-term energy security and efficiency as well as to minimise occupants’ disturbance, construction works and installation costs. In this regard, the present study performs a techno-economic evaluation on a novel retrofit solution for DHW production in a pilot building. The proposed solution appoints a substantial role to the thermal energy storage through a 2-pipe hot water network utilisable for both DHW and heating purposes. The first storage level is provided by a centralised buffer storage supplied by a PV-BESS-driven heat pump while the second level consists of decentralised modular tanks installed in each dwelling for the production and storage of hot water. Firstly, experimental thermal performance of the proposed decentralised storages is investigated. By developing a dynamic simulation code, the energy efficiency of the proposed solution is compared to that of the existing system in the pilot building as well to that of a typical centralised system as a benchmark solution. Finally, economic analysis of the retrofit solution is performed to address capital expenditures of the system, including purchasing and installation costs, as well as its life cycle cost (LCC). The obtained results indicate that the proposed system reduces the annual energy consumption for DHW production more than 7,200 kWh, with respect to the existing DHW system. Furthermore, it is shown that, in the proposed system, the fraction of thermal loss from piping network decreases by 31.5%, compared to a typical DHW centralised system. Economic assessment of the proposed solution implies that this system, in terms of both mechanical and electrical components, requires 13.7% lower initial investment than a typical centralised system. However, the cost of control systems in this system is higher since it is inherently a control-based system.

Energy and Buildings, 2023

The present study deals with a multi-objective analysis of an innovative decentralised system to ... more The present study deals with a multi-objective analysis of an innovative decentralised system to produce and store domestic hot water (DHW), emphasising on the combined effects of the technological aspect, control strategy and user’s behaviour. The proposed system, by relying on thermal energy storage, decouples energy production and demand while shaves peaks in the energy demand and, at the same time, provides more autonomy to users through local storages. To identify subtle interactions in components of DHW system, dynamic simulations are carried out by establishing a coupled TRNSYS-MATLAB code, calibrated and validated by experimental measurements. The energy analysis implies that the proposed system cuts the required annual electrical energy in half, of which up to 82% of needed primary energy is supplied from renewable sources, compared to previous electrical-decentralised system. The optimisation of the results through applying control strategies indicates that adopting a three-time charging scheme is advantageous in terms of providing a more stable temperature profile as well as a higher hot water temperature. Compared to an available-by-demand operation, this scheme reduces the required total annual electricity by 5.2 % and enhances total thermal loss from components up to 4.0%. Furthermore, a sensitivity analysis on the results emphasises the striking role of the user behaviour in electrical energy consumption either via draw-off temperature or adjusting the pre-defined temperature for activation of the built-in auxiliary heater.

Applied Sciences, 2023

The present study examines the possibility of thermal comfort optimisation inside an office room ... more The present study examines the possibility of thermal comfort optimisation inside an office room where, due to historical heritage, it is possible to modify neither the energetic characteristic of the envelope nor the position of the inlet air vents. The distribution of global and local thermal comfort indices is evaluated in both heating and cooling conditions by establishing a computational fluid dynamics (CFD) model validated against experimental data. The obtained results demonstrate a striking asymmetry of the air velocity and temperature distribution due to the low energy efficiency of the building. In heating mode, the predicted mean vote (𝑃𝑀𝑉
) values were improved if the discharged air from the fan coil was at its maximal velocity. However, at the same time, the vertical air temperature gradient increased by around 0.5 ∘
C in each working station. In the cooling condition, in the absence of the solar radiation, the minimal air-flow rate satisfied the acceptable range of the draught rate (𝐷𝑅
), whereas in the presence of a solar load, it could not meet the required cooling load in all positions, leading to higher floor temperature. The findings of this study allow for identifying and rearranging the optimal position of working stations in terms of thermal comfort.

Thermal Science and Engineering Progress, 2022

The present study investigates the integrated effects of the ceiling radiant cooling and ventilat... more The present study investigates the integrated effects of the ceiling radiant cooling and ventilation on dispersion and deposition of indoor airborne particles. Five groups of particles with different sizes, ranging from 0.1 to 10 µm, are selected to be injected inside a ventilated space equipped with the ceiling radiant cooling panel (CRCP). Two ventilation strategies under different air change rates are considered, namely up-supply and down-supply ventilations. The conjugate heat transfer between the CRCP and indoor air is examined for different inlet temperatures of the chilled water. An Eulerian-Lagrangian CFD model is developed and validated by experimental data in order to predict the turbulent airflow characteristics and thermal performance of the CRCP system as well as the transient particle trajectories. The results indicate that the particle decay rate is associated with the temperature difference between the CRCP surface and surrounding walls. A sensitivity analysis on the results shows that the surface temperature of CRCP in both ventilation methods is a more effective parameter in particle deposition rate, compared to the inlet air velocity; a 40% augmentation of the ventilation rate leads to 2.6% increase in particle decay rate, whereas the same alteration in inlet water temperature of the CRCP results in 7.3% enhancement of the decay rate. It is shown that while the particle decay rate in up-supply ventilation is faster than down-supply one, the down-supply mode removes higher number of particles, for a given ventilation rate. Furthermore, it is shown that the particle concentration in breathing zone diminishes by decreasing the temperature of radiant cooling panel. Findings of the present study are expected to provide insights into future design of the ventilation and ceiling radiant cooling system for a better indoor air quality.

Energy and Built Environment, 2021

Mechanical Ventilation with Heat Recovery (MVHR) systems are gaining increasing interest in build... more Mechanical Ventilation with Heat Recovery (MVHR) systems are gaining increasing interest in buildings with low energy demand, for improvement of the Indoor Air Quality (IAQ) and reduction of the ventilation energy loss. In retrofitted buildings, MVHRs are often integrated with an additional air heater to cover space heating demand. Hence, evaluation of the interactions between MVHR and heat emitter, and their effects on indoor airflow characteristics is of significant importance. The present study aims to investigate effects of a combined MVHR-fan-coil system in heating mode on IAQ and thermal comfort parameters inside a retrofitted room, by means of a computational fluid dynamic (CFD) code. The proposed CFD model is validated by comparing the numerical results with experimental data. The results yielded by numerical simulations allow evaluating the indoor environmental quality characteristics as well as addressing the MVHR and fan coil interactions. The results indicate that the airflow discharged from the fan coil could have a significant impact on the age of the air; while it provides a desirable thermal comfort condition within the room, it may hinder to some extent delivery of the fresh air to the occupied zone due to creation of counterflow fields. Furthermore, it is shown that although increasing the fan speed (ON mode) would slightly enhance the air change efficiency, the OFF mode yields not only a better distribution of the fresh air but also a higher ventilation efficiency than when fan coil operates.

Journal of Building Engineering, 2022

Given the high concentration of indoor airborne particles during the winter and their harmful eff... more Given the high concentration of indoor airborne particles during the winter and their harmful effects on human health, it is of great importance to examine combined effects of the ventilation and heat source on indoor particle dispersion. The present study aims to investigate transient dispersion and deposition of indoor particles under the heat recovery ventilation (HRV). Five groups of particles with different diameters ranging from 0.1 to 10 μm were taken into account, representing the inhalable indoor airborne particles. By considering three different heating systems, including the radiator, floor heating system and fan coil, the integrated ventilation-heating effects on particle dispersion were evaluated and compared. An Eulerian-Lagrangian CFD model was developed to predict turbulent characteristics of the airflow field and unsteady particle trajectories. The role of particle size, air change rate and outdoor temperature was addressed. In addition, influence of the heat source position on the particle decay rate and removal efficiency was investigated. The results indicated that the impact of heating system on the particle decay rate is weakened by increasing the ventilation rate. Among all heating systems, the radiator renders the highest dispersion rate and the slowest decay rate, even lower than a single HRV unit. It was revealed that, for an intermediate ventilation rate, the particle deposition rate in fan coil system is 3.6 and 2.4 times faster than the radiator and floor heating systems, respectively. It was also found that displacing the radiator to the opposite side of the ventilation unit quadruplicates the removal efficiency and leads to 146% enhancement of the decay rate coefficient.

Journal of Physics: Conference Series , 2021

The borehole heat exchanger (BHE) is a critical component to improve energy efficiency and decre... more The borehole heat exchanger (BHE) is a critical component to improve energy
efficiency and decreasing environmental impact of ground-source heat pump systems. The lower
thermal resistance of the BHE results in the better thermal performance and/or in the lower
required borehole length. In the present study, effects of employing a nanofluid suspension as a
heat carrier fluid on the borehole thermal resistance are examined. A 3D transient finite element
code is adopted to evaluate thermal comportment of nanofluids with various concentrations in
single U-tube borehole heat exchangers and to compare their performance with the conventional
circuit fluid. The results show, in presence of nanoparticles, the borehole thermal resistance is
reduced to some extent and the BHE renders a better thermal performance. It is also revealed
that employing nanoparticle fractions between 0.5% and 2 % are advantageous in order to have
an optimal decrement percentage of the thermal resistance.

Applied Thermal Engineering, 2022

The present study aims to investigate comprehensively the performance of various nanofluids in si... more The present study aims to investigate comprehensively the performance of various nanofluids in single U-tube borehole heat exchangers (BHEs). Seven common nanoparticles with the volume fraction ranging from 0.1% to 2.0% are selected to be evaluated as the heat carrier fluid. Firstly, a comparative techno-economic analysis is performed to highlight the merits and drawbacks of each nanofluid. Then, a sensitivity analysis is performed to optimise the decrement percentage of BHE thermal resistance. Finally, by means of the linear regression of numerical results obtained for different nanofluids, simple equations are proposed allowing evaluation of the outlet fluid temperature for nanofluids. The obtained results indicate that Ag- and Cu-based nanofluids are characterised by the highest heat transfer enhancement, although this improvement is at penalty of a higher pressure drop and up to 31% higher required pumping power. The optimum decrement percentage of thermal resistance yielded in presence of Cu-water nanofluid was equal to 4.31%. Furtheremore, it is shown that employing nanofluids to reduce the BHE length is not a promising choice. Economic analysis revealed that the cost of electrical energy for nanofluids due to the higher energy consumption of pump is negligible in comparison with the capital cost of nanoparticles. The SiO2 nanoparticles with a capital cost ranging from 5.8 to 17.5 €/m is the cheapest nanoparticle to employ, unlike the Ag nanoparticles.

Sustainability, 2020

Heat recovery ventilation (HRV) systems can be integrated with an additional air heater in buildi... more Heat recovery ventilation (HRV) systems can be integrated with an additional air heater in buildings with low energy demand in order to cover space heating demand. The employment of coupled HRV-heater systems is, therefore, gaining increasing interest for the improvement of the indoor environmental quality (IEQ), as well as the reduction of ventilation energy loss. The present paper analyses the efficacy of a HRV system, coupled with a low-temperature radiator, in satisfying the IEQ indices inside a retrofitted dormitory room. A computational fluid dynamic (CFD) model based on the finite volume method is established to investigate IEQ characteristics including indoor air quality and thermal comfort condition. The presented CFD code provides a practical tool for a comprehensive investigation of the IEQ indices in spaces employing a coupled HVAC system. In an analysis of indoor air quality, parameters such as age of the air, air change efficiency, and ventilation efficiency in removal of gaseous contaminants, namely VOCs and CO 2 , are evaluated. The results obtained by the numerical model allow addressing the interaction between HRV and radiator systems and its effects on airflow field. The results show the decrease of the indoor operative temperature with increment of the supply air flow rate, which is mainly due to the decreased thermal efficiency of the HRV system. The obtained results indicate that, while higher ventilation rates can significantly decrease the age of the air and gaseous contaminants level, at the same time, it would cause a local discomfort in some parts of the room.

Energies, 2021

Ground-coupled heat pumps usually employ fields of borehole heat exchangers (BHEs), which must be... more Ground-coupled heat pumps usually employ fields of borehole heat exchangers (BHEs), which must be designed by suitable models. In order to validate a BHE model, it is advisable to compare the computation results with experimental data. A well-known data set was provided by Beier et al. (Geothermics 2011, 40) through a laboratory model usually called “sandbox”. Several authors proposed estimates of the thermal properties of the sandbox grout and sand. In this paper, we present a new estimate of those properties, obtained by means of 2D finite-element simulations that consider all the details of the experimental setup, including the thin aluminum pipe at the BHE boundary. Our results show that the measured temperatures in the fluid and in the sand can be reproduced very accurately by considering thermal conductivities 0.863 W/(mK) for the grout and 3.22 W/(mK) for the sand, volumetric heat capacities 4.6 MJ/(m3K) for the grout and 3.07 MJ/(m3K) for the sand, and a slightly enhanced heat capacity of the water contained in the BHE. The 2D simulations are validated by comparison with an analytical solution and by 3D simulations.

E3S Web of Conferences, 2020

The present study investigates the planar Couette flow problem for low Reynolds numbers inside a ... more The present study investigates the planar Couette flow problem for low Reynolds numbers inside a rectangular duct with a morphing cavity serving as a vortex formation promoter. A finite element code implemented in COMSOL Multiphysics is employed to analyze the effects of the cavity aspect ratio and variations of the Reynolds number on formation and topology of the vortices within the embedded cavity. The obtained results indicate that the cavity height is influential in the number of vortices. It is shown by increasing the Reynolds number, a single vortex tends to move towards the outlet. In addition, streamlines demonstrate that small vortices in vicinity of the cavity corner tend to be enlarged with increase of the Reynolds number. The developed numerical model can be extended to the flow structure of natural systems such as an embayment subjected to parallel-to-shore currents.

Energies, 2020

Given that the issue of variations in geometrical parameters of the borehole heat exchanger (BHE)... more Given that the issue of variations in geometrical parameters of the borehole heat exchanger (BHE) revolves around the phenomenon of thermal resistance, a thorough understanding of these parameters is beneficial in enhancing thermal performance of BHEs. The present study seeks to identify relative changes in the thermal performance of double U-tube BHEs triggered by alterations in circuit arrangements, as well as the shank spacing and the borehole length. The thermal performance of double U-tube BHEs with different configurations is comprehensively analyzed through a 3D transient numerical code developed by means of the finite element method. The sensitivity of each circuit configuration in terms of the thermal performance to variations of the borehole length and shank spacing is investigated. The impact of the thermal interference between flowing legs, namely thermal short-circuiting, on parameters affecting the borehole thermal resistance is addressed. Furthermore, the energy exchange characteristics for different circuit configurations are quantified by introducing the thermal effectiveness coefficient. The results indicate that the borehole length is more influential than shank spacing in increasing the discrepancy between thermal performances of different circuit configurations. It is shown that deviation of the averaged-over-the-depth mean fluid temperature from the arithmetic mean of the inlet and outlet temperatures is more critical for lower shank spacings and higher borehole lengths.

Energies, 2020

Ground-coupled heat pump (GCHP) systems usually utilize buried vertical heat exchangers, named bo... more Ground-coupled heat pump (GCHP) systems usually utilize buried vertical heat exchangers, named borehole heat exchangers (BHEs). The accurate design or simulation of a GCHP system requires the calculation of the time-dependent outlet temperature from the BHEs, Tout. However, the most widely employed BHE simulation models yield the time evolution either of the mean temperature of the BHE-ground surface, Tsm, or of that of the fluid, Tfm. In transient regime, it is not easy to relate Tout to either Tsm or Tfm. In this paper we determine, through 3D finite element simulations, simple expressions of a dimensionless coefficient φ allowing the calculation of Tout by means of a simulation model that yields Tfm. These expressions hold for single U-tube BHEs, both in quasi-steady and in unsteady working conditions. We validate our 3D simulation code by comparison with an analytical BHE model. Then, we present applications of our expressions of φ to calculate the time-dependent values of Tout through a BHE model that yields those of Tfm. Finally, we show that the values of φ in quasi-steady working conditions can be used for a simple calculation of the effective borehole thermal resistance.

Future Cities and Environment, 2019

An accurate assessment of thermal comfort inside a building is essential since it is associated t... more An accurate assessment of thermal comfort inside a building is essential since it is associated to the human’s perception of well-being and comfort. In the present study, a 3D computational fluid dynamic (CFD) code is employed to evaluate the indoor comfort indexes for a university office located in a historical building, built of thick masonry walls and of large single-glass windows, using fan coil as an air conditioning system. The experimental measurement has been carried out to validate the numerical model and to obtain the required initial and boundary conditions. The experimental set-up employs an innovative system for the sensor localization, based on acoustic sources, signal processing and trilateration algorithms. By means of finite volume method, the turbulent air flow, the local heat transfer characteristics and the operative temperature inside the room are obtained for a typical winter day. The results yielded by numerical simulations allow to evaluate thermal comfort condition at working places inside the office and to identify the best comfort areas. The results show that even when the air temperature is quite uniform inside the room, the operative temperature at the positions where occupants are placed is significantly affected by surface temperature of the windows, due to the large window to wall surface ratio and also by the position and operational condition of fan coil. It is concluded that 3D comfort map allows to optimize internal layout of the office room; furthermore, the possibility of thermal comfort optimization in specific workstation together with local control of heating system lead to gain remarkable energy saving results.

Applied Energy, 2018

The design of ground-coupled heat pump systems requires the knowledge of the mean temperature T f... more The design of ground-coupled heat pump systems requires the knowledge of the mean temperature T fm of the working fluid in borehole heat exchangers. This quantity is usually approximated by the arithmetic mean of inlet and outlet temperature. The approximation yields an overestimation of the thermal resistance of the heat ex-changer in thermal response tests, as well as errors in the estimation of the outlet fluid temperature in the dynamic simulation of ground-coupled heat pumps. Recently (Applied Energy 206, 2017, 1406-1415), Zanchini and Jahanbin determined, by finite element simulations, correlations that allow an immediate evaluation of T fm in any working condition, with reference to double U-tube boreholes with length 100 m and shank spacing 85 mm. In this paper, the analysis presented there is extended to double U-tube boreholes with any length, between 50 and 200 m, and any shank spacing, between 65 and 105 mm. The results hold for every thermal conductivity of the sealing grout between 0.9 and 1.6 W/(m K), every volume flow rate between 12 and 24 L per minute, every diameter of the BHE and every working condition (heating, cooling, thermal response test), both in quasi-stationary and in transient regime.

Applied Energy, 2017

In the evaluation of thermal response tests and in the dynamic simulation of ground-coupled heat ... more In the evaluation of thermal response tests and in the dynamic simulation of ground-coupled heat pumps, the mean temperature T m of the working fluid in a borehole heat exchanger is usually approximated by the arithmetic mean of inlet and outlet temperature. In thermal response tests, this approximation causes an over-estimation of the thermal resistance of the heat exchanger. In the dynamic simulation of ground-coupled heat pumps, this approximation introduces an error in the evaluation of the outlet temperature from the ground heat exchangers. In this paper, by means of 3D finite element simulations, we provide tables of a dimensionless coefficient that allows an immediate evaluation of T m in any working condition, with reference to double U-tube borehole heat exchangers with a typical geometry. These tables allow a more accurate estimation of the borehole thermal resistance by thermal response tests and a more accurate evaluation of the outlet temperature in dynamic simulations of ground-coupled heat pump systems. Criteria for the extension of the results to other geometries are also provided.

Geothermics, 2018

The effects of the surface temperature distribution on the thermal resistance of a double U-tube ... more The effects of the surface temperature distribution on the thermal resistance of a double U-tube Borehole Heat Exchanger (BHE) are studied by finite element simulations. It is shown that the thermal resistance of a BHE cross section is not influenced by the bulk-temperature difference between pairs of tubes, but is influenced by the thermal conductivity of the ground when the shank spacing is high. Then it is shown that, if the real mean values of the fluid bulk temperature and of the BHE external surface are considered, the 3D thermal resistance of the BHE coincides with the thermal resistance of a BHE cross section, provided that the latter is invariant along the BHE. Finally the difference between the BHE thermal resistance and the effective BHE thermal resistance, defined by replacing the real mean temperature of the fluid with the average of inlet and outlet temperature, is evaluated in some relevant cases.

Journal of Physics: Conference Series , Oct 2016

In the evaluation of Thermal Response Tests (TRTs) and in the design of Borehole Heat Exchanger (... more In the evaluation of Thermal Response Tests (TRTs) and in the design of Borehole Heat Exchanger (BHE) fields, the mean temperature of the fluid Tm is usually approximated by the arithmetic mean Tave of inlet and outlet temperatures. This approximation can yield relevant design errors. An expression for the evaluation of Tm has been proposed by Marcotte and Pasquier (MP, Renewable Energy, 33) for single U-tube BHEs. In this paper, the difference Tm ̶ Tave is determined by 3D finite-element simulations for a double U-tube BHE in 6 unsteady working conditions. The results are validated qualitatively through an approximate analytical method. They show that the MP expression yields too low values of Tm ̶ Tave if applied to double U-tube BHEs, so that specific relations are required.

Engineering Journal, 2017

Forced convective heat transfer and wall characteristics of nanofluid flow containing Al2O3 nanop... more Forced convective heat transfer and wall characteristics of nanofluid flow containing Al2O3 nanoparticles and water inside a miniature tube is studied numerically by means of computational fluid dynamic (CFD) code. Problem is solved by employing finite volume approach using both single-phase (homogeneous) and dispersion models. In both models, constant and temperature-dependent thermophysical properties are used and results are compared to available experimental and theoretical literatures. It can be seen as the Reynolds number increases, the Nusselt number improves, too. However, it is accompanied by higher wall shear stress. Moreover, in the case of temperature-dependent properties, lower values for shear stress were obtained. In comparison with experimental data and available theoretical correlations, dispersion model in both temperature-dependent and constant properties shows a desirable compatibility. On the other hand, single-phase model in constant thermophysical properties underestimates the amount of convective heat transfer. Furthermore, it can be observed at wall, by increasing the particles volume concentration, not only wall temperature decreases also, rate of thermal enhancement decreases slightly.

Applied Thermal Engineering, Mar 2016

The performance of a thin plane radiator in a room is studied by CFD simulations. Different dista... more The performance of a thin plane radiator in a room is studied by CFD simulations. Different distances between radiator and wall are considered. Upwards temperature gradient and downwards temperature gradient are compared. Upwards temperature gradient yields higher performance than downwards. 10 cm distance between radiator and wall yields higher performance than lower distances. a b s t r a c t The performance of a thin plane radiator in a square room with 4 m horizontal sides and 3 m height is analyzed through a 3D finite-volume simulation code implemented in ANSYS Fluent. The radiator is considered as placed at a distance of either 3, or 5, or 10 cm from the window wall, and having a linear temperature distribution at its surface, either increasing (normal configuration) or decreasing (reverse configuration) with height. The code is validated by comparing the mean Nusselt number on the radiator surface with that obtained by applying the correlation of Churchill and Chu for free convection on a vertical surface. Then, the code is employed to determine the velocity and temperature fields in the room, the total power released by the radiator, and the operative temperature. The latter is considered as the main performance index. The results show that the normal configuration yields a better performance than the reverse one, and that a distance of 10 cm between radiator and wall yields a slight performance increase with respect to lower distances.

Energy Conversion and Management, 2023

Energy and Buildings, 2023

Applied Sciences, 2023

Thermal Science and Engineering Progress, 2022

Energy and Built Environment, 2021

Journal of Building Engineering, 2022

Journal of Physics: Conference Series , 2021

Applied Thermal Engineering, 2022

Sustainability, 2020

Energies, 2021

E3S Web of Conferences, 2020

Energies, 2020

Future Cities and Environment, 2019

Applied Energy, 2018

Applied Energy, 2017

Geothermics, 2018

Journal of Physics: Conference Series , Oct 2016

Engineering Journal, 2017

Applied Thermal Engineering, Mar 2016

InTech, Aug 31, 2016

Exploiting nanofluids in thermal systems is growing day by day. Nanofluids having ultrafine solid... more Exploiting nanofluids in thermal systems is growing day by day. Nanofluids having ultrafine solid particles promise new working fluids for application in energy devices. Many studies have been conducted on thermophysical properties as well as heat and fluid flow characteristics of nanofluids in various systems to discover their advantag‐ es compared to conventional working fluids. The main aim of this study is to present the latest developments and progress in the mathematical modeling of nanofluids flow. For this purpose, a comprehensive review of different nanofluid computational fluid dynamics (CFD) approaches is carried out. This study provides detailed information about the commonly used formulations as well as techniques for mathematical modeling of nanofluids. In addition, advantages and disadvantages of each method are rendered to find the most appropriate approach, which can give valid results.

Roomvent, 2021

Mechanical Ventilation with Heat Recovery (MVHR) systems are widely used in new and renovated bui... more Mechanical Ventilation with Heat Recovery (MVHR) systems are widely used in new and renovated buildings, both for Indoor Air Quality (IAQ) improvement and reduction of ventilation energy losses. In some approaches, mainly recommended for residential buildings, they are integrated to the windows frame or external façade. These systems are usually combined with a heat emitter to cover the space heating demand. The present study investigates effects of a combined MVHR system with a fan coil on IAQ characteristics of a student dormitory room undergone the energy retrofitting, through a Computational Fluid Dynamic (CFD) code. The results obtained by the numerical simulation allow assessing distributions of the airflow and temperature inside the room and investigating the IAQ parameters such as the Mean Age of the Air (MAA), local mean age of the air at exhaust vent, and Air Change Efficiency (ACE). Furthermore, the interaction between MVHR and fan coil systems and its impact on IAQ characteristics are addressed.

18th International Conference on Sustainable Energy Technologies – SET , 2019

An accurate assessment of operative temperature inside a building is essential since it is associ... more An accurate assessment of operative temperature inside a building is essential since it is associated to the human's perception of well-being and comfort. In the present study, a 3D computational fluid dynamic (CFD) code is employed to evaluate the indoor operative temperature for a university office located in a historical building, consisting of thick masonry walls and large single glass windows, using fan coil as an air conditioning system. The experimental measurement was carried out using an innovative system for the sensor localization (based on acoustic sources and a specific signal processing algorithm) in order to validate the numerical model and to obtain the required initial and boundary conditions for the case under study. The turbulent air flow, the operative temperature, and the local heat transfer characteristics inside the room are presented in typical winter conditions, allowing to identify the best comfort areas. The results show that the operative temperature of the room is significantly affected by surface temperatures of the windows, especially due to the large windows to wall surface ratio, and by the position and operational condition of fan coil. Comfort conditions inside the room are not uniform and high energy consumption is required to maintain temperature set point. It is concluded that 3D comfort maps on operative temperature and air velocity allow to optimize internal layout of the office room; moreover, the possibility to optimize comfort conditions in specific workstation together with control of operating mode of the fan coil (velocity and temperature of air inlet) allows to gain important energy saving results.

Eurotherm, 2016

The first national conference of new technologies in chemistry and chemical engineering, 2013

National Symposium of Applied Research on Science and Engineering

University of Bologna, 2018

The present Ph.D. dissertation deals with the finite element analysis of the heat transfer proces... more The present Ph.D. dissertation deals with the finite element analysis of the heat transfer processes in double U-tube Borehole Heat Exchangers, called BHEs. As the main outline of this study, it can be pointed out to the analysis of the working fluid temperature distribution, proposing correlations to determine the mean fluid temperature, and the analysis of the thermal resistance and effects of the temperature distribution on it, for double U-tube BHEs. In the evaluation of thermal response tests (TRTs), in the design of the BHE fields, and in the dynamic simulation of ground-coupled heat pumps (GCHPs), the mean temperature Tm of the working fluid in a BHE, is usually approximated by the arithmetic mean of inlet and outlet temperatures. In TRTs, this approximation causes an overestimation of the thermal resistance of the heat exchanger. In the dynamic simulation of GCHPs, this approximation introduces an error in the evaluation of the outlet temperature from the ground heat exchangers. In the present thesis, by means of 3D finite element simulations, firstly, the analysis of the fluid temperature distribution is carried out, then, correlations are proposed to determine the mean fluid temperature, for double U-tube BHEs. Tables of a dimensionless coefficient are provided that allows an immediate evaluation of Tm in any working condition, with reference to double U-BHEs with a typical geometry. These tables allow a more accurate estimation of the borehole thermal resistance by TRTs and a more accurate evaluation of the outlet temperature in dynamic simulations of GCHP systems. Criteria for the extension of the results to other geometries are also provided. In addition, the effects of the surface temperature distribution on the thermal resistance of a double U-tube BHE are investigated. It is shown that the thermal resistance of a BHE cross section (2D) is not influenced by the bulk-temperature difference between pairs of tubes, but is influenced by the thermal conductivity of the ground when the shank spacing is high. Then it is shown that, if the real mean values of the bulk fluid temperature and of the BHE external surface are considered, the 3D thermal resistance of the BHE coincides with the thermal resistance of a BHE cross section, provided that the latter is invariant along the BHE. Eventually, the difference between the BHE thermal resistance (2D or 3D) and the effective BHE thermal resistance, defined by replacing the real mean temperature of the fluid with the average of inlet and outlet temperatures, is evaluated in relevant cases.