The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Angelo Zarrella - One of the best experts on this subject based on the ideXlab platform.
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Simulation-Based Comparison Between the Thermal Behavior of Coaxial and Double U-Tube Borehole Heat Exchangers
Energies, 2019Co-Authors: Davide Quaggiotto, Angelo Zarrella, Michele De Carli, Giuseppe Emmi, Luc Pockelé, Jacques Vercruysse, Mario Psyk, Davide Righini, Antonio Galgaro, Dimitrios MendrinosAbstract:In this study, the thermal behavior of the coaxial and double U borehole heat exchangers was investigated using numerical simulations in both the long- and short-term. As a reference for borehole heat exchanger specifications, the existing coaxial and double U probes of a geothermal heat pump installed within the Horizon 2020 research project named “Cheap GSHPs” were considered. Nine years of simulations revealed that when borehole heat exchangers are subjected to a balanced thermal load, and intermittent operating modes of the ground source heat pump system are set, the coaxial pipes’ configuration provides better thermal performance due to the higher thermal capacitance of the heat-Carrier Fluid and the lower borehole thermal resistance. The analysis was conducted considering two different types of ground with different thermal conductivity values. As result, the more conductive ground type highlights the higher yield of the coaxial probe.
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A simulation-based analysis of variable flow pumping in ground source heat pump systems with different types of borehole heat exchangers: A case study
Energy Conversion and Management, 2016Co-Authors: Angelo Zarrella, Giuseppe Emmi, Michele De CarliAbstract:Abstract A simulation model of ground source heat pump systems has been used to investigate to what extent a variable flow of the heat-Carrier Fluid of the ground loop affects the energy efficiency of the entire system. The model contemporaneously considers the borehole heat exchangers, the heat pump, the building load, and the control strategies for the circulation pumps of the ground loop. A constant speed of the circulation pumps of the ground loop was compared with a variable flow controlled by means of a constant temperature difference across the heat pump on the ground side considering the load profile of an office building located in North Italy. The analysis was carried out for a single U-tube, double U-tube and coaxial pipe heat exchangers. The control strategies adopted to manage the flow rate of the heat-Carrier Fluid of the ground loop affect both the heat exchange rate of the borehole field and the heat pump’s long-term energy efficiency. The simulations show considerable differences in the system’s seasonal energy efficiency. The constant speed of the circulation pumps leads to the best results as far as the heat pump’s energy performance was concerned, but this advantage was lost because of the greater amount of electrical energy used by the circulation pumps; this, of course, affects the energy efficiency of the entire system. The optimal solution appears then to be a constant temperature difference in the heat-Carrier Fluid across the heat pump.
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performance of heat pumps with direct expansion in vertical ground heat exchangers in heating mode
Energy Conversion and Management, 2015Co-Authors: Michele De Carli, Stefano Fiorenzato, Angelo ZarrellaAbstract:Abstract Ground source heat pump systems represent an interesting example of renewable energy technology for heating and cooling of buildings. The connection with the ground is usually done by means of a closed loop where a heat-Carrier Fluid (pure water or a solution of antifreeze and water) flows and, in heating mode, moves heat from ground to refrigerant Fluid of heat pump. A new solution is the direct expansion heat pump. In this case, the heat-Carrier Fluid inside the ground loop is the same refrigerant Fluid of heat pump. This paper focuses on the energy performance of direct expansion ground source heat pump with borehole heat exchangers in heating mode, looking at residential building installations. For this purpose, the evaporating process of the refrigerant Fluid inside vertical tubes is investigated in order to analyze the influence of the convective heat transfer coefficient on the global heat transfer with the surrounding ground. Then, an analytical model reported in literature for the design of common borehole heat exchangers has been modified for direct expansion systems. Finally, the direct expansion and common ground source heat pumps have been compared in terms of both total borehole length and thermal performance. Results indicate that the direct expansion system has higher energy performance and requires lower total borehole length compared to the common system. However, when the two systems are compared with the same mean Fluid evaporating temperature, the overall length of the ground heat exchanger of the direct expansion heat pump is greater than that of the common system.
Michele De Carli - One of the best experts on this subject based on the ideXlab platform.
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Simulation-Based Comparison Between the Thermal Behavior of Coaxial and Double U-Tube Borehole Heat Exchangers
Energies, 2019Co-Authors: Davide Quaggiotto, Angelo Zarrella, Michele De Carli, Giuseppe Emmi, Luc Pockelé, Jacques Vercruysse, Mario Psyk, Davide Righini, Antonio Galgaro, Dimitrios MendrinosAbstract:In this study, the thermal behavior of the coaxial and double U borehole heat exchangers was investigated using numerical simulations in both the long- and short-term. As a reference for borehole heat exchanger specifications, the existing coaxial and double U probes of a geothermal heat pump installed within the Horizon 2020 research project named “Cheap GSHPs” were considered. Nine years of simulations revealed that when borehole heat exchangers are subjected to a balanced thermal load, and intermittent operating modes of the ground source heat pump system are set, the coaxial pipes’ configuration provides better thermal performance due to the higher thermal capacitance of the heat-Carrier Fluid and the lower borehole thermal resistance. The analysis was conducted considering two different types of ground with different thermal conductivity values. As result, the more conductive ground type highlights the higher yield of the coaxial probe.
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A simulation-based analysis of variable flow pumping in ground source heat pump systems with different types of borehole heat exchangers: A case study
Energy Conversion and Management, 2016Co-Authors: Angelo Zarrella, Giuseppe Emmi, Michele De CarliAbstract:Abstract A simulation model of ground source heat pump systems has been used to investigate to what extent a variable flow of the heat-Carrier Fluid of the ground loop affects the energy efficiency of the entire system. The model contemporaneously considers the borehole heat exchangers, the heat pump, the building load, and the control strategies for the circulation pumps of the ground loop. A constant speed of the circulation pumps of the ground loop was compared with a variable flow controlled by means of a constant temperature difference across the heat pump on the ground side considering the load profile of an office building located in North Italy. The analysis was carried out for a single U-tube, double U-tube and coaxial pipe heat exchangers. The control strategies adopted to manage the flow rate of the heat-Carrier Fluid of the ground loop affect both the heat exchange rate of the borehole field and the heat pump’s long-term energy efficiency. The simulations show considerable differences in the system’s seasonal energy efficiency. The constant speed of the circulation pumps leads to the best results as far as the heat pump’s energy performance was concerned, but this advantage was lost because of the greater amount of electrical energy used by the circulation pumps; this, of course, affects the energy efficiency of the entire system. The optimal solution appears then to be a constant temperature difference in the heat-Carrier Fluid across the heat pump.
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performance of heat pumps with direct expansion in vertical ground heat exchangers in heating mode
Energy Conversion and Management, 2015Co-Authors: Michele De Carli, Stefano Fiorenzato, Angelo ZarrellaAbstract:Abstract Ground source heat pump systems represent an interesting example of renewable energy technology for heating and cooling of buildings. The connection with the ground is usually done by means of a closed loop where a heat-Carrier Fluid (pure water or a solution of antifreeze and water) flows and, in heating mode, moves heat from ground to refrigerant Fluid of heat pump. A new solution is the direct expansion heat pump. In this case, the heat-Carrier Fluid inside the ground loop is the same refrigerant Fluid of heat pump. This paper focuses on the energy performance of direct expansion ground source heat pump with borehole heat exchangers in heating mode, looking at residential building installations. For this purpose, the evaporating process of the refrigerant Fluid inside vertical tubes is investigated in order to analyze the influence of the convective heat transfer coefficient on the global heat transfer with the surrounding ground. Then, an analytical model reported in literature for the design of common borehole heat exchangers has been modified for direct expansion systems. Finally, the direct expansion and common ground source heat pumps have been compared in terms of both total borehole length and thermal performance. Results indicate that the direct expansion system has higher energy performance and requires lower total borehole length compared to the common system. However, when the two systems are compared with the same mean Fluid evaporating temperature, the overall length of the ground heat exchanger of the direct expansion heat pump is greater than that of the common system.
Alexandra Legrand - One of the best experts on this subject based on the ideXlab platform.
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characterization of solid liquid suspensions real large non spherical particles in non newtonian Carrier Fluid flowing in horizontal and vertical pipes
Journal of Food Engineering, 2007Co-Authors: Alexandra Legrand, Marc Berthou, L FillaudeauAbstract:Abstract The objective of this study is to develop a methodology based on flow visualisation in order to measure the cumulative distribution of particles in vertical and horizontal tubes and to validate it with model and real food suspensions. The cumulative particle concentration provides new information in addition to the description of suspension flow, the residence time distribution, as well as the particle to Fluid relative velocity and the friction curves. The method proposed firstly enables us to draw up a geometrical description based on a theoretical analysis of the suspension (homogeneous suspension, stationary bed) and secondly, to define the quantitative criteria issuing from the cumulative particle distribution. The cumulative distribution was investigated with a model suspension (alginate beads in CMC solution) and a real industrial product (bean mixture) versus flow-rate (from 233 up to 2922 l h −1 ), concentration (from 3% up to 26% w/w) and particle-to-pipe diameter ratios (from 0.187 up to 0.330). Strong analogies between model and real suspension behaviour were noted when the particle concentration increases. However noticeable differences were observed and the results show that the flow pattern depends on four major parameters: (i) the orientation of the tubes and (ii) the density differences (and associated dispersion) between the Carrier Fluid and the particles; but (iii) the shape and (iv) the mechanical properties of particles are factors which limit particle concentration increase and cause Fluids to tend toward homogeneity.
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Physical, Mechanical, Thermal and Electrical properties of cooked red bean (Phaseolus Vulgaris L.) for continuous ohmic heating process
Journal of Food Engineering, 2007Co-Authors: Alexandra Legrand, Jean Claude Leuliet, Sophie Duquesne, Régis Kesteloot, Peter Winterton, Luc FillaudeauAbstract:Due to their complex composition and properties, the continuous thermal processing of solid-liquid mixtures (e.g. suspension of fragile particle in viscous Carrier Fluids) remains an empirical and random operation as compared to canning. Alternative technologies (e.g. ohmic heating) may achieve high-temperature treatment in a short time (HTST) but requires a perfect knowledge of thermo-physical and electrical properties of both particles and Carrier Fluid. Food properties are needed and play a significant role to predict and define the quality and behaviour of solid-liquid mixture. The properties of red beans (Phaseolus vulgaris L.) and a model non-Newtonian Carrier Fluid were studied throughout the duration of the process. Physical (theological behaviour, density, shape and dimensions), mechanical (elasticity modulus, maximal deformation and stress) and thermal (heat capacity, thermal conductivity, thermal diffusivity) properties as a function of water content ranging from 11.6 to 67.4% w/w are reported. The electrical conductivity (electrical properties) was described as a function of the temperature and the solid concentration by a semi-empirical equation. The limiting factors to succeed a HTST for heterogeneous products in continuous thermal process were identified and discussed in the light of the properties of the foods involved. The large dispersion of particle mass volume had a simultaneous incidence of the suspension flow and the heat transfer. The volume expansion of particle (+22% between blanched and cooked bean) and the important loss of mechanical properties (-68% for elastic properties) constitutes unavoidable limiting factors inducing mechanical degradation and sometimes plugging of the duct. The electrical conductivity is strongly affected by a combined effect of temperature and solid concentration, which will induces irreversible heat treatment heterogeneity between particles. This work stresses that the continuous conventional or ohmic heating of these cooked dishes will be hard to achieve on an industrial scale.
L Fillaudeau - One of the best experts on this subject based on the ideXlab platform.
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characterization of solid liquid suspensions real large non spherical particles in non newtonian Carrier Fluid flowing in horizontal and vertical pipes
Journal of Food Engineering, 2007Co-Authors: Alexandra Legrand, Marc Berthou, L FillaudeauAbstract:Abstract The objective of this study is to develop a methodology based on flow visualisation in order to measure the cumulative distribution of particles in vertical and horizontal tubes and to validate it with model and real food suspensions. The cumulative particle concentration provides new information in addition to the description of suspension flow, the residence time distribution, as well as the particle to Fluid relative velocity and the friction curves. The method proposed firstly enables us to draw up a geometrical description based on a theoretical analysis of the suspension (homogeneous suspension, stationary bed) and secondly, to define the quantitative criteria issuing from the cumulative particle distribution. The cumulative distribution was investigated with a model suspension (alginate beads in CMC solution) and a real industrial product (bean mixture) versus flow-rate (from 233 up to 2922 l h −1 ), concentration (from 3% up to 26% w/w) and particle-to-pipe diameter ratios (from 0.187 up to 0.330). Strong analogies between model and real suspension behaviour were noted when the particle concentration increases. However noticeable differences were observed and the results show that the flow pattern depends on four major parameters: (i) the orientation of the tubes and (ii) the density differences (and associated dispersion) between the Carrier Fluid and the particles; but (iii) the shape and (iv) the mechanical properties of particles are factors which limit particle concentration increase and cause Fluids to tend toward homogeneity.
Giuseppe Emmi - One of the best experts on this subject based on the ideXlab platform.
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Simulation-Based Comparison Between the Thermal Behavior of Coaxial and Double U-Tube Borehole Heat Exchangers
Energies, 2019Co-Authors: Davide Quaggiotto, Angelo Zarrella, Michele De Carli, Giuseppe Emmi, Luc Pockelé, Jacques Vercruysse, Mario Psyk, Davide Righini, Antonio Galgaro, Dimitrios MendrinosAbstract:In this study, the thermal behavior of the coaxial and double U borehole heat exchangers was investigated using numerical simulations in both the long- and short-term. As a reference for borehole heat exchanger specifications, the existing coaxial and double U probes of a geothermal heat pump installed within the Horizon 2020 research project named “Cheap GSHPs” were considered. Nine years of simulations revealed that when borehole heat exchangers are subjected to a balanced thermal load, and intermittent operating modes of the ground source heat pump system are set, the coaxial pipes’ configuration provides better thermal performance due to the higher thermal capacitance of the heat-Carrier Fluid and the lower borehole thermal resistance. The analysis was conducted considering two different types of ground with different thermal conductivity values. As result, the more conductive ground type highlights the higher yield of the coaxial probe.
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A simulation-based analysis of variable flow pumping in ground source heat pump systems with different types of borehole heat exchangers: A case study
Energy Conversion and Management, 2016Co-Authors: Angelo Zarrella, Giuseppe Emmi, Michele De CarliAbstract:Abstract A simulation model of ground source heat pump systems has been used to investigate to what extent a variable flow of the heat-Carrier Fluid of the ground loop affects the energy efficiency of the entire system. The model contemporaneously considers the borehole heat exchangers, the heat pump, the building load, and the control strategies for the circulation pumps of the ground loop. A constant speed of the circulation pumps of the ground loop was compared with a variable flow controlled by means of a constant temperature difference across the heat pump on the ground side considering the load profile of an office building located in North Italy. The analysis was carried out for a single U-tube, double U-tube and coaxial pipe heat exchangers. The control strategies adopted to manage the flow rate of the heat-Carrier Fluid of the ground loop affect both the heat exchange rate of the borehole field and the heat pump’s long-term energy efficiency. The simulations show considerable differences in the system’s seasonal energy efficiency. The constant speed of the circulation pumps leads to the best results as far as the heat pump’s energy performance was concerned, but this advantage was lost because of the greater amount of electrical energy used by the circulation pumps; this, of course, affects the energy efficiency of the entire system. The optimal solution appears then to be a constant temperature difference in the heat-Carrier Fluid across the heat pump.