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The paper stems from the benefits of the application of energy analysis in the early-stage buildi... more The paper stems from the benefits of the application of energy analysis in the early-stage building design combined with the difficulties that prevent this integration due to the complexity of the needed simulations. The most common solution to overtake this obstacle is to simplify the building energy model, but not enough attention is paid to understand or predict the consequences of this action. The paper focuses on discussing the difference in results evaluated comparing the simulation of a detailed building model, based on all information available on the building during operation, and a simplified one, suitable for the application in early stage design. This result is achieved by defining a methodology, which consists in developing a simplification protocol and applying it to a suitable number of case studies starting from a detailed model and ending in the simplified one after the application of said protocol. The protocol is based on the use of EnergyPlus software both to dev...
Simplified impingement models are largely used in numerical simulation of spray impingement on so... more Simplified impingement models are largely used in numerical simulation of spray impingement on solid walls, since the direct simulation of multiple drop impact is outside of the present computer capabilities. These models are usually semiempirical based on single-drop impact ...
ABSTRACT Experiments to understand the effect of surface wettability on impact characteristics of... more ABSTRACT Experiments to understand the effect of surface wettability on impact characteristics of water drops onto solid dry surfaces were conducted. Various surfaces were used to cover a wide range of contact angles (advancing contact angle from 48 • to 166 • , and contact angle hysteresis from 5 • to 56 •). Several different impact conditions were analyzed (12 impact velocities on 9 different surfaces, among which 2 were superhy-drophobic). Results from impact tests with millimetric drops show that two different regimes can be identified: a moderate Weber number regime (30 < W e < 200), in which wettability affects both drop maximum spreading and spreading characteristic time; and a high Weber number regime (W e > 200), in which wettability effect is secondary, because capillary forces are overcome by inertial effects. In particular, results show the role of advancing contact angle and contact angle hysteresis as fundamental wetting parameters to allow understanding of different phases of drop spreading and beginning of recoiling. It is also shown that drop spreading on hy-drophilic and superhydrophobic surfaces occurs with different time scales. Finally, if the surface is superhydrophobic, eventual impalement, i.e., transition from Cassie to Wenzel wetting state, which might occur in the vicinity of the drop impact area, does not influence drop maximum spreading. C 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757122]
The paper reports an experimental analysis of the secondary atomisation produced by the impact of... more The paper reports an experimental analysis of the secondary atomisation produced by the impact of a single drop on a solid heated surface. Different wall temperatures were used to study different boiling regimes. The size of secondary drops produced by the impact was measured by two techniques, namely the phase Doppler anemometry (PDA) and the image analysis technique (IAT); this
In the development of anti/de-icing systems for aeronautics, wind turbines or telecommunication a... more In the development of anti/de-icing systems for aeronautics, wind turbines or telecommunication antennas to date, less attention is paid to coating strategies. The majority of studies dealing with coatings have focused mainly on reducing ice adhesion forces, to ...
Drops and Bubbles in Contact with Solid Surfaces, 2016
The present review deals with the impact of drops of fluids with complex microstructure (non-Newt... more The present review deals with the impact of drops of fluids with complex microstructure (non-Newtonian) on solid surfaces, with the aim to highlight a number of relevant differences with respect to the impact of drops of Newtonian liquids. Attention is focused on shear-thinning fluids, viscoplastic (or yield-stress) fluids, and viscoelastic fluids, in particular dilute polymer solutions.
Owing to their simple construction, cost effectiveness, and high thermal efficiency, pulsating he... more Owing to their simple construction, cost effectiveness, and high thermal efficiency, pulsating heat pipes (PHPs) are growing in popularity as cooling devices for electronic equipment. While PHPs can be very resilient as passive cooling systems, their operation relies on the establishment and persistence of slug/plug flow as the dominant flow regime. It is, therefore, paramount to predict the flow regime accurately as a function of various operating parameters and design geometry. Flow pattern maps that capture flow regimes as a function of nondimensional numbers (e.g., Froude, Weber, and Bond numbers) have been proposed in the literature. However, the prediction of flow patterns based on deterministic models is a challenging task that relies on the ability of explaining the very complex underlying phenomena or the ability to measure parameters, such as the bubble acceleration, which are very difficult to know beforehand. In contrast, machine learning algorithms require limited a pri...
A low-cost, flexible pulsating heat pipe (PHP) was built in a composite polypropylene sheet consi... more A low-cost, flexible pulsating heat pipe (PHP) was built in a composite polypropylene sheet consisting of three layers joint together by selective laser welding, to address the demand of heat transfer devices characterized by low weight, small unit thickness, low cost, and high mechanical flexibility. A thin, flexible, and lightweight heat pipe is advantageous for various aerospace, aircraft, and portable electronic applications where the device weight, and its mechanical flexibility are essential. The concept is to sandwich a serpentine channel, cut out in a polypropylene sheet and containing a self-propelled mixture of a working fluid with its vapor, between two transparent sheets of the same material; this results into a thin, flat enclosure with parallel channels hence the name “pulsating heat stripes” (PHS). The transient and steady-state thermal response of the device was characterized for different heat input levels and different configurations, either straight or bent at dif...
Langmuir : the ACS journal of surfaces and colloids, Jun 26, 2016
It is well known that a superhydrophobic surface may not be able to repel impacting droplets due ... more It is well known that a superhydrophobic surface may not be able to repel impacting droplets due to the so-called Cassie-to-Wenzel transition. It has been proven that a critical value of the receding contact angle (θR) exists for the complete rebound of water, recently experimentally measured to be 100° for a large range of impact velocities. On the contrary, in the present work, no rebound was observed when low surface tension liquids such as hexadecane (σ = 27.5 mN/m at 25°C) are concerned, even for very low impact velocities and very high values of θR and low contact angle hysteresis. Therefore, the critical threshold of θR ≈ 100° does not sound acceptable for all liquids and for all the hydrophobic surfaces. For the same Weber numbers a Cassie-to-Wenzel state transition occurs after the impact due to the easier penetration of low surface tension fluids in the surface structure. Hence a criterion for drop rebound of low surface tension liquids must consider not only the contact a...
This work defines a methodology aimed at the creation of a simplified energy model able to simula... more This work defines a methodology aimed at the creation of a simplified energy model able to simulate a residential building with a reasonable workload. The simulation results should have a sufficient accuracy at any stage of a building design, by exploiting the benefits of a modular approach with increasing detail rendition. The idea is to verify the accuracy of the simulations comparing different methodologies, from stationary simulations, using a Italian software called TERMUS, to more sophisticated, even if standard, dynamic simulations, using TRNSYS. Such comparisons have already been carried out in the past in different papers, but a thorough analysis of the envelope-plant system using progressive simplification steps has not yet been done, especially for a residential test case in an on-going retrofit process. The results indicate that with the proper simplification steps, shown in the analysis, the accuracy in terms of energy needs and power curves is very high (the difference...
This work presents the creation of a dynamic energy model able to simulate, with a reasonable wor... more This work presents the creation of a dynamic energy model able to simulate, with a reasonable workload, a very large number of integrated building-plant systems with different scales and resolutions, in order to have a design support for architects and designers, reducing their modeling effort and errors. The model includes the dynamic simulation of the building envelope, all the heating plant subsystems, and all the plant components relating to the production of domestic hot water, the latter with possible solar thermal integration. Starting from a detailed model created with the calculation engine Trnsys, the paper explores simplifications that can considerably reduce the number of necessary inputs for the simulations, thus minimizing the modeling, implementation and simulation runtime of the model, while still maintaining an acceptable degree of accuracy with respect to the computational results and real energy consumptions. The model is benchmarked by means of a case study compr...
The paper stems from the benefits of the application of energy analysis in the early-stage buildi... more The paper stems from the benefits of the application of energy analysis in the early-stage building design combined with the difficulties that prevent this integration due to the complexity of the needed simulations. The most common solution to overtake this obstacle is to simplify the building energy model, but not enough attention is paid to understand or predict the consequences of this action. The paper focuses on discussing the difference in results evaluated comparing the simulation of a detailed building model, based on all information available on the building during operation, and a simplified one, suitable for the application in early stage design. This result is achieved by defining a methodology, which consists in developing a simplification protocol and applying it to a suitable number of case studies starting from a detailed model and ending in the simplified one after the application of said protocol. The protocol is based on the use of EnergyPlus software both to dev...
Simplified impingement models are largely used in numerical simulation of spray impingement on so... more Simplified impingement models are largely used in numerical simulation of spray impingement on solid walls, since the direct simulation of multiple drop impact is outside of the present computer capabilities. These models are usually semiempirical based on single-drop impact ...
ABSTRACT Experiments to understand the effect of surface wettability on impact characteristics of... more ABSTRACT Experiments to understand the effect of surface wettability on impact characteristics of water drops onto solid dry surfaces were conducted. Various surfaces were used to cover a wide range of contact angles (advancing contact angle from 48 • to 166 • , and contact angle hysteresis from 5 • to 56 •). Several different impact conditions were analyzed (12 impact velocities on 9 different surfaces, among which 2 were superhy-drophobic). Results from impact tests with millimetric drops show that two different regimes can be identified: a moderate Weber number regime (30 < W e < 200), in which wettability affects both drop maximum spreading and spreading characteristic time; and a high Weber number regime (W e > 200), in which wettability effect is secondary, because capillary forces are overcome by inertial effects. In particular, results show the role of advancing contact angle and contact angle hysteresis as fundamental wetting parameters to allow understanding of different phases of drop spreading and beginning of recoiling. It is also shown that drop spreading on hy-drophilic and superhydrophobic surfaces occurs with different time scales. Finally, if the surface is superhydrophobic, eventual impalement, i.e., transition from Cassie to Wenzel wetting state, which might occur in the vicinity of the drop impact area, does not influence drop maximum spreading. C 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757122]
The paper reports an experimental analysis of the secondary atomisation produced by the impact of... more The paper reports an experimental analysis of the secondary atomisation produced by the impact of a single drop on a solid heated surface. Different wall temperatures were used to study different boiling regimes. The size of secondary drops produced by the impact was measured by two techniques, namely the phase Doppler anemometry (PDA) and the image analysis technique (IAT); this
In the development of anti/de-icing systems for aeronautics, wind turbines or telecommunication a... more In the development of anti/de-icing systems for aeronautics, wind turbines or telecommunication antennas to date, less attention is paid to coating strategies. The majority of studies dealing with coatings have focused mainly on reducing ice adhesion forces, to ...
Drops and Bubbles in Contact with Solid Surfaces, 2016
The present review deals with the impact of drops of fluids with complex microstructure (non-Newt... more The present review deals with the impact of drops of fluids with complex microstructure (non-Newtonian) on solid surfaces, with the aim to highlight a number of relevant differences with respect to the impact of drops of Newtonian liquids. Attention is focused on shear-thinning fluids, viscoplastic (or yield-stress) fluids, and viscoelastic fluids, in particular dilute polymer solutions.
Owing to their simple construction, cost effectiveness, and high thermal efficiency, pulsating he... more Owing to their simple construction, cost effectiveness, and high thermal efficiency, pulsating heat pipes (PHPs) are growing in popularity as cooling devices for electronic equipment. While PHPs can be very resilient as passive cooling systems, their operation relies on the establishment and persistence of slug/plug flow as the dominant flow regime. It is, therefore, paramount to predict the flow regime accurately as a function of various operating parameters and design geometry. Flow pattern maps that capture flow regimes as a function of nondimensional numbers (e.g., Froude, Weber, and Bond numbers) have been proposed in the literature. However, the prediction of flow patterns based on deterministic models is a challenging task that relies on the ability of explaining the very complex underlying phenomena or the ability to measure parameters, such as the bubble acceleration, which are very difficult to know beforehand. In contrast, machine learning algorithms require limited a pri...
A low-cost, flexible pulsating heat pipe (PHP) was built in a composite polypropylene sheet consi... more A low-cost, flexible pulsating heat pipe (PHP) was built in a composite polypropylene sheet consisting of three layers joint together by selective laser welding, to address the demand of heat transfer devices characterized by low weight, small unit thickness, low cost, and high mechanical flexibility. A thin, flexible, and lightweight heat pipe is advantageous for various aerospace, aircraft, and portable electronic applications where the device weight, and its mechanical flexibility are essential. The concept is to sandwich a serpentine channel, cut out in a polypropylene sheet and containing a self-propelled mixture of a working fluid with its vapor, between two transparent sheets of the same material; this results into a thin, flat enclosure with parallel channels hence the name “pulsating heat stripes” (PHS). The transient and steady-state thermal response of the device was characterized for different heat input levels and different configurations, either straight or bent at dif...
Langmuir : the ACS journal of surfaces and colloids, Jun 26, 2016
It is well known that a superhydrophobic surface may not be able to repel impacting droplets due ... more It is well known that a superhydrophobic surface may not be able to repel impacting droplets due to the so-called Cassie-to-Wenzel transition. It has been proven that a critical value of the receding contact angle (θR) exists for the complete rebound of water, recently experimentally measured to be 100° for a large range of impact velocities. On the contrary, in the present work, no rebound was observed when low surface tension liquids such as hexadecane (σ = 27.5 mN/m at 25°C) are concerned, even for very low impact velocities and very high values of θR and low contact angle hysteresis. Therefore, the critical threshold of θR ≈ 100° does not sound acceptable for all liquids and for all the hydrophobic surfaces. For the same Weber numbers a Cassie-to-Wenzel state transition occurs after the impact due to the easier penetration of low surface tension fluids in the surface structure. Hence a criterion for drop rebound of low surface tension liquids must consider not only the contact a...
This work defines a methodology aimed at the creation of a simplified energy model able to simula... more This work defines a methodology aimed at the creation of a simplified energy model able to simulate a residential building with a reasonable workload. The simulation results should have a sufficient accuracy at any stage of a building design, by exploiting the benefits of a modular approach with increasing detail rendition. The idea is to verify the accuracy of the simulations comparing different methodologies, from stationary simulations, using a Italian software called TERMUS, to more sophisticated, even if standard, dynamic simulations, using TRNSYS. Such comparisons have already been carried out in the past in different papers, but a thorough analysis of the envelope-plant system using progressive simplification steps has not yet been done, especially for a residential test case in an on-going retrofit process. The results indicate that with the proper simplification steps, shown in the analysis, the accuracy in terms of energy needs and power curves is very high (the difference...
This work presents the creation of a dynamic energy model able to simulate, with a reasonable wor... more This work presents the creation of a dynamic energy model able to simulate, with a reasonable workload, a very large number of integrated building-plant systems with different scales and resolutions, in order to have a design support for architects and designers, reducing their modeling effort and errors. The model includes the dynamic simulation of the building envelope, all the heating plant subsystems, and all the plant components relating to the production of domestic hot water, the latter with possible solar thermal integration. Starting from a detailed model created with the calculation engine Trnsys, the paper explores simplifications that can considerably reduce the number of necessary inputs for the simulations, thus minimizing the modeling, implementation and simulation runtime of the model, while still maintaining an acceptable degree of accuracy with respect to the computational results and real energy consumptions. The model is benchmarked by means of a case study compr...
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Papers by Marco Marengo