GLI IMPIANTI HVAC E LA PANDEMIA DA SARS-CoV-2 Dobbiamo ripensare la progettazione?

L'avvento della pandemia Sars-Cov-2 ha costretto al ripensamento di tutti i sistemi HVAC, a partire dalle condizioni di progetto fino agli aspetti funzionali e dimensionali. L'articolo esamina gli aspetti salienti e cerca di integrare le nuove sensibilità con quelle esistenti al fine di proporre soluzioni sostenibili a medio e lungo termine

Ventilazione ed efficienza energetica negli impianti ad aria per gli edifici del futuro: una visione a quattro dimensioni

I recenti eventi legati alla pandemia si uniscono alla crescente sensibilità rispetto ai temi ambientali, alla generale attenzione rispetto alla sostenibilità e alla responsabilità per le future generazioni. Tutti questi temi convergono verso una generale esigenza di miglioramento delle prestazioni degli edifici e, allo stesso tempo, alla riduzione dei costi energetici. La presente memoria presenta quattro differenti aree di miglioramento applicabili agli impianti ad aria sulle quali si ritiene che è arrivato il momento di concentrare gli sforzi concettuali e tecnologici. Le quattro dimensioni del miglioramento proposte sono le seguenti: la riduzione delle perdite d’aria, l’ottimizzazione del controllo della diffusione dell’aria negli impianti VaV, l’implementazione di sistemi selettivi per l’abbattimento di contaminanti specifici, la considerazione degli aspetti di contesto nella valutazione del recupero di calore dall’aria espulsa. Le quattro direzioni indicate sono ritenute quelle che, nell’ambito dei sistemi ad aria, riservano maggiori margini di ottimizzazione e questo risulta tanto più vero quanto più queste strade vengono intraprese contemporaneamente. Esse sono finalizzate a minimizzare lo sforzo energetico massimizzando la prestazione in termini di mantenimento della qualità dell’aria. Questo obiettivo può essere perseguito ridefinendo i vincoli che fino ad oggi non hanno permesso di sfruttare al massimo le potenzialità offerte dai sistemi a portata variabile. L’approccio presentato è prevalentemente un approccio prestazionale rivalutato alla luce dei miglioramenti delle tecnologie produttive e di caratterizzazione dei componenti, della possibilità di considerare i sistemi ad aria come parte potenzialmente sinergica di sistemi più complessi e delle nuove sensibilità sviluppate a seguito dell’avvento della Pandemia. I miglioramenti ottenibili in termini percentuali da una azione di questo tipo promettono di risultare superiori rispetto a qualunque implementazione a livello di singolo componente, tuttavia essi richiedono un cambio di approccio da parte dei progettisti e la disponibilità dei costruttori a lavorare per consentire lo sviluppo di procedure normalizzate applicabili su vasta scala

Ventilation and energy efficiency in Air Systems for future buildings: a four dimensions approach

Recent pandemic events are combined with a growing awareness of environmental issues, a general focus on sustainability and responsibility for future generations. All these issues converge towards a general need to improve the performance of buildings and at the same time reduce energy costs. This paper presents four different areas of improvement applicable to air systems on which it is felt that the time has come to focus conceptual and technological efforts. The four dimensions of the proposed improvement are as follows: The reduction of air leakage, the optimization of air diffusion control in VaV applications, the implementation of selective systems for the removal of specific contaminants, the system-wide contextualization of heat recovery from exhaust air. The four directions indicated are considered to offer the greatest potential for optimization in the context of air systems, and this is all the more true if these paths are taken simultaneously. They are aimed at minimizing energy effort (i.e., treated air flow rates) while maximizing performance in terms of maintaining indoor air quality. This can be done by repositioning the boundaries that until now have not allowed the full potential offered by a wise application of variable airflow systems. The approach presented is mainly a performance-based approach re-evaluated in the light of improvements in manufacturing and component characterization technologies, the possibility of considering air systems as a potentially synergistic part of more complex systems, and new sensitivities developed following the advent of pandemic events. The potential improvements in percentage terms from such an action promise to be greater than any single component implementation, but they require a change of attitude on the part of designers and a readiness on the part of manufacturers to work towards the development of standardized procedures applicable on a large scale

Ventilation and energy efficiency in Air Systems for future buildings: a four dimensions approach.

Recent pandemic events are combined with a growing awareness of environmental issues, a general focus on sustainability and responsibility for future generations. All these issues converge towards a general need to improve the performance of buildings and at the same time reduce energy costs. This paper presents four different areas of improvement applicable to air systems on which it is felt that the time has come to focus conceptual and technological efforts. The four dimensions of the proposed improvement are as follows: The reduction of air leakage, the optimization of air diffusion control in VaV applications, the implementation of selective systems for the removal of specific contaminants, the system-wide contextualization of heat recovery from exhaust air. The four directions indicated are considered to offer the greatest potential for optimization in the context of air systems, and this is all the more true if these paths are taken simultaneously. They are aimed at minimizing energy effort (i.e. treated air flow rates) while maximizing performance in terms of maintaining indoor air quality. This can be done by repositioning the boundaries that until now have not allowed the full potential offered by a wise application of variable airflow systems. The approach presented is mainly a performance-based approach re-evaluated in the light of improvements in manufacturing and component characterization technologies, the possibility of considering air systems as a potentially synergistic part of more complex systems, and new sensitivities developed following the advent of pandemic events. The potential improvements in percentage terms from such an action promise to be greater than any single component implementation, but they require a change of attitude on the part of designers and a readiness on the part of manufacturers to work towards the development of standardized procedures applicable on a large scale

A pharmaceutical cleanroom HVAC system: energy audit and energy saving options

The paper focus on Energy Audit procedures applied to the HVAC Systems of some cleanrooms at a pharmaceutical industry plant located in the outskirts of Rome. The paper describes instruments, procedures and results obtained. Different energy saving options are described and assessed qualitatively and quantitatively. Possible extensions to different applications are envisaged

Development of a scaled model for the experimental study of air flow patterns in a conditioned indoor space

ABSTRACT A laboratory model of a real warehouse was designed and operated to study the flow patterns generated by its conditioning systems when operated in isothermal conditions. The systems includes a central distribution located near the roof, composed by a long horizontal cylindrical duct with many small holes on its two sides to distribute the fluid, and four outlets at the lower corners of the square floor. The model is scaled down 1:10, and water is used as model fluid to respect the fluid-dynamic similitude. Laser Sheet Visualizations and Particle Image Velocimetry are successfully implemented to describe qualitatively and quantitatively the flow pattern. The velocity maps show that the two lateral jets merge in one central jet directed downward, and two large counter-rotating vortices are formed on its sides. The flow has a strong 3D structure, and often an asymmetry can be present among the two sides of the ambient. The processing of the velocity data allows to calculate many useful parameters. The velocity distribution histograms are used to describe the ability of the system in keeping the air movement and mixing in the whole ambient, and to evaluate the comfort in the occupied zones. The induction coefficient, obtained by the integration of the velocity, is calculated at different vertical distances from the distributor. The developed systems shows big potential in the parametric study of conditioning systems, thanks to its small dimensions, lower costs, easier and faster parameter change when compared to a real scale indoor space

Solutions for full-outdoor-air operation of air rooftop units with direct expansion circuit and integrated recirculation

Following the advent of the Sars – Cov 2 pandemic, HVAC systems have been affected by different interventions both in the emergency and in the medium term. These interventions were dictated by the need to maximise the risk reduction within air-conditioned environments and among these interventions one of the most applied has been the elimination of recirculation in favor of a full-out-door- air operation, specifically in multi-zone systems. Some plant, such as those served by roof-top units, however, provide a minimum share of recirculation that is necessary for the proper functioning of the integrated refrigeration unit. For these units, the elimination of recirculation has led to a significant increase in blocking situations. The research provides the basis for the application of integrated solutions designed to prevent blocking situations for new and existing systems through the insertion of a modulated bypass between the supply air and the external air intake so as to allow temporarily the recirculation function without, however, creating a situation of risk propagation. The proposed solutions have been applied to a real system, the regulation has been carried out in integration with the management logic of the unit and has been tested to be effective in cooling mode