Comparison between variable and constant refrigerant flow air conditioning systems in arid climate: Life cycle cost analysis and energy savings

All over the world, there is a call to encourage sustainable energy thinking and implementation. There is an urgent need to consider sustainable solutions in any design projects that are able to reduce energy consumption. In the heating, ventilation, and air conditioning field, the rise of the variable refrigerant flow systems has made big progress. This study presents a life cycle cost analysis to evaluate the economic feasibility of constant refrigerant flow (CRF), and in particular, the conventional ducted unit air conditioning system and the variable refrigerant flow (VRF) system by using detailed cooling load profiles, as well as initial, operating, and maintenance costs. Two operating hours scenarios are utilized and the present worth value technique for life cycle cost analysis is applied to an existing office building located in Qatar, which can be conditioned by CRF and VRF systems. The results indicate that, although the initial cost of the VRF system is higher than that of the CRF system by 23%, the present worth cost of the VRF system is much lower than that of the CRF system at the end of the lifetime due to lower operating costs. There is also a significant energy saving of 27% by using VRF compared to the CRF. The implementation of these results on a national scale will promote the use of sustainable energy technologies such as the VRF system. 2021 by the authors. Licensee MDPI, Basel, Switzerland.Acknowledgments: The authors would like to acknowledge Al Muftah Contracting Company W.L.L. company (Doha, Qatar) for assisting this research in terms of providing useful field data and the usage of the transfer function method (TFM) through the software Hourly Analysis Program (HAP) by Carrier. The authors would also like to thank Qatar National Research Foundation (QNRF) (Doha, Qatar) for funding the open access fees for the publication of this manuscript.Scopu

POSSIBLE USAGE OF VARIABLE REFRIGERANT FLOW IN ARID CLIMATE: TECHNICAL AND MANAGEMENT PERSPECTIVE

All over the world, there is a call to encourage sustainable energy thinking and implementation. In the heating, ventilation and air conditioning field, the rise of the variable refrigerant flow systems has made a big progress throughout the years. This study presents a life-cycle cost analysis to evaluate the economic feasibility of constant refrigerant flow (CRF) in particular the conventional ducted unit air conditioning system that is widely used in Qatar and the variable refrigerant flow (VRF) system. Detailed cooling load profiles will be used for the existing units and the new VRF model in addition to initial, operating, and maintenance costs. Two operating hours scenarios are utilized to consider 12 and 24 operating hours and the present-worth value technique for life-cycle cost analysis is applied to an existing office building located in Qatar which can be conditioned by CRF and VRF systems. The results indicate that although the initial cost of the VRF system is higher than that of the CRF system, the present-worth cost of the VRF system is lower than that of the CRF system at the end of the lifetime due to lower operating costs. The implementation of these results on a national scale will promote the use of sustainable energy technologies such as the variable refrigerant flow system to reduce the energy consumption in Qatar and to improve the national power grid utilization, efficiency, and expansion in the coming years

Life Cycle Cost Analysis for Variable Refrigerant Flow (VRF) and Constant Refrigerant Flow (CRF) Air Conditioning Systems in Arid Climate: Case Study in Qatar

All over the world, there is a call to encourage sustainable energy thinking and implementation. In the heating, ventilation and air conditioning field, the rise of the variable refrigerant flow systems has made a big progress. This study presents a life-cycle cost analysis to evaluate the economic feasibility of constant refrigerant flow (CRF) in particular the conventional ducted unit air conditioning system and the variable refrigerant flow (VRF) system by using detailed cooling load profiles, initial, operating, and maintenance costs. Two operating hour scenarios are utilized and the present-worth value technique for life-cycle cost analysis is applied to an existing office building located in Qatar which can be conditioned by CRF and VRF systems. The results indicate that although the initial cost of the VRF system is higher than that of the CRF system, the present-worth cost of the VRF system is lower than that of the CRF system at the end of the lifetime due to lower operating costs. The implementation of these results on a national scale will promote the use of sustainable energy technologies such as the VRF system

Building social policies in Lebanon

Texte en français, en anglais et en arab

Building social policies in Lebanon

Texte en français, en anglais et en arab

Study protocol for a randomised controlled trial of haloperidol plus promethazine plus chlorpromazine versus haloperidol plus promethazine for rapid tranquilisation for agitated psychiatric patients in the emergency setting (TREC-Lebanon)

Background: Agitated and aggressive behaviours are common in the psychiatric setting and rapid tranquilisation is sometimes unavoidable. A survey of Lebanese practice has shown that an intramuscular haloperidol, promethazine and chlorpromazine combination is a preferred form of treatment but there are no randomised trials of this triple therapy.Methods: This is a pragmatic randomised trial. Setting - the psychiatric wards of the Psychiatric Hospital of the Cross, Jal Eddib, Lebanon. Participants - any adult patient in the hospital who displays an aggressive episode for whom rapid tranquilisation is unavoidable, who has not been randomised before, for whom there are no known contraindications. Randomisation – stratified (by ward) randomisation and concealed in closed opaque envelope by independent parties. Procedure – if the clinical situation arises requiring rapid tranquilisation, medical residents overseeing the patient will open a TREC-Lebanon envelope in which will be notification of which group of treatments should be preferred [Haloperidol + Promethazine + Chlorpromazine (HPC) or Haloperidol + Promethazine (HP)], along with forms for primary, secondary and serious adverse effects. Treatment is not given blindly. Outcome - primary outcome is calm or tranquil at 20 minutes post intervention. Secondary outcomes are calm/tranquil at 40, 60 and 120 minutes post intervention, asleep, adverse effects, use of straitjacket and leaving the ward. Follow-up will be up to two weeks post randomisation.Discussion: Findings from this study will compare the HPC versus HP combination used in Lebanon’s psychiatry emergency routine practice.Trial registration: ClinicalTrials.gov NCT03639558. Registration date, August 21, 2018

Simulation numérique des écoulements d'air et de polluants induits par le mouvement d'une personne : effets sur les dispositifs de confinement dynamique

Devices for extracting toxic vapours from substances used during manipulation, such as laboratory fume cupboards, are widely used to protect the operators. These devices are based on a ventilation system which induces a flow generating suction air to provide containment and extraction of the gaseous pollutants. However, people using these devices induce, by their movements, aerodynamic disturbances which are fundamentally unsteady and turbulent, potentially impacting, often severely, the performance of these protection devices. While their vulnerability when exposed to these disturbances is known, there is currently no available way to quantitatively assess their impact. That said, the emergence of high-performance computation capabilities combined with numerical simulation in fluid mechanics now makes it possible to simulate unsteady and turbulent flows induced by moving obstacles at the scale of a work space. In this context, this work is dedicated to the development of a numerical model essentially based on the combination of a large eddy simulation approach for turbulence and an immersed boundary method for moving obstacles. This numerical model will then allow the study and quantitative analysis of the impact of aerodynamic disturbances on dynamic containment devices. A first part of this work consists, first of all, in carrying out verifications and validations of the different coupled modelling. The numerical model is then used to carry out unsteady and turbulent numerical simulations of the movement of an obstacle in front of a laboratory fume cupboard in use, in a typical size of a laboratory work room. Finally, the results of these simulations are compared with measures of containment efficiency, carried out on a full-scale laboratory experiment.Les dispositifs d’extraction de vapeurs toxiques de produits utilisés lors de manipulation, telles que les sorbonnes de laboratoire, sont massivement employés pour protéger les manipulateurs. Ces dispositifs sont basés sur un système de ventilation générant un écoulement d’air d’aspiration qui doit assurer le confinement et l’extraction des polluants gazeux. Or, les personnes qui utilisent ces dispositifs induisent, par leur mouvement, des perturbations aérauliques qui sont fondamentalement instationnaires et turbulentes, pouvant alors impacter, parfois gravement, le fonctionnement de ces dispositifs de protection. Bien que soit connue leur vulnérabilité lorsqu’ils sont exposés à ces perturbations, il n’existe pas à l’heure actuelle de moyens d’évaluer quantitativement leur impact. Cela dit, l’avènement des moyens de calculs haute performance combiné à la simulation numérique en mécanique des fluides rend aujourd’hui possible la simulation d’écoulements instationnaires et turbulents induits par des obstacles mobiles à l’échelle d’un local de travail. Dans ce contexte, ce travail est dédié à l’élaboration d’un modèle numérique basé essentiellement sur le couplage d’une approche par simulation des grandes échelles pour la turbulence et d’une méthode de pénalisation de type frontière immergée pour les obstacles mobiles. Ce modèle numérique permettra alors l’étude et l’analyse quantitative de l’impact des perturbations aérauliques sur les dispositifs de confinement dynamique. Une première partie de ce travail consiste d’abord à effectuer des vérifications et des validations des différentes modélisations couplées. Le modèle numérique est ensuite utilisé pour réaliser des simulations numériques instationnaires et turbulentes du passage d’un obstacle mobile devant une sorbonne de laboratoire en fonctionnement, dans un volume représentatif d’un local de travail en laboratoire. Enfin, les résultats de ces simulations sont confrontés à des mesures d’efficacité de confinement, réalisées sur une expérience de laboratoire à taille réelle

Simulations numériques des écoulements d'air et de polluant induits par le mouvement d'une personne : effets sur les dispositifs de confinement dynamique

Devices for extracting toxic vapours from substances used during manipulation, such as laboratory fume cupboards, are widely used to protect the operators. These devices are based on a ventilation system generating a flow generating suction air to provide containment and extraction of the gaseous pollutants. However, people using these devices induce, by their movements, aerodynamic disturbances which are fundamentally unsteady and turbulent, potentially impacting, often severely, the performance of these protection devices. While their vulnerability when exposed to these disturbances is known, there is currently no available way to quantitatively assess their impact. That said, the emergence of high-performance computation capabilities combined with numerical simulation in fluid mechanics now makes it possible to simulate unsteady and turbulent flows induced by moving obstacles at the scale of a work space. In this context, this work is dedicated to the development of a numerical model essentially based on the combination of a large eddy simulation approach for turbulence and a immersed boundary method for moving obstacles. This numerical model will then allow the study and quantitative analysis of the impact of aerodynamic disturbances on dynamic containment devices. A first part of this work consists, first of all, in carrying out verifications and validations of the different coupled modelling. The numerical model is then used to carry out unsteady and turbulent numerical simulations of the movement of a mobile obstacle in front of a laboratory fume cupboard in use, in a typical size of a laboratory work room. Finally, the results of these simulations are compared with measures of containment efficiency, carried out on a full-scale laboratory experimentLes dispositifs d’extraction de vapeurs toxiques de produits utilisés lors de manipulation, telles que les sorbonnes de laboratoire, sont massivement employés pour protéger les manipulateurs. Ces dispositifs sont basés sur un système de ventilation générant un écoulement d’air d’aspiration qui doit assurer le confinement et l’extraction des polluants gazeux. Or, les personnes qui utilisent ces dispositifs induisent, par leur mouvement, des perturbations aérauliques qui sont fondamentalement instationnaires et turbulentes, pouvant alors impacter, parfois gravement, le fonctionnement de ces dispositifs de protection. Bien que soit connue leur vulnérabilité lorsqu’ils sont exposés à ces perturbations, il n’existe pas à l’heure actuelle de moyens d’évaluer quantitativement leur impact. Cela dit, l’avènement des moyens de calculs haute performance combiné à la simulation numérique en mécanique des fluides rend aujourd’hui possible la simulation d’écoulements instationnaires et turbulents induits par des obstacles mobiles à l’échelle d’un local de travail. Dans ce contexte, ce travail est dédié à l’élaboration d’un modèle numérique basé essentiellement sur le couplage d’une approche par simulation des grandes échelles pour la turbulence et d’une méthode de pénalisation de type frontière immergée pour les obstacles mobiles. Ce modèle numérique permettra alors l’étude et l’analyse quantitative de l’impact des perturbations aérauliques sur les dispositifs de confinement dynamique. Une première partie de ce travail consiste d’abord à effectuer des vérifications et des validations des différentes modélisations couplées. Le modèle numérique est ensuite utilisé pour réaliser des simulations numériques instationnaires et turbulentes du passage d’un obstacle mobile devant une sorbonne de laboratoire en fonctionnement, dans un volume représentatif d’un local de travail en laboratoire. Enfin, les résultats de ces simulations sont confrontés à des mesures d’efficacité de confinement, réalisées sur une expérience de laboratoire de taille réell

Numerical simulations of air and pollutant flows induced by the movement of a person : effects on dynamic containment devices

Les dispositifs d’extraction de vapeurs toxiques de produits utilisés lors de manipulation, telles que les sorbonnes de laboratoire, sont massivement employés pour protéger les manipulateurs. Ces dispositifs sont basés sur un système de ventilation générant un écoulement d’air d’aspiration qui doit assurer le confinement et l’extraction des polluants gazeux. Or, les personnes qui utilisent ces dispositifs induisent, par leur mouvement, des perturbations aérauliques qui sont fondamentalement instationnaires et turbulentes, pouvant alors impacter, parfois gravement, le fonctionnement de ces dispositifs de protection. Bien que soit connue leur vulnérabilité lorsqu’ils sont exposés à ces perturbations, il n’existe pas à l’heure actuelle de moyens d’évaluer quantitativement leur impact. Cela dit, l’avènement des moyens de calculs haute performance combiné à la simulation numérique en mécanique des fluides rend aujourd’hui possible la simulation d’écoulements instationnaires et turbulents induits par des obstacles mobiles à l’échelle d’un local de travail. Dans ce contexte, ce travail est dédié à l’élaboration d’un modèle numérique basé essentiellement sur le couplage d’une approche par simulation des grandes échelles pour la turbulence et d’une méthode de pénalisation de type frontière immergée pour les obstacles mobiles. Ce modèle numérique permettra alors l’étude et l’analyse quantitative de l’impact des perturbations aérauliques sur les dispositifs de confinement dynamique. Une première partie de ce travail consiste d’abord à effectuer des vérifications et des validations des différentes modélisations couplées. Le modèle numérique est ensuite utilisé pour réaliser des simulations numériques instationnaires et turbulentes du passage d’un obstacle mobile devant une sorbonne de laboratoire en fonctionnement, dans un volume représentatif d’un local de travail en laboratoire. Enfin, les résultats de ces simulations sont confrontés à des mesures d’efficacité de confinement, réalisées sur une expérience de laboratoire de taille réelleDevices for extracting toxic vapours from substances used during manipulation, such as laboratory fume cupboards, are widely used to protect the operators. These devices are based on a ventilation system generating a flow generating suction air to provide containment and extraction of the gaseous pollutants. However, people using these devices induce, by their movements, aerodynamic disturbances which are fundamentally unsteady and turbulent, potentially impacting, often severely, the performance of these protection devices. While their vulnerability when exposed to these disturbances is known, there is currently no available way to quantitatively assess their impact. That said, the emergence of high-performance computation capabilities combined with numerical simulation in fluid mechanics now makes it possible to simulate unsteady and turbulent flows induced by moving obstacles at the scale of a work space. In this context, this work is dedicated to the development of a numerical model essentially based on the combination of a large eddy simulation approach for turbulence and a immersed boundary method for moving obstacles. This numerical model will then allow the study and quantitative analysis of the impact of aerodynamic disturbances on dynamic containment devices. A first part of this work consists, first of all, in carrying out verifications and validations of the different coupled modelling. The numerical model is then used to carry out unsteady and turbulent numerical simulations of the movement of a mobile obstacle in front of a laboratory fume cupboard in use, in a typical size of a laboratory work room. Finally, the results of these simulations are compared with measures of containment efficiency, carried out on a full-scale laboratory experimen