scholarly journals Effectiveness of Chilled ceiling assisted by intermittent personalized ventilation for active contaminants’ confinement and energy savings

2019 ◽  
Vol 17 ◽  
pp. 405-410
Author(s):  
D. Al Assaad ◽  
◽  
K. Ghali ◽  
N. Ghaddar
Keyword(s):  
Energy Savings ◽  
Personalized Ventilation ◽  
Chilled Ceiling

Effective Mixed-Mode Ventilation System With Intermittent Personalized Ventilation for Improving Thermal Comfort in an Office Space

2020 ◽  
Author(s):  
Elvire Katramiz ◽  
Nesreen Ghaddar ◽  
Kamel Ghali
Keyword(s):  
Thermal Comfort ◽  
Control Strategy ◽  
Mixed Mode ◽  
Natural Ventilation ◽  
Energy Savings ◽  
Ventilation System ◽  
Energy Performance ◽  
Building Performance Simulation ◽  
Office Space ◽  
Personalized Ventilation

Abstract The mixed-mode ventilation (MMV) system is an energy-friendly ventilation technique that combines natural ventilation (NV) with mechanical air conditioning (AC). It draws in fresh air when the outdoor conditions are favorable or activates otherwise the AC system during occupancy hours. To improve performance of the MMV system, it is proposed to integrate it with an intermittent personalized ventilation (IPV) system. IPV delivers cool clean air intermittently to the occupant and enhances occupant thermal comfort. With the proper ventilation control strategy, IPV can aid MMV by increasing NV mode operational hours, and improve the energy performance of the AC system by relaxing the required macroclimate set point temperature. The aim of this work is to study the IPV+MMV system performance for an office space application in terms of thermal comfort and energy savings through the implementation of an appropriate control strategy. A validated computational fluid dynamics (CFD) model of an office space equipped with IPV is used to assess the thermal fields in the vicinity of an occupant. It is then coupled with a transient bio-heat and comfort models to find the overall thermal comfort levels. Subsequently, a building-performance simulation study is performed using Integrated Environmental Solutions-Virtual Environment (IES-VE) for an office in Beirut, Lebanon for the typical summer month of July. An energy analysis is conducted to predict the savings of the suggested design in comparison to the conventional AC system. Results showed that the use of IPV units and MMV significantly reduced the number of AC operation hours while providing thermal comfort.

Reducing Energy Demand in Commercial Buildings: Balancing Convection and Radiant Cooling

2010 ◽  
Author(s):  
Lee Chusak ◽  
Andrew Harris ◽  
Ramesh Agarwal
Keyword(s):  
Thermal Comfort ◽  
Energy Demand ◽  
Energy Savings ◽  
Ventilation System ◽  
Computational Domain ◽  
Exterior Wall ◽  
Displacement Ventilation ◽  
Comfort Levels ◽  
Isothermal Wall ◽  
Chilled Ceiling

Using Computational Fluid Dynamics (CFD) software, three different cooling systems used in contemporary office environments are modeled to compare energy consumption and thermal comfort levels. Incorporating convection and radiation technologies, full-scale models of an office room compare arrangements for (a) an all-air overhead system (mixing ventilation), (b) an all-air raised floor system (displacement ventilation), and (c) a combined air and hydronic radiant system (displacement ventilation with a chilled ceiling). The computational domain for each model consists of one isothermal wall (simulating an exterior wall of the room) and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room). Two sets of computations were conducted. The first set of computations utilized a constant temperature isothermal exterior wall, while the second set utilized an isothermal wall that changed temperatures as a function of time simulating the temperature changes on the exterior wall of a building throughout a 24 hour period. Results show superior thermal comfort levels as well as substantial energy savings can be accrued using the displacement ventilation, especially the displacement ventilation with a chilled ceiling over the conventional mixing ventilation system.

Effectiveness of Intermittent Personalized Ventilation Assisting Chilled Ceiling in Protecting Occupants Against Active Particles

2019 ◽  
Author(s):  
Douaa Al-Assad ◽  
Nesreen Ghaddar ◽  
Kamel Ghali
Keyword(s):  
Particle Diameter ◽  
Operating Conditions ◽  
Thermal Manikin ◽  
Breathing Zone ◽  
Pv System ◽  
Active Particles ◽  
Comfort Levels ◽  
Office Space ◽  
Personalized Ventilation ◽  
Chilled Ceiling

Abstract In this work, an intermittent personalized ventilation (PV) system was coupled with a chilled ceiling system in an office space. The ability of this system in protecting occupants from active particulate matter due to an indoor contamination source was investigated. To perform this study, a 3D transient computational fluid dynamics model was used to determine the velocity, thermal, and particle concentration fields in the space. The fluid flow in the space was experimentally validated in previous works in a climatic chamber equipped with a thermal manikin representing an occupant in an office space. The validated model was used to perform a parametric study varying the intermittent PV operating frequency as well as the particle diameter. The results were used to recommend PV operating conditions, which would ensure the protection of occupant against the contaminants present in the macroclimate and deposited on nearby surfaces. It was found that the intermittent PV should operate at an average flow rate of 7.5 L/s and a frequency of 0.73 Hz. These conditions provided acceptable values of intake fraction in the breathing zone and surrounding microclimate and acceptable deposited fractions. Moreover, these conditions provided good thermal comfort levels (0.86: comfortable) and good protection against passive contaminants (εv,BZ = 64 %).

Thermal Comfort and Energy Savings in a Simulated Office Conditioned by a Transient Personalized Ventilator and a Displacement Ventilation System

2020 ◽  
Author(s):  
Douaa Al Assad ◽  
Kamel Ghali ◽  
Nesreen Ghaddar ◽  
Elvire Katramiz
Keyword(s):  
Thermal Comfort ◽  
Energy Savings ◽  
Ventilation System ◽  
Rate Of Change ◽  
Comfort Level ◽  
Thermal Manikin ◽  
Cfd Model ◽  
Displacement Ventilation ◽  
Additional Energy ◽  
Personalized Ventilation

Abstract The aim of this work is to evaluate the performance of an intermittent personalized ventilation (IPV) system assisting a displacement ventilation (DV) system to improve thermal comfort and save energy. This will be conducted by developing a transient 3D computational fluid dynamics (CFD) model of an occupied office space equipped with systems. The occupant is modeled by a heated thermal manikin replicating the human body. The CFD model is coupled with a transient bio-heat model to compute segmental skin temperatures and their rate of change. The latter are taken as input into Zhang’s comfort model to predict and overall thermal comfort. The model was used to conduct a case study, where the overall thermal comfort and energy savings will be assessed for the IPV + DV These results will be compared with those of steady personalized ventilation (PV) + DV and standalone DV systems. By varying the IPV frequency in the typical indoor range of [0.3 Hz – 1 Hz], it was found that the IPV + DV system was able to enhance comfort compared to steady PV + DV and a standalone DV. In addition, an energy analysis was conducted and it was shown that the IPV was able to achieve considerable energy savings compared to a steady PV + DV at the same thermal comfort level. Moreover, relaxing the DV supply temperature to higher occupied zone temperatures, can provide additional energy savings while still maintaining comfort levels in the space.

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