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.

Increasing Energy Efficiency of HVAC Systems of Buildings Using Phase Change Material

2011 ◽  
Author(s):  
Lee Chusak ◽  
Jared Daiber ◽  
Ramesh Agarwal
Keyword(s):  
Thermal Comfort ◽  
Phase Change ◽  
Phase Change Material ◽  
Energy Requirements ◽  
Exterior Wall ◽  
Displacement Ventilation ◽  
Cooling Systems ◽  
Comfort Levels ◽  
Chilled Ceiling ◽  
Change Material

Using Computational Fluid Dynamics (CFD), four 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) a combined air and hydronic radiant system (overhead system with a chilled ceiling), (c) an all-air raised floor system (displacement ventilation), and (d) a combined air and hydronic radiant system (displacement ventilation with a chilled ceiling). The computational domain for each model consists of one temperature varying wall (simulating the temperature of the exterior wall of the building during a 24-hour period) and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room). Two sets of computations are conducted. The first set considers a glass window and plastic shade configuration for the exterior wall to compare the four cooling systems. The second set of computations consider a glass window, a phase change material layer and the plastic shade configuration for the exterior wall to examine the effect of the phase change material (PCM) layer on the cooling energy requirements. Both sets of simulations assumed an external wall that changed temperature as a function of time simulating the temperature changes on the exterior wall of the room during a 24 hour period. Results show superior thermal comfort levels as well as substantial energy savings can be accrued using the displacement ventilation and especially the displacement ventilation with a chilled ceiling over the conventional overhead mixing ventilation system. The results also show that the addition of a PCM layer to the exterior wall can significantly decrease the cooling energy requirements.

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.

scholarly journals Housing retrofit as an intervention in thermal comfort practices: Chinese and Dutch householder perspectives

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Frank J. de Feijter ◽  
Bas J.M. van Vliet
Keyword(s):  
Thermal Comfort ◽  
Low Income ◽  
Financial Incentives ◽  
Energy Demand ◽  
Energy Savings ◽  
Qualitative Interviews ◽  
Technical Standards ◽  
Comfort Levels ◽  
Adaptive Thermal Comfort ◽  
The One

AbstractContemporary packages of housing retrofit equipment are based on models of expected energy savings with regard to globally standardized thermal comfort levels. Previous research shows that the energy savings realised after a housing retrofit is substantially lower than expected. Attempts to reduce energy demand by physical re-design, utilising technical standards for thermal comfort as well as financial incentives, tend to ignore the role of retrofit interventions in the construction of everyday practices of thermal comfort making. Thermal comfort practices of heating, cooling and ventilation are moderated by specific householders’ motivations which constitute ‘wants’ and emerging ‘needs’ in the interaction with the housing retrofit equipment. This paper proposes that the interactions between the retrofitted buildings and the householders are the sum of material affordances, as signified by the design of the housing equipment on the one hand, and the practical affordances in practices-as-performances on the other. The study presents comfort practices in relation to recently retrofitted low-income housing estates in Beijing, Mianyang (Sichuan province, South-west China) and Amsterdam on the basis of 50 qualitative interviews with householders in each city. The paper concludes that the expected energy saving is counteracted by a poor match between conventional retrofit packages and householders’ considerations about their thermal comfort. To better reduce energy demand and to mitigate energy poverty, retrofit packages should provide adaptive thermal comfort as preferred by householders, rather than fixed or tightly specified thermal comfort. Such a perspective may support a more flexible and inclusive use of housing equipment as part of retrofit programs.

scholarly journals Assessment age of air and thermal comfort in a classroom by adopting displacement ventilation with chilled ceiling system

2021 ◽  
Vol 9 (ICRIE) ◽  
Author(s):  
Ali Aedan Shbeeb ◽  
◽  
Ala'a Abbas Mahdi ◽  
Ahmed Kadhim Hussein ◽  
◽  
...  
Keyword(s):  
Load Ratio ◽  
Comfort Level ◽  
Airflow Rate ◽  
Cooling Load ◽  
Displacement Ventilation ◽  
Comfort Levels ◽  
The Mean ◽  
Chilled Ceiling ◽  
Increasing Load ◽  
Air Exchange

This study aims to investigate the effect of the cooling load ratio covered by the chilled ceiling on the age of air and comfort level in a classroom in a hot and dry climate in Iraq-Hilla city. Air age, air exchange efficiency, and concentrations of pollutants in a classroom are investigated numerically by used AIRPAK software under displacement ventilation combined with a chilled ceiling system. Four cases are studied at different values of the cooling load covered by the chilled ceiling (0%, 25%, 50%, 80%) with respect to total classroom cooling load. Cooling load removes by chilled ceiling varied from (0 to 84.5 W/m2) based on the classroom area, and its temperature varied between (17.5-22.5oC). The displacement ventilation airflow rate was kept at 0.3m3/s, and the air temperature supply varied between (19.5-24.5oC) depend on the amount of cooling load covered by displacement ventilation. The results showed that the mean local air age increasing with height. The room mean air age increase and air exchange efficiency reduce with increasing load portion, which treated by the chilled ceiling. Increasing the portion of the load treated by chilled ceiling tends to improve comfort levels.

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.

Energy Use Comparison of Air Distribution Systems Serving a Section of a School Building

2012 ◽  
Author(s):  
Stillman Jordan ◽  
Randall D. Manteufel
Keyword(s):  
Total Energy ◽  
Distribution System ◽  
Energy Recovery ◽  
Distribution Systems ◽  
Energy Savings ◽  
Ventilation System ◽  
Space Distribution ◽  
Air Distribution ◽  
Displacement Ventilation ◽  
Humid Climate

An optimal air distribution design accomplishes both comfort and ventilation requirements while consuming as little energy as possible. This paper analyzes four different air distribution systems and technologies including single duct variable air volume air handlers, chilled beam cooling systems, total energy recovery wheels, displacement ventilation, and dedicated outside air systems; in an effort to determine the best air distribution system for a representative section of a school in hot and humid climate. The effectiveness of the air distribution systems is evaluated by analyzing how the different technologies take advantage of the natural convective properties of air to create a comfortable environment for the occupied region of the space. Distribution effectiveness and energy consumption must be weighed against considerations such as system complexity and ease of operation. This paper compares several alternative air distribution systems to a baseline single inlet VAV system that is commonly used in new schools designed today. Calculations show that the total energy recovery wheels result in a 16% energy savings over the baseline air distribution system because of the large amount of outside air required in school buildings. Chilled beams are not well suited for schools because of the large amount of outside air required by the space and the sophisticated design and operation needed to prevent condensation from occurring at the chilled beam. The results show that the air distribution system that consumes the least amount of energy is a displacement ventilation system. The system also inherently promotes better indoor air quality as it allows air to naturally rise out and return out of the space with minimal mixing of contaminates that may be recirculated within the room for others to breath. The displacement ventilation system’s overall energy savings of 20% over the baseline is mainly attributed to its total energy recovery wheel and the system’s ability to drastically reduce the cooling load seen by the air cooled chiller by effectively ventilating spaces using less outside air.

Subjective Evaluation of Thermal Comfort Using an Air Recirculation Device

1983 ◽  
Vol 27 (8) ◽  
pp. 751-756
Author(s):  
David A. VanDyke ◽  
Frederick H. Rohles ◽  
Michael P. Webster
Keyword(s):  
Thermal Comfort ◽  
Energy Demand ◽  
Energy Savings ◽  
Rating Scale ◽  
Thermal Sensation ◽  
Subjective Evaluation ◽  
Comfort Level ◽  
National Bureau ◽  
Environmental Laboratory ◽  
Fan Speed

To determine the effectiveness of a small fan in enhancing thermal comfort in an open office, eight subjects were studied at 24.4 C (76F), 26.1 C (79F), and 27.8 C (82F) (all at 50% RH), in an environmental laboratory where each workstation was equipped with a small variable speed fan. Control trials were run at all three temperatures without the use of the fan. Three subjective responses were measured: thermal sensation (a nine category rating scale), thermal comfort (a seven pair semantic differential scale), and temperature preference. During fan tests, subjects were allowed to adjust the fan speed to their preference at 15 minute intervals. Results showed that use of the fan could allow a 3°F temperature increase while maintaining the same comfort level, or increase comfort at temperatures of 79°F and up. The 3°F increase in temperature would result in a 9% energy savings, based on the National Bureau of Standards suggestion of a reduction in air conditioning energy demand of 6% per °C or 3% per °F. The study also shows that users prefer a fan that is adjustable in speed and placement.

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