Numerical analysis of the methods for reducing the energy use of air-conditioning systems in non-uniform indoor environments

2020 ◽  
Vol 167 ◽  
pp. 106442 ◽  
Author(s):  
Chao Liang ◽  
Xianting Li ◽  
Xiaoliang Shao ◽  
Baoming Li
Keyword(s):  
Numerical Analysis ◽  
Air Conditioning ◽  
Energy Use ◽  
Indoor Environments ◽  
Air Conditioning Systems

A dynamic model for human thermal comfort for smart building applications

2019 ◽  
Vol 234 (4) ◽  
pp. 472-483
Author(s):  
Ghezlane Halhoul Merabet ◽  
Mohamed Essaaidi ◽  
Driss Benhaddou
Keyword(s):  
Thermal Comfort ◽  
Air Conditioning ◽  
Research Work ◽  
Comfort Level ◽  
Indoor Environments ◽  
Air Conditioning System ◽  
Human Thermal Comfort ◽  
Local Quality ◽  
Set Up ◽  
Air Conditioning Systems

Thermal comfort is closely related to the evaluation of heating, ventilation, and air conditioning systems. It can be seen as the result of the perception of the occupants of a given environment, and it is the product of the interaction of a number of personal and environmental factors. Otherwise, comfort issues still do not play an important role in the daily operation of commercial buildings. However, in the workplace, local quality effects, in addition to the health, the productivity that has a significant impact on the performance of the activities. In this regard, researchers have conducted, for decades, investigations related to thermal comfort and indoor environments, which includes developing models and indices through experimentations to establish standards to evaluate comfort and factors and set-up parameters for heating, ventilation, and air conditioning systems. However, to our best knowledge, most of the research work reported in the literature deals only with parameters that are not dynamically tracked. This work aims to propose a prototype for comfort measuring through a wireless sensor network and then presenting a model for thermal comfort prediction. The developed model can be used to set up a heating, ventilation, and air conditioning system to meet the expected comfort level. In particular, the obtained results show that there is a strong correlation between users’ comfort and variables such as age, gender, and body mass index as a function of height and weight.

Design for Sustainable Data Center Energy Use and Eco-Footprint

2010 ◽  
Author(s):  
Milton Meckler
Keyword(s):  
Data Center ◽  
Air Conditioning ◽  
Fossil Fuels ◽  
Energy Use ◽  
Data Centers ◽  
Ghg Emissions ◽  
High Energy ◽  
Operational Reliability ◽  
Energy Utilization ◽  
Air Conditioning Systems

What does remain a growing concern for many users of Data Centers is their continuing availability following the explosive growth of internet services in recent years, The recent maximizing of Data Center IT virtualization investments has resulted in improving the consolidation of prior (under utilized) server and cabling resources resulting in higher overall facility utilization and IT capacity. It has also resulted in excessive levels of equipment heat release, e.g. high energy (i.e. blade type) servers and telecommunication equipment, that challenge central and distributed air conditioning systems delivering air via raised floor or overhead to rack mounted servers arranged in alternate facing cold and hot isles (in some cases reaching 30 kW/rack or 300 W/ft2) and returning via end of isle or separated room CRAC units, which are often found to fight each other, contributing to excessive energy use. Under those circumstances, hybrid, indirect liquid cooling facilities are often required to augment above referenced air conditioning systems in order to prevent overheating and degradation of mission critical IT equipment to maintain rack mounted subject rack mounted server equipment to continue to operate available within ASHRAE TC 9.9 prescribed task psychometric limits and IT manufacturers specifications, beyond which their operational reliability cannot be assured. Recent interest in new web-based software and secure cloud computing is expected to further accelerate the growth of Data Centers which according to a recent study, the estimated number of U.S. Data Centers in 2006 consumed approximately 61 billion kWh of electricity. Computer servers and supporting power infrastructure for the Internet are estimated to represent 1.5% of all electricity generated which along with aggregated IT and communications, including PC’s in current use have also been estimated to emit 2% of global carbon emissions. Therefore the projected eco-footprint of Data Centers into the future has now become a matter of growing concern. Accordingly our paper will focus on how best to improve the energy utilization of fossil fuels that are used to power Data Centers, the energy efficiency of related auxiliary cooling and power infrastructures, so as to reduce their eco-footprint and GHG emissions to sustainable levels as soon as possible. To this end, we plan to demonstrate significant comparative savings in annual energy use and reduction in associated annual GHG emissions by employing a on-site cogeneration system (in lieu of current reliance on remote electric power generation systems), introducing use of energy efficient outside air (OSA) desiccant assisted pre-conditioners to maintain either Class1, Class 2 and NEBS indoor air dew-points, as needed, when operated with modified existing (sensible only cooling and distributed air conditioning and chiller systems) thereby eliminating need for CRAC integral unit humidity controls while achieving a estimated 60 to 80% (virtualized) reduction in the number servers within a existing (hypothetical post-consolidation) 3.5 MW demand Data Center located in southeastern (and/or southern) U.S., coastal Puerto Rico, or Brazil characterized by three (3) representative microclimates ranging from moderate to high seasonal outside air (OSA) coincident design humidity and temperature.

Fungal Contamination in Hospital Environments

2006 ◽  
Vol 27 (1) ◽  
pp. 44-47 ◽  
Author(s):  
F. Perdelli ◽  
M. L. Cristina ◽  
M. Sartini ◽  
A. M. Spagnolo ◽  
M. Dallera ◽  
...  
Keyword(s):  
Air Conditioning ◽  
Airborne Fungi ◽  
Selective Medium ◽  
Indoor Environments ◽  
Fungal Contamination ◽  
Mean Values ◽  
Hospital Environments ◽  
Airborne Concentration ◽  
Detection And Counting ◽  
Air Conditioning Systems

Objectives.To assess the degree of fungal contamination in hospital environments and to evaluate the ability of air conditioning systems to reduce such contamination.Methods.We monitored airborne microbial concentrations in various environments in 10 hospitals equipped with air conditioning. Sampling was performed with a portable Surface Air System impactor with replicate organism detection and counting plates containing a fungus-selective medium. The total fungal concentration was determined 72-120 hours after sampling. The genera most involved in infection were identified by macroscopic and microscopic observation.Results.The mean concentration of airborne fungi in the set of environments examined was 19 ± 19 colony-forming units (cfu) per cubic meter. Analysis of the fungal concentration in the different types of environments revealed different levels of contamination: the lowest mean values (12 ± 14 cfu/m3) were recorded in operating theaters, and the highest (45 ± 37 cfu/m3) were recorded in kitchens. Analyses revealed statistically significant differences between median values for the various environments. The fungal genus most commonly encountered was Penicillium, which, in kitchens, displayed the highest mean airborne concentration (8 ± 2.4 cfu/m3). The percentage (35%) of Aspergillus documented in the wards was higher than that in any of the other environments monitored.Conclusions.The fungal concentrations recorded in the present study are comparable to those recorded in other studies conducted in hospital environments and are considerably lower than those seen in other indoor environments that are not air conditioned. These findings demonstrate the effectiveness of air-handling systems in reducing fungal contamination.

scholarly journals Progressive Development and Challenges Faced by Solar Rotary Desiccant-Based Air-Conditioning Systems: A Review

Processes ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1785
Author(s):  
Ranjan Pratap Singh ◽  
Ranadip K. Das
Keyword(s):  
Solar Energy ◽  
Air Conditioning ◽  
Energy Use ◽  
Operating Cost ◽  
Electrical Energy ◽  
Low Grade ◽  
Vapor Compression ◽  
Cooling Systems ◽  
Ongoing Research ◽  
Air Conditioning Systems

A rotary desiccant-based air-conditioning system is a heat-driven hybrid system which combines different technologies such as desiccant dehumidification, evaporative cooling, refrigeration, and regeneration. This system has an opportunity to utilize low-grade thermal energy obtained from the sun or other sources. In this paper, the basic principles and recent research developments related to rotary desiccant-based cooling systems are recalled and their applications and importance are summarized. It is shown that with novel system configurations and new desiccant materials, there is great potential for improving the performance and consistency of rotary desiccant systems; at the same time, the use of solar energy for regeneration purposes can minimize the operating cost to a great extent. Some examples are presented to demonstrate how rotary desiccant air conditioning can be a promising solution for replacing traditional vapor-compression air-conditioning systems. Recent advances and ongoing research related to solar-powered hybrid rotary desiccant cooling systems are also summarized. The hybrid systems make use of a vapor-compression system in order to have better operational flexibility. These systems, although they consume electrical energy, use solar energy as the principal source of energy, and hence, significant savings of premium energy can be obtained compared to conventional vapor-compression systems. However, further research and development are required in order to realize the sustainable operation of solar rotary desiccant air-conditioning systems, as solar energy is not steady. Reductions in capital cost and size, along with improvements in efficiency and reliability of the system is still needed for it to become a player in the market of air conditioning.

scholarly journals Mixing Effectiveness of Various Damper-Plenum Configurations

2008 ◽  
Vol 42 (2008) ◽  
pp. 18-22 ◽  
Author(s):  
H. J. Sauer ◽  
P. Hande ◽  
F. Finaish
Keyword(s):  
Pressure Drop ◽  
Air Conditioning ◽  
Energy Use ◽  
Scale Validation ◽  
Velocity Ratio ◽  
Mixing Performance ◽  
Mixing Box ◽  
American Society ◽  
Air Conditioning Systems ◽  
Air Streams

Improper mixing of outside air and return air streams in building air conditioning systems has been recognized for years. The problems may lead to nuisance cycling, frequent freeze-stat trips and serious consequences of a frozen or ruptured conditioning coil. It was thought that typical solutions for the problem usually consist of preferred placement of outside air and return air duct penetrations to the mixing box, manipulation of the inlet damper angles and velocity ratio between the outside air and return air streams and the insertion of static flow mixers in the mixing box to help improve the thermal stratification. This paper reports the results of a computational fluid dynamics (CFD) study conducted as a follow-up to an experimental study conducted at the Ruskin Laboratory in Grandview, Missouri, sponsored by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). The CFD results indicated that the most significant improvement in mixing performance with minimum increase in pressure drop and energy use is achieved by expanding the mixing plenum. Effectiveness increased from 39 percent to 67 percent with less than a 0.1 inch of water additional pressure drop. However, optimization of relative plenum dimensions and baffle size and placement awaits additional CFD simulations and full scale validation.

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