scholarly journals Effect of supply air temperature on conservation of energy in air conditioning of space

2011 ◽  
pp. 51-54
Author(s):  
V. N. Bartari ◽  
S. P. S. Rajput
Keyword(s):  
Air Temperature ◽  
Distribution System ◽  
Energy Savings ◽  
Thermal Environment ◽  
Temperature Sensors ◽  
Air Distribution ◽  
Conservation Of Energy ◽  
Buoyancy Flow ◽  
Flow Energy ◽  
The Impact

In HVAC applications, huge amount of energy is utilized in fans and blowers to maintain the flow. In this paper energy savings associated with air distribution is discussed. In a most commonly used air distribution system, uniform thermal environment in the occupied space is established. An alternative to this method is the under floor air distribution system (UFAD) which is in its fantasy state. Thermal stratification can be established in this method due to the buoyancy flow of the air. In this paper assessment of the impact of temperature sensors in energy savings is done in UFAD system. It is observed that by the placement of temperature sensors in the occupied space, supply air temperature can be controlled while maintaining the comfort conditions. By optimal conditions of the temperature and volume flow, energy savings can be achieved due to reduction in energy requirements in refrigeration and ventilation. The comfort criteria of ASHRAE standard 55-92 is taken.

Effects of Human Gait on Air Distribution in Contagious Isolation Tent Wards

2013 ◽  
Vol 380-384 ◽  
pp. 1770-1773
Author(s):  
Gao Feng Wei ◽  
Zhan Shu ◽  
Gang Tang
Keyword(s):  
Air Pollution ◽  
Air Temperature ◽  
Pollution Control ◽  
Three Dimensions ◽  
Human Gait ◽  
Air Distribution ◽  
Air Pollution Control ◽  
Air Velocity ◽  
The Impact ◽  
Contaminant Distribution

The purpose of this study was to investigate the effects of human gait on air distribution in contagious isolation tent wards. The proposed contagious isolate tent wards were designed as the operating room for serious paroxysmal infectious patients. The three dimensions model of contagious isolation tent ward was reconstructed. Then, the computed fluid dynamical (CFD) methods were used to simulate and analyze the air distribution of contagious isolation tent ward. The dynamical meshes technology was employed to simulate the human gait. An experiment was implemented to measure air velocity of the proposed isolate tent ward. The results showed that the human gait motion affects air pressure, air velocity and contaminant distribution, while the impact on air temperature could be ignored. It was concluded that the impact of human gait or movements should be taken into account in air pollution control of contagious isolation tent wards.

Impact of Optimal Discharge Air Temperature and Minimum Airflow

2009 ◽  
Author(s):  
Young-Hum Cho ◽  
Young-hoon Jung ◽  
Mingsheng Liu
Keyword(s):  
Air Temperature ◽  
Thermal Stratification ◽  
Room Temperature ◽  
Energy Savings ◽  
The Other ◽  
Waste Energy ◽  
Heating Load ◽  
Save Energy ◽  
Air Circulation ◽  
The Impact

Airflow and discharge air temperature can be varied to maintain room temperature setpoint according to heating load. Increasing discharge air temperature and the decreasing airflow can save energy, but it causes reduced air circulation as supply air temperature rises above the space temperature. On the other hand, increasing airflow can improve air circulation; however, it may waste energy. The objective of this study is to identify the correlation between the minimum airflow and discharge air temperature that will maintain room thermal comfort. Optimal room airflow and discharge air temperature were analyzed, and the impact of room airflow and discharge air temperature on thermal stratification was evaluated and potential energy savings was estimated. Its performance was conducted through field experiment.

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.

CFD-Based Parametric Analysis on the Performance of Personalized Partition Air Distribution Systems

Solar Energy ◽  
2006 ◽  
Author(s):  
Kybum Jeong ◽  
Moncef Krarti ◽  
Zhiqiang Zhai
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Distribution System ◽  
Distribution Systems ◽  
Comfort Level ◽  
Cfd Modeling ◽  
Air Distribution ◽  
Air Velocity ◽  
Comfort Index ◽  
System Mode

The partition air distribution systems evaluated in this study allow occupants to control the system mode (on/off) and the supply air velocity and direction with similar flexibility as occupants in automobiles. To find optimal specifications for the partition air distribution systems that are able to achieve comfortable micro-environment, a CFD modeling tool was used to simulate the airflow and thermal performance of the partition air distribution systems in a typical office space. By analyzing the distribution characteristics of indoor air temperature, air velocity and thermal comfort index, the study assessed the performance of the partition air distribution systems with different operating parameters. The simulation results were analyzed and evaluated to assess both occupant’s thermal comfort and system energy consumption. The study shows that space cooling energy can be reduced while maintaining acceptable indoor thermal comfort level using a partition air distribution system with a higher supply air temperature.

scholarly journals Thermal and Geometric Controls on the Rate of Surface Air Temperature Changes in a Medium-Sized, Midlatitude City

2007 ◽  
Vol 46 (2) ◽  
pp. 241-247 ◽  
Author(s):  
Tomohiko Tomita ◽  
Hiroyuki Kusaka ◽  
Ryo Akiyoshi ◽  
Yoshiyuki Imasato
Keyword(s):  
Time Dependence ◽  
Air Temperature ◽  
Urban Areas ◽  
Mesoscale Model ◽  
Thermal Environment ◽  
Surface Air Temperature ◽  
Anthropogenic Heat ◽  
View Factor ◽  
Temperature Changes ◽  
The Impact

Abstract Gradual cooling in the evening forms a wintertime nocturnal urban heat island. This work, with a mesoscale model involving urban canopy physics, is an examination of how four thermal and geometric controls—anthropogenic heat QF, heat capacity C, thermal conductivity k, and sky-view factor ψs—modify the rate of surface air temperature changes ΔT/Δt. In particular, the time dependence is diagnosed through numerical experiments. The controls QF and k are major agents in the evening, when QF changes the evening ΔT/Δt linearly and k is logarithmic. The effects of C and ψs are large in the morning and in the afternoon with those of k. The impact of QF is, however, substantial only in the evening. Because the time dependence of C and k is different, the thermal inertia used as a parameter in the urban climate studies should be divided into two parameters: C and k. To improve the thermal environment in urban areas, the modification of QF and k could be effective.

A sustainable localised air distribution system for enhancing thermal environment and indoor air quality of poultry house for semiarid region

2021 ◽  
Vol 203 ◽  
pp. 70-92
Author(s):  
Douaa K. Al Assaad ◽  
Mohamad S. Orabi ◽  
Nesreen K. Ghaddar ◽  
Kamel F. Ghali ◽  
Darine A. Salam ◽  
...  
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Distribution System ◽  
Thermal Environment ◽  
Air Distribution ◽  
Semiarid Region ◽  
Poultry House

scholarly journals The effect of a density gradient in groundwater on ATES system efficiency and subsurface space use

2018 ◽  
Vol 45 ◽  
pp. 85-103
Author(s):  
Martin Bloemendal ◽  
Theo N. Olsthoorn
Keyword(s):  
Thermal Energy ◽  
Energy Savings ◽  
Salinity Gradient ◽  
Primary Energy ◽  
Density Gradients ◽  
Buoyancy Flow ◽  
Heating And Cooling ◽  
Vertical Hydraulic Conductivity ◽  
The Impact ◽  
Research Show

Abstract. A heat pump combined with Aquifer Thermal Energy Storage (ATES) has high potential in efficiently and sustainably providing thermal energy for space heating and cooling. This makes the subsurface, including its groundwater, of crucial importance for primary energy savings. ATES systems are often placed in aquifers in which salinity increases with depth. This is the case in coastal areas where also the demand for ATES application is high due to high degrees of urbanization in those areas. The seasonally alternating extraction and re-injection between ATES wells disturbs the preexisting ambient salinity gradient causing horizontal density gradients, which trigger buoyancy flow, which in turn affects the recovery efficiency of the stored thermal energy. This section uses analytical and numerical methods to understand and explain the impact of buoyancy flow on the efficiency of ATES in such situations, and to quantify the magnitude of this impact relative to other thermal energy losses. The results of this research show that losses due to buoyancy flow may become considerable at (a relatively large) ambient density gradients of over 0.5 kg m−3 m−1 in combination with a vertical hydraulic conductivity of more than 5 m day−1. Monowell systems suffer more from buoyancy losses than do doublet systems under similar conditions.

scholarly journals Auxiliary Draught Base Performance Improvement of Air Distribution System of Cold Store

2019 ◽  
Vol 8 (4) ◽  
pp. 4737-4748
Keyword(s):  
Heat Transfer ◽  
Flow Velocity ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Cold Storage ◽  
Distribution System ◽  
Storage System ◽  
Air Transport ◽  
Air Distribution ◽  
The Impact

Air distribution enable convective heat transfer in cold storage operation. Thermal behaviors of the cold storage system are based on air transport arrangements. Transport characteristics can handle with auxiliary arrangements such as induce draught system. Experimental investigation for the impact of auxiliary draught system (ADS) on air transportation is carried out. Air transport velocity was measured in the cold chamber with a hot wire anemometer. Experimental results show significant enhancement by three times mid-section air flow velocity and overall one- and half-time greater flow velocity observed, while return air velocity measured almost tow time of general condition during the experiment. COP of plant improve by 21% with 25% less time required to achieve desired temperature. 26% saving in power consumption observed during experiments. Auxiliary draught ensures homogeneous environment inside the plant through proper mixing of air and support convective heat transfer. Designing and analysis of airflow patterns with temperature distribution in large entity like cold storage is a difficult task thus Computational Fluid Dynamics (CFD) can address the issue with high degree of precision. It has been observed that SST K-ℇ model has average 26% error with experimental values

Assessment of thermal comfort in high-occupancy spaces with relevance to air distribution schemes: A case study of mosques

2018 ◽  
Vol 39 (5) ◽  
pp. 572-589 ◽  
Author(s):  
S Samiuddin ◽  
Ismail M Budaiwi
Keyword(s):  
Thermal Comfort ◽  
Performance Index ◽  
Distribution System ◽  
Thermal Environment ◽  
Terminal Velocity ◽  
Air Distribution ◽  
Human Thermal Comfort ◽  
Index Value ◽  
Air Diffusion

In high-occupancy intermittently operated buildings such as mosques and auditoriums, maintaining an acceptable thermal environment may present a challenging task. Variations in the operation and the thermal loads can result in variable and non-uniform thermal comfort conditions when the HVAC system is not properly designed. Non-uniformity of the thermal environment is greatly influenced by the design and scheme of the air distribution system. Mosques, with their distinctive five intermittent short occupancies and the non-fixed posture of occupants, present a unique case for investigation. In this study, the effect of air distribution of various schemes of a ceiling-based system on the thermal comfort in mosques is investigated. Air diffusion performance index and Fanger’s PMV method are used to assess thermal comfort. Three air distribution schemes at four diffuser terminal velocities were studied using the EnergyPlus and computational fluid dynamics techniques. Results indicate major variations in air diffusion performance index with each air distribution scheme type and diffuser terminal velocity. The uniformity of the PMV was entirely dependent on the air diffusion performance index value and exhibited large variations when the air diffusion performance index value was low. In most cases, the space was overcooled with an average PMV of −0.66 or below. Practical application: The effect of air distribution system design on human thermal comfort has been very complex to understand, as it involves different schemes and different diffuser discharge velocities. This study will help engineers and designers in designing better thermal environment for the occupants.

scholarly journals Survey on thermal environments in bathrooms and elderly behavior while bathing in old residential buildings in Nanjing, China

2020 ◽  
Vol 172 ◽  
pp. 15009
Author(s):  
Pengcheng Shi ◽  
Yonghui Li ◽  
Yuan Ying ◽  
Shuichi Hokoi
Keyword(s):  
Blood Pressure ◽  
Air Temperature ◽  
Thermal Environment ◽  
Residential Buildings ◽  
The Elderly ◽  
Personal Factors ◽  
Physiological Models ◽  
Thermal Environments ◽  
Daily Behavior ◽  
The Impact

Bathing is a typical daily behavior among Chinese elderly people, which causes large thermal environmental fluctuations especially in winter. Rapid fluctuations of the thermal environment can lead to a drastic change in human blood pressure and may cause accidents while bathing. The most common style of Chinese bathing is showers. Information on the thermal environment during bathing is limited, making analysis difficult. This study aims to understand the current situation of bathing in old residences in Nanjing, China. To examine elderly bathing behaviors and thermal environments in bathrooms during bathing, we monitored the thermal environment in three elderly families and administered a questionnaire survey from which 49 responses were obtained. Results were categorized into environmental and personal factors that affect blood pressure during bathing. In winter, the temperature in a bathroom is often below 10℃. A heating device is installed close to the head (87%); thus, the thermal environment is vertically non-uniform (air temperature difference often exceeds 10℃). Most elderly individuals bathe for less than 30 minutes and the rise in air temperature often exceeds 10℃. This information will be used as the boundary conditions for thermo-physiological models that can quantitatively assess the impact of the environment on the elderly, and for the renovation of bathrooms.

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