A comparison of the thermal comfort performances of a radiation floor cooling system when combined with a range of ventilation systems

2019 ◽  
Vol 29 (4) ◽  
pp. 527-542 ◽  
Author(s):  
Jiying Liu ◽  
Zhuangzhuang Li ◽  
Moon Keun Kim ◽  
Shengwei Zhu ◽  
Linhua Zhang ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
Cooling System ◽  
Whole Body ◽  
Equivalent Temperature ◽  
Thermal Discomfort ◽  
Computational Fluid Dynamics Simulations ◽  
Radiant Floor Cooling System ◽  
Personalized Ventilation ◽  
Dynamics Simulations ◽  
Ventilation Systems

This study conducted a series of computational fluid dynamics simulations to evaluate the thermal comfort performance of a radiant floor cooling system when combined with different ventilation systems, including mixed ventilation (MV), stratum ventilation (SV), displacement ventilation (DV) and ductless personalized ventilation (DPV). A window temperature of 32°C and three different floor temperatures including 20, 22 and 24°C were set in summer. We used the vertical air temperature differences (VATD) at ankle and head level, the percentage of dissatisfied, the draught rate at the ankle level and the equivalent temperature as our main evaluation indices. Our results show that the VATD in DV system can reach up to about 5°C, compared with about 2°C in MV and SV systems. For the DPV system, there is only a marginal drop in the VATD. For the DV and DPV cases, with a rate of air changes per hour (ACH) of 2.4−1, we recorded a higher draught rate at the ankle level, ranging from 6.55% to 9.99%. The lower equivalent temperature values for the foot and calf segments occur when the floor temperature is 20°C. In all cases, the equivalent temperature values of the whole body indicate an acceptable level of thermal discomfort.

Optimal Minimum Airflow for Air Circulation of Single-Duct VAV Terminal Boxes

2008 ◽  
Author(s):  
Young-Hum Cho ◽  
Mingsheng Liu
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Thermal Discomfort ◽  
Variable Air Volume ◽  
Air Handling Unit ◽  
Optimal Value ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Air Circulation ◽  
The Impact

Thermal comfort in an area is directly controlled by terminal boxes in variable air volume (VAV) air-handling unit (AHU) systems. The terminal box either modulates airflow or adjusts the discharge air temperature. Reduced air circulation will cause thermal discomfort in a conditioned space if the airflow and discharge air temperature are not suitable. The objective of this study is to identify an optimal value for airflow and discharge air temperature that will maintain room thermal comfort. Optimal room airflow and discharge air temperature is analyzed, and the impact of room airflow and discharge air temperature on thermal stratification is verified through CFD (Computational Fluid Dynamics) simulations.

scholarly journals Hybrid Ventilation in an Air-Conditioned Office Building with a Multistory Atrium for Thermal Comfort: A Practical Case Study

Buildings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 625
Author(s):  
Hao-Hsiang Hsu ◽  
Wei-Hwa Chiang ◽  
Jian-Sheng Huang
Keyword(s):  
Thermal Comfort ◽  
Public Space ◽  
Office Building ◽  
Practical Case ◽  
Displacement Ventilation ◽  
Cold Air ◽  
The Public ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Stack Ventilation

This study involved a series of computational fluid dynamics simulations to evaluate the effectiveness of stack and displacement ventilation in providing better thermal comfort in an air-conditioned office building. To reduce energy consumption, the public area of the studied building is cooled by air from air-conditioned rooms with lower temperatures. The air, which is driven by buoyancy, then, flows outside through the multistory atrium. The simulation results indicated that displacement ventilation provides superior thermal comfort performance relative to stack ventilation. A design with a higher ceiling, a higher heat source and a lower inlet with cold air can substantially enhance the efficiency of displacement ventilation. Furthermore, handrails near the atrium play a crucial role because they help to retain cold air in the public space for a longer period, thereby contributing to a better predicted mean vote value.

scholarly journals Experimental investigation of occupants’ thermal sensation under a personalized ventilation system

2021 ◽  
Vol 2069 (1) ◽  
pp. 012167
Author(s):  
P Ebrahimi Naghani ◽  
S A Zolfaghari ◽  
M Maerefat ◽  
J Toftum ◽  
S M Hooshmand ◽  
...  
Keyword(s):  
Air Temperature ◽  
Cooling System ◽  
Thermal Sensation ◽  
Ventilation System ◽  
Body Part ◽  
Whole Body ◽  
Energy Costs ◽  
Air Temperatures ◽  
The Common ◽  
Personalized Ventilation

Abstract By considering the importance of providing proper indoor environment conditions for occupants and also due to energy costs, one of the solutions for indoor local air-conditioning is Personalized Ventilation System (PVS). In this paper, the occupants’ thermal sensation was experimentally studied for body segments that are mostly affected by the PVS. The local sensation of head, chest, arm, and hand at two supply air temperatures of 16 and 32°C were investigated. Eight volunteer subjects participated in this survey. The subjects reported the most thermal satisfaction on their hands. Also, the arms were the segments with the coolest thermal sensation (-1.28, between slightly cool and cold). Results indicate that the head’s thermal sensation at both supply air temperatures was neutral and the hand was the only body part that experienced warm thermal sensation during the test. Also, by increasing the supply air temperature to 32°C whole body thermal sensation changed from -0.46 to -0.09 on the seven-point scale, which means that the cooling system worked properly for occupants’ cooling. In this system, cooling occurred at 32°C instead of the common 16°C supply air temperature, which results in energy-saving and decreases annual running costs.

scholarly journals Numerical evaluation of thermal discomfort in conditions of surface heating and asymmetric radiation

2018 ◽  
Vol 9 (2) ◽  
pp. 175-179
Author(s):  
F. Kalmár ◽  
T. Kalmár
Keyword(s):  
Thermal Properties ◽  
Thermal Comfort ◽  
Winter Period ◽  
Negative Effects ◽  
Air Velocity ◽  
Thermal Discomfort ◽  
External Wall ◽  
Wall Heating ◽  
Personalized Ventilation ◽  
Radiant Temperature

This paper presents the results of analytical analysis of thermal comfort and radiation asymmetry in case of wall heating depending on the room geometry and thermal properties of the external wall. The negative effects of radiation asymmetry on thermal comfort in case of summer conditions can be lowered using advanced personalized ventilation systems. In case of buildings with poor thermal properties of the envelope during the winter period low surface temperatures may occur. The aim of this research was to analyse the thermal asymmetry in the case of a room with one external wall and wall heating installed on the opposite wall. It was assumed that the radiation asymmetry will lead to discomfort and it was hypothesised that the discomfort might be reduced increasing the air velocity. The results have proven that thermal asymmetry in the middle of the room will not lead to thermal discomfort even for walls without any additional thermal insulation. However, the mean radiant temperature varies significantly depending on the position of the occupant in the room. In this case, the personalized control on the air velocity can help to improve the thermal comfort conditions.

scholarly journals Thermal Comfort Aspects of Solar Gains during the Heating Season

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1702 ◽  
Author(s):  
Ferenc Kalmár ◽  
Tünde Kalmár
Keyword(s):  
Thermal Comfort ◽  
Energy Use ◽  
Winter Season ◽  
Diffuse Radiation ◽  
Heating Season ◽  
Negative Effects ◽  
Thermal Discomfort ◽  
Wet Bulb Globe Temperature ◽  
Globe Temperature ◽  
Personalized Ventilation

Glazing plays a key role in the energy balance of buildings. The aim of this paper is to enlighten the thermal discomfort caused by large glazed areas in the heating season and to point out a possible solution that can provide proper thermal comfort with low energy use. It is unusual to discuss the negative effects of solar gains on thermal comfort during the heating season. However, there are cases when glazing may lead to unforeseen indoor thermal discomfort conditions. Laboratory and on site measurements were performed in order to assess thermal discomfort caused by direct and diffuse radiation. It was shown that the WBGT (Wet Bulb Globe Temperature) index may exceed even 30 °C in the winter season in a room having large glazed area oriented to east. Laboratory tests performed in climate chamber have shown that the high PMV values cannot be reduced below 1.0, increasing the air change rate in the room. Using opaque drapes, the WBGT index was reduced by 2 °C, but the daylighting decreased substantially. It was demonstrated that by using advanced personalized ventilation systems, the appropriate thermal comfort can be provided avoiding the reduction of daylighting.

scholarly journals Experimental and numerical investigations of cooling drag

2017 ◽  
Vol 231 (9) ◽  
pp. 1203-1210
Author(s):  
Teddy Hobeika ◽  
Simone Sebben ◽  
Lennart Löfdahl
Keyword(s):  
Velocity Distribution ◽  
Aerodynamic Drag ◽  
Cooling System ◽  
Good Prediction ◽  
Test Results ◽  
Cooling Flow ◽  
Computational Fluid Dynamics Simulations ◽  
Flow Through ◽  
Mass Flows ◽  
Dynamics Simulations

As the target figures for CO2 emissions are reduced every year, vehicle manufacturers seek to exploit all possible gains in the different vehicle attributes. Aerodynamic drag is an important factor that affects the vehicle’s fuel consumption, and its importance rises with the shift from the New European Driving Cycle to the Worldwide harmonized Light vehicles Test Cycle which has a higher average speed. In order to reduce vehicle drag, car manufacturers employ the use of grill/spoiler shutters which reduces the amount of air going through the vehicle’s cooling system, also known as cooling flow, thus reducing both its cooling capability and the resultant cooling drag. This paper investigates the influence of different grill blockages on the cooling flow through the radiator of a Volvo S60. By modifying the engine bay and radiator, load cells are used to measure the force acting on the radiator core while the velocity distribution across the radiator core is measured using pressure probes. These values are analyzed and compared to different vehicle configurations and grill inlet designs. A number of test configurations are reproduced in Computational Fluid Dynamics simulations and compared to the test results. For some grill configurations, the simulations provide a good prediction of mass flow and velocity distribution; however a clear discrepancy is present as the grill blockages increase. On the other hand, the force acting on the radiator core was well predicted for all configurations. This paper discusses the different parameters affecting cooling flow predictions such as wind tunnel blockage and measurement grid discretization by comparing radiator forces and mass flows. In addition, the changes on overall vehicle forces are discussed with the radiator force put in context with cooling drag.

scholarly journals A Comparative Study for Forced Ventilation Systems in Industrial Buildings to Improve the Workers’ Thermal Comfort

2021 ◽  
Vol 13 (18) ◽  
pp. 10267
Author(s):  
Mohamed I. Elhadary ◽  
Abdullah Mossa Y. Alzahrani ◽  
Reda M. H. Aly ◽  
Bahaa Elboshy
Keyword(s):  
Thermal Comfort ◽  
Cooling System ◽  
Volume Flow Rate ◽  
Ventilation System ◽  
Forced Ventilation ◽  
Industrial Buildings ◽  
Increase Productivity ◽  
Computational Fluid Dynamics Cfd ◽  
Spot Cooling ◽  
Ventilation Systems

The appropriate ventilation for factory spaces with regard to volume flow rate and air velocity inside the factory is one of the most important factors in the improvement of the thermal comfort of workers and in the reduction of the percentage of pollution they are exposed to, which in turn helps to improve the work environment and increase productivity. It also could improve the performance of machines. Hence, overheating can cause various problems and malfunctions. In this study, three types of mechanical ventilation systems are compared: the wall fan extract ventilation system, the roof fan extract ventilation system, and the spot cooling system. The Ansys software has been used to conduct the computational fluid dynamics (CFD) simulations for the different cases and the ventilation effectiveness factor (VEF) has been used to compare the performances of the three systems. The ventilation factor notably relies on the temperature distribution produced through the modeling and the results show that the most optimal system that can be used for similar factory spaces is the forced ventilation system. Finally, it is also the best in terms of energy consumption, despite the increase in the initial cost of its installation.

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