Objective investigation of discomfort due to draught in a tangential air distribution system: Influence of air diffuser’s offset ratio

Both, Balázs; Szánthó, Zoltán

doi:10.1177/1420326x17702703

Cited by 6 publications

(4 citation statements)

References 20 publications

(23 reference statements)

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“…The inlet Archimedes number (Ar i ) [47,48] is a measure of the relative importance of buoyant and inertia forces. Ar i is important in building airflows because it combines two important ventilation design parameters, i.e., supply air velocity and room temperature difference.…”

Section: Theory and Mathematical Modelsmentioning

confidence: 99%

Experimental Investigation of the Ventilation Performance of Different Air Distribution Systems in an Office Environment—Cooling Mode

et al. 2019

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The performance of a newly designed corner impinging jet air distribution method with an equilateral triangle cross section was evaluated experimentally and compared to that of two more traditional methods (mixing and displacement ventilation). At nine evenly chosen positions with four standard vertical points, air velocity, turbulence intensity, temperature, and tracer gas decay measurements were conducted for all systems. The results show that the new method behaves as a displacement ventilation system, with high air change effectiveness and stratified flow pattern and temperature field. Both local air change effectiveness and air exchange effectiveness of the corner impinging jet showed high quality and promising results, which is a good indicator of ventilation effectiveness. The results also indicate that there is a possibility to slightly lower the airflow rates for the new air distribution system, while still meeting the requirements for thermal comfort and indoor air quality, thereby reducing fan energy usage. The draught rate was also lower for corner impinging jet compared to the other tested air distribution methods. The findings of this research show that the corner impinging jet method can be used for office ventilation.Energies 2019, 12, 1354 2 of 15 the average IAQ in the occupied zone, and the results showed that there was a 35-50% improvement in the breathing zone due to the buoyancy effect around the mannequin body [4]. In a more recent publication, four different ventilation systems were compared in terms of ventilation efficiency, thermal comfort and energy-saving potential by using numerical simulations. The four systems compared were DV, mixing ventilation (MV), wall confluent jets ventilation (WCJ), and impinging jet ventilation (IJV). The comparison was done for an office environment. The results showed that DV was better than the other air delivery systems in all areas except when evaluating the vertical temperature gradient between ankle and neck levels for a standing person [5]. Other research groups have also concluded that DV is more suitable for cooling by exhibiting higher ventilation and energy effectiveness. It also creates a temperature stratification which facilitates the concentration of pollutants in the lower strata of the occupied space [6][7][8].Another type of air distribution system is IJV, which has been the subject of much research [9-13]. However, very few studies have examined multiple inlet devices based on IJV. In an early study, Karimipanah and Awbi [14] compared IJV to wall displacement ventilation in a laboratory classroom. They tested several key parameters such as ventilation efficiency, local mean age of air, and other characteristic parameters both experimentally and by numerical simulations. One of the conclusions of their research was that the IJV system showed a slight improvement in mean age of air and velocity distributions due to a better balance between buoyancy and momentum forces. Similarly, Koufi et al. [15] also reached the conclusion that IJV ha...

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Section: Theory and Mathematical Modelsmentioning

confidence: 99%

Experimental Investigation of the Ventilation Performance of Different Air Distribution Systems in an Office Environment—Cooling Mode

et al. 2019

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“…Inlet Archimedes number (Ar i ) [32,33] is a measure of the relative importance of buoyant and inertia forces. Ar i is important in building airflows because it combines two important ventilation design parameters, supply air velocity and room temperature difference.…”

Section: Theory and Mathematical Modelsmentioning

confidence: 99%

Experimental Investigation of Ventilation Performance of Different Air Distribution Systems in an Office Environment—Heating Mode

et al. 2019

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A vital requirement for all-air ventilation systems are their functionality to operate both in cooling and heating mode. This article experimentally investigates two newly designed air distribution systems, corner impinging jet (CIJV) and hybrid displacement ventilation (HDV) in comparison against a mixing type air distribution system. These three different systems are examined and compared to one another to evaluate their performance based on local thermal comfort and ventilation effectiveness when operating in heating mode. The evaluated test room is an office environment with two workstations. One of the office walls, which has three windows, faces a cold climate chamber. The results show that CIJV and HDV perform similar to a mixing ventilation in terms of ventilation effectiveness close to the workstations. As for local thermal comfort evaluation, the results show a small advantage for CIJV in the occupied zone. Comparing C2-CIJV to C2-CMV the average draught rate (DR) in the occupied zone is 0.3% for C2-CIJV and 5.3% for C2-CMV with the highest difference reaching as high as 10% at the height of 1.7 m. The results indicate that these systems can perform as well as mixing ventilation when used in offices that require moderate heating. The results also show that downdraught from the windows greatly impacts on the overall airflow and temperature pattern in the room.

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“…The inlet Archimedes number (Ar i ) [22,32] is a measure of the relative importance of buoyant and inertia forces. Ar i is important in building airflows because it combines two important ventilation design parameters, i.e., supply air velocity and room temperature difference.…”

Section: Theory and Mathematical Modelsmentioning

confidence: 99%

Experimental Evaluation of the Ventilation Effectiveness of Corner Stratum Ventilation in an Office Environment

2019

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An experimental study was conducted in a room resembling an office in a laboratory environment. The study involved investigating the ability of corner-placed stratum ventilation in order to evaluate the ventilation's effectiveness and local thermal comfort. At fixed positions, the air temperature, air velocity, turbulence intensity, and tracer gas decay measurements were carried out. The results show that corner-placed stratum ventilation behaves very similar to a mixing ventilation system when considering air change effectiveness. The performance of the system was better at lower supply air flow rates for heat removal effectiveness. For the heating cases, the draught rates were all very low, with the maximum measured value of 12%. However, for the cooling cases, the maximum draught rate was 20% and occurred at ankle level in the middle of the room.SV was proposed by Lin as a response to the requirements of some governments in East Asia for operating indoor spaces at elevated temperatures in order to conserve energy [9][10][11]. The new recommended indoor air temperatures have been set to (26-28 • C) in the Republic of Korea, (26 • C) in Chinese mainland, (25.5 • C) Hong Kong, (27 • C) Taiwan and (28 • C) in Japan for summers [12]. Since conventional ventilation systems are incapable of efficiently providing thermal neutrality in warm conditions, SV was devised to serve that purpose. The ventilation system is aimed at coping with higher room temperature and air movement and has been found suitable for cooling small to medium rooms [13]. Lin et al. [10] stated that with a properly designed supply air velocity and volume, location of diffusers and exhausts, SV has potential to maintain better thermal comfort with a smaller vertical temperature difference, lower energy use and better indoor air quality (IAQ) in the breathing zone. In addition, a comparison of the mean air temperatures in the occupied zone confirmed that SV offered the highest cooling efficiency, followed by DV, and in last place, mixing ventilation (MV) [14].SV draws on the strength of personalized ventilation systems. Personalized or task ventilation systems have been ranked as the most energy efficient and provide the best air quality in the breathing zone. However, such systems are inadequate because only limited ductwork can be installed in the occupied zone to avoid obstructions. Besides the limited ductwork, task ventilation systems cannot adequately cater for the mobile occupants within the occupied zone. SV supplies fresh air directly into the occupied zone in order to overcome the shortcomings of the task ventilation system while retaining the benefits of better indoor air quality and energy performance [15]. For example, owing to its low nonlinearity and fast response, the SV system can be used to offer differentiated air velocity, temperature and predicted mean vote (PMV) distributions to cater for individual occupant preferences in shared spaces [16,17].The underlying operation principle of the SV system is the supply of fresher air dire...

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Objective investigation of discomfort due to draught in a tangential air distribution system: Influence of air diffuser’s offset ratio

Cited by 6 publications

References 20 publications

Experimental Investigation of the Ventilation Performance of Different Air Distribution Systems in an Office Environment—Cooling Mode

Experimental Investigation of the Ventilation Performance of Different Air Distribution Systems in an Office Environment—Cooling Mode

Experimental Investigation of Ventilation Performance of Different Air Distribution Systems in an Office Environment—Heating Mode

Experimental Evaluation of the Ventilation Effectiveness of Corner Stratum Ventilation in an Office Environment

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