Here we present a field study examining the impact of elevated room temperature and air movement on thermal comfort and self-reported productivity. This experiment was performed in three ...environmental conditions (one with a set-point of 23 °C—a typical set-point used in Singapore—and two elevated (up to 28 °C) room temperature conditions). Occupants had shared control of ceiling fans.
The results show that the most comfortable thermal condition, with thermal sensation closest to neutral, is achieved at a room temperature of 26 °C with operating fans. Increasing the temperature set-point from 23 °C to 26 °C resulted in a significant increase in thermal acceptability (from 59% to 91%), and a 44 kWh/m2yr savings in electrical energy used for comfort cooling. We found that a room's set-point temperature can be increased up to 27 °C without creating a negative impact when controllable air movement is provided compared to an environment with a set-point of 23 °C. Thermal satisfaction is significantly higher in spaces of 26 °C with operating fans, than when the room's temperature is set at the typical 23 °C. Moreover, the relative humidity in the office is decreased from 62% (when the temperature was 23 °C) to 50% when the temperature was 27 °C.
Occupant's self-reported ability to concentrate, be alert, and ability to be productive was comparably high in all conditions. The results indicate that work performance is poorly correlated with room temperature, but increases with greater individual thermal satisfaction.
•The most comfortable conditions are achieved at a temperature of 26 °C with fans.•Ceiling fans provide neutral thermal sensation in real office environments with temperatures up to 27 °C.•Room relative humidity decreases with the increase of a room's temperature set-point.•Self-reported productivity is highest in conditions supporting neutral thermal sensation.•Self-reported productivity increases with an increase in occupants' thermal satisfaction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Elevated air movement produced by fans can offset air-conditioning energy requirements by allowing temperature setpoints to be raised without compromising thermal comfort. These advantages are even ...greater in hot and humid climates that inherently have large and sustained indoor cooling requirements. Few studies have assessed the in-situ benefits of fans in actual buildings. We installed ceiling and desk fans into a Zero Energy office building (675 m2) in Singapore. Across an 11-week period, 35 occupants alternated between two conditions (no fan vs. fan): 24 °C setpoint with fans off, and 26.5 °C setpoint with fans on. When the temperature setpoint was raised and elevated air movement was provided, a 32% energy reduction was obtained. The energy savings accrued without any negative impacts occurring on thermal satisfaction. Overcooling caused by thermal preference to slightly warmer and warmer conditions was substantially reduced from 33 to 9%. No changes in perceived air-staleness or self-reported alertness and ability to concentrate occurred either, indicating parity across the no fan and fan conditions. Although occupants primarily relied on ceiling fans at the 26.5 °C setpoint, they were by default on at the beginning of each day, giving less incentive to use the desk fans. Our study took place in a high-performance Zero Energy building, whereby thermal dissatisfaction was already low (7%). Therefore, notable changes did not occur, but significant improvements to thermal comfort could still occur in buildings that are unable to maintain high levels of thermal satisfaction.
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•We raised the setpoint from 24 to 26.5 °C and provided supplementary air movement.•Elevated air movement reduced cooling energy requirements by 32%.•No negative impacts to thermal preference or thermal satisfaction were found.•Overcooling was reduced from 33 to 9%.•Perceived air-staleness and self-reported productivity were unaffected.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Climate change and the urgency of decarbonizing the built environment are driving technological innovation in the way we deliver thermal comfort to occupants. These changes, in turn, seem to be ...setting the directions for contemporary thermal comfort research. This article presents a literature review of major changes, developments, and trends in the field of thermal comfort research over the last 20 years. One of the main paradigm shift was the fundamental conceptual reorientation that has taken place in thermal comfort thinking over the last 20 years; a shift away from the physically based determinism of Fanger's comfort model toward the mainstream and acceptance of the adaptive comfort model. Another noticeable shift has been from the undesirable toward the desirable qualities of air movement. Additionally, sophisticated models covering the physics and physiology of the human body were developed, driven by the continuous challenge to model thermal comfort at the same anatomical resolution and to combine these localized signals into a coherent, global thermal perception. Finally, the demand for ever increasing building energy efficiency is pushing technological innovation in the way we deliver comfortable indoor environments. These trends, in turn, continue setting the directions for contemporary thermal comfort research for the next decades.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Occupancy schedules and density can have a substantial influence on building plug, lighting, and air conditioning energy usage. In recent years, the study related to occupancy and its impact on ...building energy consumption has gained momentum and is also promoted by ASHRAE as it has created a multi-disciplinary group to encourage a comprehensive study of occupant behaviour in buildings. Past studies suggest that building systems do not consume the same energy and provide similar Indoor Environmental Quality (IEQ) to their designed specifications due to inaccurate assumptions of occupants and their behaviour. Supplying ASHRAE 62.1 specified minimum required ventilation based on accurate occupancy may lead to significant air-conditioning energy savings. However, the same strategy is not suitable in the current time since minimum required ventilation may not be sufficient to mitigate the SARS-CoV-2 virus spread in confined spaces. High-temperature cooling augmented with elevated air movement across an acceptable range of velocity can maintain the health and comfort of occupants by providing higher ventilation and without an energy penalty. The analysis of the literature highlights strengths, weaknesses, and key observations about the existing occupancy monitoring and occupancy-based building system control methods to help in the direction of future occupancy-based research.
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•Maintaining ASHRAE 62.1 specified minimum required ventilation based on occupancy schedules may lead to air-conditioning energy savings.•ASHRAE 62.1 specified minimum required ventilation may not be sufficient to mitigate the SARS-CoV-2 virus spread in confined spaces.•Occupants' IEQ requirements vary in contrast to the assumption of nearly homogeneous IEQ conditions.•Personalised ventilation can be used to minimize the indoor spread of SARS-CoV-2.•High-temperature cooling augmented with elevated air movement can maintain higher ventilation without an energy penalty.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Amaç: Bu çalışmada iki farklı dönme dairesi çapına sahip tavan tipi vantilatörün hava hareketlerinin Hesaplamalı Akışkanlar Dinamiği (HAD) yöntemiyle ortaya konulması ve en uygun türbülans modelinin ...belirlenmesi amaçlanmıştır.
Materyal ve Yöntem: İlk aşamada, tavan tipi vantilatörlerin fan merkezinden belirli uzaklıklardaki eksenel yöndeki hava hızı değişimleri ölçülmüştür. Bu amaçla zeminden iki farklı yükseklik (1.0 ve 1.5 m) dikkate alınmıştır. İkinci aşamada farklı türbülans modelleri ile hesaplamalı akışkanlar dinamiği analiz yöntemiyle hesaplanan değerler, ölçüm değerleri ile karşılaştırılmıştır.
Araştırma Bulguları: Sonuçlar istatistiksel olarak değerlendirildiğinde, en düşük MAE ve NRMSD değerleri 4 m dönme dairesi çapı için Spalart Allmaras ve SST k- modellerinde, 5 m dönme dairesi çapı için SST k- modelinde bulunmuştur. Grafik karşılaştırmalar incelendiğinde SST k- modelinin diğer modellere göre az da olsa daha iyi tahminlemeyi gerçekleştirdiği görülmektedir.
Sonuç: HAD simülasyon modellerinin çözüm yaklaşımları birbirine oldukça yakın bulunmuştur. Türbülans modelinin uygun seçimi ve iyi yapılandırılmış ağ yapısı ile zeminden belirli yükseklikteki noktalarda HAD simülasyonu ile deneysel verilere çok yakın tahminlerin elde edilebileceği ortaya konulmuştur.
Objective: The objective of this study was to determine the air movements of the ceiling fan with two different rotation circle diameter by using Computational Fluid Dynamics (CFD) method and select the most suitable turbulence model.
Material and Methods: In the first stage, the air velocity changes in the axial direction of ceiling fans at certain distances from the fan center were measured. For this purpose, two different heights (1.0 and 1.5 m) from the ground were taken into account. In the second step, the values calculated by the computational fluid dynamics analysis method using different turbulence models were compared with the measurements.
Results: The results were evaluated statistically. The lowest MAE and NRMSD values were found by using the Spalart Allmaras and SST k- models for fan with a 4 m rotation circle diameter, and the SST k- model for fan with a 5 m rotation circle diameter. Based on the graphical comparisons, it can be stated that the SST k- model made slightly better estimations than the other models.
Conclusion: The solution approaches of the CFD simulation models were found to be close to each other. The appropriate selection of the turbulence model and considering the well-designed mesh structure, it has been shown that estimates that are very close to experimental data can be obtained by CFD simulation at certain heights above the ground.
The effects of air movement from ceiling fans on subjective thermal comfort and perceived air quality (PAQ) were examined for warm-humid environments. In a climate chamber controlled at three ...temperatures (26 °C, 28 °C and 30 °C) and two relative humidity (RH 60% and 80%), sixteen subjects (8 males and 8 females) dressed in summer clothing (0.5 clo) were exposed to 7 levels of air speed ranging from 0.05 m/s to 1.8 m/s. The subjects were asked to rate their thermal sensation, comfort, PAQ, air movement acceptability, humidity sensation, eye-dryness during the 2-h and 15 min long tests. Air movement significantly improves the subjects' thermal comfort, PAQ, and humidity sensation without causing dry-eye discomfort. Without air movement, the 80% acceptable limit established by the ASHRAE standard 55 was reached at 26°C/60%RH, 26°C/80%RH, and 28°C/60%RH. With air movement, more than 80% of the subjects perceived the environments acceptable at 28°C/80%RH, 30°C/60%RH, and 30°C/80%RH. The preferred air speeds for ceiling fans were in many cases higher than the limit specified in ASHRAE Standard, which is 0.8 m/s when users have no control over the fan.
•We studied air movement and thermal comfort in warm-humid environments.•We obtained the acceptable range of temperature, humidity and air speeds.•Air movement improves thermal comfort and PAQ in warm-humid environments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Mixed-mode ventilation offers a promising solution for achieving comfortable indoor environments in an energy-efficient manner. However, in the tropics, characterized by a year-round hot and humid ...climate, opportunities for natural ventilation (NV) are typically limited to specific hours, necessitating operational mode switches on an intraday basis. Much of the thermal comfort research on mixed-mode ventilation relies either on cross-sectional data collected from different subjects or longitudinal data spanning a few seasons. This raises an open question: Can occupants thermally adapt when switching between NV and air-conditioning (AC) modes within a single day? To address the gap, our experimental study engaged 57 tropically acclimatized subjects, exposing them to combinations of five operational modes and four ceiling fan speeds (0.15-1.15 m/s) over an eight-hour timeframe. The results revealed that the subjects preferred a Standard Effective Temperature (SET*) that was 2-3 °C higher when operating in the NV mode compared to the AC modes, indicating thermal adaptation within the same day and in the same space. Specifically, the adaptation process was observed to stabilize between 35 to 45 mins following a mode switch. These findings contribute to the optimization of thermal comfort in mixed-mode controls, considering the dynamic characteristics of thermal adaptation.
•Thermal comfort experiment in tropical mixed-mode ventilation with ceiling fans.•Same-day and same-space thermal adaptation was observed when switching modes.•Thermal perceptions took 35 to 45 mins to adapt and stabilize after a mode switch.•NV in the tropics achieved 90% acceptability at a ceiling fan speed of 1.15 m/s.•Significant divergence between thermal preference and acceptability was identified.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The cooling effect of air movement is widely recognized as an energy-efficient measure for thermal environment management under the cooling mode, but it is generally neglected under the heating mode. ...This study proposes that the cooling effect of air movement negatively impacts the energy efficiency of advanced air distribution and should be considered when modulating advanced air distribution under the heating mode. Advanced air distribution like stratum ventilation and wall attachment ventilation supplies warm and clean air into the occupied zone by employing supply air momentum to suppress thermal buoyancy. However, the supply air momentum elevates the air movement in the occupied zone and the cooling effect of air movement negatively impacts the energy efficiency of advanced air distribution under the heating mode. Based on numerical simulations validated by the experiments, the results show the cooling effect of air movement significantly impacts the optimal operation, particularly the optimal supply airflow rate of stratum ventilation and the optimal supply air temperature of wall attachment ventilation. Accounting for the cooling effect of air movement can improve the optimal overall performance of advanced air distribution, particularly when the preference for energy efficiency increases. Compared with the optimization ignoring the cooling effect of air movement, the optimization considering the cooling effect of air movement improves the overall performance by up to 38.7% for stratum ventilation and up to 67.6% for wall attachment ventilation. Therefore, the cooling effect of air movement should be considered for modulating advanced air distribution under the heating mode.
•CE (Cooling effect) of air movement negatively impacts energy efficiency under heating mode.•CE of air movement significantly impacts optimal supply airflow rate of stratum ventilation.•CE of air movement significantly impacts optimal supply air temperature of wall attachment ventilation.•Optimization considering CE of air movement improves overall performance by up to 38.7% for stratum ventilation.•Optimization considering CE of air movement improves overall performance by up to 67.6% for wall attachment ventilation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
With the improvement of people’s living standard, the requirements of indoor air environment are also increased correspondingly. Trombe wall can not only improve the natural ventilation of buildings ...but also play an important role in cooling and heat storage of indoor temperature. The study of air flow velocity in Trombe Wall is critical for the improvement of Trombe wall performance. In this study, the regular patterns of air velocity is derived and analyzed by combining mathematics and simulation. And the changing rules of air velocity under different conditions are obtained. These research results can provide reliable basis and good reference for Trombe wall design and natural ventilation analysis.
•Trombe wall should be the same width as the boundary line.•The air velocity can be controlled by changing of the wall height.•The air velocity also increases with the increase of temperature difference.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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