Analysis on the impact of mean radiant temperature for the thermal comfort of underfloor air distribution systems

Relative humidity is an important micro-climate parameter in radiant cooling environment. Based on the human thermal comfort model, this paper studied the effect on PMV index of relative humidity, and studied the relationship of low mean radiant temperature and relative humidity, drew the appropriate design range of indoor relative humidity for radiant cooling systems.The results show that high relative humidity can compensate for the impact on thermal comfort of low mean radiant temperature, on the premise of achieving the same thermal comfort requirements. However, because of the limited compensation range of relative humidity, together with the constraints for it due to anti-condensation of radiant terminal devices, the design range of relative humidity should not be improved, and it can still use the traditional air-conditioning design standards.

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Thermomodernization of the school and change of the level of thermal comfort

Energy and automation ◽

10.31548/energiya2021.03.062 ◽

2021 ◽

pp. 62-74

Author(s):

V. Deshko ◽

◽

N. Buyak ◽

I. Bilous ◽

◽

...

Keyword(s):

Energy Consumption ◽

Thermal Comfort ◽

Comfort Level ◽

Mean Radiant Temperature ◽

Before And After ◽

Change In The Mean ◽

The Mean ◽

Energy Audits ◽

Radiant Temperature ◽

The Impact

The paper highlights the topical issue of ensuring the appropriate thermal comfort level and reducing energy consumption by public buildings. Thermal modernization, in turn, allows increasing the level of thermal comfort, which is not taken into account and evaluated in practice, although the relevant standards for comfort conditions and categories of buildings to ensure comfort have been introduced in Ukraine. The aim of the study is to analyze the impact of thermal modernization on the level of energy consumption and thermal comfort. The paper analyzes the change in the level of comfort before and after thermal modernization, defines the comfortable conditions category of the building, presents the change in the mean radiant temperature, as one of the main factors of PMV change in these conditions. PMV has been found to vary from -0.7 in the cold months to 0.2 in the off-season. Changing the thermal resistance can increase the PMV. The wall of the S orientation is characterized by larger fluctuations of PMV, which is due to the inflow of solar radiation and as a consequence of increasing the mean room radiant temperature. The change in the value of energy consumption is analyzed, the class of energy efficiency and the category for providing comfortable conditions are determined. Such an approach on the example of a real building is an example for conducting energy audits and certification taking into account comfort indicators.

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Thermal Comfort Evaluation of a Mixed-mode Ventilated Office Building with Advanced Natural Ventilation and Underfloor air Distribution Systems

Energy Procedia ◽

10.1016/j.egypro.2017.03.214 ◽

2017 ◽

Vol 111 ◽

pp. 520-529 ◽

Cited By ~ 8

Author(s):

Xiang Deng ◽

Georgios Kokogiannakis ◽

Zhenjun Ma ◽

Paul Cooper

Keyword(s):

Thermal Comfort ◽

Mixed Mode ◽

Distribution Systems ◽

Natural Ventilation ◽

Office Building ◽

Air Distribution ◽

Comfort Evaluation ◽

Underfloor Air Distribution

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Thermal Comfort Analysis for Overhead and Underfloor Air Distribution Systems

CFD Letters ◽

10.37934/cfdl.13.12.113132 ◽

2021 ◽

Vol 13 (12) ◽

pp. 113-132

Author(s):

Firas Basim Ismail ◽

Nizar F.O. Al-Muhsen ◽

Ain Amira Johari

Keyword(s):

Thermal Comfort ◽

Distribution Systems ◽

Cfd Simulation ◽

Fluid Dynamic ◽

Superior Performance ◽

Air Distribution ◽

Preventive Action ◽

Ansys Fluent ◽

Proposed Model ◽

Underfloor Air Distribution

Underfloor and overhead air distributions are two types of Heating Ventilating and Air Conditioning (HVAC) system in which both differs in term of channelling the supplied air into a space. Underfloor air distribution (UFAD) system channels the supplied air from the underfloor plenum and goes to the return vent at the ceiling. On the other hand, the overhead air distribution (OHAD) system utilizes the ceiling-to-ceiling air pathway approach. In this study, A developed HVAC model was proposed. Ansys Fluent program was used to numerically investigate the best thermal comfort of the proposed model in terms of occupant satisfaction by referring to ASHRAE Standard. Two scenarios were designed and adopted in the computational investigation which is OHAD and UFAD. Three heat-generating parameters were involved which are a room lamp, personal computer and occupant. The attained computational fluid dynamic (CFD) simulation results were validated. Generally, the attained CFD results showed that the UFAD system could perform better compare to the OHAD system even though the OHAD system could have some benefits. Specifically, the UFAD system provided the best thermal performance whereas the OHAD system was found to be less efficient in providing thermal comfort to the occupant and consumed a greater amount of energy because it was required to cool down the whole room instead of being cooled partly. The CFD results confirmed that the UFAD system was capable of maintaining the room temperature at 26°C at a height below 2.0 m compared to 1.2 m of the OHAD system. In conclusion, the UFAD system could provide better indoor air quality, and it could have superior performance for the tropic weather regions such as Malaysia compared to that of the OHAD system. Besides, using the UFAD system could be represented a preventive action that could be proposed to solve the mould growth inside any occupied room.

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Modeling Mean Radiant Temperature Distribution in Urban Landscapes Using DART

Remote Sensing ◽

10.3390/rs13081443 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1443

Author(s):

Maria Angela Dissegna ◽

Tiangang Yin ◽

Hao Wu ◽

Nicolas Lauret ◽

Shanshan Wei ◽

...

Keyword(s):

Remote Sensing ◽

Thermal Comfort ◽

Leaf Area ◽

Remote Sensing Data ◽

Outdoor Thermal Comfort ◽

Transfer Model ◽

Mean Radiant Temperature ◽

Area Index ◽

Sensing Data ◽

Radiant Temperature

The microclimatic conditions of the urban environment influence significantly the thermal comfort of human beings. One of the main human biometeorology parameters of thermal comfort is the Mean Radiant Temperature (Tmrt), which quantifies effective radiative flux reaching a human body. Simulation tools have proven useful to analyze the radiative behavior of an urban space and its impact on the inhabitants. We present a new method to produce detailed modeling of Tmrt spatial distribution using the 3-D Discrete Anisotropic Radiation Transfer model (DART). Our approach is capable to simulate Tmrt at different scales and under a range of parameters including the urban pattern, surface material of ground, walls, roofs, and properties of the vegetation (coverage, shape, spectral signature, Leaf Area Index and Leaf Area Density). The main advantages of our method are found in (1) the fine treatment of radiation in both short-wave and long-wave domains, (2) detailed specification of optical properties of urban surface materials and of vegetation, (3) precise representation of the vegetation component, and (4) capability to assimilate 3-D inputs derived from multisource remote sensing data. We illustrate and provide a first evaluation of the method in Singapore, a tropical city experiencing strong Urban Heat Island effect (UHI) and seeking to enhance the outdoor thermal comfort. The comparison between DART modelled and field estimated Tmrt shows good agreement in our study site under clear-sky condition over a time period from 10:00 to 19:00 (R2 = 0.9697, RMSE = 3.3249). The use of a 3-D radiative transfer model shows promising capability to study urban microclimate and outdoor thermal comfort with increasing landscape details, and to build linkage to remote sensing data. Our methodology has the potential to contribute towards optimizing climate-sensitive urban design when combined with the appropriate tools.

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How Can We Adapt Thermal Comfort for Disabled Patients? A Case Study of French Healthcare Buildings in Summer

Energies ◽

10.3390/en14154530 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4530

Author(s):

Youcef Bouzidi ◽

Zoubayre El Akili ◽

Antoine Gademer ◽

Nacef Tazi ◽

Adil Chahboun

Keyword(s):

Thermal Comfort ◽

Thermal Environment ◽

Residential Buildings ◽

Linear Regression Analysis ◽

Environmental Parameters ◽

Physical Parameters ◽

Mean Radiant Temperature ◽

Operative Temperature ◽

Neutral Temperature ◽

Radiant Temperature

This paper investigates adaptive thermal comfort during summer in medical residences that are located in the French city of Troyes and managed by the Association of Parents of Disabled Children (APEI). Thermal comfort in these buildings is evaluated using subjective measurements and objective physical parameters. The thermal sensations of respondents were determined by questionnaires, while thermal comfort was estimated using the predicted mean vote (PMV) model. Indoor environmental parameters (relative humidity, mean radiant temperature, air temperature, and air velocity) were measured using a thermal environment sensor during the summer period in July and August 2018. A good correlation was found between operative temperature, mean radiant temperature, and PMV. The neutral temperature was determined by linear regression analysis of the operative temperature and Fanger’s PMV model. The obtained neutral temperature is 23.7 °C. Based on the datasets and questionnaires, the adaptive coefficient α representing patients’ capacity to adapt to heat was found to be 1.261. A strong correlation was also observed between the sequential thermal index n(t) and the adaptive temperature. Finally, a new empirical model of adaptive temperature was developed using the data collected from a longitudinal survey in four residential buildings of APEI in summer, and the obtained adaptive temperature is 25.0 °C with upper and lower limits of 24.7 °C and 25.4 °C.

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Numerical Study on Coupled Operation of Stratified Air Distribution System and Natural Ventilation under Multi-Variable Factors in Large Space Buildings

Energies ◽

10.3390/en14238130 ◽

2021 ◽

Vol 14 (23) ◽

pp. 8130

Author(s):

Ziwen Dong ◽

Liting Zhang ◽

Yongwen Yang ◽

Qifen Li ◽

Hao Huang

Keyword(s):

Thermal Comfort ◽

Working Conditions ◽

Distribution System ◽

Distribution Systems ◽

Natural Ventilation ◽

Numerical Study ◽

Air Distribution ◽

Large Space ◽

Air Conditioners ◽

Air Supply

Stratified air distribution systems are commonly used in large space buildings. The research on the airflow organization of stratified air conditioners is deficient in terms of the analysis of multivariable factors. Moreover, studies on the coupled operation of stratified air conditioners and natural ventilation are few. In this paper, taking a Shanghai Airport Terminal departure hall for the study, air distribution and thermal comfort of the cross-section at a height of 1.6 m are simulated and compared under different working conditions, and the effect of natural ventilation coupling operation is studied. The results show that the air distribution is the most uniform and the thermal comfort is the best (predicted mean vote is 0.428, predicted percentage of dissatisfaction is 15.2%) when the working conditions are 5.9% air supply speed, 11 °C cooling temperature difference and 0° air supply angle. With the coupled operation of natural ventilation, the thermal comfort can be improved from Grade II to Grade I.

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A climatic study of an urban green space: the Gulbenkian Park in Lisbon (Portugal)

Finisterra ◽

10.18055/finis1420 ◽

2012 ◽

Vol 42 (84) ◽

Cited By ~ 2

Author(s):

Henrique Andrade ◽

Rute Vieira

Keyword(s):

Solar Radiation ◽

Thermal Comfort ◽

Green Space ◽

Urban Green Space ◽

Mean Radiant Temperature ◽

Climatic Parameters ◽

Incident Solar Radiation ◽

Urban Green ◽

Isolated Trees ◽

Radiant Temperature

Measurements of various climatic parameters were carried out in an average-sized green space in the centre of Lisbon (the Fundação Calouste Gulbenkian Park). The aims consisted of assessing the thermal differentiation between the park and the surrounding built-up area and analysing the microclimatic patterns within the park itself. The main results demonstrate that the park is cooler than the built-up area in all the seasons and both during the daytime and at night, but especially so in the daytime during the summer. The most signiﬁcant microclimatic contrasts were found to occur with respect to solar radiation and mean radiant temperature, with consequences upon the level of thermal comfort. The structure of the vegetation was also found to have a signiﬁcant microclimatic inﬂuence, since the reduction in the level of incident solar radiation brought on by the presence of groups of trees was much larger than that associated with isolated trees.

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

Energies ◽

10.3390/en12101835 ◽

2019 ◽

Vol 12 (10) ◽

pp. 1835 ◽

Cited By ~ 5

Author(s):

Arman Ameen ◽

Mathias Cehlin ◽

Ulf Larsson ◽

Taghi Karimipanah

Keyword(s):

Thermal Comfort ◽

Distribution Systems ◽

Cold Climate ◽

Air Distribution ◽

Temperature Pattern ◽

Office Environment ◽

Ventilation Effectiveness ◽

Local Thermal Comfort ◽

Heating Mode ◽

Occupied Zone

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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