An Assessment of Thermal Comfort for Thermoelectric-Based Radiant Cooling Systems: A Numerical Investigation

Spherical Object ◽

Cooling Systems ◽

Modeling And Analysis ◽

Radiant Cooling ◽

Abstract Studying various innovative cooling/heating technologies as alternatives to vapor-compression refrigeration cycles has received growing attention over the last few years. Thermoelectric (TE) systems are among the promising emerging technologies in this category. In the present paper, numerical modeling and analysis is performed using COMSOL Multiphysics to assess the performance of a thermoelectric (TE)-based radiant cooling ceiling panel on the thermal comfort in a test chamber. The system consists of a rectangular test chamber (∼ 1.2 m × 1.2 m × 1.5 m) with a ceiling panel fabricated on the center of the ceiling (0.6 m × 0.6 m × 0.002 m). Four TE modules are installed on the backside of the ceiling panel producing a cooling effect to maintain the ceiling temperature at the desired level. The lowered temperature of the ceiling panel allows heat exchange through radiation and convection. A spherical object is used to model a globe thermometer (GT) and capture the mean radiant temperature inside of the chamber. The variation of mean radiant temperature and operative temperature versus time are assessed under natural convection, and the comfort level is evaluated using the PMV method based on ASHRAE Standard 55. Design challenges, such as temperature limitation to the dew point temperature, among others, will be discussed. The result of this study provides insights regarding the expected thermal comfort from TE-based radiant cooling systems under various conditions.

Membrane-assisted radiant cooling for expanding thermal comfort zones globally without air conditioning

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2001678117 ◽

2020 ◽

Vol 117 (35) ◽

pp. 21162-21169 ◽

Cited By ~ 1

Author(s):

Eric Teitelbaum ◽

Kian Wee Chen ◽

Dorit Aviv ◽

Kipp Bradford ◽

Lea Ruefenacht ◽

...

Keyword(s):

Water Supply ◽

Thermal Comfort ◽

Cooling System ◽

Thermal Sensation ◽

Dew Point ◽

Radiation Exchange ◽

Radiant Cooling ◽

Chilled Water ◽

We present results of a radiant cooling system that made the hot and humid tropical climate of Singapore feel cool and comfortable. Thermal radiation exchange between occupants and surfaces in the built environment can augment thermal comfort. The lack of widespread commercial adoption of radiant-cooling technologies is due to two widely held views: 1) The low temperature required for radiant cooling in humid environments will form condensation; and 2) cold surfaces will still cool adjacent air via convection, limiting overall radiant-cooling effectiveness. This work directly challenges these views and provides proof-of-concept solutions examined for a transient thermal-comfort scenario. We constructed a demonstrative outdoor radiant-cooling pavilion in Singapore that used an infrared-transparent, low-density polyethylene membrane to provide radiant cooling at temperatures below the dew point. Test subjects who experienced the pavilion (n= 37) reported a “satisfactory” thermal sensation 79% of the time, despite experiencing 29.6 ± 0.9 °C air at 66.5 ± 5% relative humidity and with low air movement of 0.26 ± 0.18 m⋅s−1. Comfort was achieved with a coincident mean radiant temperature of 23.9 ± 0.8 °C, requiring a chilled water-supply temperature of 17.0 ± 1.8 °C. The pavilion operated successfully without any observed condensation on exposed surfaces, despite an observed dew-point temperature of 23.7 ± 0.7 °C. The coldest conditions observed without condensation used a chilled water-supply temperature 12.7 °C below the dew point, which resulted in a mean radiant temperature 3.6 °C below the dew point.

Design Range of Indoor Relative Humidity in Radiant Cooling Environment

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.4905 ◽

2011 ◽

Vol 243-249 ◽

pp. 4905-4908

Author(s):

Xue Min Sui ◽

Xu Zhang ◽

Guang Hui Han

Keyword(s):

Relative Humidity ◽

Thermal Comfort ◽

Design Standards ◽

Human Thermal Comfort ◽

Radiant Cooling ◽

Climate Parameter ◽

Radiant Temperature ◽

Thermal Comfort Model ◽

The Impact

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.

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 ◽

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.

Numerical analysis of cooling potential and indoor thermal comfort with a novel hybrid radiant cooling system in hot and humid climates

Indoor and Built Environment ◽

10.1177/1420326x211040853 ◽

2021 ◽

pp. 1420326X2110408

Author(s):

Jiying Liu ◽

Moon Keun Kim ◽

Jelena Srebric

Keyword(s):

Thermal Comfort ◽

Cooling System ◽

Comfort Level ◽

Thermal Output ◽

Radiant Cooling ◽

Room Condition ◽

Hot And Humid Climates ◽

The Mean ◽

Radiant Temperature ◽

Vapour Condensation

The study investigates a hybrid radiant cooling system's potential to achieve thermal comfort. The hybrid radiant cooling (HRC) system combines the best features of a typical all-air and conventional chilled radiant cooling system. An HRC system presents the advantages to (a) reduce vapour condensation and to (b) adjust the cooling output by using an Airbox convector. The three systems perceive thermal comfort in the predicted mean vote (PMV) between –0.5 and +0.5 at 25 and 27°C. In the room condition at 31°C, the all-air system has a lower thermal comfort level because the elevated airspeed is less effective when the mean radiant temperature (MRT) is low. This study suggests a cooling strategy to maximize the thermal comfort level by effectively utilizing the HRC in extreme conditions without extra cooling sources. When the designed set point indoor temperature is 25°C, the Airbox convector of the HRC fan can be off. However, if the indoor air temperature increases above 25°C, an occupant can activate the Airbox convector; the actual thermal output of HRC is increased, and the elevated airspeed can reduce the predicted percentage dissatisfied (PPD) level. Even in an extreme indoor thermal condition at 31°C, the HRC minimizes the PPD level.

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 ◽

Area Index ◽

Sensing Data ◽

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.

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 ◽

Operative Temperature ◽

Neutral 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.

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 ◽

Climatic Parameters ◽

Incident Solar Radiation ◽

Urban Green ◽

Isolated Trees ◽

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.

Numerical Investigations of Air Flow Patterns and Thermal Comfort in an Ice-Cream Factory Conditioned by Conventional Air Conditioning or Radiant Cooling Systems

10th International Energy Conversion Engineering Conference ◽

10.2514/6.2012-4099 ◽

2012 ◽

Author(s):

Essam Khalil ◽

Waled Sweida

Keyword(s):

Thermal Comfort ◽

Air Conditioning ◽

Air Flow ◽

Ice Cream ◽

Flow Patterns ◽

Cooling Systems ◽

Numerical Investigations ◽

Radiant Cooling

The most problematic variable in the course of human-biometeorological comfort assessment — the mean radiant temperature

Open Geosciences ◽

10.2478/s13533-011-0010-x ◽

2011 ◽

Vol 3 (1) ◽

Cited By ~ 40

Author(s):

Noémi Kántor ◽

János Unger

Keyword(s):

Thermal Comfort ◽

Short Wave ◽

Urban Environments ◽

Outdoor Thermal Comfort ◽

Radiation Environment ◽

Wave Radiation ◽

Radiation Fluxes ◽

The Mean ◽

AbstractThis paper gives a review on the topic of the mean radiant temperature Tmrt, the most important parameter influencing outdoor thermal comfort during sunny conditions. Tmrt summarizes all short wave and long wave radiation fluxes reaching the human body, which can be very complex (variable in spatial and also in temporal manner) in urban settings. Thermal comfort researchers and urban planners need easy and sound methodological approaches to assess Tmrt. After the basics of the Tmrt calculation some of the methods suitable for obtaining Tmrt also in urban environments will be presented.. Two of the discussed methods are based on instruments which measure the radiation fluxes integral (globe thermometer, pyranometer-pyrgeometer combination), and three of the methods are based on modelling the radiation environment with PC software (RayMan, ENVI-met and SOLWEIG).

The Derivation of Cooling Set-Point Temperature in an HVAC System, Considering Mean Radiant Temperature

Sustainability ◽

10.3390/su11195417 ◽

2019 ◽

Vol 11 (19) ◽

pp. 5417

Author(s):

Jinmog Han ◽

Jongkyun Bae ◽

Jihoon Jang ◽

Jumi Baek ◽

Seung-Bok Leigh

Keyword(s):

Thermal Comfort ◽

Indoor Environment ◽

Thermal Characteristics ◽

Weather Conditions ◽

System Control ◽

Hvac System ◽

Point Temperature ◽

Set Point ◽

Heating, ventilation, and air-conditioning (HVAC) systems usually have a set-point temperature control feature that uses the indoor dry-bulb temperature to control the indoor environment. However, an incorrect set-point temperature can reduce thermal comfort and result in unnecessary energy consumption. This study focuses on a derivation method for the optimal cooling set-point temperature of an HVAC system used in office buildings, considering the thermal characteristics and daily changes in the weather conditions, to establish a comfortable indoor environment and minimize unnecessary energy consumption. The operative temperature is used in the HVAC system control, and the mean radiant temperature is predicted with 94% accuracy through a multiple regression analysis by applying the indoor thermal environment data and weather information. The regression equation was utilized to create an additional equation to calculate the optimal set-point temperature. The simulation results indicate that the HVAC system control with the new set-point temperatures calculated from the derived equation improves thermal comfort by 38.5% (26%p). This study confirmed that a cooling set-point temperature that considers both the thermal characteristics of a building and weather conditions is effective in enhancing the indoor thermal comfort during summer.