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

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.

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

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.

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

2020 ◽  
Vol 117 (35) ◽  
pp. 21162-21169 ◽  
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 ◽  
Mean Radiant Temperature ◽  
Radiation Exchange ◽  
Radiant Cooling ◽  
Chilled Water ◽  
Radiant Temperature

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.

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

2021 ◽  
Author(s):  
Mohadeseh Seyednezhad ◽  
Hamidreza Najafi
Keyword(s):  
Thermal Comfort ◽  
Test Chamber ◽  
Comfort Level ◽  
Dew Point ◽  
Mean Radiant Temperature ◽  
Spherical Object ◽  
Cooling Systems ◽  
Modeling And Analysis ◽  
Radiant Cooling ◽  
Radiant Temperature

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.

Design Range of Indoor Relative Humidity in Radiant Cooling Environment

2011 ◽  
Vol 243-249 ◽  
pp. 4905-4908
Author(s):  
Xue Min Sui ◽  
Xu Zhang ◽  
Guang Hui Han
Keyword(s):  
Relative Humidity ◽  
Thermal Comfort ◽  
Mean Radiant Temperature ◽  
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.

scholarly journals Thermal Comfort and Energy Analysis of a Hybrid Cooling System by Coupling Natural Ventilation with Radiant and Indirect Evaporative Cooling

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7825
Author(s):  
Pradeep Shakya ◽  
Gimson Ng ◽  
Xiaoli Zhou ◽  
Yew Wah Wong ◽  
Swapnil Dubey ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
Hybrid System ◽  
Natural Ventilation ◽  
Cooling System ◽  
Evaporative Cooling ◽  
Supply System ◽  
Hybrid Cooling ◽  
Air Supply ◽  
Radiant Cooling ◽  
Indirect Evaporative Cooling

A hybrid cooling system which combines natural ventilation with a radiant cooling system for a hot and humid climate was studied. Indirect evaporative cooling was used to produce chilled water at temperatures slightly higher than the dew point. With this hybrid system, the condensation issue on the panel surface of a chilled ceiling was overcome. A computational fluid dynamics (CFD) model was employed to determine the cooling load and the parameters required for thermal comfort analysis for this hybrid system in an office-sized, well-insulated test room. Upon closer investigation, it was found that the thermal comfort by the hybrid system was acceptable only in limited outdoor conditions. Therefore, the hybrid system with a secondary fresh air supply system was suggested. Furthermore, the energy consumptions of conventional all-air, radiant cooling, and hybrid systems including the secondary air supply system were compared under similar thermal comfort conditions. The predicted results indicated that the hybrid system saves up to 77% and 61% of primary energy when compared with all-air and radiant cooling systems, respectively, while maintaining similar thermal comfort.

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

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Noémi Kántor ◽  
János Unger
Keyword(s):  
Thermal Comfort ◽  
Short Wave ◽  
Urban Environments ◽  
Outdoor Thermal Comfort ◽  
Radiation Environment ◽  
Wave Radiation ◽  
Mean Radiant Temperature ◽  
Radiation Fluxes ◽  
The Mean ◽  
Radiant Temperature

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).

scholarly journals Thermal comfort of patients in hospital ward areas

1977 ◽  
Vol 78 (1) ◽  
pp. 17-26 ◽  
Author(s):  
R. M. Smith ◽  
A. Rae
Keyword(s):  
Steady State ◽  
Thermal Comfort ◽  
Air Temperature ◽  
Hospital Ward ◽  
Patient Comfort ◽  
Mean Radiant Temperature ◽  
Air Velocity ◽  
Assessment Techniques ◽  
The Mean ◽  
Radiant Temperature

SUMMARYThe patient is identified as being of prime importance for comfort standards in hospital ward areas, other ward users being expected to adjust their dress to suit the conditions necessary for patient comfort. A study to identify the optimum steady state conditions for patient comfort is then described.Although this study raises some doubts as to the applicability of the standard thermal comfort assessment techniques to ward areas, it is felt that its results give a good indication of the steady-state conditions preferred by the patients. These were an air temperature of between 21.5° and 22° C and a relative humidity of between 30% and 70%, where the air velocity was less than 0.1 m/s and the mean radiant temperature was close to air temperature.

scholarly journals Control, Regulation and Command System of Hydronic Radiant Floors Heating by Wireless and Energy Harvesting Sensors and Actuators

2013 ◽  
Vol 543 ◽  
pp. 389-392 ◽  
Author(s):  
Gilberto Batista ◽  
Pedro Dinis Gaspar ◽  
Pedro D. Silva
Keyword(s):  
Energy Harvesting ◽  
Thermal Comfort ◽  
Air Temperature ◽  
Heating System ◽  
Comfort Level ◽  
Sensors And Actuators ◽  
Control Regulation ◽  
Radiant Temperature ◽  
And Control ◽  
Actual Control

This paper presents the development of an innovative control, regulation and command system for hydronic radiant floors, more flexible and efficient that guarantees a better thermal comfort to the user and simultaneously improves the energy efficiency of this type of heating system. The majority of the actual control of hydronic radiant floors is done by thermostats that measure the air temperature and control the actuators (pumps and valves) in order to maintain the room at the specified temperature. These systems requires the frequent adjustment of thermostats set-point in order to obtain thermal comfort as it depends on other factors than just the air temperature, such as, the air humidity, external environmental conditions, radiant temperature, among others. This paper presents a control, regulation and command solution that requires minimum user intervention, as the user only has to choose the desirable thermal comfort level. The control algorithm is based on the calculation of PMV (Predicted Mean Vote) index as defined on Thermal Comfort Standard ISO 7730. Another advantage of the proposed system is related to the wireless and energy harvesting sensors and actuators that provide much more flexibility to the system.

Sign in / Sign up

Export Citation Format

Share Document