Impact of evaporative cooling due to wetting of urban materials on local thermal comfort in a street canyon

This study provides comprehensive details of evaporative cooling options for building air-conditioning (AC) in Multan (Pakistan). Standalone evaporative cooling and standalone vapor compression AC (VCAC) systems are commonly used in Pakistan. Therefore, seven AC system configurations comprising of direct evaporative cooling (DEC), indirect evaporative cooling (IEC), VCAC, and their possible combinations, are explored for the climatic conditions of Multan. The study aims to explore the optimum AC system configuration for the building AC from the viewpoints of cooling capacity, system performance, energy consumption, and CO2 emissions. A simulation model was designed in DesignBuilder and simulated using EnergyPlus in order to optimize the applicability of the proposed systems. The standalone VCAC and hybrid IEC-VCAC & IEC-DEC-VCAC system configurations could achieve the desired human thermal comfort. The standalone DEC resulted in a maximum COP of 4.5, whereas, it was 2.1 in case of the hybrid IEC-DEC-VCAC system. The hybrid IEC-DEC-VCAC system achieved maximum temperature gradient (21 °C) and relatively less CO2 emissions as compared to standalone VCAC. In addition, it provided maximum cooling capacity (184 kW for work input of 100 kW), which is 85% higher than the standalone DEC system. Furthermore, it achieved neutral to slightly cool human thermal comfort i.e., 0 to −1 predicted mean vote and 30% of predicted percentage dissatisfied. Thus, the study concludes the hybrid IEC-DEC-VCAC as an optimum configuration for building AC in Multan.

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

Energies ◽

10.3390/en14227825 ◽

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.

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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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A parametric analysis of the influence of wind speed and direction on the thermal comfort performance of a Passive Downdraught Evaporative Cooling (PDEC) system – field measurements from a Saudi Arabian library

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/329/1/012042 ◽

2019 ◽

Vol 329 ◽

pp. 012042

Author(s):

M A Alshenaifi ◽

S Sharples

Keyword(s):

Wind Speed ◽

Thermal Comfort ◽

Parametric Analysis ◽

Evaporative Cooling ◽

Saudi Arabian ◽

Field Measurements

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Transient Human Thermal Comfort Response in Convective and Radiative Environments

Heat Transfer: Volume 3 ◽

10.1115/ht2008-56101 ◽

2008 ◽

Author(s):

Mohamad Al-Othmani ◽

Nesreen Ghaddar ◽

Kamel Ghali

Keyword(s):

Thermal Comfort ◽

Thermal Conditions ◽

Activity Level ◽

Convective Heating ◽

Convective System ◽

Clothing Insulation ◽

Indoor Space ◽

Human Thermal Comfort ◽

Walking Activity ◽

Local Thermal Comfort

In this work, human transient thermal responses and comfort are studied in non-uniform radiant heating and convective heating environments. The focus was on a change from walking activity of human in outdoor cold environment at high clothing insulation to warm indoor environment at sedentary activity level associated with lower clothing insulation. A transient multi-segmented bioheat model sensitive to radiant asymmetry is used to compare how fast the human body approaches steady state thermal conditions in both radiative and convective warm environments. A space thermal model is integrated with the bioheat model to predict the transient changes in skin and core temperature of a person subject to change in metabolic rate and clothing insulation when entering conditioned indoor space. It was found that overall thermal comfort and neutrality were reached in 6.2 minutes in the radiative environment compared to 9.24 minutes in convective environment. The local thermal comfort of various body segments differed in their response to the convective system where it took more than 19 minutes for extremities to reach local comfort unlike the radiative system where thermal comfort was attained within 7 minutes.

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Assessing the indoor thermal comfort of a toll station

MATEC Web of Conferences ◽

10.1051/matecconf/201928202031 ◽

2019 ◽

Vol 282 ◽

pp. 02031

Author(s):

Ricardo M.S.F. Almeida ◽

Eva Barreira ◽

Sandra Soares ◽

Ramos Nuno M.M. ◽

Sérgio Lopes ◽

...

Keyword(s):

Thermal Comfort ◽

Indoor Environment ◽

Thermal Sensation ◽

Physical Parameters ◽

Indoor Environmental Quality ◽

Thermal Perception ◽

Health And Wellbeing ◽

Local Thermal Comfort ◽

Toll Station ◽

Global And Local

The importance of a good indoor environment for peoples’ health and wellbeing is nowadays clearly established. Besides enhancing the wellbeing of building occupants and helping decrease the occurrence of building related illness, a good indoor environment can also lead to a decrease in worker complaints and absenteeism. This paper presents the results of a three-month monitoring campaign where the thermal comfort of a toll station was evaluated, including the main room and the cabins. The physical parameters required for the assessment of both global and local thermal comfort were measured and the results were compared with the thermal perception of the occupants, which was collected through questionnaires. The indoor environmental quality in the main room was better than in the cabins and a mismatch between the PMV index and the occupants thermal sensation was identified.

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Numerical analysis of local thermal comfort in a plan office under natural ventilation

Indoor and Built Environment ◽

10.1177/1420326x19866497 ◽

2019 ◽

Vol 29 (7) ◽

pp. 972-986 ◽

Cited By ~ 3

Author(s):

Xiang Deng ◽

Zijing Tan

Keyword(s):

Thermal Comfort ◽

Natural Ventilation ◽

Meteorological Data ◽

Ventilation System ◽

Comfort Level ◽

Open Plan ◽

Computational Fluid Dynamics Cfd ◽

Internal Volume ◽

Local Thermal Comfort ◽

Primary Focus

The utilisation of automatic controlled natural wind in office buildings to maintain indoor thermal comfort has gained wide attention in recent years. Generally, it is not necessary to ensure that the whole internal volume of a building with large open spaces meets thermal comfort requirements. Primary focus should be on occupied areas. Accordingly, the local thermal comfort in an open-plan office with automatic controlled natural ventilation system was investigated numerically and experimentally. A computational fluid dynamics (CFD)-based method was presented for indoor environment and thermal comfort prediction. Long-term in situ measurement was conducted during summer and transition seasons. The meteorological data were collected by a mini weather station located on the roof of the target building. Meanwhile, indoor air velocity, temperature, turbulence intensity and wall temperatures were recorded locally. Three thermal comfort indices, i.e. thermal stratification represented by percentage dissatisfied (PD), the extended predicted mean vote (PMVe) and draught rate were employed to evaluate the thermal comfort level of the interested areas during natural ventilation period. The numerical results revealed a risk of local thermal dissatisfaction under low outdoor temperature and strong windy conditions.

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User Thermal Comfort in Historic Buildings: Evaluation of the Potential of Thermal Mass, Orientation, Evaporative Cooling and Ventilation

Sustainability ◽

10.3390/su12229672 ◽

2020 ◽

Vol 12 (22) ◽

pp. 9672

Author(s):

Mamdooh Alwetaishi ◽

Ashraf Balabel ◽

Ahmed Abdelhafiz ◽

Usama Issa ◽

Ibrahim Sharaky ◽

...

Keyword(s):

Thermal Comfort ◽

High Altitude ◽

Air Temperature ◽

Thermal Performance ◽

Indoor Air ◽

Computer Modelling ◽

Evaporative Cooling ◽

Comfort Level ◽

Thermal Mass ◽

The Impact

The study investigated the level of thermal comfort in historical buildings located at a relatively high altitude in the Arabian Desert of Saudi Arabia. The study focused on the impact of the use of thermal mass and orientation on the level of thermal performance at Shubra and Boqri Palaces. Qualitative and quantitative analyses were used in this study, including a questionnaire interview with architecture experts living at the relatively high altitude of Taif city, to obtain data and information from local experts. The computer software TAS EDSL was used along with on-site equipment, such as thermal imaging cameras and data loggers, to observe the physical conditions of the building in terms of its thermal performance. The study revealed that the experts’ age and years of experience were important aspects while collecting data from them during the survey. The use of thermal mass had a slight impact on the indoor air temperature as well as the energy consumption, but it helped in providing thermal comfort. Use of ventilation can improve thermal comfort level. Evaporative cooling technique has a considerable impact on reducing indoor air temperature with 4 °C drop, improving the thermal comfort sensation level. The novelty of this work is that, it links the outcomes of qualitative results of experts with field monitoring as well as computer modelling. This can contribute as method to accurately collect data in similar case studies.

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