Energies

Research

30 pages, 8148 KiB

Open AccessArticle

A Numerical and Experimental Investigation of a Confluent Jets Ventilation Supply Device in a Conference Room

by Harald Andersson, Mathias Cehlin and Bahram Moshfegh

Energies 2022, 15(5), 1630; https://doi.org/10.3390/en15051630 - 22 Feb 2022

Cited by 5 | Viewed by 1859

In this study, confluent jets ventilation (CJV) supply devices with three different nozzle arrays (1 × 19, 2 × 19, 3 × 19) were investigated both numerically and experimentally at two different airflow and supply air temperature set-ups. The performance of the CJV [...] Read more.

In this study, confluent jets ventilation (CJV) supply devices with three different nozzle arrays (1 × 19, 2 × 19, 3 × 19) were investigated both numerically and experimentally at two different airflow and supply air temperature set-ups. The performance of the CJV supply devices was investigated concerning thermal comfort, indoor air quality (IAQ), and heat removal effectiveness in a conference room environment. A comparison between the experimental and numerical results showed that the

\bar{ϑ^{2}} - f

model had the best agreement out of the investigated turbulence models. The numerical results showed that the size of the array had a great impact both on near-field development and on the conditions in the occupied zone. A larger array with multiple rows and a lower momentum conserved the inlet temperature and the mean age of the air better than a single-row array with a higher momentum. A larger array with multiple rows had a higher IAQ and a greater heat removal effectiveness in the occupied zone because the larger array conserved the mean age of air better and the buoyancy driven flow was slightly better at removing the heat. Because of the lower inlet velocities, they also had lower velocities at ankle level, which decreased the risk of draft and thermal discomfort. Full article

(This article belongs to the Special Issue Sustainable Buildings: Heating, Ventilation and Air-Conditioning)

► Show Figures

Figure 1

23 pages, 8322 KiB

Open AccessArticle

Effects of Air Supply Terminal Devices on the Performance of Variable Refrigerant Flow Integrated Stratum Ventilation System: An Experimental Study

by Yat Huang Yau, Umair Ahmed Rajput, Altaf Hussain Rajpar and Natalia Lastovets

Energies 2022, 15(4), 1265; https://doi.org/10.3390/en15041265 - 9 Feb 2022

Cited by 4 | Viewed by 2410

Abstract

A variable refrigerant flow integrated stratum ventilation (VRF-SV) system was proposed as an energy efficient substitute for conventional central cooling systems for buildings. The novel system provided conditioned air to enclosed spaces with high indoor air quality and thermal comfort. This study investigated [...] Read more.

A variable refrigerant flow integrated stratum ventilation (VRF-SV) system was proposed as an energy efficient substitute for conventional central cooling systems for buildings. The novel system provided conditioned air to enclosed spaces with high indoor air quality and thermal comfort. This study investigated the effects of different types of ASTDs on the performance of the VRF-SV hybrid system. The performance was experimentally evaluated with five air terminal types, including bar grille, double deflection grille, jet slot, perforated and drum louver diffusers. The evaluation was carried out using standard indices: temperature and velocity distribution, airflow pattern, effective draft temperature (EDT), air distribution performance index (ADPI), thermal sensation vote and comfort feedback survey. The results indicated that the ASTD type had a significant impact on airflow pattern. Furthermore, the bar grille diffuser provided the occupants with greater thermal comfort and acceptable indoor environment. Almost all the EDT values determined in the breathing zone in the case with bar grille diffuser found under the satisfactory range, i.e., −1.2 < K < 1.2. Based on these values, the ADPI for bar grille diffuser was calculated as 92.8%. Thus, the bar grille diffuser is recommended to be installed with the VRF-SV hybrid system in buildings. Full article

(This article belongs to the Special Issue Sustainable Buildings: Heating, Ventilation and Air-Conditioning)

► Show Figures

Figure 1

28 pages, 7460 KiB

Open AccessArticle

Comparison of Single- and Multipipe Earth-to-Air Heat Exchangers in Terms of Energy Gains and Electricity Consumption: A Case Study for the Temperate Climate of Central Europe

by Łukasz Amanowicz and Janusz Wojtkowiak

Energies 2021, 14(24), 8217; https://doi.org/10.3390/en14248217 - 7 Dec 2021

Cited by 21 | Viewed by 4277

Abstract

Earth-to-air heat exchangers (EAHEs) can be used in the ventilation systems of various types of buildings. Multipipe structures can be found in large-volume buildings, yet scientific analysis of such systems is rare. Annual energy gains and electricity consumption for equivalent single-pipe and multipipe [...] Read more.

Earth-to-air heat exchangers (EAHEs) can be used in the ventilation systems of various types of buildings. Multipipe structures can be found in large-volume buildings, yet scientific analysis of such systems is rare. Annual energy gains and electricity consumption for equivalent single-pipe and multipipe systems are typically not available. This paper bridges this gap, presenting the results of experimental studies on pressure losses in three-, five- and seven-pipe EAHEs and analysis for the annual energy gains and electric energy consumption as compared to a single-pipe exchanger. The results showed that the multipipe EAHE can be successfully replaced by a single-pipe structure with the same thermal performance and similar pressure losses if a tube with the appropriate diameter is used. However, multipipe heat exchangers can also use pipes of larger diameter (manifolds and/or branches), which improves their energy efficiency and may then make them more advantageous than single-pipe structures. From this reason, ultimately, the final selection of exchanger geometry should take into account economic and environmental issues and also user preferences and their importance in the hierarchy. Full article

(This article belongs to the Special Issue Sustainable Buildings: Heating, Ventilation and Air-Conditioning)

► Show Figures

Figure 1

31 pages, 5482 KiB

Open AccessArticle

Thermodynamic Performance Investigation of a Small-Scale Solar Compression-Assisted Multi-Ejector Indoor Air Conditioning System for Hot Climate Conditions

by Valerie Eveloy and Yusra Alkendi

Energies 2021, 14(14), 4325; https://doi.org/10.3390/en14144325 - 18 Jul 2021

Cited by 8 | Viewed by 2473

Abstract

In year-round hot climatic conditions, conventional air conditioning systems consume significant amounts of electricity primarily generated by conventional power plants. A compression-assisted, multi-ejector space cooling system driven by low-grade solar thermal energy is investigated in terms of energy and exergy performance, using a [...] Read more.

In year-round hot climatic conditions, conventional air conditioning systems consume significant amounts of electricity primarily generated by conventional power plants. A compression-assisted, multi-ejector space cooling system driven by low-grade solar thermal energy is investigated in terms of energy and exergy performance, using a real gas property-based ejector model for a 36 kW-scale air conditioning application, exposed to annually high outdoor temperatures (i.e., up to 42 °C), for four working fluids (R11, R141b, R245fa, R600a). Using R245fa, the multi-ejector system effectively triples the operating condenser temperature range of a single ejector system to cover the range of annual outdoor conditions, while compression boosting reduces the generator heat input requirement and improves the overall refrigeration coefficient of performance (COP) by factors of ~3–8 at medium- to high-bound condenser temperatures, relative to simple ejector cycles. The system solar fraction varies from ~0.2 to 0.9 in summer and winter, respectively, with annual average mechanical and overall COPs of 24.5 and 0.21, respectively. Exergy destruction primarily takes place in the ejector assembly, but ejector exergy efficiency improves with compression boosting. The system could reduce annual electric cooling loads by over 40% compared with a conventional local split air conditioner, with corresponding savings in electricity expenditure and GHG emissions. Full article

(This article belongs to the Special Issue Sustainable Buildings: Heating, Ventilation and Air-Conditioning)

► Show Figures

Figure 1

23 pages, 5783 KiB

Open AccessArticle

Effect of Roof Cooling and Air Curtain Gates on Thermal and Wind Conditions in Stadiums for Hot Climates

by Fangliang Zhong, Hassam Nasarullah Chaudhry and John Kaiser Calautit

Energies 2021, 14(13), 3941; https://doi.org/10.3390/en14133941 - 1 Jul 2021

Cited by 7 | Viewed by 2700

Abstract

To host the 2022 FIFA World Cup, Qatar is facing the greatest challenge in balancing the energy consumptions for cooling the stadiums and the thermal comfort for both players and spectators. Previous studies have not considered using a combined configuration of air curtain [...] Read more.

To host the 2022 FIFA World Cup, Qatar is facing the greatest challenge in balancing the energy consumptions for cooling the stadiums and the thermal comfort for both players and spectators. Previous studies have not considered using a combined configuration of air curtain and roof cooling supply slot in stadiums to prevent the infiltration of outside hot air and reduce the cooling system’s energy consumption. This paper presents a Computational Fluid Dynamics (CFD) study of thermal and wind modeling around a baseline stadium and simulates the cooling scenarios of air curtains and roof cooling along with the energy consumption estimations for the World Cup matches using Building Energy Simulation (BES). Sensitivity analysis of different supply speeds and supply temperatures of air curtain gates and roof cooling was carried out, and the results showed that scenario six, which provides supply air of 25 m/s and 20 m/s at the roof and air curtain gates with a supply temperature of 10 °C, demonstrates optimal thermal performances on both the spectator tiers and the pitch. Compared with the baseline stadium performance, the average reductions in temperature on the pitch and spectator tiers under scenario six could reach 15 °C and 14.6 °C. The reductions in the Predicted Percentage of Dissatisfied values for the upper and lower tiers as well as the pitch were 63%, 74%, and 78%. In terms of the estimated energy consumptions, scenario six would consume electric energy per match at a rate of 25.5 MWh compared with 22.8 MWh for one of the stadiums in the 2010 South Africa World Cup and 42.0 MWh for the 2006 Germany World Cup. Future research is recommended to explore the influence of supply angle on air curtain gates and roof cooling supply slots’ performances. Full article

(This article belongs to the Special Issue Sustainable Buildings: Heating, Ventilation and Air-Conditioning)

► Show Figures

Figure 1

33 pages, 10526 KiB

Open AccessArticle

Evaluating the Use of Displacement Ventilation for Providing Space Heating in Unoccupied Periods Using Laboratory Experiments, Field Tests and Numerical Simulations

by Saqib Javed, Ivar Rognhaug Ørnes, Tor Helge Dokka, Maria Myrup and Sverre Bjørn Holøs

Energies 2021, 14(4), 952; https://doi.org/10.3390/en14040952 - 11 Feb 2021

Cited by 8 | Viewed by 5961

Abstract

Displacement ventilation is a proven method of providing conditioned air to enclosed spaces with the aim to deliver good air quality and thermal comfort while reducing the amount of energy required to operate the system. Until now, the practical applications of displacement ventilation [...] Read more.

Displacement ventilation is a proven method of providing conditioned air to enclosed spaces with the aim to deliver good air quality and thermal comfort while reducing the amount of energy required to operate the system. Until now, the practical applications of displacement ventilation have been exclusive to providing ventilation and cooling to large open spaces with high ceilings. The provision of heating through displacement ventilation has traditionally been discouraged, out of concern that warm air supplied at the floor level would rise straight to the ceiling level without providing heat to the occupied space. Hence, a separate heating system is regularly integrated with the displacement ventilation in cold climates, increasing the cost and energy use of the system. This paper goes beyond the common industry practice and explores the possibility of using displacement ventilation to provide heating without any additional heating system. It reports on experimental investigations conducted in laboratory and field settings, and numerical simulation of these studies, all aimed at investigating the application of displacement ventilation for providing a comfortable indoor environment in winter by preheating the space prior to occupancy. The experimental results confirm that the proposed concept of providing space heating in unoccupied periods without a separate heating system is possible with displacement ventilation. Full article

(This article belongs to the Special Issue Sustainable Buildings: Heating, Ventilation and Air-Conditioning)

► Show Figures

Figure 1

24 pages, 1890 KiB

Open AccessArticle

Building Energy Management for Passive Cooling Based on Stochastic Occupants Behavior Evaluation

by Michele Roccotelli, Alessandro Rinaldi, Maria Pia Fanti and Francesco Iannone

Energies 2021, 14(1), 138; https://doi.org/10.3390/en14010138 - 29 Dec 2020

Cited by 15 | Viewed by 2613

Abstract

The common approach to model occupants behaviors in buildings is deterministic and consists of assumptions based on predefined fixed schedules or rules. In contrast with the deterministic models, stochastic and agent based (AB) models are the most powerful and suitable methods for modeling [...] Read more.

The common approach to model occupants behaviors in buildings is deterministic and consists of assumptions based on predefined fixed schedules or rules. In contrast with the deterministic models, stochastic and agent based (AB) models are the most powerful and suitable methods for modeling complex systems as the human behavior. In this paper, a co-simulation architecture is proposed with the aim of modeling the occupant behavior in buildings by a stochastic-AB approach and implementing an intelligent Building Energy Management System (BEMS). In particular, optimized control logics are designed for smart passive cooling by controlling natural ventilation and solar shading systems to guarantee the thermal comfort conditions and maintain energy performance. Moreover, the effects of occupant actions on indoor thermal comfort are also taken into account. This study shows how the integration of automation systems and passive techniques increases the potentialities of passive cooling in buildings, integrating or replacing the conventional efficiency strategies. Full article

(This article belongs to the Special Issue Sustainable Buildings: Heating, Ventilation and Air-Conditioning)

► Show Figures

Figure 1

24 pages, 8894 KiB

Open AccessArticle

On the Ventilation Performance of Low Momentum Confluent Jets Supply Device in a Classroom

by Harald Andersson, Alan Kabanshi, Mathias Cehlin and Bahram Moshfegh

Energies 2020, 13(20), 5415; https://doi.org/10.3390/en13205415 - 16 Oct 2020

Cited by 8 | Viewed by 1957

Abstract

The performance of three different confluent jets ventilation (CJV) supply devices was evaluated in a classroom environment concerning thermal comfort, indoor air quality (IAQ) and energy efficiency. The CJV supply devices have the acronyms: high-momentum confluent jets (HMCJ), low-momentum confluent jets (LMCJ) and [...] Read more.

The performance of three different confluent jets ventilation (CJV) supply devices was evaluated in a classroom environment concerning thermal comfort, indoor air quality (IAQ) and energy efficiency. The CJV supply devices have the acronyms: high-momentum confluent jets (HMCJ), low-momentum confluent jets (LMCJ) and low-momentum confluent jets modified by varying airflow direction (LMCJ-M). A mixing ventilation (MV) slot jet (SJ) supply device was used as a benchmark. Comparisons were made with identical set-up conditions in five cases with different supply temperatures (T_S) (16–18 °C), airflow rates (2.2–6.3 ACH) and heat loads (17–47 W/m²). Performances were evaluated based on DR (draft rating), PMV (predicted mean vote), ACE (air change effectiveness) and heat removal effectiveness (HRE). The results show that CJV had higher HRE and IAQ than MV and LMCJ/LMCJ-M had higher ACE than HMCJ. The main effects of lower T_s were higher velocities, DR (HMCJ particularly) and HRE in the occupied zone as well as lower temperatures and PMV-values. HMCJ and LMCJ produce MV conditions at lower airflow rates (<4.2 ACH) and non-uniform conditions at higher airflow rates. LMCJ-M had 7% higher HRE than the other CJV supply devices and produced non-uniform conditions at lower airflow rates (<3.3 ACH). The non-uniform conditions resulted in LMCJ-M having the highest energy efficiency of all devices. Full article

(This article belongs to the Special Issue Sustainable Buildings: Heating, Ventilation and Air-Conditioning)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Sustainable Buildings: Heating, Ventilation and Air-Conditioning

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (8 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI