Research

25 pages, 7291 KiB

Open AccessArticle

Seasonal Analysis Comparison of Three Air-Cooling Systems in Terms of Thermal Comfort, Air Quality and Energy Consumption for School Buildings in Mediterranean Climates

by María Jesús Romero-Lara, Francisco Comino and Manuel Ruiz de Adana

Energies 2021, 14(15), 4436; https://doi.org/10.3390/en14154436 - 22 Jul 2021

Cited by 5 | Viewed by 2502

Abstract

Efficient air-cooling systems for hot climatic conditions, such as Southern Europe, are required in the context of nearly Zero Energy Buildings, nZEB. Innovative air-cooling systems such as regenerative indirect evaporative coolers, RIEC and desiccant regenerative indirect evaporative coolers, DRIEC, can be considered an [...] Read more.

Efficient air-cooling systems for hot climatic conditions, such as Southern Europe, are required in the context of nearly Zero Energy Buildings, nZEB. Innovative air-cooling systems such as regenerative indirect evaporative coolers, RIEC and desiccant regenerative indirect evaporative coolers, DRIEC, can be considered an interesting alternative to direct expansion air-cooling systems, DX. The main aim of the present work was to evaluate the seasonal performance of three air-cooling systems in terms of air quality, thermal comfort and energy consumption in a standard classroom. Several annual energy simulations were carried out to evaluate these indexes for four different climate zones in the Mediterranean area. The simulations were carried out with empirically validated models. The results showed that DRIEC and DX improved by 29.8% and 14.6% over RIEC regarding thermal comfort, for the warmest climatic conditions, Lampedusa and Seville. However, DX showed an energy consumption three and four times higher than DRIEC for these climatic conditions, respectively. RIEC provided the highest percentage of hours with favorable indoor air quality for all climate zones, between 46.3% and 67.5%. Therefore, the air-cooling systems DRIEC and RIEC have a significant potential to reduce energy consumption, achieving the user’s thermal comfort and improving indoor air quality. Full article

(This article belongs to the Special Issue Ventilation and Building Energy Systems)

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17 pages, 9769 KiB

Open AccessArticle

Analysis of the Velocity Distribution in the Plenum Box with Various Entries

by Joanna Halibart, Klaudia Zwolińska, Marek Borowski and Marek Jaszczur

Energies 2021, 14(12), 3630; https://doi.org/10.3390/en14123630 - 18 Jun 2021

Cited by 4 | Viewed by 2821

Abstract

The ventilation system plays a crucial role in every building. Proper design and optimization of its operation increase the comfort of users due to efficient air exchange and at the same time control its velocity in the rooms. The aim of this paper [...] Read more.

The ventilation system plays a crucial role in every building. Proper design and optimization of its operation increase the comfort of users due to efficient air exchange and at the same time control its velocity in the rooms. The aim of this paper is the analysis of the effect of plenum box entry on the velocity profile concerning the diffuser face panel. This issue may sometimes be ignored at the design stage but can significantly affect the airflow from the diffuser and consequently increase the risk of draft. The results of the PIV experimental measurements and numerical simulations concerning various entries of the plenum box (top and side) were investigated in this study. The measurements were used to develop the mathematical and numerical models, which were then used to assess the effect of localization of the spigot of the plenum box on its operation. The numerical analysis was carried out on plenum boxes with the air diffuser with a face panel composed of square grid perforations. Analyses show that the entries significantly affect both the way of air distribution inside the plenum box and the profile of the airflow and its velocity under the simulated air diffuser. Full article

(This article belongs to the Special Issue Ventilation and Building Energy Systems)

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19 pages, 7609 KiB

Open AccessArticle

Evaluation of Integral Effect of Thermal Comfort, Air Quality and Draught Risk for Desks Equipped with Personalized Ventilation Systems

by Eusébio Conceição and Hazim Awbi

Energies 2021, 14(11), 3235; https://doi.org/10.3390/en14113235 - 01 Jun 2021

Cited by 20 | Viewed by 1971

Abstract

This work evaluates the integral effect of thermal comfort (TC), indoor air quality (IAQ) and Draught Risk (DR) for desks with four personalized ventilation (PV) systems. The numerical study, for winter and summer thermal conditions, considers a virtual chamber, a desk, four different [...] Read more.

This work evaluates the integral effect of thermal comfort (TC), indoor air quality (IAQ) and Draught Risk (DR) for desks with four personalized ventilation (PV) systems. The numerical study, for winter and summer thermal conditions, considers a virtual chamber, a desk, four different PV systems, four seats and four virtual manikins. Two different PV configurations, two upper and two lower air terminal devices (ATD) with different distance between them are considered. In this study a coupling of numerical methodology, using one differential and two integral models, is used. The heating, ventilating and air conditioning (HVAC) system performance in this work is evaluated using DR and room air removal effectiveness (ε_DR) that is incorporated in an Air Distribution Index (ADI). This new index, named the Air Distribution Turbulence Index (ADTI), is used to consider simultaneously the TC, the IAQ, the DR and the effectiveness for heat removal (ε_TC), contaminant removal (ε_AQ) and room air removal (ε_DR). The results show that the ADI and ADTI, are generally higher for Case II than for Case I, increase when the inlet air velocity increases, are higher when the exit air is located at a height 1.2 m than when is located at 1.8 m, and are higher for summer conditions than for winter conditions. However, the values are higher for the ADI than ADTI. Full article

(This article belongs to the Special Issue Ventilation and Building Energy Systems)

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15 pages, 5103 KiB

Open AccessArticle

Indoor Climate Performance in a Renovated School Building

by Pavla Mocová and Jitka Mohelníková

Energies 2021, 14(10), 2827; https://doi.org/10.3390/en14102827 - 14 May 2021

Cited by 6 | Viewed by 1800

Abstract

Indoor climate comfort is important for school buildings. Nowadays, this is a topical problem, especially in renovated buildings. Poorly ventilated school classrooms create improper conditions for classrooms. A post-occupancy study was performed in a school building in temperate climatic conditions. The evaluation was [...] Read more.

Indoor climate comfort is important for school buildings. Nowadays, this is a topical problem, especially in renovated buildings. Poorly ventilated school classrooms create improper conditions for classrooms. A post-occupancy study was performed in a school building in temperate climatic conditions. The evaluation was based on the results of long-term monitoring of the natural ventilation strategy and measurements of the carbon dioxide concentration in the school classroom’s indoor environment. The monitoring was carried out in an old school building that was constructed in the 1970s and compared to testing carried out in the same school classroom after the building was renovated in 2016. Surprisingly, the renovated classroom had a significantly higher concentration of CO₂. It was found that this was due to the regulation of the heating system and the new airtight windows. The occupants of the renovated classroom have a maintained thermal comfort, but natural ventilation is rather neglected. A controlled ventilation strategy and installation of heat recovery units are recommended to solve these problems with the classroom’s indoor environment. Microbiological testing of the surfaces in school classrooms also shows the importance of fresh air and solar radiation access for indoor comfort. Full article

(This article belongs to the Special Issue Ventilation and Building Energy Systems)

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21 pages, 7236 KiB

Open AccessArticle

Optimization of Window-to-Wall Ratio for Buildings Located in Different Climates: An IDA-Indoor Climate and Energy Simulation Study

by Sana Sayadi, Abolfazl Hayati and Mazyar Salmanzadeh

Energies 2021, 14(7), 1974; https://doi.org/10.3390/en14071974 - 02 Apr 2021

Cited by 23 | Viewed by 5442

Abstract

This study investigates different cases to obtain optimal Window-to-Wall ratio (WWR) in seven different climate conditions based on the Köppen–Geiger climate classification. The optimal WWR was decided based on the minimum amount of total energy use (total of cooling, heating, and lighting energy [...] Read more.

This study investigates different cases to obtain optimal Window-to-Wall ratio (WWR) in seven different climate conditions based on the Köppen–Geiger climate classification. The optimal WWR was decided based on the minimum amount of total energy use (total of cooling, heating, and lighting energy use) of a building model during a complete year. The impact of overhang and automatic blinds were assessed on the optimization of WWR for a building with integrated automatic lighting control. Moreover, three different windows with different U-values and features were employed in order to analyze their effect on the energy use and WWR of the building. IDA-Indoor Climate and Energy (IDA-ICE) was used to carry out the simulations. The software has been validated based on ASHRAE Standard 140. Based on each climate condition, orientation, employed window type, and comfort conditions, an optimal range with a specific combination of window with blind, overhang, or neither was found. Full article

(This article belongs to the Special Issue Ventilation and Building Energy Systems)

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18 pages, 3709 KiB

Open AccessArticle

Study of Radial Wall Jets from Ceiling Diffusers at Variable Air Volume

by Maria Hurnik, Jan Kaczmarczyk and Zbigniew Popiolek

Energies 2021, 14(1), 240; https://doi.org/10.3390/en14010240 - 05 Jan 2021

Cited by 5 | Viewed by 1962

Abstract

The knowledge of the air velocity distribution in the supply jets is essential when designing ventilation and air conditioning systems. In this study, we tested and analyzed the velocity distributions in the radial wall jets—these jets are commonly used in ventilated rooms. Tests [...] Read more.

The knowledge of the air velocity distribution in the supply jets is essential when designing ventilation and air conditioning systems. In this study, we tested and analyzed the velocity distributions in the radial wall jets—these jets are commonly used in ventilated rooms. Tests included jets from two ceiling diffusers of different constructions, at three airflow rates. The mean air speed distributions were measured with a 16-channel hot-sphere anemometer both in the self-similarity zone and in the terminal zone. A specially developed method of converting the mean speed to mean velocity was used. The measurement results show that the spread coefficients of the jets from both diffusers were the same, but the positions of the virtual origin were different. Due to the friction of the jet with the ceiling and the transfer of momentum to the recirculating flows, the momentum flux in the self-similarity zone decreased by up to 50%. An improved method for calculating velocity distributions in radial wall jets was developed and validated. This method takes into account the decrease of momentum, non-zero position of the jet origin, and faster velocity decrease in the terminal zone. A reliable method of predicting air velocity distribution in radial wall jets (RWJs) from ceiling diffusers may allow to properly select the diffuser size, its location, and the range of flow rate changes. The design process for variable air volume systems can be facilitated. Full article

(This article belongs to the Special Issue Ventilation and Building Energy Systems)

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17 pages, 3600 KiB

Open AccessArticle

Parametric Study of Air Infiltration in Residential Buildings—The Effect of Local Conditions on Energy Demand

by Artur Miszczuk and Dariusz Heim

Energies 2021, 14(1), 127; https://doi.org/10.3390/en14010127 - 29 Dec 2020

Cited by 12 | Viewed by 2076

Abstract

Airtightness is nowadays one of the physical parameters which determine overall building energy performance. In a wide range of states, the upper limit for air change rate at a Pa (n_a), air permeability rate at a Pa (q_a [...] Read more.

Airtightness is nowadays one of the physical parameters which determine overall building energy performance. In a wide range of states, the upper limit for air change rate at a Pa (n_a), air permeability rate at a Pa (q_a), or specific leakage rate at a Pa (w_a) is determined by the formal regulations. It should be highlighted that airtightness requirements are mainly the same around the world, disregarding any site and climatic conditions. The main goal of the presented work was to reveal the effect of individual location and surrounding infiltration rate and heat demand. The analyses were done using numerical techniques and computational models of the three buildings developed and calibrated based on the blower door test results. The compared buildings characterize by a similar geometry but differ in the air change rate at 50 Pa (n₅₀). Analyses done for different locations and levels of sheltering by surrounding elements allow the determination of the real effect of local conditions. The obtained differences in energy demand between two locations from the same climatic zone were from 70% to 90%, depending on the airtightness of the buildings. Considering different sheltered conditions, the differences for the same location can be even 200%. The obtained results allowed for the formulation of the general conclusion that building location and level of exposure could be considered in future airtightness regulations. Full article

(This article belongs to the Special Issue Ventilation and Building Energy Systems)

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12 pages, 6936 KiB

Open AccessArticle

Performance Improvement of Condensation Reduction and Removal in Heat Recovery Ventilators Using Purge Methods

by Kwiyoung Park, Dongchan Lee, Hyun Joon Chung and Yongchan Kim

Energies 2020, 13(22), 6152; https://doi.org/10.3390/en13226152 - 23 Nov 2020

Cited by 2 | Viewed by 1649

Abstract

In this study, several purge and ventilation methods are proposed to reduce and remove condensation in a heat recovery ventilator for commercial and household buildings. The effects of the airflow rate, duration of ventilation, purge interval, and return air temperature on the quantities [...] Read more.

In this study, several purge and ventilation methods are proposed to reduce and remove condensation in a heat recovery ventilator for commercial and household buildings. The effects of the airflow rate, duration of ventilation, purge interval, and return air temperature on the quantities of condensation and condensation removal in the heat recovery ventilator are analyzed. The increase in the air flow rate and return air temperature increases the condensation removal rate owing to the enhanced evaporation of the condensate. Furthermore, the reductions in the duration of ventilation and purge interval decreased the accumulation of condensate on the heat exchanger element. Based on the experimental results, optimum ventilation and purge strategies are proposed according to the outdoor temperature. The operation of the heat recovery ventilator with the proposed ventilation and purge strategies shows at least a 33% and up to an 80% reduction in the quantity of condensate compared with a given operation method. Accordingly, the proposed operation strategies can significantly reduce the growth of microorganisms and fungi and also increase the efficiency of a heat recovery ventilator. However, further investigation on the detailed performance according to the outdoor humidity and overall energy analysis is necessary to supplement the limitations of this study. Full article

(This article belongs to the Special Issue Ventilation and Building Energy Systems)

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