- Email: [email protected]
The Study Natural Ventilation by Using Buildings Windows: Case Study in a Hot Dry Climate, Ghardaïa, Algeria
Available online at www.sciencedirect.com
ScienceDirect Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Available Energy Procedia 00 (2017) 000–000
ScienceDirect ScienceDirect
www.elsevier.com/locate/procedia
Energy (2017) 000–000 475–480 EnergyProcedia Procedia139 00 (2017) www.elsevier.com/locate/procedia
International Conference On Materials And Energy 2015, ICOME 15, 19-22 May 2015, Tetouan, Morocco, and the International Conference On Materials And Energy 2016, ICOME 16, 17-20 May 2016, La Rochelle, France The 15th International Symposium on District Heating and Cooling
The Study Natural Ventilation by Using Buildings Windows: Case Assessing of using the heat demand-outdoor Studythe in afeasibility Hot Dry Climate, Ghardaïa, Algeria temperature district heatc demand forecast a, *,function for a long-term a b a a
M. Hamdani S.M.A. Bekkouche , T. Benouaz , R.Belarbi and M.K. Cherier a,b,c a a b c c Andrić *, enA.Energies PinaRenouvelables, , P. Ferrão , J. Centre Fournier ., B. Lacarrière , O. Le Corre Unité deI. Recherche Appliquée URAER, de Développement des Energies Renouvelables, CDER, 47133, a
Ghardaïa, Algeria. IN+ Center for Innovation, Technology and Policyb Research Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal University- of Tlemcen, Algeria. b c Veolia Recherche & Innovation, Avenue Dreyfous Daniel, 78520 Limay, France University291 of La Rochelle, France. c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France
Abstract Abstract Natural ventilation in buildings can create a comfortable and healthy indoor environment, and save energy used in the mechanical ventilation systems, have an important role on the balance between heating and cooling needs, It is also necessary to study the Districtcombinations heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the possible with natural resources. greenhouse emissions the building These systems requireopen highwindows investments which are returned through the heat With natural gas ventilation thefrom internal building sector. structure is cooled through and/or air vents, in order to provide a sales.induced Due toflow the or changed climate buildingforces renovation policies, heat ademand in so thethefuture could decrease, wind stack effect. It isconditions dependentand on natural to move air through building: disadvantage is that prolonging the investment return period. but on the other hand it delivers low running costs and low energy usage by reducing there is no direct control of the ventilation, The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand the electrical energy used for air-conditioning. forecast. The district of implement Alvalade, simple locatedprinciples in Lisbonbased (Portugal), was used case proven study. The is consisted of 665 The building design must on common senseas anda have their district effectiveness in traditional buildings thatItvary construction period typology. Three weather scenarios medium, high)passive and three constructions. mustinbeboth adapted to seasonal needsand (warm in winter, cool in summer) and (low, promote maximum solardistrict gain renovation and minimizescenarios losses were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were withofresults from athe dynamic heatgeometry, demand model, previously developed and validated by the authors. Incompared the first part this article, building its operation and the thermo-aerodynamics numerical model are developed The results showed that when only weather are change is considered, the margin could be applications under the TRNSYS-CONTAM environment presented. In the second part, of theerror simulation is acceptable performed for for some both cases; with (the error natural in annual demand was lower thanventilation. 20% for all weather scenarios However,door afterand introducing ventilation night and without natural The study will ensureconsidered). the night ventilation window ofrenovation the cell scenarios, the from error 20 value which are open pm increased until 8 am.up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the the number of heating hours of 22-139h during the heating season (depending on the combination of weather and ©decrease 2017 TheinAuthors. Published by Elsevier Ltd. renovation under scenarios considered). On scientific the other committee hand, function intercept increased for 7.8-12.7% per decade (depending on the Peer-review responsibility of the of ICOME 2015 and ICOME 2016. coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve Multizone the accuracy of heat demand estimations. Keywords: model, Natural Ventilation, pressure coefficient, TRNSYS-CONTAM © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +213561523809. Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected] 1876-6102 © 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the scientific committee of ICOME 2015 and ICOME 2016. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling.
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of ICOME 2015 and ICOME 2016 10.1016/j.egypro.2017.11.240
476 2
M. Hamdani et al. / Energy Procedia 139 (2017) 475–480 M. Hamdani et al. / Energy Procedia 00 (2017) 000–000
1. Introduction The natural ventilation and infiltration of a building are driven by the pressure difference across the building structure between the inside and outside; this pressure difference is a result of temperature difference between inside and outside which cause a difference in air density (stack effect). With stack effect, the movement of the air is due to the temperature difference between the inside and the outdoor. The air flow is vertical along the path of least resistance [1]. In this way when the inside temperature is higher than the outside, the warmer air rises through the building and flows out at the top, while the colder outside air comes to the bottom to replace the warmer air which is rising up through the structure. The wind pressure on buildings surfaces depends on several factors, such as wind direction, speed shape of building, location, local environment and so on. Generally the pressures are higher on the windward side and lower/negative on the leeward. In general a global effect of natural ventilation is a combination between stack effect and wind effect and it has to be supported by motorized vents to guarantee different air flows in the different periods of the days. This also depends on building height, local terrain, internal resistance to vertical air flow and flow resistance characteristics. In natural ventilation, low energy usage imposes restrictions on the shape of the building. The ventilated spaces have to be within a relatively small distance from an external wall. Moreover some drawbacks can happen. For the opening windows, such as security issues, noise and pollution are not always sufficient to ensure a ventilation rate [1]. The design phase has a fundamental importance for the building have to be designed to provide natural ventilation, considering all the factors that affect it. In summer, it is sometimes possible to enjoy the night cooling outside air to cool the building. The scenario of ventilation can evacuate the heat stored during the day in building materials (walls, furniture). In general, free cooling in the building should be done through natural ventilation, by large openings in the front surface, that is to say, a priori, the windows (one cannot imagine having to drill holes in the building vertical surfaces and floors) [1] .the free night cooling must be automated (automatic openings), regulated depending on the indoor and outdoor temperature to be effective. It is difficult to estimate the real gain through free night cooling. It depends on the building structure, ventilation mode, the size of the openings and the outside temperature [2]. The mass of the building is used for storing heat during the day to prevent overheating. This heat is then emits during the night can be achieved by increasing the airflow rate of cooler night time air through the building due to the stack effect, and the heat gain of the night-time air from heat exchange with the storage in mass, a high airflow rate. This approach basically lowers the peaks of heat gains on warm summer days [3]. 2. Numerical Modeling Coupling TRNSYS-CONTAM The major task in completing the simulation of the buildings and the airflow was the integration of the TRNSYS building model and the CONTAM airflow model. Numerical simulations of this project were performed using the coupling between the 56 types (thermal model of the building) and 97 (air flow model) TRNSYS 17 This type uses input climate data and air temperatures of the various areas provided by the type56 and determine the different rates required for the type to 56 each time. We have chosen to use the ventilation CONTAM model. This tool allows modeling the exchange ventilation in a building. The building is represented as a network of nodes which are representing a building area. The external environment is also represented by an area [4], [5]. Each network node is characterized by its pressure and temperature. The possible paths of air between the different nodes are represented by the connections between these nodes, corresponding to the leak occurring through the aeraulic components: door and opened and closed windows, cracks in the walls, inlets, etc [2]. The various flow rates are calculated by expressing the mass conservation equation at each of the network nodes. The conservation of mass is satisfied for each of the areas of the building. The temperature, and the density of the air, is known by coupling with the type56 which receives as input the flow rates calculated by CONTAM (type97). Type 97 uses a file that contains a description of areas and ventilation of the building component connections. This file is generated by CONTAM. The Type 56 calculates the temperature of the air from inside knowledge of the thermal characteristics of the building loads and ventilation rates and infiltration, type 97 evaluates meanwhile airflows between the inside areas and out from the external stresses and knowledge of internal temperatures. The flow rates of infiltration and natural ventilation are induced by the wind and thermal draft [4], [5]
M. Hamdani al. / Energy Procedia 139 (2017) 475–480 M. Hamdani et al. et / Energy Procedia 00 (2017) 000–000
477 3
Fig. 1. Coupling TRNSYS-CONTAM
3. Presentation and Building modeling The building climate is hot and dry in the summer with temperatures variation between a maximum of around 45 °C and a minimum of 20 °C, thus giving a large temperature swing. Winter temperatures vary between a maximum of 24 °C and a minimum of 0 °C. Its normal temperature in January is 10.4 °C and 36.3 °C in July. The average annual range is about 12.2 ° amplitudes of monthly average temperatures. They are more moderate in winter than in summer (average 11° in winter cons 13.5° in summer). The monthly maximum amplitudes are larger in summer than in winter fluctuates around 20 °C. Solar radiation is intense throughout the year with a maximum of 700 Wm-2 in winter and 1000 Wm-2 in summer, measured on the horizontal surface [6]-[10]. The study was carried out on a building in Ghardaïa. The exterior envelope, apart from contributing to the energy savings during the building life by controlling the energy exchange between indoor space and environment developed a comfortable indoor environment [6]-[10]. Fig. 2 is a schematic outline of apartment building, the house has a net area of 71.3 m2, and wall heights are equal to 2.8 m while the other dimensions are shown in detail in Fig. 2.
Fig. 2. The house plan
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M. Hamdani et al. / Energy Procedia 139 (2017) 475–480 M. Hamdani et al. / Energy Procedia 00 (2017) 000–000
In our model, the openings are on both north and south surface for the building with a main door on the East side, during the day the temperature of the outside air is greater than that of the interior. To eliminate the exchange ventilation with outdoor air, the windows and the door will be closed during the day, opened the night (the window and the door will be closed is the time or TaiTao) [11]. By numerical simulation of the model is determined corresponding to each case. For better ventilation of the interior during the night, the door and the window will be on two different opposite wall, it is necessary to seek their guidance for minimized heat gain. During the day the windows and the door will be closed. heat transfer is carried out as the case of an opaque member. To calculate the temperature in the inside face of the window and the door, the same method and the same steps in the case of wall are followed [6]-[10]. 4. Build Energy Model in TRNSYS The thermal simulation of the building was performed by coupling a thermal model developed under TRNSYS and ventilation via the CONTAM software model. As illustrated in Fig. 3, the building is modeled as a singlebuilding area in a "ventilation" model which calculates the ventilation rate and the air permeability through the casing [12].
Fig. 3. Airflow and pressure distributions in the six-zone calculated by CONTAM
To calculate the dynamic air infiltration rates, CONTAM is used to create the multi-zone model for the case study building. To build the multi-zone model in CONTAM, one needs to zone the building reasonably to the level that it is not too complicated while not affecting the accuracy of results. Second, we calculate the wind pressure coefficient on each surface. To calculate the wind pressure coefficient of each surface, Urban context plays a very important role in wind pressure profile calculation [12] . Fig. 4 shows the temperatures in the Open Space for summer days from the current model. We also note that the indoor temperature is higher than the outside at night with a difference up to 2.5 ° C. The interest of the night ventilation is to use this temperature difference to create an aspiration of fresh air into the building to cool the building during the night to avoid overheating during the day effect. To assess the impact of the phenomenon, it is first necessary to study the physics of the phenomenon involved is commonly called the stack effect. Natural ventilation gives excellent results in terms of summer comfort. The study shows that it would be wise to use this process during the summer months especially as it requires no cooling energy. The variation in the size of the opening would also improve thermal comfort.
M. Hamdani al. / Energy Procedia 139 (2017) 475–480 M. Hamdani et al.et/ Energy Procedia 00 (2017) 000–000
4795
Fig. 4. Comparison of indoor temperatures in scenarios with different ventilation
5. Conclusion
Thermo- aeraulic modeling is essential for establishing overall thermal performance values and understand how different assembly designs perform under different interior and exterior climate conditions. This tool is used to evaluate the performance of a proposed architecture for a real building located in a very hot climate. The object of the Natural night ventilation is to discharge a maximum during the night, the heat accumulated in the building material and for strong absorption of heat during the day this is especially building energy management regulated depending on weather conditions. It is timely today. Free cooling, which is to refresh the local at night to avoid air conditioning expenditures, provides another illustration Thus, with simulation tools. The models are made using TRNSYS coupling with CONTAM. Four ventilation scenarios are studied to know the most thermal comfort scenario. From the perspective of thermal engineering, windows are a special gate in the building envelope too. Their global heat transfer coefficient is typically 3 to 10 times higher than the equivalent for the opaque envelope. Therefore, they let the heat flow more easily between the indoor and the outdoor. In buildings located in climates with cold winters, the heat loss through windows can be quite significant. However, windows are also permeable to the penetration of solar radiation. Thus, if properly orientated, they can also contribute with a “free heating energy”
in winter time. In the summer time, however, the penetration of solar radiation may be a concern and contribute to overheating or increased energy demand for cooling. In the opposite trend, windows can contribute to cool the building through ventilation free-cooling, including night ventilation
480 6
M. Hamdani et al. / Energy Procedia 139 (2017) 475–480 M. Hamdani et al. / Energy Procedia 00 (2017) 000–000
References [1] Ghjuvan Antone Faggianelli ,Rafraîchissement par la ventilation naturelle traversante des bâtiments en climat méditerranéen, Université corse Pascal Paoli, Thèses 2014. [2] Barhoun Hayssam, nfluence des transferts aérauliques dans les parois sur leurs performances thermiques, 2006 , Thèses l'INSA de Lyon. [3] Bart Macquoy, Natural ventilation based bioclimatic redevelopment - 1/14 - Building transformation and improvement into an integrated energy efficient multifunctional design ,January 14th, 2014. [4] R.Lapisa, Effect of ground thermal inertia on the energy balance of commercial low-rise buildings, Building Simulation 2013, Chambéry, France. [5] Etude de l’impact des « cool roofs », de la ventilation naturelle et de l’inertie thermique du sol sur les performances énergétiques de bâtiments commerciaux), Université de La Rochelle, France. [6] S.M.A. Bekkouche, T. Benouaz, M.K. Cherier, M. Hamdani, N. Benamrane, M.R. Yaiche, Thermal resistances of local building materials and their effect upon the interior temperatures case of a building located in Ghardaïa region, Construction and Building Materials 52 (2014) 59–70. [7] M. Hamdani, S. M. A. Bekkouche, T. Benouaz, R. Belarbi, M. K. Cherier, Minimization of indoor temperatures and total solar insolation by optimizing the building orientation in hot climate, Engineering Structures And Technologies, Taylor & Francis: ISSN 2029-882X / eISSN 20298838 2014 6(3): 131–149, doi:10.3846/2029882X.2012.988756. [8] S. M. A. Bekkouche, T. Benouaz, M. K. Cherier, M. Hamdani, M. R. Yaiche et N Benamrane, "Influence of the Compactness Index to Increase the Internal Temperature of a Building in Saharan Climate", Elsevier, Energy and Buildings vol.66 (2013) pp. 678–687. [9] S. M. A. Bekkouche, T. Benouaz, M. K. Cherier, M. Hamdani, R. M Yaiche, R. Khanniche (2013), Influence of building orientation on internal temperature in Saharan climates, building located in Ghardaïa region (Algeria), International Scientific Journal, Thermal Science, 2013, Vol. 17, No. 2, pp. 349-364. [10] S. M. A. Bekkouche, T. Benouaz, M. R. Yaiche, M. K. Cherier, M. Hamdani, F. Chellali, Introduction to Control of Solar Gain and Internal Temperatures by Thermal Insulation, Proper Orientation and Eaves, Elsevier, Energy and Buildings vol.43 (2011) pp. 2414–2421. [11] Bencheikh Hamida, Etude et Realisation D’un Systeme de Refroidissement Passif en Utilisant une toiture radio-evaporative dans les climats chauds et arides, universite mentouri de constantine, these doctorat, 2007. [12] CONTAM,http://www.bfrl.nist.gov/IAQanalysis/CONTAM/. [13] D. Cóstola, B. Blocken, J.L.M. Hensen, Overview of pressure coefficient data in building energy simulation programs ,Building and enveronement,44(10),2007-2036.
ScienceDirect Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Available Energy Procedia 00 (2017) 000–000
ScienceDirect ScienceDirect
www.elsevier.com/locate/procedia
Energy (2017) 000–000 475–480 EnergyProcedia Procedia139 00 (2017) www.elsevier.com/locate/procedia
International Conference On Materials And Energy 2015, ICOME 15, 19-22 May 2015, Tetouan, Morocco, and the International Conference On Materials And Energy 2016, ICOME 16, 17-20 May 2016, La Rochelle, France The 15th International Symposium on District Heating and Cooling
The Study Natural Ventilation by Using Buildings Windows: Case Assessing of using the heat demand-outdoor Studythe in afeasibility Hot Dry Climate, Ghardaïa, Algeria temperature district heatc demand forecast a, *,function for a long-term a b a a
M. Hamdani S.M.A. Bekkouche , T. Benouaz , R.Belarbi and M.K. Cherier a,b,c a a b c c Andrić *, enA.Energies PinaRenouvelables, , P. Ferrão , J. Centre Fournier ., B. Lacarrière , O. Le Corre Unité deI. Recherche Appliquée URAER, de Développement des Energies Renouvelables, CDER, 47133, a
Ghardaïa, Algeria. IN+ Center for Innovation, Technology and Policyb Research Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal University- of Tlemcen, Algeria. b c Veolia Recherche & Innovation, Avenue Dreyfous Daniel, 78520 Limay, France University291 of La Rochelle, France. c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France
Abstract Abstract Natural ventilation in buildings can create a comfortable and healthy indoor environment, and save energy used in the mechanical ventilation systems, have an important role on the balance between heating and cooling needs, It is also necessary to study the Districtcombinations heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the possible with natural resources. greenhouse emissions the building These systems requireopen highwindows investments which are returned through the heat With natural gas ventilation thefrom internal building sector. structure is cooled through and/or air vents, in order to provide a sales.induced Due toflow the or changed climate buildingforces renovation policies, heat ademand in so thethefuture could decrease, wind stack effect. It isconditions dependentand on natural to move air through building: disadvantage is that prolonging the investment return period. but on the other hand it delivers low running costs and low energy usage by reducing there is no direct control of the ventilation, The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand the electrical energy used for air-conditioning. forecast. The district of implement Alvalade, simple locatedprinciples in Lisbonbased (Portugal), was used case proven study. The is consisted of 665 The building design must on common senseas anda have their district effectiveness in traditional buildings thatItvary construction period typology. Three weather scenarios medium, high)passive and three constructions. mustinbeboth adapted to seasonal needsand (warm in winter, cool in summer) and (low, promote maximum solardistrict gain renovation and minimizescenarios losses were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were withofresults from athe dynamic heatgeometry, demand model, previously developed and validated by the authors. Incompared the first part this article, building its operation and the thermo-aerodynamics numerical model are developed The results showed that when only weather are change is considered, the margin could be applications under the TRNSYS-CONTAM environment presented. In the second part, of theerror simulation is acceptable performed for for some both cases; with (the error natural in annual demand was lower thanventilation. 20% for all weather scenarios However,door afterand introducing ventilation night and without natural The study will ensureconsidered). the night ventilation window ofrenovation the cell scenarios, the from error 20 value which are open pm increased until 8 am.up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the the number of heating hours of 22-139h during the heating season (depending on the combination of weather and ©decrease 2017 TheinAuthors. Published by Elsevier Ltd. renovation under scenarios considered). On scientific the other committee hand, function intercept increased for 7.8-12.7% per decade (depending on the Peer-review responsibility of the of ICOME 2015 and ICOME 2016. coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve Multizone the accuracy of heat demand estimations. Keywords: model, Natural Ventilation, pressure coefficient, TRNSYS-CONTAM © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +213561523809. Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected] 1876-6102 © 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the scientific committee of ICOME 2015 and ICOME 2016. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling.
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of ICOME 2015 and ICOME 2016 10.1016/j.egypro.2017.11.240
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M. Hamdani et al. / Energy Procedia 139 (2017) 475–480 M. Hamdani et al. / Energy Procedia 00 (2017) 000–000
1. Introduction The natural ventilation and infiltration of a building are driven by the pressure difference across the building structure between the inside and outside; this pressure difference is a result of temperature difference between inside and outside which cause a difference in air density (stack effect). With stack effect, the movement of the air is due to the temperature difference between the inside and the outdoor. The air flow is vertical along the path of least resistance [1]. In this way when the inside temperature is higher than the outside, the warmer air rises through the building and flows out at the top, while the colder outside air comes to the bottom to replace the warmer air which is rising up through the structure. The wind pressure on buildings surfaces depends on several factors, such as wind direction, speed shape of building, location, local environment and so on. Generally the pressures are higher on the windward side and lower/negative on the leeward. In general a global effect of natural ventilation is a combination between stack effect and wind effect and it has to be supported by motorized vents to guarantee different air flows in the different periods of the days. This also depends on building height, local terrain, internal resistance to vertical air flow and flow resistance characteristics. In natural ventilation, low energy usage imposes restrictions on the shape of the building. The ventilated spaces have to be within a relatively small distance from an external wall. Moreover some drawbacks can happen. For the opening windows, such as security issues, noise and pollution are not always sufficient to ensure a ventilation rate [1]. The design phase has a fundamental importance for the building have to be designed to provide natural ventilation, considering all the factors that affect it. In summer, it is sometimes possible to enjoy the night cooling outside air to cool the building. The scenario of ventilation can evacuate the heat stored during the day in building materials (walls, furniture). In general, free cooling in the building should be done through natural ventilation, by large openings in the front surface, that is to say, a priori, the windows (one cannot imagine having to drill holes in the building vertical surfaces and floors) [1] .the free night cooling must be automated (automatic openings), regulated depending on the indoor and outdoor temperature to be effective. It is difficult to estimate the real gain through free night cooling. It depends on the building structure, ventilation mode, the size of the openings and the outside temperature [2]. The mass of the building is used for storing heat during the day to prevent overheating. This heat is then emits during the night can be achieved by increasing the airflow rate of cooler night time air through the building due to the stack effect, and the heat gain of the night-time air from heat exchange with the storage in mass, a high airflow rate. This approach basically lowers the peaks of heat gains on warm summer days [3]. 2. Numerical Modeling Coupling TRNSYS-CONTAM The major task in completing the simulation of the buildings and the airflow was the integration of the TRNSYS building model and the CONTAM airflow model. Numerical simulations of this project were performed using the coupling between the 56 types (thermal model of the building) and 97 (air flow model) TRNSYS 17 This type uses input climate data and air temperatures of the various areas provided by the type56 and determine the different rates required for the type to 56 each time. We have chosen to use the ventilation CONTAM model. This tool allows modeling the exchange ventilation in a building. The building is represented as a network of nodes which are representing a building area. The external environment is also represented by an area [4], [5]. Each network node is characterized by its pressure and temperature. The possible paths of air between the different nodes are represented by the connections between these nodes, corresponding to the leak occurring through the aeraulic components: door and opened and closed windows, cracks in the walls, inlets, etc [2]. The various flow rates are calculated by expressing the mass conservation equation at each of the network nodes. The conservation of mass is satisfied for each of the areas of the building. The temperature, and the density of the air, is known by coupling with the type56 which receives as input the flow rates calculated by CONTAM (type97). Type 97 uses a file that contains a description of areas and ventilation of the building component connections. This file is generated by CONTAM. The Type 56 calculates the temperature of the air from inside knowledge of the thermal characteristics of the building loads and ventilation rates and infiltration, type 97 evaluates meanwhile airflows between the inside areas and out from the external stresses and knowledge of internal temperatures. The flow rates of infiltration and natural ventilation are induced by the wind and thermal draft [4], [5]
M. Hamdani al. / Energy Procedia 139 (2017) 475–480 M. Hamdani et al. et / Energy Procedia 00 (2017) 000–000
477 3
Fig. 1. Coupling TRNSYS-CONTAM
3. Presentation and Building modeling The building climate is hot and dry in the summer with temperatures variation between a maximum of around 45 °C and a minimum of 20 °C, thus giving a large temperature swing. Winter temperatures vary between a maximum of 24 °C and a minimum of 0 °C. Its normal temperature in January is 10.4 °C and 36.3 °C in July. The average annual range is about 12.2 ° amplitudes of monthly average temperatures. They are more moderate in winter than in summer (average 11° in winter cons 13.5° in summer). The monthly maximum amplitudes are larger in summer than in winter fluctuates around 20 °C. Solar radiation is intense throughout the year with a maximum of 700 Wm-2 in winter and 1000 Wm-2 in summer, measured on the horizontal surface [6]-[10]. The study was carried out on a building in Ghardaïa. The exterior envelope, apart from contributing to the energy savings during the building life by controlling the energy exchange between indoor space and environment developed a comfortable indoor environment [6]-[10]. Fig. 2 is a schematic outline of apartment building, the house has a net area of 71.3 m2, and wall heights are equal to 2.8 m while the other dimensions are shown in detail in Fig. 2.
Fig. 2. The house plan
478 4
M. Hamdani et al. / Energy Procedia 139 (2017) 475–480 M. Hamdani et al. / Energy Procedia 00 (2017) 000–000
In our model, the openings are on both north and south surface for the building with a main door on the East side, during the day the temperature of the outside air is greater than that of the interior. To eliminate the exchange ventilation with outdoor air, the windows and the door will be closed during the day, opened the night (the window and the door will be closed is the time or Tai
Fig. 3. Airflow and pressure distributions in the six-zone calculated by CONTAM
To calculate the dynamic air infiltration rates, CONTAM is used to create the multi-zone model for the case study building. To build the multi-zone model in CONTAM, one needs to zone the building reasonably to the level that it is not too complicated while not affecting the accuracy of results. Second, we calculate the wind pressure coefficient on each surface. To calculate the wind pressure coefficient of each surface, Urban context plays a very important role in wind pressure profile calculation [12] . Fig. 4 shows the temperatures in the Open Space for summer days from the current model. We also note that the indoor temperature is higher than the outside at night with a difference up to 2.5 ° C. The interest of the night ventilation is to use this temperature difference to create an aspiration of fresh air into the building to cool the building during the night to avoid overheating during the day effect. To assess the impact of the phenomenon, it is first necessary to study the physics of the phenomenon involved is commonly called the stack effect. Natural ventilation gives excellent results in terms of summer comfort. The study shows that it would be wise to use this process during the summer months especially as it requires no cooling energy. The variation in the size of the opening would also improve thermal comfort.
M. Hamdani al. / Energy Procedia 139 (2017) 475–480 M. Hamdani et al.et/ Energy Procedia 00 (2017) 000–000
4795
Fig. 4. Comparison of indoor temperatures in scenarios with different ventilation
5. Conclusion
Thermo- aeraulic modeling is essential for establishing overall thermal performance values and understand how different assembly designs perform under different interior and exterior climate conditions. This tool is used to evaluate the performance of a proposed architecture for a real building located in a very hot climate. The object of the Natural night ventilation is to discharge a maximum during the night, the heat accumulated in the building material and for strong absorption of heat during the day this is especially building energy management regulated depending on weather conditions. It is timely today. Free cooling, which is to refresh the local at night to avoid air conditioning expenditures, provides another illustration Thus, with simulation tools. The models are made using TRNSYS coupling with CONTAM. Four ventilation scenarios are studied to know the most thermal comfort scenario. From the perspective of thermal engineering, windows are a special gate in the building envelope too. Their global heat transfer coefficient is typically 3 to 10 times higher than the equivalent for the opaque envelope. Therefore, they let the heat flow more easily between the indoor and the outdoor. In buildings located in climates with cold winters, the heat loss through windows can be quite significant. However, windows are also permeable to the penetration of solar radiation. Thus, if properly orientated, they can also contribute with a “free heating energy”
in winter time. In the summer time, however, the penetration of solar radiation may be a concern and contribute to overheating or increased energy demand for cooling. In the opposite trend, windows can contribute to cool the building through ventilation free-cooling, including night ventilation
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