hig.sePublications
Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 38) Show all publications
Cehlin, M., Karimipanah, T., Larsson, U. & Ameen, A. (2019). Comparing thermal comfort and air quality performance of two active chilled beam systems in an open-plan office. Journal of Building Engineering, 22, 56-65
Open this publication in new window or tab >>Comparing thermal comfort and air quality performance of two active chilled beam systems in an open-plan office
2019 (English)In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 22, p. 56-65Article in journal (Refereed) Published
Abstract [en]

The traditional air distribution and supply devices in ventilated rooms are not always able to effectively remove excess heat from the space. Therefore, chilled beams, especially the active systems, are used to achieve the desired cooling demand. The focus of this paper was the potential benefit of a newly designed active chilled beam (ACB) system, to improve heat removal effectiveness local thermal condition and indoor air quality in the occupants’ breathing zone. The system based on 1-way flow design (1W-ACB) was installed in an open-plan office and its performance was studied by analysing the temperatures, velocities and tracer gas concentrations in predetermined risky zones. The system was compared against a traditional 4-way flow design (4W-ACB).

The obtained results showed that heat removal effectiveness was slightly higher for the 1W-ACB system compared to the 4W-ACB system. The local thermal condition was very good close to the workstations when using 1W-ACB. The benefits of the new system were also shown in the occupied zone by analysing the mean age of air and air-change effectiveness (ACE) in the breathing level at the workstation locations. The 1W-ACB system provided air with lower mean age (fresher air), and therefore higher ACE, near the breathing zone at the workstations compared to the 4W-ACB. On the other hand, the 4W-ACB system had the advantage of providing high thermal and mean age of air uniformity throughout the room.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Active Chilled Beam, Air Change Effectiveness, Heat Removal Effectiveness
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-28583 (URN)10.1016/j.jobe.2018.11.013 (DOI)2-s2.0-85057839765 (Scopus ID)
Available from: 2018-11-22 Created: 2018-11-22 Last updated: 2019-01-07Bibliographically approved
Vachaparambil, K. J., Cehlin, M. & Karimipanah, T. (2018). Comparative Numerical Study of the Indoor Climate for Mixing and Confluent Jet Ventilation Systems in an Open-plan Office. In: Proceedings of the 4th international Conference on Building Energy & Environment: . Paper presented at COBEE2018, 4th international Conference on Building Energy & Environment, 5-9 February 2018, Melbourne, Australia (pp. 73-78). Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia
Open this publication in new window or tab >>Comparative Numerical Study of the Indoor Climate for Mixing and Confluent Jet Ventilation Systems in an Open-plan Office
2018 (English)In: Proceedings of the 4th international Conference on Building Energy & Environment, Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia , 2018, p. 73-78Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia, 2018
Keywords
Confluent jet ventilation
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-26568 (URN)978-0-646-98213-7 (ISBN)
Conference
COBEE2018, 4th international Conference on Building Energy & Environment, 5-9 February 2018, Melbourne, Australia
Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2018-05-21Bibliographically approved
Andersson, H., Cehlin, M. & Moshfegh, B. (2018). Experimental and numerical investigations of a new ventilation supply device based on confluent jets. Building and Environment, 137, 18-33
Open this publication in new window or tab >>Experimental and numerical investigations of a new ventilation supply device based on confluent jets
2018 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 137, p. 18-33Article in journal (Refereed) Published
Abstract [en]

In developed countries, heating, ventilation, air conditioning (HVAC) systems account for more than 10% of national energy use. The primary function of a HVAC system is to create proper indoor environment. A number of ventilation strategies have been developed to minimize HVAC systems’ energy use whilst still maintaining a good indoor environment. Among these strategies are confluent jet ventilation and variable air volume. In this study, an air supply device with a novel nozzle design that uses both of the above-mentioned strategies was investigated both experimentally and numerically at three different airflow rates. The results from the numerical investigation using the SST k - ω turbulence model regarding velocities and flow patterns are validated by experimental data carried out by Laser Doppler Anemometry. The results from both studies show that the flow pattern and velocity in each nozzle is directly dependent on the total airflow rate. However, the flow pattern does not vary between the three different airflow rates. The numerical investigation shows that velocity profiles for each nozzle have the same pattern regardless of the airflow rate, but the magnitude of the velocity profile increases as the airflow increases. Thus, a supply device of this kind could be used for variable air volume and produce confluent jets for the airflow rates investigated.

Keywords
Confluent jets, Laser Doppler anemometry, SST k, Validation study, Ventilation supply device, ω turbulence model
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-26571 (URN)10.1016/j.buildenv.2018.03.038 (DOI)000433649700003 ()2-s2.0-85044917956 (Scopus ID)
Funder
Knowledge Foundation
Note

Funding: University of Gavle, Repus Ventilation AB and the Knowledge Foundation

Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2019-02-13Bibliographically approved
Cehlin, M. (2018). Mapping tracer gas concentrations using a modified Low Third Derivative method: numerical study. The International Journal of Ventilation
Open this publication in new window or tab >>Mapping tracer gas concentrations using a modified Low Third Derivative method: numerical study
2018 (English)In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044Article in journal (Refereed) Epub ahead of print
Abstract [en]

In indoor applications, computed tomography is the process of transforming a network of intersecting attenuation measurements into a spatially resolved two-dimensional concentration map. In this study the Low Third Derivative method (LTD) was numerically evaluated and optimized for different conditions. A modified version of the LTD algorithm (LTDm) was proposed and evaluated against the original version. Eight test maps were reconstructed under different conditions, such as weight ratio, pixel resolution, beam density and measurement noise. Performance of both LTD algorithms was found to be intimately related to the number of peaks and complexity in the test map and the steepness of the peaks. The LTDm algorithm improved the quality, especially for concentration maps including steep gradients and regions with very low concentrations. The LTDm method heavily lessened aliasing distortions and efficiently minimized the effects of noise.

Keywords
Computed tomography, numerical study, reconstruction algorithm, tracer gas distribution
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-26569 (URN)10.1080/14733315.2018.1462935 (DOI)2-s2.0-85045619672 (Scopus ID)
Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2018-06-05Bibliographically approved
Haghshenas, S., Sajadi, B. & Cehlin, M. (2018). Multi-Objective Optimization of Impinging Jet Ventilation Systems: Taguchi Based CFD Method. Building Simulation, 11(6), 1207-1214
Open this publication in new window or tab >>Multi-Objective Optimization of Impinging Jet Ventilation Systems: Taguchi Based CFD Method
2018 (English)In: Building Simulation, ISSN 1996-3599, E-ISSN 1996-8744, Vol. 11, no 6, p. 1207-1214Article in journal (Refereed) Published
Abstract [en]

This paper presents a Taguchi method-based approach that can optimize the operating performance of impinging jet ventilation (IJV) systems with limited computational fluid dynamics (CFD) simulation results. The Taguchi optimization calculation finds the best operating design for the weighted overall objective function as a presenter of the multi-objective function problem. The method is used to optimize the operating characteristics of an IJV system considering the factors of supply air temperature, level of the return air vent and percentage of the air exhausted through the ceiling to achieve an overall best performance of thermal comfort, indoor air quality (IAQ) and system energy performance as the objective functions. The study indicates the contribution percentage for each factor in each objective function. The level of the return air vent, the supply air temperature, and the percentage of air exhausted through the ceiling have a contribution of 35.8%, 28.5%, and 35.8% in the objective functions, respectively. Based on the results, the best performance of the IJV system happens when the inlet air temperature is 18 °C, the height of the return air vent is 2 m above the floor, and the percentage of air exhausted through the ceiling is 22.5%.

Keywords
impinging jet ventilation (IJV), thermal comfort, indoor air quality, energy performance, Taguchi method, optimization
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-26570 (URN)10.1007/s12273-018-0450-z (DOI)000451924600010 ()2-s2.0-85056574558 (Scopus ID)
Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2019-01-07Bibliographically approved
Cehlin, M., Larsson, U. & Chen, H. (2018). Numerical investigation of Air Change Effectiveness in an Office Room with Impinging Jet Ventilation. In: K. Inthavong*, C.P Cheung, G. Yeoh, J.Y. Tu (Ed.), Proceedings of the 4th international Conference on Building Energy & Environment: . Paper presented at COBEE2018, 4th international Conference on Building Energy & Environment,5-9 February 2018, Melbourne, Australia (pp. 641-646). Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia
Open this publication in new window or tab >>Numerical investigation of Air Change Effectiveness in an Office Room with Impinging Jet Ventilation
2018 (English)In: Proceedings of the 4th international Conference on Building Energy & Environment / [ed] K. Inthavong*, C.P Cheung, G. Yeoh, J.Y. Tu, Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia , 2018, p. 641-646Conference paper, Published paper (Refereed)
Abstract [en]

Providing occupant comfort and health with minimum use of energy is the ultimate purpose of heating, ventilating and air conditioning systems. This paper presents the air-change effectiveness (ACE) within a typical office room using impinging jet ventilation (IJV ) in combination with chilled ceiling (CC) under different heat loads ranging from 6.5 - 51 W per square meter floor area. In this study, a validated CFD model based on the v2f turbulence model is used for the prediction of air flow pattern and ACE. The interaction effect of chilled ceiling and heat sources results in a complex flow with air circulation. The thermal plumes and air circulation in the room result in a variation of ACE within the room but also close to the occupant. For all studied cases, ACE is above 1.2 close to the occupants, indicating that IJV is more energy efficient than mixing ventilation.

Place, publisher, year, edition, pages
Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia, 2018
Keywords
Impinging jet ventilation
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-26567 (URN)978-0-646-98213-7 (ISBN)
Conference
COBEE2018, 4th international Conference on Building Energy & Environment,5-9 February 2018, Melbourne, Australia
Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2018-09-17Bibliographically approved
Khosravi Bakhtiari, H., Cehlin, M. & Akander, J. (2018). Thermal Comfort in Office Rooms in a Historic Building with Modernized HVAC Systems. In: Kiao Inthavong,Chi Pok Cheung, Guan Yeoh, Jiyuan Tu (Ed.), Proceedings of the 4th International Conference On Building Energy & Environment, COBEE 2018: RMIT University, Melbourne, Australia, Feb 5-9th 2018. Paper presented at 4th International Conference On Building Energy & Environment, COBEE 2018, 5-9 February 2018, Melbourne, Australia (pp. 683-688). Melbourne: Conference On Building Energy & Environment, Article ID 230.
Open this publication in new window or tab >>Thermal Comfort in Office Rooms in a Historic Building with Modernized HVAC Systems
2018 (English)In: Proceedings of the 4th International Conference On Building Energy & Environment, COBEE 2018: RMIT University, Melbourne, Australia, Feb 5-9th 2018 / [ed] Kiao Inthavong,Chi Pok Cheung, Guan Yeoh, Jiyuan Tu, Melbourne: Conference On Building Energy & Environment , 2018, p. 683-688, article id 230Conference paper, Published paper (Refereed)
Abstract [en]

SUMMARY

Envelopes with low thermal performance are common characteristics in European historic buildings, leading to higher energy demand and insufficient thermal comfort. This paper presents the results of a study on thermal comfort in the historic office building of City Hall in Gävle, Sweden. It is equipped with two modern heat recovery ventilation systems with displacement ventilation supply devices in offices. District heating network heats the building via pre-heat supply air and radiators. Summer cooling comes from electric heat pump, rejecting heat into the exhaust ventilation air. A building management system controls HVAC equipment. Methodology includes on-site measurements, data logging on management system and evaluating the occupants’ perception of a summer and a winter period indoor environment using a standardized questionnaire. In conclusion, thermal comfort in this historic building is poor although it is equipped with modern ventilation systems and there should be possibilities for improving comfort, by improved control strategies.

Keywords — Historic Buildings, On-site Measurements, Standardized Questionnaire, Thermal Comfort

Place, publisher, year, edition, pages
Melbourne: Conference On Building Energy & Environment, 2018
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-26550 (URN)978-0-646-98213-7 (ISBN)
Conference
4th International Conference On Building Energy & Environment, COBEE 2018, 5-9 February 2018, Melbourne, Australia
Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-06-05Bibliographically approved
Akander, J., Cehlin, M. & Moshfegh, B. (2017). Assessing the Myths on Energy Efficiency When Retrofitting Multifamily Buildings in a Northern Region (1ed.). In: Ali Sayigh (Ed.), Sustainable High Rise Buildings in Urban Zones: Advantages, Challenges, and Global Case Studies (pp. 139-161). Cham: Springer Publishing Company
Open this publication in new window or tab >>Assessing the Myths on Energy Efficiency When Retrofitting Multifamily Buildings in a Northern Region
2017 (English)In: Sustainable High Rise Buildings in Urban Zones: Advantages, Challenges, and Global Case Studies / [ed] Ali Sayigh, Cham: Springer Publishing Company, 2017, 1, p. 139-161Chapter in book (Other academic)
Abstract [en]

In the light of EU’s requirements to achieve a major cut in energy use by 2050, Sweden has the same target. The built environment must by 2020 reduce energy use by 20 and 50 % by 2050. The size of the future building stock will naturally increase and regardless of how energy efficient future buildings will be, the energy performance of the old stock must be improved in order to reach those goals. In major renovation projects involving multifamily buildings in large residential areas in the cities, 50 % reduction can be achieved. This is cost-effective and profitable even if the rent is increased.

Gävleborg is a sparse region in the North, with few cities. Multifamily buildings are generally much smaller than in large cities and owners are reluctant to impose changes that increase rents due to the housing situation in the region. In consequence, the Regional Council and the University of Gävle set out to assess the potential and feasibility of reducing energy use and carbon dioxide emissions in this region’s multifamily buildings. Eleven real buildings were investigated, each having various ownership forms, different technical attributes and heating sources. Energy audits and measurements were conducted to assess the condition of each building. Performances of the buildings and proposed improvements were simulated with building energy simulation programs, whilst life cycle cost analyses were conducted to study viability. Carbon dioxide emission (CO2) reductions were estimated for each improvement.

Based on the results, a concluding discussion is made on whether or not some myths on energy use and retrofitting are true. The following is concluded: It is possible to reach a 50 % reduction, but it is not economical with the costs involved and with today’s energy prices and moderate price increase over time.

Retrofitting or improvements made in the building’s services systems (HVAC) are more economical than actions taken to improve performance of building by constructions. HVAC improvements give about 20 % reduction in energy use. However, mechanical ventilation systems with heat recuperation are not economical, though these may or may not substantially reduce use of thermal energy.

Solar energy is, despite the latitude of the region, economically viable—especially PV solar energy. Photovoltaic panels (PVs) are becoming viable—the combination of PVs and district heating is beneficial since saving electricity is more important than thermal energy in district-heated areas.

Place, publisher, year, edition, pages
Cham: Springer Publishing Company, 2017 Edition: 1
Keywords
Retrofit, Multifamily buildings, Energy savings
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-23209 (URN)10.1007/978-3-319-17756-4_8 (DOI)2-s2.0-85028882688 (Scopus ID)978-3-319-17755-7 (ISBN)978-3-319-17756-4 (ISBN)
Projects
EKG-f
Funder
Swedish Energy Agency
Note

Funders of the EKG project: Swedish Energy Agency, Regional Council of Gävleborg and University of Gävle. 

Available from: 2017-01-02 Created: 2017-01-02 Last updated: 2018-03-13Bibliographically approved
Lane, A.-L., Cehlin, M. & Gustavsson, T. (2017). ByggaE – Method for Quality Assurance of Energy Efficient Buildings. International Journal of Energy Production and Management, 2(2), 133-139
Open this publication in new window or tab >>ByggaE – Method for Quality Assurance of Energy Efficient Buildings
2017 (English)In: International Journal of Energy Production and Management, ISSN 2056-3272, E-ISSN 2056-3280, Vol. 2, no 2, p. 133-139Article in journal (Refereed) Published
Abstract [en]

Policies for energy efficiency requirements in buildings have become more stringent according to EU2020 goals. Despite policy regulations, requirements for energy efficiency are not met in many new buildings. Some of the reasons for this energy performance gap are related to the building process. The aim with this paper is to describe a purposed method for quality assurance of sustainable buildings according to energy efficiency. The proposed method is called ByggaE, where ‘Bygga’ is the Swedish word for ‘build’ and E is the first letter in ‘energy efficient’. It is a tool intended to lower the energy performance gap related to the building process by guiding the client and providers through the process to fulfill goals. The essence of ByggaE is the formulation of requirements by the client and the working process of identifying, handling and following up critical constructions and key issues. This working process involves all participants in the building project by using appropriate quality guidelines and checklists for documentation, communication and verification. ByggaE is a step forward ensuring that the building fulfills the defined functions and that conscious decisions are taken when goals have to be changed during the building project. The next steps are to ensure the usefulness of the method in practice by more testing and to spread knowledge about the method.

Place, publisher, year, edition, pages
WIT Press, 2017
Keywords
energy efficient buildings, quality assurance, building process, energy performance gap
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-25477 (URN)10.2495/EQ-V2-N2-133-139 (DOI)
Funder
Knowledge Foundation
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2018-03-13Bibliographically approved
Joudi, A., Cehlin, M., Svedung, H., Rönnelid, M. & Moshfegh, B. (2017). Numerical and experimental investigation of the influence of infrared reflective interior surfaces on building temperature distributions. Indoor + Built Environment, 26(3), 355-367
Open this publication in new window or tab >>Numerical and experimental investigation of the influence of infrared reflective interior surfaces on building temperature distributions
Show others...
2017 (English)In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 26, no 3, p. 355-367Article in journal (Refereed) Published
Abstract [en]

Radiative properties of interior surfaces can affect not only the building heat flux but also the indoor environment, the latter of which has not been thoroughly investigated. The aim of this study is to analyse the effect of surface emissivity on indoor air and surface temperature distributions in a test cabin with reflective interior surfaces. This was done by comparing experimental and simulation data of the test cabin with that of a normal cabin. This study employs transient computational fluid dynamics (CFD) using re-normalisation group (RNG) k-epsilon model, surface-to-surface radiation model and an enhanced wall function. Boundary conditions were assigned to exterior surfaces under variable outdoor conditions. The numerical and the measurement results indicate that using interior reflective surfaces will affect the indoor air temperature distribution by increasing the vertical temperature gradient depending on the time of the day. CFD simulations with high spatial resolution results show increased interior surface temperature gradients consistent with the increased vertical air temperature gradient. The influence of reflective surfaces is potentially greater with higher indoor surface temperature asymmetry. The vertical indoor air temperature gradient and surface temperatures are important parameters for indoor thermal comfort.

Keywords
Reflective interior surfaces, Indoor air temperature gradient, Transient computational fluid dynamics, Surface-to-surface radiation, Building thermal performance
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-24243 (URN)10.1177/1420326X15609966 (DOI)000399487300007 ()2-s2.0-85018162879 (Scopus ID)
Available from: 2017-06-15 Created: 2017-06-15 Last updated: 2018-03-13Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2023-689x

Search in DiVA

Show all publications