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Cehlin, Mathias, DoktorORCID iD iconorcid.org/0000-0003-2023-689x
Publications (10 of 43) 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)000457639900006 ()2-s2.0-85057839765 (Scopus ID)
Funder
Vinnova, 2013-03772
Available from: 2018-11-22 Created: 2018-11-22 Last updated: 2019-08-09Bibliographically approved
Khosravi Bakhtiari, H., Akander, J. & Cehlin, M. (2019). Evaluation of Thermal Comfort in a Historic Building Refurbished to an Office Building with Modernized HVAC Systems. Advances in Building Energy Research
Open this publication in new window or tab >>Evaluation of Thermal Comfort in a Historic Building Refurbished to an Office Building with Modernized HVAC Systems
2019 (English)In: Advances in Building Energy Research, ISSN 1751-2549, E-ISSN 1756-2201Article in journal (Refereed) Epub ahead of print
Abstract [en]

Envelopes with low thermal performance are common characteristics in European historic buildings, causing higher energy demand and insufficient thermal comfort. This paper presents the results of a study on indoor environmental quality (IEQ), with special focus on thermal comfort, in the historic City Hall of Gävle, Sweden, now used as an office building. There are two modern heat recovery ventilation systems with displacement ventilation supply devices. The district heating network heats the building via pre-heat supply air and radiators. Summer cooling comes from electric heat pump ejecting heat into the exhaust ventilation air. A building management system (BMS) controls the heating, ventilation and air-conditioning (HVAC) equipment. The methodology included on-site measurements, BMS data logging and evaluating the occupants’ perception of a summer and a winter period indoor environment using a standardized questionnaire. In conclusion, indoor environmental quality in this historic building is unsatisfactory. Stuffy air, too high, too low and varying room temperatures, lighting problems and noise are constant issues. Although it is equipped with modern ventilation systems, there are still possibilities for improving thermal comfort by improved control strategies, since upgrading the building’s envelope is not allowed according to the Swedish Building Regulations in historic buildings with heritage value.

Keywords
Thermal comfort, historic building, HVAC
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-29442 (URN)10.1080/17512549.2019.1604428 (DOI)2-s2.0-85064678798 (Scopus ID)
Funder
Knowledge Foundation, 20150133
Available from: 2019-04-05 Created: 2019-04-05 Last updated: 2019-08-16Bibliographically approved
Ameen, A., Choonya, G. & Cehlin, M. (2019). Experimental Evaluation of the Ventilation Effectiveness of Corner Stratum Ventilation in an Office Environment. Buildings, 9(7), Article ID 169.
Open this publication in new window or tab >>Experimental Evaluation of the Ventilation Effectiveness of Corner Stratum Ventilation in an Office Environment
2019 (English)In: Buildings, ISSN 2075-5309, E-ISSN 2075-5309, Vol. 9, no 7, article id 169Article in journal (Refereed) Published
Abstract [en]

An experimental study was conducted in a room resembling an office in a laboratory environment. The study involved investigating the ability of corner-placed stratum ventilation in order to evaluate the ventilation’s effectiveness and local thermal comfort. At fixed positions, the air temperature, air velocity, turbulence intensity, and tracer gas decay measurements were carried out. The results show that corner-placed stratum ventilation behaves very similar to a mixing ventilation system when considering air change effectiveness. The performance of the system was better at lower supply air flow rates for heat removal effectiveness. For the heating cases, the draught rates were all very low, with the maximum measured value of 12%. However, for the cooling cases, the maximum draught rate was 20% and occurred at ankle level in the middle of the room.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
air change effectiveness; air exchange efficiency; ventilation effectiveness; draught rate; temperature effectiveness
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-30433 (URN)10.3390/buildings9070169 (DOI)000478645000003 ()2-s2.0-85070072942 (Scopus ID)
Available from: 2019-07-15 Created: 2019-07-15 Last updated: 2019-08-23Bibliographically approved
Ameen, A., Cehlin, M., Larsson, U. & Karimipanah, T. (2019). Experimental Investigation of Ventilation Performance of Different Air Distribution Systems in an Office Environment: Heating Mode. Energies, 12(10), Article ID 1835.
Open this publication in new window or tab >>Experimental Investigation of Ventilation Performance of Different Air Distribution Systems in an Office Environment: Heating Mode
2019 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 10, article id 1835Article in journal (Refereed) Published
Abstract [en]

A vital requirement for all-air ventilation systems are their functionality to operate both in cooling and heating mode. This article experimentally investigates two newly designed air distribution systems, corner impinging jet (CIJV) and hybrid displacement ventilation (HDV) in comparison against a mixing type air distribution system. These three different systems are examined and compared to one another to evaluate their performance based on local thermal comfort and ventilation effectiveness when operating in heating mode. The evaluated test room is an office environment with two workstations. One of the office walls, which has three windows, faces a cold climate chamber. The results show that CIJV and HDV perform similar to a mixing ventilation in terms of ventilation effectiveness close to the workstations. As for local thermal comfort evaluation, the results show a small advantage for CIJV in the occupied zone. Comparing C2-CIJV to C2-CMV the average draught rate (DR) in the occupied zone is 0.3% for C2-CIJV and 5.3% for C2-CMV with the highest difference reaching as high as 10% at the height of 1.7 m. The results indicate that these systems can perform as well as mixing ventilation when used in offices that require moderate heating. The results also show that downdraught from the windows greatly impacts on the overall airflow and temperature pattern in the room.

Keywords
Corner impinging jet, mixing ventilation, displacement ventilation, tracer gas, air exchange effectiveness, air change effectiveness, draught rate
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-29582 (URN)10.3390/en12101835 (DOI)000471016700014 ()2-s2.0-85066877057 (Scopus ID)
Note

Funding agency:

- University of Gävle

Available from: 2019-05-21 Created: 2019-05-21 Last updated: 2019-08-23Bibliographically approved
Ameen, A., Cehlin, M., Larsson, U. & Karimipanah, T. (2019). Experimental investigation of ventilation performance of different air distribution systems in an office environment – cooling mode. Energies, 12(7), Article ID 1354.
Open this publication in new window or tab >>Experimental investigation of ventilation performance of different air distribution systems in an office environment – cooling mode
2019 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 7, article id 1354Article in journal (Refereed) Published
Abstract [en]

The performance of a newly designed corner impinging jet air distribution method with an equilateral triangle cross section was evaluated experimentally and compared to that of two more traditional methods (mixing and displacement ventilation). At nine evenly chosen positions with four standard vertical points, air velocity, turbulence intensity, temperature, and tracer gas decay measurements were conducted for all systems. The results show that the new method behaves as a displacement ventilation system, with high air change effectiveness and stratified flow pattern and temperature field. Both local air change effectiveness and air exchange effectiveness of the corner impinging jet showed high quality and promising results, which is a good indicator of ventilation effectiveness. The results also indicate that there is a possibility to slightly lower the airflow rates for the new air distribution system, while still meeting the requirements for thermal comfort and indoor air quality, thereby reducing fan energy usage. The draught rate was also lower for corner impinging jet compared to the other tested air distribution methods. The findings of this research show that the corner impinging jet method can be used for office ventilation.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
Corner impinging jet, mixing ventilation, displacement ventilation, tracer gas, air exchange effectiveness, air change effectiveness, draught rate
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-29443 (URN)10.3390/en12071354 (DOI)000465561400171 ()2-s2.0-85065464428 (Scopus ID)
Available from: 2019-04-05 Created: 2019-04-05 Last updated: 2019-08-16Bibliographically approved
Cehlin, M. (2019). Mapping tracer gas concentrations using a modified Low Third Derivative method: numerical study. The International Journal of Ventilation, 18(2), 136-151
Open this publication in new window or tab >>Mapping tracer gas concentrations using a modified Low Third Derivative method: numerical study
2019 (English)In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 18, no 2, p. 136-151Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Taylor & Francis, 2019
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)000469880200004 ()2-s2.0-85045619672 (Scopus ID)
Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2019-08-22Bibliographically approved
Ameen, A. & Cehlin, M. (2019). Reducing energy usage in multi-family housing. In: 2019 9th International Conference on Future Environment and Energy 9–11 January 2019, Osaka, Japan: . Paper presented at 2019 9th International Conference on Future Environment and Energy, 9–11 January 2019, Osaka, Japan. Institute of Physics Publishing (IOPP), 257, Article ID 012030.
Open this publication in new window or tab >>Reducing energy usage in multi-family housing
2019 (English)In: 2019 9th International Conference on Future Environment and Energy 9–11 January 2019, Osaka, Japan, Institute of Physics Publishing (IOPP), 2019, Vol. 257, article id 012030Conference paper, Published paper (Refereed)
Abstract [en]

The energy usage in residential sector have been around 22% of the total energy use in the world and increasing due to the population growth and higher living standards. The energy sources for this are made up primarily of non-renewable energy resources which generates a large amount of global greenhouse gases. A lot of countries have implemented various regulations and rules to reduce the energy usage in buildings and promoting the use of renewable energy technologies. This paper presents a parametric study of a typical multi-family building in its pre-design stage. The climate location used is Sweden (Gothenburg) and Japan (Osaka). The aim of the study is to compare various configurations and to examine how they affect the energy use. The most interesting configurations are the use of heat pump and solar cells. Other configurations that are examined are infiltration levels, pressure coefficients, wind impact, ventilation with heat recovery, ventilation scheduling, building orientation and finally changing U-values in the building material. Results of this study show that the energy saving, by utilizing a heat pump and solar panels, can reduce the total energy use by 34.9% for Gothenburg and 32% for Osaka. The results also show that the difference in total energy use between the two cities reduce substantially (3% difference) when utilizing a heat pump in combination with solar panels.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Series
IOP Conference Series: Earth and Environmental Science, ISSN 1755-1307, E-ISSN 1755-1315 ; 257
Keywords
Building energy simulation, BES, IDA ICE, multi-family, energy renovation, EEM
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-29391 (URN)10.1088/1755-1315/257/1/012030 (DOI)
Conference
2019 9th International Conference on Future Environment and Energy, 9–11 January 2019, Osaka, Japan
Available from: 2019-03-18 Created: 2019-03-18 Last updated: 2019-08-12Bibliographically 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
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
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