| 1. |
- Wigö, Hans, 1959-
(författare)
-
Effects of intermittent air velocity on thermal and draught perception : A field study in a school environment
- 2013
-
Ingår i: The International Journal of Ventilation. - 1473-3315 .- 2044-4044. ; 12:3, s. 249-255
-
Tidskriftsartikel (refereegranskat)abstract
- Air movement in an indoor space may be experienced in very different ways. For persons feeling cool, air movement tends to be perceived as draught, whilst when feeling warm air movement may provide a desired cooling effect. In the transition zone it therefore seems difficult to use constant air velocity as a tool for cooling without creating draught problems. One possible way to use air movement as a method to improve thermal comfort, without resultant draught problems, could be to use intermittent air velocity instead of constant velocity. This new cooling method was implemented in a high school in Sweden and evaluated during spring (April) and autumn (September). The present paper reports results from two field experiments where subjects were exposed to velocity variations. The analysis shows significant effects of velocity condition on thermal comfort and air quality. In summary, people exposed to velocity variation perceived the air as cooler and fresher compared with those exposed to constant low velocity and very few classified the air movement as draught. A further conclusion is that even the pupils who were exposed to velocity variation wanted slightly more air movement.
|
|
| 2. |
- Kabanshi, Alan, et al.
(författare)
-
The influence of heat, air jet cooling and noise on performance in classrooms
- 2015
-
Ingår i: The International Journal of Ventilation. - : Informa UK Limited. - 1473-3315 .- 2044-4044. ; 14:3, s. 321-332
-
Tidskriftsartikel (refereegranskat)abstract
- The quality of indoor environments influences satisfaction, health, and work performance of the occupants. Additional understanding of the theoretical and practical value of individual indoor parameters in relation to health and performance aids indoor climate designers to obtain desired outcomes. This also results in expenditure savings and increased revenue: health care and improved productivity. Here, we report two experiments that investigated how heat, cooling strategy and background noise influence performance in a full-scale classroom mockup setting. The results show that heat and background noise are detrimental to logic-based tasks and to writing, whilst cooling manipulations can protect performance. Implications for indoor environment design are discussed.
|
|
| 3. |
- Abdul Hamid, Akram, et al.
(författare)
-
The impact of a DCV-system on the IAQ, energy use, and moisture safety in apartments - a case study
- 2022
-
Ingår i: International Journal of Ventilation. - : Informa UK Limited. - 1473-3315 .- 2044-4044. ; 21:1, s. 35-52
-
Tidskriftsartikel (refereegranskat)abstract
- A novel DCV-system controls the air-change rate for each apartment in multifamily buildings based on two indoor air parameters: 1) the moisture load (supply), and 2) volatile organic compounds. With a central fan, but decentralized control boxes placed outside each apartment, the system controls the air-change rate for each apartment. This paper’s main aim is to determine the potential of this DCV-system, through a case study, to: 1) achieve good IAQ, 2) handle the moisture loads appropriately, and 3) achieve good energy efficiency in multifamily buildings. Furthermore, the paper aims to assess the possibility to achieve good IAQ by validating the DCV-system’s VOC-controls through measurements of CO2 in apartments. Field measurements show that the system responds appropriately to apartment-specific loads, and that acceptable emission and moisture loads are achieved in most apartments in the case study. The impact that the system has on the energy use was assessed through calculations based on the field measurements. The calculations show that the DCV-system saves energy used for heating the supply-air by 86% in comparison to a mechanically balanced ventilation system without heat recovery, and 22% in comparison to the same system but with heat recovery.
|
|
| 4. |
- Andersson, Harald, 1987-, et al.
(författare)
-
An Investigation Concerning Optimal Design of Confluent Jets Ventilation with Variable Air Volume
- 2024
-
Ingår i: The International Journal of Ventilation. - : Taylor & Francis. - 1473-3315 .- 2044-4044. ; 23:3, s. 183-203
-
Tidskriftsartikel (refereegranskat)abstract
- This parametric study aims to predict the performance of confluent jets ventilation (CJV) with variable air volume (VAV) from four CJV design parameters. A combination of computational fluid dynamics (CFD), and response surface method (RSM) has been used to predict the energy efficiency, thermal comfort and IAQ for the four expected vital design variables, i.e., heat load (XH), number of nozzles (XN), airflow rate (XQ) and supply temperature (XTS). The RSM was used to generate a quad-ratic equation for the response variables exhaust temperature (TE), sup-ply temperature (TP), PMV, DR, eT and ACE. The RSM shows that the TE, TP and PMV were independent of the number of nozzles. The proposed equations were used to generate setpoints optimized for thermal com-fort (PMV) for summer, spring and winter cases with different CLO fac-tors and different TS under a scenario where the heat load varied between 10-30W/m2. TE was used as setpoint to regulate the airflow rate to keep the PMV values close to zero. The results show that by adapting the TS to the CLO factor both thermal comfort and the energy efficiency can be improved. Further energy reduction can be gained by downregulating the airflow rate to keep the TP at a fixed setpoint when the heat load is decreased. This means that a CJV can effectively be combined with VAV to improve environmental performance with good thermal comfort (-0.5
|
|
| 5. |
- Blomqvist, Claes, et al.
(författare)
-
Air Movements through Horizontal Openings in Buildings – A Model Study
- 2004
-
Ingår i: The International Journal of Ventilation. - : Informa UK Limited. - 1473-3315 .- 2044-4044. ; 3:1, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- A building contains a number of large openings like doors and staircases. When the temperature of the spaces connected by these openings differs, the difference in density will cause air movements through them. Horizontal air movements through vertical openings in buildings like doors and windows are well investigated while studies of air movements through horizontal openings like stairwells are less frequent and therefore this work is focusing on this case. The paper reports on an experimental study of the possibility of using buoyancy forces to distribute air and heat through horizontal openings. The experiments have been carried out in a scale model with water as the operating fluid. The result of the study shows that the flow rate through a horizontal opening is roughly half of the flow rate through a vertical opening for the same conditions, probably caused by the more complex flow pattern in the horizontal opening. A staircase below the horizontal opening will guide the flow somewhat and will cause a small increase of the fluid exchange through the opening.
|
|
| 6. |
- Cehlin, Mathias, et al.
(författare)
-
Computed tomography for indoor application
- 2006
-
Ingår i: The International Journal of Ventilation. - 1473-3315 .- 2044-4044. ; 4:4, s. 349-364
-
Tidskriftsartikel (refereegranskat)abstract
- This paper deals with tomographic techniques for two-dimensional spatially resolved concentration measurements indoors. This represents a significant advance over the traditional point measuring method for mapping tracer gas and pollutants. Methods for recording of data are stressed as well as different types of tomographic reconstruction algorithms such as the Smooth Basis Function Minimization (SBFM) and the modified Low Third Derivative (LTDm) methods. Among the reconstruction algorithms available today, SBFM and LTDm are among the most promising. These algorithms show potential for reconstruction of gas concentration in rooms, since they are regularized to converge towards smooth concentration distributions. Using the LTD method and ‘snapshot’ configuration enables the examination and real-time monitoring of transient flows.
|
|
| 7. |
- Cehlin, Mathias, et al.
(författare)
-
Computed Tomography for Indoor Applications
- 2006
-
Ingår i: The International Journal of Ventilation. - 1473-3315 .- 2044-4044. ; 4:4, s. 349-364
-
Tidskriftsartikel (refereegranskat)
|
|
| 8. |
- Cehlin, Mathias, 1974-
(författare)
-
Mapping tracer gas concentrations using a modified Low Third Derivative method : numerical study
- 2019
-
Ingår i: The International Journal of Ventilation. - : Taylor & Francis. - 1473-3315 .- 2044-4044. ; 18:2, s. 136-151
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 9. |
- Claesson, Leif, et al.
(författare)
-
Unsteady Flow Reversal in Natural Ventilation Stack : Model Scale Tests
- 2005
-
Ingår i: The International Journal of Ventilation. - 1473-3315 .- 2044-4044. ; 4:1, s. 25-36
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of the unsteady flow in a ventilation stack of a school have been made at model scale in an environmental wind tunnel. The results confirm the expectation that the stack is well-sited, in that it was difficult to induce flow reversal except over a narrow range of wind directions and the amount of reversal was small (reversal percentage < 5 %). The results also show that the technique is capable of reliably detecting such small reversal percentages.
|
|
| 10. |
- Einberg, Gery, et al.
(författare)
-
Characteristics of Particles and their Behaviour in Ventilation Air
- 2003
-
Ingår i: The International Journal of Ventilation. - 1473-3315 .- 2044-4044. ; 2:1, s. 45-54
-
Tidskriftsartikel (refereegranskat)abstract
- The behaviour of particles in air flow is important for identifying those in various locations in ventilated space. The main reason for this study is to propose a new modelling concept to determine a realistic distribution of particles of different sizes in a space. The goal for this investigation is to divide particles into groups according to their behaviour in air and to improve the existing settling model. The growth of particle aerodynamic diameter in higher relative humidity is also presented. Here, growth of diameter and coagulation is used to determine the control volume concentration. The finite volume method is used to describe the particle concentration in the computational domain. A background to particle properties and theory for calculations are given for this purpose. Results from the literature survey reveal that modelling needs a more systematic approach to cover all sizes of particles with clear classification by behaviour.
|
|
