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| 2. |
- Ameen, Arman, 1976-, et al.
(författare)
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Assessment of Thermal Comfort and Air Quality in Office Rooms of a Historic Building: A Case Study in Springtime in Continental Climate
- 2023
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Ingår i: Buildings. - : MDPI. - 2075-5309. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- One of the most important aspects of working in an office environment is ensuring that the space has optimal thermal comfort and an indoor environment. The aim of this research is to investigate the thermal comfort and indoor climate in three office rooms located at one of the campus buildings at the University of Gävle, Sweden. The evaluated period is in the month of April during springtime. During this period, parameters such as temperature, relative humidity, CO2, supply air flow rate, and room air velocities are measured on site. The results of the measurement show that the indoor temperature is on average lower in the rooms facing north, at 21–23.5 °C, compared to the rooms facing south, which reach high temperatures during sunny days, up to 26 °C. The results also show that the ventilation air supply rate is lower than the requirement for offices in two of the office rooms. The ACH rate is also low, at ≈ 1 h−1 for all the rooms, compared to the required levels of 2–4 h−1. The CO2 levels are within the recommended values; on average, the highest is in one of the south-facing rooms, with 768 ppm, and the maximum measured value is also in the same room, with 1273 ppm for a short period of time.
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| 3. |
- Björling, Mikael, 1960-, et al.
(författare)
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Infiltration of Air into two World Heritage Farmhouses in Sweden during Winter Conditions
- 2018
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Ingår i: Roomvent & Ventilation 2018. - Helsinki, Finland. - 9789525236484 ; , s. 1079-1084
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Konferensbidrag (refereegranskat)abstract
- As a part of an ongoing study, we report measurements of air infiltration during winter conditions into two Decorated Farmhouses of Hälsingland designated as UNESCO World Heritage Sites. In winter these two-storied farmhouses are rarely heated, except for special occasions. In this measurement one farmhouse was unheated, whereas one room was heated for a brief period in the other one. The observed local mean ages of air measured with tracer gas techniques generally increase with height, both locally within each room and between floors. The average temperature and humidity also increases from the first to the second floor. The indoor temperature follows the outdoor temperature with a time lag. The differences in water content between inside and outside air correlate with changes of the indoor relative humidity. The correlation is stronger for humidity increase than for humidity decrease, possibly due to moisture absorption by interior text.
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| 4. |
- Broström, Tor, et al.
(författare)
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Convective heating in a medieval church : Effects of air-to-air heat pumps on air movements, particle deposition and temperature distribution
- 2009
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Ingår i: Proceedings of the 11th International Conference on Air Distribution in Rooms (Roomvent) 2009, Busan, Korea.
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Konferensbidrag (refereegranskat)abstract
- In Europe many historic buildings use direct electric heating. Air-to-air heat pumps are an interesting alternative, in particular for conservation heating. However, the convective heating may accelerate soiling of walls and artefacts by increasing the velocity and turbulence. The objective of the present paper is to discuss the general problem, the methodology for studying air motions and temperature distribution, and to present the results from a case study where air-to-air heat pumps and bench heaters were used for heating in a medieval church. The temperatures, velocities and humidity in the church have been measured for four different heating modes. The present study does not indicate any major disadvantages of using heat pumps for background heating in stone churches of the studied kind. More detailed long term studies are needed to ascertain the effects over time.
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| 5. |
- Chen, L., et al.
(författare)
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Numerical investigations of wind and thermal environment in 2D scaled street canyons with various aspect ratios and solar wall heating
- 2021
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Ingår i: Building and Environment. - : Elsevier. - 0360-1323 .- 1873-684X. ; 190
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Tidskriftsartikel (refereegranskat)abstract
- Optimizing urban ventilation is an effective way to improve urban air quality and thermal environment. For this purpose, under the validation of wind-tunnel experiments, flow regimes and micro thermal environment in typical reduced-canyon models with aspect ratios (AR) of 1.1, 2.4, 4 and 5.67 were investigated by CFD simulations using periodic boundary condition. ANSYS Fluent 15.0 with a solar ray tracing model and radiation model was performed to numerically study turbulence characteristics with wind-driven force and solar-heating conditions. Results revealed that, with wind-driven condition, a clockwise vortex existed in normal and deep street canyon (AR = 1.1 and 2.4) while two counter-rotating vortices appeared in extremely deep canyon (AR = 4 and 5.67). Moreover, different turbulence structures and air temperature distribution existed in canyons with different solar-heating conditions. When the leeward wall or ground was heated, the pedestrian-level velocity increased and street ventilation was strengthened compared to wind-driven condition for all AR values. Particularly, the single main vortex was strengthened (AR = 1.1 and 2.4), and the two-vortex structure in extremely deep canyons (AR = 4 and 5.67) changed to single-vortex structure. When the windward wall was heated, the clockwise main vortex at AR = 1.1 and 2.4 was deformed, and a new sub vortex gradually appeared near street bottom. Furthermore, at AR = 4 and 5.67, windward solar heating destroyed the two-vortex structure and slightly improved pollutant dilution capacity. This work implied that extremely deep street design with weak pedestrian-level ventilation should be avoided. It also provides a meaningful reference for urban planning.
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| 6. |
- Cooper, Ed W, et al.
(författare)
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Measurement of the adventitious leakage of churches with a novel pulse technique
- 2011
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Ingår i: Proc. Roomvent 2011. - Trondheim, Norge : Tapir Akademisk Forlag. - 9788251928120
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Konferensbidrag (refereegranskat)abstract
- The University of Gavle is currently involved in a project on saving energy in historic buildings (churches). An important factor in the determination of the natural ventilation rate is the adventitious leakage of the envelope. Measurement of leakage is therefore a key feature of the investigations. It was decided to adopt a new technique developed at the University of Nottingham (UNott). It is a pulse technique compared to the conventional steady technique.The conventional technique consists of generating a steady and high pressure difference (50 Pa) across the envelope by means of a fan. Such pressures are rarely encountered in ventilation and this leads to errors in the low-pressure leakage. Furthermore the use of the conventional blower door technique in churches is difficult due to their large volume and the need to replace the doors.The underlying principle of the UNott technique is described and examples of results are given. The most important advantage of the Unott technique is that the leakage is determined at the low pressure differences that are encountered with ventilation e.g. 4 Pa. This is made possible primarily by the fact that the effects of wind and buoyancy at the time of the test are eliminated by taking account of the pressure variation before and after the pulse.For measurements in large buildings, a number of identical piston/cylinder units have to be operated simultaneously. The University of Gävle has developed a system whereby up to seven units can be used. Such a number is required for a leaky church and this is the first time this has been done.
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| 7. |
- Falk, Anders B., et al.
(författare)
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Influence of some weather parameters on the susceptibility of apple fruit to postharvest grey mould attack
- 2018
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Ingår i: Proceedings 2018. ; , s. 124-127
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Konferensbidrag (refereegranskat)abstract
- Several cultural and weather factors during the season influence the susceptibility of apple fruit to post-harvest pathogens. In the present study, the effect of different weather parameters on postharvest susceptibility of apples of the cv. ‘Ingrid Marie’ to grey mould was investigated. In 2015, apple fruit were collected from orchards in Southern Sweden, where local weather stations monitored different parameters. After harvest, the fruit were tested for susceptibility to grey mould by artificially inoculating them with%FLQHUHD. Lesion development was monitored over a 10-day-period. Analysis of results for a few orchards showed that cold weather for over a month preceding harvest and a low total number of growth degree days gave apples that were more susceptible to grey mould. This study was carried out in conventional orchards, but the conclusions can be important also for organic production, since they deal with the general effect of sunshine, temperature and rain, factors that may strengthen fruit during cultivation, regardless of production type. Future studies may focus on organic production to investigate whether these effects are general and also apply to organic production.
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| 8. |
- Garman, Ian, et al.
(författare)
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Demand control and constant flow ventilation compared in an exhaust ventilated bedroom in a cold-climate single-family house
- 2024
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Ingår i: Intelligent Buildings International. - : Elsevier. - 1750-8975 .- 1756-6932. ; 15:4, s. 175-188
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Tidskriftsartikel (refereegranskat)abstract
- A convertible, zoned ventilation system was field-tested in a modern, airtight Swedish home when occupied either by an experimental team or by a family. Indoor air quality in the master bedroom was monitored under four ventilation strategies. Relative to constant air volume strategies (CAV), demand-controlled ventilation (DCV) that was responding to CO2 concentration extracted more air when people were present, but less in total over 24 h. This elevated the indoor air humidity, beneficial in climates with dry winter air. Multiple monitors within the bedroom indicated that vertical CO2 stratification occurred routinely, presumably due to low mixing of supply air from a wall-mounted diffuse vent, spreading the air radially over the wall. This seemingly improved air quality in the breathing zone under local (ceiling) extract ventilation but worsened it during more typical, centralised extract ventilation, where air escapes the room via an inner doorway. The local extract arrangement thus seemed to yield both improved ventilation efficiency and reduced contaminant spread to other rooms. The noted air quality variations within the room highlight the importance of sensor placement in demand-control ventilated spaces, even in small rooms such as bedrooms.
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| 9. |
- Garman, Ian, et al.
(författare)
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Ventilation alone fails to prevent overheating in a Nordic home field study
- 2022
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Ingår i: 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022, Kuopio, 12 June 2022 through 16 June 2022. - : International Society of Indoor Air Quality and Climate.
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Konferensbidrag (refereegranskat)abstract
- A field study conducted in a modern Nordic single-family house with high airtightness and insulation levels, attempted to control summer indoor overheating using night-time cooling strategies. Exhaust air flow rates were manually scheduled by the researchers (based on weather forecasts), analogous to what an engaged occupant - or a predictive system - might do. Air temperatures at a nearby meteorological station peaked at 30 °C during 6 days in June that saw only 44 hours below 18 °C. Temperatures recorded indoors at the test house reached 32 °C, due also to very large solar gains, and never fell below 26 °C over 8 continuous days. It appears that under extended heat conditions that are exceptional now, but foreseen to become more frequent, some modern Nordic homes cannot be temperature controlled by ambient ventilation alone. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
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| 10. |
- Hayati, Abolfazl, 1985-, et al.
(författare)
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Evaluation of the LBL and AIM-2 air infiltration models on large single zones : three historical churches
- 2014
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Ingår i: Building and Environment. - : Elsevier BV. - 0360-1323 .- 1873-684X. ; 81, s. 365-379
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Tidskriftsartikel (refereegranskat)abstract
- Air infiltration in ancient churches and other historical and monumental buildings is of great importance considering moisture transfer, energy consumption, thermal comfort and air pollutants that induce surface soiling. Two of the most established models for predicting air infiltration rate in buildings are the Lawrence Berkeley Laboratory (LBL) model and the Alberta air Infiltration Model (AIM-2). Being originally developed mainly for dwellings, their applicability to large single zone buildings is evaluated in this study by comparing model predictions with field measurements in three historical stone churches that are naturally ventilated only through infiltration. The somewhat more developed AIM-2 model yielded slightly better predictions than the LBL model. However, an LBL version that allows inclusion of the Neutral Pressure Level (NPL) of the building envelope produced even better predictions and also proved less sensitive to assumptions on air leakage distribution at the building envelopes. All models yielded however significant overpredictions of the air infiltration rate. Since NPL may be difficult to attain in practice, the AIM-2 model was chosen for model modification to improve predictions. Tuning of this model by varying its original coefficients yielded however unrealistic model behaviors and the eventually suggested modification implied introducing a correction factor of 0.8. This reduced the median absolute prediction error from 25% to 11%. Thus, especially when the NPL is not at hand, this modification of the AIM-2 model may suit better for air infiltration assessment of churches and other buildings similar to the tested kind.
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