| 1. |
- Abdul Hamid, Akram, et al.
(författare)
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Determining the impact of air-side cleaning for heat exchangers in ventilation systems
- 2020
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Ingår i: Building Services Engineering Research & Technology. - : SAGE Publications. - 0143-6244 .- 1477-0849. ; 41:1, s. 46-59
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Tidskriftsartikel (refereegranskat)abstract
- Cleaning coils can be an efficient way to reduce the need for reparations and maintain the functionality of a ventilation system. This study builds upon existing knowledge concerning the contamination of heat exchangers. Through field measurements on coils and heat-recovery units, a laboratory experiment on a coil, and a generic calculation example, this study determines the impact of sustained contamination on heat-recovery units with regards to energy use. Field measurements made before and after cleaning of heat exchangers show an average increase in the pressure drop by 12% and decrease in the thermal exchange efficiency by 8.1% due to mass deposited on the surface of the heat exchangers. Results from a laboratory test show a correlation between the mass deposited on a coil and (1) the increase in pressure drop over the coil, as well as (2) a diminishing heat exchange. Accumulating contamination on heat-recovery units in residential and commercial buildings (over time) is then linked to increasing pressure drop and diminishing thermal efficiency. With models based on these links, energy loss over time is calculated based on a generic calculation example in a realistic scenario. Practical application : The results from this study emphasize the need for maintenance of buildings with ventilation systems with coils, but more so those with heat-recovery units. The presented field measurements and laboratory study correlate energy loss with sustained accumulation of contaminants on coils and heat-recovery units. These results should serve as a recommendation to property owners considering maintenance of such units in their buildings.
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| 2. |
- Brembilla, Christian, 1983-, et al.
(författare)
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The impact of control strategies on space heating system efficiency in low-energy buildings
- 2019
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Ingår i: Building Services Engineering Research & Technology. - London : Sage Publications. - 0143-6244 .- 1477-0849. ; 40:6, s. 714-731
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Tidskriftsartikel (refereegranskat)abstract
- In this study efficiency factors measures the thermal energy performance for space heating. This study deals with the influence of control strategies on the effriciency factors of space heating and its distribution system. An adaptive control is developed and applied to two types of heating curves (linear and non-linear) for a low-energy building equipped with renewable energy sources. The building is modelled with a hybrid approach (law driven + data driven model). The design of the floor heating is calibrated and validated by assessing the uncertainty bands for low temperatures and mass flow rate. advantages and disavantages of linear and non-linear heating curves are highlighted to illustrate their impact on space heating thermodynamic behaviour and on the efficiency factors of the space heating system.Practical application: The study reveals that applying commercial building energy simulation software is worthwhile to determine reliable performance predictions. Oversimplified building models, in particular when considering building thermal mass, are not capable of simulating the thermodynamic response of a building subjected to different control strategies. The application of different heating cuirves (linear and non-linear) to massless building models leaves the amount of mass flow rate delivered to the space heating unchanged when the building is subjected to sharp variations of the outdoor temperature.
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| 3. |
- Brinkworth, BJ, et al.
(författare)
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A validated procedure for determining the buoyancy-induced flow in ducts
- 2005
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Ingår i: Building Services Engineering Research & Technology. - : SAGE Publications. - 0143-6244 .- 1477-0849. ; 26:1, s. 35-48
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Tidskriftsartikel (refereegranskat)abstract
- A procedure is set out for calculating the buoyant flow induced in a duct with heat input at the wall, as in the cooling ducts used behind photovoltaic arrays. In these, buoyancy is opposed by various pressure losses, due to obstructions at the inlet and outlet, fluid friction at the walls and structural support members passing transversely through the duct. New methods are developed for calculating these losses, and each is validated separately by tests in a purpose-built isothermal rig. Measurements are also reported for some further losses, not yet amenable to calculation, due to nets and hoods at the duct ends, as might be used to exclude rain and wildlife. Finally, the whole procedure is validated by measurement of a duct with one heated wall. Practical application: Verified by measurements at every stage of its development, the method reported gives greater confidence in the routine calculation of the flow induced in ductwork where there is heat gain, as in systems for PV cooling and natural ventilation. The new treatments given for the hydrodynamic losses at basic components apply wherever these are used in the field of HEVAC.
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| 4. |
- Karlsson, Fredrik, et al.
(författare)
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Measured and predicted energy demand of a low energy building : Important aspects when using building energy simulation
- 2007
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Ingår i: Building Services Engineering Research & Technology. - : SAGE Publications. - 0143-6244 .- 1477-0849. ; 28:3, s. 223-235
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Tidskriftsartikel (refereegranskat)abstract
- Three different simulation tools were used to simulate a low energy terraced house in the south of Sweden. The software tools all use dynamic models to calculate, for example, the energy demand for heating and the indoor temperatures. The aim of this paper is to discuss the relative importance to the annual energy demand of different energy aspects of a Swedish low-energy house. Both measured and simulated values are considered and compared. The focus is on the impact of choice of software, the habits of the tenants, and the relative impact of different design parameters such as ventilation rates. The measured values for total electricity demand range from about 6000 kWh to over 12000kWh, the average demand being 8020kWh. The annual predicted total energy demand using three different simulation software tools deviated by about 2%. The energy use deviation due to airflow control was about 10%, and the deviation due to differences in heat exchanger efficiency was about 20% and the deviation in annual energy use due to differences in internal gains due to differences in tenant habits, assumed in the models, was 7%. Furthermore, when comparing the predicted energy use during the design process of the low-energy building with actual measurements after the tenants have moved in, these differ about 50% in average for this specific case. Practical application: Building energy simulation software is often used to make predictions of how different construction materials, design principles and operation influence the energy balance and indoor thermal comfort. It is therefore important that the output of these software tools is trustworthy and accurate. This paper discusses the importance of accurate input data during the design process in order to achieve a valid prediction of energy use with emphasis on tenants' behaviour. It was shown that the deviations in a parametric study were larger than the deviations in the comparison between the results from the three simulation tools. This indicates a need for more accurate models for modelling tenant behaviour and habits rather than more accurate building component models.
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| 5. |
- Teli, Despoina, 1980, et al.
(författare)
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Fuel poverty-induced ‘prebound effect’ in achieving the anticipated carbon savings from social housing retrofit
- 2016
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Ingår i: Building Services Engineering Research and Technology. - : SAGE Publications. - 0143-6244 .- 1477-0849. ; 37:2, s. 176-193
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Tidskriftsartikel (refereegranskat)abstract
- Social housing retrofit is often seen as a way to contribute to carbon reductions as it typically encompasses large-scale interventions managed by one landlord. This work investigates the carbon savings potential of a deep retrofit in a local authority owned 107-flat tower block, taking into account the tenants' pre-retrofit heating strategies. Prior to the retrofit, temperature and relative humidity monitoring were undertaken in 18 flats for 35 days. The measurements were then used to develop occupant heating profiles in the 18 homes. Dynamic thermal simulation of the flats pre- and post-retrofit using the identified user heating profiles highlights that for these fuel poverty-constrained flats, the estimated carbon savings of retrofit will be typically half those predicted using standard rules for temperatures in living spaces.Practical application: The findings presented in this paper demonstrate the impact of fuel poverty on the expected benefits from social housing retrofit schemes, providing information relevant to multiple stakeholders: (1) building industry: The study highlights the need to use empirical data in building energy modelling, as typical conditions could be far from representative in social homes (2) Policy makers and social landlords: Targets for CO2 reduction may not be achieved through retrofitting, but the social impact could be much greater and more critical than assumed. The findings under this work help to direct incentives for retrofit schemes towards the social and health benefits achieved.
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