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  • 1.
    Joudi, Ali
    Dalarna University, School of Technology and Business Studies, Energy Technology. Linköpings universitet.
    Radiation properties of coil-coated steel in building envelope surfaces and the influence on building thermal performance2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Recent studies have shown that the optical properties of building exterior surfaces are important in terms of energy use and thermal comfort. While the majority of the studies are related to exterior surfaces, the radiation properties of interior surfaces are less thoroughly investigated. Development in the coil-coating industries has now made it possible to allocate different optical properties for both exterior and interior surfaces of steel-clad buildings. The aim of this thesis is to investigate the influence of surface radiation properties with the focus on the thermal emittance of the interior surfaces, the modeling approaches and their consequences in the context of the building energy performance and indoor thermal environment.

    The study consists of both numerical and experimental investigations. The experimental investigations include parallel field measurements on three similar test cabins with different interior and exterior surface radiation properties in Borlänge, Sweden, and two ice rink arenas with normal and low emissive ceiling in Luleå, Sweden. The numerical methods include comparative simulations by the use of dynamic heat flux models, Building Energy Simulation (BES), Computational Fluid Dynamics (CFD) and a coupled model for BES and CFD. Several parametric studies and thermal performance analyses were carried out in combination with the different numerical methods.

    The parallel field measurements on the test cabins include the air, surface and radiation temperatures and energy use during passive and active (heating and cooling) measurements. Both measurement and comparative simulation results indicate an improvement in the indoor thermal environment when the interior surfaces have low emittance. In the ice rink arenas, surface and radiation temperature measurements indicate a considerable reduction in the ceiling-to-ice radiation by the use of low emittance surfaces, in agreement with a ceiling-toice radiation model using schematic dynamic heat flux calculations.

    The measurements in the test cabins indicate that the use of low emittance surfaces can increase the vertical indoor air temperature gradients depending on the time of day and outdoor conditions. This is in agreement with the transient CFD simulations having the boundary condition assigned on the exterior surfaces. The sensitivity analyses have been performed under different outdoor conditions and surface thermal radiation properties. The spatially resolved simulations indicate an increase in the air and surface temperature gradients by the use of low emittance coatings. This can allow for lower air temperature at the occupied zone during the summer.

    The combined effect of interior and exterior reflective coatings in terms of energy use has been investigated by the use of building energy simulation for different climates and internal heat loads. The results indicate possible energy savings by the smart choice of optical properties on interior and exterior surfaces of the building.

    Overall, it is concluded that the interior reflective coatings can contribute to building energy savings and improvement of the indoor thermal environment. This can be numerically investigated by the choice of appropriate models with respect to the level of detail and computational load. This thesis includes comparative simulations at different levels of detail.

  • 2.
    Joudi, Ali
    et al.
    Dalarna University, School of Technology and Business Studies, Energy Technology. SSAB Europe, Borlänge.
    Cehlin, Mathias
    Högskolan i Gävle.
    Svedung, Harald
    Dalarna University, School of Technology and Business Studies, Energy Technology. SSAB Europe, Borlänge.
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Energy Technology.
    Moshfegh, Bahram
    Högskolan i Gävle.
    Numerical and experimental investigation of the influence of infrared reflective interior surfaces on building temperature distributions2017In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 26, no 3, p. 355-367Article in journal (Refereed)
    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–" 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.

  • 3.
    Joudi, Ali
    et al.
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Svedung, Harald
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Wäckelgård, Ewa
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Energy Efficient Buildings with Functional Steel Cladding2011In: World Renewable Energy Congress, Linköping, Sweden, 2011Conference paper (Refereed)
    Abstract [en]

    The aim of the study is to develop a model for the energy balance of buildings that includes the effect from the radiation properties of interior and exterior surfaces of the building envelope. As a first step we have used ice arenas as case study objects to investigate the importance of interior low emissivity surfaces. Measurements have been done in two ice arenas in the north part of Sweden, one with lower and one with higher ceiling emissivity. The results show that the low emissivity ceiling gives a much lower radiation temperature interacting with the ice under similar conditions. The dynamic modelling of the roof in ice arenas shows a similar dependence of the roof-to-ice heat flux and the ceiling emissivity. A second part of the study focus on how to realise paints with very low thermal emissivity to be used on interior building surfaces.

  • 4.
    Joudi, Ali
    et al.
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Svedung, Harald
    Building Surface Radiation Properties and Heat Flux: poster2010In: ENERGY FORUM on Solar Building Skins, Bressanone, Italien, 2010Conference paper (Other academic)
  • 5.
    Joudi, Ali
    et al.
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Svedung, Harald
    Energy savings in buildings through optimized surface heat radiation properties2009In: Ökosan'09 - The International Symposium on High-Quality Thermal Retrofit of Large-Volume Buildings, Weiz, Austria, 2009Conference paper (Other academic)
  • 6.
    Joudi, Ali
    et al.
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Svedung, Harald
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Bales, Chris
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Highly reflective coatings for interior and exterior steel cladding and the energy efficiency of buildings2011In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 88, no 12, p. 4655-4666Article in journal (Refereed)
    Abstract [en]

    The effect of surface heat-radiation properties of coil-coated steel cladding material on the energy efficiency of buildings in Nordic climate is addressed by parallel temperature and energy usage measurements in a series of test cabins with different exterior solar reflectivity and interior thermal reflectivity. During one year, a number of one- or two-week experiments with air conditioner cooling and electrical floor heating were made while logging air-, radiation- and surface temperatures, energy consumption and weather conditions. Measurements show significant energy savings in the test cabins by the use of high thermal reflectivity interior surfaces both during heating and cooling and a strongly reduced cooling demand by the use of high solar reflectivity exterior surfaces. Results are interpreted within the context of a steady-state energy flux model, to illuminate the importance of surface resistance properties (radiation and convective heat dissipation).

  • 7.
    Joudi, Ali
    et al.
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Svedung, Harald
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology. SSAB EMEA.
    Cehlin, Mathias
    Building, Energy and Environmental Engineering, University of Gävle.
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Reflective coatings for interior and exterior of buildings and improving thermal performance2013In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 103, p. 562-570Article in journal (Refereed)
    Abstract [en]

    The importance of reducing building energy usage and thriving for more energy efficient architectures, has nurtured creative solutions and smart choices of materials in the last few decades. Among those are optimizing surface optical properties for both interior and exterior claddings of the building. Development in the coil-coating steel industries has now made it possible to allocate correct optical properties for steel clad buildings with improved thermal performance. Although the importance of the exterior coating and solar gain are thoroughly studied in many literatures, the effect of interior cladding are less tackled, especially when considering a combination of both interior and exterior reflective coatings. This paper contemplates the thermal behavior of small cabins with reflective coatings on both interior and exterior cladding, under different conditions and climates with the aim to clarify and point out to the potential energy saving by smart choices of clad coatings.

  • 8.
    Joudi, Ali
    et al.
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Svedung, Harald
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Rönnelid, Mats
    Dalarna University, School of Technology and Business Studies, Energy and Environmental Technology.
    Energy efficient surfaces on building sandwich panels: a dynamic simulation model2011In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 43, no 12, p. 3736-3736Article in journal (Refereed)
    Abstract [en]

    The choice of building envelope is critical for the energy performance of buildings. The major part of the energy used by a building during its lifetime is used for maintaining a suitable interior thermal climate under varying exterior conditions. Although exterior heat radiation properties (i.e. total solar reflectivity and long wave thermal emissivity) have been well accepted to have a large impact on the need for active cooling in warmer climate, the effect of a reduced thermal emissivity on interior surfaces on the building thermal energy flux is rarely studied. This paper addresses the sensitivity of the thermal energy flux through a sandwich panel, by systematically varying the surface thermal emissivity (both interior and exterior) and total solar reflectance of exterior surface, for three geographical locations: southern, middle and northern Europe. A model is introduced for calculating the effect of both interior and exterior optical properties of a horizontal roof panel in terms of net energy flux per unit area. The results indicate potential energy saving by the smart choice of optical properties of interior and exterior surfaces.

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