Department of Mechanical engineering

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    Energy performance of phase change materials integrated into brick masonry walls for cooling load management in residential buildings
    (Elsevier, 2021-07) Rai, Aakash Chand
    Energy demand for space cooling in residential buildings is projected to witness rapid growth, primarily fueled by increasing household incomes in developing countries. To manage this ever-increasing cooling demand, integration of phase change materials (PCMs) in building walls is a potential solution that can reduce the buildings’ cooling energy consumption and peak cooling loads. However, to attain the proposed benefits from PCM integration, it is crucial to appropriately select PCM parameters such as its phase-change temperature and positioning in the wall. Thus, this investigation studied the energy performance of PCM integrated brick masonry walls for cooling load management in residential buildings under periodic steady-state conditions to identify the parameters that govern its performance and develop simple design guidelines. The research found that regardless of the amount of latent heat stored by the PCM, the daily heat gains and cooling loads were equal for wall configurations having equal thermal resistances under identical boundary conditions. Furthermore, even with the application of night ventilation, adding a PCM layer to a well-insulated wall did not reduce its cooling load; thus, PCM integration was ineffective in reducing the cooling load. However, the latent heat stored by the PCM reduced the fluctuations in the hourly heat gains and cooling loads; thus, PCM integration was found suitable for peak load management. For the PCM's proper utilization, its recommended position is on the inner side of the wall with sufficient insulation shielding it from outdoor conditions, and its melting temperature should be close to the indoor set-point temperature
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    Performance assessment of residential building envelopes enhanced with phase change materials
    (Elsevier, 2020-02) Rai, Aakash Chand
    Residential buildings in India account for ~22% of the national electricity consumption, of which one-third is used for space cooling; however, they are rarely constructed with energy-efficiency considerations. This presents an opportunity for reducing the energy consumption and associated greenhouse gas (GHG) emissions by design and construction of energy-efficient houses. Therefore, this investigation assessed the potential of PCM-enhanced building envelopes for reducing the cooling energy requirements of residential buildings in Delhi (capital of India). Through numerical simulations, we studied the impact of key PCM design parameters such as its thickness, position, melting point temperature and latent heat capacity on the proposed energy benefits, and compared them with those obtained with insulation-enhanced envelopes. We found that, applying a PCM layer on the roof reduced the summer heat gain by 12.6%–36.2%, whereas an insulation layer of the same thickness reduced heat gains by 41.0%–71.4% over the baseline construction. PCM-enhanced walls were also found to reduce the heat gain by 10.4%–26.6%, while insulated walls led to a heat gain reduction of 32.4%–64.0%. By extrapolating these results to city-scale, it appears that PCM/insulation-enhanced envelopes could reduce Delhi's annual electricity consumption and GHG emissions by 0.3%–1.5% and 0.2%–1.0%, respectively.