Yazar "Paksoy, Halime" seçeneğine göre listele

Listeleniyor 1 - 6 / 6
  • Küçük Resim Yok
    Öğe
    2 years of monitoring results from passive solar energy storage in test cabins with phase change materials
    (Pergamon-Elsevier Science Ltd, 2020) Cellat, Kemal; Beyhan, Beyza; Konuklu, Yeliz; Dundar, Cengiz; Karahan, Okan; Gungor, Caner; Paksoy, Halime
    Buildings are one of the major consumers of global energy with a significant share reaching to 40%. Phase change materials (PCMs) are used in building materials and structures for energy saving in buildings. PCM absorbs heat from solar energy during daytime and releases that heat when temperatures cool down at night. The benefits of using PCMs in building materials are to reduce peak load and energy demand for heating and cooling and attain smaller temperature fluctuations. The aim of this study is to demonstrate passive utilization of solar energy storage in buildings with a new microencapsulated bio-based PCM (mPCM). The demonstration involves several development steps, which start in the laboratory for development of mPCM suitable for concrete and go to the building application with an innovative panel design under real climate conditions in the field. Monitoring of the test buildings with and without mPCM showed that developed microencapsulated PCM-concrete composite panels helped to maintain thermal comfort in buildings with a change in indoor air temperature with respect to reference building reaching 2 degrees C, which corresponds to up to 13% energy savings.
  • Küçük Resim Yok
    Öğe
    Encapsulation of Phase Change Materials
    (Elsevier, 2022) Paksoy, Halime; Şahan, Nurten; Konuklu, Yeliz
    Thermal energy storage (TES) has to be an integral part of future energy systems to achieve net zero emissions vision (NZEV) by 2050. Among the many roles TES can play in NZEV are providing uninterrupted use of renewable energy for heating and cooling, flexibility options for power generation and secure and long-life use of electronics that are becoming more and more important in the digitized world. TES can be done using sensible heat, latent heat and thermochemical concepts. Latent heat storage has the capability of charging and recharging at a high capacity and constant temperature, which makes it stand out among the other TES concepts. Phase change materials (PCM) are employed in latent heat storage to provide these features. Solid-liquid and solid-solid phase changes are preferred in PCM applications to avoid complexity of dealing with gas phase. © 2022 Elsevier Inc. All rights reserved
  • Küçük Resim Yok
    Öğe
    Latent Heat Storage Systems
    (Elsevier Inc., 2018) Konuklu, Yeliz; Şahan, Nurten; Paksoy, Halime
    Thermal energy storage is a key technology to address the challenges in the transition to a low carbon energy system. Latent heat storage (LHS) is one of these technologies that have special features of enabling isothermal and compact storage. Recently, there has been an increasing interest in LHS applications and phase change material development. This chapter gives an overview on fundamentals, applications, and recent trends on LHS materials. © 2018 Elsevier Inc. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Robust microencapsulated phase change materials in concrete mixes for sustainable buildings
    (WILEY-BLACKWELL, 2017) Beyhan, Beyza; Cellat, Kemal; Konuklu, Yeliz; Gungor, Caner; Karahan, Okan; Dundar, Cengiz; Paksoy, Halime
    For passive building applications, phase change materials (PCMs) are microencapsulated to avoid leakage of PCM from concrete structure. The primary challenge of using microencapsulated PCM (MPCM) is its weak shell structure. New MPCMs with different shell compositions to prevent breakage during mixing in fresh concrete are needed. In this study, free radical polymerization method to microencapsulate capric acid-myristic acid mixture as PCM with two different methyl methacrylate co-polymers is proposed to produce robust MPCMs for building applications. Two new microcapsules (MPCM-1 and MPCM-2) having latent heats of 91.9 and 97.3 J/g were synthesized. SEM analyses showed the size of microcapsules being in the range of 400-850 nm for MPCM-1 and 250-475 nm for MPCM-2. Analyses also reveal that the shells of MPCMs were not harmed, as they were added into concrete mixes. The microsphere's geometry was preserved, and distribution was homogeneous. The MPCMs were also studied under thermal tests of 1000 heating/cooling cycles. No significant changes in thermal properties were observed after thermal cycling tests. Copyright (C) 2016 John Wiley & Sons, Ltd.
  • Küçük Resim Yok
    Öğe
    Thermal buffering effect of a packaging design with microencapsulated phase change material
    (Wiley, 2019) Unal, Murat; Konuklu, Yeliz; Paksoy, Halime
    Temperature fluctuations during storage and transportation are the most important factors affecting quality and shelf life of food products. Phase change materials (PCM) with their isothermal characteristics are used to control temperature in various thermal operations. In this study, octanoic acid as PCM candidate was used in a packaging material design for thermal control of a food product. The PCM candidate was microencapsulated in different shell materials in our laboratory. Among the synthesized microcapsules, microencapsulated PCM (mPCM) (Delta Hm = 42.9 J/g) with styrene polymer as the shell material was selected based on its properties of being cost effective and compatibility with human health. Thermal buffering effect of PCM in bulk and microencapsulated forms was tested in a packaging design with special PCM pockets. Results showed that packages with mPCM and bulk PCM provided 8.8 and 6 hours of thermal buffering effect for 160 g of chocolate compared with the package without PCM (reference package).
  • Küçük Resim Yok
    Öğe
    Thermal enhancement of concrete by adding bio-based fatty acids as phase change materials
    (ELSEVIER SCIENCE SA, 2015) Cellat, Kemal; Beyhan, Beyza; Gungor, Caner; Konuklu, Yeliz; Karahan, Okan; Dundar, Cengiz; Paksoy, Halime
    An effective way to enhance the thermal storage capacity of buildings is to incorporate phase change materials (PCM) into building materials. Fatty acids are derivatives of materials readily found in nature and labeled as bio-based. In this study, we tested binary mixtures of capric acid (CA), myristic acid (MA), lauric acid (LA), and palmitic acid (PA) as candidate materials for building applications. The melting points of such fatty acid mixtures may further be adjusted, to agree with human comfort zone temperatures by regulating their compositions. We developed two binary mixtures of CA-LA and CA-MA as candidate PCMs for building applications. Thermal storage capacities were measured to be 109.0-155.4 J/g with a differential scanning calorimeter. Thermal cycle tests showed that both PCMs are thermally and chemically stable. Durabilities of PCM mixtures determined by the thermal gravimetric analysis indicated that degradation started at 120 degrees C. The compressive strengths of 1 wt.% PCM added to concrete mixtures were reduced by 12%, yet stayed within the desired limits for C35/45 concretes. However, when PCM contents were increased to 2 wt.%, compression strengths were reduced further, to be within the limits of C30/37 concretes. Both PCMs were suitable for self-compacting concrete mixtures used in buildings. (C) 2015 Elsevier B.V. All rights reserved.