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    A comparison of heating and cooling systems having radiant and ventilation systems regarding thermal comfort
    (Springer, 2024) Rahmanparast, Amir; Bacak, Aykut; Camci, Muhammet; Karakoyun, Yakup; Acikgoz, Ozgen; Dalkilic, Ahmet Selim
    Thermal comfort is crucial for indoor environmental quality, impacting occupant well-being and intellectual productivity. Despite the widespread use of HVAC technologies in residential and commercial buildings, there is growing awareness of thermal comfort, leading to more studies on this issue. According to international publication indexes nearly 60% of publications belongs to the categories of construction building technology, energy fuels, and civil engineering. It should also be noted that 40% of world energy consumption pertains to construction sector. In this context, radiant cooling and heating systems come forward with their low exergy destruction rates pointing out the potential to be energy-efficient due to their higher and lower operation temperatures. Displacement ventilation, with its low heating and cooling capacity, has not gained widespread preference. However, the increasing consciousness of global warming and energy efficiency, along with the fear of airborne virus contamination, views stand-alone or hybrid applications of radiant heating/cooling and displacement ventilation as potential future solutions. This review study investigates the impact of radiant heating/cooling and ventilation types, mixing, and displacement on thermal comfort performance, focusing on factors affecting thermal comfort in trending radiant cooling and heating applications like radiant walls, ceilings, and floors. The study emphasizes the importance of considering occupant preferences, building characteristics, and energy efficiency when choosing the most suitable heating and cooling systems for different indoor environments. Stand-alone and hybrid applications of radiant heating/cooling and displacement systems can enhance thermal comfort performance, with the exception of specific cases requiring a high thermal load or ventilation rate.
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    Case studies on local mixed convection heat transfer coefficients along a radiant heated wall subjected to displacement ventilation
    (Springer, 2023) Camci, Muhammet; Karakoyun, Yakup; Acikgoz, Ozgen; Dalkilic, Ahmet Selim
    As the demand for energy-efficient air conditioning systems enabling thermal comfort criteria increases, the research into innovative systems that combine displacement ventilation and radiant heating is being more up-to-date. This work discusses local mixed convection heat transfer coefficients over a radiant heated wall in an experimental room coupled with displacement ventilation provided by a floor level nozzle. In the experimental chamber, the air enters the room either from the floor level of the analyzed heated wall as in scenario 1 or the opposite wall in scenario 2 in the upward direction. The intervals of air inlet temperature and velocity are set between 13-27 & DEG;C and 0-2.5 ms(-1), respectively. The obtained data have been analyzed from a physical point of view, and four correlations having R-sq. numbers of 0.93, 0.94, 0.94, and 0.98 have been developed for the local mixed convective heat transfer coefficients along a heated wall. The alterations of local convection heat transfer coefficients along an examined radiant heated wall affected by a slot diffuser delivering a lowest air inlet velocity of 0.5 ms(-1) and highest air inlet velocity of 2.5 ms(-1) are gained in the intervals of 2-5.8 Wm(-2) K-1 and 2.5-10 W m(-2) K-1, in turn.
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    Öğe
    Experimental investigation of mixed and forced convection generated by displacement ventilation with radiant wall heating
    (Pergamon-Elsevier Science Ltd, 2022) Camci, Muhammet; Karakoyun, Yakup; Acikgoz, Ozgen; Dalkilic, Ahmet Selim
    There is a rising necessity concerning low energy consumption and thermal comfort, thus, new systems combining displacement ventilation and radiant heating are becoming common as a research topic. The current paper covers free, mixed, and forced convection in an experimental chamber consisting of a radiant wall heating system and a baseboard level diffuser. Air temperature in the test room is adjusted using an air blower via a novel designed baseboard level slot diffuser along with a hydronic wall heating circuit. Simultaneously; an upward direction air jet is blown through the heated or the opposite wall under two scenarios. The ranges of air inlet velocity and temperature are selected to be between 0.25 and 12.5 m/s and 14-26 degrees C, correspondingly. The heat transfer characteristics pertaining to the heated wall are studied with respect to the influences of wall and air temperatures, air inlet velocities, and the location of the diffuser. To derive convective heat transfer coefficient correlations valid for mixed and forced types for a radiant heated wall, acquired data have been processed. The convective, radiative, and total heat transfer coefficient intervals of 3-14.1, 5.2-5.5, and 9.3-21.7 W/m2K have been obtained for the radiant heated wall coupled with airflows, correspondingly.