Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Determination of Characteristics of Adsorbent for Adsorption Heat Pumps(Izmir Institute of Technology, 2013) Sayılgan, Şefika Çağla; Ülkü, SemraAdsorption heat pumps, which are environmentally friendly and operating with thermal sources, have gained attention in recent years. Although they have higher primary energy efficiency than traditional heat pumps, adsorption heat pumps require improvements due to the low COP and SCP/SHP values. The selection of appropriate working pair, the determination of adsorption equilibrium and kinetics of the pair is quite important in the design of adsorption heat pumps. In this study, the working pairs used in adsorption heat pumps were discussed, and the models used in adsorption equilibria and kinetics were explained. In the experimental part, the effect of the adsorption and desorption temperatures on adsorption capacity and mass diffusivity were investigated. Type RD silica gel-water and zeolite 13X-water were selected as working pairs in the adsorption experiments. Accordingly, two volumetric systems were constructed; adsorption experiments were conducted and pressure changes were recorded against time. The experimental studies showed that the adsorption capacity was decreased with increasing adsorption temperature and with decreasing desorption temperature, and zeolite 13X-water pair had higher adsorption capacity than type silica gel-water pair under the same conditions. Type II and Type I isotherms were observed for type RD silica gel-water pair and zeolite 13X-water pair, respectively. The effective diffusivity of zeolite 13X-water pair was found in the range of 2x10-8-9x10-9 m2/s for the short time period and in the range of 7x10-10-10-8 m2/s for the long time period. In addition, it was seen that the effective diffusivity was effected from the initial adsorptive concentration and the effective diffusivity was decreased with increasing adsorbate concentration. This may be related to the effects of the heat transfer resistance, surface resistance or hydration and migration of the cations in the structure of the zeolite 13X.Master Thesis A Study on Isotherm Characteristics of Adsorbent-Adsorbate Pairs Used in Adsorption Heat Pumps(Izmir Institute of Technology, 2011) Yıldırım, Zeynep Elvan; Mobedi, Moghtada; Ülkü, SemraAdsorption heat pumps are promising systems due to their ability to recover heat at low temperature levels and to provide cooling and/or heating effects. It has advantages such as using renewable energy sources, being environmental friendly, having no vibration and lower operation costs. In this study, the most common pairs used in adsorption heat pumps were reviewed and their thermophysical and adsorption behaviors were discussed. The adsorption equilibrium phenomena were explained in details. The different experimental methods for determination of adsorption equilibrium for pairs were explained and compared. The change of heat of adsorption according to the varying adsorbed amount was studied numerically for two different equilibrium equations. It is found that, the heat of adsorption for pairs fitting Dubinin-Astakhov equation has a decrease with increasing adsorbed amount, while the heat of adsorption for pairs fitting Freundlich equation does not depend on adsorbed amount. A numerical study was performed to investigate the performances and cooling capacities of three different adsorption chillers for six different pairs. The results showed that when S40 silica gels - water pair is used, the chiller cooled with low temperature source gives the highest performances.In the experimental section of the present study, a volumetric setup was designed and constructed. Experiments were performed for a conventional pair of silica gel - water. It was observed that the maximum adsorption capacity of the experimented silica gel -water pair was 21% (kg water vapor /kg silica gel) at 35 °C, 19% (kg water vapor/kg silica gel) at 45 °C and 11% (kg water vapor /kg silica gel) at 60 °C.