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Title: Thermodynamic and heat transfer analysis of an activated carbon-R723 adsorption system
Author: Khaliji Oskouei, Mohammadhasan
ISNI:       0000 0004 6495 7960
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2016
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The main challenge of adsorption systems today is to improve the performance of the thermal generator in order to make adsorption systems economically viable. The key novelty of this doctoral thesis is its evaluation of the potential use of a new refrigerant, R723, in an adsorption system using activated carbon as adsorbent. Granular activated carbon is a well-known and effective adsorbent in adsorption systems. The R723 refrigerant was introduced into the market in early 2004; this new refrigerant is an azeotropic mixture of 40% ammonia and 60% dimethyl ether by mass. The new refrigerant is compatible with copper alloy (Cu-Ni 90/10), in comparison with ammonia, which is only compatible with stainless steel. The high thermal conductivity of Cu-Ni 90/10 causes an improvement in heat exchange in the thermal generator. This work investigates the effect of granular activated carbon packed bed density on gas permeability. A correlation was found between granular activated carbon packing density and refrigerant pressure drop over the thermal generator. The porosity of granular activated carbon in terms of adsorbing the R723 was determined. The porosity was evaluated using the gas mixture adsorption theory and using the porosity experimental data for granular activated carbon / ammonia and granular activated carbon / dimethyl ether pairs. The performance of the adsorption system for different applications was determined with the activated carbon / R723 pair. The effects of concentration of R723 and granular activated carbon packing density on the thermal parameters of activated carbon packing, including the thermal conductivity and heat transfer coefficients of the contact wall/packed carbon, were studied simultaneously. A correlation was established showing the connection between the thermal parameters of the packed bed, and the concentration of R723 and the density of the granular activated carbon packed bed. Finally, this thesis demonstrates modelling procedures for a tubular generator with the granular activated carbon (208-C) / R723 pair, with regard to different applications such as air conditioning, ice making and a heat pump. The model under consideration included the ideal desorption effect without heat and mass recovery, while imposing the ideal temperature jump into the boundary of the tubular generator. During the modelling, information such as driving temperature (Tg), coefficient of performance (COP), and specific cooling and heating powers (SCP & SHP), was collected. The collected information was used to established a correlation in order to estimate the optimum driving temperature, COP, SHP and SCP, based on different governing parameters, such as granular activated carbon packing density, outside diameter (OD) and the length of the thermal generator. This information is useful in choosing the correct typical standard tube size of the thermal generator with the granular activated carbon (208-C) / R723 pair for specific applications, based on optimum governing parameters, such as the range of heat source availability and the power requirement. The other key point which was examined was the effect of tubular generator body material on COP and SCP (SHP) for different applications. The model used stainless steel and Cu-Ni 90/10 with standard wall thickness.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TK Electrical engineering. Electronics Nuclear engineering