Abstract
In solar-thermal adsorption/desorption processes, it is not always possible to preserve equal operating times for the adsorption/desorption modes due to the fluctuating supply nature of the source which largely affects the system’s operating conditions. This paper seeks to examine the impact of adopting unequal adsorption/desorption times on the entire cooling performance of solar adsorption systems. A cooling system with silica gel–water as adsorbent-adsorbate pair has been built and tested under the climatic condition of Iraq. A mathematical model has been established to predict the system performance, and the results are successfully validated via the experimental findings. The results show that, the system can be operational at the unequal adsorption/desorption times. The performance of the system with equal time is almost twice that of the unequal one. The roles of adsorption velocity, adsorption capacity, overall heat transfer coefficient, and the performance of the cooling system are also evaluated.
Highlights
Air conditioning (AC) is one of the primary human activities that contributes to heavy power consumption, during the summer months
According to data provided by International Energy Agency (IEA, Paris, France), the global power consumed by air-conditioners and electric fans in building sector is around 20% of the total power consumption [1]
The performance of the intermittent cooling system with different adsorption/desorption operating times was investigated in terms of adsorption velocity, adsorption capacity, overall heat transfer coefficient, coefficient of performance (COP), and specific cooling power (SCP)
Summary
Air conditioning (AC) is one of the primary human activities that contributes to heavy power consumption, during the summer months. The cooling efficiency of adsorptive systems depends on the evaporation rate, which in turn, largely depends on the thermophysical properties of the adsorbent-adsorbate working pairs and the effective design of the porous adsorbent bed to provide the necessary heat and mass transfer augmentation These influencing factors have been a subject of interest for numerous studies, and several cooling, refrigeration, and desalination applications have been explored using different working pairs with different bed designs [9,10,11]. Varying heating/cooling water temperatures or their mass flow rates, as a result of equipment obsolescence and weather changes, are commonly arising in the real cooling process Based on these characteristics, this paper presents a dynamic model for an adsorption cooling system driven by solar evacuated tubes collectors under unequal states conditions. The roles of adsorption velocity, adsorption capacity, overall heat transfer coefficient, and the performance of the cooling system are elucidated
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