Characterization Of The Isosteric Heat Of Adsorption Refrigeration

The development of solar refrigeration technologies became the worldwide focalpoint for concern because the peaks of requirements in cold coincide most of the time withthe availability of the solar radiation. One of these emerging technologies is the solarpowered adsorption refrigeration technology which is proven to be suitable and applicablefor refrigeration as well as air conditioning applications. The refrigerants used in thesesystems are environmentally benign, natural refrigerants and are free from CFC. Therefore,these systems have zero ozone depleting as well as a zero global warming potentials.Reasonable prediction and correct determination for the working pairs‘coolingperformance still represents a challenge due to an ongoing intense development of novelsorbents and processes, in particular for sorption systems with relatively weaksorption-interaction forces. Adsorption affinity reflects mainly the relative interactionintensity between the adsorbate and the host frame work, the interaction will lead the freeadsorbate to adsorbed phase and release heat that is part of the isosteric heat of adsorption.In other words, we can use the isosteric heat of adsorption to characterize some adsorptionworking pair‘s affinity, the former is more attainable and practical criteria to evaluate theworking pair‘s potential performance. At the same time, we can have a rapid screening ofporosity and adsorption capacity among some alternative adsorbents based on infrareddetection of the isosteric heat of adsorption. For these reasons, when we design andsynthetize the optimal adsorbent with properties specifically tailored for particularcooling/heating applications, maybe we can first theoretically calculate the isosteric heatof adsorption of the ideal working pairs, second work out the isosteric heat of adsorptionof the alternative adsorbents interacting with same refrigerant under given workingcondition with molecular modeling, then screen out the optimum adsorbents whoseisosteric heat is closest to the ideal one, and at last, evaluate their practical adsorptioncapacity with a rapid high through-out experiment. Besides, if we can precisely predict theisosteric heat of adsorption at different load levels, we can carefully study the kinetics ofadsorption with different adsorbent cooling plans which will help us to selective a bestplan resulting shorter cycle time and higher SCP. So, it is meaningful to develop a simplebut not losing accuracy method to facility the adsorption refrigeration engineers to design adsorbers and the researchers to develop novel sorbents and processes.In this work, we first analysis the special adsorption process applied for refrigeration,describe the evaporation-adsorption equilibrium process using thermodynamic approachesbased on some reasonable assumptions according to the practical adsorption refrigerationsystems, then obtain a simple correction formula to predict the isosteric heat of adsorption,which only need the working conditions and some thermodynamic parameters ofrefrigerant. The comparison between the theory and empirical values shows an error with6%-18%.