Adsorption chiller using flat-tube adsorbers – Performance assessment and optimization

Rogala, Zbigniew

doi:10.1016/j.applthermaleng.2017.04.059

Cited by 49 publications

(16 citation statements)

References 25 publications

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“…In contrast to the LPM, the present model includes the effects of geometric features (fin height, fin spacing, tube diameter, and thickness) and considers the contact resistance between the sorbent material and metallic finned tube, which affirmatively enhances the accuracy of the analysis. There were a lot of studies on geometric optimization in adsorption beds [4,13,[25][26][27]. Also, recent coating technology has made it possible to reduce contact resistance and tremendously enhance performance (Rezk [28], Girnik and Aristov [29]).…”

Section: Effect Of Bed Modelmentioning

confidence: 99%

Effects of Evaporator and Condenser in the Analysis of Adsorption Chillers

et al. 2020

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In a survey of the literature from the last 20 years, 20% of the numerical models used to analyze the performance of adsorption chillers assumed the evaporator and condenser were ideal, with a fixed evaporation temperature and condenser temperature, and ignored interactions between the adsorption bed and evaporator/condenser. Even when the interaction with the evaporator and condenser was included, the other 80% of studies modeled the adsorption bed based on the LPM (lumped parameter method), which ignores the geometry effect and contact resistance of the bed, and thus reduces the accuracy of the analysis. As a consequence, these earlier numerical studies overestimated the system performance of the adsorption chiller. In this study, we conducted a refined numerical approach which avoids these limitations, producing estimates in close agreement with experimental results. Compared with our approach, the models with ideal treatment of evaporator and condenser overestimated COP (coefficient of performance) and SCP (specific cooling power) by as much as 16.12% and 24.64%, respectively. The models based on LPM overestimated COP and SCP by 22.82% and 11.28%, compared to our approach.

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Section: Effect Of Bed Modelmentioning

confidence: 99%

Effects of Evaporator and Condenser in the Analysis of Adsorption Chillers

et al. 2020

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“…In order to achieve good adsorption properties, highly porous materials are required, which, in turn, result in low thermal conductivity. According to [18], there are three possible ways to assemble the adsorbent-adsorber: Fill the adsorber with adsorbent grains [19][20][21], coat the adsorbers [21], or consolidate the composite adsorbents [9,22]. Adsorbent-adsorber assembly influences both the heat transfer from the adsorber surface to the grains, as well as the inter-and intraparticle mass transfer of the adsorbate vapor.…”

Section: Adsorbate-adsorber Assemblymentioning

confidence: 99%

“…According to [20], heat exchangers should be characterized by advantageous metal to adsorbent mass and of heat transfer surface to adsorbent mass ratio. The adsorber design has to increase heat transfer while also decreasing intra-and interparticle mass transfer resistance [20]. Moreover, the flow maldistribution should be minimized [23].…”

Section: Heat Exchangers: New Types Of Adsorption Bedsmentioning

confidence: 99%

“…Therefore, the selection of lightweight and compact adsorbers is of great importance in adsorption chiller design. The latest research in this area [20,21] shows the advantages of the finned flat-tube aluminum heat exchanger, which is typically used in automotives. This adsorber design ensures an increase of COP of up to 30% compared to that of traditional constructions.…”

Section: Heat Exchangers: New Types Of Adsorption Bedsmentioning

confidence: 99%

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Experimental Study of Performance Improvement of 3-Bed and 2-Evaporator Adsorption Chiller by Control Optimization

et al. 2019

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The main challenge facing adsorption cooling technology is low Coefficient of Performance (COP), which becomes a key factor of the commercialization of this technology. This paper presents the results of modifications, aiming to increase COP, applied to the control software of a prototype three-bed two-evaporator adsorption chiller. Changes were mainly related to the sequence of the switching valves and had no influence on the hardware of the chiller. The sequence changes enabled the introduction of heat recovery and mass regeneration. Moreover, the precooling process was improved. The applied modifications not only resulted in significant improvement of the chiller's COP, but also improved the cooperation adsorption unit heating source, which is of great importance in case of district heating supply. The improvement was also observed concerning such operational aspects as noise and vibrations. In the authors' opinion, the presented modifications can be introduced to most exploited adsorption chillers and could potentially lead to similar improvements in performance.Energies 2019, 12, 3943 2 of 17 Methods of Improving COP of Adsorption ChillerThe issue of COP improvement of adsorption chillers is the subject of much research, which focuses on two main fields of study: Improvements via hardware modification and via software modification. Hardware modifications mainly consist of the proper selection of working pairs, the optimization of the adsorption beds [8], and the general system design. Software modifications reported in the literature optimize the switching time and cycle allocation. Some of the optimization methods, like the application of heat or mass recovery, usually require both hardware and software modifications. Working PairsThe appropriate selection of the working pair was reported in [9,10] as a crucial factor influencing the COP of adsorption chillers. Therefore, much reported research is related to adsorption working pairs and their properties [10]. The most popular pairs are microporous silica gel and water, zeolite and water (including alumino-silicate zeolites) [11,12], and Y-type zeolite with methanol or ethanol combinations [9,13]. Moreover, some novel adsorption working pairs are investigated, that is (silico) aluminophosphate-water, consolidated adsorbents such as LiBr-silica-ethanol or water, CaCl 2 -silica and water, and activated carbon with ethanol, methanol or water [9].Each adsorption working pair has unique properties that make it possible to obtain good performance in the conditions considered. For example, water-based pairs cannot be applied to achieve temperatures lower than 0 • C (due to water's freezing point). Some of the adsorbates, like methanol, are harmful, and its application would probably require additional safety procedures. An overview of working pairs was presented by [14]. Other important factors which must be considered are the expense and availability of the selected adsorption working pair.

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“…However, according to Chorowski et al [2], some electric power is consumed by the cooling tower and pumping systems. The maximum reported SCP of the adsorption chillers (while driven by similar heating and cooling temperatures to the FDC) does not exceed 300 W/kg [11]. On the other hand, vapor-compression chillers are supplied only with the electric power, which is spent on running the compressor and the secondary systems (e.g., condenser fans).…”

Section: Introductionmentioning

confidence: 99%

The Influence of Operating Parameters on Adsorption/Desorption Characteristics and Performance of the Fluidised Desiccant Cooler

2018

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This paper concerns the issue of the proper selection of the operating parameters of the fluidised desiccant cooler. Despite the fact that fluidised desiccant cooling technology is being reported in the literature as an efficient way to provide cooling for the purposes of airconditioning , the improper control of its operation can lead to a significantly worse performance than expected. The objective of the presented theoretical study is to provide guidelines on the proper selection of such operating parameters of a fluidized desiccant cooler, such as superficial air velocity, desiccant particle diameter, bed switching time, and desiccant filling height. The influence of the chosen operating parameters on the performance of fluidised desiccant cooling technology is investigated based on their impact on electric and thermal coefficients of performance (COP) and specific cooling power (SCP). Moreover, the influence of the outlet air temperature, humidity, and desiccant water uptake on the adsorption/desorption characteristics was investigated, contributing to better understanding of sorption processes.

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Adsorption chiller using flat-tube adsorbers – Performance assessment and optimization

Cited by 49 publications

References 25 publications

Effects of Evaporator and Condenser in the Analysis of Adsorption Chillers

Effects of Evaporator and Condenser in the Analysis of Adsorption Chillers

Experimental Study of Performance Improvement of 3-Bed and 2-Evaporator Adsorption Chiller by Control Optimization

The Influence of Operating Parameters on Adsorption/Desorption Characteristics and Performance of the Fluidised Desiccant Cooler

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