Design of compact microscale geometries for ammonia–water desorption

Delahanty, Jared C.; Garimella, Srinivas; Garrabrant, Michael A.

doi:10.1080/23744731.2015.1015906

Cited by 20 publications

(2 citation statements)

References 17 publications

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“…However, concerns of long operation time and material fouling remain. Heating processes, though efficient, contend with energy consumption and water content, prompting innovations like vacuum heating [18], microchannel heaters [19], and heating under elevated pressure [20][21][22]. Tao et.…”

Section: Introductionmentioning

confidence: 99%

Microscopic insight into evaporation and condensation of binary system ammonia-water with the effect of hydrogen bond

Tan,

Kim,

Siwayanan

et al. 2024

Preprint

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Ammonia recovery for fertilizer and energy production faces a critical bottleneck: inaccurate prediction of evaporation and condensation rates in dilute solutions due to strong hydrogen bonds between ammonia and water. The presence of these bonds deviates the thermodynamics properties of ammonia water from standard laws like Henry's Law and Raoult's Law, hampering process optimization. As results, many of the ammonia water separation studies were conducted using specifically designed apparatus, and the results are bounded to said apparatus. This study introduces a novel method using Molecular Dynamics Simulations to tackle this challenge. We developed a simulation framework accounting for hydrogen bond interactions in low-concentration (20% wt%) ammonia-water mixtures. By systematically varying temperature under constant pressure, our approach tracks evaporation and condensation rates, revealing an efficient recovery strategy. At 140°C, ammonia evaporates at a rate of 609.22 kg·m-2·s-1 while condensate at 9.18 kg·m-2·s-1 under 20°C with, both at 0.4 MPa. Importantly, this strategy minimizes water loss, maximizing ammonia separation. These findings highlight the limitations of traditional models and demonstrate the power of molecular simulations in overcoming hydrogen bond challenges. Future work includes further validation against experimental data and exploring more complex mixtures for broader applicability. By unlocking accurate rate predictions, this work paves the way for optimizing ammonia recovery processes, boosting efficiency and sustainability in diverse fields. Mathematics Subject Classification 65Z05, 76T06, 76T10, 80-10.

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Section: Introductionmentioning

confidence: 99%

Microscopic insight into evaporation and condensation of binary system ammonia-water with the effect of hydrogen bond

Tan,

Kim,

Siwayanan

et al. 2024

Preprint

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show abstract

“…Therefore, the desorber (also known as a generator) is the most restrictive component for absorption systems driven by renewable energy sources [ 4 ]. Several desorber designs have been proposed to overcome the large volume problem and to improve the heat and mass transfer processes, which include dual components (desorber and condenser) [ 5 , 6 , 7 ], enhanced falling-film configurations [ 8 , 9 , 10 ], and microchannel configurations [ 11 , 12 , 13 ]. In addition to the design geometries, the performance of any desorber is affected by the condenser.…”

Section: Introductionmentioning

confidence: 99%

Experimental Performance of a Membrane Desorber Operating under Simulated Warm Weather Condensation Temperatures

et al. 2021

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In absorption systems using the aqueous lithium bromide mixture, the Coefficient of Performance is affected by the desorber. The main function of this component is to separate the refrigerant fluid from the working mixture. In conventional boiling desorbers, constant heat flux and vacuum pressure conditions are necessary to carry out the desorption process, and usually, the absorbers are heavy and bulky; thus, they are not suitable in compact systems. In this study, a membrane desorber was evaluated, operating at atmospheric pressure conditions with a water/lithium bromide solution with a concentration of 49.6% w/w. The effects of the solution temperature, solution mass flow, and condensation temperature on the desorption rate were analyzed. The maximum desorption rate value was 6.1 kg/m2h with the following operation conditions: the solution temperature at 95.2 °C, the solution mass flow at 4.00 × 10−2 kg/s, and the cooling water temperature at 30.1 °C. On the other hand, the minimum value was 1.1 kg/m2h with the solution temperature at 80.2 °C, the solution mass flow at 2.50 × 10−2 kg/s, and the cooling water temperature at 45.1 °C. The thermal energy efficiency, defined as the ratio between the thermal energy used to evaporate the refrigerant fluid with respect to the total thermal energy entering the membrane desorber, varied from 0.08 to 0.30. According to the results, a high solution mass flow, a high solution temperature, and a low condensation temperature lead to an increase in the desorption rate; however, a low solution mass flow enhanced the thermal energy efficiency. The proposed membrane desorber could replace a conventional boiling desorber, especially in absorption cooling systems that operate at high condensation temperatures as in warm weather regions.

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Development and demonstration of a compact ammonia–water absorption heat pump prototype with microscale features for space-conditioning applications

Garimella

Keinath

Delahanty

et al. 2016

Applied Thermal Engineering

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Design of compact microscale geometries for ammonia–water desorption

Cited by 20 publications

References 17 publications

Microscopic insight into evaporation and condensation of binary system ammonia-water with the effect of hydrogen bond

Microscopic insight into evaporation and condensation of binary system ammonia-water with the effect of hydrogen bond

Experimental Performance of a Membrane Desorber Operating under Simulated Warm Weather Condensation Temperatures

Development and demonstration of a compact ammonia–water absorption heat pump prototype with microscale features for space-conditioning applications

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