A Review of Reactant Salts for Resorption Refrigeration Systems

Bao, Huashan; Wang, R. Z.

doi:10.1142/s2010132510000150

Cited by 11 publications

(6 citation statements)

References 21 publications

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“…There is a great number of MHAs that can react with ammonia in a wide temperature range (50~350 • C) [30]. In a complete cycle, they undertake endothermic desorption with ammonia release in one-half cycle and experience exothermic adsorption in the other half cycle when returning to the initial state.…”

Section: Methodsmentioning

confidence: 99%

Solid–Gas Sorption System for Ammonia Storage and Delivery Driven by Engine Waste Heat for NOx Reduction of Diesel Engine

et al. 2022

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A new design of a sorption-selective catalytic reduction (SCR) system is proposed to improve ammonia storage density and meet the ammonia demand for high NOx conversion efficiency at a relatively lower temperature (<100 °C) compared to urea-SCR systems. The major components are a main unit and a start-up unit that each contain a metal halide ammine as the sorbent. The start-up unit can operate without any external heat source, but spontaneously releases ammonia at the ambient temperature and is only used when the main unit is being warmed up for action. The selection criteria for the metal halide ammine for each unit is discussed. The working pair of SrCl2 as the main ammine and NH4Cl as the start-up ammine is further analyzed as an example to be used in the sorption-SCR system for a diesel engine, the NOx emissions of which were experimentally measured in different operation modes. Based on the experimental data of engine emissions and kinetic models of the chemisorption between ammines and ammonia, the dynamic performance of the sorption system with a total capacity of 180 L sorbent composite in different layouts was investigated and compared. It was found that the achievable desorption conversion degree was lower in smaller reactors and was more sensitive to operating conditions in smaller reactors compared to larger reactors. This suggests that a system using a small reactor layout requires some extra volume to completely meet the required capacity compared to a larger reactor layout. However, because systems with large reactors tend to respond slowly, as they have more thermal mass and take a longer time for preparation, there is a design trade-off required to have optimal performance and balance between the main unit and the start-up unit. In the case studied in this work, a system using three rechargeable reactors with a volume of 60 L each was found to be the preferable layout; it could have about a 90% desorption conversion degree and required around 10 min of warm-up time. Meanwhile, the coupled start-up unit should have a capacity of around 165 mL at least.

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Section: Methodsmentioning

confidence: 99%

Solid–Gas Sorption System for Ammonia Storage and Delivery Driven by Engine Waste Heat for NOx Reduction of Diesel Engine

et al. 2022

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“…Despite environmental issues that are widely advocated such as global warming and ozone depletion for which this refrigerant is highly responsible, most of the refrigerant and air-conditioning industries are still using mechanical compressor-based refrigerant technology due to its high COP and high refrigerant effect today. Fortunately, scientist had focused on global warming and its effects in Kyoto Protocol 1997 [4]. Since that, more and more research are concentrated on the development of a more sustainable and environmentally friendly adsorption refrigeration technology.…”

Section: Introductionmentioning

confidence: 99%

Evaporator Performance for Water Refrigerant Adsorption Cooling System

Khanafiah¹,

Sahafudin²,

Jerai³

2022

JMechE

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Adsorption Cooling System gives an alternative to the commercial vapor compression refrigeration cycles due to their benefits of having a very environmentally friendly and promising energy-saving system. An adsorption cooling system consists of four main components which are thecondenser, evaporator, expansion valve, and adsorption bed for the system to effectively function. One of the factors that affect the efficiency of the system is the performance of the evaporator itself as the system operates at sub-atmospheric pressure and the performance is mediocre when using conventional evaporators. Due to the low-pressure condition, hydrostatic pressure may affect the saturated temperature of the water refrigerant in a flooded type evaporator. Therefore, in this study, the performance of the evaporator was investigated based on the water height variation. The highest heat transfer coefficient and evaporation heat transfer rate are achieved when the water is set at the heat exchanger tube diameter level. Furthermore, 0.1 kg of silica gel adsorbent is used to obtain the maximum of 250 W/kg of Specific Cooling Power when the heat transfer fluid is set to 20 ºC.

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“…When considered alongside the uptake values of ammonia (NH 3 ) per gram of salt, Table 1, the salts ammonium chloride (NH 4 Cl), sodium bromide (NaBr) and barium chloride (BaCl 2 ) are the most frequently reviewed for LTS applicability. Bao and Wang [2], provide a useful summary table of previous resorption working pair studies. However, not detailed clearly in previous works is the dynamic characterisation of the ammonia-ammonium chloride reaction across the working pressure range for a resorption heat pump application.…”

Section: Introduction 1research Justificationmentioning

confidence: 99%

Ammonium Chloride (NH4Cl)—Ammonia (NH3): Sorption Characteristics for Heat Pump Applications

et al. 2021

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In a resorption heat pump, the adsorption and desorption reaction of ammonium chloride (NH4Cl) with ammonia (NH3) is of interest as a Low Temperature Salt (LTS). Reviewing previously published NH4ClNH3 equilibrium lines, ammonium chloride appears to offer useable working temperatures (50–70 °C) in the 10–15 bar pressure range during the adsorption reaction, and provides beneficial working conditions for the desorption reaction, when compared with alternative LTS candidates at atmospheric pressure. The NH4ClNH3 adsorption and desorption reactions, using a NH4Cl composite salt, have been evaluated under dynamic ‘realworld’ conditions in a Large Temperature Jump (LTJ) experimental testing rig; although there are concerns with mass transfer characteristics, the salt exhibits no hysteresis between the adsorption and desorption reactions, contrary to previous literature. The experimentally obtained equilibrium line values for the reaction enthalpy and entropy are 29,835 J/mol and 207 J/(mol∙K), respectively. Using a semi-empirical model, the NH4Cl composite salt has been successfully characterised, enabling the prediction of salt reaction behaviour. The model constants, A and n, identified are 4.5 and 5 for adsorption and 5 and 4 for desorption, with an overall salt active fraction (applicable to both reactions) of 0.98. Overall, the working equilibrium line and the dynamic performance of ammonium chloride has been investigated and the applicability of NH4Cl as a LTS for a resorption heat pump determined.

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A Review of Reactant Salts for Resorption Refrigeration Systems

Cited by 11 publications

References 21 publications

Solid–Gas Sorption System for Ammonia Storage and Delivery Driven by Engine Waste Heat for NOx Reduction of Diesel Engine

Solid–Gas Sorption System for Ammonia Storage and Delivery Driven by Engine Waste Heat for NOx Reduction of Diesel Engine

Evaporator Performance for Water Refrigerant Adsorption Cooling System

Ammonium Chloride (NH4Cl)—Ammonia (NH3): Sorption Characteristics for Heat Pump Applications

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