Adsorption Refrigeration Technologies

This chapter introduces a comprehensive overview about the principles, challenges and applications of adsorption refrigeration systems (ARSs), as a promising sustainable solution for many of cooling and heating applications. In addition to the features and the basics of ARSs, the following topics have been covered such as characteristics of working pairs, trends in improving the heat and mass transfer of the adsorber; advanced adsorption cycles and performance and operational data of some adsorption refrigeration applications. In some details, the operating range and the performance of ARSs are greatly affected by the employed working adsorbent/refrigerant pairs. Therefore, the study, development and optimum selection of adsorbent/refrigerant pairs, particularly the composite adsorbents, can lead to improving the performance and reliability of ARSs. Regarding the enhancement of heat and mass transfer in the adsorbent bed, two methods are commonly used: one is the development of adsorbents through different coating technologies or new materials such as metal-organic frameworks, and the second is the optimization of the adsorber geometrical parameters and cycle modes. Finally, a brief on some adsorption chillers applications have started to find their share in markets and driven by solar or waste heats

Numerical Investigation of Copper Foam Adsorption Beds Packed with MOF-801 for Space Cooling and Desalination Applications

In this paper, an emerging Metal Organic Framework adsorbent MOF-801 packed into a recently developed copper foamed adsorbent-bed is numerically investigated under different operating conditions and physical parameters and benchmarked against the widely used silica gel adsorbent. A numerical model using lumped dynamic modelling approach was developed and validated against experimental data. An enhancement in the effective thermal conductivity for MOF-801 and silica gel foam packed bed and hence an improvement for the overall performance. The MOF-801-based system showed a higher performance for desalination application with a maximum production of specific daily water production of 13 m3/ton·day compared to 9 m3/ton·day for the silica gel-based system. MOF-801-based system evidenced its competition in the cooling application, achieving enhancement for the specific cooling power 140% higher than silica gel-based system

Multi-objective optimisation of MOF-801 adsorbent packed into copper foamed bed for cooling and water desalination systems

Recently, there have been several endeavours to enhance the performance of the adsorption systems for cooling cum desalination by developing new materials and adsorbent bed designs. Therefore, this article contributes to the field by computationally studying the utilisation of state-of-the-art MOF-801 adsorbent packed into the emerging copper-foamed adsorbent bed heat exchanger and benchmarking its performance against that utilising silica gel baseline adsorbent. A multi-objective global optimisation aimed simultaneously at the best coefficient of performance, specific cooling power, and clean water productivity was undertaken. The optimisation was built on the insights from a broad parametric study for the geometric and operating conditions. Given the novelty of the adsorbent MOF-801 and bed design combination, a one-dimensional model was developed to imitate the heat transfer in the adsorbent bed and coupled with a previously validated empirical lumped analytical model for the adsorption system using the MATLAB platform. Using copper foam significantly enhanced the effective thermal performance of the adsorbent bed, improving the overall system performance under different operating conditions. Furthermore, the clean water productivity of the MOF-801-based system outperformed that of the SG-based system by 38%, as the former yielded 29.7 m3/(ton.day), while the latter 21.5 m3/(ton.day). Besides, the MOF-801-based system showed specific cooling power of 830.8 W/kg compared to 611.5 W/kg for the silica gel-based system. However, the cooling capacity per unit volume determined the systems’ form factor, and the coefficient of performance was respectively higher by 9.6% and 20.2% for the silica gel-based system than those of the MOF-801-based system, stemming from the low packing density of MOF-801

Productivity and Thermal Performance Enhancements of Hollow Fiber Water Gap Membrane Distillation Modules Using Helical Fiber Configuration: 3D Computational Fluid Dynamics Modeling

Although hollow fiber water gap membrane distillation (HF-WGMD) units offer certain advantages over other MD desalination systems, they still require enhancements in terms of distillate flux and productivity. Therefore, this work proposes a novel configuration by incorporating the helical turns of HF membranes within the water gap channel of the HF-WGMD modules. A fully coupled 3D CFD model is developed and validated to simulate the multifaceted energy conservations and diffusion mechanisms that are inherent to the transport phenomena in the proposed HF-WGMD module. Single and double helical HF membrane designs with different numbers of turns are compared to the reference modules of single and double straight HF membrane designs under various operational conditions. At a feed temperature of 70 °C, a noteworthy 11.4% enhancement in the distillate flux is observed when employing 20 helical turns, compared to the single straight HF membrane module. Furthermore, the specific productivity revealed a maximum enhancement of 46.2% when using 50 helical turns. The thermal performance of the proposed HF-WGMD module shows higher energy savings of up to 35% in specific thermal energy consumption for a one-stage module. Using three stages of single helical modules can increase the gain output ratio from 0.17 for the single stage to 0.37, which represents an increase of 117.6%. These findings indicate the high potential of the proposed approach in advancing the performance of HF-WGMD systems

Investigation of the Mechanical and Tribological Behavior of Epoxy-Based Hybrid Composite

The main target of this study is to evaluate the impact of hybrid reinforcement using Al2O3 nanoparticles and graphite on the epoxy nanocomposites’ mechanical and tribological properties. Various weight fractions of the reinforcement materials, ranging from 0 to 0.5 wt.%, were incorporated into the epoxy. The aim is to enhance the characteristics and durability of the polymers for potential utilization in different mechanical applications. The addition of hybrid additives consisting of Al2O3 nanoparticles and graphite to the epoxy resin had a noticeable effect on the performance of the epoxy nanocomposites. The incorporation of these additives resulted in increased elasticity, strength, toughness, ductility, and hardness as the concentration of reinforcement increased. The enhancement in the stiffness, mechanical strength, toughness and ductility reached 33.9%, 25.97%, 25.3% and 16.7%, respectively. Furthermore, the frictional tests demonstrated a notable decrease in both the coefficient of friction and wear with the rise of the additives’ weight fraction. This improvement in the structural integrity of the epoxy nanocomposites led to enhanced mechanical properties and wear resistance. The SEM was utilized to assess the surfaces of tested samples and provide insights into the wear mechanism

Performance Assessment of an Ice-Production Hybrid Solar CPV/T System Combining Both Adsorption and Vapor-Compression Refrigeration Systems

The technology of a hybrid solar concentration photovoltaic/thermal (CPV/T) system is an efficient way of converting solar energy to heat and electrical power, in which overall energy-extraction efficiency is at its highest. In this study, numerical dynamic simulation models were developed for a hybrid solar CPV/T system and an adsorption refrigeration system (ARS). Under the climatic conditions of Riyadh all year round, the electrical and thermal powers generated by the CPV/T system were used to estimate the ice production of both the vapor compression refrigeration system (VCS) and the ARS. The CPV/T system can provide a thermal energy of 37.6 kWh and electrical energy of 24.7 kWh a day on average over the year using a 12.5 m2 facing area of Fresnel lenses. The ARS employed an advanced approach which used Maxsorb III adsorbent packed in two aluminum foam beds. An optimum cycle time of the ARS was adapted for each month to match the variation in the thermal energy, while a variable-speed compressor was chosen for the VCS. Due to its higher coefficient of performance (COP), the proposed solar hybrid system can produce 494.4 kg of ice per day while sharing 84.5% of the VCS. The average solar COP over the year of the hybrid system can attain 0.875, which represents a promising value for a solar ice-production system

Performance investigation of adsorption cooling and desalination systems employing thermally enhanced copper foamed bed coated with SAPO-34 and CPO-27(Ni)

Despite the increasing interest in adsorption cooling and desalination systems, the poor heat hence mass transfer in the adsorbent-bed (the core component) impedes the efficient energy conversion at the system level and increases its physical footprint. In response, this paper numerically investigates the overall enhancement of adsorption cooling cum desalination system employing emerging copper foamed adsorbent beds of advanced thermal performance coated with advanced adsorbent materials to address such an untapped challenge. Silico-aluminophosphate (SAPO-34) and Nickel-based metal-organic framework CPO-27(Ni) adsorbents were employed. First, a 2-D axisymmetric computational fluid dynamic fully coupled model was developed to simulate the adsorbent-beds considering non-ideal condenser and evaporator pressures. Second, the influence of different operating conditions and copper foam thicknesses was investigated at the adsorbent- bed and system levels. The advanced adsorption kinetics of SAPO-34 enabled shortening the cycle time from 600 to 180 s, which enhanced the coefficient of performance (COP), specific cooling power (SCP), and specific daily water production (SDWP) of the system by 163%, 223%, and 228%. The regeneration temperature was the most influential parameter on the systems’ performance within the investigated range (70-100 °C). It enhanced the COP from 0.2 to 0.421, SCP from 132 to 821 W.kg-1, and SDWP from 4.7 to 29.3 m3.ton-1.day- 1, for CPO-27(Ni) coated bed; and COP from 0.378 to 0.388 and SCP from 393 to 855 W.kg-1 and SDWP from 14 to 31 m3.ton-1.day-1 , for SAPO-34 coated bed. The reported enhancements at the adsorption system- level signpost metal-foamed adsorbent-bed coating the most thermally efficient adsorbent-bed design

Experimental Evaluation of a Solar Low-Concentration Photovoltaic/Thermal System Combined with a Phase-Change Material Cooling Technique

The high operating temperatures of photovoltaic (PV) panels negatively affect both electrical efficiency and material degradation rate. Combining both a water-cooling-based photovoltaic/thermal (PV/T) system and a phase-change material (PCM) with/without low concentration (LC) represents a promising solution for boosting the overall energy conversion efficiency of the PV system. This approach needs to be evaluated in harsh weather where the PCM should have a high melting temperature. Therefore, this study experimentally investigates the performance of three PV cooling systems, namely PV-PCM, PV/T-PCM, and LCPV/T-PCM, compared to a reference PV without cooling, under the weather conditions of Riyadh. The results show that the PV/T-PCM attained the highest daily average electrical and overall efficiencies of 14.24% (5% increase) and 42.7%, respectively, compared to 13.56% electrical efficiency of the reference panel. The electrical efficiency of the PV-PCM was 13.64% due to inefficient natural cooling in the afternoon. The LCPV/T-PCM recorded the best performance during the two hours around noon, with an average increase in electrical power and efficiency of 11.06% and a maximum overall efficiency of 70%. Finally, the LCPV/T-PCM system can be only effectively used to support the higher demand for electricity and thermal energy around noon; otherwise, a new design configuration with low concentration is needed to establish a higher electrical efficiency in most hours of sunlight

Performance Assessment of an Ice-Production Hybrid Solar CPV/T System Combining Both Adsorption and Vapor-Compression Refrigeration Systems

The technology of a hybrid solar concentration photovoltaic/thermal (CPV/T) system is an efficient way of converting solar energy to heat and electrical power, in which overall energy-extraction efficiency is at its highest. In this study, numerical dynamic simulation models were developed for a hybrid solar CPV/T system and an adsorption refrigeration system (ARS). Under the climatic conditions of Riyadh all year round, the electrical and thermal powers generated by the CPV/T system were used to estimate the ice production of both the vapor compression refrigeration system (VCS) and the ARS. The CPV/T system can provide a thermal energy of 37.6 kWh and electrical energy of 24.7 kWh a day on average over the year using a 12.5 m2 facing area of Fresnel lenses. The ARS employed an advanced approach which used Maxsorb III adsorbent packed in two aluminum foam beds. An optimum cycle time of the ARS was adapted for each month to match the variation in the thermal energy, while a variable-speed compressor was chosen for the VCS. Due to its higher coefficient of performance (COP), the proposed solar hybrid system can produce 494.4 kg of ice per day while sharing 84.5% of the VCS. The average solar COP over the year of the hybrid system can attain 0.875, which represents a promising value for a solar ice-production system

Examination of Using Aluminum-Foam/Finned-Tube Beds Packed with Maxsorb III for Adsorption Ice Production System

Producing ice using adsorption systems can represent a sustainable solution and meet the recent global environmental regulations as they use natural refrigerants and can be driven by solar energy. However, the beds used in these systems still have low thermal and adsorption characteristics. This study investigates numerically the use of an emerging aluminum foamed bed packed with advanced Maxsorb adsorbent in a two-bed adsorption system and reports cases of performance improvements compared to the classical finned-tube based system used to produce ice. A comprehensive 2-D transient pressure distribution model for the two beds was developed and validated. The model considers the temporal and spatial variations of the two beds’ parameters, while the effect of the thermal mass and heat transfer effectiveness of the condenser and evaporator components are imitated at the boundary conditions for bed openings using two zero-dimensional models. The results show the interrelated effects of varying the cycle times from 400 s to 1200 s with 2, 5, and 10 mm foam thicknesses/fin heights on the overall performance of both systems. The Al-foam based system demonstrated the performance superiority at a 2 mm foam thickness with maximum ice production of 49 kgice/kgads in 8 h, an increase of 26.6% over the counterpart finned-tube based system at a 400 s cycle time. The best COP of 0.366 was attained at a 5 mm foam thickness and 1200 s with an increase of 26.7%. The effective uptake of the Al-foam based system was reduced dramatically at a 10 mm foam thickness, which deteriorated the system performance