Mass Recovery Process Research Articles

Numerical Study of a Three-Bed Adsorption Chiller Employing an Advanced Mass Recovery Process with Different Cycles

In this paper, the performance comparison between two different cycles has been numerically studied. In cycle1, the configuration of beds in the three bed chiller with mass recovery were taken as uniform in size but in cycle2 the configuration of Hex3 is taken as half of Hex1 or Hex2 (where Hex1 and Hex2 are identical). In the present numerical solution, the heat source temperature variation is taken from 70°C to 90°C (for both cycle) and along with coolant inlet temperature at 30°C and the chilled water inlet temperature at 14°C. Silica gel-water is chosen as adsorbent-refrigerant pair. In the new strategy, if any one bed (3rd bed) is connect with the evaporator during pre-heating or pre-cooling time then it will give better performance than that of existing system. In this strategy, mass recovery process also occurs in all bed. Results show that the cooling capacity (CC) and coefficient of performance (COP) of the cycle1 is much better than that of the cycle2 in the range of heat source temperature from 700C to 900C.

Numerical Study of a Three-Bed Adsorption Chiller Employing an Advanced Mass Recovery Process

The performance improvement of a three-bed (equal bed) adsorption chiller employing an advanced mass recovery process has been numerically studied in this paper. The mass recovery scheme is used to improve the cooling effect and a CFC-free-based sorption chiller driven by the low-grade waste heat or any renewable energy source can be developed for the next generation of refrigeration. Silica gel/water is taken as adsorbent/adsorbate pair for the present chiller. The three-bed adsorption chiller comprises with three adsorber/desorber heat exchanger, one evaporator and one condenser. In the present numerical solution, the heat source temperature variation is taken from 500C to 900C along with coolant inlet temperature at 300C and the chilled water inlet temperature at 140C. In the new strategy, if any one bed (3rd bed) is connect with the evaporator during pre-heating or pre-cooling time then it will give better performance than that of existing system. In this strategy, mass recovery process also occurs in all bed. A cycle simulation computer program is constructed to analyze the influence of operating conditions (hot and cooling water temperature) on COP (coefficient of performance), and CC (cooling capacity).

Modeling and optimizing a two-bed adsorption cooling system with a modified mass recovery process

A two-bed adsorption refrigeration cycle (ARC) with a new proposed modified mass recovery process is investigated (modeled, optimized and compared with ARC cycle with conventional mass recovery process) here. This proposed modified mass recovery process increases the system cooling capacity and cycle exergy efficiency. These achievements reached by opening the connecting valve between two beds during mass recovery process as usual, but continuing cooling of adsorption bed by water even during mass recovery process. Thus, the refrigerant vapor moved from desorber to adsorber bed in this situation by two effects, the higher pressure of refrigerant vapor in desorber bed and also due to higher effect of adsorption process for cooling of this bed by water. Furthermore, at the end of the proposed modified mass recovery process, the equilibrium pressure of beds was closer to the evaporator pressure than that for ARC with conventional mass recovery process. Thus, the new switched adsorption bed could connect to evaporator even during pre-cooling process. This makes connecting time period of evaporator and adsorber longer than that for ARC with the conventional mass recovery process. The above effects increased the amount of refrigerant vapor adsorbed in the adsorption bed which increased ARC cooling capacity as well. Finally to study the effects of various design variables, a two bed ARC with the proposed modified mass recovery cycle is modeled and optimized for a specific cooling capacity by considering coefficient of performance and exergy destruction as two objective functions. Results for a system with 14 kW (4 refrigeration tons) cooling capacity showed 0.555, 0.284 and 1719.6 kJ for optimum values of coefficient of performance (COP, with 0.9% increase), exergy efficiency (14% increase) and total exergy destruction (16.2% decrease), respectively in comparison with those for ARC with the conventional mass recovery process.

Performance Evaluation of a Three-Bed (Unequal Bed) Adsorption Chiller Employing an Advanced Mass Recovery Process

Performance Evaluation of a Three-Bed (Unequal Bed) Adsorption Chiller Employing an Advanced Mass Recovery Process

Experimental investigation on a two-bed adsorption refrigeration system with mass recovery

• A novel continuous adsorption refrigeration system was built and tested. • Mass recovery process enhances the refrigeration performance of the system. • The optimal mass recovery time for the refrigeration cycle is 180 s in this study. • The COP of the adsorption cooling cycle with mass recovery (180 s) is 0.122. In a two-bed continuous refrigeration system, the adsorbers often switch between desorption and adsorption states. Due to this frequent switching, the refrigeration capacity is easily wasted, and energy consumption is increased, resulting in generally low refrigeration performance. In this paper, a novel continuous adsorption refrigeration system using mass recovery was built and experimentally studied. Two adsorbent tubes and activated carbon-methanol were used as the adsorbers and the working pair, respectively. The two adsorbers were separately powered by an electrical heater and hot water. Two aspects of mass recovery were researched and compared: the system performance of processes without and with mass recovery and the system performance at different mass recovery times. The results demonstrate that the mass recovery process enhances the refrigeration performance of the system. The coefficients of performance (COPs) of cycles with mass recovery (180 s) and without mass recovery are 0.122 and 0.107, respectively; mass recovery increases the COP by 14.02%. It is also indicated that there is an optimal mass recovery time for the refrigeration cycle, which is 180 s in this study. Compared with those of 160 s and 200 s cycles, the COP of the optimal system increases by 2.52% and 6.09%, respectively.

Experimental study on adsorption cooling performance of copper foams curing MIL-101/isobutane double bed system

In this paper, copper foams cured MIL-101(CFCM)/isobutane double-bed adsorption cooling system (ACS) were designed and constructed by using the CFCM unit tube adsorbers. Adsorption cooling characteristic curves of CFCM/isobutane double-bed ACS were studied. Influence of cycle parameters and mass recovery process on the cooling capacity, specific cooling power (SCP) and coefficient of performance (COP) of the CFCM/isobutane double-bed ACS was investigated. Results show that under the conditions of cycle time of 600 s, pre-cooling/pre-heating time of 120 s, condensation temperature of 15°C and hot water temperature of 85°C with the flow rate of 20 L h −1 , and cooling water temperature of 14-16°C with the flow rate of 50 L h −1 , the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS is 65.20 kJ kg −1 , 108.67 W kg −1 and 0.2260, respectively. Compared with basic cycle, the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS increases by about 26%, 24% and 22% under mass recovery time of 10 s. The cooling performance of CFCM/isobutane double-bed ACS remains stable after 100 sets consecutive basic cycles and 20 sets mass recovery cycles.

Mass Treatment of Flooded Archival Materials by Gamma Radiation

Abstract This work describes mass recovery processes of flooded archival materials at industrial scale. The presence of fungi on paper represents a threat to the integrity of the document because they degrade cellulose, one of the main components of paper. Gamma radiation treatments are investigated as mass disinfection agents for their high penetrating power, speed of treatment, and absence of risk due to chemical residuals. We compared two different recovery processes: thermal drying followed by gamma irradiation and gamma irradiation followed by thermal drying. Both these processes were conducted simultaneously on naturally contaminated archival items and on paper specimens artificially contaminated with test species. Efficacy was assessed by culture method and ATP assay, right after the treatments and after four years of storage at room temperature. Coupling gamma irradiation with a drying step with dry heat at 55–60 °C reduces the fungal loads on natural items up to levels close to the detection limits, and the reduction is maintained after four years. On artificial specimens, spore germination is completely inhibited, mycelia growth is also highly affected, but the melanised test species appear to be more resistant. A synergistic effect between gamma irradiation, water content, and thermal drying is highlighted in this paper.

Study of the salinity effects on the cooling and desalination performance of an adsorption cooling cum desalination system with a novel composite adsorbent

Adsorption cooling cum desalination systems can produce cooling effect and fresh water simultaneously, powered by low-grade heat sources. This study aims to obtain the relationship between saltwater salinity and the cooling and desalination performance, and to develop a comprehensive numerical model that can accurately predict the cooling and desalination performance of an adsorption desalination system, with the use of a novel composite adsorbent having a high water uptake and thermal conductivity. A mathematical model has been developed, considering mass recovery process, preheating/precooling process and the effect of salinity on the physical properties of saltwater, which is verified by experiments on a prototype adsorption desalination system. It turns out that the simulation results match well with the corresponding experiment results. Under the operating conditions with the desorption temperature at 85 °C and evaporation temperature at 14 °C, experiment results show that the specific cooling power and specific daily water production values are 490 W/kg and 18 m3/tonne adsorbent/day for seawater. The trend of cooling and desalination performance change vs. saltwater salinity is clearly reported. Both experiment and simulation results demonstrate that the adsorption cooling cum desalination system adopting the composite adsorbent has a great potential to sustainably provide fresh water and cooling effect.

Performance improvement of adsorption desalination system by applying mass and heat recovery processes

Adsorption desalination system (ADS) is gaining growing attention for its capability to co-produce desalinated water and cooling by utilizing waste heat and renewable energy sources. In this paper, a new operation cycle for 2-bed ADS had been introduced with the heat and mass recovery between the adsorption beds, the condenser, and the evaporator. The appropriate ADS thermodynamic mathematical model was derived and evaluated by valid experimental data. In the recovery mode, the cold water extract heat from the beds and condenser to the evaporator and two beds were connected to each other through control valves to achieve a pressure equilibrium. The specific daily water production (SDWP) for this 2-bed ADS is 9.58 m^3 /ton of silica gel/ day at the hot water temperature of 95 (°C) and the cold water temperature of 30 (°C). As a result, the SDWP of the advanced 2-bed ADS is 66% more than the conventional 2-bed ADS.

Experimental study of an adsorption chiller for extra low temperature waste heat utilization

Lots of low temperature waste heat exists in industrial fields which also requires cooling processes, i.e.: data center and glass and liquid crystal display panel manufacturing. Silica gel-water adsorption refrigeration can well match the operation temperature in waste heat utilization for these applications but its technical feasibility and experimental performance is not studied. In this paper, a silica gel-water adsorption chiller using mass recovery process is built and experimentally studied under the condition of lower than 80 °C driving hot water temperature. For the case of data center waste heat utilization, the adsorption chiller can be well operated under the condition of driving temperatures of 51.4–61.3 °C, with the COPs (coefficient of performance) of 0.285–0.477 and SCPs (specific cooling power) of 71.2–108.4 W∙kg−1 while producing 18.8–22.4 °C chilled water. For the cases of glass and liquid crystal display panel manufacturing waste heat utilization, COPs of 0.317–0.483 and SCPs of 95.2–146.7 W∙kg−1 are obtained under the conditions of driving temperatures of 56.2–74.9 °C and chilled water outlet temperatures of 14.2–16.8 °C. These experimental results indicate that feasibility in operation and good performance of silica gel-water adsorption chiller for extra low temperature waste heat utilization is confirmed.

A small-scale silica gel-water adsorption system for domestic air conditioning and water heating by the recovery of solar energy

A small-scale silica gel-water adsorption system with modular adsorber, which utilizes solar energy to achieve the cogeneration of domestic air conditioning and water heating effect, is proposed and investigated in this paper. A heat recovery process between two adsorbers and a mass recovery process between two evaporators are adopted to improve the overall cooling and heating performance. First, the adsorption system is tested under different modes (different mass recovery, heat recovery, and cogeneration time) to determine the optimal operating conditions. Then, the cogeneration performance of domestic cooling and water heating effect is studied at different heat transfer fluid temperatures. The results show that the optimal time for cogeneration, mass recovery, and heat recovery are 600 s, 40 s, and 40 s, respectively. When the inlet temperature of hot water is around 85°C, the largest cooling power and heating power are 8.25 kW and 21.94 kW, respectively. Under the condition of cooling water temperature of 35°C, the obtained maximum COPc, COPh, and SCP of the system are 0.59, 1.39, and 184.5 W/kg, respectively.

Mass recovery characteristics of hydrophobic hollow fiber membrane-based refrigerant mass exchangers in vapor absorption refrigeration systems

In thermally-driven vapor absorption refrigeration systems, a solution heat exchanger performs the heat recovery to elevate the thermal performance. This study focuses on the use of the hydrophobic hollow fiber membrane (HFM) for mass recovery of water vapor between two streams of lithium bromide (LiBr) solution across the HFM layers. We propose two configurations of the HFM-based refrigerant mass exchangers (HFM-RME): direct-contact and vacuum operating modes. A theoretical analysis explores the characteristics of the mass recovery processes based on simultaneous heat and mass transfer. Because the driving force of the water vapor mass recovery across the HFM layers is due to the difference in vapor pressures between the two streams of the LiBr solution, a larger temperature difference leads to higher mass recovery of the water vapor. In the direct-contact operating mode, the two streams of LiBr solution flow in direct contact across the HFM layers. The conduction heat transfer across the HFM layers reduces the solution temperatures along the length of the HFMs; as a result, it deteriorates the mass recovery of the water vapor. However, in the vacuum operating mode, the two streams of LiBr solution flow through each HFM, and the water vapor occupies the shell side at vacuum condition. The water vapor diffuses through the shell side, as the temperature difference between the LiBr solutions is given. The conduction heat transfer is neglected, and the solution temperature difference is adequately maintained along the HFM length, compared with the direct-contact operating mode. Therefore, the mass transfer of the water vapor, is enhanced by introducing the vacuum operating mode. The present work provides a comprehensive understanding of the heat and mass transfer characteristics in the proposed HFM-RMEs.

A novel adsorption heat pump cycle: Cascaded mass recovery cycle

Using mass recovery process can significantly improve the adsorption heat pump (AHP) system performance. A cascaded mass recovery cycle using multiple mass recovery process is proposed and studied. A theoretical calculation of silica gel–water AHP using different kinds of AHP cycle is performed and the results based on silica gel–water AHPs show that COP/CAQ of cascaded mass recovery cycle is superior to that of basic cycle or conventional mass recovery cycle. In other words, performance of AHP can be significantly improved by cascaded mass recovery cycle. Besides, cascaded mass recovery cycle is suitable for strict conditions of low heat source temperature, high heat sink temperature and low evaporation temperature, and its stage number of mass recovery is suggested to be less than 4 for convenient uses. Combined system of multi-stage and cascaded mass recovery cycle can overcome the disadvantages of high complexity and equipment cost and make the system more efficient and convenient.

Experimental study on operating features of heat and mass recovery processes in adsorption refrigeration

Combined use of heat and mass recovery processes in adsorption refrigeration is an efficient way to improve the system performance. Several kinds of heat and mass recovery processes have been proposed. In this study, a serial heat recovery process between two adsorbers and a mass recovery-like process between two evaporators is selected. Their operating features in a practical silica gel-water adsorption refrigeration system are experimentally studied. Operating features and performances of heat and mass recovery process can be presented in terms of inlet and outlet temperatures and transferred heat of two adsorbers and two evaporators. The results show that residual heat transfer fluid in the adsorbers and evaporators significantly influences the heat and mass recovery processes, respectively. In the case of this study, optimal ranges of heat and mass recovery time is 25–45 s and 5–50 s, respectively. Heat recovery process can produce negative effect when heat recovery time is beyond 45 s and it is inefficient when heat recovery time is below 25 s. Cooling effect is remarkably yielded when mass recovery time is within the range of 5–50 s.

Modeling and Simulation of Mass Recovery Process in Adsorption System for Cooling and Desalination

Abstract The intrinsic nature of adsorption cycles calls for heat and mass recovery schemes to improve the performance of the system. Energy recovery schemes become highly crucial for adsorption chiller cum desalination plants due to the unavoidable, frequent switching between the heating and cooling phases of the adsorber beds. A comprehensive numerical model for the mass recovery scheme by pressure equalization is developed and the validation with the experimental data is reported. The present model is able to capture the transient pressure response by the adsorbers during the pressure equalization process. It is observed that the specific equalization time exists for optimum mass recovery otherwise the reverse phenomenon occurs tarnishing the positive effect of the mass recovery scheme. Both the experimental and simulation results show that optimum mass recovery time is about 15 to 20 s depending on the heating/cooling temperature sources. The specific daily water production (SDWP) improvement can be as high as 5% by the mass recovery scheme which requires no additional hardware and heat source.

Design and experimental study of a silica gel-water adsorption chiller with modular adsorbers

A silica gel-water adsorption chiller driven by low-grade heat is developed. System configuration without any vacuum valves includes two sorption chambers, a 4-valve hot/cooling water coupled circuit and a 4-valve chilled water circuit. Each sorption chamber is composed of one adsorber, one condenser and one evaporator. The design of this chiller, especially the design of modular adsorber, is suitable for low-cost industrial production. Efficient and reliable heat and mass recovery processes are also adopted. This chiller is tested under different conditions and it features the periodic variations of temperatures and cooling power. Through the experimental study, the optimal cooling time, mass recovery time and heat recovery time are 720 s, 40 s and 24 s, respectively. Besides, the obtained cooling power, COP and SCP are 42.8 kW, 0.51 and 125.0 W kg−1, respectively, under typical conditions of 86/30/11 °C hot water inlet/cooling water inlet/chilled water outlet temperatures, respectively.

Optimizing performance of a three-bed adsorption chiller using new cycle time allocation and mass recovery

In this paper a new cycle time allocation for a three-bed silica-gel/water adsorption chiller is proposed and analyzed analytically. In this operating cycle lengths of all the phases are adjusted in such a way that it becomes possible to introduce mass recovery process. The result is increased cooling capacity and overall system performance. This new cycle time allocation is especially suitable for three-bed chillers driven with 60–65 °C heat source, because within this hot water temperature range the improvement of performance is the largest.The COP and SCP were calculated for a particular chiller described in the literature. Thanks to mass recovery the COP of analyzed chiller increased by 35% (from 0.268 to 0.362) at Thtf,in = 65 °C, and by 15% (from 0.350 to 0.405) at Thtf,in = 85 °C. Numerical optimization allowed to determine that at Thtf,in = 85 °C optimal mass recovery time is 8–12 s and the switching time is 27–35 s, while at Thtf,in = 65 °C optimal mass recovery time is 11–13 s and the switching time is 45–53 s.The COP of chiller running new operating cycle and cooled with Tcool,in = 30 °C is comparable to the performance of chiller running conventional operating cycle and cooled with Tcool,in = 25 °C. The SCP at Tcool,in = 30 °C and new allocation is comparable to the SCP at Tcool,in = 27.5 °C and conventional operating cycle.

Effect of Mass Recovery on the Performance of Solar Adsorption Cooling System

The study investigates the effect of mass recovery process on the performance of a conventional two bed solar adsorption cooling system with direct solar coupling mathematically. In an adsorption refrigeration system, the pressure in adsorber and desorber are different. The mass recovery scheme utilizes this pressure difference to enhance the refrigerant mass circulation. Average Cooling Capacity (ACC) and Coefficient of Performance (COP) were calculated by computer simulation to analyze the influences of operating conditions. The results show that the average cooling capacity of mass recovery system is superior to that of conventional system. It is also seen that mass recovery process enhances the overall performances of solar driven chiller and there is an optimum mass recovery time for an adsorption cooling system with direct solar coupling

Novel adsorption refrigerators with separate type two phase closed thermosyphon designs

Two adsorption refrigerators with separate type two-phase closed thermosyphon heating processes are designed to improve the heat transfer performance and to reduce the system's moving parts number and system's size. One adsorption refrigerator uses the design of three-effect separate type two-phase closed thermosyphon heating/cooling; the other one uses the design of separated separate type two-phase closed thermosyphon heating and force convection cooling. The results show that the coefficient of performance (COP) and specific of cooling power (SCP) can be improved because of the pressure difference mass recovery process. The system with the separate type two-phase closed thermosyphon heating and force convection cooling design is more attractive because fewer moving parts are used and the system's size can be reduced for building. Moreover, the thermal transfer of the adsorption beds is designed as separate type heat pipe, which can avoid the problem of corrosion from heat or sink sources, such as heavy-duty exhaust gases or seawater. Under the nominal working condition, the evaporating temperature, COP and SCP can reach −21 °C, 0.26 and 474 W kg−1. Copyright © 2015 John Wiley & Sons, Ltd.

Study and Analysis by Numerical Simulation of a Solar Continuous Adsorption Chiller

Environment and energy problems over the world have motivated researchers to develop energy systems more sustainable, having as one of the possible alternative the use of solar energy as source for cooling systems. Adsorption refrigeration systems are regarded as environmentally friendly alternatives to conventional vapour compression refrigeration systems, since they can use refrigerants that do not contribute to ozone layer depletion and global warming. In this paper a performance comparison between a solar continuous adsorption cooling system without mass recovery process and solar continuous adsorption cooling system with mass recovery process is carried out. Silica-Gel as adsorbent and water as refrigerant are selected. The results show that the adsorption refrigeration machine driven by solar energy can operate effectively during four months and is able to produce cold continuously along the 24 hours of the day. The importance of the mass recovery is proved in this study by increasing the coefficient of performance and the cooling capacity produced. For the same cooling capacity produced, the required number of solar collectors with mass recovery system is lower than the required number of solar collectors in the case of the refrigeration unit without mass recovery. For the same cooling capacity the system with mass recovery process allowed lower generation temperature.