Mass Recovery Process Research Articles

Experiment verified simulation study of the operating sequences on the performance of adsorption cooling system

In this study, simulation was conducted to investigate the effect of heat recovery, mass recovery, pre-heating and pre-cooling processes and their combinations on the system performance of a double-bed adsorption cooling system. The model developed consists of pressure variations and detailed compressible flow with flow resistance, which other similar studies had not taken into consideration, thus a detailed simulation of mass recovery, and pre-heating and pre-cooling processes is included in this study. A double-bed adsorption cooling system with silica gel and water as adsorbent-adsorbate pair was built for verifying the simulation models. Based on the simulation results, it was found that the basic cycle provided a COP and SCP of 0.20 and 57.6 W/kg, respectively. By conducting heat recovery for 30 seconds, the COP was increased by 20% to 0.24 compared to the basic cycle. The SCP was also increased to 66.4 W/kg, a 15% increase. The major advantage through conducting the mass recovery is in the SCP, whereby it was increased by 40% to 80.8W/kg. Additionally, performing only the pre-heating and pre-cooling process can also bring some benefits to the system. Therefore, for adsorption cooling systems that cannot carry out the mass recovery and/or heat recovery cycles, performing pre-heating and pre-cooling process only is recommended. This not only can reduce the cost, but also simplify the control program of the systems. Moreover, mass recovery followed by pre-heating and pre-cooling cycle is highly preferred when the SCP is the optimization target, since the SCP was hugely increased by 41% to 81.4 W/kg.

Analysis of an optimal resorption cogeneration using mass and heat recovery processes

This paper presents an optimised resorption cogeneration using mass and heat recovery to improve the performance of a novel resorption cogeneration fist proposed by Wang et al. This system combines ammonia-resorption technology and expansion machine into one loop, which is able to generate refrigeration and electricity from low-grade heat sources such as solar energy and industrial waste heat. Two sets of resorption cycle are designed to overcome the intermittent performance of the chemisorption and produce continuous/simultaneous refrigeration and electricity. In this paper, twelve resorption working pairs of salt complex candidates are analysed by the first law analysis using Engineering Equation Solver (EES). The optimal resorption working pairs from the twelve candidates under the driven temperature from 100°C to 300°C are identified. By applying heat/mass recovery, the coefficient of performance (COP) improvement is increased by 38% when the high temperature salt (HTS) is NiCl2 and by 35% when the HTS is MnCl2. On the other hand, the energy efficiency of electricity has also been improved from 8% to 12% with the help of heat/mass recovery. The second law analysis has also been applied to investigate the exergy utilisation and identify the key components/processes. The highest second law efficiency is achieved as high as 41% by the resorption working pair BaCl2–MnCl2 under the heat source temperature at 110°C.

Thermodynamic analysis and performance simulation of different kinds of mass recovery processes applied in adsorption refrigeration system

Mass recovery process is an efficient way to improve the performance of adsorption refrigeration system. By researching two kinds of conventional mass recovery cycle (i.e., mass recovery between two beds [TBMRC] and between evaporators [TEMRC]), double mass recovery cycle (DMRC) is proposed to reduce heat loss. Thermodynamic analysis shows that the heat loss of DMRC is less than the other two kinds. Consequently, DMRC system performance should be the best, followed by TEMRC and TBMRC as the worst. A mathematical model of heat and mass transfer was then built and simulation was performed to analyze the system performance. The simulation results show that the optimal cycle time and mass recovery time are 30 mins and 10 s, respectively. Compared with the basic cycle, both coefficient of performance and specific cooling power of mass recovery cycle are much better. The system performance of different kinds of mass recovery cycle is almost the same in most cases, caused by a small reduction of heat loss in DMRC or TEMRC, when compared with the cooling capacity and heating power. However, under some conditions (i.e., large cycle time or high evaporation temperature), performance of DMRC is better than the other two kinds, which is consistent with the thermodynamic analysis results.

Study of the new composite adsorbent of salt LiCl/silica gel–methanol used in an innovative adsorption cooling machine driven by low temperature heat source

An adsorption cooling machine with LiCl/Silica gel–methanol was designed and tested, which can work for air conditioning and cold storage. The machine can be driven by low temperature heat source, such as solar energy and industrial waste heat. The composite adsorbent of LiCl/Silica gel has higher adsorption capacity and the methanol has a higher working pressure. So, the cooling performance, system's reliability and the adsorbent's mass transfer performance can be improved. The adsorption machine was experimentally investigated. The test results show that the cycle time and heat recovery process has more influence on COP (Coefficient of Performance) than on cooling capacity. The mass recovery process has significant influence both on cooling capacity and COP. When the cycle time is prolonged from 460 s to 760 s, the cooling capacity and COP increased by 4.3% and 20.6%, respectively. When the hot water inlet temperature, cooling water inlet temperature, cooling medium outlet temperature and heat recovery time are 75 °C, 31 °C, 5 °C and 60 s, respectively, the cooling capacity is improved by 6.3% by heat recovery process while the COP is improved by 27.3%. When the mass recovery time extends from 50 s to 120 s, the cooling capacity and COP increase by 68.4% and 53.3%. When the hot water inlet temperature is about 88 °C, the cooling water inlet temperature is about 25 °C, the adsorption machine produced -4 °C of cooling medium, the cooling capacity and COP were about 1.0 kW and 0.13, respectively.

Performance improvement and comparison of mass recovery in CaCl2/activated carbon adsorption refrigerator and silica gel/LiCl adsorption chiller driven by low grade waste heat

One CaCl2/activated carbon-ammonia adsorption refrigerator and one silica gel/LiCl-methanol chiller was designed and tested. The comparison of performance improvement of mass recovery process on the two adsorption systems was studied. The results show that the COP (coefficient of performance) and SCP (specific of cooling power) can be improved by 15.4% and 10.5% by mass recovery process in silica gel/LiCl-methanol chiller, while they can be improved by 53.8% and 51.5% in CaCl2/acitvated carbon-ammonia refrigerator, because the latter has larger pressure difference between the hot and cold bed. Both the CaCl2/acitvated carbon-ammonia refrigerator and the silica gel/LiCl-methanol chiller can provide continuous and stable cooling capacity. Under nominal working condition, the evaporator temperature, COP and SCP can reach −21 °C, 0.26 and 474 W kg−1 in CaCl2/activated carbon-ammonia refrigerator, and they are 15 °C, 0.41 and 244 W kg−1 in the silica gel/LiCl-methanol chiller.

Experimental investigation adsorption chillers using micro-porous silica gel–water and compound adsorbent-methanol

Compound adsorbent of macro-porous silica gel/LiCl-methanol and micro-porous silica gel–water were used as working pairs in two adsorption cooling systems respectively. The adsorption performance was experimentally investigated and compared. The experiment results are that mass recovery process can improve cooling capacity significantly while heat recovery process can improve coefficient of performance (COP) more significantly. The silica gel/LiCl-methanol cooling system has higher adsorption capacity and working pressure. When the hot water inlet temperature, cooling water inlet temperature and chilled water outlet temperature are about 85°C, 31°C and 15°C, the specific cooling power (SCP) of silica gel/LiCl-methanol cooling system is higher by 59.5% than that of silica gel–water cooling system. The silica gel/LiCl-methanol cooling system can also work for cold storage. When the hot water inlet temperature, cooling water inlet temperature and chilled water outlet temperature are about 88°C, 25°C and −4°C, the cooling capacity and COP are 1.0kW and 0.13.

F203 地震災害の群集避難と復旧過程のシミュレーション(F2.社会シミュレーション,フォーラム)

F203 地震災害の群集避難と復旧過程のシミュレーション(F2.社会シミュレーション,フォーラム)

EXPERIMENTAL STUDY ON A THREE-BED ADSORPTION CHILLER

This article presents the experimental results of a three-bed advanced adsorption chiller using silica gel–water as the adsorbent–refrigerant pair. The three-bed adsorption chiller comprises three sorption elements (Hexs), one evaporator and one condenser. In the present study, the heat source temperature varies from 55°C to 80°C along with coolant inlet temperature at 30°C and the chilled water inlet temperature at 14°C. Mass recovery process occurs between Hex1 and Hex2 and no mass recovery with Hex3. The performances in terms of cooling capacity (CC) and coefficient of performance (COP) are compared with those of conventional three-bed without mass recovery scheme. Results show that three-bed with mass recovery scheme provides more CC values than those provided by the three-bed system without mass recovery scheme while it provides better COP values for 65–75°C heat source temperature.

Experimental analysis of an adsorption refrigerator with mass and heat-pipe heat recovery process

A heat pipe type adsorption refrigerator system is proposed and investigated, which can be powered by solar energy or waste heat of engine. The study assesses the performance of compound adsorbent (CaCl 2 and activated carbon)–ammonia adsorption refrigeration cycle with different orifice sets and different mass and heat recovery processes by experimental prototype machine. Specific cooling power (SCP) and coefficient of performance (COP) were calculated with experimental data to analyze the influences of operating condition. The results show that the jaw opening of the hand needle nozzle can influence the adsorption performance obviously and the thermostatic expansion valve (TEV) is effective in the intermediate cycle time in the adsorption refrigeration system. The SCP of the cycle with the mass-heat recovery together (combined recovery process) is superior to that of the conventional cycles with mass recovery or heat recovery independently.

Experimental Study on Two Beds Adsorption Chiller with Regeneration

This work is devoted to investigate the setup, charging, and the influence of the key variables on the performance of a 1.5 tons capacity two bed adsorption chiller. The beds (66.7 c m x 52.4 cm x 23.5 cm each) functions as methanol generators. The using of two generators is to build a nearly continuous adsorption-desorption cycle, by allowing the generators to work alternatively either adsorbing or desorbing the medium. The switching between desorption and adsorption phases was achieved by a simple manual electric control system. The adsorption chiller was driven by hot water, with a temperature range of 70 to 100 o C. Active carbon-methanol adsorption pair was used in this study. The chiller was charged by 11 kg of active carbon and 2.2 kg of methanol, giving an initial concentration of (0.1966 kg CH 3 OH/kg AC). It was found that using the mass recovery process increases the initial concentration of methanol in the desorption generator; hence, improving the COP and SCP of the cycle. The COP of this adsorption chiller was about 0.301, while the SCP was about 0.3532 kW/kg AC , at an outdoor temperature of 25 o C. Eventually a mass of 200 kg of water could be chilled from 10 o C to about 7 o C in about 14 min.

Influence of mass recovery on the performance of a heat pipe type ammonia sorption refrigeration system using CaCl 2/activated carbon as compound adsorbent

The performance analyses of a sorption refrigeration system with different mass recovery processes are presented, in which compound adsorbent of CaCl 2 and activated carbon is used to improve the mass and heat transfer performances of sorption bed. The heating, cooling and heat recovery processes between two sorption beds were performed by multifunction heat pipes without additional power consumption. The experimental Clapeyron diagrams showed that the cycles with mass recovery (MR), with heat and mass recoveries (HMR), and with mass and heat recoveries (MHR), have better thermodynamic performances when compared with the sorption cycle without mass recovery (MR0). The implementary order of mass recovery and heat recovery has strong influence on the efficacy of mass recovery while it has little influence on the efficacy of heat recovery. In sorption cycles with HMR and with MHR, the hot beds can be pre-cooled and cold beds can be pre-heated effectively during the switching process, and heat consumption from external heat source during desorption phase is thereby reduced. Mass recovery can enlarge cycled refrigerant mass due to the transfer of refrigerant gas between two sorption beds during mass recovery process. In comparison with sorption cycle with MR0, sorption cycles with MR, with HMR, and with MHR can generally improve the coefficient of performance (COP) and specific cooling power (SCP) by more than 20% and 16%, respectively. Especially, sorption cycle with MHR has the highest performance among different mass recovery processes due to the fact that MHR has the advantages of MR and HMR, and it can improve the COP by 46.7% when compared with the cycle with MR0.

Experimental research on dynamic operating characteristics of a novel silica gel-water adsorption chiller

A novel silica gel-water adsorption chiller consisting of two adsorption/desorption chambers and an evaporator with one heat-pipe working chamber is experimentally studied. The dynamic operating characteristics of the chiller and the thermodynamic characteristics of the adsorber are obtained. The experimental results show that the dynamic operating characteristics of the chiller and the thermodynamic characteristics of the adsorber are satisfactory and that the cycle is a novel and effective adsorption cycle. A mass recovery process increases the cyclic adsorption capacity of the system and improves adaptability of the chiller to a low-grade heat source. In addition, the experiment indicates that this novel chiller is highly suitable for an air conditioning system with a low dehumidification requirement or a system with a large cycle flowrate and an industrial cooling water system.

Performance study of a high efficient multifunction heat pipe type adsorption ice making system with novel mass and heat recovery processes

The purpose of this paper is to present the performance analysis of a multifunction heat pipe type adsorption ice maker with activated carbon–CaCl 2 as compound adsorbent and ammonia as refrigerant. For this test unit, the heating, cooling and heat recovery processes between two adsorbent beds are performed by multifunction heat pipes. A novel mass and heat recovery adsorption refrigeration cycle is developed. When mass recovery process is implemented before heat recovery process, the performance of the cycle with novel mass and heat recovery processes is much better than that for the cycle with the conventional mass and heat recovery processes. The experimental results show that the former cycle can increase the coefficient of performance (COP) and specific cooling power (SCP) by more than 17% compared with the latter cycle. In comparison with the basic adsorption cycle, the mass and heat recovery cycle can enlarge the cycled refrigerant mass and reduce the power consumption of boiler; the COP and SCP were improved by more than 11% when the mass recovery time was 20 s, while at the optimal mass recovery time of 40 s, the COP improvements for conventional and novel mass and heat recovery cycles are 43.8% and 68.7%, respectively. It was concluded that the novel mass and heat recovery processes are more beneficial to improve the performance of adsorption refrigeration system in comparison with the conventional mass and heat recovery processes.

An efficient solar-powered adsorption chiller and its application in low-temperature grain storage

A novel solar-powered adsorption cooling system for low-temperature grain storage has been built, which consists of a solar-powered water heating system, a silica gel–water adsorption chiller, a cooling tower and a fan coil unit. The adsorption chiller is composed of two identical adsorption units, each of them containing an adsorber, a condenser, and an evaporator/receiver. The two water evaporators have been incorporated into one methanol evaporator by the use of the concept of a gravity heat pipe. In order to improve the system efficiency and achieve continuous cooling production, the adsorbers are operated out-of-phase, and heat and mass recovery processes have been used. During the period from July to September of 2004, the system was put into experimental operation to cool the headspace (i.e., the air volume above the grain) of a grain bin. Three months of operation showed promising performance. The chiller had a cooling power between 66 and 90 W per m 2 of collector surface, with a daily solar cooling coefficient of performance (COP solar) ranging from 0.096 to 0.13. The electric cooling COP was between 2.6 and 3.4.

Split heat pipe type compound adsorption ice making test unit for fishing boats

In order to settle the problem of the corrosion between sea water and the steel adsorber for ammonia system, a split heat pipe type adsorption ice making test unit, which use compound adsorbent of CaCl 2 and activated carbon to improve the adsorption performance, is designed and constructed. For this test unit there is mass recovery function between two beds and the CaCl 2 in compound adsorbent per bed is 1.88 kg, and there is only one pump for the whole heating and cooling phase for adsorbers. Performances of this system are tested; the lowest evaporating temperature is as low as −42 °C. At the evaporating temperature of −35 and −25 °C, the cooling powers are 0.89 and 1.18 kW, respectively. At the evaporating temperature of −15 °C, its average cooling power is 1.37 kW, which corresponds coefficient of performance of refrigeration COP=0.41 and specific cooling power per kilogram CaCl 2 of each adsorber SCP=731 W kg −1. The mass recovery process has improved SCP and COP for the system by 15.5 and 24.1%, respectively. Heat transfer performance is also improved by the split heat pipe construction; the average heat transfer coefficient for a whole cycle is 155.8 W m −2 °C −1.

Experimental investigation of mass recovery adsorption refrigeration cycle

The study investigates the performance of silica gel–water adsorption refrigeration cycle with mass recovery process by experimental prototype machine. In an adsorption refrigeration cycle, the pressures in adsorber and desorber are different. The mass recovery cycle utilizes the pressure difference to enhance the refrigerant mass circulation. Moreover, novel cycle was proposed for improvement of cooling output. In our previous study, simulation analysis shows that mass recovery cycle has the advantage over conventional single-stage. Experiments with prototype machine were conducted to investigate the performance improvement of mass recovery cycle in the present paper. Specific cooling power (SCP) and coefficient of performance (COP) were calculated with experimental data to analyze the influences of operating conditions. The proposed cycle was compared with the single-stage cycle in terms of SCP and COP. The results show that SCP of mass recovery cycle is superior to that of conventional cycle and mass recovery cycle is effective with low temperature heat source.

Mass recovery adsorption refrigeration cycle—improving cooling capacity

The study investigates the performance of two-bed, silica gel-water adsorption refrigeration cycle with mass recovery process. The cycle with mass recovery can be driven by the relatively low temperature heat source. In an adsorption refrigeration cycle, the pressures in adsorber and desorber are different. The chiller with mass recovery process utilizes the pressure difference to enhance the refrigerant mass circulation. Cooling capacity and coefficient of performance (COP) were calculated by cycle simulation computer program to analyze the influences of operating conditions. The mass recovery cycle was compared with conventional cycle such as the single stage adsorption cycle in terms of cooling capacity and COP. The results show that the cooling capacity of mass recovery cycle is superior to that of conventional cycle and the mass recovery process is more effective for low regenerating temperature.

Experimental study of a solidified activated carbon-methanol adsorption ice maker

In this paper, the experiments are performed on an adsorption ice maker driven by waste heat, which uses up to two beds. Each bed uses methanol as refrigerant and solidified activated carbon (120 kg adsorbent totally, 60 kg adsorbent per bed) as adsorbent. This system is designed to be driven by the waste heat of a 100 kW diesel engine. The experiments show that the cooling power could be enhanced by the mass recovery process up to 11%, and the heating power could be lowered by the heat recovery process up to 30%. The optimal cooling power of this prototype is about 2.0 kW and corresponds to a specific cooling power (SCP) is about 17 W/kg with both heat and mass recoveries between two beds. Considering the optimal adsorption time is much longer than optimal desorption time at the condition of ice making, the experiments are operated on a single bed (60 kg adsorbent per bed) and the adsorption time used in experiments is two times of desorption time, then the performance of a three-bed adsorption ice maker (120 kg adsorbent totally, 40 kg adsorbent per bed) is predicted by the results of experiments on this single bed. The results of prediction show that both COP and cooling power of three-bed operation could be enhanced greatly compared to the two-bed operation; optimal SCP and COP are respectively 22 W/kg and 0.239 when mass and heat recoveries proceed between three beds. Optimal ice productivity of this three-bed system is 21 kg/h when the water temperature is 25 °C and ice temperature is −7 °C.

Study of the Effects of Mass and Heat Recovery on the Performances of Activated Carbon/Ammonia Adsorption Refrigeration Cycles

Mass recovery can play an important role to better the performance of adsorption refrigeration cycles. Cooling capacity can be significantly increased with mass recovery process. The coefficient of performance (COP) of the activated carbon/ammonia adsorption refrigeration cycle might be increased or decreased with mass recovery process due to different working conditions. The advantage is that its COP is not sensitive to the variation of heat capacity of adsorber metal and condensing and evaporating temperature. The cycle with mass and heat recovery has a relatively high COP.

Influence of degree of mass recovery and heat regeneration on adsorption refrigeration cycles

Heat regeneration and mass recovery are two ways to improve the cooling performance and the cycle cooling power of an adsorption refrigeration cycle. The definitions of the pressure coefficient of mass recovery and temperature coefficient of heat regeneration are presented in this paper to describe the degree of mass recovery and heat regeneration, as well as to discuss the combined effects of heat regeneration and mass recovery on adsorption refrigeration cycles. Besides, isothermal and adiabatic mass recovery processes are also compared in the paper.