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Three types of consolidated compact composite multi-salt sorbents are studied, which are mixtures of NH 4 Cl, CaCl 2 and MnCl 2 with different proportions. The Clapeyron curves under non-equilibrium conditions and isobaric sorption/desorption curves are tested. The multi-salt sorbents show combining properties of NH 4 Cl, CaCl 2 and MnCl 2 at different temperatures. One distinguished feature of these three types of multi-salt sorbents is the disappearance of sorption hysteresis. However, there are some differences in cycle sorption quantities, which may influence refrigeration and energy storage performances for different types of multi-salt sorbents. The behaviors of different types of sorption working pairs are analyzed for continuous sorption refrigeration cycle and energy storage system. Results indicate that the multi-salt sorbents are more suitable for variable temperature heat source and low-grade heat recovery than single salt sorbents. The NH 4 Cl/CaCl 2 /MnCl 2 mixture with the mass ratio of 1:3:2 generates more cooling power than the other two with similar coefficient of performance (COP), while the multi-salt sorbent with the mass ratio of 3:2:1 is optimal for the thermochemical sorption energy storage system. Analysis of exergy efficiency and exergy destruction also shows that the multi-salt sorbents adapt better for low temperature low-grade heat. [ABSTRACT FROM AUTHOR]

Based on the earlier-established MnCl 2 /CaCl 2 –NH 3 two-stage solid sorption freezing system for a refrigerated truck, a series of optimization designs are conducted in this prototype system. For sorption beds consisting of many unit tubes, the arrangement mode is changed to the staggered arrangement. Off-the-shelf heat exchangers from refrigeration industries are chosen as the evaporator and the condenser, and an expansion valve is also used. The total mass of the optimized system is reduced to approximately 150 kg. Firstly, different refrigerating temperatures ranging from −25 °C to 0 °C are investigated, and experimental results show the optimized system can easily satisfy requirement even for transporting frozen goods. The earlier-established system can only satisfy requirement for transporting fresh goods. Simultaneously, the cycle time can be reduced to 45 min. Through the optimization, both the refrigerating capacity and the total mass of the system can satisfy requirement of this refrigerated truck. [ABSTRACT FROM AUTHOR]

Abstract: 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 (CaCl2 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. [Copyright &y& Elsevier]

The diaphragm pump is commonly utilized in the small-scale ammonia-water power cycle for pumping the liquid from absorber to evaporator. The electricity consumption and possible leakage of such a pump influence the system efficiency and reliability significantly. In order to find an alternative "pump" with high reliability and low cost, a gravity assisted thermal driven "pump" (GTP), which is consisted of three top-down organized units connecting absorber and evaporator separately, is designed. With the charging and discharging phases, the pressure in each unit fluctuates, and the level of the liquid increases and decreases alternately by the function of gravity. The results of the system show that the net work and thermal efficiency are 10.68 kW and 9.9%, respectively, when the evaporator and absorber are at 140 °C/4000 kPa and 25 °C/800 kPa separately. The optimal net work, thermal efficiency and exergy efficiency are improved by 4.87%, 3.62% and 10.06% respectively compared with the conventional cycle. An application of the GTP power cycle with the capacity of 10 kW driven by the biomass boiler is analyzed, and the results show that the electricity produced by 645 kg biomass pellets can support more than 12 households per day. Image 1 • An ammonia-water power cycle without electricity driven pump is proposed. • Gravity assisted thermal driven "pump" is designed to replace electric pump. • The maximum energy and exergy efficiency of new type cycle are 10.3% and 33.2%. • Performance of new type cycle is improved compared with conventional cycle. [ABSTRACT FROM AUTHOR]

This letter is intended to reply to the Letter to the Editor by A. Bejan and closure the discussion on the authors' published article that proposed the temperature–heat ( T – Q ) diagram methodology for adsorption refrigeration. Dr. Bejan asserted his ownership of the “ origin ” of this method and reaffirmed the “ falsehood ” of entransy in his letter. In this reply, the authors give answers and rebuttals to Dr. Bejan's comments and make some points about the academic debate on entransy. [ABSTRACT FROM AUTHOR]

As a type of traditional cycle for electricity generation, the main limitation of the Rankine cycle is the endothermic process for the evaporation (e) of water (w), which does not always fit very well with the trend of the heat source. The Kalina cycle can make up the efficiency loss by using a working fluid of water–ammonia, which has a variable heating process by adjusting the concentration of ammonia in the water absorbent. Based on the Kalina cycle, a combined power and refrigeration generating cycle has been proposed by Goswami, which generally has reasonable exergy efficiency but suffers from the low energy efficiency for the refrigeration process. In this study, a new type of the resorption cogeneration system is designed, which features a comparable electrical generating performance and much higher refrigerating performance than the Goswami cycle. The performances are analysed, and the exergy of the system is calculated. When the system works without heat recovery, ηEl and COPref range between 0.072–0.126 and 0.33–0.53, respectively; when the heat recovery cycle is included, in which the thermal capacity of the metal and the adsorbent of the adsorber are both considered, the ηEl and COPref range between 0.095–0.158 and 0.416–0.691, respectively. The highest value exergy efficiency of the system is ∼0.82, which is an improvement by 50% when compared with that of the Goswami cycle. [ABSTRACT FROM PUBLISHER]

The purpose of this letter is to reply to and closure the comment paper by M.M. Awad on the present authors' article that proposed the temperature–heat ( T – Q ) diagram methodology for adsorption refrigeration cycle. Dr. Awad did not comment on any technical content of the commented article. The comments mainly enumerated opposing views on entransy. In this letter, the present authors reiterated the theoretical basis of T – Q diagram, and gave rebuttals to Dr. Awad's comments. [ABSTRACT FROM AUTHOR]

The method of temperature–heat ( T – Q ) diagram analysis was proposed in this article. In T – Q diagram, the area between two process curves along the temperature axis represents the irreversibility degree of heat transfer, which has the same dimension with entransy dissipation. T – Q diagram can be used to optimize the heat exchange configuration and the heat exchanger network of adsorption refrigeration systems. The proposed T – Q diagram and traditional energy, exergy and entropy analyses were adopted to a multi-stage heat recovery adsorption refrigeration system. Results show that the optimal heat recovery schemes determined through T – Q diagram and cycle entropy production analyses are identical, while T – Q diagram is more intuitional since the analysis procedure is done graphically. T – Q diagram can also be applied to analyze experiment related results of process temperatures, and is capable of giving an estimation of the performance improvement for heat recovery cycle. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Heat recovery is an effective way to improve adsorption refrigeration system performance due to its easy realization and obvious improvement. Three kinds of heat recoveries (circular heat recovery is complete type and serial and passive heat recoveries are part type) have been applied in recent adsorption refrigerators. Theoretical analysis of three heat recovery methods has been done and results show that serial and passive heat recoveries (part type) are more optimal than circular heat recovery (complete type) when manufacture and cost are considered. Furthermore, a CFD model of a fin-tube type adsorber has been established and simulations of serial and passive heat recoveries have been done. The simulation results show that recovery time of passive heat recovery has an effective range whose value is approximately double of optimum recovery time. Thus, serial heat recovery is more reliable than passive heat recovery. Besides, Optimum recovery time of both serial and passive heat recoveries is approximately equal to the ratio of tube length to heating/cooling flow rate. Contribution distribution of recovered heat has also been analyzed. And the results show that contributions of fluid and tube regions are respectively 89%∼94% and 5%∼10% while contributions of adsorbent and fin regions are negligible. [ABSTRACT FROM AUTHOR]

An innovative multifunction heat pipe type sorption refrigeration system is designed, in which a two-stage sorption thermodynamic cycle based on two heat recovery processes was employed to reduce the driving heat source temperature, and the composite sorbent of CaCl2 and activated carbon was used to improve the mass and heat transfer performances. For this test unit, the heating, cooling and heat recovery processes between two reactive beds are performed by multifunction heat pipes. The aim of this paper is to investigate the cycled characteristics of two-stage sorption refrigeration system with heat recovery processes. The two sub-cycles of a two-stage cycle have different sorption platforms though the adsorption and desorption temperatures are equivalent. The experimental results showed that the pressure evolutions of two beds are nearly equivalent during the first stage, and desorption pressure during the second stage is large higher than that in the first stage while the desorption temperatures are same during the two operation stages. In comparison with conventional two-stage cycle, the two-stage cycle with heat recovery processes can reduce the heating load for desorber and cooling load for adsorber, the coefficient of performance (COP) has been improved more than 23% when both cycles have the same regeneration temperature of 103°C and the cooling water temperature of 30°C. The advanced two-stage cycle provides an effective method for application of sorption refrigeration technology under the condition of low-grade temperature heat source or utilization of renewable energy. [Copyright &y& Elsevier]

Abstract: In this paper, an innovative dual-mode multifunction heat pipe type chemisorption ice maker was designed, in which the compound adsorbent of activated carbon–CaCl2 was used to improve the mass and heat transfer performance of adsorbent. For this test unit, the heating, cooling and heat recovery processes between two adsorbent beds were performed by multifunction heat pipes without additional power consumption. Two operation modes were possible for the advanced chemisorption refrigeration system. The first operation mode was a highly efficient mass and heat recovery sorption cycle where driving heat source temperature was about 145°C. The second operation mode was a two-stage heat recovery sorption cycle in which available driving heat source temperature was about 103°C. The experimental results showed that the first operation mode cycle can increase the coefficient of performance (COP) by 69% when compared with basic cycle. The second operation mode cycle can operate effectively with relatively low-grade generation temperature, and the performance of the two-stage heat recovery cycle was improved by more than 23% when compared with conventional two-stage cycle under the same generation temperature of 103°C and cooling water temperature of 30°C. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to present the performance analysis of a multifunction heat pipe type adsorption ice maker with activated carbon–CaCl2 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. [Copyright &y& Elsevier]

A novel resorption cycle with internal heat recovery process is proposed, which is expected to further explore potentials of power and refrigeration cogeneration. Two sets of basic resorption refrigeration cycles are adopted, which are integrated with turbine/expander to realize quasi-continuous output in both half cycles. An improved cogeneration efficiency could be obtained with safety feature. Different ammonia composite sorbents with better heat and mass transfer performance are selected to investigate the overall performance when heat source temperature is in the range from 200 °C to 360 °C. It is indicated that energy efficiency for power generation is able to reach up to 0.263 at 360 °C heat source temperature while refrigeration coefficient of performance could achieve up to 1.31 at 200 °C heat source temperature. The optimal total exergy efficiency of novel resorption cogeneration cycle is as high as 0.74 by using working pair of FeCl 2 -CaCl 2 -BaCl 2 at 240 °C heat source temperature. Compared with other sorption cycles for power and refrigeration cogeneration at similar heat source temperatures, the proposed resorption cycle exhibits the highest exergy efficiency, which is about 30% higher than that of water-ammonia sorption cogeneration cycle, and twice higher than that of basic resorption cogeneration cycle. [ABSTRACT FROM AUTHOR]

Abstract: A conceptual design of a triple-effect solid–gas thermochemical sorption refrigeration system using three kinds of reactive salts and ammonia as working pairs is presented. In the proposed system, two internal heat recovery processes were employed to enhance the energy utilization efficiency. The adsorption heat of a high-temperature salt was recovered for the regeneration process of a middle-temperature salt, while the adsorption heat released by the middle-temperature salt was used to regenerate a low-temperature salt. The presented sorption refrigeration system can produce three cooling-effects in one cycle, at the expense of only one heat input at high temperature. The coefficient of performance (COP) of the system can be improved by 146–200% compared to that obtained with a conventional sorption refrigeration system. When the sensible heats of the reactant, the refrigerant and the metallic part of the reactors were considered, theoretical results showed the calculated COP employing the triple-effect sorption cycle varied between 0.75 and 0.97 with the mass ratio between the metallic part of the reactor and the reactive salt. [Copyright &y& Elsevier]