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NaBr is considered as one of the typical low temperature salts employed for solid sorption refrigeration. The novel concept of solid sorption heat pipe (SSHP) which integrates heat and mass transfer with solid-gas sorption technology is expected to fulfill the continuous heat transfer and alleviate the drawbacks of both conventional heat pipe and thermosyphon. In this paper, an experimental system for both sorption/desorption unit and heat transfer unit is designed and the experiments of non-equilibrium sorption/desorption performances of NaBr-NH 3 and heat transfer performances of SSHP with different molar amounts and inclination angles are carried out, respectively. The test results of sorption/desorption unit demonstrate that the increase of desorption quantity becomes very slow when the heating temperature reaches up to 75 °C and above, and with the increase of condensing pressure, the mass of ammonia desorbed from the ammoniate NaBr becomes less. The investigations of SSHP with 3 mol sorbates show that the heat transfer quantity increases significantly with the heating temperature reaches to 55 °C and above, in which the relatively higher desorption rate can be obtained. The largest value of heat transfer quantity per unit molar ammonia for 3 mol sorbates is close to that of 5 mol under the condition of heating temperature of 90 °C and cooling temperature of 20 °C. When the angle of inclination changes from 90° to 45°, the heat transfer capacity of SSHP declines more significantly compared with that of the angle from 45° to 0°. [ABSTRACT FROM AUTHOR]

A novel type solid sorption heat pipe (SSHP) is developed for continuous heat transfer. In contrast to conventional heat pipe (HP), SSHP utilizes the composite sorbent-sorbate as working media to replace the wick structure inside HP. Such a technology is expected to alleviate the heat transfer limits of conventional HP. NaBr is chosen as the sorbent, and the expanded natural graphite treated with sulfuric acid serves as the matrix. A certain molar amount of the sorbate (NH 3 ) is complexed with the composite sorbent. The desorption, condensation and chemisorption processes of NaBr-NH 3 working pairs are investigated for both vertical and horizontal placed SSHP. The results show that the desorption process of NaBr-NH 3 solid-gas reaction can be carried out while the heating temperature reaches up to 60 °C or above. The highest radial heat flux in both vertical and horizontal placed SSHP is around 22.1 and 12.4 kW/m 2 , respectively, while the axial heat flux for both SSHPs is not less than 400 kW/m 2 . It can be concluded that the SSHP is characterized by the non-isothermal heat transfer performance and verified to be available for continuous heat transfer. The vertical SSHP has a better overall heat transfer performance than horizontal SSHP under the same condition and NaBr-NH 3 working pairs applied in SSHP is suitable for low-grade thermal energy transfer above 60 °C. [ABSTRACT FROM AUTHOR]

Energy conversion technologies, especially for power generation and refrigeration, driven by the low temperature heat source are gathering the momentum recently. This paper presents a novel cogeneration cycle combining power and refrigeration with energy storage function. MnCl 2 –CaCl 2 –NH 3 is selected as the working pair. Phase change materials of “50 wt% NaNO 3 + 50 wt% KNO 3 ” and “65 mol% capric acid + 35 mol% lauric acid” are chosen for heat and cold storage, respectively. Heat and mass transfer property of composite adsorbents are investigated, and isentropic efficiency of scroll expander is tested by compressed air. Based on experimental results, a cogeneration system with power of 300 W maximum and cooling power of 2 kW is designed and analyzed. Analysis shows that total energy efficiency of cogeneration system increases from 0.316 to 0.376 and energy efficiency decreases from 0.402 to 0.391 when evaporation temperature increases from −10 to 20 °C. Cold releasing process is able to last 91 min with cold storage function. [ABSTRACT FROM AUTHOR]

For halide salt-ammonia working pairs, thermal conductivity and permeability always change with the adsorption/desorption concentration because of swelling and agglomeration phenomena during the processes of complexation and decomposition. Correspondingly, heat and mass transfer performance, which both affect the adsorption refrigeration performance, will be influenced. To provide an overview of the process mentioned above, solidified composite adsorbents that utilize expanded natural graphite (ENG) as the matrix were developed for eight different salts. Thermal conductivity and permeability were investigated for three different ratios between ENG and salt in the ammoniating process. The resulting data were compared with the data for the adsorbents that did not adsorb ammonia. The results indicate that the thermal conductivity and permeability of ammoniated salts have a strong dependence on the salt ratio and the consolidated density of the compound adsorbent. In regard to the adsorbent that was not adsorbed, the optimal thermal conductivity was 1.73 W/(m K) for the adsorbent of CaCl2-ENG with a density of 550 kg/m3 when the salt ratio was 75%. The optimal permeability was 9.02 × 10−11 m2 for the adsorbent of BaCl2-ENG with a density of 450 kg/m3 when the salt ratio was 83% in converging mode. Furthermore, the thermal conductivity and permeability of the compact compound ammoniated salts varied significantly with different concentrations of ammonia. The largest increase in thermal conductivity was as high as 1.25 W/(m K)during the adsorption process, whereas the largest decrease in permeability was as high as 5.08 × 10−11 m2 for different adsorption states. For the different adsorption working pairs, the thermal conductivity and permeability ranged from 0.62 to 2.98 W/(m K) and 1.47 × 10−14–8.13 × 10−11 m2, respectively. [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]

Abstract: Composite adsorbents, comprising activated carbon and expanded natural graphite, have been developed, and their thermal conductivity, permeability and adsorption performance were tested. The thermal conductivity varied with the ratio of activated carbon to expanded natural graphite. Thermal conductivity increased as the ratio of expanded graphite increased. Considering that the density of activated carbon for the composite adsorbent should not be lower than 200 kg/m3, otherwise the volumetric cooling capacity would be unacceptably low, the highest thermal conductivity obtained from experiments was 2.47 W m−1 K−1. The permeability was also measured, and the best result obtained was 4.378 × 10−12 m2. In order to evaluate the influence of heat and mass transfer on adsorption performance, the adsorption rate was tested using a Rubotherm magnetic suspension balance, and results showed that for the freezing conditions lower than −10 °C the performance of granular activated carbon was better than that of solidified adsorbent because of the reduced mass transfer of ammonia at low saturated pressure. The adsorption performance of consolidated adsorbents increased rapidly when the evaporating temperature was higher than −10 °C. When the evaporating temperature was 8 °C, the adsorption rate of consolidated adsorbent was improved by 29% if compared with that of granular adsorbent. [Copyright &y& Elsevier]

Abstract: In order to study the refrigeration performances of the resorption refrigeration technology, the resorption working pair of BaCl2–MnCl2–NH3, which has the similar working requirements for the heat source and cooling source, and also could satisfy the similar refrigeration requirements with the adsorption working pair of CaCl2–NH3, is studied by simulation and experiments. In the simulation the mass transfer resistance is not considered for the systems, and the refrigeration performances related with heat transfer performances are studied, results show that the resorption refrigeration system has a higher refrigeration power and COP (coefficient of the refrigeration performance) because the refrigeration effect is generated by the reaction heat compared to the latent heat of evaporation. After the simulation the experimental test unit is constructed, and the experimental data are analyzed. Results show that the resorption rate is influenced by the critical mass transfer performance very much, and the refrigeration performance is lower than that of adsorption system. The resorption system also has the problem of the larger refrigeration power loss for the reason of the sensible heat requirement of low temperature adsorber. How to improve the mass transfer performance of resorption system and decrease the influence on the refrigeration power by the sensible heat requirement of low temperature adsorber will be the key research directions for the application of resorption refrigeration systems. [Copyright &y& Elsevier]

The purpose of present study is to investigate laminar fully developed flow in a horizontal rectangular channel with the tandem cylinder sources under different Re and source positions. The boundaries in this experiment include four cases: the former cylinder is cathode and the latter cylinder is anode;the former cylinder is anode and the latter is cathode;the upper plate is cathode and two cylinders are anode; andthe two cylinders are cathode and upper plate is anode. The influence of the mass transfer rate and the boundary types between the sources have also been investigated. An experimental study of mixed convection with CuSO 4 plus; H 2 SO 4 + H 2 O solution in a horizontal channel was performed. The shadowgraph technique was used to visualize the flow and to determine the nature and effect of solutal driven secondary flows in a horizontal channel with the tandem cylinder sources inside. The ranges of the parameters studied in the present work are Pr = 5–7, Ar = 1, Sc = 1700–2400, Re = 50–200, Gr m = 1.75 × 10 5 (Re d = 7.25–29, Gr* m = 6833.6), d/H = 0.145. [ABSTRACT FROM AUTHOR]

Adsorption performances of three types of adsorbents, CaCl2 with different expansion space, simple compound adsorbent and solidified compound adsorbent made by CaCl2 and activated carbon, are tested, in which ammonia is used as refrigerant. The solidified compound adsorbent shows the best performance for adsorption ice makers on fishing boats for the larger filling quantity of adsorbent in adsorber. The mass transfer performance is improved by the additive of activated carbon in solidified compound adsorbent at the condition of low evaporating temperature. The volume cooling density of solidified compound adsorbent is about 35% improved at least in comparison with the optimal results of CaCl2 at the evaporating temperature of −15 °C. [Copyright &y& Elsevier]

An innovative resorption system is established and investigated for seasonal thermal energy storage. Solar energy is stored in form of chemical potential in summer whereas the stored energy could be released in form of sorption heat in winter. Working pair of MnCl 2 -CaCl 2 -NH 3 is selected and composite sorbents are developed with expanded natural graphite treated with sulfuric acid as the matrix for heat and mass transfer intensification. It is indicated that the highest effective heat storage density, heat power density and system COP are able to reach 1047 kJ kg −1 , 402 W kg −1 and 0.58 under the condition of 30 °C heat output temperature and 15 °C ambient temperature. Novel resorption thermal energy storage system verifies the feasibility for seasonal energy storage at high ambient temperature in winter, which reveals great potentials for solar energy utilization. Also worth noting that two possible solutions i.e. temperature upgrade mode and sorption-compression mode are analyzed and compared when ambient temperature is relatively low i.e. below 0 °C. Results demonstrate that heat could be supplied in term of −15 °C ambient temperature and 50 °C heat output temperature. Two methods could deal with the issues at low ambient temperature, which have their respective advantages for different applications. [ABSTRACT FROM AUTHOR]

A novel two-stage sorption refrigeration system is established and analyzed, which is driven by heat source with the temperature lower than 100 °C. CaCl 2 -BaCl 2 -NH 3 is selected as working pair whereas matrix of expanded natural graphite treated with sulfuric acid (ENG-TSA) is used for the improved heat and mass transfer performance of composite sorbent. The non-fin filling technique is adopted to decrease mass and volume of sorption reactor, which further improves system compactness. Results show that two-stage sorption refrigeration system is flexibly adapted to different heat source with temperature below 100 °C. COP and SCP of the novel system range from 0.185 to 0.22 and from 50 W kg −1 to 76 W kg −1 , respectively under the condition of 70 °C–90 °C heat source temperature and 5 °C–10 °C evaporation temperature. Performance of novel two-stage sorption refrigeration system is also compared with that of previous type by using the conventional fin tube sorption reactor based on mass and volume of the whole system. It is indicated that the highest improvement of SCP sys and VCP sys for the novel system are able to reach 28.1% and 32.5%, respectively when heat source temperature is 70 °C. [ABSTRACT FROM AUTHOR]

Abstract: Adsorption refrigeration and heat pump systems have been considered as important means for the efficient use of low-grade thermal energy of 60–150°C. Sorption systems are merely thermodynamic systems based on heat exchangers, and therefore a good design to optimize heat and mass transfer with reaction or sorption processes is very important, for which the notable technique is the use of expanded graphite to improve both heat and mass transfer in the chemisorption beds. Studies have also shown the need to enhance the heat transfer in adsorption bed by matching with the efficient heat transfer of thermal fluids. Heat pipes and good thermal loop design coupled with adsorption beds could yield higher thermal performance of a sorption system. A novel design with passive evaporation, known as rising film evaporation coupled with a gravity heat pipe was introduced for high cooling output. It has also been shown that the performance of traditional heat and mass recovery in the sorption systems is limited, and novel arrangement of thermal fluid and refrigerant may improve the performance of sorption systems. Based upon the above researches, various sorption systems have been developed, and high performances have been reached. [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: To improve the performance of the adsorption refrigeration of CaCl2–ammonia adsorption system, activated carbon has been distributed uniformly in the mass of CaCl2, thereby helping to enhance mass transfer and uplift the cooling power density. A multifunctional heat pipe adsorption refrigerator, in which activated carbon-CaCl2 is used as compound adsorbent and ammonia as refrigerant, is designed. Water and acetone are used as working liquids for the heat pipe. This paper presents a study on the adsorption refrigeration performances of this adsorption refrigerator under two different working conditions, ice-maker for fishing boat driven by the waste heat from exhaust gases, and solar ice-maker driven by solar water heating. The obtained average SCP (specific cooling power) and the COP (coefficient of performance) of the refrigerator were measured to be 770.4W/kg and 0.39 at about −20°C of evaporating temperature for the former working condition, and they were 161.2W/kg and 0.12 at about −15°C of evaporating temperature for the later working condition. [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]