Basic Adsorption Cycle Research Articles

Electricity Generation Using a Hybridized Zeolite Adsorption Heat Pump and Heat Engine

The use of adsorption in Thermal Energy Storage has gained considerable research interest of late. Some applications have focused on the use of TES for transformation of low temperature heat in applications such as cooling and heating. Zeolite and water have been studied as suitable materials. Their characteristics as environmentally friendly materials and high affinity makes them conspicuous. The unique properties of zeolites to hold adsorbed water/heat with very minimal loss is also significant. With the aid of a dynamo, a Stirling engine as heat engine and the adsorption energy storage system serving as heat pump was used to generate electricity. The relationship between electricity generation and temperature was investigated. The obtained average temperature and pressure of the zeolite - water adsorption heat pump was also compared with the basic adsorption cycle.

Performance of MIL-101(Cr)/Water Working Pair Adsorption Refrigeration System Based on a New Type of Adsorbent Filling Method

MIL-101(Cr) and water were applied to adsorption refrigeration technology. MIL-101(Cr) was prepared by hydrothermal synthesis method and characterized by X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption–desorption measurement at 77 K, thermal gravimetric analysis (TGA) and scanning electron microscope (SEM). The adsorption isotherms of water vapor on MIL-101(Cr) were investigated by using a gravimetric water sorption analyzer. This study established the basic adsorption cycle mathematical model and used MATLAB/Simulink for the simulation. The control variable method was used to simulate the effect on the cooling capacity and coefficient of performance (COP) when the desorption temperature changed. When the adsorption temperature was 35 °C, the evaporation temperatures were 15 °C and 20 °C, and the amount of water vapor equilibrium adsorption on MIL-101 (Cr), Cooling power per unit adsorbent mass (SCP), and COP were measured by using the adsorption performance test rig on the basis of a new type of powder adsorbent filling method.

Heat recovery process in an adsorption refrigeration machine

In this paper, a detailed thermodynamic model based on Dubinin–Astakhov equation is given, which presents a complete and precise description of an adsorption cooling machine cycle.Heat recovery process is one of a lot of useful ways to improve the cooling performance of this kind of machines. This process is also proposed in this paper. In the proposed model, several main factors affecting the performance of cycles are discussed according to the results of computer simulations, such as the working conditions, especially the regenerating temperature, the condensation temperature, evaporation temperature and the two-adsorber temperature difference at the end of heat recovery. The relationship between the performance of the cycle and heat recovery ratio and these factors is initially investigated. The performance of heat recovery cycle is also analyzed and compared with that of the basic adsorption cycle. The obtained results showed that heat recovery can play an important role to improve the performance of an adsorption refrigeration machine.

Advancement of Solar Adsorption Cooling by Means of Heat Storage

A solar heat driven basic adsorption cooling system with silica-gel-water pair has been investigated analytically. Two cases have been studied. Performance of the chiller with different collector numbers, cycle time and heat storage. First, the performance of a basic adsorption cycle directly coupled with solar collector has been studied. Later, the performance of the chiller with heat storage has been investigated analytically. The investigation was carried on the climatic conditions of Dhaka, Bangladesh. The study reveals that heat storage is more effective than the direct solar coupling; however, it requires more collectors depending on the size of the storage tank. The analysis shows that cycle time is one of the most influential parameter for solar driven adsorption cooling system. It is also observed that the size of collector can be reduced if proper cycle time was adjusted. The analysis also revealed that the system with 20 collectors (each of 2.415m2) along with 1000s cycle time provides better performance for the base run conditions. It is also seen that the solar driven adsorption chiller with heat storage works well beyond the sunset time.

Isothermal sorption characteristics of the BaCl 2–NH 3 pair in a vermiculite host matrix

Chemisorption could be useful in adsorption systems due to the large concentration change compared with physisorption. Equilibrium concentration characteristics of ammonia with a composite adsorbent material (BaCl 2 impregnated into a vermiculite matrix) are investigated: the maximum concentration is about 0.4 kg ammonia/kg adsorbent. Hysteresis was observed between the synthesis and the decomposition reactions. The analysis of the data suggests that the hysteresis could be due to the dimensional changes of the solid during the reactions. The bi-variant behaviour observed was contrary to the mono-variant behaviour anticipated and the reasons are discussed. The COP of a basic adsorption cycle for typical ice-making and air-conditioning applications utilizing ammonia and the composite material were calculated. The results show that the material could be used for air-conditioning or other refrigeration applications. The COP could reach up to 0.6 at typical conditions ( T ev = 15 °C, T con = 35 °C).

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.

Study of the fundamentals of adsorption systems

In the design of adsorption refrigeration/heat pump systems, the characteristics of both adsorbent-adsorbate (refrigerant) pairs and adsorption cycles play an important role in various kinds of applications. The description of the performance of the adsorption-desorption process involves different modeling techniques with various simplifications, and the corresponding results are significantly different. In this paper, a thermal model based on the Dubinin-Radushkevich equation and thermodynamic analyses is given, which presents a complete and precise description of adsorption-desorption cycles. In the model, variable physical properties with temperature, such as specific heat of working pairs, isosteric heat of desorption or adsorption, are particularly considered, several main factors affecting the performance of cycles are discussed according to the results of computer simulations, such as the characteristics of working pairs and the working conditions, especially the heat capacities of generators. The relationship between the performance of the cycles and these factors is initially investigated. The performances of advanced cycles, such as the heat regenerative adsorption cycle, are also analyzed and compared with that of the basic adsorption cycle.

Influence of Microporous Characteristics of Activated Carbons on the Performance of an Adsorption Cycle for Refrigeration

The performance of an adsorption refrigerating process, quantified by the coefficient of refrigerating performance (COP), depends on the adsorbent. From the Dubinin−Astakhov equation, it is possible to calculate the performance of a basic adsorption cycle, taking the characteristics of the adsorbate and the adsorbent into account. The influence of the physical characteristics of the adsorbent on performance is shown by way of the parameters of the Dubinin−Astakhov equation: total micropore volume, W0, characteristic energy, Eo; and exponent, n. The influence of the pore size dispersion is estimated thanks to the Dubinin−Stoeckli equation and by comparison of the performances simulated with measured characteristics of several activated carbons. This study shows that there exists, for given thermodynamic conditions, an activated carbon having optimal physical characteristics that allows us to obtain the best performance.