Water Adsorption In Zeolites Research Articles

Numerical study of an energy storage unit based on zeolite-water adsorption for mobilized thermal energy storage

Mobile energy storage heating trucks present a promising solution to address current challenges associated with low energy utilization and reliance on a singular heat supply method. This technology seamlessly integrates waste heat recovery and thermal energy utilization, offering potential advantages such as streamlining construction cycles and providing timely energy supply in scenarios with diverse energy demands. To enhance the energy delivery efficiency of mobile heating, this paper employs computational fluid dynamics (CFD) simulation to thoroughly examine the heat accumulator at the core of an adsorption-based mobilized thermal energy storage. Furthermore, the paper conducts simulations and analyses of heat and mass transfer within a zeolite-water accumulator, closely scrutinizing variations in temperature, vapor content, and water content within the zeolite field. The results indicate that, during the heat storage process in the 3 m/s to 5 m/s system, the zeolite sensible heat storage capacity increases by 6.48 %, accompanied by a reduction in latent heat. Specifically, when the inlet steam velocity is 5 m/s compared to 3 m/s, the equilibrium heat transfer time shortens by 24.6 %. Furthermore, for an inlet steam temperature ranging from 180 °C to 220 °C, the average temperature can be elevated by 28.8 °C, resulting in a 10.6 % increase in sensible heat storage capacity. However, the heat storage time experiences a 3.4 % increase. In the exothermic process, with an inlet air velocity of 5 m/s compared to 3 m/s, there is a 22.2 % reduction in latent heat exothermic and a 16.7 % reduction in exothermic time. The inlet air temperature during the exothermic process is 8.9 °C lower than the final temperature of 20 °C, leading to a 3.2 % increase in exothermic quantity and a 20 % improvement in exothermic efficiency.

Thermodynamic performance evaluation of an innovative steam compressor using zeolite-water adsorption reactor

The industrial sector is a large energy consumer producing huge amounts of low enthalpy waste steam which can be compressed to increase its condensation pressure for its subsequent effective use. In this paper, adsorption technology was used to increase the waste steam enthalpy since this process requires small amounts of electrical energy. An innovative configuration of the adsorption compressors is presented involving direct contact between an adsorbent bed and the waste steam. The direct-contact design avoids the use of a heat exchanger between the steam and the zeolite adsorbent material, thus reducing the geometry complexity and the overall cost. The direct-contact technology is new and generally studied for heat pump purposes. This paper numerically investigates the physical feasibility of the process highlighting its main advantages and limitations. The results show a promising thermodynamic behaviour suggesting the possibility of using this adsorption compressor for several industrial processes involving higher than 7 bar steam pressure and pressure ratios up to 1.26. The steam consumption was lower than one order of magnitude of the usable compressed steam.

Optimization and experimental analysis of a solar powered adsorption refrigeration system using selective adsorbent/adsorbate pairs

Adsorption-based cooling system is a cost-effective method of heat conversion. It has the potential to dramatically enhance energy efficiency while also lowering pollutant levels. For this purpose, a solar-powered vapor adsorption refrigeration system (VAdRS) using activated carbon–methanol and zeolite–water as the working pair has been designed and experimentally evaluated. The aim of this experiment was to evaluate the coefficient of performance (COP) and specific cooling power (SCP) of a solar cooling unit by utilizing the optimum minimum and maximum mass concentration ratios. The novel solar-assisted adsorption refrigeration system optimization technique is used in this research to evaluate the optimal performance of the solar-powered VAdRS under various operating scenarios. The experiment was conducted at the optimum minimum and maximum mass concentration ratios of 0.1 and 0.2, respectively. The experimental results show that the activated carbon–methanol adsorption system produces a higher COP value than the zeolite–water adsorption system of 0.49–0.64 and 0.64–0.67 at constant evaporator and condenser temperature, respectively. It also showed that the higher SCP value was revealed in the zeolite–water-based adsorption cooling system as 207.5–217.4 kJ/kg. It was revealed that AC–methanol could be used to operate better in low-generating-temperature conditions. On the other hand, the zeolite–water adsorption system can be used at higher generating temperatures.

Performance Results of a Solar Adsorption Cooling and Heating Unit

The high environmental impact of conventional methods of cooling and heating increased the need for renewable energy deployment for covering thermal loads. Toward that direction, the proposed system aims at offering an efficient solar powered alternative, coupling a zeolite–water adsorption chiller with a conventional vapor compression cycle. The system is designed to operate under intermittent heat supply of low-temperature solar thermal energy (<90 °C) provided by evacuated tube collectors. A prototype was developed and tested in cooling mode operation. The results from the testing of separate components showed that the adsorption chiller was operating efficiently, achieving a maximum coefficient of performance (COP) of 0.65. With respect to the combined performance of the system, evaluated on a typical week of summer in Athens, the maximum reported COP was approximately 0.575, mainly due to the lower driving temperatures with a range of 75 °C. The corresponding mean energy efficiency ratio (EER) obtained was 5.8.

Life cycle analysis of ZEOSOL solar cooling and heating system

Within the context of the HVAC sector decarbonization, the market of solar driven heating and cooling systems has expanded significantly over the last years. The ZEOSOL system has as its key principle the coupling of a 12.5 kWc hybrid zeolite-water adsorption chiller with a 40 m2 solar field of vacuum tube collectors. The impact assessment has been conducted using ReCiPe 2016 method, using as reference system a conventional reversible heat pump of equal cooling capacity. The analysis indicated that the ZEOSOL system has a smaller environmental footprint in terms of impact categories such as global warming and ozone depletion potential, with a 51.2% and a 37.4% decrease of the equivalent emissions in comparison with the reference respectively. This is mainly due to the significant reduction in electricity consumption, given its high solar fraction, in contrast with the grid driven conventional system. On the other hand, the examined system performs worse in impact categories such as eco-toxicity and mineral resources scarcity, as a result of the use of large masses of copper based materials, mainly for pipelines and the solar field. On the contrary, the conventional system uses significantly less materials and therefore has better performance in the influenced categories.

Integrated ORC-Adsorption cycle: A first and second law analysis of potential configurations

Owing to the relatively limited efficiency of separate power, heating and cooling production systems, multi-generation (combined power, heat and/or cooling) has drawn a lot of attention in the recent years. The design of multigeneration systems based on the Organic Rankine Cycle (ORC) and adsorption cooling is appealing, since these technologies can utilize medium and low temperature heat including waste heat and solar energy. In the present work, a study of four potential system configurations of an integrated Organic Rankine Cycle (ORC) - adsorption cycle is carried out. For a given waste heat source, the first and second law efficiencies of the investigated configurations are calculated for a number of organic fluids considering a subcritical and a supercritical ORC. Furthermore, the systems are optimized taking into account the pinch point values in the heat exchangers. A zeolite-water adsorption chiller is considered with a nominal cooling capacity of 13 kWc. The results of each configuration are compared with that of an integrated ORC - Vapour Compression Cycle (VCC) with the same cooling capacity. The highest exergetic efficiencies for the ORC-adsorption chiller and the ORC-VCC systems are equal to 40% and 30%, respectively.

Water vapor permeation and its influence on gases through a zeolite-4A membrane

It is known that water adsorption in zeolites can severely affect the adsorption and, thus, the permeation of other gases. This work proposes an investigation about the contributions of both surface and gas translation diffusion on permeation of some light gases (H2, CH4 and CO) in the presence of water for the 4A zeolite within a wide range of temperature (300–700 K). As main results, the contributions of the two considered diffusional mechanisms and their relative weights are determined, showing in a quantitative way that the presence of water vapor significantly reduces the adsorption of the other species. The extent to what this effect influences the overall permeation process is reported considering the variation of temperature, allowing a good prediction of the permeance decrease of H2, CH4 and CO when mixed with water vapor. The water adsorption drives the permeation of the water itself, and, in the meantime, hinders the adsorption and, hence, the permeation of the other gases.

Relation of water adsorption capacities of zeolites with their structural properties

An investigation was carried out to determine the extent of relations between various structural properties of zeolite frameworks and their experimental water adsorption capacities. For this aim, average water capacity values were determined for different zeolite frameworks by utilizing water adsorption capacities reported in the literature for related materials. It was observed that the theoretical surface areas and volumes available for water adsorption in zeolites as well as the fractal dimensions of these materials exhibited some correlation with their experimental adsorption capacities. The results might give an indication of the potential for development of different zeolite frameworks, regarding their water adsorption capacities. Analogue materials of known zeolite framework structures, with different chemical compositions, which may allow for relatively high water adsorption capacities, may be prepared for such an improvement. The investigations may also be informative for the development of new zeolite-like adsorbents with relatively high capacities.

Modeling and Performance Prediction of an Adsorption Cooling System with Single Bed

This article presents a mathematical model for simulating the thermal performance of a single bed zeolite-water adsorption cooling system. A set of energy balance equations for the system components have been solved using the Engineering Equation Solver (EES) program. An experimental test loop has been installed to prove the technical visibility of the system and validate the model. The variations in the temperature of the adsorption bed, condenser, and evaporator were investigated. The system coefficient of performance (COP) varied with the mass concentration ratio of the water vapor. The optimum COP reached a value of 0.39 at a minimum and maximum adsorbate concentration ratio of about 0.077 and 0.2, respectively. The maximum COP was achieved at a heating temperature of about 170 oC. The results of the model proved an acceptable compatibility with the experimental results thus the model can be considered as a valuable tool for researcher and engineers to design and simulate the performance of the adsorption cooling system.

Hybrid Stirling engine-adsorption chiller for truck auxiliary power unit applications

This paper presents preliminary experimental test results for a novel truck auxiliary power unit (APU) design consisting of a 1 kWe free-piston Stirling engine and 2 kWt zeolite-water adsorption chiller that is powered via waste heat from the engine's cooling jacket. A prototype system was built and tested to study the interaction dynamics between the Stirling engine and adsorption chiller and to determine the performance of the chiller in extreme ambient temperature conditions. The results show that pulsed thermal loading from the chiller on the engine results in engine power spikes to 110–115% of rated power. An average COP of 0.42 ± 0.06 was achieved for the adsorption chiller. An investigation into mitigating the negative effects of low buffering was also conducted and estimates that a buffer volume of 50 litres is sufficient to minimise the effects. This volume can potentially be achieved through integration with the main truck engine eliminating the need for a supplementary tank. The proposed system has many benefits over existing technologies such as low noise, high reliability and clean emissions without any need for additional exhaust treatment.

Adsorption Cooling System Using Metal-Impregnated Zeolite-4A

The adsorption cooling systems have been developed to replace vapor compression due to their benefits of being environmentally friendly and energy saving. We prepared zeolite-4A and experimental cooling performance test of zeolite-water adsorption system. The adsorption cooling test-rig includes adsorber, evaporator, and condenser which perform in vacuum atmosphere. The maximum and minimum water adsorption capacity of different zeolites and COP were used to assess the performance of the adsorption cooling system. We found that loading zeolite-4A with higher levels of silver and copper increased COP. The Cu6%/zeolite-4A had the highest COP at 0.56 while COP of zeolite-4A alone was 0.38. Calculating the acceleration rate of zeolite-4A when adding 6% of copper would accelerate the COP at 46%.

Dynamic study of steam generation from low-grade waste heat in a zeolite–water adsorption heat pump

A novel zeolite–water adsorption heat pump system based on a direct-contact heat exchange method to generate steam from low-grade waste gas and water has been proposed and examined experimentally. Superheated steam (200 °C, 0.1 MPa) is generated from hot water (70–80 °C) and dry air (100–130 °C). A dynamic model for steam generation process is developed to describe local mass and heat transfer. This model features a three-phase calculation and a moving water–gas interface. The calculations are carried out in the zeolite–water and zeolite–gas regions. Model outputs are compared with experimental results for validation. The thermal response inside the reactor and mass of steam generated is well predicted. Numerical results show that preheat process with low-temperature steam is an effective method to achieve local equilibrium quickly, thus generation process is enhanced by prolonging the time and increasing mass of the generated steam. Besides, high-pressure steam generation up to 0.5 MPa is possible from the validated dynamic model. Future work could be emphasized on enhancing high-pressure steam generation with preheat process or mass recovery operation.

On the development of an innovative gas-fired heating appliance based on a zeolite-water adsorption heat pump; system description and seasonal gas utilization efficiency

The main objective of this work is to introduce an innovative hybrid heating appliance incorporating a gas condensing boiler and a zeolite-water adsorption heat pump. The condensing boiler is applied to drive the zeolite-water heat pump for the heating base-load and to assist the heat pump in the so called “mixed operation” mode, in which both the heat pump and the condensing boiler are working in series to cover medium heating demands. Peak heating demands are covered by the condensing boiler in the so called “direct heating” mode. The three operation modes of the hybrid heating appliance have been technically described.In addition, the laboratory test conditions for estimating the seasonal heating performance according to the German Guideline VDI 4650-2 have been introduced. For both heating systems 35/28 °C and 55/45 °C, which represent the typical operating conditions of floor and high temperature radiating heating systems in Europe, seasonal heating gas utilization efficiencies of 1.34 and 1.26 have been measured, respectively with a ground heat source.In two field test installations in one-family houses in Germany, the introduced heating appliance showed 27% more seasonal gas utilization efficiency for heating and domestic hot water production, which is equivalent to a CO2-emission reduction of 20% compared to the gas condensing boiler technology.

Performance evaluation of a zeolite–water adsorption chiller with entropy analysis of thermodynamic insight

This paper presents an environment-friendly adsorption chiller using Zeolite FAM Z01–water pair as opposed to the conventional silica gel and water pair. The adsorbent, zeolite, is thinly coated onto the surfaces of fin-tube heat exchanger for faster rates of heat and mass transfer. Another feature of the adsorption chiller is the use of a lever-countered weighted valve which can be open or closed by the pressure difference between the reactors and the condenser or evaporator. Experiments are conducted to evaluate the performance of zeolite-based chiller in terms of total heat input, cooling capacity, and coefficient of performance (COP) with respect to heat source temperature and adsorption/desorption cycle time where an optimal operational zone can be determined: (i) hot water inlet temperatures range from 65°C to 85°C, (ii) adsorption/desorption cycle times of 200–300s at optimum cooling and COP, Entropy analyses have been conducted to understand the irreversibility contributed by both the desorption and adsorption beds at assorted hot water inlet temperatures and cycle time.

Development of microwave assisted zeolite–water adsorption heat pump

A microwave assisted zeolite–water adsorption heat pump system was designed, manufactured and investigated experimentally. The influence of operation time of microwave oven on performance of the adsorption heat pump was studied. The performance criteria: coefficient of performance, specific cooling power and volumetric cooing power, were calculated for the designed and tested adsorption heat pump system. The regeneration of adsorbent bed was achieved very rapidly (35 min) by using microwave heating system. The poor thermal conductivity of adsorbent did not affect the periods of isosteric heating and isobaric desorption processes.

Experimental investigation on the effect of the switching frequency on the performance of a thermal wave adsorption heat pump

In this paper, a two modular zeolite water adsorption heat pump (AHP) based on the thermal wave concept has been experimentally investigated. Each module composes of two heat exchangers contained in a hermetic stainless steel vessel. The first heat exchanger is the adsorber/desorber located on the top of the vessel, while the second is the evaporator/condenser heat exchanger located on the bottom of the vessel. Throughout this work, the effect of the non-dimensional switching frequency, which has been introduced and theoretically investigated by Alam et al. [Int. J. Heat Mass Transfer 43 (2000) 4419–4431], on COP and the mean heating power of an adsorption heat pump has been experimentally investigated under one typical working condition of AHPs. The results showed that the switching frequency and adsorber/desorber flow rate have strong influences on both COP and the mean heating power. It has been also found that there is an optimum switching frequency corresponding to each flow rate, at which the COP attains its maximum value. The obtained optimum switching frequencies vary slightly from 0.28 at an adsorber fluid flow rate of 0.6 l.min-1 to 0.32 at 1 l.min-1 .

Cyclic steam generation from a novel zeolite–water adsorption heat pump using low-grade waste heat

Cyclic steam generation experiments from a novel zeolite–water adsorption heat pump were carried out to demonstrate the feasibility of recycling hot water and low-grade waste gas. A direct heat exchange approach was introduced to enhance heat transfer and decrease system size. The experimental steam generation rate per unit mass of zeolite is 2.44×10−5 (kg-steam/kg-zeolite)/s at regeneration for 1200s, which is 10% larger than that for 3600s. A one-dimensional model describing transport phenomena during regeneration was developed to estimate temperature distributions and local water content in zeolite at the end of regeneration. Based on the numerical results, the mass of steam generated in the subsequent process was calculated. Then, the cyclic steam generation rate can be estimated. Calculated results on steam generation rate agree with the two sets of experimental data. The calculation reveals a maximum in the steam generation rate with the change in regeneration time. Predictions also show the possibility of high-pressure steam generation from this system.

Experimental investigation on the optimal performance of Zeolite–water adsorption chiller

This paper presents the performance testing of Zeolite adsorption cooling system driven by low grade waste heat source extracted from prime mover’s exhaust, power plant’s exhaust and the solar energy. The adsorbent FAM Z01 is used as an adsorbent in the adsorption chiller facility. Owing to its large equilibrium pore volume, it has the high affinity for the water vapor adsorbate. The key advantages of the Zeolite adsorption cooling system are: (i) it has no moving parts rendering less maintenance, (ii) the energy efficient means of cooling by the adsorption process with a low temperature heat source, (iii) the use of vapor pipes are replaced by self actuating vapor valves rendering smaller footprint area and (iv) it is environmental friendly with low carbon footprint. The experimental investigations were carried out for Zeolite adsorption chiller at different key operating conditions namely (i) heat source temperature, (ii) the cycle time and (iii) the heat recovery time. It is investigated that performance of coefficient (COP) of this system could be as high as 0.48 while the waste heat source temperature is applicable as low as 55°C.

Numerical Simulation for Steam Generation Process in a Novel Zeolite–Water Adsorption Heat Pump

Numerical Simulation for Steam Generation Process in a Novel Zeolite–Water Adsorption Heat Pump

Experimental investigation of a natural zeolite–water adsorption cooling unit

In this study, a thermally driven adsorption cooling unit using natural zeolite–water as the adsorbent–refrigerant pair has been built and its performance investigated experimentally at various evaporator temperatures. The primary components of the cooling unit are a shell and tube adsorbent bed, an evaporator, a condenser, heating and cooling baths, measurement instruments and supplementary system components. The adsorbent bed is considered to enhance the bed’s heat and mass transfer characteristics; the bed consists of an inner vacuum tube filled with zeolite (zeolite tube) inserted into a larger tubular shell. Under the experimental conditions of 45 °C adsorption, 150 °C desorption, 30 °C condenser and 22.5 °C, 15 °C and 10 °C evaporator temperatures, the COP of the adsorption cooling unit is approximately 0.25 and the maximum average volumetric cooling power density (SCP v) and mass specific cooling power density per kg adsorbent (SCP) of the cooling unit are 5.2 kW/m 3 and 7 W/kg, respectively.