Adsorption Air Conditioning System Research Articles

Energy and exergy analyses of a hybrid adsorption refrigeration system for simultaneous production of cold water and dry air

Current adsorption refrigeration systems are limited by dehumidification methods and produce either cold water or cold dry air. The single cooling product greatly hinders their application into situations where multiple cooling outputs are needed. In order to address this issue, this paper introduces a hybrid adsorption refrigeration system using efficient desiccant coated heat exchangers to provide both cold water and dry air via the deep utilization of input heat sources. In this study, the performance of the hybrid system is experimentally investigated from a combined perspective of energy and exergy. Results show that the hybrid system can simultaneously output cold water and dry air with a heat source of 50–80 °C. A low-temperature cooling water is beneficial to system performance, while an optimum input hot water temperature exists. At a coolant-side temperature of 25 °C, the COP reaches its maximum of 0.238 under a heat source temperature of 60 °C, and the highest exergetic efficiency is quantified as 13.9% when powered by 50 °C hot water. Increasing inlet air temperature or relative humidity facilitates the COP improvement but has a negligible effect on the exergetic efficiency. In comparison with a traditional adsorption air conditioning system, the hybrid system has a wider range of input hot water temperatures and is more advantageous in terms of cooling exergy and exergetic efficiency. This hybrid system firstly enables adsorption refrigeration to export dual cooling products of cold water and dry air, which is expected to extend adsorption refrigeration into fully automatic industrial fields.

Adsorption Solar Air Conditioning System for Singapore Climate

The design of an adsorption solar air conditioning system is investigated by using a model with an activated carbon–methanol working pair. This system is analysed with the solar insolation levels and ambient temperatures of Singapore. The proposed design mainly consists of two tubular reactor heat exchangers (TRHEXs) operating out of phase and driven by heat from an evacuated tube solar collector (ETSC). The pair of TRHEXs act as a thermal compressor and contain about 2.275 kg of activated carbon per reactor. The evacuated tube solar collector (ETSC) has better performance and is more cost effective than the flat plate solar collector (FPSC), even though it has a higher cost per unit. On the hottest day of the year, the proposed adsorption system has a maximum cooling power of 2.6 kW and a COP of 0.43 at a maximum driving temperature of 139 °C with a 9.8 m2 ETSC area. The system has a total estimated cost of EUR 10,550 corresponding to about SGD 14,800 with a 7-year payback time. At similar cooling capacities, the adsorption air conditioning system is expected to be more cost effective than the conventional system beyond an expected period of 7 years, with an expected lifetime of 15 to 20 years.

An experimental study and Performance Evaluation of a small adsorption air-conditioning system with FAM Z05 Zeolite and water

The main purpose of this work is to focus on comparing a FAM Z05 Zeolite-water and silica gel-water for designing two adsorption beds and evaluating the performance of the system. Two adsorption beds are tested in this study, the first one is using Polyvinyl acetate (PVA) glue for coating Zeolite with a weight of 1.2 kg, the second one is using polyvinylpyrrolidone (PVP) glue for coating Zeolite with a weight of 1.4 kg. The cooling water temperature of 25 °C and the chill water temperature of 20 °C are fixed during the experimental work, whereas three different hot water temperatures of 60, 70 and 80 °C are tested and changed, and five cycle’ times of 20, 25, 30, 35 and 40 minutes are changed to investigate their effects on the performance of the system. The test results show that the Coefficient of Performance (COP) on PVA glue at hot water of 70 °C is higher than that on PVP glue and this can be explained by the fact that the PVP glue blocks the porosity of the Zeolite and then deactivates the active nucleation sites which results in decreasing the adsorption of the water vapor. It is also observed that COP increases with increasing the cycle time. In addition, comparing the performance of the Zeolite adsorption bed with PVA glue to the silica-gel adsorption bed, the desorption temperature is much lower, and SCP at hot water of 80 °C is better than other types of coating glues.

Solar adsorption air conditioning system – Recent advances and its potential for cooling an office building in tropical climate

Solar adsorption air conditioning system (SADCS) is an excellent alternative to the conventional vapour compression system (VCS). SADCS has advantages over VCS system notably that it is a green cooling technology that utilizes solar energy to drive the adsorption/desorption cycle, using pure water as a green HFC-free refrigerant, mechanically simple and can be operated without moving parts other than the magnetic valves. In the last decade, several developments and innovations have been achieved in the field of SADCS research. However, further research is needed to bring this technology to practical level. Hence, this paper first discusses the literature survey that adds insights into the research of SADCS technologies with emphasis placed on the practical research that has been conducted at lab-scale and commercial level. Then, the potential of SADCS for cooling applications of an office building in tropical climate is discussed using simulation in TRNSYS. From the simulation we found that the solar fraction of the SADCS system is as high as 63 %, with the temperature and the relative humidity of an office space can reach an average of 20 °C and 60 % respectively, which are within the range of the thermal comfort level for the occupants.

Performance assessment of a solar-powered adsorption air conditioning system

Rotary desiccant air conditioning is a thermally driven and CFCs free technology which mainly uses low grade heat sources, such as solar energy and waste heat. The dehumidifier is the critical component of the desiccant air conditioning system and its performance affects in a decisive manner the effectiveness, size and manufacture cost of the whole system. This paper presents an adequate simulation tool to predict the behaviour of packed bed dehumidifier of rotary wheel type under appropriate working conditions to a solar-assisted configuration. The analysis is carried out through a one-dimensional gas-side resistance model of heat and mass transfer processes on air-solid desiccant interface and provides a large number of numerical results that can be used for design and operational optimization of the desiccant wheel.

Second Law Analysis of an Adsorption Air-Conditioning System

Abstract. Air conditioning systems are designed to improve people's living standards and provide comfort. The use of this system brings together with environmental problems, energy consumption and costs. These problems can be reduced by making studies on energy efficiency and saving in air conditioning systems. Adsorption (dehumidification, desiccant) air conditioning systems, which have widely being used in recent years, can be evaluated in terms of energy efficiency. In this study, a desiccant based air-conditioning system was considered to evaluate the system performance by using second law analysis (exergy analysis) for Yozgat province. Psychometric properties for each state and system performance parameters were calculated using Engineering Equation Solver (EES). It was found from the results that maximum exergy destruction occurs in electric heater unit and the total exergy destruction of the system is 24.66 kW. It was also found that the exergy efficiency of this system is 19.87 %. The results showed that this system can be used for air conditioning in Yozgat climate conditions and the performance of the system can be increased by using waste heat or renewable energy resources for regeneration heat. Keywords Air conditioning, Second law analysis, exergy, irreversibility Ozet. Iklimlendirme sistemleri insanlarin yasam standartlarini yukseltmek ve konfor saglamak icin tasarlanmaktadir. Bu sistemlerin kullanimi enerji tuketimi, enerji maliyetleri ve cevre problemlerini de beraberinde getirir. Bu problemler, iklimlendirme sistemlerinde enerji verimliligi ve tasarrufuna yonelik calismalar yapilarak azaltilabilmektedir. Enerji verimliligi acisindan degerlendirilebilecek iklimlendirme sistemlerinden biride son yillarda yaygin bir sekilde kullanilmakta olan adsorbsiyonlu (nem almali, desisif) iklimlendirme sistemleridir. Bu calismada, nem almali bir iklimlendirme sistemi ele alinarak sistem performansi, ikinci yasa analizi (ekserji analizi) yapilarak Yozgat iklim sartlari icin degerlendirilmistir. Sistemde bulunan butun noktalarin psikrometrik ozellikleri ve sistem performans parametreleri, Engineering Equation Solver (EES) programi kullanilarak hesaplanmistir. Yapilan calisma sonunda ele alinan sistemde en cok tersinmezligin (ekserji yikimi) isitma unitesinde meydana geldigi ve sistemin toplam tersinmezligin 24.66 kW oldugu tespit edilmistir. Ayrica sistem ikinci yasa (ekserji) verimi %19.87 olarak hesaplanmistir. Elde edilen sonuclardan sistemin Yozgat iklim sartlarinda iklimlendirme uygulamalarinda kullanilabilecegi ayrica bu tur sistemlerde rejenerasyon isisinin elde edilmesinde atik isi veya yenilenebilir enerji kaynaklarinin kullanimiyla sistem performansinin arttirilabilecegi belirlenmistir. Anahtar Kelimeler: Iklimlendirme, ikinci yasa analizi, ekserji, tersinmezlik

CPO-27(Ni) metal–organic framework based adsorption system for automotive air conditioning

Metal–organic frameworks (MOFs) are a new class of adsorbent materials that have high surface area, high pore volume, uniform pore size and highly tunable structural properties. Although many MOFs were developed mainly for gas storage applications, few were investigated for water adsorption heat pumping applications. This paper investigates the feasibility of a commercially available MOF, CPO-27(Ni), for automotive adsorption air conditioning through dynamic modelling and experimental testing. A single adsorption bed system was developed to investigate the performance of CPO-27(Ni) at different operating conditions. Also, a Simulink model was developed to simulate the performance of a 2.4kW two bed adsorption system for automotive air conditioning.Results showed that this adsorption air conditioning system can produce a specific cooling power (SCP) of 440Wkg−1 and a coefficient of performance (COP) of 0.456 at a desorption temperature of 130°C which can be obtained by the engine’s exhaust gas. Finally, a comparison between the performance of CPO-27(Ni) and advanced zeolite material (SAPO-34) was held proving that CPO-27(Ni) outperformed SAPO-34 producing 42% higher SCP value and hence leading to a more compact system.This work highlights the potential of using MOF materials in automotive air conditioning systems.

Steady-state Analysis on Thermally Driven Adsorption Air-conditioning System for Agricultural Greenhouses

In the present study, water vapor adsorption onto silica-gel, activated carbon powder (ACP) and activated carbon fiber (ACF) has been experimentally measured at 20°C, 30°C and 50°C. The adsorption data is fitted with Guggenheim–Anderson–De Boer and Dubinin–Astakhov adsorption models for silica-gel and ACP/ACF, respectively. Steady-state moisture cycled (MCSS) is determined for greenhouse demand category-I, II and III which are based on 60%, 40% and 20% relative humidity of dehumidified air, respectively. The ACP and ACF enable maximum MCSS for demand category-I and II, respectively. However, the silica-gel is found the only applicable adsorbent for demand category-III.

Design and Modeling of One Refrigeration Ton Solar Assisted Adsorption Air Conditioning System

The modeling of the performance of a one refrigeration ton (RT) solar assisted adsorption air-conditioning refrigeration system using activated carbon fiber/ethanol as the adsorbent/adsorbate pair has been undertaken in this study. The effects of hot water, cooling water, chilled water inlet temperatures, and hot water and chilled water flow rates were taken into consideration in the optimization of the system and in the design of the condenser, evaporator, and hot water storage tank. The study includes analysis of the weather data and its effect on both the adsorption system and the cooling load. This is then followed by estimation of the cooling capacity and coefficient of performance (COP) of the adsorption system as a function of the input parameters. The results of the model will be compared to experimental data in a next step.

Weather Effect on the Solar Adsorption Air-conditioning System using Activated Carbon Fiber/Ethanol as Pair of Refrigeration: A Case Study of Malaysia

This study indicates the simulation analysis of the solar adsorption cycle using the activated carbon fiber/ethanol as the pair of refrigeration in Malaysia. The heat source used was evacuated tube collectors. The cycle is used for the purpose of air-conditioning for two temperature levels, where the cooling load can be 7°C. TRNSYS simulation software was used to model the system with the weather data of Malaysia. The results showed that the weather has a high effect on the performance of the cycle. Both the cooling capacity and the COP were calculated in this study.

Numerical Analysis of a Thermal Storage Tank as Part of a 20 kW Solar/gas Adsorption Air Conditioning System

The environmental conscience is bringing up significant methods and techniques to save energy and substitute the fossil fuel resources by renewable ones. The adsorption air conditioning system at LES-UFPB has been projected by this point of view, as it is powered by solar energy. Together with it, there is a thermal storage tank whose function is to store thermal energy as long as possible, since the solar radiation changes throughout the day. This article presents a tri dimensional numerical analysis, run in Fluent CFD software, looking for the effect of inlets and outlets flow on velocity and temperature fields inside the thermal storage tank. A grid independence study was carried out and the results of velocity and temperature fields at both transient and steady flow were presented and discussed.

Performance Study of a Solar Adsorption Refrigeration System

This paper presents the simulation of a solar-powered continuous adsorption air-conditioning system with the working pair of silica gel and water. In order to make the adsorption system more suitable to use solar energy to supply cooling continuously during daytime, a new adsorption system without refrigerant valves is being developed in SJTU recently. By using this system, the problem such as pressure drop along refrigerant circuit can be resolved. The frequent switches of refrigerant valves can also be omitted. The daytime long simulation results (ranging from 6:00 to 18:00) demonstrate that the solar-powered adsorption system can supply a fairly steady cooling output all the time. Based on the results, parametric study is also undertaken to optimize the design.

Parametric study and simulation of a heat-driven adsorber for air conditioning system employing activated carbon–methanol working pair

ObjectivesThis paper aims to present a parametric study to compare with the experimental results obtained previously for a typical activated carbon–methanol, adsorption air-conditioning system powered by exhaust heat. The main objective is to study the effect of wall thickness on the desorption temperature and the cooling performance. MethodsThe current study is a simulation/parametric investigation employing computational fluid dynamics (CFD) simulation technique. ResultsIt is found that the CFD result is close to the experimental works. In this CFD investigation, an input exhaust gas of 200°C would have bed temperature around 120°C while employing 20mm thick of wall made by stainless steel. The adsorber took around 10min to heat up and decrease to room temperature around the same period. This set of data produce a cooling power of 0.65kW and COP around 0.25 with cycle time of 1200s. ConclusionIt is concluded that higher input temperature would have relatively longer cycle time but it is able to produce higher cooling power in return. While in design, it proves that an optimal wall thickness should be 15–20mm of stainless steel that offer lower heat transfer rate to maintain the system under functional Tdes at all time. Practice implicationsThis paper proves that adsorption air-conditioning system is technically applicable; however wall thickness of the adsorber should be considered seriously as one of the important parameters for suitable heat transfer and improved adsorption–desorption rate of the system.

New Adsorption Air Conditioning System Powered by Solar Energy; Operation Principals and Winter Mode Modelling and Simulation

This research focuses on the development of new adsorption air conditioning system powered by solar energy. The new system uses humidifier, heat exchanger, rotary desiccant and silica gel/water adsorption chiller. This unit is introduced to allow the production heat or cold with a good indoor air quality, and controls hygrometry. This system is powered by solar energy and does not “abuse” nature. The new design is made of five sections which are: the Pre-cooling / pre-heating, the drying, the energy recovery, the water adsorption chiller and the brewing. It permits three working modes according to the climatic conditions and to the season of the year. This work focuses on the design, modelling and numerical simulation of the air conditioning system working in winter mode. The simulation uses ambient temperature and solar flux for Gafsa city conditions to predict the behaviour of the system. Moreover, we present the evolution temperature during 24 hours in the building, the storage tank and at some point on the new system. This work includes a study of the building relative humidity, vs respectively, relative humidity at the outlet air of the humidifier and temperature of the water used for humidification

Size Reduction of an Engine Waste-Heat Driven Air- Conditioner for Passenger Cars and Light-Duty Trucks

An engine waste-heat driven adsorption air conditioning system is studied to provide cooling for vehicles to improve fuel economy.It is critical to reduce the size of the system in order to adopt the technology in the applications of passenger cars and light-duty trucks. Thus, a modular design using the zeolite-water working pair is modeled to determine the size of the system for the cooling requirement of 3.5kW during steady operation. The methods to reduce the module number and thus the size of the system are investigated and the control strategy to satisfy a high cooling requirement during thestart-up of the cooling period is also discussed.

Performance of a modified zeolite 13X-water adsorptive cooling module powered by exhaust waste heat

A modified adsorption cooling module with a working pair of 13X zeolite-water used for engineering truck air-conditioning driven by engine waste heat is presented in this paper. The cooling powers at different evaporating temperatures for the module were first tested, and the cycle operating characteristics of the module at different cooling powers were then analyzed and discussed. The performance of the cooling module is found to have a strong coupling with exterior ambient parameters such as the heat source temperature ( T hs), ambient temperature ( T a), air velocity ( v) and air relative humidity ( φ). Experiments were carried out systematically and analyzed in detail to study the effects of the ambient parameters on the module performance. Our results indicate that the demonstrated cooling module has a good performance, and the minimum evaporating temperatures corresponding to the cooling powers of 2.0 W and 10.5 W are 0.7 °C and 16.2 °C, respectively, under the conditions of T hs at 325 °C, T a at 18 °C, φ at 70%, and natural convection. Based on the presented module, a preliminary multiple module adsorption air conditioning system for engineering truck driver’s cab was also proposed in this work.

An adsorption air conditioning system to integrate with the recent development of emission control for heavy-duty vehicles

The recent development to control the emissions of large diesel engines has provided opportunities for heat-driven cooling methods in vehicles. An adsorption air conditioning system is therefore proposed in this work for heavy-duty truck application. This system is powered by engine waste heat when the engine of a truck is running. When the engine is off, it can be operated by fuel fired heaters, a newly implemented technology to reduce truck idling. Hence, this system can not only reduce engine emissions but also improve the overall energy efficiency. A lumped parameter model of the system using zeolite-water as its working pair is developed, and the adsorption capacity of zeolite is simulated with the linear driving force model. The dynamic performance of the system and a parametric study on adsorbent mass transfer, operating temperatures and cycle operating periods are presented. Alternative working pairs and the potential to commercialize the system are also discussed. This system may be designed to satisfy the cooling requirement for idle reduction of long-haul trucks.

Proof of Concept Car Adsorption Air-Conditioning System Using a Compact Sorption Reactor

A prototype compact sorption generator using an activated-carbon/ammonia pair based on a plate heat exchanger concept has been designed and built at Warwick University. The novel generator has low thermal mass and good heat transfer. The heat exchanger uses nickel brazed shims and spacers to create adsorbent layers only 4 mm thick between pairs of liquid flow channels of very low thermal mass. The prototype sorption generator manufactured has been evaluated under the European Union (EU) car air-conditioning testing conditions. While driven with waste heat from the engine coolant water (at 90°C), a pair of the current prototype generators (loaded with about 1 kg carbon in each of two beds) has produced an average cooling power of 1.6 kW with 2-kW peaks.

Experimental Study of an Automobile Exhaust Heat-Driven Adsorption Air-Conditioning Laboratory Prototype by Using Palm Activated Carbon-Methanol

Adsorption air-cooling systems powered by waste heat or solar heat can help to reduce the use of ozone-depleting substances, such as chlorofluorocarbons (CFCs) and hydro-chlorofluorocarbons (HCFCs). In recent years, these systems have faced increasing interest in many fields because they are quiet, long lasting, inexpensive to maintain, and environmentally friendly. This paper presents a laboratory prototype of an automobile adsorption air-conditioning system powered by exhaust heat, which has been successfully built and tested in the laboratory. The working pair used is a locally produced palm-derived activated carbon with methanol. Experimental results obtained show that, by having a cycle time of 20 minutes, an average chilled-air temperature of around 73.0°XF (22.6°XC) is achieved when the cooling coil temperatures fell between 49°XF to 58°XF (9.5°XC to 14.7°XC). The coefficient of performance (COP) and specific cooling power (SCP) of this prototype are approximately 0.19 and 614 Btu/h·lb (396.6 Wkg−1), respectively.

Optimum Matching of Heat Source Temperature to a Solar Adsorption Air-Conditioning System for Maximum Solar Cooling Coefficient of Performance

For solar thermal utilization, one of the main objectives is to improve system performance for reducing collector areas. In this article, the optimum heat source temperature for maximizing solar cooling coefficient of performance (COP) of a novel solar adsorption air-conditioning system (SAACS) is investigated theoretically. A mathematical model for the energy balance of the SAACS is developed. The optimum heat source temperature for the SAACS with two types of solar collector is determined by numerical simulation. The simulation results reveal that the solar cooling COP of the SAACS with evacuated tube collector can exceed 0.25 with optimum heat source temperature. Moreover, the SAACS can run with high efficiency in a wide heat source temperature range when the solar radiation is more than 700 W/m2.