Potential of a direct contact adsorption heat pump system for generating steam from waste water

An adsorption heat pump with a direct contact system for steam generation has been developed and the feasibility of the proposed system was confirmed both theoretically and experimentally. The basic cycle for the system has been proposed to use zeolite–water working pairs in the p‐T‐x equilibrium curve. To generate steam above 150°C from low‐energy level water at 80°C, a direct contact adsorption heat pump prototype was constructed. The experimental results show that steam could be generated by the direct contact system and the relationship between the amount of water adsorbed and the change in temperature with time is discussed. This study is expected to serve as a foundation for developing continuous adsorption heat pump systems for steam generation. Copyright © 2011 John Wiley & Sons, Ltd.     

Adsorption heat pumps for providing coupled heating and cooling effects in olive oil mills

The olive oil mill wastewater presents serious environmental threats. In this study, adsorption heat pumps utilizing zeolite coatings were proposed for olive oil mills as a helping tool for the treatment of wastewater, as well as for providing a cooling effect, which may especially be useful to prevent thermal deterioration of the olive oil. The performance of a heat pump using two adsorbers operating with waste heat was determined for different operating conditions. It was established that a sufficiently high amount of olive oil wastewater might be treated in such a system when a suitable source of waste heat is used for heating the adsorbers of the heat pump. Copyright © 2007 John Wiley & Sons, Ltd.     

A novel type of coupling cycle for adsorption heat pumps

This paper presents an adsorption heat pump system using a new coupling cycle. Experiment results and analysis show that the COP of the binary coupling cycle is higher than that of pure water–zeolite system. The system operating pressure is found to be near ambient pressure when proper concentration of ammonia is used in the system. The leakage to the system is reduced achieving long life and allowing the vessels of the system to be signed light in weight. The feasibility and reliability of the adsorption heat pump would be greatly improved by the use of the new binary adsorption cycle, providing essential benefits for industrialization.     

Exergy and energy analyses of absorption heat pumps

This paper presents a detailed thermodynamic analysis of absorption heat pumps and heat transformers. First and second law thermodynamic methods are both applied to calculate the respective energy efficiency (COP) and the energy efficiency (n) for the systems as well as the individual components. Using LiBr/H₂O as an example, two three-dimensional T-S-X diagrams for an absorption heat pump and a heat transformer are constructed by calculating the thermodynamic properties and the chemical potentials. From the calculated COP and n values, it is concluded that AHP for heating has better thermodynamic performance than both AHP for cooling and heat transformer.     

Review of mathematical investigation on the closed adsorption heat pump and cooling systems

A mathematical model of the closed adsorption heat pump and cooling systems is particularly used to assist in interpreting the observed phenomena, to design the system, to predict the trends, and to assist in optimization. In this paper, various mathematical models mainly analyzing the heat and mass transfer process of an adsorption bed in closed adsorption heat pump and cooling systems are reviewed and classified based on complexity, into three main groups: i.e. thermodynamic model; lumped parameters model; heat and mass transfer model. The major characteristics of different models and assumptions used are presented and discussed. Also, the numerical methods and validation of the models are summarized and significant results obtained through mathematical model are detailed. Although the models have evolved to a point where several features of the process can be predicted, more effort is required before the models can be applied to define actual operating conditions as well as to further investigate new closed adsorption cycles.     

Numerical study of a combined heat and mass recovery adsorption cooling cycle

A new transient two-dimensional model for the simulation of a combined heat and mass recovery adsorption cooling cycle based on the zeolite NaX/water working pair is proposed in this paper. The model describes the transfer phenomena in the adsorber in detail and is solved by control volume method. Internal and external mass transfer limitations which are neglected by many researchers are considered in the model since they have significant effects on the performance of the adsorption cooling cycle. The numerical results show that the combined heat and mass recovery cycle between two adsorbent beds can increase the coefficient of performance (COP) of an adsorption cooling system by more than 47% compared to the single bed cycle. This numerical model can be used in system optimization and design of adsorption cycles.     

Low rate energy use for heating and in industrial energy supply systems—Some technical and economical aspects

The subject hereof are two typical examples of waste heat and low-temperature heat use and the objective is to evaluate economic effectiveness taking into account various boundary conditions. The first facility considered is an “earth-coupled” heat pump with direct evaporation used as a component of a heating system. The second is an industrial installation, based on a specific project to use waste heat from the cooling process. Alternatively, four different technical options have been considered, including the use of the compression heat pump, absorption heat pump, heat transformer (absorption) and combined system with a gas motor for driving the heat pump compressor. An original simple methodology for economic analysis evaluating uses of low-temperature heat sources as elements of energy supply systems has been developed using input data taken from actual research or industrial projects. The paper also offers a comparison between such energy supply systems operating under different economic conditions of Germany and Poland.     

基于溶液除湿的风冷热泵系统性能分析

为了克服利用冷却除湿的风冷热泵空调系统机器露点过低、需要再冷和过热、难以适应显热潜热比例的变化、不能蓄能等缺点,提出基于集热再生器溶液除湿的热泵空调系统。通过济南某工程实例研究表明,与冷却除湿空调系统相比较耗电量减少12.3%,利用太阳能加热溶液除湿具有降低空调除湿能耗、利用可再生能源、减少高品位能源消耗等优势。证明太阳能溶液除湿在空调系统中是处理潜热负荷的理想选择,具有较好的节能性。     

Design of solar powered adsorption heat pump with ice storage

The design and performance of a solar (and/or natural gas) powered adsorption (desiccant-vapor) heat pump for residential cooling (and heating) is described. The entire system is modeled and analyzed: adsorption heat pump itself, ice thermal storage reservoir, and solar collectors. The adsorption heat pump embodies patent pending improvements to the state-of-the-art which elevate coefficient of performance for cooling from a maximum of 1.2 reported in the literature to a conservatively predicted minimum of 1.5. The adsorption device utilizes economical, robust configurations (shell-and-tube) and components (helical annular finned tubes, multi-lumen tubes) commonly employed in heat exchangers in a manner heretofore untried, as well as other enhancements (metal wool to diffuse heat throughout the adsorbent). The vessel is all aluminum and the adsorbent-refrigerant pair is carbon-ammonia. The ice reservoir provides 24 h cooling. Two types of solar collector are determined to be satisfactory at the selected operating temperature of 170 °C: (1) compound parabolic concentrator with high concentration ratio (10+) and automatic tilt adjustment, and (2) evacuated (0.001 atm) flat panel, similar to atmospheric pressure versions employed for domestic water heating.     

The two-stage metal hydride heat transformer

Metal hydrides can be utilized as working materials in different types ofprocesses in the field of energy technology. Among others, thermally driven heat transformationdevices are very promising solutions for the rational use of energy. Main applications forthermodynamic metal hydride machines are the heat transformer for generation of hightemperatures, or the heat pump/refrigerator for generation of both high and low temperatures.Such metal hydride machines can be used in a variety of applications due to their large operatingtemperature range. This paper gives an overview of the experimental setup of a prototype heattransformer for industrial use, providing useful heat (continuous output of about 7 kW at atemperature of about 190–200°C with a driving heat of 130–135°C and a cooling watertemperature of 40°C.     

Zeolites direct synthesis on heat exchangers for adsorption heat pumps

Improving performances of adsorption heat pumps involves developments in adsorbent materials as well as in design of more efficient adsorbers and heat exchangers. The aim of the present work was to study some aspects of the “direct synthesis” of zeolites on metal surfaces for the preparation of coated adsorbent beds for more efficient adsorption heat pumps. Different zeolites were grown on stainless steel, copper and aluminium and the results were analysed in terms of phenomena at the zeolite–metal interface, coating thickness, adhesion properties and protective effects. Direct synthesis, indeed, has demonstrated to be a valuable technique but influenced by requirements and limitations strictly dependent on the physico–chemical interaction between the material used for support and the zeolite coating considered.     

Chemical processes for energy storage and transmission

Chemical reaction, adsorption of a gas in a solid, or adsorption of gas in a liquid solvent can be used to solve problems in conservation, storage and transmission of energy. Possible applications of such processes are chemical heat pumps, cooling systems, heat transformers, chemical heat pipes, separation, storage and transmission of hydrogen. In the present paper, the principal chemical processes are described with their applications, advantages and drawbacks.     

Adsorption properties of a natural zeolite–water pair for use in adsorption cooling cycles

The equilibrium adsorption capacity of water on a natural zeolite has been experimentally determined at different zeolite temperatures and water vapor pressures for use in an adsorption cooling system. The Dubinin–Astakhov adsorption equilibrium model is fitted to experimental data with an acceptable error limit. Separate correlations are obtained for adsorption and desorption processes as well as a single correlation to model both processes. The isosteric heat of adsorption of water on zeolite has been calculated using the Clausius–Clapeyron equation as a function of adsorption capacity. The cyclic adsorption capacity swing for different condenser, evaporator and adsorbent temperatures is compared with that for the following adsorbent–refrigerant pairs: activated carbon–methanol; silica gel–water; and, zeolite 13X–water. Experimental results show that the maximum adsorption capacity of natural zeolite is nearly 0.12 kg_w/kg_ad for zeolite temperatures and water vapor pressures in the range 40–150 °C and 0.87–7.38 kPa.     

Parametric Analysis of Solar Heating and Cooling Systems for Residential Applications

Abstract

In this paper, a parametric analysis of two solar heating and cooling systems, one using an absorption heat pump and the other one using an adsorption heat pump, was performed. The systems under investigation were designed to satisfy the energy requirements of a residential building for space heating/cooling purposes and domestic hot water production. The system with the absorption heat pump was analyzed upon varying (i) the solar collectors’ area, (ii) the volume of the hot water storage, (iii) the volume of the cold water tank, and (iv) the climatic conditions. The system with the adsorption heat pump was evaluated upon varying (i) the inlet temperature of hot water supplied to the adsorption heat pump, (ii) the volume of the hot water storage, (iii) the volume of the cold water tank, and (iv) the climatic conditions. The analyses were performed using the dynamic simulation software TRNSYS in terms of primary energy consumption, global carbon dioxide equivalent emissions, and operating costs. The performance of the solar heating and cooling systems was compared with those associated with a conventional system from energy, environmental and economic points of views in order to evaluate the potential benefits.     

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–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.     

地源热泵岩土热物性测试简介与分析

地源热泵系统作为利用可再生能源的暖通空调技术,具有节能、环保等优点,在世界范围内被广泛使用。土壤作为地源热泵系统的冷热源,对整个系统有着至关重要的影响。不同建筑负荷特性要求系统对土壤的取放热量不同,二者的不平衡会使土壤的温度发生变化,影响整个系统的运行。对特定建筑地源热泵系统土壤的热物性测试是设计地埋管系统的重要依据。本文对热物性测试的理论依据进行了简单介绍,并对具体事例进行了分析计算,得出岩土体的导热系数等具体热物性参数,为地源热泵系统的精确设计提供了依据。     

Cooling performance of a vertical ground-coupled heat pump system installed in a school building

This paper presents the cooling performance of a water-to-refrigerant type ground heat source heat pump system (GSHP) installed in a school building in Korea. The evaluation of the cooling performance has been conducted under the actual operation of GSHP system in the summer of year 2007. Ten heat pump units with the capacity of 10 HP each were installed in the building. Also, a closed vertical typed-ground heat exchanger with 24 boreholes of 175 m in depth was constructed for the GSHP system. To analyze the cooling performance of the GSHP system, we monitored various operating conditions, including the outdoor temperature, the ground temperature, and the water temperature of inlet and outlet of the ground heat exchanger. Simultaneously, the cooling capacity and the input power were evaluated to determine the cooling performance of the GSHP system. The average cooling coefficient of performance (COP) and overall COP of the GSHP system were found to be ～8.3 and ～5.9 at 65% partial load condition, respectively. While the air source heat pump (ASHP) system, which has the same capacity with the GSHP system, was found to have the average COP of ～3.9 and overall COP of ～3.4, implying that the GSHP system is more efficient than the ASHP system due to its lower temperature of condenser.     

Evaluation of ground source heat pump systems for residential buildings in warm Mediterranean regions: the example of Cyprus

This paper presents a feasibility analysis for the installation of ground source heat pump systems in Cyprus. Two reference buildings, a single- and a multi-family one, are designed and analyzed using the EnergyPlus software, in order to calculate their energy needs for heating and cooling for the climate conditions of Cyprus, one of the warmest areas in Southern Europe. These energy needs are assumed to be covered by the conventional heating and cooling systems that are most widely used in Cyprus or alternatively by a ground source heat pump system, which consists of a vertical ground heat exchanger and water-to-water heat pumps and is analyzed using an in-house developed and validated code. Primary energy consumption and the resulting CO₂ emissions for both the conventional and the alternative systems are calculated and compared. Results show that the installation of the ground source heat pump system achieves in most cases substantial reductions in primary energy use for both types of buildings. As regards carbon emissions, the findings are less clear: Emissions of the geothermal system are higher than those of the conventional system for the single-family building but considerably lower for the multi-family one. From an economic perspective, the geothermal system compares favorably with the conventional systems in many cases, particularly for the multi-family building.     

一种基于排取热量平衡的地源热泵系统设计方法

地源热泵空调系统作为一种高效节能的空调系统,正得到日益广泛的应用.然而,由于建筑物的冷负荷及其运行时间往往大于供暖负荷及其运行时间,设计过程中往往取最不利情况下的负荷计算结果作为设计依据,排取热量的不平衡导致地温变化,最终影响空调运行性能.针对于此,提出了一种基于排取热量平衡的地源热泵系统设计方法.