Air to Water Generator Integrated Systems: The Proposal of a Global Evaluation Index—GEI Formulation and Application Examples

Due to water scarcity, in the last few decades, air-to-water generator (AWG) technology, whose useful effect is the extraction of water from air, has been improved. In particular, in the last few years, advanced AWG integrated systems have been developed. Such systems permit, not only to condense water from air, but also the smart use of the by-side effects of the process in order to partially or totally cover the heating ventilation air conditioning (HVAC) needs of a building. Presently, there are no evaluation tools that permit a complete comparison among AWG machines, taking into account all the useful effects that can be obtained at the same time and with the same energy input. The current work, starting from the need for such a tool, proposes a global index whose formulation considers all useful effects of an integrated system, the energy required to obtain them, and the integration degree of the machine. The index translates into a single number the system global efficiency, by means of a particular combination of existing efficiency indicators. In its extended formulation, it can be applied, not only to AWGs, but also to other HVAC integrated systems, as well as to combinations of non-integrated and integrated solutions. In addition to equations, the paper provides calculation examples and a case study in order to show the practical application and advantages of GEI.

Phase Change Materials and Their Benefits in ETICS

Phase change materials (PCMs) are materials with the ability of absorption of latent heat based on a phase change. PCMs are able to store and release a large amount of energy at certain temperatures melting or freezing. The aim of the research is to verify whether this phenomenon (material) can be used within an external thermal insulation composite system (ETICS). This is particularly the usage of PCMs in the base coat. The research is focused on two main areas. The first area concerns the water condensation on the surface of the ETICS and the associated phenomenon of algae attack. The second area concerns the warming of ETICSs with the use of dark color shades. Practical experiments showed a positive effect of PCMs on the heat-storage properties of the ETICS base coat. It was also experimentally verified that the PCM sample did not condense water vapor on the sample surface compared to the reference sample.

Application of an absorption heat pump in the conditions of an existing combined heat and power plant

The dependence of mankind on energy resources only increases with the development of scientific and technological progress. It is clear that the supply of natural energy resources will run out soon. The solution is using new energy generation technologies based on renewable and secondary sources. Due to the presence in Ukraine of operating combined heat and power plants, there is the possibility of producing thermal energy using the secondary heat by absorption heat pumps. At the same time, the thermal energy of flue gases and steam from steam turbines does not heat the atmosphere, but are involved in the generation of thermal energy for heating networks of settlements. Due to the ability of the absorbent solution to absorb and condense water vapor under the influence of low-potential and high-potential heat carriers, it is possible to significantly reduce the consumption of traditional energy resources and increase the overall efficiency of the combined heat and power plants. World experience shows that the use of secondary energy resources can significantly improve the country's energy balance. And the main problem is the availability of these resources. In today's changing climate, the use of renewable energy sources requires additional expences and it is appropriate to pay attention to use of present secondary energy resources, which are not used now. There are a lot of such resources available in heat generating facilities. This is especially noticeable in large cities with central heating networks. Therefore, increasing the efficiency of their work makes it possible to significantly improve the energy balance of the whole country and reduce tariffs for thermal energy for industry and individual consumers, which, in turn, will improve the living standards of citizens.

Experimental Study of Condensation in a Thermoacoustic Cooler With Various 3D-Printed Regenerators Using Water Vapor as the Working Fluid

Thermoacoustics (TA) deals with the conversion of heat into sound and vice versa. The device that transfers energy from a low-temperature reservoir to a high-temperature one by utilizing acoustic work is called TA cooler (TAC). The main components of a typical TAC are a resonator, a porous regenerator (e.g., stack of parallel plates), and two heat exchangers. The thermoacoustic phenomenon takes place in the regenerator where a nonzero temperature gradient is imposed and interacts with the sound wave. The low temperature at the cold end of TAC can be used to condense water from the humid air and also reduce the moisture. In the current study, the sound wave with high intensity was produced to drive a TAC to produce cooling power at a cold temperature around 18 °C, using saturated water vapor as the working fluid. The drainage of condensate in the regenerator is the key to the system’s performance. This work is dedicated to investigate the effect from temperature gradient created in TAC on the condensation enhancement, by adopting three different designs of regenerators. A 3D printer was used to design and fabricate different structures of regenerator, and then, the systematic cooling capacity was tested and compared with different regenerators. This work can be extended to evaluate how the TA effect can be affected by the condensation if humid air is directly used as the working fluid. The potential application of this investigation can be an autonomous TAC system for water harvesting in arid areas.

Performance Evaluations of Extracting Water From Dry Air Using Multi-Stage Desiccant Wheels and Vapor Compression Cycle

A water extraction device that takes water from air in dry area is proposed. This device is designed to meet domestic water demand in remote rural areas, where the climate is dry and fresh water is scarce. The device can be driven effectively by low-temperature waste heat and has the characteristics of large daily water production, low energy consumption per unit of water and high water quality. Because the moisture content of air in dry area is very low, the effect of direct condensation is limited. Solid adsorbent is able to adsorb water vapor from air at a low temperature and release water vapor at under high temperature, which can be used for water extracting from air. To improve its performance under dry circumstances, the key technical point of this device is to use solid adsorbent to collect water vapor from other air to raise its dew point temperature, and then use high temperature cold source to condense water vapor from it. In this paper, configurations of the solid adsorption are proposed, which can be driven with low regeneration temperature under the same humidity increasing amount. This device uses multi-stage desiccant wheels to realize humid increasing. Desiccant wheel can be driven with high temperature to take water vapor from dehumidification air and release water vapor to regeneration air. The multi-stage configuration is good for the reduction of regeneration temperature, making applications of low temperature waste heat form heat pumps possible. Then, influencing factors of water extracting rate are analyzed. The influencing of regeneration temperature, humid reduction amount of the humidified air and cooling and heating systems, etc., are analyzed. Last, air handling processes considering cold and heat sources are recommended to reduce energy consumption. The heat pump driven scenarios are discussed in particular. Through optimization, the water extracting rate can be increased and energy consumption per unit of water can be reduced. At present, this paper only studies air water extracting processes and thermal processes, and does not involve structure of the device, water purification and power consumption of fans, etc.

Improvement of Low Inner Surface Temperature with Use of Linear Heating Component

Not only in Austria but also in EU and worldwide is the problem concerning restoration of old buildings very present. In the soaked massive brick walls are very often, moist caused, low thermal resistance and very low surface temperature, especially in the walls corner. At the Research Centre of Building Physics, TU Vienna, was an investigation carried out, which should act solution to this problem. To compensate thermal deficits of a cold wall corner (thermal bridge) area a linear heating component has been studied in the form of a pipe-in-pipe system, which raises the temperature of the wall corner and prevents the condensation. Through a targeted local heat supply, the necessary heating power is registered, within the temperature doesn’t fall below the critical value, at which it can come to building of condense water or to formation of mould. The calculations performed with a COMSOL program were carried out using tests on a real object. Thus, the calculated and the measured values could be compared. The first results can be seen as promising in terms of heating power saving, where you don’t need to heat the whole room to a high temperature. Through the selective heat power supply in the corner area thermal bridge effect will be eliminated.

State of airway surface liquid on guinea pig trachea

Two preparations of the guinea pig trachea have been examined: an isolated preparation and a preparation in vivo, both exposed to air on the mucosal surface. Ion-selective microelectrodes have been used to measure Na (alpha Na) and K activities (alpha K) in airway surface liquid (ASL) while airflows tending either to evaporate or to condense water were applied. Other variables measured included ASL depth and transepithelial potential difference (TEPD). In isolated preparations, condensation did not progressively alter depth, alpha Na, or TEPD but caused a slight increase in alpha K. Evaporation decreased depth; increased alpha Na, alpha K, and osmotic pressure; and changed TEPD. Measurements on preparations in vivo broadly supported these observations. In addition, the depth of ASL developed on isolated preparations was related to the humidity of the air to which animals had been previously exposed. We conclude that condensation and evaporation at the ASL-air interface in isolated preparations and in preparations in vivo do significantly modify key ASL variables as does the relative humidity of the air to which animals are exposed before experimentation.