Maisotsenko Cycle Research Articles

Recovered water from fuel cells as a supply for Maisotsenko evaporative cooling systems in a hydrogen-powered urban bus

The EU ban on the sale of new petrol and diesel cars from 2035 requires finding sustainable alternatives both from an energy and an environmental point of view. The path now seems to be drawn towards a total electrification of public and private transportation sectors. However, the issue of the limited range of electric vehicles, particularly for heavy-duty ones, still needs to be addressed. The development of fuel cell vehicles powered by compressed hydrogen, not relying exclusively on batteries, can achieve ranges comparable to those powered by fossil-fuel. The development of hydrogen vehicles must proceed in parallel with increasing the efficiency of passenger compartment air conditioning, which requires a significant share of the total energy consumed. An efficient alternative to common vapor compression cooling systems is represented by evaporative coolers, in which water evaporation is used to cool an air flow. This study investigates the feasibility of utilizing the recovered water from the exhaust gas of a hydrogen PEM fuel cell, powering an urban bus, within a commercial indirect evaporative cooling system employing the Maisotsenko cycle. The cooling capacity of the proposed system was calculated to verify the possibility of implementing it on an urban bus. The water available at the cathode of the fuel cell and the water required by the evaporative cooler were evaluated under various conditions and compared. The calculations demonstrate that even under intense weather conditions, where approximately 40 kg of water may be required every hour, at least 10 % of water needed by the evaporative cooling system can be provided by the water produced through the hydrogen reaction. In mild weather conditions or by cooling the exhaust, it is possible to significantly increase the share of pure water supplied to the evaporative system. The integration of hydrogen fuel cells and evaporative coolers in bus equipment can be an energy-efficient, win–win solution. This configuration enables the dual utilization of the hydrogen employed to drive the fuel cell.

Analytical modelling of an indirect evaporative cooler based on the Maisotsenko cycle for HVAC applications

Highly-efficient evaporative cooling systems can significantly reduce the energy use in buildings, thereby contributing to meet Europe’s climate commitments, including building decarbonisation by 2050. The Maisotsenko Cycle is an indirect, multi-stage type of evaporative cooling which can be used in different air-conditioning applications. The main objective of this study is to develop an analytical model of an indirect evaporative cooler based on the Maisotsenko cycle for HVAC applications. The conservation equations governing the heat and mass transfer processes occurring in the indirect evaporative cooler were solved by means of numerical methods, and the results provided by the model were validated using experimental data reported in the literature (differences lower than 2%). Finally, a parametric study was conducted where the influence of various operational and environmental variables on the system's performance were numerically analysed.

Transient analysis of an efficient solar assisted air-conditioning system for subtropical climate with various solar thermal collectors

The air conditioning demand of the world is largely fulfilled by vapor compression systems; however, these systems are also responsible for depleting ozone layer due to the nature of refrigerants. Desiccant cooling systems integrated with solar thermal energy technologies could be an attractive alternative with some performance enhancement techniques. In this study, transient seasonal performance investigation is performed for an innovative solar integrated desiccant cooling system that uses regenerative evaporative cooler known as solar assisted desiccant integrated Maisotsenko cycle cooler for better cooling performance. Furthermore, transient annual performance analysis of solar system for meeting thermal energy requirement for regenerating the desiccant wheel in summer season and handling heating load of the building in winter season is also carried out with three different solar thermal collector technologies for finding out more efficient technology. The key performance indicators in this study are useful energy gain, solar source efficiency, auxiliary energy sharing, coefficient of performance, and solar fraction. The results of the key performance parameters are reported as monthly average values. The proposed integrated system resulted to be very efficient with a maximum COP value of 1.13 in April when latent cooling loads are low and 0.78 in August when latent cooling loads are higher. The system’s maximum cooling capacity is 24 kW in April corresponding to a sensible heat factor of 0.720. Furthermore, the regeneration temperature requirements ranged from 50 °C to 78 °C, respectively that makes it favorable to use low grade thermal energy through non concentrating solar thermal collectors. The regeneration thermal energy requirement for desiccant wheel fluctuates throughout the year, maximizing in August due to higher dehumidification requirements. The study also revealed that the evacuated tube collector technology is most suitable with average annual efficiency of around 36 %.

Performance predication of a solar assisted desiccant air conditioning system using radial basis function neural network: An integrated machine learning approach

In this Paper solar desiccant air conditioning system integrated with cross flow Maisotsenko cycle (M-cycle) indirect evaporative cooler is used to investigate the performance of whole system in different range of parameters. Solar evacuated tube electric heater is used to supply the regeneration temperature to the desiccant wheel, whereas, Desiccant Wheel (DW) and M-cycle is used to handle latent load and sensible load separately. Major contribution of this research is to predict system level performance parameters of a Solar Assisted Desiccant Air Conditioning (Sol-DAC) system using Radial Basis Function Neural Network (RBF-NN) under real transient experimental inlet conditions. Nine parameters are mainly considered as input parameters to train the RBF-NN model, which are, supply Air temperature at the process side of desiccant wheel, supply air humidity ratio at process side of the desiccant wheel, outlet temperature from the desiccant wheel at process side, outlet humidity ratio from the desiccant wheel at process side, regeneration temperature at regeneration side of the DW, outlet temperature from the heat recovery wheel at process side, outlet humidity ratio out from the Heat Recovery Wheel (HRW) at process side, temperature before heat recovery wheel regeneration side of the system, humidity ratio before heat recovery wheel regeneration side of the system. Four parameters are considered as the output of the RBF-NN model, namely: output temperature, output humidity, Cooling Capacity (CC), and Coefficient of Performance (COP). The results of the RBF-NN model shows that the best Mean Squared Error (MSE) and Regression coefficient (R) for outlet temperature prediction are 0.00998279 and 0.99832 when regeneration temperature is 70 °C and inlet humidity at 18 g/kg. Best MSE and R for predication of outlet humidity are 0.0102932 and 0.99485 when the regeneration temperature is 70 °C and inlet humidity at 16 g/kg. Best MSE and R for predication of COP are 0.0106691 and 0.9981 when the regeneration temperature is 70 °C and inlet humidity 12 g/kg. Best MSE and R for predication of CC are 0.0144943 and 0.99711 when the regeneration temperature is 70 °C and inlet humidity 14 g/kg. Experimental and predicted performance parameters were in close agreement and showed minimal deviation. Investigations of predicted results revealed that trained RBF-NN model was capable of predicting the trend of output result under the varying input condition.

Efficient harvesting of renewable evaporative energy from atmospheric air through hierarchical nano/microscale shaping of air-water interface

Renewable evaporative energy from atmospheric air is a recently emerged research field that demonstrates the great potential for significant energy savings in the air conditioning of buildings, data/big-data/integrated-big-data centers, agricultural storage facilities, and greenhouses. Here, we develop a method for an essential increase in the harvesting efficiency of renewable air evaporative energy by enhancing the water evaporation rate through the shaping of the air-water interface (AWI) by the menisci formed in superhydrophilic hierarchical surface nano/microstructures. Using this method, we achieve a 10-fold rise in the evaporation rate for the microscale AWI shaping. For the first time, we discover the superevaporation effect that provides an unprecedented 130-fold rise in the evaporation rate at the hierarchical nano/microscale AWI shaping. Furthermore, based on these findings, for the first time, we elaborate a novel material with an engineered AWI for a significant increase in the harvesting of renewable air evaporative energy in the dew point (Maisotsenko cycle) indirect evaporative air conditioning systems whose operation is fundamentally based on utilizing renewable air evaporative energy. The dew point cooling device fabricated using this novel material shows significantly superior cooling performance, validating the substantially enhanced harvesting of the air's evaporative energy. Our findings can essentially advance the emerging field of renewable air evaporative energy and, besides the air conditioning technology, can provide significant efficiency enhancements in water purification/desalination, thermal management, gas turbine power generation, and waste heat recovery technologies.

Biochar powders coating to improve evaporative cooling in Maisotsenko-cycle systems

This work presents an experimental study on the performance of biochar powder coatings on aluminum surfaces for use in indirect evaporative coolers based on the Maisotsenko cycle. The performance of the biochar coated samples was compared to cellulose-coated aluminum samples and uncoated ones. Results showed that biochar coatings improved the performance of uncoated aluminum, with the 150 μm particle size coating offering performance comparable to cellulose. However, wetting times were longer, which has implications for spraying strategies.

Water-energy nexus in the combined cycle power plant using energy, exergy, economic and environmental analyses

The growing demand for water and energy and the limitation on their resources necessitate comprehensive studies on the water-energy nexus from different aspects in large industries, especially power plants. In the present study, the water-energy nexus has been analyzed using energy, exergy, economic, and environmental analyses for the retrofit scenarios in a combined cycle power plant. The injection of boiler blow-down into the condenser will save 47809.5 m3 of make-up water and 1.115 million m3 of natural gas per year. Replacing the Maisotsenko evaporative cooler with the fogging system increases the revenue index and the water consumption index by 2.7%. The raw water is replaced with high-quality water. The output power of the combined cycle power plant is reduced by 2.1 MW (0.83%) due to the steam injection from the heat recovery boiler into the combustion chamber of the gas unit, while its exergy degradation rate is reduced by 8.5 MW (2.42%). Also, the efficiency of the first and second laws have been decreased by 0.49% and 0.4%, respectively. The results show that the recovery of boiler blow-down for condenser or steam injection into the combustion chamber of the gas unit from heat recovery of the boiler reduces water consumption and exergy destruction simultaneously. Using Maisotsenko cycle and steam injection into the combustion chamber of the gas unit from the heat recovery of boiler reduces the exergy destruction and NOx emissions. The present study provides useful insights to quantify the water-energy nexus for decision-makers in the industry to reach proper decisions according to the opportunities and limitations.

Sustainability framework of intelligent social houses with a synergy of double-façade architecture and active air conditioning systems

Social houses are built around the world to fulfill the basic needs of the growing population, especially middle-income families. Owing to the low budget available for such houses around the globe, necessary energy codes are often compromised. This research, through a methodological sustainability framework, presents the case study of Mexico with the objective to address this worldwide issue. More than 100,000 social houses were built in Mexico just in the year 2021 without strictly following any definitive building energy codes. Eventually, this is a ticking bomb, if left unaddressed, that can bring serious energy and environmental consequences connected with various social issues. Thus, as a research gap, the conventional 4E (energy, exergy, economic, and environmental) analysis cannot fully address such a complex energy-environmental-economic-social nexus. This work proposes an integrated sustainability framework of the practicability of the bioclimatic architecture of such a social house including energy, economic, environmental, and social assessment (novel addition to the analysis). The novel methodology is implemented on a novel technological advancement where double-façade architecture (i.e., solar chimney) is installed through a synergy and intelligent operation with an active air conditioning system including a desiccant enhanced air cooler and novel dew-point evaporative cooler. The article makes use of conventional physics-based modeling of thermal machines combined with an artificial neural network digital twin-based data-driven non-sorting genetic optimization of solar chimneys for various climatic conditions of Mexico. The optimal points are evaluated using annual climatic data to maintain the thermal comfort conditions and the results have suggested an increase of ∼48% through intelligent integration of double-façade architecture with the Maisotsenko cycle air cooler. Life-cycle economic assessment has suggested the Levelized cost of air conditioning be between 0.0096 and 0.0390 USD/kWh and can save up to ∼273 MXN per month with a real payback period of ∼8 years. Environment assessment has reported mitigation of up to ∼5668.59 kgCO2/year as compared to conventional vapor compression refrigeration systems. The social assessment is conducted on a pilot scale to directly ask the people of Mexico about their perception of the installation of the solar chimney while giving the fact that the initial price of the social houses can increase between 2.5 and 4%. It is reported that ∼62% of the sample is willing to install it even with a high price tag with a motive to initiate the climate change mitigation phenomena. The importance of the work has concluded that the government needs to take drastic and tough decisions to further regulate the energy efficiency in the social houses and limit the constructors to offer sustainable building construction.

Performance investigation of solar assisted desiccant integrated Maisotsenko cycle cooler in subtropical climate conditions

Air conditioning has become an integral part of buildings due to climate change and global warming. About 40% of the world energy is being consumed by the building sector, with around 50% share of HVAC applications. In the current study, the simulation-based performance of solar desiccant integrated Maisotsenko cycle cooling system is analyzed in subtropical climate conditions. Initially, an office building model is developed in TRNBuild to generate hourly dynamic year around air-conditioning loads. Afterwards a simulation model of the SDI-MC is developed for maximum cooling capacity of 24 kW in TRNSYS and validated with experimental data. Additionally, an effective control strategy is also implemented to efficiently meet the air-conditioning demand. The main performance parameters include COP, cooling capacity, useful energy gain, efficiency of solar water heating system, auxiliary energy share, and solar fraction of the system. The result revealed that the COP of the system ranges from 0.78 to 1.13 due to variation in system inlet humidity and temperature. Regeneration temperature requirement varies from 60 °C to 78 °C while cooling capacity of system ranges from 8 KW to 24 KW. Similarly, the results revealed an average annual efficiency of evacuated tube solar thermal collectors around 35.80% with total annual energy gain of 113.96 MJ. Furthermore, the maximum annual auxiliary energy share required for regeneration is 12.5%.

Numerical Analysis of dew point Indirect Evaporative Cooler

An indirect evaporative cooler that uses a Maisotsenko (M) Cycle has the potential to be a green and sustainable solution for managing a building’s cooling demand since it can attain sub-wet bulb temperature without humidification. This study presents the design and simulation analysis of a crossflow indirect evaporative cooler using the COMSOL Multiphysics software for various ambient conditions. The cooler’s performance was evaluated by varying the inlet air temperatures. The analysis was conducted using numerical simulations, and the outcomes were compared with experimental data. The simulation results demonstrated that the cooler could achieve significant temperature reductions at a minor energy consumption as compared to traditional air conditioning systems. This study delivers that this system reduces the temperature of inlet air up to 22°C as well as cooling capacity and coefficient of performance values are 3.699 kW and 27.40. Overall, the results demonstrate the potential of crossflow indirect evaporative coolers as an energy-efficient alternative to conventional air conditioning systems.

Performance characterization of M-cycle indirect evaporative cooler and heat recovery ventilator for commercial buildings – Experiments and model

Evaporative cooling systems in buildings can dramatically reduce greenhouse gas emissions due to their low energy consumption, lack of ecologically harmful refrigerants and their diverse applications. Indirect evaporative cooling (IEC) uses water in the secondary air stream to cool the primary air without adding humidity to the indoor environment. The Maisotsenko Cycle (M−Cycle) design of an IEC has the potential to approach dew-point on the primary air by pre-cooling the secondary air stream before extracting heat in cross-flow with the primary air. Separately, a variety of technologies exist for energy recovery in commercial buildings to pre-condition ventilation air. In this study a M−cycle heat and mass exchanger was used as a heat recovery ventilator (HRV) to recover energy from the exhaust air stream during winter and as an IEC during summer to cool the ventilation air. Experiments were performed by operating the full-size IEC/HRV system with a maximum air flow rate of 2210 m3/hr in conjunction with indoor and outdoor environmental chambers simulating respective environments. The experimental results showed HRV heating sensible effectiveness between 67 % and 63 % and IEC cooling total effectiveness between 81 % and 71 % with increasing air flow rates. A detailed numerical model was developed to predict the performance of the IEC/HRV over a large range of operating conditions. The IEC model simulates heat and mass transfer from water evaporation in the secondary air and potentially from condensation in the primary air during summer season operation. The HRV model simulates heat transfer and potentially mass transfer from secondary air condensation during winter season operation. The detailed physics-based model was compared with experimental data, and it predicted the performance with high accuracy for both summer and winter operating conditions. The average absolute errors for supply air temperature between the experimental results and model predictions were 0.2 °C in HRV winter mode and 1.0 °C in IEC summer mode. The validated IEC model was used to further explore the possibility of combined ventilation and passive space cooling without a supplemental air-conditioner. The analysis shows that utilizing IEC for summer operation offers high cooling COP and even the potential for passive space cooling, which is not possible with conventional energy recovery ventilators (ERV).

Исследование процесса испарения водно-этанолового раствора на супергидрофильной капиллярно-пористой поверхности в условиях вынужденной конвекции

In view of the continuous growth of global energy consumption, reduction of non-renewable energy sources, as well as increasing greenhouse gas emissions, it is necessary to introduce pro-mising methods to increase the importance of rational use of energy resources in the industrial, domestic and scientific and technical fields, which will reduce the amount of energy to provide the same level of energy supply of buildings or technological processes in production. This paper considers superhydrophilic capillary-porous surfaces capable of providing heat exchange through phase transition, which is of fundamental importance in evaporative radiators for space applications, heat pipes, as well as in the operation of cooling towers for electricity and heat production in centralized heat supply systems. The study of the heat exchange process with phase transition on the capillary-porous surface was carried out by conducting experiments on evaporation of water-ethanol mixture of different concentration under conditions of forced convection at diffe¬rent orientation of the modified surface in space. The results obtained in this work allow us to judge about the effectiveness of capillary-porous structures in heat exchangers operating on eva¬poration cycles and the Maisotsenko cycle, and are also applicable to further study of heat and mass transfer processes occurring on superhydrophilic capillary-porous surfaces.

Experimental analysis of dewpoint indirect evaporative cooler operating with solar panel

M-cycle (Maisotsenko cycle) based indirect evaporative cooling system can significantly enhance the natural ecosystem. The operating cost of dewpoint indirect evaporative cooler (Dewpoint-IEC) is low for space air cooling systems. Dewpoint-IEC is inexpensive, energy efficient, and ecological friendly. This study illustrates the experimental evaluation of Dewpoint-IEC working with varying operating conditions. The system designed for up to 1 Ton cooling capacity of the system which has coefficient of performance and energy efficiency ratio up to 6 and 20. The experimentation of Dewpoint-IEC is investigated in terms of the relative humidity and ambient temperature. The results indicate that the effectiveness of the Dewpoint-IEC system is increased with decrease the relative humidity and increase the ambient air temperature. The highest experimental values of wet bulb and dewpoint effectiveness of the system is 1.11 and 0.76. The maximum resulting values of EER, COP, and cooling capacity is 19, 6.1, and 3.3 kW, respectively. Based on experimental results, the system is a feasible option in hot summer days. Moreover, the power consumption of the Dewpoint-IEC is 70 W which can be achieved by combining the system with solar panels. So, current research also shows that Dewpoint-IEC integrated with solar panel recommends off-grid solution as well.

Performance prediction for modified design of dew point evaporative cooler for air cooling

ABSTRACT Traditional air conditioning systems use lot of energy; thus, dew point evaporative air-cooling systems could be a good alternative. Many experts studied the impact of constructional and operating characteristics on Maisotsenko cycle (M-cycle) to improve its performance. Cooler performance is influenced by the heat exchanger. Heat exchangers were constructed using flat and corrugated plates. The present study proposes the use of geometrically modified trapezoidal corrugated plates for counter flow heat exchanger, which consists of alternate air and water flow passageways. The numerical model is developed to predict the performance under variety of inlet air conditions and channel dimensions. In the standard range of incoming air properties such as relative humidity, the performance parameters assist in making cooler recommendations. Comparison and validation of simulation results are done with published experimental data for corrugated and trapezoidal corrugated plate heat exchangers. For trapezoidal corrugated plates, simulation findings revealed 10% increase in wet bulb efficiency and 7% increase in dew point efficiency over corrugated plates. The efficiency of wet bulb and dew point decreases as channel gap widens. For trapezoidal corrugated plates, the larger channel spacing minimises pressure drop.

Thermal performance analysis of a mixed-flow indirect evaporative cooler

This study experimentally investigates the performance of an indirect evaporative cooler based on the Maisotsenko cycle. It consists of a heat and mass exchanger (HMX) with a novel mixed-flow configuration. The de-sized cellulose rich cotton fabric is used as water-absorbing material, and aluminum sheets are used to fabricate the heat mass exchanger unit. The cooling performance indices of the system, namely dew point effectiveness (DPE), wet bulb effectiveness (WBE), and the coefficient of performance (COP), are evaluated at different inlet air temperatures (24 to 35 °C), volumetric flow rates (600 to 1050 m 3 /h), relative humidity (35 to 65%) and the extraction ratio (0.1 to 0.6). The results of the experimental study show that at a relative humidity of 35%, and inlet air temperature of 35 °C, the magnitude of the wet bulb and dew point effectiveness are highest and higher dew point and wet bulb effectiveness are observed at lower mass flow rates. The best cooling capacity and COP were obtained at an extraction ratio of 0.3 and are found to be highest at DBT of 35 °C. The maximum magnitude of CC was 2 kW with a COP of 16. Additionally, the convective heat transfer coefficient is calculated theoretically and compared with the experimental value. Further, a comparison of the obtained results for the mixed flow configuration considered in this study with those for other configurations reported in the literature reveals that the indirect evaporative cooler with mixed-flow configuration yields comparably good effectiveness. • Performance of indirect mixed flow evaporative cooler evaluated experimentally. • Effect of temperature, flow rate, relative humidity and extraction ratio are studied. • The optimum extraction ratio is observed to be 0.30. • Better performance is at higher inlet air temperature with lower humidity. • The maximum COP of 16 was observed at 35 °C with 35% relative humidity.

Thermodynamic and technoeconomic comparative justification of a waste heat recovery process with integration of multifluid and indirect evaporative cooler

For a well-developed, efficient and feasible system, it is necessary to produce power generation enormously with a reduction in harmful emissions like Carbon dioxide (CO2), Carbon monoxide (CO), Nitrogen (N), Nitrogen oxide (NOx), and Sulphur dioxide (SO2). Waste heat gases emit directly into an environment, it has many adverse effects on the environment including global warming, environmental pollution, and effect on human health as well. Researchers believe that a thermally efficient system could be achieved by converting waste heat gases into net power output. From this system, the efficiency obtained is 5% to 8% unable to meet the space and cost demands of this waste heat recovery (WHR) system. For waste heat recovery, the most typical cycles used for this are the Rankine cycle and Brayton cycle. Even though these are the best cycles but their efficiency is not as such maximum. By observing all these aspects, there is a different way of recovering waste heat and that is an indirect evaporative cooler (IDE). An indirect evaporative cooler is beneficial in terms of enormous power generation, getting maximum efficiency, low operating cost, and acquiring a sustainable system. The focus of current research was to recover industrial waste heat gases exhausted from SP boilers in the cement industry. ASPEN HYSYS software is used for generating a waste heat recovery model that further operates on the Maisotsenko cycle (M cycle). The topping cycle and bottoming cycle are used in this model. Both the working fluid air and binary mixture CO2-C7H8 operated in a model. By manipulating the model with working fluid air, this system generated a net power output of 68.53 MW with 35.44% thermal efficiency. Integrating the model with a binary mixture of CO2-C7H8 permits 48.59 MW output power with a 38.57% efficiency value. Comparison analysis is performed for extracting the best optimal parameters with extreme power generation and the greatest efficiency value. The industrial operating parameters of the Bestway cement industry operated in this developed model present 38.04 MW and 30.63 MW of power generation with 27.78% and 27.77% efficiency by executing both fluids air and CO2-C7H8 mixture. A techno-economic analysis (TEA) is performed for this entire waste heat recovery system which exhibits a cost of $30/MWh along 3 years payback period.

Experimental investigation of a hybrid configuration of solar thermal collectors and desiccant indirect evaporative cooling system

This paper presents the integrated performance of a solar-assisted desiccant dehumidifier along with Maisotsenko cycle (M-cycle) counter flow heat and mass exchanger. This system handles latent load and sensible load separately. The hybrid configuration of solar thermal collectors was analyzed for efficiency of solar collectors and solar fraction. High consumption of fossil fuels, which are already present in a limited amount, is also associated with environmental problems and climate change issues, as these increase the chances of global warming. These issues demand of us to shift towards renewable energy resources. Increase in world energy use results in a number of environmental problems, such as climate change, in addition to global warming and ozone depletion. In building services, HVAC systems are major concerns. To overcome the requirement, conventional air conditioning and vapor compression systems are mainly used for air conditioning, although these also have some environmental problems. Solar thermal applications in combination with other renewable-energy-dependent cooling practices have generated a huge interest towards sustainable solutions, keeping in view several techno-economical, environmental, and climatic advantages. The experimental investigation reveals that the maximum outlet temperature and efficiency of solar thermal collectors was 87°C and 56% respectively. The maximum cooling capacity of the system is evaluated at 4.6 kW.

THE INFLUENCE OF DIFFERENT FACTORS ON THE MAISOTSENKO CYCLE EFFECTIVENESS

An important problem in the heat industry is the significant cost of energy resources for air conditioning. Therefore, energy-efficient refrigeration systems based on renewable energy sources and evaporative air cooling, as well as air-conditioning systems according to the Maisotsenko cycle using psychrometric energy of the environment are of great importance. This paper presents the results of experimental and numerical research of the influence of various factors on the efficiency of indirect evaporative heat and mass transfer apparatus on the M-cycle on the basis of a new unit cell.
 An experimental stand of a heat and mass transfer apparatus with vertically arranged plate channels was developed for experimental research. Experimental studies of heat and mass transfer in the new unit cell were conducted in a wide range of Reynolds numbers 200…1200, temperature 16… 30 °С, relative humidity 30… 50 %. The calculated study was performed using a modified ε-NTU method. Studies have shown that the thermodynamic efficiency of a wet bulb thermometer at a Reynolds number below 500 exceeded one. According to the results of computational studies, the influence of cell length and surface intensification of dry channels on thermodynamic efficiency was determined. Shown the effect of changes in thermodynamic efficiency in the range of 86…94 % increase in efficiency by 1 % leads to an increase in cell length by 7 %. The value of the enhancement factor increases with increasing air flow regime, so when the heat and mass transfer surface area increases by 50 % and the Reynolds number 200, the thermodynamic efficiency increases by 14 %, and with the Reynolds number 800 – by 28 %. The dependence of the thermodynamic efficiency of the cells at the dew point on the relative humidity of the inlet air have a maximum, which with increasing Reynolds number shifts toward larger values of relative humidity.
 Unlike traditional air conditioning devices, the M-cycle heat and mass exchanger does not use a steam compression cycle, so energy costs are spent only on the operation of the fan to pump air, which is a more environmentally friendly and energy efficient way of air conditioning.

Performance evaluation of a solar powered solid desiccant evaporative cooling system with different recirculation air ratios

The evaporative cooling technology (ECT) has been regarded as an effective alternative to conventional vapour compression systems due to its energy saving and eco-friendly features. Moreover, when integrating with a solid desiccant unit, ECT can further extend its application in hot and humid environments. This paper proposed and evaluated a solar-assisted solid desiccant Maisotsenko cycle (M−cycle) based indirect evaporative cooling (IEC) system with different recirculation air ratios. Three other cooling systems, including stand-alone Direct Evaporative Cooling (DEC), stand-alone M−cycle IEC, and conventional solid desiccant evaporative cooling system (SD-DEC), were also simulated and compared with the proposed system under various ambient conditions. These systems were assessed in terms of supply air temperature, indoor relative humidity ratio, water consumption rate, coefficient of performance (COP) and solar fraction in this study. A case study of the proposed system was carried out under two typical Australian climates, Darwin and Melbourne. The results indicated that the solar-assisted solid desiccant cooling system integrated with M−cycle IEC had the best cooling performance compared with the other three systems, particularly in hot and humid areas. When increasing the recirculation air ratios from 0% to 60%, a maximum reduction of 23.1% and 41.9% could be observed in the system’s supply air temperature and humidity ratio, respectively. The highest COP was 0.89 when the inlet air temperature was 30 °C, and the COP value would vary as the inlet air temperature and humidity ratio increased. However, a higher water consumption rate was also observed, 31.36% to 57.94% more water would be consumed. This indicates that it requires selecting a proper recirculation air ratio for different climates to achieve the best performance.

Theoretical and numerical assessment of an enhanced Humidification-Dehumidification desalination system based on Indirect Evaporative cooling and Vapour Compression Refrigeration

In this work, a theoretical study and a numerical performance analysis of a novel Humidification-Dehumidification (HDH) desalination system, that simultaneously exploits an Indirect Evaporative Cooling (Maisotsenko cycle, IEC) device and a Vapour Compression Refrigeration cycle (VCR), are proposed. The IEC device is here employed as a very efficient saltwater evaporator-air humidifier, by an optimized mass exchange process between saltwater and working airstream. Both thermal exchanges of the VCR cycle are used: the hot coil pre-heats the inlet air to enhance the effectiveness of the evaporation process, while the cold one provides the cooling capacity to condense freshwater. The numerical model is based on data of actual commercial devices and considers their effective operational mode. The parametric analysis and the yearly simulations in different climatic areas show very promising results (GOR and RWA factor equal to 3.4 and 5.0∙106 in the best operative condition, equal to 3.2 and 4.1∙106 in the best climate situation) that lead to consider this technology as very competitive among HDH desalinations systems.