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The technical advantages of using evaporative cooling have drawn the attention of many researchers and industrialist in the world. Moreover, evaporative cooling techniques have been found to be most promising alternative to the HVAC methods in various building applications such as residential, commercial, agricultural, institutional and industrial buildings. An extensive literature review on latest developments of evaporative cooling that might deliver efficient cooling relief, reduce carbon emission and energy utilization in the buildings was carried out in the present paper. Also, the paper contains study of working principle of evaporative cooling, various types such as direct evaporative cooling (DEC), indirect evaporative cooling (IEC) and combined (IDEC) evaporative cooling system. Evaporative cooling makes the air cooler by increasing its humidity level. Thereby, it can be observed from the paper that the evaporative cooling provides a promising way to reduce the energy consumption in hot and arid climate conditions. Also, it seems to be an economical and environment friendly cooling compared to conventional HVAC methods which will ensure a substantial saving of fossil fuel (coal, petroleum and natural gas) utilization and reduction of carbon emission allied to the buildings.

Evaporative cooling is widely recognized as an energy efficient and environmentally-friendly air conditioning solution, and it has drawn a lot of market interest in recent years. However, this technology is accompanied by several challenges. For instance, insufficient evaporation due to poor and non-homogenous water distribution of the pre-cooling pad significantly reduces the cooling performance. The aim of the study is to develop a technique for numerical simulation of the distribution of a droplet liquid (water) on the mesh surface of an adiabatic cooler to improve the performance of air conditioning equipment. Modern computer-aided design (CAD)/computational fluid dynamics (CFD) programs were used to solve the issue. For the mathematical modelling of the medium motion, non-stationary Navier–Stokes equations were used. Parameters such as heat, mass transfer, and the efficiency of liquid droplet spraying were determined. The current study presents CAD modelling, conducted in SolidWorks platform, of water distribution on the adiabatic cooling pad’s mesh surface for improving air conditioning equipment performance. This study provides the methodology for computer modeling and numerical calculation of the parameters of adiabatic cooling, such as modelling of water atomization process. The results show that the use of additional metal mesh intended as cooling pads increases the mass transfer coefficient by Sh ≈ 15–40%; heat transfer coefficient Nu increases by ≈20–40%; and the atomization efficiency increases by ≈30–40%. The installation of metal pad mesh allows for equalized uniformity of the water distribution. The results imply that there are more opportunities to optimize the parameters of adiabatic cooling, which should be evaluated in further research on the subject.

A full-scale adobe-based evaporative cooler was built to be low-cost, and eco-friendly cooling storage for fruits and vegetables in vulnerable communities in developing countries. This paper evaluated the thermal behavior of the cooler, by measuring real-time conditions of temperature and humidity under different circumstances of water irrigation in 12 weeks during the dry season in Campo Grande, MS, Brazil. Disregarding other variables (solar radiance and wind), the cooler without irrigation had a similar temperature loss but lower efficiency due to intrinsic evaporative cooling behavior of adobe. Results show the system can contribute to decreasing internal temperature even without water input.

This study investigates the performance of a refrigeration unit by applying a spray evaporative cooling system to an air-cooled chiller. Experiments are conducted in the temperate monsoon climate region by combining the spray evaporative cooling system with the air-cooled chiller. Moreover, this study adopts a new gas–liquid two-phase swirl nozzle, which is independently developed and characterized by high atomization quality and low energy consumption. The experimental results show that the power of the compressor is reduced, while the COP (Coefficient of Performance) of the air-cooled chiller increases by 4%–8% after the intervention of the spray evaporative cooling system. The spray cooling system contributes to an electricity savings of 2.37%–13.53% in air-cooled chiller systems. If a more reasonable spray evaporative cooling mode is used, such as controlling the water flows according to the cooling capacity and arranging the nozzle positions and angles reasonably, the COP of the air-cooled unit will be further improved.

The prolonged manifestation of workers working in warm and moist atmospheric conditions results in their decreased labour work productivity, excessive sweating, and heat stress. Flexible and comfortable cooling vests are an appropriate solution to enhance labour work productivity. The study aims to determine the cooling efficiency of the material. A model is developed work on the principle of indirect evaporative cooling (IDEC) provides cooled air without adding humidity i.e. latent heat of vaporization is transferred to working air, which makes more doable over the direct evaporative cooling (DEC). The performance of three different hygroscopic materials is evaluated on the base of the following parameters including ambient air temperature, primary and secondary air temperature, and relative humidity. This study shows that aspen pads have proven to be the most appropriate hygroscopic material in achieving a minimum temperature difference of 7°𝐶 at ambient temperature and relative humidity.

In this paper, the cooling and freshwater generation performance of a novel hybrid configuration of a solid desiccant-based M-cycle cooling system (SDM) combined with a humidification–dehumidification (HDH) desalination unit is analysed and compared in three operational modes: ventilation, recirculation, and half recirculation. The HDH unit in this system recycles the moist waste air sourced from the M-cycle cooler and rotary desiccant wheel of the SDM system to enhance water production. A mathematical model was established and solved using TRNSYS and EES software. The results of this study indicate that the recirculation mode exhibited superior cooling performance compared to the other two modes, producing up to 7.91 kW of cooling load and maintaining a supply air temperature below 20.85 °C and humidity of 12.72 g/kg under various ambient conditions. All the operational modes showed similar water production rates of around 52.74 kg/h, 52.43 kg/h, and 52.14 kg/h for the recirculation, half-recirculation and ventilation modes, respectively, across a range of operating temperatures. The recirculation mode also exhibited a higher COP compared to the other modes, as the environmental temperature and relative humidity were above 35 °C and 50%. However, it should be noted that the implementation of the recirculation mode resulted in a higher water consumption rate, with a maximum value of 5.52 kg/h when the inlet air reached 45 °C, which partially offset the benefits of this mode.

Pervious concrete has good permeability and moisture adjustment properties due to its rich pore structure. It can not only reduce surface runoff by infiltration of rainfall, but also retain a certain amount of water inside, and then decrease the surface temperature via evaporation. In order to optimize the evaporative cooling performance of pervious concrete, this study introduces a modified method of incorporating superabsorbent zeolite produced from industrial wastes into pervious concrete as hygroscopic filler. The effects of zeolite dosages on the basic physical and mechanical properties of pervious concrete were analyzed, and then the evaporative cooling performance of zeolite-modified pervious concrete with the optimum replacement rate was studied. The results showed that the zeolite addition significantly reduced the density of pervious concrete, while having little impact on the permeability. The compressive and splitting tensile strength of pervious concrete increased first and then decreased as the replacement rate of zeolite powder increased, and the content of 15% zeolite powder and 20% zeolite aggregate was beneficial to improve the mechanical properties of pervious concrete. Contributing to the abundant micro-pores and higher specific surface area of zeolite particles, this could improve capillary water absorption and the water storage ability of pervious concrete. During the process of evaporation, the water absorption increment could effectively reduce the surface temperature by 5–8 °C, and maintain the evaporation cooling effect for 10–12 h.

Heat transfer measurements of flow boiling Carbon Dioxide (CO$_2$) in vertical upward direction have been carried out with a dedicated test facility at the European Organization for Nuclear Research (CERN). The investigation covers saturation temperatures within a range of $-25 \degree \textrm{C} \leq T_{\mathrm{sat}} +5 \degree \textrm{C}$, mass velocities from 100kg m$^{-2}$ s$^{-1}$ $\leq G \leq $ 450 kg m$^{-2}$ s$^{-1}$ and heat fluxes of 5.3 kW m$^{-2}$ and 11.4 kW m$^{-2}$. The experiments have been conducted in a vertical upward evaporator of 8 mm inner diameter and 8 m length and a database of more than 1900 measurements has been compiled within the present study. The heat transfer mechanism is dominated by the nucleate boiling contribution and dryout is observed as a function of saturation temperature, mass velocity and heat flux. A correlation is proposed to predict the dryout inception within the experimental range where the onset of dryout has been observed. The results suggest that most commonly used heat transfer prediction models underpredict the heat transfer mechanisms of CO$_2$. Moreover, the heat transfer coefficients of CO$_2$ increase in vertical upward direction, compared to the data of horizontal studies. For that reason, a vertical multiplier is suggested to capture the trends of vertical upflow with two existing prediction models.

The current standard of residential buildings is based on well-insulated and airtight construction as an effective way to reduce primary energy consumption. On the other hand, this intensifies the issue of the indoor air quality. In this paper, the applicability of a hybrid dehumidification/evaporative cooling system for the processing and supply of fresh air is evaluated. The proposed novel system employs cross-flow hollow-fiber membrane modules. To provide a better insight into this novel approach, the system’s performance is numerically investigated using a validated mathematical model. The proposed fresh air processing system provides supply air parameters in or close to the summer comfort range. The analyzed system is characterized by a high coefficient of performance (COP) of up to 33.2 at an outdoor air temperature in the range of 30 °C to 38 °C and a humidity ratio in the range of 8 g/kg to 14 g/kg. Moreover, a temperature difference of up to 9.7 °C can be obtained after the two-stage membrane processing and the mixing process.

Evaporative cooling is a promising concept to reduce the fuel cell system volume and mass significantly. This paper investigates the interactions between the fuel cell stack and the balance of plant in an evaporatively cooled polymer electrolyte fuel cell system (PEFCS). For this, a zero-dimensional PEFCS model, comprising the fuel cell stack, air compressor, charge air cooler, humidifier, hydrogen recirculation blower, condensing radiator and water separator has been developed and analyzed. Two evaporative cooling system architectures are compared to conventional, liquid cooling. Optimal operating conditions are determined by a numerical optimization of the net system power output. Main results show that evaporative cooling works on the system level over a wide range of operating conditions. The optimum system power and highest efficiencies are achieved at high temperatures (80–90 °C), low pressure (125–150 kPa) and a corresponding cathode stoichiometry between 1.5 and 3, allowing for a closed water loop at the same time. The air compressor shows an increased power demand, compared to conventional cooling and the exhaust gas condenser is identified as the one critical component for evaporative cooling. Its performance is key to an efficient operation and closed water loop at all ambient conditions., Journal of Power Sources, 542, ISSN:0378-7753, ISSN:1873-2755

The cooling of PV has been shown to increase electricity production. Among passive techniques, evaporative cooling has one of the greatest potentials. In this work, the efficiency and sustainability of this technique have been investigated for various climatic conditions. In-situ experiments were conducted to develop parametric models for PV cell temperatures and back surface convective heat transfer coefficient. Experiments have revealed an up to 20.1 °C lower peak PV temperature and up to 9.6% increased electric power. Year-round analysis was made for eight cities to determine the required roof size to capture precipitation and the volume of rainwater storage for sustainable evaporative cooling. The study shows that sustainable PV evaporative cooling is possible in cities with temperate and continental climates, where 1–3 m$^2$ of roof area and 50–150 l of rainwater storage are needed for 1 m$^2$ of PV. The annual electricity production can increase by 5.9–9.4 kWh/m$^2$a, which is a 3.6–4.6% increase. In the semi-arid climate of Lampedusa, a roof above 4 m$^2$ and a storage of up to 500 l per m$^2$ of PV are required. In the desert climate of Almeria and Athens, sustainable evaporative cooling is not feasible.

The applicability of a hollow fiber membrane evaporative cooler in hot–dry regions was investigated by experimental studies. To better understand the actual operating environment of the hollow fiber membrane evaporative cooler, the outdoor air design conditions for summer air conditioning in five cities were simulated by an enthalpy difference laboratory. Subsequently, the effects of water and air flow rates on outlet air parameters and performance parameters were investigated by setting-up a hollow fiber membrane evaporative cooling experimental rig. It was found that the hollow fiber membrane evaporative cooler has good application prospects in hot–dry regions such as Lanzhou, Xi’an, Yinchuan, Urumqi, and Karamay. Among them, the hollow fiber membrane evaporative cooler has higher applicability in regions with higher air temperatures and lower humidity such as Urumqi and Karamay. The results indicate that the air outlet temperature and relative humidity ranged from 26.5 °C to 30.8 °C and 63.5% to 82.8%, respectively. The outlet air temperature and relative humidity of the HFMEC can meet the thermal comfort requirements of hot–dry regions in the summer at an appropriate air flow rate. The maximum air temperature drop, wet-bulb efficiency, cooling capacity, and COP were 7.5 °C, 62.9%, 396.4 W, and 4.81, respectively. In addition, the effect of the air flow rate on the performance parameters was more significant than that of the water flow rate.

Orientador:Irenilza de Alencar Naas Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola Resumo: Durante o período de lactação, as fêmeas suínas devem consumir níveis adequados de ração para mantença e produção de leite. O baixo consumo resulta em mobilização das reservas corporais, condição corporal inadequada, falhas reprodutivas e redução no tempo de vida útil das fêmeas no rebanho, principalmente nas condições de temperatura ambiente elevada. A hipótese desse trabalho foi que, o sistema de resfriamento evaporativo associado ao uso da dieta com balanço eletrolítico, pode favorecer o conforto térmico das fêmeas suínas em lactação, durante a exposição ao calor ambiente excessivo e, consequentemente, minimizar os efeitos prejudiciais do estresse calórico sobre o desempenho. O experimento foi realizado em uma granja comercial com 72 fêmeas suínas da genética DanBred® e objetivou avaliar os efeitos do sistema de ventilação e da dieta sobre o desempenho e os parâmetros de termorregulação de porcas lactantes durante o verão. O delineamento experimental foi blocos ao acaso com quatro tratamentos em disposição fatorial 2 x 2 e 18 repetições por tratamento. Os tratamentos foram dois sistemas de ventilação (ventilação natural ou resfriamento evaporativo) e duas dietas (balanço eletrolítico natural de 175 mEq kg-1 ou balanço eletrolítico ajustado de 275 mEq kg-1). Os resultados foram submetidos à análise de variância utilizando o programa Minitab®15.1. Foram registrados os dados de temperatura ambiente, umidade relativa do ar, velocidade do ar, iluminância e características físico-químicas da água. Foram calculados o índice de conforto térmico e o retorno econômico do investimento. Foram monitorados os dados fisiológicos (frequência respiratória, temperatura retal, temperatura superficial, concentração de sódio, potássio e cloretos na urina e concentração de cortisol salivar) e de desempenho das porcas (consumo de ração, condição corporal e intervalo desmame-estro) e dos leitões. As variáveis de termorregulação e os resultados de desempenho das porcas e dos leitões também foram avaliados de acordo com a ordem de parto. Não houve efeito significativo do sistema de ventilação e da dieta sobre o consumo de ração, a condição corporal e o intervalo desmame-estro das porcas. O sistema de resfriamento evaporativo proporcionou redução (P

Buildings are known to be responsible for about a third of energy consumption in developed countries. This situation, together with the fact that the existing building stock is being renovated at a very slow pace, makes it crucial to focus on the energy retrofitting of buildings as the only way to reduce their contribution to these energy consumptions and the consequences derived from them in terms of pollution and climate change. The same level of insulation and the same type of windows is usually proposed for all dwellings in a building block. This article shows that since the improvements required by each dwelling in the same block are different, the proposed solution must also be different. The methodology is proposed for a practical case consisting of an apartment block in C&aacute, diz, a demonstration building of the European RECO2ST project. To achieve the optimum solution for each case, a multi-objective optimization problem is solved: to minimize the annual heating demand of the building and the standard deviation of the annual demand of the different dwellings. Thanks to the use of the proposed methodology, it is possible to bring the building to a Nearly Zero Energy Building (NZEB) level, while avoiding excessive insulation that causes overheating in summer.

This chapter analyses the potential combination of ventilative cooling solutions with direct evaporative cooling (DEC) systems. The focus is on passive downdraught evaporative cooling (PDEC) towers, whose performance is described based on the analysis of monitored results. The main design aspects of PDEC towers are explained, including basic relationships and support tools for system optimization. A series of case studies is reported, illustrating different integration strategies and providing a series of examples for designers. Finally, a simulation-based approach to analysing the local potential of PDEC to reduce thermal discomfort in naturally ventilated buildings is introduced, providing a method by which DEC systems can be integrated in building projects from the early-design phases.

Lithium-ion (Li-ion) batteries play an essential role in our daily lives and are considered the main power source in electric vehicles. The process of charging and discharging the battery continuously drives to a significant amount of heat generation which results in temperature differences, non-uniformity, and thermal runaway. An effective battery thermal management strategy (BTMS) is required to maintain battery temperature in the optimal range and thus ensure high performance, safety, and longevity of lithium-ion batteries. This study proposes a unique battery thermal management depends on using the jute as a plant-based, cheap, environmental, economic, renewable and lightweight fiber. Thorough experiments are carried out on a 50 Ah prismatic high-energy battery cell with an integrated evaporative cooling system and its effects on battery thermal behavior are studied. The maximum temperature, temperature difference, and temperature uniformity on the cell surface are compared under different conditions, which include natural convection cooling, forced air cooling, and evaporative cooling. The results confirm that using the jute for the proposed BTMS improves the efficiency of air cooling with a better temperature uniformity as well as reduced equipment and weight. This article represents the first attempt to analyze the performance of jute fiber as a cooling medium in BTMS. Thus, it contributes to improving the battery thermal management system air-based.

Direct evaporative cooling is widely known to be an energy efficient air-conditioning option for arid and semi-arid climates. However, care must be taken on humidity ranges achieved indoors. Existing literature presents several options for integrating evaporative cooling within buildings for passive cooling applications. This work aims at expanding the current knowledge by focusing on the use of water-filled hollow bricks to implement evaporative cooling of air in contact with the brick’s surfaces. A prototype is built and experimentally characterized under controlled air velocity, air temperature and relative humidity conditions. Results on the psychrometric conditions achieved under different geometric arrangements (i.e., with one, two or three rows of four bricks each) are presented and discussed. Insights on likely building integration of the system for passive cooling purposes in farms and agriculture applications are eventually given.

The purpose of this study is to evaluate the potential for using the spaces integrating the roads and sidewalks in the street canyon as human-centered spaces, and to investigate more appropriate measures to improve the thermal environment for pedestrians and visitors in these spaces. Based on the spatial distribution of SET* throughout the day, as possible human-centered street space uses, north–south streets with restricted widths and south sidewalks on east–west streets are candidates. Spatiotemporal distributions of SET* were calculated when water was sprinkled on the road surface in the street canyon and when water surface, sunshade, and trees were introduced in the street canyon. Assuming people walk or stay on the water surface, the MRT decreases, causing SET* to be below 31.5 °C at any time, so if a continuous supply of water is guaranteed and people can approach the water surface, the water surface can be expected to have a significant impact anywhere at any time. On the east–west street, shading by sunshades and trees occurs along the lanes at any time, allowing pedestrians moving through the lanes to pass through the shaded areas on a periodic cycle. On north–south street, the time required for the countermeasures is limited to around noon, so the measure is effective even if the shade does not occur in the target lanes only around noon.

Preservation of potatoes in a controlled cool environment (i.e., in cold storage) consumes a substantial amount of energy. The specific energy consumption in Indian cold storage has been estimated to be between 9 and 26 kWh/ton/year. In this article, the potential for minimizing the energy consumption in the refrigeration process of cold storage through passive cooling concepts (i.e., roof evaporative cooling and the earth integration of the storage building) was explored. These passive concepts of cooling have shown significant potential for lowering the cooling loads and the energy consumption in different types of buildings. Therefore, a feasibility analysis for a potato storage building, considering the effect of the passive cooling concepts, was conducted for three different climatic conditions (i.e., hot–dry, warm–humid, and composite) in India. The energy saving potentials in the cold storage were assessed by quantifying the thermal energy exchange between the indoor and outdoor environments using the modified admittance method. The effect of heat transfer through the building envelope on total energy consumption was estimated for the building having various sunken volumes (buried depths) without and with roof evaporative cooling. Further, the economic feasibility of adopting passive concepts was assessed in terms of life cycle saving compared to the base case. Results indicate that earth coupling without and with evaporative cooling has substantial potential to reduce the cooling load and can produce significant savings.

The phenomenon of urban heat islands is mainly caused by the increase of artificially hardened surfaces in cities, and it can be alleviated by using permeable pavements to dissipate latent heat. There are many disagreements on the cooling effect of permeable pavements, and at present, it still needs more tests and modeling to prove this view. This paper proposes a 3-D transient model based on the heat transfer theory of porous media to accurately evaluate the cooling performance of permeable pavements. The influences of surface thermal parameters, storage depths, and spraying schemes on the cooling performance of permeable pavements are analyzed. The results show that compared with the peak temperature in the dry state, saturated permeable pavements can be significantly reduced. It is also found that the reflectivity of permeable pavements is positively correlated with the magnitude of temperature reduction and it has the most significant effect on the surface temperature among the discussed thermal parameters. A water storage layer with a thickness of 15 cm is recommended to balance economic costs and the cooling performance of permeable pavements. Based on the calculation results of the temperature reduction and cooling time, the optimal quantity of water spray is given innovatively. The proposed model can help improve the material components, structures, and maintenance methods of permeable pavements.

The evaporation of water droplets placed on heated hydrophilic, hydrophobic, and superhydrophobic sub- strates is numerically investigated. Simplified analytical models for droplet evaporation only include va- por diffusion transport in the surrounding gas domain and assume an isothermal droplet interface at the substrate temperature. The comprehensive model developed in this study accounts for all of the per- tinent transport mechanisms. The interface is cooled via absorption of latent heat during evaporation, and the saturated vapor concentration is coupled to local temperature at the droplet interface. Conjugate heat and mass transfer are solved throughout the system using temperature-dependent physical prop- erties. Buoyancy-driven convective flows (induced by both species concentration and temperature gradi- ents) in the droplet and gas domains are also simulated. The evaporation rates predicted as a function of the substrate wettability (contact angle from 10 °to 160 °) and substrate temperature (40 °C to 65.4 °C) are validated against experiments from the literature. The modeling approach yields quantitative insights into the influence of these transport mechanisms on the evaporation characteristics. As substrate tem- perature is increased, the buoyancy-induced convection significantly increases the evaporation rate by up to ~60% on the hottest substrate compared to the diffusion-based model, by enhancing vapor transport in the gas domain. Simultaneously, the liquid-gas interface is increasingly cooled by evaporation, lead- ing to a large temperature drop across the droplet height, ~18 °C for a 3 μL droplet evaporating on the superhydrophobic substrate at 60 °C. This significantly alters the distribution of the vapor fraction and evaporation flux along the interface and suppresses the evaporation rate (by ~53%). When both factors are considered together, the net effect (namely, enhancement or suppression) on the evaporation rate is dependent on the competition between the buoyancy-induced convection and evaporative cooling. On hydrophilic substrates, the evaporative cooling effect is weak because the flat droplet shape results in a relatively small temperature difference between the interface and the heated substrate; upward gas-phase natural convection is dominant and enhances evaporation. On the hydrophobic substrate, these respective suppression and enhancement effects counterbalance each other. On the superhydrophobic substrate, the effect of evaporative cooling is further amplified by the large thermal resistance between the substrate and interface, dominating the transport process and entirely suppressing the influence of upward natural convection in the gas phase.

The growing needs for fruit and vegetable production, together with the current climate change situation, make agriculture under plastic and greenhouse cooling indispensable. The most commonly used approaches are natural ventilation, shading and fan-pad systems. To foster a climate that allows forplant production under cover in extreme conditions, a novel fan-pad system has been devised that incorporates a pre-chamber and an air distribution system using air ducts running alongside the crop rows. The system has been tested in a greenhouse in Almeria (Spain) during the daytime in August, when the weather was hotter. Tests were also carried out in combination with natural ventilation and shading. The results indicate that the fan-pad system was efficient under extreme weather conditions and that it avoided creating horizontal thermal gradients. By determining the theoretical value of the air temperature leaving the pad, we were able to estimate the evaporative cooling potential of the fan-pad system as a function of the outdoor climate. Under extreme conditions, the fan-pad system&rsquo, s efficiency decreased along with increased air temperature and, above all, the increased relative humidity of the outside air. When the outdoor climate is warm and humid, natural ventilation may be the most efficient temperature control method. If the outdoor climate is warm and dry, the evaporative pad is more effective, especially when combined with shading.

Journal of Research and Applications in Mechanical Engineering (JRAME), 8, 2, 114-134

A significant portion of global energy consumption is due to energy consumption in the buildings. Heating, cooling, and air conditioning systems have the largest share in this energy consumption. Evaporative cooling systems, which have the advantage of being economical, zero pollution, and easy maintenance are preferred to reduce energy consumption in buildings. These systems are used in many areas such as greenhouses, broiler houses, and warehouses. In this study, analyzes of exergy, sustainability, and cooling efficiency in four different situations of a ground source direct evaporative cooling system were made. The system was studied in four different cases. While the highest exergy efficiency was obtained in case 3 with 20.83%, the exergy efficiencies in other cases were obtained as 16.83%, 17.49%, and 18.36%, respectively. In addition, the highest specific exergy loss was determined as 100.51 J/kg in case 2, while it was calculated as 73.08 J/kg, 80.23 J/kg, and 73.05 J/kg for the other cases, respectively. It is seen that the sustainability values are in parallel with the exergy efficiency when the evaporative cooling system is examined for four different cases. The sustainability values were determined as 1.20 for case 1, 1.21 for case 2, 1.26 for case 3, and 1.22 for case 4. It is determined that the exergy efficiency gives precise information about the usability and sustainability of the system when these situations are evaluated. The exergetic improvement potential (EIP) was determined as 0.061 for case 1, 0.082 for case 2, 0.063 for case 3, and 0.059 for case 4, respectively. Although the highest exergy efficiency is obtained in case 3, it has a higher recovery potential than case 1 and case 4. In addition, cooling efficiencies for four different cases were obtained as 33.70%, 34.81%, 41.69%, and 36.95%, respectively. The temperature differences between the room and ambient temperatures were determined as 1.45 °C, 1.21 °C, 1.6 °C, and 1.48 °C for each case, respectively.

A test facility to investigate flow pattern transitions of vertical two-phase flow of CO2 has been built within the scope of the high-luminosity detector upgrades at the European Organization for Nuclear Research (CERN). Adiabatic flow pattern observations for both vertical up- and downflow are recorded with high-speed imaging in tubes of 8 mm inner diameter, with saturation temperatures in the range of − 25 ° C to + 5 ° C and mass velocities ranging from 100 kg m − 2 s − 1 to 450 kg m − 2 s − 1 . A database of 431 flow pattern observations in upward and 123 in downward direction has been compiled. The recorded data have been analyzed with machine learning techniques and a previously trained Frame- and Flow-Regime-Classifier is used for the flow regime classification. The observed two-phase flow pattern transitions did not match the transition lines of existing flow pattern maps. As a consequence, new transition lines for the bubbly-to-slug, slug-to-churn and churn-to-annular transitions have been developed for both vertical upflow and downflow respectively and condensed into new flow pattern maps. It is concluded, that the flow regime transitions are strongly depended on vapour quality, mass velocity, the flow direction and the fluid properties. Compared to horizontal flow, a dryout region is not observed and the liquid film of the annular flow regime dries out symmetrically at vapour qualities close to x = 1 .

Currently, a majority of global residential air-conditioning requirements are met using cooling systems based on the vapor compression cycle (VCC). To meet the future demand for space cooling and to reduce the corresponding environmental impact, there is a need for alternative cooling systems which require less resources and exhibit a higher coefficient of performance (COP). One of proposed alternatives is called the hybrid evaporative-vapor compression (HEVC) cycle, which utilizes adiabatic latent cooling in combination with the VCC. In this paper, we conducted a feasibility analysis of a HEVC system by comparing its performance to that of VCC for various global climates. To accomplish this, we developed and validated models to simulate the performance of residential VCC and HEVC systems. ASHRAE weather data and design conditions were then used to compare the performance of the two systems. In general, HEVC systems are best suited for hot arid climates with energy reduction greater than 20%. Conversely, humid climates are not suitable for HEVC adoption due to degraded performance of evaporative coolers in these climates. In addition to comparing the energy savings from HEVC systems, it is also critical to analyze their water consumption. Generally, climates that benefit the most from HEVC technology tend to also experience water scarcity issues. Thus, both the energy savings and water consumption of HEVC systems must be analyzed to guide the discussion on their adoption.

A combined circulation system of spray evaporative cooling and air cooling (CCSSECAC) is a way to enhance the cooling performance of an air-cooled electric machine while maintaining its existing structure. Based on a traditional air-cooled machine, when the discrete evaporative cooling medium particles are scattered into the airflow, they will reach the heat source with the air circulation. The cooling capacity of the cooling system is enhanced simultaneously through the phase transition and convection heat transfer. Ultrasonic atomization is a simple way to produce tiny droplets and a good way to improve the performance of CCSSECAC. To verify the effectiveness of such a system, a principle test model was built and a multi-operational condition experiment was carried out as an exploratory study. The experimental results showed that the new cooling system was feasible for horizontal machines, and the stator coil temperature was significantly reduced compared with the air-cooled mode.

This paper proposes a novel radiative passive system for hot and dry climates to improve outdoor thermal comfort. The solution consists in a curtain, characterized by two different finishing surfaces, one is waterproof and the other one is absorbent, immersed in a water tank by means of a mechanized system and subsequently used as a radiant surface with reduced temperature thanks to evaporative cooling effect. The effectiveness of the proposed system is verified by means of CFD simulations carried out on a sample application in outdoor space and supported by experimental measurements carried out on a small sample of curtain. The results showed that the proposed system can reduce the operative temperature up to 6°C with respect to the testing conditions (air temperature of 28.5°C and relative humidity of 50.5%) ensuring higher comfort levels and a limited water consumption to keep the curtain constantly wet (25 l/h for 130m 2 of wet curtain).

Energy consumption in buildings due to heating, cooling and air conditioning (HVAC) systems has a steadily growing trend as a consequence of enhanced indoor thermal comfort conditions. The role of cooling in HVAC oriented energy consumption is remarkable especially in regions with extreme climatic conditions such as Africa and Middle East. In hot and arid climates, cooling demand is usually met by cost-effective evaporative cooling solutions. However, in hot and humid climates, evaporative cooling systems are not capable of providing cooling as the outdoor air is already almost saturated in most cases. Therefore in this research, a novel desiccant-based evaporative cooling system is presented. For different values of inlet supply air temperature and relative humidity provided by a standard environmental chamber, temperature and relative humidity values are measured experimentally at the inlet and outlet of dehumidification and humidification unit, respectively. Since the main purpose of the system developed is to provide cost-effective thermal comfort conditions especially in humid climates, dehumidification effectiveness is calculated for each case tested. The results indicate that the system provides attractive findings for temperate and humid climatic conditions, where stand-alone evaporative cooling systems are inconclusive. For a case of average inlet relative humidity of 94.7% and average inlet air temperature of 38.6 °C, the average outlet relative humidity and air temperature are determined to be 65.5% and 33.3 °C, respectively. An average of 5.3 °C reduction is achieved in supply air temperature as well as an average of 63.7% dehumidification effectiveness which is attractive and promising. © 2016 Elsevier B.V.

Significance Climate change—especially accelerated warming and drying—threatens to increase extinction risk, yet there is little evidence that physiological limitations have contributed to species declines. This study links species-specific water requirements for cooling body temperature to the collapse of a Mojave Desert bird community over the past century from climate change. Species occupying the hottest, driest sites were less likely to persist. Birds with the greatest water requirements for cooling their body temperature experienced the largest declines. Large-bodied carnivores and insectivores were especially vulnerable to cooling costs because they obtain water primarily from their food. Climate warming increases the evaporative cooling demand for birds, which will affect geographic patterns in body size and future extinction risk., Climate change threatens global biodiversity by increasing extinction risk, yet few studies have uncovered a physiological basis of climate-driven species declines. Maintaining a stable body temperature is a fundamental requirement for homeothermic animals, and water is a vital resource that facilitates thermoregulation through evaporative cooling, especially in hot environments. Here, we explore the potential for thermoregulatory costs to underlie the community collapse of birds in the Mojave Desert over the past century in response to climate change. The probability of persistence was lowest for species occupying the warmest and driest sites, which imposed the greatest cooling costs. We developed a general model of heat flux to evaluate whether water requirements for evaporative cooling contributed to species’ declines by simulating thermoregulatory costs in the Mojave Desert for 50 bird species representing the range of observed declines. Bird species’ declines were positively associated with climate-driven increases in water requirements for evaporative cooling and exacerbated by large body size, especially for species with animal-based diets. Species exhibiting reductions in body size across their range saved up to 14% in cooling costs and experienced less decline than species without size reductions, suggesting total cooling costs as a mechanism underlying Bergmann’s rule. Reductions in body size, however, are unlikely to offset the 50 to 78% increase in cooling costs threatening desert birds from future climate change. As climate change spreads warm, dry conditions across the planet, water requirements are increasingly likely to drive population declines, providing a physiological basis for climate-driven extinctions.

This paper evaluates two roof pond configurations combined with a water-to-air heat exchanger (WAHE). Test cells of 1.35 m × 1.35 m x 1.35 m with the same thermal properties, except for the roofs, are built in a hot-dry climate with mild winters. They are connected with a WAHE placed inside the roof pond's water by a pipe through which the indoor air is re-circulated. The first roof consists of a 0.35 m deep water pond covered with a floating polystyrene insulation 0.03 m thick, and a spray system located 0.5 m above it that operates at night. The second roof is covered with an aluminum plate separated by a 0.10 m air gap above a 0.25 m deep water pond. We ran multiple series and compared the results to a control cell that had a California energy code compliant insulated roof. Predictive equations are developed to dimension the WAHE system. Results demonstrate that the cells with roof ponds have better cooling performance than the code compliant control cell. The best performance is obtained in the cell with the WAHE operating continuously. In this case, the indoor temperature stayed below 24 °C even with ambient temperatures above 35 °C.

This paper discusses the design, construction and assessment of a modified, cost-effective evaporative cooling facility for the preservation of fresh fruits and vegetables for use by the average Nigerian farmer, agri-business entrepreneur or layman. The designed facility makes use of cooling pads and constantly running water. It was designed and constructed with carefully selected inexpensive and readily available materials. The structure was made of internally and externally cemented sliced cement blocks. River sand was used as the cooling pad and product storage values were compared with those stored under ambient air conditions. Tomatoes were the test crop used to assess the structure’s cooling efficiency. Findings showed that a cooling chamber filled with river sand as a cooling pad with constant application of water performed better in the storage of tomato fruit (Lycopersicum esculentum) than fruits stored under ambient conditions. It was therefore recommended that tomatoes should be stored under temperatures between 22-230C to increase shelf life and reduce spoilage. There is a need for more work to be done in terms of introduction of fans, other cooling pad materials and constant water to enhance the structure’s performance.

The hot humid tropics is a region of significant rainfall and abundant solar energy that facilitate high evapotranspiration rates and a rich biodiversity. The region is characterized by its forest landcover that influences the climate by using and dissipating the solar energy and interacting with the water cycle. Many areas of the hot humid tropics are losing this capacity to regulate their typical hydrologic fluxes and surface energy balances due to the extreme land use and land cover change caused by urbanization, thus becoming environments with increased temperatures, disrupted water cycle, degraded water quality and reduced biodiversity. Green infrastructure is a nature-based solution to mitigate these impacts of urbanization. However, physical limitations of the urban context as well as technical and financial barriers impede to just rely on green infrastructure strategies. Alternatively, the built surfaces of the urban landcover can be adapted to harness the abundant precipitation of the humid tropics for restoring the water energy balances distorted by urban development. One way is the use of rainwater for surface evaporative cooling of conventional buildings, to reduce their heat gains and indoor and outdoor heat transfers from the building envelope while contributing to substantial reduction of stormwater runoff. This research explores the potential of rainwater use for building surface evaporative cooling (BSEC) from a holistic perspective, integrating criteria from fields such as architecture, building physics, urban climatology and urban hydrology, to verify its relevance as a common strategy for dealing with urban problems in the hot humid tropics such as overheating, flooding and water pollution. Weather influences, hygrothermal performance, effects of radiation and humidity, evaporation rates and water consumption by BSEC in relation to low-rise buildings are measured quantitatively through field experiment, hygrothermal and CFD simulations and water budgeting to determine benefits in thermal performance and the potential demand for rainwater. The results indicate that, in hot humid tropical environments, the cooling effect of rainfall is not negligible and is produced just by little portion of the precipitation intercepted by the buildings. Also, BSEC strategies effectively diminish urban overheating, generate a significant demand for the precipitation surplus and contribute to considerable runoff reductions. Additionally, the higher humidity from BSEC does not increase thermal discomfort, but the lower surface temperatures are rarely sufficient to achieve outdoor comfortable conditions.

Gas turbine inlet air-cooling (TIAC) is an established technology for augmenting gas turbine output and efficiency, especially in hot regions. TIAC using evaporative cooling is suitable for hot, dry regions; however, the cooling is limited by the ambient wet-bulb temperature. This study investigates two-stage evaporative TIAC under the harsh weather of Riyadh city. The two-stage evaporative TIAC system consists of indirect and direct evaporative stages. In the indirect stage, air is precooled using water cooled in a cooling tower. In the direct stage, adiabatic saturation cools the air. This investigation was conducted for the GE 7001EA gas turbine model. Thermoflex software was used to simulate the GE 7001EA gas turbine using different TIAC systems including evaporative, two-stage evaporative, hybrid absorption refrigeration evaporative and hybrid vapor-compression refrigeration evaporative cooling systems. Comparisons of different performance parameters of gas turbines were conducted. The added annual profit and payback period were estimated for different TIAC systems.

The article deals with the study on the efficiency of units for porous ammonium nitrate production. The ways which increase the effective implementation of energy resources are determined by including the ejector recycling module, heat and mass exchangers that utilize principles of regenerative indirect evaporative cooling, and the sub-atmospheric inverse Brayton cycle. Mixed exergy analysis evaluates all flows of the system contour as those of the same value. The target parameter for determining the efficiency of both systems is the ratio of the unit&rsquo, s productivity to the exergy expenditures to produce the unit mass of the product. As a result, it is found that the mentioned devices and units enable to increase the efficiency of the basic scheme by 87%.

Regions that experience ambient temperatures rising during hot seasons have significant losses and impacts on both output power and efficiency of the gas turbine. When the ambient temperature increases, the air mass flow rate decreases, and hence leads to reduce the gas turbine produced power. Ambient air can be cooled by using either evaporative cooler or absorption chiller. Currently, the performance was simulated thermodynamically for a natural gas operated gas turbine. The performance was tested for the base case without any turbine inlet cooling (TIC) systems and compared with the performance for both evaporative cooler and absorption chiller separately in terms of output power, thermal efficiency, heat rate, specific fuel consumption, consumed fuel mass flow rate, and economics. Results showed that at air ambient temperature equals to 37 °C and after deducting all the associated auxiliaries power consumption for both evaporative cooler and absorption chiller, the absorption chiller with regenerator can achieve an augmentation of 25.47% in power and 33.66% in efficiency which provides a saving in average power price about 13%, while the evaporative cooler provides only an increase of 5.56% in power and 1.55% in efficiency, and a saving of 3% in average power price.

The paper presents an investigation into the energy performance of a novel irregular heat and mass exchanger for dew point cooling which, compared to the existing flat-plate heat exchangers, removed the use of the channel supporting guides and implemented the corrugated heat transfer surface, thus expecting to achieve the reduced air flow resistance, increased heat transfer area, and improved energy efficiency (i.e. Coefficient of Performance (COP)) of the air cooling process. CFD simulation was carried out to determine the flow resistance (K) factors of various elements within the dry and wet channels of the exchanger, while the ‘finite-element’ based ‘Newton-iteration’ numerical simulation was undertaken to investigate its cooling capacity, cooling effectiveness and COP at various geometrical and operational conditions. Compared to the existing flat-plate heat and mass exchangers with the same geometrical dimensions and operational conditions, the new irregular exchanger could achieve 32.9%–37% higher cooling capacity, dew-point and wet-bulb effectiveness, 29.7%–33.3% higher COP, and 55.8%–56.2% lower pressure drop. While undertaking dew point air cooling, the irregular heat and mass exchanger had the optimum air velocity of 1 m/s within the flow channels and working-to-intake air ratio of 0.3, which allowed the highest cooling capacity and COP to be achieved. In terms of the exchanger dimensions, the optimum height of the channel was 5 mm while its length was in the range 1–2 m. Overall, the proposed irregular heat and mass exchanger could lead to significant enhanced energy performance compared to the existing flat-plate dew point cooling heat exchanger of the same geometrical dimensions. To achieve the same amount cooling output, the irregular heat and mass exchanger had the reduced size and cost against the flat-plate ones.

For the thin metal foil cooling that is not very intense, the temperature change in thickness can be neglected when the Biot number Bi

International audience; The thermal behavior of 12 standard and cool pavement structures (asphalt, granite, stabilized sand, cobblestones, reflective paints, pervious concretes, dry grass, etc.) coupled with pavement-watering is studied in the lab under heatwave like conditions. Watering is fine-tuned for each structure to maximize cooling and minimize water consumption using two linear cooling regimes, before deployment in the field. The surface heat budget is closely studied and the partitioning of irradiance and net radiation into conductive, convective, radiative and cooling flux at surface is analyzed for each structure. Energy partitioning, surface temperature increase and optimal watering rates all exhibit good correlation with overall surface absorptivity. The transmitted flux at varying depths is also characterized using a transmission index that includes surface absorptivity and apparent conductivity of the traversed layers. Results of this study intend to improve our understanding of the energy balance of cool pavements compared to traditional ones under given weather conditions, as well as that of processes involved in the optimization of their evaporative cooling versus watering rate. Benefits of each pavement, efficiency of the method, limitations of the protocol and its potential transposition to the field are all discussed in this contribution.

In a pitched ventilated roof, an air stream enters a cavity below the roof surface through openings at the level of the gutters, then it flows up along the roof and is finally discharged through openings along the ridge. The heat brought by the absorbed solar radiation is removed thanks to the flow established by natural ventilation, but only in part because the flow is relatively weak and unstable. As shown in previous work, a stronger and more regular air flow can be ensured by forced ventilation, extracting the air by means of a fan after it has been collected along the ridge by a properly designed manifold. This setup can be further enhanced by humidifying and saturating the air as it enters the cavity, thus significantly lowering the downstream air temperature. An indirect evaporative cooling system is thus obtained, by which an inhabited space under the roof can be cooled through the ceiling while remaining sealed and unaffected by the evaporative process. In this work, the setup is analyzed by a mathematical model and the concept tested by means of a small scale test bed, showing that it can be used to counter extremely hot ambient conditions with a relatively low consumption of liquid water and almost negligible energy need.

Mist cooling is a widely known and applied heat mitigation technology, especially in urban settings. Despite this, conceiving the right installation is no trivial matter as scattered and unstandardized is the knowledge on the multiple interrelations with the local microclimate. This paper investigates how the cooling efficiency of a dry mist system depends on the local meteorological trends. An experimental system of 24 overhead nozzles constantly operating at 0.7 MPa, was installed in Italy and monitored for a week in summertime. Temperature and relative humidity underneath the mist were mapped in five locations with a time step of 10 s, together with the main meteorological parameters, measured at an undisturbed location, for reference. Cooling and humidification capacity were characterized as probability density, key summary statistics and relevant confidence intervals with minimal redundancy and minimal distortion. A supervised learning algorithm was used to disclose the sensitivity of the recorded temperature drop to the contextual microclimatic evolution. It was demonstrated that the cooling capacity of the tested system was largely a function of the local wet bulb depression, as instantaneous reading as well as short-term trend. Additionally, solar irradiation and wind speed were found to be negatively and positively correlated, respectively.

Previous measurements (Del Rio et al. 2019) have confirmed the formation of cool summer microclimates through a combination of passive cooling elements (i.e., evaporative cooling louver, vegetation, and sunscreen) in semi-outdoor building spaces in Japan. Computational fluid dynamics (CFD) simulation is useful to understand the contribution of each element to semi-outdoor and indoor microclimates with natural ventilation, and to determine their effective combination. To date, there have not been sufficient studies on the modeling and validation for the CFD simulation of microclimates by such elements. This study demonstrates the modeling method using literature-based values and field measurements. It also demonstrates model validity by comparing the obtained results with field measurements. The results show that CFD simulation with detailed modeling of these elements can replicate vertical temperature distributions at four different positions across the semi-outdoor space and indoor space. The maximum difference in air temperature between the measurements and simulation results was 0.7&ndash, 1 &deg, C. The sensitivities of each passive cooling element on the microclimates formed in both spaces were confirmed. The watered louver condition and shorter louver&ndash, window distance were most effective in cooling both spaces. These results indicate that the modeling method could be effectively applied to assess cool microclimates and formulate a passive cooling design.

The main objective of this paper is to estimate the system performance of an evaporative cooling assisted outdoor air system for air conditioning a data center. To evaluate the computer room air conditioning (CRAC) system used evaporative cooling technology, a mock-up for evaporative cooling assisted outdoor air system was designed. The feasibility of the evaporative cooling assisted outdoor air system is analysed by experimental test for a modular data center in Anseong, Korea. A mock-up system is designed by 43,000 m3/h of design fan flow, 160kW of the cooling capacity for air conditioning a data center. A design condition for the indirect evaporative cooler was set in 50% of sensible heat exchange efficiency and 65% of indirect evaporative cooling efficiency, respectively. A server rack simulator was installed to adjust the 160kW of sensible heat emission of modular data center. The experiment results show that the 59% of a sensible heat exchange efficiency and 78% of indirect evaporative cooling efficiency under experimental conditions.

วารสารวิชาการและวิจัย มทร.พระนคร สาขาวิทยาศาสตร์และเทคโนโลยี, 12, 2, 1-9

New research on evaporative cooling and breathable walls has demonstrated the potential for smart designs where conductive, convective, and radiative heat fluxes are matched or supplemented through low-energy natural phenomena such as wet-bulb temperature depression associated with evaporation. This research seeks to examine the operational and theoretical performance of novel vapor permeable evaporative cooling membrane layers. Latent heat is removed through the evaporation of water through the membrane, where contaminants remain in solution as the hydrophobic membrane allows for passage of only water vapor. Through steady-state analysis of a proposed cooling system for building exterior walls, cooling capacity was shown to exceed cooling loads for large indoor areas. Candidate materials produced from recycled glass were examined through sintering, hydrophobing, and other processes to create materials with the requisite properties specified by simulations. Real data acquired for Princeton, NJ from July 2011 was inputted to the simulations to quantify behavior of the system under real conditions. Even in the humid climate of New Jersey in July, the system can supplement a conventional cooling system, acting as a buffer between interior and external environments. Additionally, the novel mathematical model developed to simulate this evaporative process is in 0.04 ± 0.28 °C agreement to measured data.

This paper evaluates and compares the system performance of a solar desiccant-evaporative cooling (SDEC) system with a referenced conventional variable air volume (VAV) system for a typical office building in all 8 Australian capital cities. A simulation model of the building is developed using the whole building simulation software EnergyPlus. The performance indicators for the comparison are system coefficient of performance (COP), annual primary energy consumption, annual energy savings, and annual CO2 emissions reduction. The simulation results show that Darwin has the most apparent advantages for SDEC system applications with an annual energy savings of 557 GJ and CO2 emission reduction of 121 tonnes. The maximum system COP is 7. For other climate zones such as Canberra, Hobart and Melbourne, the SDEC system is not as energy efficient as the conventional VAV system.

Highlight Stomatal conductance of two species (a broadleaf and a conifer) increased with increasing temperature. This response was independent of carbon metabolism, plant water status, or vapour pressure difference., The effect of temperature on stomatal conductance (gs) and corresponding gas exchange parameters was studied in two tree species with contrasting leaf anatomy and ecophysiology—a broadleaf angiosperm, Populus deltoides x nigra (poplar), and a needle-leaf gymnosperm, Pinus taeda (loblolly pine). Experiments were conducted in growth chambers across a leaf temperature range of 19–48°C. Manipulations of temperature were done in well-watered and drought soil conditions and under ambient (400 ppm) and elevated (800 ppm) air CO2 concentrations. Increases in leaf temperature caused stomatal opening at both ambient and elevated [CO2]. The gs increased by 42% in poplar and by 40% in loblolly pine when leaf temperature increased from 30°C to 40°C at a vapour pressure difference of 1 kPa. Stomatal limitation to photosynthesis decreased in elevated temperature in loblolly pine but not in poplar. The ratio of net photosynthesis to gs depended on leaf temperature, especially at high temperatures. Evaporative cooling of transpiring leaves resulted in reductions in leaf temperature up to 9°C in well-watered poplar but only 1°C in drought-stressed poplar and in loblolly pine. As global mean temperatures rise and temperature extremes become more frequent and severe, understanding the effect of temperature on gs, and modelling that relationship, will become increasingly important.

© 2017 by the authors. Solar desiccant cooling is widely considered as an attractive replacement for conventional vapor compression air conditioning systems because of its environmental friendliness and energy efficiency advantages. The system performance of solar desiccant cooling strongly depends on the input parameters associated with the system components, such as the solar collector, storage tank and backup heater, etc. In order to understand the implications of different design parameters on the system performance, this study has conducted a parametric analysis on the solar collector area, storage tank volume, and backup heater capacity of a solid solar desiccant cooling system for an office building in Brisbane, Australia climate. In addition, a parametric analysis on the outdoor air humidity ratio control set-point which triggers the operation of the desiccant wheel has also been investigated. The simulation results have shown that either increasing the storage tank volume or increasing solar collector area would result in both increased solar fraction (SF) and system coefficient of performance (COP), while at the same time reduce the backup heater energy consumption. However, the storage tank volume is more sensitive to the system performance than the collector area. From the economic aspect, a storage capacity of 30 m3/576 m2 has the lowest life cycle cost (LCC) of 405,954 for the solar subsystem. In addition, 100 kW backup heater capacity is preferable for the satisfaction of the design regeneration heating coil hot water inlet temperature set-point with relatively low backup heater energy consumption. Moreover, an outdoor air humidity ratio control set-point of 0.008 kgWater/kgDryAir is more reasonable, as it could both guarantee the indoor design conditions and achieve low backup heater energy consumption.

Cooling sector plays a crucial role in the World’s transition towards an efficient and decarbonised energy system. Solar cooling is an attractive idea because of the chronological coincidence between available solar radiation and cooling needs. This paper studies the possibility of increasing the efficiency of solar photovoltaic modules by evaporative cooling. This, combined with the use of a water condensed chiller, will enable an efficient cooling system design as a whole. To achieve this goal this paper experimentally evaluates the thermal and electrical performance of a Photovoltaic Evaporative Chimney. A prototype with two photovoltaic modules was built; one of them is used as a reference and the other is modified in its rear side including the evaporative solar chimney. The system is able to dissipate a thermal power of about 1500 W with a thermal efficiency exceeding 30% in summer conditions. The module temperature differences reach 8 K, depending on the wind conditions and ambient air psychrometric properties. Regarding the electrical efficiency, the results showed an average improvement of 4.9% to a maximum of 7.6% around midday in a typical summer day for a Mediterranean climate. The authors wish to acknowledge the collaboration in the experimental work of the following Mechanical and Electrical Engineering students: S. Rodríguez, J.F. Bernal, P. Díez, H. Garcés, C. Selva, V. García, J. Navas and E. Gálvez; and especially to E. Sánchez for his amazing work as a lab technician.

Introduction: The study evaluated the effect of low ambient relative humidity on physical performance and perceptual responses during load carriage in a hot environment. Methods: Ten heat-unacclimatized male subjects participated in three 130-min trials, during which they walked on a treadmill, carrying a load of ~35 kg, at a speed of 3.2 km.h−1, with an incident wind at the same velocity and ambient temperature at 45°C. Each trial commenced with a 10-min baseline at 20°C and 50% relative humidity (RH), the subjects transferred to a climatic chamber and commenced their simulated hike, comprising two 50-min walks separated by a 20-min rest period. In two, full protective equipment (FP) trials, RH was 10% (partial pressure of water vapor, pH2O = 7.2 mmHg) in one (FP10), and 20% (pH2O = 14.4 mmHg; FP20) in the other. In the control trial, subjects were semi-nude (SN) and carried the equipment in their backpacks; RH was 20%. Measurements included oxygen uptake, ventilation, heart rate, rectal and skin temperatures, heat flux, temperature perception, and thermal comfort. Results: In FP20, four subjects terminated the trial prematurely due to signs of heat exhaustion; there were no such signs in FP10 or SN. Upon completion of the trials, pulmonary ventilation, heart rate, and rectal temperature were lower in FP10 (33 ± 5 l/min; 128 ± 21 bpm; 38.2 ± 0.4°C) and SN (34 ± 4 l/min; 113 ± 18 bpm; 38.1 ± 0.4°C than in FP20 (39 ± 8 l/min; 145 ± 12 bpm; 38.6 ± 0.4°C). Evaporation was significantly greater in the SN compared to FP10 and FP20 trials. FP10 was rated thermally more comfortable than FP20. Conclusion: A lower ambient partial pressure of water vapor, reflected in a lower ambient relative humidity, improved cardiorespiratory, thermoregulatory, and perceptual responses during load carriage.