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Preparation of atomic Bose–Einstein condensate (BEC) with tunable interactions in a quasi-one-dimensional (quasi-1D) optical trap is essential for both the observation of bright matter-wave solitons and the quantum simulation based on the discrete atomic momentum states. However, the quasi-1D BEC has been obtained by a complex process, which includes the creation of a three-dimensional BEC and its adiabatic transform into a quasi-1D trap. Here, we report the direct creation of a quasi-1D BEC of 133 Cs atoms by the fast evaporative cooling of ultracold atoms prepared by the degenerated Raman sideband cooling. We produce the pure BEC of up to 5.5 × 10 4 atoms in a quasi-1D optical trap with an evaporative time of 6 s. We demonstrate the anisotropic expansion of the atomic cloud after the release from the quasi-1D trap and study the dependence of both the phase space density and the temperature on the number of atoms in the trap during the evaporative cooling. Our study facilitates the promising applications of quasi-1D interacting atomic gases. [ABSTRACT FROM AUTHOR]

In the present work a numerical analysis is presented to identify the separate effect of cooling by radiation and convection, in evaporative meat weight loss during beef carcass cooling process. A transient heat and mass transfer model is proposed using a 3D beef side geometry. Water activity variations are incorporated in the model. Convective coefficients are obtained from correlations by considering buoyancy effect due to temperature and vapor concentration gradients, and forced air flow. For the purpose of model water mass diffusion into the carcass, a first approximation of the meat layer thickness affected by drying is obtained from an analytical analysis as a semi-infinite solid. The model is solved numerically and it is validated with experimental data from the literature. Results of heat load and weight loss are compared to models proposed by other authors. Temperature and surface water activity evolution, and temperature and water content profiles are analyzed also. Finally, a sensitivity study is carried out on the main result of the model, total evaporated mass, varying heat convection coefficient and radiative cooling. It is found that there is a convective heat transfer coefficient that maximize the evaporative losses, so it is important to operate far from this point in order to reduce the evaporated mass. Furthermore, radiation during the meat cooling process turns out to be an interesting method to rapidly cool meat without increasing the evaporated mass (radiation cooling). Results shows that combining properly the convection and radiation heat transfer, evaporation losses can be reduced. • A simplified model to predict beef side weight loss is validated. • Both natural and forced convection are relevant during meet chilling process. • An upper limit of meat thickness affected by drying is analytically estimated. • There is a convective coefficient value that maximizes weight loss. • Theoretically a reduction in evaporated mass might be achieved by radiative cooling. [ABSTRACT FROM AUTHOR]

Highlights: Engineering MXene into electrospun nanofibers can effectively enhance its thermal emissivity and conductance, and the unidirectional water transport of the wettability-gradient-induced-diode (WGID) membrane displayed diode-like properties with wettability gradient by tailoring the water contact angle of each single layer. The WGID membrane could achieve a cooling temperature of 1.5 °C in the "dry" state, and 7.1 °C in the "wet" state, with high emissivity of 96.40% in the MIR range, superior thermal conductivity of 0.3349 W m−1 K−1. Zero-energy-consumption for personal cooling management via multiple heat dissipation pathways, including thermal radiation, conduction, and evaporation. Thermoregulatory textiles, leveraging high-emissivity structural materials, have arisen as a promising candidate for personal cooling management; however, their advancement has been hindered by the underperformed water moisture transportation capacity, which impacts on their thermophysiological comfort. Herein, we designed a wettability-gradient-induced-diode (WGID) membrane achieving by MXene-engineered electrospun technology, which could facilitate heat dissipation and moisture-wicking transportation. As a result, the obtained WGID membrane could obtain a cooling temperature of 1.5 °C in the "dry" state, and 7.1 °C in the "wet" state, which was ascribed to its high emissivity of 96.40% in the MIR range, superior thermal conductivity of 0.3349 W m−1 K−1 (based on radiation- and conduction-controlled mechanisms), and unidirectional moisture transportation property. The proposed design offers an approach for meticulously engineering electrospun membranes with enhanced heat dissipation and moisture transportation, thereby paving the way for developing more efficient and comfortable thermoregulatory textiles in a high-humidity microenvironment. [ABSTRACT FROM AUTHOR]

Evaporative cooling stands as the prevailing method for achieving ultracold temperatures in atomic systems. Current schemes of evaporation selectively remove the hotter atoms near the edge of the trap, as the hotter and colder atoms are distributed in different spatial regions of the trapping potential. However, a long-standing goal is to directly remove the higher momentum atoms, irrespective of their spatial distribution. For this purpose, we demonstrate collisional cooling for a 6Li Fermi gas through inelastic three-body recombination near a narrow Feshbach resonance. Such three-body recombination can induce either heating or cooling effects, and the decay of the quasi-bound Feshbach molecule stirs the hotter atoms away from the trapping potential. When the threshold energy of the Feshbach molecule exceeds the atom's average kinetic energy of 3/2kBT, the cooling effect becomes more pronounced. Finally, we observe strong temperature dependence in this collisional cooling process, with greater efficiency achieved at lower temperatures. Evaporative cooling is the prevailing method for achieving ultracold temperatures in atomic systems, but the schemes to remove hotter atoms are limited by the spatial profile of the trapping potential. To overcome this limitation, the authors demonstrate a three-body recombination-based collisional cooling scheme for selective removal of hotter atoms. [ABSTRACT FROM AUTHOR]

With the great increase in installation, photovoltaics will develop as the main power supply source for the world shortly. However, the actual power generation and lifetime of photovoltaics are greatly compromised by the high working temperature under outdoor operation. In this review, the recent advances of four promising passive photovoltaic cooling methods are summarized with the aim to uncover their working principles, cooling performance, and application potential in photovoltaic devices. For radiative cooling, light management strategies with ultraviolet‐photon downshift and sub‐bandgap reflection are discussed in detail to reveal their great potential in reducing photovoltaic working temperature and enhancing power generation. Subsequently, the great cooling benefits of passive evaporative cooling are underlined in terms of its superior cooling power and temperature drop of photovoltaic devices. Moreover, the promising integrated cooling strategy is further highlighted due to its great potential in enhancing electricity production and fresh water supply. Most crucially, the remaining challenges and the authors'r insights are presented to advance the commercial applications of passive cooling methods in photovoltaics. [ABSTRACT FROM AUTHOR]

Heat stress is being exacerbated by global warming, jeopardizing human and social sustainability. As a result, reliable and energy-efficient cooling methods are highly sought-after. Here, we report a polyacrylate film fabricated by self-moisture-absorbing hygroscopic hydrogel for efficient hybrid passive cooling. Using one of the lowest-cost industrial materials (e.g., sodium polyacrylate), we demonstrate radiative cooling by reducing solar heating with high solar reflectance (0.93) while maximizing thermal emission with high mid-infrared emittance (0.99). Importantly, the manufacturing process utilizes only atmospheric moisture and requires no additional chemicals or energy consumption, making it a completely green process. Under sunlight illumination of 800 W m−2, the surface temperature of the film was reduced by 5 °C under a partly cloudy sky observed at Buffalo, NY. Combined with its hygroscopic feature, this film can simultaneously introduce evaporative cooling that is independent of access to the clear sky. The hybrid passive cooling approach is projected to decrease global carbon emissions by 118.4 billion kg/year compared to current air-conditioning facilities powered by electricity. Given its low-cost raw materials and excellent molding feature, the film can be manufactured through simple and cost-effective roll-to-roll processes, making it suitable for future building construction and personal thermal management needs. Gan et al. have developed sodium polyacrylate-based films for passive radiative cooling that can be fabricated using atmospheric moisture alone, offering radiative and evaporative cooling, reducing temperatures by up to 5 °C under partly cloudy skies. [ABSTRACT FROM AUTHOR]

Personal cooling garments (PCGs) have gained increasing attention as a promising solution to alleviate heat stress and enhance thermal comfort in hot and humid conditions. However, limited attention has been paid to the influence of clothing design on cooling performance. This review highlights the influence of design factors and provides a quantitative comparison in cooling performance for different types of PCGs, including air cooling garments, evaporative cooling garments, phase-change cooling garments, and liquid cooling garments. A detailed discussion about the relationship between design factors and the cooling performance of each cooling technique is provided based on the available literature. Furthermore, potential improvements and challenges in PCG design are explored. This review aims to offer a comprehensive insight into the attributes of various PCGs and promote interdisciplinary collaboration for improving PCGs in both cooling efficiency and garment comfort, which is valuable for further research and innovation. [ABSTRACT FROM AUTHOR]

Incorporating zero‐energy‐input cooling technology into personal thermal management (PTM) systems is a promising solution for preventing heat‐related illnesses while reducing energy consumption. Although concepts for passive radiative cooling materials are proposed, achieving subambient cooling performance while providing good wearing comfort remains a challenge. Here, a moisture‐wicking nonwoven metafabric is reported that assembles radiative cooling and evaporative heat dissipation to achieve high‐performance thermal and moisture comfort management. This metafabric demonstrates excellent spectral‐selectivity (sunlight reflection of ≈92%, atmospheric window thermal emissivity of ≈97%) and Janus wettability through large‐scale electrospinning and hierarchical design, and also inherits superior elasticity, air/moisture permeability of nonwoven fabric. Subambient temperature drops of ≈6.5 °C (≈750 W m−2 solar intensity) for stand‐alone metafabric are observed. Thanks to the moisture‐wicking effect (water evaporation rate of 0.31 g h−1 and water transport index of 1220%) of metafabric that enables fast evaporation of sweat, a maximum generation of 1 mL h−1 of sweat can cool the skin, thus reducing the excessive sweating risk after intense exercise. Additionally, the cooling performance of metafabric can be regulated by applying various strains (0–100%). The cost‐efficiency and good wearability of metafabric provide an innovative way to sustainable energy, smart textiles, and thermal wet comfort applications. [ABSTRACT FROM AUTHOR]

All-day passive radiative cooling is a promising cooling technique achieves cooling without any energy input, thereby attracting tremendous attention. Most of the studies focus on building applications, but there remains a lack of information on other potential applications of radiative cooling systems. Herein, we report an application of a polymeric passive radiative cooling coating (PRCC) on the exterior surface of chemical storage tanks, which is often overlooked but exhibits great potential to efficiently control the evaporative loss of the chemicals. The PRCC exhibits strong solar reflectivity (96.2%) and emissivity (95%) in the mid-infrared wavelength range. According to the results of an outdoor test on a small-scale chemical storage container, the PRCC achieves 81.4%, 54.1%, and 19.8% of chemicals saved compared with a raw container, container painted with commercial white paint (CWP), and the shaded raw container, respectively. A numerical simulation is also conducted to estimate the chemical standing loss from an industrial large-scale chemical storage tank. It is found that the PRCC can achieve a saving of over 50% of the chemical compared with commercial white paint for a chemical storage tank, showing a promising potential to be applied on chemical storage systems. • Excellent optical properties of spectral selectivity for radiative cooling. • Achieved all-day sub-ambient cooling on both clear and cloudy days. • Evaporation loss is investigated experimentally and numerically. • Over 50% of chemicals can be saved via the radiative cooling technology. [ABSTRACT FROM AUTHOR]

The construction of evaporative coolers in remote areas can increase the longevity of vegetables, improving food security and the local economy of small farmers in remote, impoverished communities without access to electricity. This work presents a 1:1 scale prototype of an 8 m3 (2.1 × 2.1 × 2.3 m) stabilized adobe evaporative cooler, with a design based on the appropriate technology framework, and it was built as a chamber using double adobe walls, filled with wet sand, to induce evaporative cooling. Furthermore, the paper presents the prototype's performance evaluation. The tests were carried out in the dry and wet states, with different volumes of water. The results show good performance compared with other prototypes, although the optimum watering volume could not be determined because of the high climate variance (outside temperature and humidity) that prevented the repetition of the experiments in identical operating conditions. Stabilized adobe proved to be a good choice for use in the cooler, even when subject to moisture accumulation, indicating an estimated long lifetime for the cooler. The data obtained about the efficiency of evaporative cooling show that the cooler, as expected, has its best performance on the hottest and driest days, reducing the internal temperature (up to 13.24 °C) and managing to keep the internal humidity. The cost, efficiency, durability, and replicability make the proposed evaporative cooler a feasible solution for food preservation. [ABSTRACT FROM AUTHOR]

In light of energy and climate targets, free cooling unlocks a major resource-saving potential compared to refrigeration. To fill the knowledge gap in quantifying this saving potential, we aim to specify the physical and technical limits of cooling tower applications and provide comprehensive data on electricity and water consumption. For this purpose, we distinguish six types of package-type cooling towers: dry, closed wet, open wet, and three types of hybrid systems; defining one generalized system for all types enables comparability. Subsequently, we collect data from 6730 system models of 27 manufacturers, using technical information from data sheets and additional material. The analysis reveals, for example, specific ranges of electricity demand from 0.01 to 0.06 kWel/kWth and highlights influencing factors, including type and operating point. Refrigeration systems would consume approximately ten times more electricity per cooling capacity. Furthermore, the evaluation demonstrates the functional limits, for example, the minimum cooling temperatures. Minimum outlet temperatures using evaporative cooling are up to 16 K lower than for dry cooling. The collected data have crucial implications for designing and optimizing cooling systems, including potential analysis of free cooling and efficiency assessment of cooling towers in operation. [ABSTRACT FROM AUTHOR]

• A heat and mass transfer model of droplet for artificial snow-making was established. • The critical droplet size for artificial snow-making under different environments was obtained. • The relationship between gas-liquid mass mixing ratio and snow-making density was studied, and the optimal gas-liquid mass mixing ratio suitable for artificial snow-making was obtained. This study investigates the heat and mass transfer of liquid droplets freezing in the process of artificial snow-making, and emphatically analyses the effects of droplet size, ambient temperature and relative humidity on the evaporative cooling and freezing of liquid droplets by establishing a theoretical model. On this basis, the critical droplet size for snow-making under different environmental conditions is obtained, and the accuracy of the droplet freezing model was verified by artificial snow-making experiments. Finally, by analyzing the density of artificial snow under different environmental conditions, the optimum gas-liquid mixing mass ratio (GLR) suitable for snow-making is obtained. The results show that the liquid droplets could be frozen under the action of self-evaporation and convection heat transfer with ambient. The time required for the droplet to be frozen completely shows a positive correlation with ambient temperature, relative humidity and droplet size. In the evaporation cooling stage, the droplet cooling rate increases with the decrease of ambient temperature, and in the phase transition stage, the time for the droplet resists the latent heat of phase transition increases with the increase of the droplet size. When the droplet size is smaller than the critical size for snow-making, the artificial snow can be achieved at a maximum temperature of 3 °C. The snow density decreases with the increase of GLR. And when the GLR is greater than 0.15, the snow density tends to be stable. [ABSTRACT FROM AUTHOR]

Strategies and guidelines for best practice environmental design typically have a singular focus and intended outcome, for example, green infrastructure management for urban cooling in a hotter climate. However, when applied to specific situations such as aged care, matters such as accessibility, wayfinding, and safety are also critical. Combining various audit tools offer multiple benefits to meet a variety of needs for thermal comfort, health, and well-being, as well as cost-effectiveness. In the absence of such a tool, using a place-based analysis, we developed a novel audit tool for external settings of residential aged care facilities (ACFs) incorporating urban cooling, Crime Prevention Through Environmental Design (CPTED), and universal design criteria. To determine how ACFs perform in the face of increased levels of urban heat required evaluation of additional urban cooling measures. The Audit Tool was developed and tested in collaboration with ACFs across sub-tropical and tropical areas of Australia, varying in climate, scale, and urban density. Quality of life for residents, visitors, and staff of ACFs can be supported by the provision of green infrastructure to improve the thermal comfort of outdoor settings and, if located appropriately, reduce the need for an increase in internal air-conditioning. The aim of this article is to propose a user-friendly Hybrid Environmental Design Audit Tool (HEDAT) to support facility managers, planners, and design consultants to inform the prioritization and targeting of interventions and monitoring of implementation and outcomes. [ABSTRACT FROM AUTHOR]

This work presents an experimental evaluation of the performance of a cooling pad made from the locally available material "Torai" (luffa cylindrica). Different performance parameters that define the cooling performance of the proposed pad, such as the exit air temperature, degree of cooling, saturation effectiveness, cooling potential, and coefficient of performance, have been experimentally investigated. Results show that the overall cooling performance (cooling potential, degree of cooling, effectiveness, and coefficient of performance) increases by increasing the pad thickness. For a given pad an increase in air velocity decreases the saturation efficiency and degree of cooling. The maximum saturation effectiveness and coefficient of performance found for a 7 cm pad at 1.5 m/s air velocity are 65.9% and 8.53, respectively. The rate of water evaporation increases by increasing the pad thickness and air velocity. The maximum water evaporation rate found is 1.4 g/s for a 7 cm pad at 1.5 m/s air velocity. The water retention capacity of the proposed pad material is about 78 g. Moreover, it may be concluded that the proposed pad shows reasonably good performance to be employed as a pad material for direct evaporative coolers. The cost of manufacturing a pad 30.48 cm2 is between Rs130 (US$1.625) and Rs234 (US$2.925). [ABSTRACT FROM AUTHOR]

Building energy consumption in hot arid climates is dominated by air conditioning use. Therefore, using passive cooling methods could reduce this demand, improve resource efficiency, and decrease carbon emissions. In this study, an innovative configuration of a passive downdraught evaporative cooling (PDEC) tower is investigated numerically. The governing equations are solved using the finite element method (FEM), and the effects of inlet velocity (0.5 m·s−1 ≤ uin ≤ 3 m·s−1) and temperature (35 °C ≤ Tin ≤ 45 °C) on the fluid structure, temperature field, and relative humidity are studied for three cases related to the position of the air outlet. The flow is considered as turbulent, and the building walls and the tower are assumed to be thermally well insulated. The PDEC tower is equipped with two vertical isotropic saturated porous layers. The results revealed that the inlet velocity and temperature play an essential role in the quality of the indoor temperature. In fact, the temperature can be reduced by about 7 degrees, and the relative humidity can be enhanced by 9% for lower inlet velocities. [ABSTRACT FROM AUTHOR]

In view of the ageing domestic building stock and increasing reliance on fossil fuels for cooling and ventilation of buildings, there is an urgent need for improved design knowledge and sustainable measures such as natural ventilation and passive cooling to mitigate climate change and future proof the built environment. This paper forms an appraisal of a range of low-energy refurbishment measures, i.e. building design alterations and passive systems, which were employed and evaluated in an apartment building in Greece. The applicability of these in domestic buildings in hot climates is assessed and their design implications evaluated. Implementation of wind-catchers, dynamic façades, and evaporative cooling had the highest ventilation and cooling potential, while improvements of the interior layout to allow for new airflow paths could provide further cooling to spaces and solutions to safety. [ABSTRACT FROM AUTHOR]

Passive daytime radiative cooling (PDRC) has attracted intensive attention due to its great potential in reduced energy consumption. However, the practical application for PDRC is greatly affected by geographical location and the intrinsic cooling power. Herein, a composite flexible fabric with the synergistic effect of evaporative cooling and radiative cooling is reported. A porous polymer coating with both a high solar reflectivity (90%) and a high infrared thermal emissivity (83%) is fabricated on the top side of the fabric, which can achieve effective PDRC performance. Meanwhile, hygroscopic salts are loaded on the bottom side of the fabric, which can capture water vapor at night and realize evaporative cooling during the daytime. The temperature reduction of 10.8 °C can be achieved under the direct sunlight irradiation (465 W m−2) for the prepared fabric in the outdoor experiment. The combination of radiative cooling and evaporative cooling breaks through the traditional single passive cooling mode and has great potential in further improving the performance of passive cooling. [ABSTRACT FROM AUTHOR]

Thermal comfort is an important determinant of quality of life and economic vitality in cities. Strategies to improve thermal comfort may become a more critical part of urban sustainability efforts with projections of continued urban growth and climate change. A case study was performed in the hot, dry summertime climate of Tempe, Arizona to quantify the influence of evaporative misters on the thermal environment in outdoor restaurants and to understand business managers' motivations to use misters. Microclimate measurements (air temperature (Ta), wind speed, relative humidity, globe temperature) were taken at five restaurants midday within four exposures: misted sun, misted shade, sun only, and shade only. We assessed Ta, mean radiant temperature (MRT), universal thermal climate index (UTCI), and physiological equivalent temperature (PET) between these four conditions within each location. Misters improved thermal comfort across all days, sites, and exposure conditions. MRT was on average 7.6 °C lower in misted locations, which significantly lowered average PET (– 6.5 °C) and UTCI (– 4.4 °C) (p < 0.05). Thermal comfort was most improved using mist in combination with shade. Under such conditions, PET and UTCI were reduced by 15.5 °C and 9.7 °C (p < 0.05), respectively. Business managers identified customer comfort and increased seating capacity as the principal factors for mister use. Esthetics of misters further encouraged use, while cost and environmental concerns were perceived to be less important. While this case study demonstrates value in outdoor misting in a hot, dry climate, additional work is needed to more fully evaluate tradeoffs between cost, water use, and comfort with continuing urban growth. [ABSTRACT FROM AUTHOR]

The Intrachip Enhanced Cooling Fundamentals (ICECool Fun) effort was launched by the Defense Advanced Research Projects Agency (DARPA) under the leadership of Dr. Avram Bar-Cohen during 2012–2015 to target an order of magnitude improvement in chip level and hot spot heat fluxes, compared to the then state-of-the-art (SOA). Evaporative cooling technologies to achieve potential targets of 1 kW/cm2 at the chip level and 5 kW/cm2 at the hot spot level were targeted. A key goal was to improve fundamental understanding of the evaporative cooling physics at the relevant scales, and a numerical modeling capability to enable the co-design of such solutions in emerging computing and communications systems. A summary of the five projects pursued under this effort is provided, including the key accomplishments and developed capabilities. [ABSTRACT FROM AUTHOR]

Evolution of a large part of low-mass X-ray binaries (LMXBs) leads to the formation of rapidly rotating pulsars with a helium white dwarf (He WD) companion. Observations indicate that some He WDs in binary pulsar systems are ultracool (with the effective temperatures T eff ≲ 4000 K). It is hard to cool down a He WD to such low temperatures within the Hubble time because a thick hydrogen envelope was left behind around the He core after the mass transfer process. A possible mechanism that can accelerate the WD cooling is the evaporative wind mass-loss from the He WD driven by the high-energy radiation from the recycled pulsar. In this paper, we evolve a large number of LMXBs and investigate the influence of the pulsar's high-energy radiation on the WD cooling with different input parameters, including the neutron star's spin-down luminosity, the evaporation efficiency, and the metallicity of the companion star. By comparing our results with observations we note that, for relatively hot He WDs (with T eff > 7000 K), standard WD cooling without evaporation considered is able to reproduce their temperatures, while evaporation is probably required for the He WDs with relatively low temperatures (T eff < 5000 K). [ABSTRACT FROM AUTHOR]

Dissipative energy fluxes in evaporative cooling of a substrate by droplets carried in by an air flow have been measured. It has been shown that the frequency of feeding the spray and the difference between its temperature and the temperature of the substrate influence the efficiency of its cooling. Spraying pulses with a relative duration of 0.5 and 0.25 have been investigated. It has been found that the form of these pulses does not influence, in practice, the intensity of cooling of the substrate at spray-feed frequencies higher than 3 Hz. It has been confirmed that the thermal conductivity and thickness of the substrate substantially influence the value of the energy flux dissipated by it. [ABSTRACT FROM AUTHOR]

• Impacts of the spatial gradient porosity distribution on the cooling performance are explored. • Different stepwise and continuous polynomial distributions of bed porosity are investigated. • The cooling performance is pointedly impacted by the spatial porosity distribution in the z-direction. • SCP under the S1 porosity distribution at 600 s is augmented by 9.5% (0.348 kW/kg). Adsorption cooling is an emerging, environment-friendly and energy-saving refrigeration technology. In conventional studies, the spatial distribution of the porosity of the adsorbent bed has never been considered, which could impact the heat and mass transfer in adsorption process, thus the cooling performance of the adsorption cooling systems. Here the influence of the spatial gradient porosity distribution (stepwise and continuous polynomial distributions) of the adsorbent bed on the adsorption process and cooling performance is systematically explored with average bed porosity kept constant. Results reveal that the cooling performance is significantly impacted by the spatial porosity distribution in the z direction. Provided the bed porosity increases from the cooling side to the steam side, the overall heat transfer performance is improved, which reduces the adsorption temperature that contributes to the adsorption uptake and the specific cooling power (SCP). Under the continuous polynomial distribution of the bed porosity, a SCP of 0.348 kW kg−1 is obtained, 9.5% larger than that under the uniform distribution of the bed porosity. A desired bed porosity distribution of the adsorbent bed is that the porosity gradient increases from the cooling side to the steam side. [ABSTRACT FROM AUTHOR]

Hybrid photovoltaic thermal systems consisting of solar panels and solar thermal absorbers are generally used for improving the electrical and thermal efficiency of the photovoltaic panel by cooling. Thus, thermal energy produced can be used for other applications. Depending on solar insolation and location, building integrated photovoltaic (BIPV) systems are designed and developed to fulfill energy needs. This paper reviews the detailed study on the effect of the front surface, back surface and combined front and back surface cooling on the water-based photovoltaic systems. This paper also discusses different designs of solar thermal absorber collectors. The front surface cooling resolves two problems. Firstly, it significantly reduces the PV panel temperature by 22–27 °C depending on the cooling phenomena used and secondly, it cleans the PV panel, thereby increasing the optical efficiency. The PV panel temperature reduction (5–6 °C) in the water spraying cooling system is more than water flowing over the front surface. The photovoltaic thermal absorber collector system is the most economically viable system from the electrical and thermal energy generation perspectives. The evaporative cooling on the backside of PV panels using clay and cotton wick structure could be an effective solution for a standalone PV system. It is observed that dual cooling is suitable for PV panels cooling in a hot arid region but needs further investigation. Finally, the environmental impact and economic feasibility of water-based photovoltaic cooling systems are discussed. [ABSTRACT FROM AUTHOR]

The viability of fan and natural ventilation, combined with evaporative cooling, was investigated using a simulation model and weather data for thirty-seven locations in the world (mostly in China). And the geographical distribution pattern of viable cooling technologies was examined in China. The model used was based on a simplified steady-state heat balance of a greenhouse, and weather data were from corresponding meteorological organizations. The evapotranspiration coefficient used two values of 0.5 and 1.0, and ventilation rates for natural ventilation were based on two empirically constructed equations. The results suggested that the viability of various cooling technologies depended largely on local weather, although evapotranspiration coefficient and ventilation characteristics of natural ventilation also played important roles. Some locations were sensitive to evapotranspiration coefficient and ventilation rate while some were not. The locations which were not sensitive to evapotranspiration coefficient and ventilation rate could choose the most economical technology to meet the cooling minimum, but these locations which were sensitive required evaporative cooling and/or forced ventilation. A detailed examination of the geographical pattern of viable cooling technologies was conducted for China. The results suggest that high altitude general provides a cooling advantage [ABSTRACT FROM AUTHOR]

In this study, the system which provides cooling of a place by using indirect evaporative cooling system is developed and experimentally analyzed. Fresh and hot air blown by fan from outside environment and cool indoor air are mixed in certain proportions and blown to the rotary wheel's exterior surface. The indoor air is cooled by the humidifiers before entering the rotary wheel via direct evaporative cooling. So the rotary wheel works as a heat exchanger between the indoor and outside air without mixing. By cooling the outside of the rotary wheel, the cool air enters the cross flow heat exchanger. It is allowed to cool again with the indoor air passing through the rotating wheel and being moisturized twice. In this way the room is kept comfortable. According to the results of the experiments, it is observed that the highest COP value of 2,72 is obtained when mixing 20 % fresh air and 80 % indoor air. Although this value is lower than the theoratically calculated, if leakproofing and insulation can be managed perfectly, it is clear that COP value can be much higher. [ABSTRACT FROM AUTHOR]

• Carnot limits for separate sensible and latent cooling (SSLC) systems are defined • SSLC efficiency limits are 1.3 to 15 times higher than conventional cooling • Potential energy savings are highest for high building sensible loads • SSLC also excels at low temperature lift and large indoor dewpoint depression • A taxonomy of SSLC systems provides a roadmap for future development Energy efficiency and thermal comfort can be improved by independent control of temperature and humidity. In recent work, an emerging class of cooling systems known as separate sensible and latent cooling (SSLC) systems have demonstrated 14 to 47% energy savings, while simultaneously providing better comfort control than conventional air conditioning. In this work, SSLC is defined as using two or more cooling processes with unequal sensible heat ratio (SHR) to control temperature and humidity independently and dynamically. Fundamental efficiency limits of SSLC systems are developed for the first time, demonstrating that the Carnot efficiency for SSLC is higher than that of conventional systems. It is revealed that SSLC has particularly high potential for moderate outdoor temperatures, high sensible building loads, and drier indoor conditions. In addition, this work proposes a classification scheme for SSLC systems, revealing an enormous number of feasible cycle permutations. This provides a framework for the important research task of developing SSLC systems that will save energy, be practical to construct, and be controllable. [ABSTRACT FROM AUTHOR]

This research proposes the use of membrane-assisted radiant panels to improve the thermal comfort of naturally ventilated spaces in hot and humid climates. These radiant panels are capable of conditioning naturally ventilated spaces, which is impractical with conventional mechanical cooling systems. For conventional systems, a permeable envelope will result in energy wastage from conditioned air escaping or condensation occurring on the radiant surfaces. In our system, there is no air-conditioning and we avoid condensation by separating the radiant surfaces from humid air using a membrane transparent to thermal radiation. The membrane-assisted radiant panels are an unutilized technology for architects to design comfortable naturally ventilated spaces. We propose a cooling system based on the technology and discuss the architectural implications, particularly the permeability of the building envelope and requirements for mechanical spaces, of employing this system in a case study that is a naturally ventilated classroom. Our system is compared to conventional cooling systems. Although our system requires a ceiling space reconfiguration, it does not require duct works and envelope retrofits. The comparative case study shows a potential 52% reduction in cooling energy demand from initial estimation. Considering the trade-offs, our system can be a good alternative for retrofit projects. [ABSTRACT FROM AUTHOR]

Moisture evaporation plays a crucial role in thermal management of human body, particularly in perspiration process. However, current fabrics aim for sweat removal and takes little account of basic thermo-regulation of sweat, resulted in their limited evaporation capacity and heat dissipation at moderate/intense scenarios. In this study, a hygroscopic cooling (h-cool) fabric based on multi-functional design, for personal perspiration management, was described. By using economic and effective weaving technology, directional moisture transport routes and heat conductive pathways were incorporated in the construct. The resultant fabric showed 10 times greater one-way transport index higher than cotton, Dri-FIT and Coolswitch fabrics, which contributed to highly enhanced evaporation ability (∼4.5 times than cotton), not merely liquid diffusion. As a result, h-cool fabric performed 2.1–4.2 °C cooling efficacy with significantly reduced sweat consuming than cotton, Dri-FIT and Coolswitch fabrics in the artificial sweating skin. Finally, the practical applications by actually wearing h-cool fabric showed great evaporative-cooling efficacy during different physical activities. Owing to the excellent thermo-moisture management ability, we expect the novel concept and construct of h-cool fabric can provide promising strategy for developing functional textiles with great "cool" and comfortable "dry" tactile sensation at various daily scenarios. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high-performance HSEC coating is fabricated for large-scale building cooling. • The HSEC coating has high average solar reflectance (95.1%) and MIR-infrared emissivity (92.5%). • The HSEC coating realizes ambient cooling up to 4.2 °C during the daytime. • The HSEC coating shows excellent anti-contamination property and radiative stability. The building cooling has aroused widespread attention due to its significant contribution to both global warming and energy usage. To combat global warming and reduce energy consumption, an environmentally friendly beneficial alternative to electric cooling for buildings is passive daytime radiative cooling (PDRC). However, many of the reported radiative coolers still suffer from the challenge of complex preparation processes and high costs, making it difficult to scale up for building applications. Herein, the utilization of abundant and low-cost natural resources (i.e., cellulosic biomass and minerals) is strategized to produce radiative cooling material and incorporate this material into building cooling systems to boost global carbon neutrality. Guided by this concept, a hydrophobic SiO 2 /EC composite (HSEC) coating is designed by embedding nano-sized wollastonite-based SiO 2 particles into porous ethyl cellulose (EC) polymer, and subsequently through polydimethylsiloxane (PDMS) dispersion spray treatment. Benefiting from the sufficient scattering by the nano-SiO 2 particles and randomly dispersed light-scattering air voids, the resulting cooling coating shows a high solar reflectivity of 95.1 %. More importantly, the molecular vibration of the chemical in HSEC coating results in a high atmospheric window emissivity of 92.5 %. In the field test, the HSEC coating remained approximately 4.2 °C below the ambient temperature under intense solar irradiation of 412.5 W⋅m−2. This work not only offers a promising strategy for realizing the high-value utilization of wollastonite resources in building materials, but also provides a controllable approach for large-scale preparation of highly efficient radiative cooling materials to alleviate building cooling demands. [ABSTRACT FROM AUTHOR]

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Fabrics which can keep people cool in a hot climate have attracted considerable attention in recent years. Among various cooling strategies, fabric cooling by water evaporation is proved to be very safe, simple and sustainable. Here, a tri-layer laminated fabric (TLF) inspired by perspiration is designed to realize passive cooling of human body. An interlayer fabric which is coated with crosslinked sodium polyacrylate can absorb and store a large amount of water. A moisture-absorbing and quick-drying fabric is used as the outer layer while a waterproof breathable fabric is used on the inside of the laminate in contact with skin. The prepared TLF shows decent evaporative cooling performance under dry heat conditions. The water absorbency of TLF is about 400% higher than that of pristine cotton after 1 h soaking in water. Under a 1 sun irradiation (1000 W m.2), the indoor temperature of a simulated room can be reduced by ≈.5.7 °C compared with the other without a cooling system. Meanwhile, the evaporative cooling effect can be maintained up to 5 h. This cooling fabric shows broad application prospects in the fields of thermal cooling to human and buildings. [ABSTRACT FROM AUTHOR]

The optimization effect of evaporative cooling ventilation cooling system for air compressor room in textile mills were studied. For on-site test of the air compressor room in one textile mill, the standard k-e model in RANS method of numerical simulation was used to simulate the air distribution of air compressor room.Reginal cooling optimization design was performed for the air compressor device. And the effect was compared. The test results showed that the average temperature around 1 m front and back of the device was decreased obviously.The unevenness coefficient of the temperature was decreased from 0.157 6 to 0.112 0. It is considered that the optimization scheme can obviously reduce the surface temperature of the air compressor. The indoor temperature evenness is improved too.It has better cooling effect. [ABSTRACT FROM AUTHOR]

• PCHP is proposed to enhance energy saving in high thermal density space. • Heat transfer and energy consumption models of PCHP are established. • The effects of padding thickness, ambient temperature, relative humidity, and air flow rate on the performance of PCHP are investigated. • Cooling capacity and EER of PCHP are investigated compared with CHP, providing design guide for heat pipe system in application. • The annual free cooling time of PCHP was analyzed in five typical climates in China. High thermal density space consumes massive energy, and cooling device accounts for large percentage of total consumption. To cut down energy consumption of cooling device, PCHP is proposed on the basis of heat pipe and evaporation technologies. Heat transfer and energy consumption models of PCHP are developed. The effects of geometric and operational parameters on the PCHP performance, including pad thickness, ambient temperature and ambient relative humidity (RH), air flow rate, are investigated. The results show that cooling capacity increases with the increase of pad thickness and airflow rate, and it decreases with the increase of ambient temperature and RH. With the increase of thickness, energy efficiency ratio (EER) increases at the start and then decreases under RH20%-40%, while it decreases continuously under RH70%-90%. EER increases with the decrease of ambient temperature, ambient RH and air flow rate. PCHP markedly enhances annual free cooling time compared with conventional heat pipe system (CHP), and the maximal enhanced free cooling time and increasing percentage occur at Urumchi and Guangzhou Cities, respectively. [ABSTRACT FROM AUTHOR]

A comparative study was made on air conditioning system performance improvement by effective condenser cooling and preheating the refrigerant. This study was described with the experimental investigation through a test rig fabricated from car air conditioning components. In which slight modifications were made such as compressor has to run by the electric motor with provision to measure power consumption during functioning and condenser fan has to replace with exhaust fan enclosed by the cooling pad in which water is supplied with a controlled flow rate using a water pump. Preheating of refrigerant is done using engine exhaust gas with counterflow heat exchanger setup. Air conditioning test rig was run to achieve the desired cooling effect for two processes. The coefficient of performance (COP) was calculated in both operating conditions for the same cooling effect and comparative study was made. The conclusion revealed that a new cooling method showed higher COP than preheating. By this approach, the percentage increase in heat removal rate up 37% was achieved which results in decreases the compressor running time thus mileage of vehicle can be improved significantly. [ABSTRACT FROM AUTHOR]

Irrigation is an important adaptation strategy to improve crop resilience to global climate change. Irrigation plays an essential role in sustaining crop production in water‐limited regions, as irrigation water not only benefits crops through fulfilling crops' water demand but also creates an evaporative cooling that mitigates crop heat stress. Here we use satellite remote sensing and maize yield data in the state of Nebraska, USA, combined with statistical models, to quantify the contribution of cooling and water supply to the yield benefits due to irrigation. Results show that irrigation leads to a considerable cooling on daytime land surface temperature (−1.63°C in July), an increase in enhanced vegetation index (+0.10 in July), and 81% higher maize yields compared to rainfed maize. These irrigation effects vary along the spatial and temporal gradients of precipitation and temperature, with a greater effect in dry and hot conditions, and decline toward wet and cool conditions. We find that 16% of irrigation yield increase is due to irrigation cooling, while the rest (84%) is due to water supply and other factors. The irrigation cooling effect is also observed on air temperature (−0.38 to −0.53°C) from paired flux sites in Nebraska. This study highlights the non‐negligible contribution of irrigation cooling to the yield benefits of irrigation, and such an effect may become more important in the future with continued warming and more frequent droughts. [ABSTRACT FROM AUTHOR]

With the cold-fog direct evaporative cooling (CDEC) technology, which uses the natural cooling sources, the cooling energy consumption of data centers can be reduced, and thus the cooling cost can be decreased significantly. There are only a few studies on the application of CDEC in data centers. In this paper, CDEC technology is proposed to provide cooling sources for a data center after cooling the high-temperature fresh air and circulated air from the data center. According to the results of experiments, it can be concluded that only when the relative humidity of high-temperature fresh air is lower than 40 %, the treated air meets the air supply requirements of the data center. otherwise, the circulated air need be treated by CDEC in order to ensure that the air temperature can be reduced to below 30 °C and the relative humidity be less than 80 %. Compared with general evaporative cooling, the efficiency can be improved by 2.07 %–28.50 % with CDEC. Besides, according to the orthogonal experiment, the sequence of various influencing factors on the CDEC is: air speed > spray flow rate > spray angle, which provides guidance for the optimization of application of CDEC in data centers. • Applying cold-fog direct evaporative cooling (CDEC) technology to data centers. • A cooling scheme for data center under a high-temperature climate is proposed. • FDEC can improve the utilization of natural cold sources in data centers. • FDEC is 2.07 %–28.5 % more efficient than general evaporative cooling. • This contributes to achieving free cooling for data centers throughout one year. [ABSTRACT FROM AUTHOR]

• Composite hydrogel was developed for sustainable daytime passive cooling. • Mechanical properties of hydrogel were improved by highly entangled structure. • Hydrogel achieved coupling effects of daytime radiative and evaporative cooling. • Hydrogel realized atmospheric water harvesting at night for next evaporation. • Relationship of daytime passive cooling with night time rehydration was revealed. Daytime passive cooling technology supported by coupling effects of daytime radiative cooling and evaporative cooling has drawn significant attention for alleviating the burdens of energy consumption and greenhouse gas emissions. Incorporating a hygroscopic agent allows the daytime radiative/evaporative cooler to replenish water itself at night, thus ensuring evaporative cooling during the daytime. However, the mechanism of the relationship between daytime passive cooling and nighttime rehydration is not fully understood. Besides, the design of circulating daytime radiative/evaporative coolers is segmented at present, and the poor mechanical properties of hydrogel restrict the practical application. Hence, a tough and elastic hydrogel with a highly entangled structure was prepared by dense polyacrylamide chains, exhibiting the 18-fold tensile stress and 9-fold compressive stress of the control group. Integrating zirconium dioxide (ZrO 2) particles as a spectral regulator, the composite hydrogel possessed solar reflectance of 0.90 and mid-infrared emission of 0.88, realising daytime radiative cooling. After swelling in lithium bromide (LiBr) solution, the composite hydrogel achieved a cycle of daytime evaporative cooling and nighttime rehydration. Besides, the effects of LiBr concentrations on the evaporation and hygroscopicity of the composite hydrogel were investigated. Furthermore, two indoor experiments and one outdoor field test were performed, and the findings suggested that the design of strong hygroscopicity and effective evaporation was a contradiction, and it is crucial to narrow the gap between evaporation and rehydration instead of only pursuing the best cooling performance to achieve sustainable daytime passive cooling. Thus, it is hoped that this study could broaden the field of sustainable daytime passive cooling technologies. [ABSTRACT FROM AUTHOR]

• Thickness profile investigation using reflectometry for a ferro-nanofluid thin film meniscus under the influence of magnetic field. • Significant thinning of the adsorbed layer and elongating of the transition region (flattening effects) reported on the meniscus shape. • The derived curvature and pressure profiles exhibit dominating effect of disjoining pressure in pulling liquid towards the transition region. • Evaporative overall mass flux enhanced up to 156% while the average heat flux increased to 101% on subjecting to magnetic field. This work envisages applying magnetic fields to flatten thin ferro-nanofluid film meniscus for enhanced heat transfer during evaporative cooling process. Experiments are conducted to examine the shape of the evaporating extended meniscus of ferro-nanofluid (Fe 3 0 4 nanoparticles in water suspension 0.01% v/v) under axisymmetric vertical magnetic fields (∼ 10 − 2 T) generated by solenoid placed below the heated substrate. The study includes measuring the thickness profile of the meniscus evaporating region using high nano-scale resolution reflectometry and theoretically interpreting meniscus shape in terms of flow and film heat transfer. Profile measurements reveal an increasing influence of magnetic fields in thinning of the adsorbed region and stretching of the transition region, which effectively reduce the thermal resistance across meniscus width. Data reduction based on thickness as well as the derived curvature profiles yields a high-pressure gradient driving flow along the evaporating thin film region. The results imply additional suction induced by disjoining pressure of thinner adsorbed layer which sustains replenishment of lost evaporative mass across a longer transition region interface. Subsequent heat transfer analysis reveals up to 156 % enhancement in overall heat flux and 101 % in average heat transfer with increasing magnetic field intensity. The findings establish proof of concept of applying magnetic field to augment film-based cooling. [ABSTRACT FROM AUTHOR]

The information on downward longwave (LW) radiation is necessary for the design of the passive cooling system of buildings. Because the measured LW radiation data are not available in most locations, few studies have focused on the modeling of LW radiation in China. In this study, empirical models for estimating LW radiation were proposed under all-sky conditions based on the meteorological parameters such as the ambient dry-bulb temperature, water vapor pressure, and relative humidity, which can be classified into four cases: All day, nighttime, and daytimes with and without considering the cloud modification factor. The proposed models performed are well compared with the existing models. The LW radiation datasets for 351 locations of China were developed using the proposed model for all the day based on the typical meteorological year. Moreover, the distribution map of radiative cooling potential in July was created using the proposed model for the nighttime, which can provide a valuable reference for building cooling design. [ABSTRACT FROM AUTHOR]

Integrating evaporative cooling with loop thermosyphon can significantly improve the free cooling ability. In this paper, a loop thermosyphon with evaporative condenser is investigated experimentally. The mist water flow out of a single nozzle is observed and analyzed. The performance and annual free cooling potential of the system are investigated, compared with conventional loop thermosyphon. The results show that the evaporative cooling effect of the locations below the horizontal level of the nozzle is more significant due to gravity. With the increase of horizontal distance from the nozzle, the temperature decreases and then increases and the optimal distance is 200–400 mm. The heat capacity of LTEC increases with the increase of indoor and outdoor temperature difference while it decreases with the increase of humidity. Evaporative cooling can enhance the heat transfer of LTEC by 7%–33% compared with loop thermosyphon with conventional condenser, and this value is larger for smaller indoor and outdoor temperature difference and higher indoor temperature. LTEC can expand the annual free cooling time by 7%–14% compared with LTCC and the effect is more significant in regions with drier weather. • Loop thermosyphon with evaporative condenser (LTEC) is studied experimentally. • Temperature field and flow field of the water spray out of a single nozzle are analyzed. • The distance with the best evaporative cooling effect is 200–400 mm from the nozzle. • The heat transfer of LTEC is 7%–33% larger than LTCC. • The annual free cooling time of LTEC is 7%–14% larger than LTCC. [ABSTRACT FROM AUTHOR]