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Microchannel heat exchangers find widespread use in household and automotive air conditioning due to their compact structure and high efficiency. However, two-phase refrigerant flow mal-distribution in microchannels limits their application. For the CO2 heat pump, the performance reduction by flow mal-distribution could be as large as 20%. This study proposed an approach to mitigate flow mal-distribution by inserting a perforated tube into the header of a microchannel evaporator in CO2 heat pump. Numerical simulations were carried out to investigate the impact of perforated tube parameters and CO2 inlet conditions on flow distribution. Results show a 24.4% increase in total non-uniformity (S) of flow distribution with a perforated tube. A higher number of openings and smaller diameters enhance uniformity, with the 10-hole, 2 mm diameter perforated tube proving most effective. Additionally, the most uniform flow distribution was achieved at an inlet CO2 mass flow rate of 30 g/s and a vapor quality of 0.2. And the flat tubes with an insertion depth of 5 mm and a cross-section of 16 × 2 mm is the most beneficial for uniform flow distribution. [ABSTRACT FROM AUTHOR]

The performance merits of a mobile air conditioning (MAC) system with an orifice tube (OT) were experimentally evaluated for R1234yf relative to R134a. The effect of employing a suction/liquid line internal heat exchanger (HEX) was also investigated for R1234yf. To this end, an experimental unit employing the components of an R134a MAC system was set up, equipped with a coaxial internal HEX, and tested at various compressor speeds for both refrigerants. The air temperatures entering the condenser and evaporator were simultaneously maintained at 30, 35, and 40 °C. The R1234yf unit provided on average 22.5% lower and 6.9% higher cooling capacity than the R134a unit for the inactive and active HEX, respectively. Furthermore, the coefficient of performance (COP) for the R1234yf unit without and with HEX was on average 10.9% and 3.5% lower than that for the R134a unit, respectively. The R1234yf unit without and with HEX yielded on average 41.5% and 8.4% lower exergetic efficiency than the R134a unit, respectively. These results revealed that the use of an internal HEX in an R1234yf MAC unit with an OT compensates for the cooling capacity degradation, and the R1234yf unit has almost as high performance as the R134a unit. [ABSTRACT FROM AUTHOR]

Integration of a reversal multistage flash (RVMSF) and multi-effect evaporators (MEE) desalination technologies driven by waste heat source is studied. The warm RVMSF reject brine is used as a sensible heat source for the MEE process. Three different configurations are compared and proved to outperform the standalone MSFRV system. Based on the best hybrid structure, 69 %, 67 %, and 287 % enhancement in the recovery ratio, the specific energy consumption (SEC), and the gain output ratio (GOR), respectively over the standard RVMSF process were observed. However, this was achieved at the expense of a 46 % increase in the specific heat transfer area. The recovery ratio, specific area, SEC, and GOR were found to improve with primary feed temperature, and temperature drop of the sensible heat powering the MEE. However, for a fixed number of effects, the full leverage of the supplied energy is limited causing variable or slow progress of the key performance indicators. Increasing the number of MEE effects had a positive effect on the performance causing proportional growth of the recovery ratio and GOR. A maximum value of 20.2 % for the recovery ratio and 5.7 for the GOR was observed when ten effects were used in the MEE system. [ABSTRACT FROM AUTHOR]

A kirigami-engineered composite hydrogel membrane is exploited for the construction of three dimensional (3D) solar-tracking evaporator arrays with outstanding evaporation performance and salt tolerance. The hybrid nanofiber network in the hydrogel membrane offers favorable water transport dynamics combined with excellent structural robustness, which are beneficial for the engineering of 3D dynamic structures. Periodic triangular cuts patterned into the membrane allow formation and reconfiguration of 3D conical arrays controlled by uniaxial stretching. With these structures, the tilt angles of the membrane surface are actively tuned to follow the solar trajectory, leading to a solar evaporation rate ~80% higher than that of static planar devices. Furthermore, the tapered 3D flaps and their micro-structured surfaces are capable of localized salt crystallization for prolonged solar desalination, enabling a stable evaporation rate of 3.4 kg m-2 hour-1 even in saturated brine. This versatile design may facilitate the implementation of solar evaporators for desalination and provide inspirations for other soft functional devices with dynamic 3D configurations. [ABSTRACT FROM AUTHOR]

Intermittent sunlight irradiation severely limits the performance of solar evaporators for electricity output and freshwater production. To address this issue, a hierarchical‐structured three‐dimentional (3D) solar evaporator to simultaneously enhance output voltage and freshwater production by integrating a paraffin‐type phase change material (PCM) with a circular concave‐shaped 3D supporter covered with a carbon‐black‐nanoparticles‐modified poly(ethylene terephthalate) fabric (PMCB) is developed. In this developed 3D solar evaporator, the 3D‐printed supporter can trap sunlight to improve solar energy absorption, and the PMCB obtained from hydrophilic and hydrophobic modification can adequately absorb sunlight for electricity generation and water evaporation, resulting in a maximum output voltage of 3.51 V and a high evaporation rate of 4.0 kg m−2 h−1 under natural sunlight illumination. Owing to the introduction of the PCM, the 3D solar evaporator obtains a decrease in the time required for charging a capacitor by 57.9% and an increase in freshwater production by 29.9% compared to the counterpart without a PCM. Through rationally utilizing the solar photothermal energy stored by the PCM and innovatively integrating the PCM and PMCB in a hierarchical‐structured 3D supporter, the developed 3D solar evaporator exhibits great application potential for simultaneous electricity generation and freshwater supply under intermittent solar irradiation. [ABSTRACT FROM AUTHOR]

Bi-porous evaporator for heat pipes has been studied to replace conventional mono-porous evaporators with lower thermal capacity. The thermal superiority of bi-porous evaporator is a direct function of phase separation phenomenon in small and large-pore zones. However, due to the microscale nature of the system the hidden microscopic phenomenon associated with thermal superiority has not been well established experimentally. In addition, only a few numerical studies have addressed this phenomenon using limited information. In this paper, a two-dimensional numerical simulation is conducted which accurately predicts the thermal performance of a bi-porous evaporator. Additionally, for the first time, several microscopic phenomena such as phase separation, vapor blanket formation, and liquid film formation are numerically reproduced. Thus, the thermal performance of bi-porous evaporator is successfully quantified. The effects of various design parameters are also studied and their effect on thermal performance is also quantified. For comparison, a mono-porous evaporator is also simulated. [ABSTRACT FROM AUTHOR]

The article presents the results of studies of the parameters of a new flat aluminum thermosyphon, the evaporator of which contains two identical parallely operating panels, each of which has 8 minichannels. The panels are united by single vapor and liquid collectors. The working fluid is acetone. A study was carried out to investigate the influence of a thermal load and the degree of thermosyphon filling with working fluid on the heat exchange coefficients of the evaporator and condenser, as well as on the thermal resistance of the thermosyphon. [ABSTRACT FROM AUTHOR]

Solar desalination using hydrogel evaporators is an eco‐friendly, highly efficient means with natural sunlight for sustainable freshwater production. However, it remains challenging to develop a cost‐effective and scalable method to prepare salt‐resistant hydrogel evaporators for stable desalination. Here, inspired by tree transpiration and hierarchical porous structure, a 3D‐printed bionic hydrogel evaporator (3DP‐BHE) is designed for long‐term solar desalination. Commercialized activated carbon (AC) is introduced into biomass starch skeleton as a solar light absorber to build 3DP‐BHE in a cost‐effective fashion ($10.14 m−2 of total materials cost). The bionic tree leaf layer for 94.01% light absorption and timely vapor diffusion. The bionic tree trunk layer with 3D printed bimodal porous structure for water transfer, thermal isolation, and salt ions convection and diffusion. With the unique bionic structure, the 3DP‐BHE achieves a stable evaporation rate of 2.13 kg m−2 h−1 at ≈90.5% energy efficiency under one sun (1 kW m−2). During the 7‐day desalination of 10 wt.% brine, a steady evaporation rate of 1.98 kg m−2 h−1 is maintained with a record‐high cost‐effectiveness (195.3 g h−1 $−1) manner. This 3DP‐BHE will open significant opportunities for affordable solar desalination systems on multiple scales, from individual households to off‐grid communities. [ABSTRACT FROM AUTHOR]

The performance of an ejector-assisted condenser outlet split dual-evaporator cycle is compared with a conventional dual-evaporator cycle albeit consisting a pressure reducing valve. The cycles do not employ any separator due to its inability to efficiently separate the liquid and the vapor phases. The comparison of both the cycles has been made for the same cooling capacity in low-temperature evaporator and unit flow rate of R134a and R1234yf as refrigerants. The impacts of changing the operating temperatures of evaporator and condenser have been examined in the current investigation. The study reveals that with the increase in temperature of the high-temperature evaporator, the cooling capacity of the high-temperature evaporator yields, while that of the low-temperature evaporator plummets in both the cycles. Further, the compressor work is allayed in the ejector-assisted cycle; thus, the COP is enhanced considerably. The percentage COP improvement over the basic cycle is obtained from 14.7 to 17.53% for the refrigerant R1234yf and from 14.45 to 17.32% for R134a; however, the COP of both the cycles with R12134yf is slightly lower than with R134a. The ejector has been modeled assuming a constant pressure theory. The observed trend indicates that the entrainment ratio is improved with the rise in the temperature of low-temperature evaporator, whereas it is decreased with the rise in the temperature of high-temperature evaporator. [ABSTRACT FROM AUTHOR]

[Display omitted] Solar-driven desalination is an environmentally sustainable method to alleviate the problems of freshwater scarcity and the energy crisis. However, how to improve the synergy between the photothermal material and the evaporator to achieve high photothermal conversion efficiency simultaneously, excellent thermal management system and good salt resistance remains a challenge. Here, a mushroom-shaped solar evaporation device is designed and fabricated with iron diselenide/carbon black (FeSe 2 /CB) coated cellulose acetate (CA) film as mushroom surface and cotton swab as mushroom handle, which presented high solar-driven evaporation and excellent salt resistance. Thanks to the unique photothermal effect and the synergistic effect, the FeSe 2 /CB composites enabled a promising photothermal conversion efficiency of up to 65.8 °C after 180 s. The mushroom-shaped evaporation device effectively overcomes water transport and steam spillage channel blockage caused by salt crystallization through its unique vertical transport water channels and conical air–water interface. When exposed to real sunlight, the solar evaporation rate of the steam generation structure reached as high as 2.03 kg m−2 h−1, which is more than 13 times higher than natural evaporation. This study offered new insights into the higher solar-driven evaporation rate and salt-blocking resistance of the FeSe 2 /CB mushroom-shaped solar evaporation device for solar-powered water production. [ABSTRACT FROM AUTHOR]

• A vapor-liquid adjustment evaporator is pioneered to heat pump water heater. • Serials experiments are conducted for performance comparisons. • Current vapor-liquid adjustment evaporator cannot ensure its superiority for each period. • A 6.35 % higher COP and 16.18 %−63.37 % lower evaporator pressure drops are found. Adjusting vapor and liquid in the evaporator could lead to heat transfer enhancement and pressure drop reduction simultaneously. Its benefits in the steady system, such as air conditioning and heat pump, have been confirmed extensively, but its effectiveness in the dynamic system is not explored yet. In this paper, a vapor-liquid adjustment evaporator is implemented to heat pump water heater (HPWH-AE) featured by a dynamic water heating process. Comprehensive comparisons to the heat pump water heater with a conventional evaporator (HPWH CE) are experimentally investigated and discussed. Firstly, the matching test reveals that the optimized HPWH-AE has a 6.35 % higher COP than HPWH CE. Secondly, the detailed comparisons indicate that HPWH-AE has less evaporator pressure drop, smaller compressor ratio, higher refrigerant mass flowrate and decreased power consumption than HPWH CE. Thirdly, the divided tests are carried out with an increment of half hour. The results suggest that HPWH-AE outperforms HPWH CE in terms of heating capacity and COP at the first one and half hours, which becomes inferior afterwards. However, HPWH-AE has always lower power consumption relative to HPWH CE. The images from FLIR camera show that the vapor-liquid adjustment evaporator is featured by effectively utilizing heat transfer area, resulting from more evenly distributed temperatures. Finally, the feasibility is examined at various operating conditions. HPWH-AE could have higher heating capacity and lower power consumption than HPWH CE simultaneously when ambient temperature is between 18 °C and 26.5 °C. HPWH-AE always has higher COP of 4.92–6.35 % than HPWH CE. [ABSTRACT FROM AUTHOR]

Conventional heat pipes with one evaporator and one condenser are used to cool only one heat source at a time. In electronics and space applications, where a large number of heat sources are to be cooled with limited space available, a multi branch heat pipe could be the solution. In the present study, a heat pipe (T-shape) with three branches was developed with 20 number of axial grooves in which two branches worked as evaporators and one branch as a condenser. Experimental study was performed by considering four novel types of orientations i.e. (a) horizontal orientation (HO) (b) gravity assisted orientation (GAO) (c) anti-gravity orientation (AGO) and (d) compound orientation (CO). The results are analyzed in terms of start-up characteristics and total heat transfer coefficient at different heat loads. Evaporator and condenser thermal resistances are calculated and analyzed for better understanding. It was found that horizontal orientation resulted in the highest overall heat transfer coefficient (2.72 kW/m2 ℃ at 240 W) and comparatively lower evaporator temperatures (less than 100 ℃ at 240 W) which is suitable condition for electronics cooling. Maximum effective thermal conductivity of 31.82 kW/m ℃ was achieved in horizontal orientation. It also resulted in lowest evaporator resistance (0.157 ℃/W) and lowest condenser resistance (0.114 ℃/W). Phenomena of temperature jump was observed and elaborated for compound orientation. [ABSTRACT FROM AUTHOR]

This paper researches the heat transfer equation and thermal balance equation of a shell-and-tube evaporator; constructs an accurate mathematical model for the evaporator; and derives equations including detailed and accurate calculation methods for all heat transfer coefficients, such as the refrigerant side heat transfer coefficient, water side heat transfer coefficient, refrigerant kinematic viscosity, density, and specific enthalpy. Adopting this approach involves fitting the relationships between the density, thermal conductivity, kinematic viscosity, and enthalpy of R134a refrigerants in saturated vapor and liquid states. The relationships between superheated gas enthalpy, density, and temperature were also assessed, and heat transfer coefficients were obtained through calculation methods and microelement heat transfer relationships in both the single-phase and two-phase zones, matching empirical formulas concerning the relationship between superheated enthalpy and temperature. Notably, the research utilizes the Simulink approach without relying on M files and S functions to establish the evaporator's two-phase and superheated zones, as well as an overall simulation model which provides intuitive internal coupling relationships and the coefficient calculation process in the formulas and uses the function "Algebraic Constraint" instead of "memory" or "1/z" to solve algebraic loops, thereby avoiding computation deviations introduced by delays and iterations. Finally, simulation calculations were conducted, and an experimental platform was designed and built for experimental verification which can validate the derived mathematical models. The simulation results, including the evaporator pressure, and chilled water outlet temperature with variation in chilled water mass flow rate, closely matched the experimental outcomes. The simulation model is concise and intuitive. Modifying parameters such as the thermal conductivity of the model material is straightforward, thereby alleviating the workload for researchers. It also facilitates an understanding of model principles for beginners. Moreover, the database generated from the model allows for fault analysis, diagnosis, and decision evaluation. [ABSTRACT FROM AUTHOR]

A novel Loop Heat Pipe (LHP) is developed as passive cooling system for Battery Thermal Management System (BTMS). LHPs are more efficient than traditional heat pipes at transferring heat at larger distances, which is essential for keeping the batteries in a safe and efficient temperature range. The Single Evaporator Loop Heat Pipe (SE-LHP) BTMS is tested on a battery module comprising of twelve 18,650 lithium-ion battery cells. The tests are conducted at various charge and discharge rates (1C, 1.5C, and 2C) and ambient temperatures ranging from 30°C to 45°C. The SE-LHP BTMS significantly reduces the maximum cell temperature compared to a module without BTMS. At an ambient temperature of 35°C, the SE-LHP BTMS attains temperature drops of 15%, 16.4%, and 16.29% during battery charge rates of 1C, 1.5C, and 2C, respectively. The SE-LHP BTMS also increases the discharge capacity of the battery module. For the 1.5C discharge rate, the discharge capacity increases from 41% State of Charge (SOC) to 0% SOC with the SE-LHP BTMS, compared to 39% SOC without BTMS. For the 2C discharge rate, the discharge capacity increases from 59% SOC to 0% SOC with the SE-LHP BTMS, compared to 56% SOC without BTMS. The SE-LHP BTMS also helps to keep even temperature spreading among the battery cells. When the module is exposed to ambient temperatures ranging from 30°C to 45°C, the SE-LHP BTMS keeps a temperature difference of less than 2.43°C and 3.38°C among the battery cells for all charge and discharge rates, respectively. [ABSTRACT FROM AUTHOR]

Solar steam generation to generate steam through solar light-driven surface evaporation can be an attractive methodology that utilizes green and inexhaustible solar energy to generate water steam and fresh water with superior efficiency. However, some drawbacks of the current photothermal conversion materials such as complicated fabrication process, high cost, and low salt tolerance often heavily restrict their wide applications. Herein, a green and low-cost method is designed and developed for constructing a free-standing, elastic, and highly tough 3D network of carbon nanotubes (CNTs) and MXene through an efficient "egg-box" coordination mechanism in only one step for high-efficiency water evaporation. When the mass ratios of MXene and CNTs are designed at 1:1.5 and cross-linked with sodium alginate and CaCl2, the obtained MCS-3 shows the most excellent light absorption and hydrophilicity, leading to the best evaporation rate of 1.644 kgm-2 h-1, and the highest photothermal conversion efficiency of 96%. Moreover, subject to different harsh environments and durability tests, MCS-3 also shows desired structural stability and evaporation performance. As demonstrated by its extraordinary photothermal evaporation properties, MCS-3 can envision a wide range of commercial applications covering wastewater purification, brine seawater, desalination, etc. [ABSTRACT FROM AUTHOR]

A steam-gas power plant (SGPP) combines a gas power plant (GPP) and a steam power plant by using the exhaust gas from the GPP to produce steam in the heat steam recovery generator (HRSG). The SGPP, which has a 200 ton/h HRSG capacity, experienced cracks, ruptures, and fatigue at the connection of the low-pressure evaporator pipe. Fatigue is a common failure mechanism in mechanical components due to thermal stress. However, the exact cause of the failure was unknown; therefore, a root cause analysis was conducted. Analysis included the thickness, metallography, chemical composition, tensile testing, thermography, defect testing, and hardness testing. The research showed thermal stresses were the cause of the low-pressure evaporator HRSG pipe failure. In addition, inspection results revealed a decrease in tensile strength, material hardness, and thermal expansion that exceeded the allowed limit. [ABSTRACT FROM AUTHOR]

Interfacial solar vapor evaporation is expected to be an emerging technology to solve the scarcity of freshwater due to its sustainability and high efficiency. However, the present application of evaporators is mainly limited by the complex preparation process, expensive cost of raw material, and poor structure. Herein, based on coconut shell activated carbon (CSC) and ultrahigh molecular weight polyethylene (UHMWPE), a cost‐effective and robust CSC/UHMWPE (CSC/PE) evaporator is prepared through sintering in a mold. Benefiting from high light absorptance (≈90%) and excellent thermal localization, the CSC/PE evaporator exhibits an evaporation rate of 1.340 kg m−2 h−1 and an evaporation efficiency of 80.57% in 3.5 wt% brine under 1 sun irradiation. Moreover, by regulating the component ratios, the CSC/PE evaporator achieves superhydrophilicity and proper water transportation rate, and shows long‐term stability with an average evaporation rate of 1.309 kg m−2 h−1 in natural seawater for 10 h. Specifically, the high porosity CSC/PE facilitates the salt resistance in high salinity brine (15 wt%). Importantly, the cost‐effectiveness of CSC/PE is 53.43 g h−1 $−1, which is economical compared to other reported evaporators. Therefore, the economical, simple‐to‐prepare, and durable CSC/PE evaporator has enormous potential in interfacial solar vapor evaporation for freshwater production. [ABSTRACT FROM AUTHOR]

The paper presents the results of measurements carried out in the GTM400 turbojet engine with a changed combustion chamber geometry. The available publications lack more detailed information on the temperature distribution in evaporators, which are part of the combustion chamber of small turbojet engines. As the results of the analysis showed, this is not simple, because the research takes place in very small spaces. The reason for the work carried out is to check whether the temperatures in the evaporators are high enough. This allows to determine whether the fuel is evaporating properly. Therefore, an analysis was carried out to determine the temperature distribution in the area of the inlet to the evaporator. Thanks to the modification of the combustion chamber, it was possible to measure temperatures, which in the engine literature are simulated using numerical analysis. The analysis described in the paper is one of the stages of preparing the engine for operation with hydrogen. It is modified as part of a project to build a hybrid engine burning traditional JET-A1 fuel and alternative fuel, i.e. hydrogen. [ABSTRACT FROM AUTHOR]

This article was to study vaporization phenomena in a flat gravity heat pipe (GHP) with a threaded evaporator in the active boiling mode. For this purpose, a flat GHP with a threaded evaporator was made with the following parameters: length—245 mm; cross-sectional dimensions—15.5 mm × 4 mm; length of the evaporative threaded section—40 mm; threaded pitches 0.5 mm. A window measuring 9.5 mm × 240 mm covered with a hermetically sealed sight glass was made in the upper face of the heat pipe. Ethanol was used as the working fluid. The heater was powered at 50 W. The condenser section was cooled by forced air convection. The authors visually observed and analyzed the specific features of boiling at 6 different tilt angles (90°, 75°, 60°, 45°, 30° and 15°) and showed the effect of tilt angle of a flat GHP with a threaded evaporator on its thermal performance. The study determined the effect of tilt angle on the temperature distribution along the heat pipe, the average temperature in the heating zone, thermal resistance and heat-transfer coefficients. It was found that in the heating zone, the temperature did not exceed 67 °C, while the lowest value of thermal resistance, 0.295–0.3 °C W−1, was observed at the tilt angles of 75–90°. A comparison of the thermal performance of flat GHPs with threaded and bare evaporators showed an improvement in the thermal performance of a flat GHP with a threaded evaporator compared to a bare evaporator. The results of the study show good prospects for the use of inexpensive flat gravity heat pipes with a threaded evaporator for electronic equipment cooling systems. [ABSTRACT FROM AUTHOR]

Energy, cost, and environmental concerns play a vital role in understanding governing parameters of distributor design in falling film evaporators. Distributor design is a hidden parameter in many experimental papers. The uniform distribution of liquid refrigerant over the tube bundle mostly depends on two‐phase liquid refrigerant and vapor refrigerant. This work conducted experiments with two distribution systems with and without separation of liquid‐vapor refrigerant after expansion valve for the same evaporator capacity with R134a as a refrigerant. Results reveal that; separating vapor refrigerant has a positive impact on the approach of the evaporator with an open system distributor arrangement. The highest delta T and lowest practice are found at a heat flux of 13.97 kW/m2 with an available system distributor compared to a closed system with a heat flux of 14.25 kW/m2. The open system arrangement in the distributor is the novel parameter for distributor design, ensuring uniform distribution with minimum pressure drop and dry suction. An open system distributor has an average 16.1% capacity increase over a closed system. The experimental analysis helps to understand different parameters for the design of distributors in falling film evaporators for uniform distribution. [ABSTRACT FROM AUTHOR]

To improve the performance of conventional double-effect absorption refrigeration systems (DEARS), new series parallel (SP) and reverse parallel (RP) configurations using LiCl-H2O and LiBr-H2O as working fluids, combined with two vapor compressors (VC), are proposed and thermodynamically evaluated. The effects of the distribution ratio (D) and compression ratio (CR) on the system performance are discussed. The results reveal that both configurations can extend the operation ranges of DEARS effectively at a higher distribution ratio, and the performance for low-grade heat source utilization is improved substantially by the use of VC. The compressor positioned between the evaporator and absorber is superior to that between the high-pressure generator and low-pressure generator because of the better performance improvement and larger operating ranges. In all the examined cases, LiCl-H2O systems perform better than LiBr-H2O systems in terms of the coefficient of performance (COP) and exergetic efficiency. At the higher CR of approximately 2, the compression-assisted DEARS can be driven by heat sources below 100 °C with high levels of COPs above 1.16 for the LiBr-H2O working pair and 1.29 for the LiCl-H2O working pair. The system can operate at the optimum condition by adjusting the CR values according to the characteristics of the heat sources. [ABSTRACT FROM AUTHOR]

There is a growing demand from the industrial sector and the population to cover the need for water temperature increases that can be covered with systems such as heat pumps. The present research aims to increase the heat transfer to the working fluid in a collector/evaporator, part of a solar-assisted direct expansion heat pump. This research was developed using a numerical analysis and by applying computational fluid dynamics; different simulations were performed to compare the performances of collector/evaporators with models exhibiting variations in the cross-section profile under similar conditions. An average incident solar radiation of 464.1 W·m−2 was considered during the analysis. For the comparison, profiles with hexagon-, four-leaf clover-, and circular-shaped sections with floral shapes, among others, were analysed, resulting in a temperature increase at the outlet of the working fluid of 1.3 °C. In comparison, the collector/evaporator surface temperature varied between 4 and 13.8 °C, while the internal temperature of the fluid reached 11.21 °C. Finally, it is indicated that the best results were presented by analysing the profile corresponding to the circular section with the flower shape. [ABSTRACT FROM AUTHOR]

The expansion device is the critical component of micro-to-small scale organic Rankine cycle (ORC) systems, substantially affecting system efficiency and cost. Low isentropic efficiency and lubrication requirements are the main issues associated with using volumetric expanders in ORC systems. Despite lubrication contributing to reducing internal leakages in an expander, it may compromise the performance of the ORC system by adversely affecting the evaporator's thermal capacity. This study tests a recently developed and modified revolving vane expander (M-RVE) in a micro-scale ORC test rig by implementing an adjustable oil mass flow rate. The impact of the lubricant oil on the performance of the M-RVE prototype is investigated within a wide range of oil circulation rates (OCR). The results demonstrate a negligible improvement in the filling factor for OCRs higher than 1%. Moreover, the shaft power is not considerably sensitive to OCR, while the calculated isentropic efficiency of the expander improves with OCR. Furthermore, the impact of the lubricant oil on the performance of the evaporator is studied, assuming the exact OCR as the expander and measured temperature and pressure similar to the pure refrigerant for the lubricant-refrigerant mixture in the evaporator. The study shows that the evaporator capacity is penalized with OCR, especially for values higher than 1%. Hence, an OCR of about 1% is a good compromise, and it can be used as a guideline for designing revolving vane expanders for micro-scale ORC systems without a dedicated lubricant oil circuit. [ABSTRACT FROM AUTHOR]

In this study, visualization treatment was applied to the flat disk-shaped evaporator of a loop heat pipe. By observing the liquid/vapor behavior inside the evaporator and compensation chamber, the effects of orientation on the performances during startup and during a step-increase in heat load were investigated. With water as the working fluid, the loop heat pipe was tested under three typical orientations of φ = −90°, φ = 0°, and φ = +90°. The startup time was the shortest for the φ = −90° orientation but there could be a slight temperature overshoot, resulting in an unsmoothed startup process. The startup speeds under the φ = 0° and φ = +90° orientations were similar, both without any significant temperature overshoot. The orientation could significantly change the heat leak and, therefore, the operating temperature and the heat-transfer limit. For the φ = +90° and φ = −90° orientations, the heat-transfer limits were about 71% and 157% of the value at the φ = 0° orientation, respectively. Based on visual observations, for the loop heat pipe operating in gravity-driven mode, there could be two different paths for the working fluid to return to the evaporator, namely, along the vapor line for low heat loads and along the condenser and liquid lines for relatively large heat loads, respectively. [ABSTRACT FROM AUTHOR]

Interfacial solar-driven steam generation is one of the most promising techniques used to produce clean water. However, achieving rapid water evaporation using solar steam generation devices is challenging because of their two-dimensional (2D) planar structures and confined evaporation areas. The three-dimensional (3D) structural design of evaporation devices improves water evaporation rates, thereby enhancing solar-driven steam generation. This study developed a 3D wood-based evaporator through 3D structure shaping and the flexible treatment of wood that involved coating photothermal materials with tannic acid. Because of the ampliative evaporation area and outstanding absorption, the water evaporation rate of the prepared 3D wood-based evaporator was as high as 2.5 kg m−2 h−1, and the efficiency of energy transformation was up to 101 % under simulated 1-sun irradiation; the evaporation rate and efficiency of energy transformation were considerably higher than those of 2D planar wood evaporators. Furthermore, the effective seawater desalination performance and good durability of the 3D wood-based evaporator were demonstrated. This study provides different insights into the fabrication of high-efficiency wood-based solar steam generators with high prospects for application in seawater desalination. [ABSTRACT FROM AUTHOR]

The current research combines a dual evaporator vapour-compression refrigeration system with an organic Rankine cycle. The integrated system is a renewable energy-based technology that can provide refrigeration at different refrigeration temperatures and capacities. The system's performance is compared using five different organic working fluids: butane, pentane, isopentane, hexane, and R245fa, to recommend the most suitable fluid for the system. Coefficient of performance (COP), exergy efficiency (η ex), total cost (C tot), and payback period (PB) are taken as the performance parameters. Moreover, the system's exergy performance is analysed using advanced exergy analysis (AEA), and sensitivity analysis to determine the optimal operating condition for system components. The result indicates that butane is the optimal fluid for improving energy, exergy, economical, and environmental performance. The system has a COP of 0.377, an exergy efficiency of 10.91%, a total cost of $33,091, and a payback period of 5.8 years. Boiler, compressor, condenser, and EPG make up 31% of the total exergy destruction that can be avoided by adequately selecting their operating condition. The optimal condition for boiler temperature, condenser temperature, the pinch-point temperature difference in condenser and boiler, and compressor efficiency is 120 °C, 40 °C, 3 °C, 10 °C, and 0.7, respectively. [ABSTRACT FROM AUTHOR]

Recently, the development of environmentally friendly refrigerants has emerged as a major issue in industry. Owing to the high cost of developing new refrigerants, falling-film evaporators are attracting increasing interest, given their reduced refrigerant usage compared with flooded evaporators. In falling–film evaporators, the distributor at the top of the evaporator uniformly delivers refrigerant through multiple holes over heat transfer tubes. We focus on the liquid (refrigerant) behavior in the distributor of a falling-film evaporator. To understand the underlying mechanism, we perform experiments on single hole as well as multiple holes in the distributor. For both cases, we have derived theories that predict the refrigerant height in the distributor, according to the flow rate. They show good agreement with the experimental measurements. By changing the hole diameter, number of holes, and flow rate, we quantitatively characterize parametric dependencies that determine the liquid behavior. In addition, we unveil a negative effect of the supply stream from the upper distributor that locally mitigates the outflow rate from the distributor. [ABSTRACT FROM AUTHOR]

Highlights: Hybrid fibrous aerogels with tunable wettability from the same molecular unit of vinyltrimethoxysilane are successfully developed. Superhydrophobic and superhydrophilic hybrid aerogels are integrated into a double-layered evaporator, showing robust interfacial networks to withstand repeated and tremendous compression for 1000th cycle. The evaporator delivers high water evaporation rates of 1.91 kg m−2 h−1 under laboratory conditions and 4.20 kg m−2 h−1 under outdoor experiments with the aid of wind (1 sun), enabling efficient salt rejection under continuous operation. Solar-driven interfacial evaporation is an emerging technology for water desalination. Generally, double-layered structure with separate surface wettability properties is usually employed for evaporator construction. However, creating materials with tunable properties is a great challenge because the wettability of existing materials is usually monotonous. Herein, we report vinyltrimethoxysilane as a single molecular unit to hybrid with bacterial cellulose (BC) fibrous network, which can be built into robust aerogel with entirely distinct wettability through controlling assembly pathways. Siloxane groups or carbon atoms are exposed on the surface of BC nanofibers, resulting in either superhydrophilic or superhydrophobic aerogels. With this special property, single component-modified aerogels could be integrated into a double-layered evaporator for water desalination. Under 1 sun, our evaporator achieves high water evaporation rates of 1.91 and 4.20 kg m−2 h−1 under laboratory and outdoor solar conditions, respectively. Moreover, this aerogel evaporator shows unprecedented lightweight, structural robustness, long-term stability under extreme conditions, and excellent salt-resistance, highlighting the advantages in synthesis of aerogel materials from the single molecular unit. [ABSTRACT FROM AUTHOR]

This study presents an entropy analysis of the losses in different sections of a central air conditioner. The methodology for determining the losses using entropy analysis is presented in this work. The temperature and humidity of the outside and recirculating air were measured, and losses due to mixing of air flows, cooling in the evaporator section, and heating in the condenser section were calculated. A comparative analysis of the results was performed, and the distribution diagrams of the component losses were presented. Conclusions regarding a loss-reduction method were proposed. [ABSTRACT FROM AUTHOR]

The nanostructure of materials plays a key role in interfacial solar vapor generation. Traditional approaches for optimizing interfacial evaporation rely on the external devices to enable floating on water. However, how to unlock the self-floating ability of absorbers for solar interfacial evaporation have not been taken into account. Here, we propose a self-floating absorber based on kapok fibers, which possess large hollow structure and hydrophobicity to enable this absorber float on water without assistance. Gold nanoparticles (AuNPs) were loaded on kapok fibres by in-situ synthesis and showed an extended adsorption (74.7%) wavelength ranging from 280 to 2500 nm. Both the hollow structure of kapok fibres and the thermal localization effect of AuNPs sustaintially enhance the solar interfere vapor generation effect (4 kW m−2, up to 89%). Also, Each cycle test was carried out under 1 h irradiation. The AuNPs/kapok membrane exhibited stable cycling performance, which maintained an evaporation rate of 6.98 kg m−2 h−1 over 10 times without performance decrease. These results provide new insights for design of advanced photothermal conversion materials with biomass as supporting material, We expect this as-prepared membrane can be used for a range of applications, such as solar interference steam generation, desalination and disinfection, to name a few. [ABSTRACT FROM AUTHOR]

• A dynamic model of a falling film water evaporator with recirculation is presented. • The evolution of wetted area is characterized via experimental tests. • The wettability factor is correlated to film Reynolds and Prandtl numbers. • The model can be integrated in the dynamic simulation of adsorption cycles. The objective of the present study was to develop a dynamic model to simulate a prototype falling-film evaporator that is part of a single-bed adsorption chiller test bench located at the Department of Energy of the Politecnico di Milano. The model is based on the evaporator energy and mass balances and was calibrated and validated using experimental data coming from realistic operating conditions in a range of inlet chilled water temperatures (T i n , c h w) from 15 to 25°C. From the experimental data, it was obtained that the average overall heat transfer conductance (U A) was approximately 530 W/K for all temperatures during the quasi steady-state section of the process. A correlation to calculate the wetted surface through a variable called wettability factor (f w e t) was developed from experimental data. The f w e t factors were identified using the model and were in the range of 0.80 – 0.20 (T i n , c h w = 15°C) and 0.60 – 0.20 (T i n , c h w = 25°C). It was seen that, the higher the T i n , c h w , the lower the f w e t values. The U A and saturation temperature (T r e f , s a t) values from the model were in good accordance with experimental data during the quasi steady-state section of the process. Nevertheless, the final transition stage (i.e., a situation in which the evaporator's refrigerant pool is empty) required an additional hypothesis due to the uncertain process' dynamics. The mass and energy balances that are part of the hydrodynamics and heat transfer sections of the model use Nusselt's classic theory for falling-film. [ABSTRACT FROM AUTHOR]

• A quantification method is proposed to calculate the flow rate distribution of microchannel heat exchangers. • Liquid and vapor mass flow rates are calculated with the method, and it shows how refrigerant is distributed in the inlet header. • The potential of improving the heat capacity of the evaporator with uniform distribution is calculated and discussed. Maldistribution of fluid among the ports reduces the heat capacity of a microchannel heat exchanger. It is essential to understand the maldistribution mechanism to optimize the design of the heat exchanger. Quantification of the distribution helps analyze the maldistribution issue. This study proposes a method to quantify the flow distribution and capacity potential in the microchannel heat exchangers by integrating a microchannel heat exchanger model and infrared thermography. The method calculates the liquid and vapor mass flow rate at the inlet of each microchannel tube by comparing the wall temperature of a heat exchanger from simulation and the infrared image. The method is validated with tests of a 49-tube horizontal microchannel evaporator with R134a. The exit region of the top tubes has an extremely high surface temperature, which forms a superheat region. More liquid flows to the tubes located at the center of the heat exchanger. The total mass flow rate is low when the tube has a long superheat region. The heat capacity of the tested evaporator has 9.6–21.3% improvement potential when uniformly distributed. When the refrigerant outlet superheats of the evaporator is lower, the improvement potential is higher. In the superheat region, the heat flux is much lower than the average value. This quantification method provides a tool for a more profound investigation of the maldistribution issue of a microchannel evaporator, and it can be expanded to heat exchangers with different structures. [ABSTRACT FROM AUTHOR]

• Systematic investigation of liquid flooding upon compressor start-up. • Characteristic flooding curve shown for 12 combinations of heat exchangers and refrigerants. • Correlation proposed capturing influence of heat exchanger size and refrigerant properties. Refrigeration cycles with fixed speed compressors cycle on and off to modulate their time averaged cooling capacity. While the cycles are turned off, refrigerant can migrate from the condenser into the colder evaporator. The next start-up process can then pull liquid refrigerant out of the evaporator and into the compressor causing liquid flooding. This phenomenon results in a loss of latent heat for cooling, can undercool the lubricant, and may cause damage to the compression mechanism. The geometric and thermophysical conditions that lead to liquid flooding are poorly understood. Experimental data collected for four refrigerants and three heat exchangers was analyzed for flooding conditions. A correlation was fitted to the experimental data, predicting the experimentally determined charge threshold for flooding with an average deviation of 6.6% and a maximum deviation of 16.7%. Repeating the tests with other heat exchanger types and smaller or larger compressors is suggested as important future work. [ABSTRACT FROM AUTHOR]

Solar evaporation is a sustainable, environmentally friendly and promising solution to the problem of fresh water shortage. However, the widespread application of solar evaporators is limited by their spatial geometry, surface salt deposition and durability. Here, a Janus evaporator with a 3D chiral torsion structure is designed using 3D printing technology. Such a structure increases the number of light reflections to improve light collection. At the same time, the top and bottom layers of the Janus evaporator are endowed with different surface wettability. In particular, the top layer of superhydrophobic SiO 2 /CNTs aerogel acts as a photothermal absorber and prevents salt deposition, while the bottom layer of superhydrophilic CNTs aerogel accelerates water replenishment and improves water transfer efficiency. At 1 sun, the 3D Janus evaporator exhibits a high evaporation rate of 2.775 kg m−2 h−1 and a solar-to-vapor conversion efficiency of 90.2%. The 3D Janus evaporator demonstrates a strong desalination capacity in simulated seawater and allows one to obtain fresh water above drinking water standards. Moreover, it can work sustainably in different environments and has good cycle stability. The 3D Janus evaporator, prepared by 3D printing, opens up new prospects and great potential to solve the issues associated with fresh water shortage. [Display omitted] • A Janus evaporator with a 3D chiral torsion structure is designed using 3D printing technology. • The top and bottom layers of the Janus evaporator are endowed with different surface wettability. • The 3D Janus evaporator shows a high evaporation rate of 2.775 kg m−2 h−1 under 1 sun. • The 3D Janus evaporator demonstrates a strong desalination capacity and allows one to obtain fresh water. [ABSTRACT FROM AUTHOR]

This study elucidates the hydrothermal characteristics of a capillary-driven stepped heat pipe (SHP). An axisymmetric numerical simulation is performed to analyze the effects of step pattern, area ratio (AR), evaporator length (LE), and wick parameters on the system characteristics. The results of the numerical model show good agreement with data from literature. These results suggest that superior performance can be achieved with a two-sided step and a step with sudden contraction with an enlarged evaporator. SHPs with a large area ratio (AR > 1) and a long evaporator yield superior thermal and capillary performances; those with a small condenser diameter (AR < 1) are more likely to experience dryout. Wick parameters, such as porosity (ε) and wick type, play a vital role in the system performance. Numerical results under the studied conditions can provide a clear engineering guide for the design of SHPs used in various engineering applications. [ABSTRACT FROM AUTHOR]

• An ethane PHP with varying evaporator lengths is designed and tested. • Prolonging evaporator can efficiently improve thermal performance. • The optimum performance can be obtained when the evaporator length is 120 mm. • Extending evaporator reduces thermal resistance as working temperatures decreases. The study aims to investigate how the evaporator length affects the thermal performance of ethane pulsating heat pipe (PHP). It is also expected to offer an approach for further practical application. The experimental apparatus is designed with varying evaporator lengths, ranging from 40 to 240 mm, and the condenser length is kept at 40 mm. The facility measures 440 mm long and has a 2 mm inner diameter. The experiment is carried out by changing the working temperatures from −100 to −20 °C and the filling ratios from 40 to 60% with different heating inputs. A thorough analysis of the temperature oscillation and heat transfer performance of the PHP with different evaporator lengths is presented. Effective thermal conductivity is introduced to further evaluate the effect of the prolonged evaporator on the performance of the PHP. The influence of the working temperature on the selection of the evaporator length is explored. The optimal filling ratios with different working conditions are provided. Experiments confirm that extending the evaporator length stabilizes the evaporator temperature and generates a decrease in thermal resistance. The most stable operation of the PHP is achieved when the evaporator is 120 mm long. The thermal performance deteriorates as the working temperature decreases. The optimal working temperature occurs at −40 °C. The increment of the filling ratio enhances the performance of the PHP and is conducive to the lower working temperature. [ABSTRACT FROM AUTHOR]

The increase in global energy consumption and carbon dioxide emissions increase the interest in renewable energy sources. Solar energy is at the forefront of renewable energy sources, and the decrease in cell efficiency due to various reasons during operation is an obstacle to this technology. Increasing the temperature of photovoltaic cells during operation causes a decrease in cell efficiency. Control of photovoltaic cells temperature is crucial in terms of both prolonging the economic life of the cells and increasing the efficiency of the system. The effect of the evaporator inlet and outlet position of the fluid on the heat transfer is known, but this effect was not examined in the studies carried out to increase the efficiency of the PV-T (photovoltaic–thermal) system. In the current study, the system efficiency parameters and COP (coefficient of performance) values of a PV-T evaporator cooled by forced air circulation were investigated by CFD (computational fluid dynamics) analysis. The analyzes were carried out in a single array for three different flow rates (0.0125 kg/s, 0.0250 kg/s, 0.0500 kg/s) and nine different evaporator inlet-outlet positions (CC, CL, CR, RC, RL, RR, LC, LL, LR), constant radiation of 1000 W/m². It was determined that there is a total efficiency difference of over 20% and an overall COP difference of over 25% between the best and worst inlet-outlet positions. The highest total and thermal efficiency were obtained for the RR condition, and the highest electrical efficiency was obtained for the LR condition but in the long-term, the highest efficiency can be achieved with the LC design. In the study also the highest COP values were calculated for the CL condition and the worst COP values for the RR condition. [ABSTRACT FROM AUTHOR]

To improve the thermo-economic performance of organic Rankine cycle (ORC) systems, a multi-level analysis method is proposed in this study. In the first level, the optimal configuration is determined based on the thermo-economic optimization. The exergy efficiency and electricity production cost are selected as the objective functions of optimization for three ORC configurations, including simple ORC, TORC (two-stage ORC), and DORC (dual-loop ORC). In the second level, the real potential of performance improvement for the optimal configuration is revealed through advanced exergy analysis method. Finally, the order of operating parameters to different performance indicators of the optimal configuration is determined by orthogonal experiment method. The results show that the TORC system exhibits better thermo-economic performance. Although the low-temperature condenser in the TORC system has the highest exergy destruction, the LTT (low-temperature turbine) contributes the largest avoidable-endogenous exergy destruction. Thus, the LTT has the greatest potential for technical improvement. The condensation temperature and pinch point temperature difference in the low-temperature evaporator are the primary factors for the thermodynamic and economic performance of the TORC system, respectively. While the evaporation temperature of the high-temperature evaporator has the greatest effect on the potential of technical improvement for the LTT. [ABSTRACT FROM AUTHOR]

Heat pipes play a critical role in determining the operations, safety, and energy efficiency of electronics. The main focus to improve the heat pipe performance is on the evaporator design or wicking structures. However, the intrinsic limitation comes from the condenser, which is fundamentally constrained by inefficient filmwise condensation (FWC). In this study, we successfully achieved a peak effective thermal conductivity (keff) of ~140 kW/(m·K) on widely used groove heat pipes by implementing sustianble dropwise condensation (DWC) and integrating with enhanced evaporator. To better understand the working mechanisms of the ultraefficient heat pipe, both the evaporator and condenser of the heat pipes have been modified accordingly. Our results show that up to 296% enhancements on the keff can be achieved under various inclination angles by only inducing DWC in the condenser section. The drawback of temperature fluctuations induced by DWC in smooth heat pipes appears to be effectively solved using the grooves‐wicking structure. Furthermore, by integrating the nanostructured evaporator, the keff of the heat pipe can be boosted up to 517% compared to conventional groove heat pipes. This study, for the first time, demonstrates the huge potential of engineering both the condenser and evaporator simultaneously in developing ultraefficient heat pipes. [ABSTRACT FROM AUTHOR]

When designing a heat pump evaporator, it is necessary to use correlations that ensure small deviations of the designed and realized process parameters for specific input data. The aim of the work is to propose a suitable mathematical model for the physical process in the tubular evaporator of the heat pump. The applicability of the proposed mathematical model in the design of the heat pump was evaluated by comparing the results obtained from the experimental tests of the tubular evaporator of the heat pump with the numerical results obtained from the application of the proposed mathematical model. For the experimental tests, a tubular evaporator was made and 10 measuring points were set up, where the process parameters were measured (temperature and pressure drop of the working media R134a and water). Theoretical results were obtained by dividing the evaporator into control volumes and solving the corresponding system of equations of the proposed mathematical model using the Runge-Kutta and Adams Moulton predictor-corrector method. As an independent parameter, the water temperature at the inlet to the evaporator was varied in the range of 10 °C to 18 °C. The test results show that the largest deviation of the calculated and measured water temperature is +0.41 °C to −0.58 °C, while the refrigerant temperature is +0.43 °C to + 0.52 °C. The largest deviation of the evaporator thermal capacity based on the calculations and experimental tests is +9.39% to −6.31%. Based on the obtained results, it is possible to recommend the use of the proposed mathematical model for the design of the tubular evaporator of a heat pump. [ABSTRACT FROM AUTHOR]

Numerical simulations on the fin shape of a microchannel evaporator in a CO2 air conditioning system were performed at the inlet evaporative temperature of 10 °C and the vapor quality of 0.61. Two types of fin shapes were dealt with: the straight fins and V-fins. The numerical results were verified by the experimental data. For the system under consideration and for the same heat transfer area and the heat transfer coefficient for the air side in the microchannel evaporator, the effect of the fin shape on the heat transfer was not different; however, the solution time and the physical memory for the straight fins were 1.3 and 1.45 times compared with the V-fins, respectively. Therefore, the V-fin shape should be used for numerical simulation to compare it with the straight fin shape. In this study, the evaporation of the refrigerant in the microchannel evaporator took place in four passes. The normal heat flux from the air through the fins and tubes was almost reached at 1550 W/m2 at the evaporative temperature of 10 °C. The results obtained from the experimental data were in good agreement with those obtained from the numerical results, with a deviation of less than 10%. [ABSTRACT FROM AUTHOR]

Under increasing heat loads and stricter energy consumption limits for data center servers, traditional heat sinks are becoming inadequate. In this paper, a novel aluminum three-dimensional vapor chamber heat sink of air cooling is developed, in which the evaporator and condenser are connected internally to form a three-dimensional flow channel for working fluid so that two heat transfer methods, phase change and single-phase, are combined in one device. Furthermore, a novel louvered-fin stacked evaporator wick structure and its fabrication process are proposed, which greatly improve thermal performance and temperature uniformity. Thermal characteristics under different heat loads, fan input power, and tilt angles are studied experimentally. Results show that the heat sink has a maximum heat dissipation capability of more than 450W, at which the maximum evaporator surface temperature is within 75 °C. The fan input power can distinctly improve thermal performance, heat load impacts overall thermal resistance slightly and the minimum is 0.083 °C/W. The tilt angle impacts thermal resistance slightly but significantly affects both the evaporator surface and condenser fin temperature uniformity. Under a tilt angle of 90°, regardless of heat loads, the condenser fin temperature is much lower than other tilt angles. • A novel aluminum 3-dimensional vapor chamber heat sink (3DVCHS) is proposed. • A louvered-fin stacked evaporator wick is implemented. • The air-cooled 3DVCHS has amaximum heat dissipation capability of more than 450W. • Heat loads impact the 3DVCHS thermal resistance slightly, the minimum is 0.083 °C/W. [ABSTRACT FROM AUTHOR]

In response to escalating demand for renewable energy, solar thermal evaporation systems with solar energy utilization and freshwater production capacities have garnered attention, yet face challenges in improving solar energy conversion efficiency and freshwater generation rate. Liquid metal particles emerge as a promising solution for photothermal systems due to their localized surface plasmon resonance (LSPR), but the poor formability limits the application in solar thermal evaporation systems. Herein, we present an innovative ice-templated material extrusion for liquid metal inks in a shape-morphing 3D photothermal solar generator. The programmable in-situ "freeze-printing" establishes water transport channels within printed liquid metal structures, enhancing functionality. This process, coupled with cool evaporation surface and optimized water supply channels, yields efficient and sustainable solar-driven evaporation. The liquid metal-based aerogel achieves an impressive surface temperature of 62 °C (36.4 °C in water) under 1 sun. The 3D programmable "freeze-printing" not only reduces ink consumption but also enables the construction of spiral-shaped structures, increase the cool evaporation surface. The resulting solar generation device attains a remarkable evaporation rate of 1.736 kg m−2 h−1. By delving into the structural design to enhance heat conduction and water evaporation, we have deepened our understanding of the printability of liquid metal in 3D, paving the way for advancements in additive manufacturing and evaporation applications. This work establishes a foundation for designing high-performance next-generation solar generation devices to combat global water scarcity. • Manipulating the rheological behavior and solution stability of LM ink. • Controlling the optical-thermal properties and structural stability of LM aerogel. • Constructing water transport channels by programmable "freeze-printing" technology. • Construction of a 3D evaporator provides cooler evaporating surface for efficient water evaporation. • Excellent water evaporation characteristics (1.736 kg m-2 h-1) and good cycling stability (8 times). [ABSTRACT FROM AUTHOR]

Although solar interfacial evaporation stands as a promising application for seawater desalination, it has been scarcely studied for volumetric reduction of particle-containing wastewater. Taking inspiration from trees, this work presents a novel approach of root-based solar-interfacial evaporation for accelerated drying of slurries. By varying the total surface area of the roots, the water conduction rate was maximized under different intensities of solar radiation. The optimal setup displayed a high evaporation rate of 1.15 kg/(m2h1) under 1 sun irradiation. Additionally, the evaporator dried the slurry to 75 wt% solid concentration at this high evaporation rate. The setup could remove water further till solid concentration above 90 wt% in a total 40-h duration. The decrease in slurry evaporation rates observed at higher solid concentration was attributed to the break-up of continuous water capillary bridges present between the particles in the slurries. Long duration evaporation experiments for over 100 h of continuous operation displayed 75 % evaporation efficiency, underlining the feasibility of this setup for long-term usage. Large-scale outdoor experiments, scaling to 625 cm2, exhibited high evaporation rates comparable to the smaller setups, confirming the feasibility of this setup for large-scale volumetric reduction. • Root-based evaporator setup developed for accelerated drying of fine-particle slurries • Slurry dried to 75 wt% solid concentration at high water evaporation rate • Larger root surface area extended evaporation performance to a higher solid concentration. • Evaporator displayed continuous removal of water beyond 90 wt% solid concentration. • Evaporator exhibited volumetric reduction for over 100 h of continuous operation. [ABSTRACT FROM AUTHOR]

• A tower-like porous wick is prepared and tested. • No temperature overshoot occurs in the open evaporator. • Performance deterioration happens in three batches of repeated sequential experiments. • Small bubbles only appear on the lower surface of porous wick. • A good installation of porous wick can ensure its working performance. Temperature overshoot often occurs in loop heat pipe, which is caused by the large bubble in the compensation chamber. But it is still uncertain whether this large bubble grew from parasitic bubbles inside porous wick. A multi-layer tower-like porous wick is designed to understand the growth and expansion of parasitic bubbles. The parasitic bubbles are induced to occur inside porous wick by inserting a copper pillar on the evaporator wall, and the multi-layer porous wick is used to eliminate parasitic bubbles. The pumping stagnation occurs under certain heat loads, but temperature overshoot of the evaporator wall no longer occurs in the open evaporator with the tower-like porous wick, which guides the design of evaporator to avoid temperature overshoot. It is found that a lot of small bubbles only appears on the lower surface of porous wick immersed in liquid in the evaporator, while not appears on the upper surface. Three groups of repeated experiments are carried out sequentially and the performance of the evaporation heat transfer gradually deteriorates, which is speculated to be caused by a gap between porous wick and the copper pillar, larger pore size next to copper pillar, or poor wetting caused by copper pillar oxidation. Two different types of the evaporator overheating are discovered, including the overall retreat of the evaporating interface and dry-out region expanded from the internal of porous wick to the external. At high heat load, the evaporating interface expands along the copper pillar, causing an increase in the heat transfer coefficient of the evaporator. The research results indicate that in order to better utilize porous wick for evaporation heat transfer, it is necessary to reliably adhere porous wick to the heating surface and avoid the formation of the large bubble in the compensation chamber. [ABSTRACT FROM AUTHOR]