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Dual compensation chamber loop heat pipe (DCCLHP) holds great application potential in the future aircraft thermal management. In this work, a DCCLHP with dual bayonet tubes was first proposed and fabricated, aiming to improve its startup performance especially at small heat loads in the terrestrial surroundings. Extensive experimental validation was conducted at three typical attitudes of the evaporator/CCs, i.e., the vertical attitude, 45° tilt angle and the horizontal attitude, mainly focusing on its startup characteristics and heat transport capability. According to the experimental results, the DCCLHP with dual bayonet tubes can successfully realize the startup at small heat loads in whatever attitudes of the evaporator/CCs in the ground condition, and reach a heat transport limit greater than 400 W over a distance of 2.0 m. No obvious operating instability was observed in the DCCLHP operation. In addition, a new flow mechanism was observed in the experiment, i.e., a local natural circulation of the working fluid driven by gravity occurred in the loop composed of the evaporator, the CCs, the bayonet tubes, and the branches of the liquid line. This local circulation of working fluid was identified to appear only when the evaporator/CCs were at a certain tilt angle and the heat loads were relatively small.

The coupling effect of evaporator/condenser elevations and non-condensable gas (NCG) on the performance of a loop heat pipe (LHP) operating in gravitational field was investigated experimentally. Ammonia and nitrogen were selected as the working fluid of LHP and the simulated gas of NCG, respectively. The experiments were conducted at three kinds of evaporator/condenser elevations, namely zero elevation, adverse elevation and positive elevation. Experimental results show that NCG will cause an increase in operating temperature, but the trends varies at different evaporator/condenser elevation elevations. The temperature rises caused by NCG at the zero and adverse elevations are negatively correlated with heat load, and the maximum temperature increments are both at the minimum heat load of 15 W, but the influence of NCG is less at adverse elevation. On the other hand, at favorable elevation, the temperature rise exhibits different characteristics in different LHP operation modes, i.e., positively correlated with heat load in gravity driven mode and negatively in capillarity-gravity co-driven mode, and the transition heat load is 60 W. For an LHP that has already contained a certain amount of NCG, functioning at favorable elevation could eliminate the adverse effects of NCG on operating temperature and heat transfer performance to some extent. Furthermore, it is found that the presence of NCG and adverse elevation appears to inhibit the backflow during startup and improve startup stability. These results might have reference significance for the design and installation of the LHP for terrestrial applications.

Although natural convection and thermal creep have been well recognized in the continuum and rarefied regimes, respectively, the study of the competition of them in a wide flow regime is very scarce. From a theoretical point of view, natural convection can be described by Navier–Stokes–Fourier (NSF) equations at the macroscopic level, while thermal creep needs descriptions at the molecular level. Therefore, it is quite challenging to capture these two effects simultaneously. In this work, we employ the unified stochastic particle Bhatnagar–Gross–Krook (USP-BGK) method to investigate thermally driven gas flow in a square enclosure. The simulation results obtained by the USP-BGK method are validated by comparing to those from NSF solutions and direct simulation Monte Carlo method for the continuum and transitional regimes, respectively. We find that the flow patterns in the whole flow regime cannot be determined by just one nondimensional parameter, i.e., the Rayleigh number (Ra), but needs two nondimensional parameters, i.e., the Knudsen number (Kn) and the Froude number (Fr), or Kn and Ra. Specifically, small Knudsen and Froude numbers tend to generate natural convection, while large Knudsen and Froude numbers tend to cause thermal creep. Moreover, our simulation results and analyses demonstrate that when Kn < 0.12, thermal creep is dominant if Ra < 1.0, while natural convection is dominant if Ra/Fr > 0.28, or equivalently, L/L* > 1.0, where L is the characteristic length of the system and L* is the equivalent characteristic length of molecules. These findings provide useful guidance for better understanding of the complex gas flows resulting from the competition of natural convection and thermal creep under microscale or low-density conditions such as on Mars.

In this study, a solar parabolic trough concentrator (PTC) was evaluated as a heat source of a power generation system based on energy (E1), exergy (E2), environmental (E3), and economic (E4) analyses. Various configurations of power generation systems were investigated, including the solar SRC (SRC) and solar ORC (ORC). Water and R113 were used as heat transfer fluids of SRC and ORC system, respectively. It should be mentioned that the proposed solar systems were evaluated for providing the required power of a mobile house in an emergency condition such as an earthquake that was happened in Kermanshah, Iran, in 2016 with many homeless people. The PTC system was optically and thermally investigated based on sensitivity analysis. The optimized PTC system was assumed as a heat source of the RC with two various configurations for power generation. Then, the solar RC systems were investigated based on 4E analyses for providing the power of the mobile house based on various numbers of solar RC units. It was concluded that the solar SRC system could be recommended for achieving the highest 4E performance. The highest value of its energy efficiency was found at 24.60% and of his exergy at 26.37%. On the other hand, the ORC system has energy and exergy efficiencies at 17.64% and 18.91%, respectively, which are significantly lower than the efficiencies of the SRC system. The optimum heat source temperature for the SRC system is found at 650 K, while for the ORC system at 499 K. Moreover, the best economic performance was found with the SRC system with a payback period of 7.47 years. Finally, the CO2 mitigated per annum (φCO2) was estimated at 5.29 (tones year−1), and the carbon credit (ZCO2) was calculated equal to 76.71 ($ year−1).

Systematic experiments were firstly designed and conducted to investigate the operating characteristics of a dual compensation chamber loop heat pipe (DCCLHP) under periodic acceleration conditions. A new acceleration test rig was built to generate acceleration magnitude up to 11 g. The heat load ranged from 150 W to 300 W. Three different periodic acceleration patterns, two loading modes and two acceleration directions were used to study their influence on the operating characteristics of the DCCLHP. The results demonstrated that the loop temperature could periodically oscillate with the periodic change of the acceleration. A large acceleration could lead to a high operating temperature. Configuration B could cause the lower operating temperature than configuration A for a fixed case. There were stable operating temperature difference and thermal resistance variation before and after the periodic acceleration acting for the loading mode 1. Temperature overshooting after unloading the periodic acceleration was also confirmed for the loading mode 2. Such phenomena could be explained by the change of the vapour-liquid distribution in the loop and the heat leak from the evaporator to the compensation chambers (CCs). The loop temperature oscillation with different frequency and amplitude might also occur during each periodic acceleration. For the cases of 150 W and configuration A, the acceleration effect could trigger the operating temperature exceeding 60 °C. Our work proves significant phenomena existing in the DCCLHP and presents detailed analysis, which would be of great importance for the development of new generation of loop heat pipe used in aircraft thermal management system.

The dynamics of droplets impacting on solid surfaces are directly related to a variety of engineering applications. As some industrial processes have been refined to the nanoscale, research interest in nanodroplets impact is growing. In this work, molecular dynamics (MD) is employed to investigate the impact processes of nanodroplets on superhydrophobic surfaces decorated with triangular nanoridges. We confirm that the decorated nanoridges can significantly promote the bouncing performance of nanodroplets, including enlarging the bounce domain, reducing the contact time, and enhancing the bounce velocity. We identify five distinct bounce modes for nanodroplets on the nanoridged surfaces, and the variation laws of contact time and bounce velocity of nanodroplets are determined by the characteristics of these bounce modes. Configuration of nanoridges can influence the variation laws of contact time and bounce velocity through changing the bounce modes of nanodroplets. The restitution coefficient can be piecewise fitted as the power functions of the impact Weber number of nanodroplets, regardless of the droplet diameters and ridge configurations. This work elucidates the characteristics and mechanism of nanodroplets impacting on the nanoridged surfaces, which is conducive to the design of nanostructured surfaces for related applications.

Although a superhydrophobic surface could realize rapid rebounding (i.e., short contact time) of an orthogonal impacting droplet, the rebounding along the original impacting route may limit its engineering application; in contrast, the directional transportation seems to be more promising. Here, we achieve directional transportation of a droplet impacting a wettability-controlled surface. When the droplet eccentrically impacts on the boundary between the superhydrophobic part and the hydrophilic part, it undergoes spreading, retracting, departure, throwing, and breaking up stages, and finally bounces off directionally. The directional transportation distance could even reach more than ten times the droplet size, considered the adhesion length (i.e., covering length on the hydrophilic part by the droplet at the maximum spreading) is optimized. However, there is a critical adhesion length, above which the directional transportation does not occur. To be more generalized, the adhesion length is de-dimensionalized by the maximum spreading radius, and the results show that as the dimensionless adhesion length increases, the transportation distance first increases and then decreases to zero. Under the present impacting conditions, the optimal dimensionless adhesion length corresponding to the maximum transportation distance is near 0.4, and the critical dimensionless adhesion length is about 0.7. These results provide a fundamental understanding of droplet directional transportation and could be useful for related engineering applications.

Droplet jumping phenomenon widely exists in the fields of self-cleaning, antifrosting, and heat transfer enhancement. Numerous studies have been reported on the static droplet jumping while the rolling droplet jumping still remains unnoticed even though it is very common in practice. Here, we used the volume of fluid (VOF) method to simulate the droplet jumping induced by coalescence of a rolling droplet and a stationary one with corresponding experiments conducted to validate the correctness of the simulation model. The departure velocity of the jumping droplet was the main concerned here. The results show that when the center velocity of the rolling droplet (V0 = ωR, where ω is the angular velocity of the rolling droplet and R is the droplet radius) is fixed, the vertical departure velocity satisfies a power law which can be expressed as Vz,depar = aRb. When the droplet radius is fixed, the vertical departure velocity first decreases and then increases if the center velocity exceeds a critical value. Interestingly, the critical center velocity is demonstrated to be approximately 0.76 times the capillary-inertial velocity, corresponding to a constant Weber number of 0.58. Different from the vertical departure velocity, the horizontal departure velocity is basically proportional to the center velocity of the rolling droplet. These results deepen the understanding of the droplet jumping physics, which shall further promote related applications in engineering fields.

Elastic turbulence has shown great potential to enhance heat transfer performance at the microscale. Most of the studies, however, have only considered global convective heat transfer performance along curvilinear channels, despite that the intensity of the chaotic flow varies along the streamline, leading to different local heat transfer characteristics. This work systematically investigated the local convective heat transfer performance by elastic turbulence of a shear-thinning fluid in a serpentine channel. The flow visualization along the serpentine channel was obtained and analyzed to show the existence of elastic instability and elastic turbulence. Significant enhancement of mixing was observed with the increase of polymer concentration and bulk flowrate. The variations of pressure drop, heat transfer coefficients and Nusselt numbers along the serpentine channel were analyzed to reveal local characteristics of elastic turbulence. A three-stage pressure drop profile was identified due to the variations of viscosity and elastic turbulence intensity at different flowrates and Reynolds numbers. A non-linear heat transfer performance, which increased with the increase of polymer concentrations, was observed. These are mainly attributed to the increasing intensity of elastic instability, resulting from the balance between normal stresses and streamline curvatures. A large increase of Nusselt number versus Weissenberg number was also revealed due to the coupling of shear-thinning behavior and elastic instability effects.

Many unmanned aerial vehicles (UAVs) such as solar powered ones require their top surfaces of the wings to be integral and gap free. To enable rolling movement and improve aerodynamic performance of such UAVs, a novel design scheme of split aileron is proposed that is similar to the concept of split flap. The function of the separated aileron is implemented utilizing an electro-servo system actuated by a brushless direct current motor (BLDCM). The design of three conceptual configurations, including the upper, middle, and bottom positions with deflection angle of 31° and 15° downwards, are studied numerically. Based on the optimal design of the bottom position of the split aileron structure, its aerodynamic characteristics, maneuverability and structural weight are evaluated by comparing with a traditional hinged aileron. The results indicate that the proposed design of the detached aileron can enhance the average aerodynamic efficiency of the wing by 16.3% and reduce the weight by 58.3%. A functional prototype of the split aileron wing airplane is established and manufactured based on the proposed design. The flight test results confirm the applicability of the clam-shell aileron to control the rolling motion of aircraft, which is of high potential for solar-powered fixed-wing UAVs.

Considering the mass and energy sources carried by the accumulated ice layer, an unsteady heat and mass transfer model of the runback water film on the deicing surface is established to simulate aircraft electro-thermal deicing process. With the extension of the freezing coefficient to the transient calculation, the coupled heat transfer of the runback water and the solid skin is solved at each time step by a temperature-based method. Unsteady numerical simulation is carried out for the electro-thermal deicing system of a NACA 0012 airfoil. The temperature variations with time are in acceptable agreement with the literature data, and the unsteady temperature-based deicing model is verified. The calculation results of temperature, runback water flux and ice thickness on the deicing surface are analyzed at different time points, and it is shown that the unsteady electro-thermal deicing model can capture the main features of the icing, ice melting and re-freezing processes in the transient deicing simulations.

Considering the influence of surface temperature distribution on air convective heat transfer coefficient, the robust tight-coupling method is firstly developed for aircraft thermal anti-icing simulations under icing conditions. To include the effects of the impinging water droplets on the conjugate heat transfer of thermal anti-icing systems, the Messinger thermodynamic model of runback water film is modified and added to the tightly coupled calculation of the external air flow and the internal solid skin heat conduction. Numerical simulations are carried out on an electro-thermal anti-icing system under both dry air and icing conditions, and the main conclusions below can be drawn. First, convective heat transfer coefficient changes slightly with surface temperature near the leading edge, but is obviously affected by temperature distribution in the downstream area. Second, the anti-icing temperature deviations between the predicted value and the experiment date are acceptable and comparable to the calculation results in the literature, verifying the feasibility and effectiveness of the tight-coupling method. Third, compared with the traditional decoupled loose-coupling method, the robust tight-coupling anti-icing method successfully captures the effect of surface temperature on convective heat transfer coefficient, and predicts higher temperature with lower drop rate on the downstream surfaces.

HITEC salt (40 wt. % NaNO2, 7 wt. % NaNO3, 53 wt. % KNO3) with a melting temperature of about 142 °C is a typical phase change material (PCM) for solar energy storage. Both aluminum oxide (Al2O3) nanopowder and metal foam were used to enhance pure HITEC salt, so as to retrieve the limitation of composite PCMs with single enhancement. The morphologies and thermo-physical properties of the composites were firstly characterized with Scanning Electron Microscope, Fourier-transform Infrared spectroscopy and Differential Scanning Calorimeter, respectively. A pilot test rig with a heater of 380 W located in the inner pipe was built, which was encapsulated with HITEC salt, nano-salt (HITEC salt seeded with 2 wt. % Al2O3 nanopowder) and salt/copper foam composite seeded with 2 wt. % Al2O3 nanopowder as storage media. Then heat storage and retrieval tests of the energy storage system were conducted both for pure HITEC salt and composite PCMs at various heating temperatures. The temperature evolutions and distributions of the PCMs at different locations were measured, including radial, angular, and axial locations, and the energy and volumetric mean powers during heat storage/retrieval processes were calculated subsequently. The results show that metal foam is generally compatible with the nano-salt. The maximum deviation of the melting/freezing phase change temperatures of the nano-salt/copper foam composite is 3.54 °C, whereas that of the nano-salt/nickel foam composite is 3.80 °C. The specific heats of the nano-salt are apparently enhanced with the addition of Al2O3 nanopowder both in solid and liquid states. The system encapsulated with the nano-salt/copper foam composite can be considerably enhanced, e.g. the time-duration of heat storage process at the heating temperature of 160 °C can be reduced by about 58.5%, compared to that of pure salt. The volumetric mean power of heat storage for the nano-salt/copper foam composite at the heating temperature of 180 °C increases to 109.32 kW/m3, compared with 53.01 kW/m3 of pure HITEC salt. The information will be helpful for solar system design, construction and application using molten salt for solar energy storage.

To explore the effect of initial velocity on the droplet jumping induced by coalescence of a moving droplet and a static one, we performed simulations using the volume of fluid method with a dynamic contact angle model, and validated the simulation results against our experiments. The results show that the initial velocity of the moving droplet accelerates the droplet deformation during jumping, resulting in a unique departure feature. Droplet departs at different stages under different initial velocities, and the droplet departure velocity in the vertical direction is approximately constant at the first stage and then increases after Reynolds number reaches a critical value. The horizontal departure velocity is proportional to the initial velocity with a ratio of 0.4. The initial velocity also affects the energy conversion during the droplet jumping greatly. This work shall bring new insights into the droplet jumping behavior and promote its application in related fields.

In order to promote future commercial applications of loop heat pipe (LHP) especially in the civil fields, environmentally friendly R134a is considered a good candidate working fluid to replace the commonly used anhydrous ammonia. In this work, two sets of LHPs with R134a as the working fluid were designed and fabricated, one with a nickel wick, and the other with a stainless steel wick. Their thermal performance, mainly including the startup, the power increment test, the thermal resistance and the heat transport capability, were experimentally studied, evaluated and compared. Based on the experimental results, it is found that both of the R134a LHPs present excellent startup performance, achieve a maximum heat transfer capacity greater than 100 W, and exhibit good response characteristics to stepwise change of heat load. The R134a LHP with a nickel wick shows good anti-gravity capability; however, the one with a stainless steel wick is quite sensitive to the adverse elevation. The physical mechanisms responsible for the experimental results mentioned above have been analyzed and discussed. This work contributes to a better understanding on the operating performance and characteristics of the R134a LHPs, providing good design guidance and reference for its future applications.

We verify the similarity law (SL) and show a violation of frequency scaling (f-scaling) in low-pressure capacitive radio frequency (rf) plasmas via fully kinetic particle-in-cell simulations. The SL scaling relations for electron density and electron power absorption are first confirmed in similar rf discharges. Based on these results, with only the driving frequency varied, the f-scaling for electron density is also validated, showing almost the same trend as the SL scaling, across most of the frequency regime. However, violations of the f-scaling are observed at lower frequencies, which are found to be relevant to the electron heating mode transition from stochastic to Ohmic heating. Electron kinetic invariance is illustrated for the SL and f-scaling being valid, respectively, whereas the electron kinetic variation is observed when the f-scaling is violated.

Developing renewable energy technologies, especially solar energy-based, is of great importance to secure our energy future. Current solar thermal systems, however, have relatively low utilization efficiencies, limited not only by their low solar energy capture efficiency but also the auxiliary pumping power to circulate the working fluid. Here an innovative nanoparticle enabled pump-free direct absorption solar collector concept is presented, which combines the advantages of volumetric solar harvesting and oscillating heat pipes. Two different flow modes have been observed when the concentration of nanofluid is different. There is an optimum filling ratio when the thermal resistance reaches the minimum. Validation experiments show that the proposed concept can efficiently harvest solar energy and spontaneously transfer the heat into targeted areas, providing a novel approach for efficient solar energy utilization.

Objective: To assess the association between metformin and endometrial cancer risk by conducting a meta-analysis.Methods: A comprehensive search of electronic databases, conference abstracts, and clinical trial registers was performed to identify available evidence. Studies that evaluated the association between metformin use and endometrial cancer risk were considered. We pooled relative risk (RR) estimates with 95% confidence intervals (CIs) by using either a fixed-effects or a random-effects model.Results: Nine studies (1 randomized controlled trial, 5 cohort studies, and 3 case-control studies) involving more than 1.20 million participants and 7,762 cases of endometrial cancer met eligibility criteria. There was no evidence of an association between metformin use and endometrial cancer risk (RR, 0.96; 95% CI, 0.80 to 1.16). Similarly, the pooled data showed that metformin use was not significantly associated with endometrial cancer risk in patients with diabetes (RR, 0.93; 95% CI, 0.78 to 1.11). In subgroup analyses, the results were stable across different study designs and comparisons, and remained unchanged after adjusting for age and BMI or obesity.Conclusions: The current meta-analysis suggests that metformin has no chemopreventive effect against endometrial cancer.

Elastic turbulence, which is sensitive to geometry and polymer rheology, has shown great potential for improving the performance of mixing, heat transfer, and even oil recovery. Recent studies showed the importance of the rheological properties of polymer solutions on the onset of elastic turbulence. However, variations of rheological properties based on polymer sensitivities such as salinity and its corresponding effects on the elastic turbulence have not been revealed. This work investigated systematically the effects of salinity on the onset of elastic turbulence in both swirling flow and curvilinear microchannels. The variations of statistical properties, such as probability distribution functions (PDFs) and power spectral density of injected power (PSD), were analyzed for characterization. The onset conditions of elastic turbulence are postponed by high salinity, which is consistent with the mixing performance in a curvilinear microchannel. A salinity independent power-law exponent at a value of −4.3 is observed in a fully developed elastic regime for all polymer solutions. Particularly, the diffusion of fluorescein at a low flow rate in the microchannel is possible due to the existence of a steady secondary flow before the onset of elastic instability.

Water/oil flow characteristics in a water-wet capillary were simulated at the pore scale to increase our understanding on immiscible flow and enhanced oil recovery. Volume of fluid method was used to capture the interface between oil and water and a pore-throat connecting structure was established to investigate the effects of viscosity, interfacial tension (IFT) and capillary number (Ca). The results show that during a water displacement process, an initial continuous oil phase can be snapped off in the water-wet pore due to the capillary effect. By altering the viscosity of the displacing fluid and the IFT between the wetting and non-wetting phases, the snapped-off phenomenon can be eliminated or reduced during the displacement. A stable displacement can be obtained under high Ca number conditions. Different displacement effects can be obtained at the same Ca number due to its significant influence on the flow state, i.e., snapped-off flow, transient flow and stable flow, and ultralow IFT alone would not ensure a very high recovery rate due to the fingering flow occurrence. A flow chart relating flow states and the corresponding oil recovery factor is established.

In order to push forward the commercial applications of loop heat pipe (LHP) especially in an environment where people are present, it is of great importance to explore alternative working fluids to substitute the commonly used anhydrous ammonia. In this work, an acetone-charged LHP with a nickel wick is developed and experimentally studied, mainly focusing on its startup and heat transport capability. Based on the experimental results and theoretical analysis, some important conclusions have been drawn, as summarized below: 1) The acetone-charged LHP with 2 mm inner diameter pipeline can successfully realize the startup, and reach a heat transport capability of 60 W × 0.5 m; 2) When the inner diameter of the pipeline is increased from 2 to 4 mm, the LHP can start up with a much smaller heat load, i.e., 5 W, achieving a much lower steady-state operating temperature; 3) When the inner diameter of the pipeline is increased from 2 to 4 mm, the heat transport capability of the acetone-charged LHP can be increased from 60 to 100 W. 4) Adverse elevation affects greatly the heat transport capability of the acetone-charged LHP. With the adverse elevation increasing from 0 to 0.2 m, the heat transport capability is decreased from 100 to 60 W. The physical mechanisms responsible for the experimental results mentioned above have been analyzed and discussed. This work contributes to a better understanding on the operating performance and characteristics of the acetone-charged LHP, providing good design guidance and reference for its future applications.

Songhe Li,1 Dacheng Wen,2 Songtian Che,3 Zhihua Cui,1 Yabin Sun,1 Hua Ren,1 Jilong Hao1 1Department of Ophthalmology, The First Hospital of Jilin University, Changchun, People’s Republic of China; 2Department of Gastrointestinal Nutrition and Hernia Surgery, The Second Hospital of Jilin University, Changchun, People’s Republic of China; 3Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, People’s Republic of China Background: A growing body of evidence supports the involvement of long noncoding RNA 00152 (LINC00152) in the progression and metastasis of multiple cancers. However, the exact roles of LINC00152 in the progression of human retinoblastoma (RB) remain unknown. We explored the expression and biological function of human RB.Materials and methods: The expression level of LINC00152 in RB tissues and cells was analyzed using quantitative real-time PCR. The function of LINC00152 was determined using a series of in vitro assays. In vivo, a nude mouse model was established to analyze the function of LINC00152. Gene and protein expressions were detected using quantitative real-time PCR and Western blot assays, respectively.Results: The expression of LINC00152 mRNA was upregulated in RB tissues and cell lines. Knockdown of LINC00152 significantly inhibited cell proliferation, colony formation, migration, and invasion and promoted cell apoptosis and caspase-3 and caspase-8 activities in vitro, as well as suppressing tumorigenesis in vivo. We identified several genes related to proliferation, apoptosis, and invasion including Ki-67, Bcl-2, and MMP-9 that were transcriptionally inactivated by LINC00152.Conclusion: Taken together, these data implicate LINC00152 as a therapeutic target in RB. Keywords: retinoblastoma, LINC00152, proliferation, invasion