Recent advances in thermally localized solar evaporation hold significant promise for vapor generation, seawater desalination, wastewater treatment, and medical sterilization. However, salt ...accumulation is one of the key bottlenecks for reliable adoption. Here, we demonstrate highly efficient (>80% solar-to-vapor conversion efficiency) and salt rejecting (20 weight % salinity) solar evaporation by engineering the fluidic flow in a wick-free confined water layer. With mechanistic modeling and experimental characterization of salt transport, we show that natural convection can be triggered in the confined water. More notably, there exists a regime enabling simultaneous thermal localization and salt rejection, i.e., natural convection significantly accelerates salt rejection while inducing negligible additional heat loss. Furthermore, we show the broad applicability by integrating this confined water layer with a recently developed contactless solar evaporator and report an improved efficiency. This work elucidates the fundamentals of salt transport and offers a low-cost strategy for high-performance solar evaporation.
Ammonia is currently investigated as a sustainable energy source. Its mixture with hydrogen may present combustion characteristics that are similar to those of hydrocarbon, which motivates its use in ...gas turbines burners. Such similarities were discussed at atmospheric pressure in previous works for a fuel blend with a molar fraction of hydrogen XH2Fuel=0.46, which is further studied here. The influences of pressure and wall heat loss on ammonia/hydrogen/air flames are for the first time investigated via large eddy simulation. A first campaign is led at both 1 and 5 atm, to estimate the effect of pressure. It demonstrates that NO emissions are favoured by flame interactions with a hot wall, along which NO is convected. Accordingly, the flame length reduction observed at high pressure, due to higher heat release rates, leads to a more efficient NO consumption. Increasing the pressure shifts the equivalence ratio for optimal NH3 and NOX emissions towards the lean side. It results in lower hydrogen emissions and therefore an increase of the combustion efficiency. Finally, the NH3 and NOX emissions at optimal equivalence ratio are reduced from 450 ppmv for φ = 1.27 at 1 atm, to ∼ 100 ppmv for φ = 1.20 at 5 atm. A second campaign is led at both 1 and 5 atm, by varying the burner wall thermal boundary conditions. Lean combustion with cold walls presents high N2O emissions of 607 ppmv while in rich cases, the higher gas temperatures and the excess of H radicals in the burned gases yield complete N2O consumption. It is shown that heat loss effect on N2O fractions distribution is reduced at high pressure due to weaker flame interaction with the cold walls. Finally, thermal boundary conditions are found to significantly affect NOX, N2O and NH3 emissions, showing that heat losses should be considered when modelling such configuration.
•Effects of pressure and heat loss on NH3/H2 combustion were explored with LES.•Passing from 1 to 5 atm lowers NOx and NH3 emissions of rich mixture by a factor 5.•Low temperature of burner wall is favourable to NO consumption.•N2O emissions are correlated to H radicals and wall temperature.•Heat losses to the wall affect significantly NOx, N2O and NH3 emissions.
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•Cold starting process of diesel engine at low temperature is analyzed in detail.•An improved thermodynamic model of diesel engine is developed.•Cold starting performance of diesel ...engine is validated by the experimental results.•Suggestions for cold starting performance enhancement of the diesel engine are proposed.
It is very important for the diesel engine to achieve a cold startup at low environmental temperature especially in the region with the temperature in the range of −40 °C to 0 °C. Thus, the specific cold start characteristics, such as gas leakage, heat loss and clearance volume, should be investigated in detail. In order to investigate the cold start ability, an improved thermodynamic model for thermodynamic parameters is developed. The prediction of ignition temperature is the closest to the experimental values when the adiabatic index is equal to 1.34 for the compressed gas. The thermodynamic results show that the compression pressure is the most sensitive to the gas leakage rate, followed by the heat transfer loss rate and reference clearance volume. The gas leakage, heat loss and clearance volume are employed to investigate the cold start ability for the diesel engine, which provide a better reference for strengthening the cold start capacity research. The small clearance volume and big initial intake air temperature can improve the exergy of diesel engine. In addition, the entropy production increases with the increase of clearance volume. Similarly, the exergy of system will reduce with the increase of entropy production. Finally, the improvement suggestions for cold starting performance enhancement of the diesel engine are proposed.
As an energy-saving equipment, task/ambient air conditioning (TAC) system was widely used in sleeping environment in recent years. The TAC can deliver cooling air directly to the sleeping person, ...resulting that the micro climate around the human body becomes very critical in the evaluation of human beings’ thermal comfort. Different from sitting and standing, sleeping human body is always at lying posture, and thus at a lower metabolic rate than at waking status. To understand the heat balance between a sleeping body and the surrounding environment, investigation on the heat loss of human body becomes necessary. Hence, a numerical study on the body heat loss characteristics of a thermal manikin at sleeping state in a bedroom utilizing a TAC system was carried out. The convective heat transfer, radiative heat transfer, evaporative heat loss from skin and respiratory heat loss and their ratios were quantitatively analyzed. The results indicate that the convective heat transfer took the first place, accounting for about 80% of the total heat loss, and Latent heat loss accounted for 15.9%–21% of the total heat loss. In addition, the heat loss at different supply conditions was numerically studied. Results showed that the supply air temperature, flowrate and humidity play different effects on body heat loss. Contributions of this study are meaningful for the accurate control of micro climate of human activities.
Magnetic hyperthermia (MHT) is a therapeutic modality for the treatment of solid tumors that has now accumulated more than 30 years of experience. In the ongoing MHT clinical trials for the treatment ...of brain and prostate tumors, iron oxide nanoparticles are employed as intra-tumoral MHT agents under a patient-safe 100 kHz alternating magnetic field (AMF) applicator. Although iron oxide nanoparticles are currently approved by FDA for imaging purposes and for the treatment of anemia, magnetic nanoparticles (MNPs) designed for the efficient treatment of MHT must respond to specific physical-chemical properties in terms of magneto-energy conversion, heat dose production, surface chemistry and aggregation state. Accordingly, in the past few decades, these requirements have boosted the development of a new generation of MNPs specifically aimed for MHT. In this review, we present an overview on MNPs and their assemblies produced
different synthetic routes, focusing on which MNP features have allowed unprecedented heating efficiency levels to be achieved in MHT and highlighting nanoplatforms that prevent magnetic heat loss in the intracellular environment. Moreover, we review the advances on MNP-based nanoplatforms that embrace the concept of multimodal therapy, which aims to combine MHT with chemotherapy, radiotherapy, immunotherapy, photodynamic or phototherapy. Next, for a better control of the therapeutic temperature at the tumor, we focus on the studies that have optimized MNPs to maintain gold-standard MHT performance and are also tackling MNP imaging with the aim to quantitatively assess the amount of nanoparticles accumulated at the tumor site and regulate the MHT field conditions. To conclude, future perspectives with guidance on how to advance MHT therapy will be provided.
Silkworm silk, a potential material used as the matrix of conductive fibers, has attracted extensive attention due to its excellent mechanical properties. However, researches on its thermal ...properties, especially in the axial direction of the single silk fibroin fiber are less. In this study, the axial thermal conductivity of a single silk fibroin fiber after coating a gold film on the surface is measured using the 3ω method. The effects of the radiation heat loss on the intrinsic thermal conductivity are eliminated by varying the length of the test samples. The results show that the thermal conductivity of the single silk fibroin fiber decreases slightly as the temperature increases from 260 to 300 K. The extracted intrinsic axial thermal conductivity is about 0.775 W/m-K at room temperature, an order of magnitude higher than most textile fibers. The method proposed in this study can be extended to accurately measure the thermal conductivity of the other non-conductive micro-fibers.
•A 3ω-based technique is developed to eliminate the radiation loss and obtain the intrinsic axial thermal conductivity.•Contribution from radiation is important and should be considered for samples with large lengths and small diameters.•The kintr of the single silk fibroin fiber is found to be an order of magnitude higher than most textile fibers.
In this work, detailed investigations of convection heat loss from conical cavity receiver of solar parabolic dish collector using a numerical method and artificial neural network have been ...performed. The convective heat loss from the cavity receiver is primarily influenced by geometrical parameters, receiver orientation, and wind characteristics. The heat loss estimation is carried out by considering wind speed (V = 0-10 m/s), wind direction (
= 90
and −90
), receiver tilt (
= 0-90
), diameter to height ratio (d/h = 0.5-1.5), and surface temperature (T
s
= 500-800 K). The utmost heat loss occurs at a tilt of 60
for d/h < 1 and 75
for d/h
1 in head-on high wind speed, while in back-on high wind speed, it occurs at a tilt of 30
for all d/h values. The heat loss is lowest at 90° for V > 4 m/s. The d/h value of 0.5 performs well compared to other values. Further, the correlation for the Nusselt number has been proposed for the conical cavity receiver.
Abstract
Solar steam generation is emerging as promising solar-energy conversion technology for potential applications in desalination, sterilization and chemical purification. Despite the recent use ...of photon management and thermal insulation, achieving optimum solar steam efficiency requires simultaneous minimization of radiation, convection and conduction losses without compromising light absorption. Inspired by the natural transpiration process in plants, here we report a 3D artificial transpiration device with all three components of heat loss and angular dependence of light absorption minimized, which enables over 85% solar steam efficiency under one sun without external optical or thermal management. It is also demonstrated that this artificial transpiration device can provide a complementary path for waste-water treatment with a minimal carbon footprint, recycling valuable heavy metals and producing purified water directly from waste water contaminated with heavy metal ions.
To ensure good thermal performance is delivered consistently and at scale, there is a need to measure and understand the as-built heat loss of dwellings. Co-heating is a steady state, linear ...regression method, used to measure whole building heat transfer coefficients. This paper assesses the uncertainties in such outdoor, in situ, measurements due to the presence and treatment of solar gains. Uncertainties relating to solar gains are explored through both a number of field test results and simulated co-heating tests. Results demonstrate the potential for fractions of solar gains received on one day to be re-emitted on subsequent days. This dynamic behaviour can lead the steady state analysis to underestimate heat loss. Furthermore, inappropriate measurements of on-site solar radiation are shown to lead to bias in heat loss measurements. In particular, horizontal on-site solar radiation measurements are shown to significantly overestimate heat loss in buildings experiencing high proportions of direct gains through vertical openings. Both forms of uncertainty are dependent upon both the environmental test conditions and the characteristics of a test dwelling. Highly glazed, low heat loss and heavyweight buildings prove to be the most susceptible to such uncertainties, which ultimately limit both when tests can be successfully performed and which buildings can be tested.
A new dataset of nearly 15,000 oceanic heat flow measurements is analyzed to determine the conductive heat loss through the seafloor. Many heat flow values in seafloor younger than 60
Ma are lower ...than predicted by models of conductively cooled lithosphere. This heat flow deficit is caused by ventilated hydrothermal circulation recharge and discharge at crustal outcrops or areas of thin sedimentary cover. Filtering heat flow data, retaining only sites with >
400
m of sediment cover and located >
60
km from the nearest seamount, minimizes the effect of hydrothermal ventilation. Filtered heat flow exhibits a much higher correlation coefficient with seafloor age (up to 0.95 for filtered data in contrast to 0.5 for unfiltered data) and lower variability (reduction by 30%) within an age bin. A small heat flow deficit still persists at ages <
25
Ma, possibly as a result of global filtering limitations and incomplete thermal rebound following sediment burial. Detailed heat flow surveys co-located with seismic data can identify environments favoring conductive heat flow; heat flow collected in these environments is higher than that determined by the filtered global dataset, and is more consistent with conductive cooling of the lithosphere. The new filtered data analysis and the growing number of site specific surveys both support estimates of global heat loss in the range 40–47 TW.
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► We analyze ~
15,000 ocean heat flow observations globally. ► Sediment and seamount filters improve conductive heat loss estimates. ► Site-specific analyses provide robust estimates of conductive heat loss. ► Filtered heat flow vs. age is consistent with conductive plate cooling models. ► Estimated heat flow vs. age is consistent with oceanic heat loss, 40–47 TW.
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