Porous structures are ubiquitous in many thermal management and energy conversion systems. The morphology of a porous structure has significant impact on the fluid flow, heat/mass transport, and ...strength performance. However, the available fabrication techniques are not capable of directly tailoring porous structures with well-controlled pore features and functional graded pore morphology, thereby limiting the performance enhancements for these systems. In this study, a triply periodic minimal surface (TPMS) based method was developed to customize the morphology of porous media with well-controlled pore features and to fabricate these parts with additive manufacturing. Porous structures with designed pore parameters were built based on the mathematically defined iWP surface, primitive surface, diamond surface and gyroid surface. Before performing flow and heat transfer simulations, morphological analysis was conducted to establish the connections between the geometrical parameters and the performance of the porous structure (flow resistance, heat transfer, and strength). The porous structures were compared in terms of their structural strength, specific pressure drop, interstitial/volumetric heat transfer coefficients and the ratio of the Colburn factor relative to the friction factor. The TPMS porous structures indicated that much higher strength than the simple cubic packing structure (approximation of sintered metal particles) due to their reasonable struct connectivity. Computations demonstrated that the type P structure had the lowest flow resistance and highest comprehensive heat transfer coefficient (j/f). The high specific surface area, continuous changes in the flow direction, periodic mixing/redistribution and flow acceleration contributed to the higher volumetric heat transfer coefficients in the type W/G structures.
•Effects of pressure on supercritical pyrolysis of n-decane are investigated.•The formation of liquid products is preferred at higher pressures.•A novel global reaction modelling approach is proposed ...for hydrocarbon fuels.•Stoichiometric coefficients are expressed as functions of fuel conversion and pressure.•The new model predicts pyrolysis accurately at both low and high pressures.
Pressure is one of the key factors in pyrolysis of hydrocarbon fuels at supercritical pressures, which changes the relation between the product distribution and fuel conversion. However, reaction model with both high accuracy and efficiency to predict pressure effects is lacking. A comprehensive experimental investigation of pressure effects on supercritical pyrolysis of n-decane in the pressure range of 3–7 MPa and temperature range of 560–670 °C is presented. The formation of liquid products is preferred at higher pressures. Gas and liquid products of n-decane pyrolysis can be categorized into three and four types, respectively, according to the formation characteristics. Results show that pressure had more profound effects on the formation of most products without C–C double bonds or benzene rings in their molecular structures (i.e., C3–C9 n-paraffins or cycloparaffins). A novel global reaction modeling approach was presented to solve the effects of both pressure and secondary reactions on pyrolysis of hydrocarbon fuels, in which the stoichiometric coefficients of each product are expressed as binary functions of fuel conversion and pressure. The proposed model was implemented in a computational fluid dynamics (CFD) simulation to predict the n-decane pyrolysis coupled with flow and heat transfer. The results show that the model predicts n-decane pyrolysis more accurately at both low and high pressures. This study can help design regenerative cooling systems with high accuracy and efficiency for engineering applications.
Mimicking the active site and the substrate binding cavity of the enzyme to achieve specificity in catalytic reactions is an essential challenge. Herein, porous coordination cages (PCCs) with ...intrinsic cavities and tunable metal centers have proved the regulation of reactive oxygen species (ROS) generating pathways as evidenced by multiple photo‐induced oxidations. Remarkably, in the presence of the Zn4‐μ4‐O center, PCC converted dioxygen molecules from triplet to singlet excitons, whereas the Ni4‐μ4‐O center promoted the efficient dissociation of electrons and holes to conduct electron transfer towards substrates. Accordingly, the distinct ROS generation behavior of PCC‐6‐Zn and PCC‐6‐Ni enables the conversion of O2 to 1O2 and O2⋅−, respectively. In contrast, the Co4‐μ4‐O center combined the 1O2 and O2⋅− together to generate carbonyl radicals, which in turn reacted with the oxygen molecules. Harnessing the three oxygen activation pathways, PCC‐6‐M (M=Zn/Ni/Co) display specific catalytic activities in thioanisole oxidation (PCC‐6‐Zn), benzylamine coupling (PCC‐6‐Ni), and aldehyde autoxidation (PCC‐6‐Co). This work not only provides fundamental insights into the regulation of ROS generation by a supramolecular catalyst but also demonstrates a rare example of achieving reaction specificity through mimicking natural enzymes by PCCs.
Porous coordination cages with Zn‐, Ni‐ and Co‐metal clusters exhibited different electronic structures which dictated the reactive oxygen species evolution. Three photoreactions were achieved by the three cages, respectively, because of the distinct charge transfer and energy transfer pathways. This work demonstrated a rare case that a supramolecular photocatalyst exhibited reaction specificity.
•The ejector-expansion heat pump system was investigated for water outlet temperatures up to 90 °C.•The COP reaches 3.3 when water outlet temperature is 90 °C.•The ejector-expansion system COP is ...10.3% higher than the corresponding basic cycle.•Adding an ejector is more effective for the generation of high-temperature hot water.•The COP and ΔCOP increase when the compressor rotation speed decreases.
The effects of hot-water outlet temperature, compressor discharge pressure, compressor rotation speed, and expansion valve opening on the ejector and overall system performance were investigated for tap water outlet temperatures ranging from 50 to 90 °C. The coefficient of performance (COP) of the ejector–expansion heat pump system reaches 4.6 when the tap water outlet temperature is 70 °C, which is 10.3% higher than the corresponding basic cycle. Compared to the basic system, adding an ejector is more effective for the generation of high-temperature hot water. The COP of the ejector–expansion heat pump system increases; however, the COP improvement ratio ΔCOP decreases with the increase in the discharge pressure because of lower pressure lift ratio and ejector efficiency. The COP and ΔCOP increase when the compressor rotation speed decreases under our test conditions; simultaneously, the heat capacity decreases.
•The ejector and cooling performances of a transcritical CO2 ejector-expansion system were studied.•A new coefficient was defined to estimate the deviation between current operating state and a ...steady state.•The primary flow pressure has an optimal value only for relatively high back pressure conditions.•Both the entrainment ratio and COP decrease with an increase in the coefficient of mass balance.
A comprehensive experimental study on the ejector and cooling performances of a transcritical CO2 ejector-expansion system is presented. The ejector performance of the entrainment ratio, pressure lift ratio, and efficiency were investigated under various primary flow pressure, secondary flow pressure, and back pressure conditions. A new coefficient of mass balance, β, was introduced based on the liquid mass balance in and/or out of the vapor–liquid separator, which was able to estimate the deviation between current operating state and a steady state. The experiment results show that the coefficient of performance (COP) ratio of the ejector-expansion refrigeration system to the basic system decreases from 18.9% to −11% with the coefficient of mass balance increasing from −0.1 to 0.1. Both the entrainment ratio and COP decrease with an increase in the coefficient of mass balance.
Irinotecan plays a crucial role in the neoadjuvant chemoradiotherapy (nCRT) of rectal cancer, but its optimal dosing is still unclear. In this study, we included 101 eligible patients with the ...UGT1A1*28 genotype of UGT1A1*1*1 (74.3%) and UGT1A1*1*28 (25.7%) and UGT1A1*6 genotypes of GG (63.4%), GA (32.7%), and AA (3.9%). All patients received preoperative radiotherapy (50 Gy/25 fractions) with concurrent irinotecan (UGT1A1*1*1: 80 mg/m2; UGT1A1*1*28: 65 mg/m2) and capecitabine (CapIri). SN‐38 concentrations were measured at 1.5, 24, and 49 h post‐administration. Patients were divided into four groups (Q1–Q4) based on the SN‐38 concentration. The complete‐response (CR) rate was the primary endpoint. The analysis demonstrated that the 49 h SN‐38 concentration was relatively optimal for predicting efficacy and toxicity. The Q4 group had a significantly higher CR rate than the Q1 group (p = .019), but also higher rates of adverse events (p = .009). We screened the recommended 49 h SN‐38, with a 0.5–1.0 ng/mL concentration range. We also validated the correlation between UGT1A1*6 polymorphism and SN‐38 concentration, along with the clinical efficacy of irinotecan. In conclusion, our study identified the relatively optimal timepoint and concentration range for monitoring SN38 concentrations and revealed the clinical significance of UGT1A1*6 and UGT1A1*28 polymorphisms in guiding irinotecan administration, offering meaningful insights for personalised irinotecan dosing.
What's new?
Addition of the topoisomerase I inhibitor irinotecan to existing neoadjuvant chemoradiotherapy (nCRT) for locally advanced rectal cancer (LARC) is a promising approach for improving patient outcome. However, severe toxicities linked to its active metabolite, SN‐38, limit its use. Here, the authors assessed the impact of SN‐38 plasma concentration and UGT1A1 genotype on the effects of irinotecan in nCRT LARC patients. Irinotecan efficacy and toxicity were predicted by SN‐38 concentration screening over a 49‐h period. SN‐38 concentrations tended to increase alongside the number of UGT1A1*6 mutation sites. SN‐38 concentration and UGT1A1 genotype can serve a valuable role in guiding irinotecan delivery.
•Additive manufacturing technology was applied to fabricate metal porous plates.•The transpiration cooling efficiencies of the 3D-printed porous plates were high.•The mechanical properties of the ...3D-printed porous plates were improved.
Transpiration cooling is an effective method to protect high heat flux surfaces such as rocket combustion chambers. However, this technology is currently not applicable for turbine airfoils as the strength of traditional sintered porous material was too low and the pore structure was uncontrollable. Consequently, developing porous media with high mechanical strength and precise geometry is important for transpiration cooling. Present study utilized the Selective Laser Melting Additive manufacturing technology to fabricate metal porous plates for transpiration cooling. Reinforcing partition walls were applied to the porous plate to further enhance the mechanical strength. Both cooling efficiency and mechanical properties were evaluated for the additive manufactured porous plates and compared to the traditionally sintered porous plate. The experimental results showed that the transpiration cooling efficiencies of the additive manufactured porous plates with partition walls approached to that of sintered porous plate, which approached to 0.7 when coolant blowing ratio was 2%. The presence of solid partition walls did not affect the cooling efficiency even for a high blocking ratio of 60%. The mechanical property was significantly improved by additive manufactured porous plate with partition walls. The ultimate tensile strength (UTS) increased by 440% compared to sintered porous material. Such results demonstrated that additive manufacturing and reinforced partition walls might be potential solutions to enhance the mechanical strength of transpiration cooling.
•Focus on the location where Tf(r)=Tpc (pseudocritical temperature).•Propose y+|Tf(r)=Tpc estimating the value of y+ at the location of Tf(r)=Tpc.•When y+|Tf(r)=Tpc<5, heat transfer enhances upward ...and decreases downward due to buoyancy.•y+|Tf(r)=Tpc=5 is the onset of heat transfer deterioration.
Convection heat transfer of supercritical pressure fluid is important in industrial applications such as supercritical power stations, the supercritical CO2 Brayton cycle, Carbon Capture Utilization and Storage, and the thermal protection for rocket thrusters. Previous research has confirmed that there are three heat transfer regions for convection heat transfer of supercritical pressure fluid flowing inside vertical tubes: normal heat transfer, heat transfer deterioration, and heat transfer enhancement. However, existing research still carries inconsistent results, especially regarding the onsets of heat transfer deterioration of supercritical pressure fluid flow in vertical tubes. Here we propose a new view, by estimating the location where local fluid temperature, Tf(r) equals to the pseudocritical temperature, Tpc, in the transversal section inside the tube, then analyzing the relationship between the location where Tf(r)=Tpc and the turbulent boundary layers in the near wall region, to identify buoyancy effects on turbulent heat transfer. By taking advantage of infrared thermometry measurement to achieve continuous wall temperature, theoretical analysis was validated by experiments of supercritical pressure CO2 in a vertical mini-tube with inner diameter of 0.953mm. The experiments were performed for a pressure of 7.6–9.5MPa, inlet mass flux from 255kg/m2s to 685kg/m2s, and heat flux from 12kW/m2 to 63kW/m2. It is found that in contrast with the previous results, when the value of y+ at the location of Tf(r)=Tpc, y+|Tf(r)=Tpc, less than 5, heat transfer enhances for upward and decreases for downward flow due to the buoyancy effect. With the heat flux increasing or mass flux decreasing, the buoyancy effect on the turbulent convection heat transfer characteristics of supercritical pressure fluid in a vertical heated tube is be featured as the following regimes: for the upward flow, from no-effect to slight enhancement, significant reduction, recovery and then enhancement; for the downward flow, from no-effect to slight weaken, and then enhancement. Moreover, the experimental results showed that y+|Tf(r)=Tpc=5 is where there is an onset of heat transfer deterioration for the upward flow in a vertical heated tube induced by buoyancy effects. The results presented provide a better understanding of the special features of the turbulent convection heat transfer of supercritical pressure fluids in mini channels.
This study presents a new modeling approach for the thermal cracking of hydrocarbon fuels at supercritical pressures. The thermal cracking process is treated as an infinite number of continuous ...microreactions at different fuel conversions, in which the stoichiometric coefficients of each species are expressed by continuous differentiable functions of the fuel conversion to consider the effects of secondary reactions. A set of thermal cracking experimental results involving n-decane was used as an example to show how to establish the differential global reaction (DGR) model with variable stoichiometric coefficients. The DGR model was implemented in a computational fluid dynamics simulation to predict n-decane thermal cracking coupled with flow, heat transfer, and wall thermal conduction. The results showed that the DGR model can more accurately predict the species mass fractions than existing global reaction models, especially for conditions when the secondary reactions strongly impact the thermal cracking. The root-mean-square error (RMSE) of the predicted mass fractions of all species was 4.2% relative to the experimental data for a conversion of 24.2%, while the RMSE was 61.1% for an existing global reaction model. The DGR model is a modified global reaction model; thus, it is computationally efficient. The stoichiometric coefficients of the DGR model determined from the thermal cracking experiments only require the species mass/molar fractions; therefore, the modeling method can be easily extended to other hydrocarbon fuels.
•A porous module with a treelike micro-channel was additive manufactured.•Coolant water automatically flowed to the heated surface without any pump.•Coolant flow automatically adjusted the to adapt ...to the changing heat flux.
Self-pumping transpiration cooling is an effective method to cool a heated surface without a pump and control system. A porous module with a tree-like micro-channel was manufactured using a metal additive manufacturing method. A metal ceramics heater was used to heat the additive manufactured porous module to test the transpiration cooling effect. The experimental results showed that the coolant water automatically flowed from the water tank to the heated surface with a height difference of 90 mm without any pump. The porous module was efficiently cooled by self-pumping internal transpiration cooling while the temperature of the micro-hole layer was approximately 373 K. The coolant mass flow rate self-adaptively increased with the increase of the heat flux. The system automatically, in a timely manner, and accurately adjusted the coolant mass flow rate to adapt to the step and sinusoidal changed heat flux, and the temperature of the micro-hole layer remained approximately 373 K. The system worked well when the porous module had different angles with the gravity direction. The heated surface was effectively cooled, even when the porous module was upside-down.
