Quantitative Analysis of Frosting Characteristics on the Drip Tray of A Cryogenic Valve for LNG Ships

Cryogenic valves play a crucial role in the production and transportation of liquefied natural gas(LNG),and are primarily responsible for efficiently controlling the inflow and outflow of LNG and regulating pressure.However,due to their operation in low-temperature and high-humidity environments,crucial components such as drip trays are susceptible to frosting,which may lead to LNG leakage,thereby causing severe safety incidents.In this study,the user-defined function(UDF)is employed to redevelop Fluent,which integrates the frost growth model with the Eulerian multiphase flow model,to conduct a quantitative analysis of frosting on drip trays of cryogenic valves.The effects of environmental parameters,such as wind speed,ambient temperature,air humidity,and cold surface temperature on the growth of the frost layer were analyzed.This study reveals a limiting wind speed between 1 m/s and 2 m/s.Upon reaching this limit speed,the growth of the frost layer reaches its maximum,and further increases in the wind speed have no significant effect on the growth of the frost layer.Furthermore,the influence of the change in the flow field on droplet impingement and freezing during the growth of the frost layer is considered through the coupling method of the kinematic characteristics of water droplets and the collection coefficient of water droplets.This study identifies the influence of different parameters on the droplet impact efficiency,leading to the modification of the frost layer on the drip tray.

Numerical prediction of spatio-temporal frosting patterns of curved surface considering varying working parameters

Accurate numerical prediction of frosting patterns is essential for the efficient layout and timing defrosting of heat exchangers under frosting conditions.In this study,a numerical model is developed to predict the spatio-temporal frosting habits on curved surfaces in combination with the correlations of frost density and thermal conductivity.In the model,frost melting is considered.After verification,the frosting and heat transfer characteristics along the flow path are investigated under various structural and operating conditions.Frost thickness along the path is mainly affected by the cooling surface temperature,while the heat and mass transfer rates are strongly correlated with the humidity ratio.The proportions of latent heat and sensible heat are distributed more unevenly in parallel flow case than in counter flow case.Frost deposition is facilitated by a smaller radius of curvature of the cooling surface.More uniform frosting characteristics along the path and smaller heat transfer obstruction are presented with a smaller length-to-height ratio of the flow path.

Frost deformation and microstructure evolution of porous rock under uniform and unidirectional freeze-thaw conditions

The frost deterioration and deformation of porous rock are commonly investigated under uniform freeze-thaw(FT)conditions.However,the unidirectional FT condition,which is also prevalent in engineering practice,has received limited attention.Therefore,a comparative study on frost deformation and microstructure evolution of porous rock under both uniform and unidirectional FT conditions was performed.Firstly,frost deformation experiments of rock were conducted under cyclic uniform and unidirectional FT action,respectively.Results illustrate that frost deformation of saturated rock exhibits isotropic characteristics under uniform FT cycles,while it shows anisotropic characteristics under unidirectional FT condition with both the frost heaving strain and residual strain along FT direction much higher than those perpendicular to FT direction.Moreover,the peak value and residual value of cumulative frost strain vary as logarithmic functions with cycle number under both uniform and unidirectional FT conditions.Subsequently,the microstructure evolution of rock suffered cyclic uniform and unidirectional FT action were measured.Under uniform FT cycles,newly generated pores uniformly distribute in rock and pore structure of rock remains isotropic in micro scale,and thus the frost deformation shows isotropic characteristics in macro scale.Under unidirectional FT cycles,micro-cracks or pore belts generate with their orientation nearly perpendicular to the FT direction,and rock structure gradually becomes anisotropic in micro scale,resulting in the anisotropic characteristics of frost deformation in macro scale.

Frost Resistance of Pervious Concrete Mixed with Waste Glass Powder

The contents of waste glass powder(WGP)(0%,10%,15%,20%,25%)and water-binder ratio(W/C)(0.24,0.26,0.28)were used as influencing factors,and the quality loss rate(Δm)and compressive strength loss rate(Δfc)were used as characterization parameters.The Ca/Si ratio and main element contents of C-S-H gels with different WGP content were investigated by energy dispersive spectrometry(EDS).The pore structure evolution characteristics of WGP composite cementing materials were investigated by low field nuclear magnetic resonance(NMR).UsingΔfc as the index of frost resistance degradation and Weibull function,the frost resistance degradation of glass doped pervious concrete(WGP-PC)was modeled.The results show that,with WGP,for the same number of cycles,Δm andΔfc decrease and increase with the increase of WGP.Under the same WGP content,Δm andΔfc decrease first and then increase with the increase of W/C.After 100 freeze-thaw cycles,the samples with WGP content of 20%and W/C of 0.26 have the best freeze-resistance.Microscopic tests show that with the increase of WGP content,the Ca/Si ratio of C-S-H gel decreases at first and then increases with the increase of WGP content.The extreme value of Ca/Si is 2.36 when WGP is added by 20%.The pore volume of hardened paste with 20%WGP content decreased by 18.6%compared with that of cement system without WGP.The overall compactness of the specimen was improved.On the basis of the test data,a life prediction model was established according to Weibull function.The experiment showed thatΔfc could be used as a durability degradation index,and the slope of the reliability curve became gentle after WGP was added,which reduced the damage degradation rate of PC.W/C was 0.26.It's about 5000 hours.

Numerical simulation on the frosting and heat transfer characteristics of plate-fin heat exchanger considering confinement effect

In refrigerating industry,frost commonly deposits on the confined cold surfaces of heat exchangers,which affects the heat transfer performance.Along the confined flow path of the heat exchanger,the frosting at downstream is affected by the parameters from the upstream.In this study,a numerical model considering the confinement effect has been proposed to predict frosting characteristics in plate-fin heat exchanger.Convection-diffusion equations for humid air and empirical correlations for local frost density are employed in the numerical prediction.Frosting behavior and heat transfer in the confined channel are investigated with different humid air parameters and cold surface temperatures.The results indicate that frost thickness in the confined channel is thicker than that in open space under the same inlet parameters.The frost layer is thicker and fluffier along the confined channel.In addition,the air temperature difference between inlet and outlet of the confined channel enlarges with frosting.Under the same average temperature of upper and lower surfaces,the heat and mass transfer of frosting are enhanced with diminishing temperature difference of upper and lower surfaces.In such condition,frosting is mainly influenced by the cold surface with the lower temperature.

Analysis of a Rare Heavy Rain Weather Process in Autumn in Ulanqab City

Based on the conventional observation data and NCEP/NCAR reanalysis data,the circulation situation,influencing systems and causes of the heavy rain during September 20-21,2010 in Ulanqab City were analyzed from the evolution process of weather circulation situation and the changes of various physical quantity fields.The results show that there was an obvious frontal zone between 45-52°N,which brought strong cold air.The transport of warm and humid air outside the subtropical high and typhoon was the main water vapor source of the strong precipitation,and the southwest jet at 700 hPa transported abundant water vapor.There was a broad inverted trough to the south of 45°N,with a central value of 1000.0 hPa.Ulanqab City was on the top of the inverted trough,stable and less moved,which was conducive to the occurrence of systematic heavy precipitation.The rainstorm was a strong precipitation process caused by the intersection of cold air brought by the southward movement of the upper frontal zone and warm and humid air outside the subtropical high.After the precipitation,the invasion of strong cold air brought frost and cold wave weather to Ulanqab City.

Frost heaving force considering synchronous damage to tunnel lining and surrounding rocks under freeze—thaw cycles

In areas with seasonal freezing,when the tunnel lining concrete is saturated with water infiltrating the interior,the lining and the surrounding rocks will simultaneously freeze.However,the current calculation of the frost heaving force fails to consider the synchronous damage to the lining and surrounding rocks under freeze-thaw cycles.Therefore,as per the elastic calculation model of the frost heaving force and model of steady-state heat transfer of circular tunnels,this study introduces the frost heaving rate of lining and surrounding rocks.First,the analytical solution of frost heaving force is obtained for simultaneous frost heaving of lining and surrounding rocks under any steady-state temperature field.Then,based on the fracture theory and meso-damage mechanics,the damage variables of lining and surrounding rocks under freeze-thaw cycles are extracted,representing their elastic modulus and porosity.Finally,the formula of frost heaving force for synchronous damage to the lining and surrounding rocks at any steady-state temperature field is obtained.The calculation results demonstrate that the lower the temperature inside the lining,the greater the frost heaving force.With the increasing number of freeze-thaw cycles,frost heaving force tends to gradually increase initially,reaching a peak value at 85 freeze-thaw cycles,decreasing to 80%of the peak value at 140 cycles before reaching a constant value.The lining participates in frost heaving,increasing the frost heaving force.The initial increase rate of frost heaving force is 15.7%.Changing the fitting coefficients s1 and s2 of the lining and surrounding rocks can effectively control the magnitude of the frost heaving force in the tunnels.

Assessment of the spatial extent of permafrost in the Upper Indus Basin(UIB)

Climate change differentially influences the frozen ground,a major dynamic component of the cryosphere,on a local and regional scale.Under the warming climate with pronounced effects reported at higher altitudes,the characterization of the frozen ground is very important in the Upper Indus Basin(UIB),an important and critical region with respect to climate and hydro-glaciological dynamics.In this study,the efficiency and reliability of the surface frost number model are assessed in delineating the spatial extent of different classes of frozen ground in the region.The daily MODIS land surface temperature(LST)with ground surface temperature(GST)and surface geomorphological expressions as ground validation datasets are used jointly in efficiently determining the extent of different classes of frozen ground(continuous and discontinuous permafrost and seasonal frost).The LST and GST resonate with each other in the annual cycle of temperature variation,however,with mean annual LST exhibiting an offset(cold bias)of 5 to 7℃relative to mean GST.This study shows that the highest permafrost extent is observed in areas where the lowest thinning rates of glacier ice are reported and vice versa.The surface frost number model categorizes an area of 38%±3%and 15%±3%in the UIB as permafrost and seasonal frost,respectively.Based on the altitude model,the lower limit of alpine permafrost is approximated at a mean altitude of 4919±590 m a.s.l.in the UIB.The present study acts as preliminary work in the data sparse and inaccessible regions of the UIB in characterizing the frozen and unfrozen ground and may act as a promising input data source in glaciohydro-meteorological models for the Himalaya and Karakoram.In addition,the study also underlines the consideration of this derelict cryospheric climatic variable in defining and accounting for the sustainable development of socio-economic systems through its intricate ramification on agricultural activity,landscape stability and infrastructure.

Effects of transient temperature gradient on frost heave of saturated silty clay in an open system

Frost heave in seasonally frozen regions is a one-dimensional process that could severely damage infrastructure subgrades.Stress state,temperature and water migration are important factors for frost heave.This work investigated the effects of soil temperature and volumetric water content on the transient frost heave ratio during the freezing of saturated silty clay in an open system and analyzed the relationships between the transient frost heave ratio and freezing rate and between temperature gradient and frost heave rate.The results show that the frost heave ratio,frost heave rate,and freezing rate are positively correlated with the temperature gradient since the temperature gradient drives the water migration during freezing,indicating the transient temperature gradient could be used to evaluate the frost heave of saturated silty clay.The transient freezing rate and transient frost heave ratio are logarithmically related to the transient frost heave ratio and transient temperature gradient,respectively.The effects of transient temperature gradient on frost heave are the principal mechanism responsible for different frost heave characteristics and uneven frost heave along a subgrade of the same soil type.

First Record of the Genus Wijayarana (Anura, Ranidae) from Yunnan, China

Dear Editor,e family Ranidae is one of the largest and most families of amphibians(Che et al.,2007),with 64 recognized genera and429 species(Frost,2022).However,the systematics and natural history of some ranid groups have not been well-studied.One such example is the taxonomic relationship between Sylvirana,H ylarana and other closely-related taxa(Che et al.,2007;Pyron and Wiens,2011;Oliver et al.,2015).China has a large diversity of ranid frogs,with 146 speciesbelonging to 7 genera,and48 species belonging to 7 genera in the southern province of Yunnan(AmphibiaChina,2022).

Influence of thermal insulation layer schemes on the frost heaving force in tunnels

In extreme cold regions,a thermal insulation layer(TIL)is commonly employed to mitigate the detrimental effects of frost heaving forces in tunnels.Optimizing the laying scheme of TIL,specifically minimizing frost heaving forces,holds considerable importance in the prevention of frost damage.This research developed a two-dimensional unsteady temperature field of circular tunnels by using the difference method(taking the off-wall laying method as an example)based on the law of conservation of energy.Then,the frozen circle and water migration coefficient were introduced to establish the relationship between the temperature field and frost heaving forces,and a reliable methodology for calculating these forces under the specific conditions of TIL installation was developed.Then(i)the influence of the air layer thickness of the off-wall laying method,(ii)different laying methods of TIL,(iii)the TIL thickness,(iv)the thermal conductivity of the TIL,and(v)the freeze-thaw cycles on the frost heaving force were investigated.The results showed that the frost heaving force served as a reliable and effective metric for evaluating the insulation effect in tunnels.In order to avoid frost damage in compliance with the design requirements,the insulation effects from various laying methods were established,in descending efficacy order as follows:off-wall laying,double layer laying,surface laying,and sandwich laying.Our findings revealed that the optimal thickness for the air layer in the offwall laying method was 0.10 m.The insulation effect of materials with a thermal conductivity below 0.047 W/(m·℃)was furthermore found to be good.Under freeze-thaw cycle conditions,it is concluded that to prevent frost damage,the TIL thickness should be the sum of the thickness r1 of the first freeze-thaw cycle without frost heaving forces and an additional reserve value 0.06r1 of the TIL thickness.

Dynamic response characteristics of a circular lined tunnel under anisotropy frost heave of overlying soil at the tunnel portal section in cold regions

The rapid development of traffic engineering in cold regions and its consequent problems need to be considered.In this paper,the dynamic response characteristics of the tunnel portal section in cold regions with harmonic load acting on the lining were studied in the frequency domain.The lining is in close contact with the frozen soil,and there is relative movement between the frozen and unfrozen soil due to the phase change.The analytical solution of the vibration of tunnel portal section caused by the harmonic load acting on the lining was derived under the consideration of the anisotropy frost heave of overlying soil.Based on the continuity conditions and boundary conditions,the undetermined coefficients were obtained,and the analytical solutions for different medium displacements and stresses of the cold-region tunnel system were acquired.The vertical pressure coefficient was equivalently simplified as a variable that could be used to replace the thickness of the overlying soil above the tunnel.The analysis of the parameter model shows that the change of the medium parameters(lining,frozen,and unfrozen soil)affects the circumferential stresses,the radial displacements and their peak frequencies of the soil.For example,the increase of density ratio of tunnel lining to frozen soil decreases the radial stresses of the frozen and unfrozen soil;the increase of volumetric frost heaving strain of the frozen soil increases the radial displacements of the frozen surface and decreases the stability of the frozen surface;the increasing of thickness of the frozen soil significantly reduces the radial displacement of unfrozen soil at dimensionless radius η=4.5 compared with that of frozen soil at η=1.5.

New semi-analytical approach for ice lens heaving during artificial freezing of fine-grained material

The calculation of frost heaving with ice lens formation is still not standard for construction projects using artificial ground freezing(AGF).In fine-grained material,ice lenses may initiate and lead to significant heaving at the ground surface,which should be considered in advance.However,the complex processes during ice lens formation are still not fully understood and difficult to capture in a simple approach.In the past,the semi-analytical approach of Konrad and Morgenstern used one soil constant,the“segregation potential(SP)”.It has been mainly and most successfully applied to the heave calculation of natural-induced soil freezing in cold regions.Its application to AGF has been so far unsuccessful.To solve this,a new semi-analytical approach is presented in this paper.It includes AGF conditions such as bottom-up freezing,temperature gradients to reach great freezing velocities,and a distinction between two freezing states.One is the freezing-up state until a certain frost body thickness is reached(thermal transient state),and the other is a holding phase where the frost body thickness is kept constant(thermal quasi-steady state).To test its ability,the results are applied to another freezing direction,the top-down freezing.The new approach is validated using two different frost-susceptible soils and,in total,50 frost heave tests.In the thermal transient region,where the SP is applicable,the two semi-analytical approaches are compared,showing improved performance of the current method by about 15%.

Experimental study on mechanical and frost heave behaviors of silty clay improved by polyvinyl alcohol and polypropylene fiber

Silty clay is widely used as subgrade filler in cold regions,which suffer from frost heave in winter and mud pumping in spring.In this study,polyvinyl alcohol(PVA)and polypropylene(PP)fiber were used to improve the mechanical and frost heave behavior of silty clay in cold regions,and the direct shear test and one-dimensional frost heave test were employed in studying improvement effects.Moreover,improvement mechanisms of PVA and PP fiber were analyzed based on test results.The main findings are as follows.(1)Both PP and PVA can heighten the strength of silty clay and suppress frost heave,but the PVA solution has a more decisive influence on improving mechanical properties than PP fiber.(2)The improvement mechanism of the PVA solution is cementing.The improvement effect of 2%PVA solution is the best,which can increase the shear strength by approximately 40%–60%at different stress levels and decrease the frost heave ratio from 0.89%to 0.16%at optimal water content.(3)For 2%PVA improved samples,0.25%PP fiber can further increase soil cohesion by approximately 20–30 kPa at different stress levels and further decrease the frost heave ratio from 0.16%to 0.07%at optimal water content.The improvement effect is neglectable when the PP fiber content exceeds 0.25%.Overall,2%PVA with 0.25%PP fiber is the optimum combination to improve silty clay in cold regions.

The NMR core analyzing tomograph:a multi-functional tool for non-destructive testing of building materials

NMR is becoming increasingly popular for the investigation of building materials as it is a non-invasive technology that does not require any sample preparation nor causes damage to the material.Depending on the specific application it can offer insights into properties like porosity and spatial saturation degree as well as pore structure.Moreover it enables the determination of moisture transport properties and the(re-)distribution of internal moisture into different reservoirs or chemical phases upon damage and curing.However,as yet most investigations were carried out using devices originally either designed for geophysical applications or the analysis of rather homogeneous small scale(<10 mL)samples.This paper describes the capabilities of an NMR tomograph,which has been specifically optimized for the investigation of larger,heterogeneous building material samples(diameters of up to 72 mm,length of up to 700 mm)with a high flexibility due to interchangeable coils allowing for a high SNR and short echo times(50-80 ms).

Experimental study on the operating performance of the air source heat pump(ASHP)with variable outdoor airflow rate under the standard frosting condition

Frosting is a common phenomenon of the ASHP under the heating mode in winter,and the outdoor air flow rate flowing through the evaporator of the ASHP was always thought to be a major contributor.In order to validate its contribution,effects of outdoor fan airflow rate on the performance of air source heat pumps(ASHPs)were investigated under the winter heating condition.The experiment was conducted in a laboratory at the standard 2℃ air dry bulb temperature(DB)/1℃ air wet bulb temperature(WB)frosting condition,which enabled the analysis of the operating performance,frosting performance,and heating performance of the ASHP unit by changing the airflow rate of the outdoor fan.Results showed that as the airflow rate of the outdoor fan reduced from 100%to 36%,the operating performance decline and the elevated frosting-defrosting loss were observed.Meanwhile,both the frosting rate and the operating efficiency during frosting-defrosting cycles showed an increasing trend then followed by decreasing tendency.The maximum frosting rate and operating efficiency were 0.92 g/m^(2).min and 2.92,respectively,which were observed at 74%airflow rate of the outdoor fan of the ASHP unit.The observation implied the existence of the“minimum frosting suppression airflow rate”.At 36%airflow rate of the outdoor fan of the ASHP unit,however,the performance of the ASHP unit was attenuated greatly,with the frosting-defrosting efficiency loss coefficient of 0.47,the heating capacity and COP reduction by 51.5 and 38.8%,respectively.These findings provided significant references to the optimization of ASHPs performance with variable airflow rate of the outdoor fan under frosting conditions.

保持边缘的SAR图像滤波方法

首先阐明了SAR图像边缘和边缘保持的概念。其次 ,提出了一种评价平滑图像边缘保持的方法。通过计算发现 ,常用的标准滤波方法 :增强Lee滤波、Kuan滤波、增强Frost滤波和GammaMAP滤波的边缘保持能力很差。最后发展了一种能保持边缘的SAR图像滤波方法。这种方法是对Han等人去除SAR图像斑点噪声方法的改进 。

中文Frost多维度完美主义问卷的信效度检验

目的:检验中文Frost多维度完美主义问卷(FMPS)信效度。方法:共有1280名大学本科生作为被试填写了FMPS问卷,其1000名被试的数据用于探索性因素分析,另外280名被试的数据用于验证性因素分析。部分被试被要求填写测量焦虑、抑郁、强迫等心理困扰的问卷,作为效标效度检验。结果:中文版Frost多维度完美主义问卷由五个维度组成。各维度的项目载荷在0.45～0.78之间。五个因素(担心错误、条理性、父母期望、个人标准和行动的疑虑)可以解释总方差的53.7%。各维度的内部一致性系数为0.64～0.81,重测信度为0.63～0.82。中文FMPS与焦虑、抑郁、强迫等心理困扰也有显著的相关,其中“担心错误”和“行动的疑虑”与各种心理困扰的相关系数在0.30～0.70之间。结论:中文FMPS的维度结构与其英文原问卷相似,且具有令人满意的信效度,适合在中国文化环境下使用。

生物力学因素在股骨头坏死发生发展中的作用研究进展

股骨头坏死是骨科常见疾病,其发病因素尚不完全明确。股骨近端以其特有的悬臂梁结构在人体运动过程中承受数倍于体质量的负荷,在传递外部载荷中发挥重要的生物力学作用。股骨头坏死相关生物力学理论有骨重塑理论(股骨头内小梁的形态结构和排列方式随外部载荷可逐渐改建。若股骨颈骨折时复位不良,可导致松质骨力学强度逐渐下降进而坏死)和Frost力学调控假说(股骨头内小梁结构在外部载荷下可发生不同程度的变形,若变形过大可导致微骨折增多、力学强度下降,进而进一步增大小梁变形程度而发生恶性循环,最终导致股骨头坏死)。生物力学因素在股骨头坏死发生发展中发挥作用,且已通过动物实验、临床试验、数字化骨科方式得到验证。

强迫性障碍完美主义心理及防御方式的病例对照研究

目的：探讨强迫性障碍患者的完美主义心理特点及其与心理防御机制之间的关系。方法：在本病例对照研究中，选取71名符合ICD一10精神与行为障碍分类中强迫性障碍诊断标准的门诊或住院患者（病例组），及71名按照性别、年龄（±5岁）、受教育程度进行配比的无精神障碍的志愿者（对照组），用中文Frost多维度完美主义问卷（ChineseFrostMultidimensionalPerfectionismScale，CFMPS）、防御方式问卷（DefenseSt），lesQuestionnaire，DSQ）进行调查。结果：病例组的CFMPS总分[（88．5±16．2）vs．（63．0±10．7）]和担心错误[（16．4±6．4）vs．（11．6±4．0）]、行动的疑虑[（14．6±3．6）vs．（8．8±2．7）]、条理性[（23．4±5．3）vs．（17．2±4．1）]、个人标准[（19．6±5．1）vs．（14．8±3．7）]、父母期望[（14．5±5．0）vs．（10．7±3．5）]维度分，及DSQ的不成熟防御机制[（4．8±0．6）vs．（3．7±0．6）]、中间型防御机制[（4．9±0．5）vs．（4．2±0．6）]因子分均高于对照组，而DSQ的成熟防御机制因子分低于对照组[（3．8±0．6）vs．（5．7±0．8），P〈0．05]。完美主义总分与不成熟防御机制、中间型防御机制正相关（r=0．58，0．44，P〈0．01），与成熟防御机制负相关（r=-0．58，P〈0．01）。Logistic回归分析显示行动的疑虑是强迫性障碍的危险因素（OR=1．46；95％CI=1．09～1．94）。结论：强迫性障碍患者可能比正常人更追求完美，更多使用不成熟和中间型防御机制。