Questions related to Phase Change
I am trying to predict temperature distribution in laser melting process using FEM. It is a 3D transient heat conduction problem.
I have modelled it without considering phase change at the melting temperature of metal, but I am not able to understand how to incorporate the phase change, particularly how to handle the nonlinearities associated with the phase change (the latent heat, enthalpy as well as heat conductivity might not be continuous at the point of phase transition)?
Please provide some resources or any kind of help will be helpful.
I have a 750 ml reactor and working volume is 300 ml. my working temperature is 350 C. By using ideal gas law i found at the pressure to be around 2 bar. But I need final pressure build up @ 350 C to be around 25Mpa in order to keep my solvent in liquid phase. So, how should i calculate the initial head space pressure required. I'm planing to use N2 gas for pressure build up
The dirac delta function delta(n) is often approximated as the magnitude of the gradient of the color function "c" since it has the property of being non-zero only at a phase boundary. However, unless this magnitude is normalized, its value will always change based on grid resolution in discrete form.
Source terms used in phase change in the context of VOF are by definition only active at the interface and therefore are multiplied by the magnitude of the gradient of the color function, however in all the literature I've read so far that magnitude is never normalized which motivates my question.
How is it that one can using the dirac delta based on the VOF definition without taking into account the fact that on a discrete level the magnitude changes with grid resolution?
In Ansys Fluent, there is an option to solve your multiphase flow problem using either Eulerian, Mixture or VOF models. Can we analyze phase change of water to steam using VOF?
I am trying to model the OCV of an electrochemical reaction where: ACT(g) + 2H+ + 2e- --> IPA(l), at T = 25 Celcius (Standard Temperature) and P = 19.6 KPa (P < Standard Pressure). The phase change occurs due to the low pressure and the differences in saturation properties between these substances. Any help is appreciated.
During latent heat storage, the temperature of the material remains the same. So the question is what parameter changes during latent heat so that the energy stored inside the PCM material can be directly calculated as a function of X (just like we can calculate the energy in material as a function of temperature for sensible heat storage). I believe one of the parameters that changes are density. But what is the relation between the density of PCM material and energy content in it?? I am just stuck here.
Is there a way to determine the amount of heat sored in PCM material as a function of X (some simple equations) at any given time?
Also is the rate of energy stored constant during the phase changing process??
To my understanding, liquid pressure/stress can not drop below absolute zero as it would reach vapor pressure first and undergo a phase change. However, would it be possible that the liquid pressure go below zero under transient conditions where the pressure gradient undergo a rapid change in direction and magnitude?
I am going to simulate condensation of moist air using ANSYS-Fluent (only 20% water vapor and the rest is non-condensable gas). How should I set this up?
We believe we need to write UDFs for the phase change process. But what is the best multiphase approach?
(In VOF, there are different mass transfer mechanisms. In an "evaporation-condensation" model, only Lee model is available; we don't use it in this simulation.)
Please share with me your ideas and also any relevant theses or papers.
I am trying to understand the phase change boundary layer formation for flow between two parallel plates. Both plates are at -20 degrees and the water inlet temperature is 10 degrees. I am initially trying to visualize the phase change boundary layer (i.e., ice layer) on both plates. Trying to understand the steady-state case.
However, velocity & thermal boundary layer formation is perfect. Once I switch on the solidification/melting model in FLUENT, the solution becomes wrong. Velocity and thermal boundary layer becomes wrong and no phase change happens.
Any help/insight is greatly appreciated.
Can we see a phase change in the cyclic voltammetry plot of a faradaic reaction for Supercapacitor, If yes please tell me how?
Using metal wire as the spraying material, through the high-energy density and large current to generate ohmic heating, the metal wire rapidly undergoes solid→liquid→vapor→plasma phase change, resulting in an electric explosion. The explosion shock wave is used to partially melt but not vaporize The metal droplets are sprayed on the surface of the workpiece at a high speed to form a high temperature and ablation resistant coating.
Is that possible for inner coating for oil and gas pipeline if outer diameter 139.7 (5-1/2) and inner diameter 127.3 (5.012)?
Kindly, I hope if I see you answers. I appreciate your advices and guidance for me.
I am trying to realize the method in the literature:
A New Efficient and Stable 3D Conformal FDTD
and got the simulation result in the attached picture. The phase of S11 changed 180 degrees suddenly, what's the possible explanation for this? A bow tie antenna is simulated. In traditional FDTD, the phase changes gradually.
I want to simulate the phase change through out the heat exchanger that may be used in refinery by fluent. The point where the phase of oil will change is very important in this type of stations ,how I can find it or indicated using fluent.
We have synthesized certain electrode material for DSSC application and coated electrodes material on FTO. We have connected one electrode with counter and reference electrode assembly and the other one with working and sensing electrode assembly. The electrolyte has been immersed between both electrodes. However, we are not getting proper Nyquist plot as well as bode plots, as you can see there is no phase change with varying frequency.
I want to know is there any way to do nonlinear simulation in lumerical interconnect except using the thermal nonlinear waveguide? I designed a waveguide and import the properties from FDE to interconnect. Now I want to see some nonlinear aspect of it by setting up a high power loopback system. Will it be possible to see any phase changes in the loopback in Lumerical interconnect?
Hi. I am simulating a rotating heat pipe with phase change. It is divided into three sections, evaporator, adiabatic part and condenser. I have an initial fill ratio of 8% liquid. I have big problems for phase change. Using Lee's model either via UDF or as a standard fluent model I cannot observe the phase change. I also have problems with turbulent viscosity instability which leads me after a short while to Courant Number over 250 and diverging solution. Do you have any suggestions? My idea is to implement a new multiphase model, Sun's model via UDF, as mentioned in the paper I am referring to. Big problem is the inability to write the udf of this model, do you have any suggestion or help to give me please? I will leave the model below.
I am modeling a simulation where in I have a heat source from outside which tracks the effect of PCM on heat storage and better evaporation of the other fluid.
Evaporation and Condensation model was added to one fluid whose Liquid Fraction is to be tracked. I want to add a Phase Change Material using Solidification/ Melting Modeling which will affect our dominant fluid. How do you I carry out both in ANSYS Fluent? As soon as I select the VOD modelling, and give PCM Cell Zone a fluid material input, it considers the PCM also to be part of VOF. I want it to be a separate fluid just undergoing phase change and no interaction with dominant fluid.
I need two model heat exhanger between air and water. But air will be admitted in liquid state at negative temperature and on leaving the heat exchanger it should be in gaseous state.
In this problem two fluids are involved
Once again Air has enter in
On transferring heat from water it has to be converted to
I'm aware interphasechangefoam for phase change and CHTMultiregionfoam for two fluids. But in this case two fluids are involved. In this two fluid, one fluid has to undergo phase change.
Dr. Ijaz Fazil.
Many literatures pointed out that soil sand content has a greater contribution to soil thermal conductivity. However, I couldn't find any models that can quantify soil thermal conductivity using the results of soil particle size distribution. In frozen soils, things seems more complicated considering the phase change of soil water. I want to find a model to express the soil thermal conductivity. I just want to find a soil thermal conductivity model that takes into account both the soil phase change process and the soil mechanical composition
I want to simulate conditions inside conditions of a "Solar Still Distillating Tank". I have a few ideas like using may using phase change module in comsol or simulating vapour pressure but I don't know how to do it. Any help is appreciated. Thank You!
I‘m using the topology optimization module to optimize a time-dependent phase change problem.
After the first optimization step, these errors appear many times:
Warning: Forward solution failed, requesting reduced step.
Warning: Adjoint solution failed: requesting reduced step.
can anybody help me, how can I solve this problem?
thank a lot！
In the attached paper to resolve the FP like SPP resonance, the authors calculated the reflection phase change from the full field simulation. Can anyone kindly explain how the phase change can be numerically calculated ?
I am trying to simulate phase change process of paraffin wax inside a metal mesh. I am planning to use solidification/melting model in ANSYS (with energy, viscuous laminar ON). Do i need to use VOF with it as well? The metal mesh containing PCM is heated from the bottom with a constant heat flux and rest all sides are insulated except the top one which is under ambient condition (convective heat loss).
I am running a simulation that includes water phase changes. These phase changes will take place below the boiling point of water so I need a method that can accurately model this. From my understanding and testing so far, the evaporation-condensation model in Fluent will only simulate the phase changes at the water's boiling point. Therefore, I need to code a UDF to model the phase changes more realistically. I have looked into vapourization modeling but frankly have been overwhelmed by the number of methods and I am really unsure which to pick for my scenario. Temperature, pressure, and relative humidity all need to be taken into consideration.
Does anybody know of any models that seem well suited to my needs off the top of their heads? Also, I'd appreciate any literature/tutorials that summarise different models or their application in Fluent.
Is this possible to investigate the stability of a specific intermetallic phase with DFT calculations? Technically said, can I use the DFT calculation as an alternative of thermodynamic calculation to study the stability, component solubility range and stability temperature range for a specific ternary phase?
My model is a rectangular multi layered structure under which refrigerant flows through cylindrical pipes. A heat flux of 600W/m2 applied on panel and internal forced convection is used for refrigerant flow. Trying the phase change option from heat transfer in solids and fluids node but I am not getting any sollution.
I have water flowing at 4 GPM at 2.5 feet per second through 50ft of 0.375 in. outer diameter tubing with 0.014 in. wall thickness. The water flows through copper tubing into the 50ft coil section, which is submerged in an adiabatic container of 22lbs of ice, and then out again. How do I set up the heat transfer equation to find the time it will take the ice to melt, as well as the temperature of the water as it leaves the adiabatic container? Thank you.
I am simulating evaporation condensation model in Ansys fluent. Water heats at 250 degrees and evaporates and then reaches heat exchanger at top which cools at 70 degrees. But when vapours reaches heat exchanger it does not show any phase change from vapor to water. Kindly help me.
I hope everyone is doing well and is in good health.
In the simulation it is needed to change the phase of water that flows through an air domain. So I used Laminar Flow and Level Set physics in order to simulate the interface between air and water. At the end of the air domain, there is a Wetted Wall and water reaches this boundary. Now, if I want to change the phase of the water, how can I use Heat Transfer in Fluids--->Fluid 1--->Phase Change Material 1 for the water that is interfaced with air in one domain? When I am using Heat Transfer I have to select a domain; So the Heat Transfer does not follow the new geometry of water. Do anyone have an idea about changing phase of water in this case?
I appreciate your time and consideration.
Kindly suggest the solution of a above question rather i have already gone through Evaporation-condensation model available in it but did not get success.
I have to analyze an existing ammonia line to estimate the pressure drop in it.
The line is designed to transport liquid ammonia. I can compute the pressure drop with standard friction factor approach. If I reach a point were the pressure is small that the corresponding vapor pressure, partial vaporization is to be expected.
What method is recommended to compute the pressure drop from that point onwards??
I have a two phase flow textbook, but guidance would be helpful as to what is the recommended procedure.
I want to design a shell and tube heat exchanger with kern's method.
The problem in the two phase flow. I didn't find enough information.
I know that in the two phase section the evaporator is discretized and divided into N parts.
How I assume the value of U, and how calculate the surface area.
Hello dear researchers, I want to know the possible reasons (all possible reasons) for the phase change in single layered or thin film of 2 D materials probing under the ultra-fast laser spectroscopy?? For example if we obtained a spectrum indicated the phase change in that TMD then how can we know the underlying physics behind this change. Thanks
I'm familiar with how concepts such as the latent heat of fusion and vaporization work for a system consisting of a single phase-changing gas. q = mH, q=mc dt, all that fun stuff. I'm not familiar with any work in how these concepts manifest when the system consists of multiple gases, or how to determine how much of the heat energy is being transferred to a given component of the gas.
If I had, for instance, a gas containing oxygen, krypton and hydrogen, and I wanted to determine how much energy I'd need to put in in order to get the krypton to devaporize into a liquid while it was mixed in with the other gases, any idea how I'd go about calculating this?
Can anybody explain how to do thermal charecterization for parrafin wax.It would be of great help if any one can atleast share me journals or research papers on charecterization of parrafin wax?
Our group are investigating the influence of malonic acid on CaCO3 phase changes (calcite, aragonite, vaterite). It is evident that the carboxylic acid used (up to 20.00 ppm) was able to alter both the morphology and the crystalline phase of the CaCO3 polymorph.
However, it is difficult to analyse the phase transition through TG-DTA, as shown in the files attached.
If you could help us with the DTA analysis please.
I would like to simulate the process of heating a material in a stream of concentrated solar radiation, taking into account the spectrum of solar radiation, flux density, absorption coefficient of the material, phase changes in the material by changing the temperature of the material. how to apply the Stefan problem?
Pure deionized and degassed water were studied freezing kinetics. The sample size is 3 mL with the freezing rate 4-degree celcius/ min and freezing temperature -20 degree celcius. Temperature measurements were taken at the geometrical centre where the sample is kept in 1.5 cm diameter cylindrical glass holder. The freezing curve was studied with automatic data logger and the response was different each time. The Precooling time (time taken to decrease the temperature from 4 degrees to the ice-nucleating temperature), Ice nucleating temperature, phase transition duration (time taken for complete phase change of the sample from liquid to solid-state) were studied. The ice-nucleating temperature is the lowest temperature detected which is always lower than the freezing point.
The ice-nucleating temperature does not appear in some cases. Any possible reason? How to overcome that.
I am trying to simulate DC Casting of Aluminum Alloys in Comsol. I found an example related to Continuous Casting that it couples fluid flow, heat transfer and phase change during solidification of the liquid alloy. Is it possible to involve solid mechanics for the solidified shell that is computed from phase change model?
If it is not possible to do a fully-coupled model: Could you please tell me how can I set the model concerning only solid mechanics and heat transfer ? Is there a way in COMSOL to add in the presence of time, new layers of material while moving the boundary conditions (mold, water colling) silmutaneously, to simulate fluid flow ?
Like if for eg. Gd2O3, its phase change by pressure and temperature from cubic to hexagonal to monoclinic then there must be changes in angles and lattice parameters but is there any change in atomic positions in unit cell as composition is not changing?
I’m recently dealing with in situ XRD heating experiment of epitaxial thin film on single crystalline STO(100) substrate.
There are two problems I ran into:
1. Multiple background peaks from the heating stage. Any suggestions of how to deal with that? Especially when there are overlap of film characteristic peaks and stage background peaks?
2. The STO(001) peak seems to experience thermal expansion upon heating (which is reversible, meaning the peak position of the heating cycle overlaps with the cooling cycle). How can I get rid of this effect since there are BOTH phase change information and thermal expansion information for the film?
Anyone has similar experience in the related field can provide some reading literatures or insight? Thanks a lot!
The Eric Birse Trust was founded in 1984 by the family of Dr Eric A B Birse to commemorate his life and work. The primary intention of the Trust is to fund, via The Eric Birse Studentship, PhD research in the field of Chemical Engineering. To date the Studentship has supported eight PhD students, each of whom has progressed to have successful careers in industry and academia.
A PhD Scholarship supported by the Eric Birse Trust is available at the School of Engineering at the University of Edinburgh. The Studentship is open to all who wish to work in this discipline subject to meeting the Eligibility criteria and to complying with the Application Procedure. Student must apply with your own Research Proposal and nominate the most suitable academic within the Institute of Materials and Processes (IMP) or the Institute of Multiscale Thermofluids (IMT) to supervise this research.
More specifically at the Institute of Mutliscale Thermofluids we are carrying out research work on both experiments and computations, with an emphasis on multiscale and multiphase fluid systems interfaces and phase change from nano- to macro-scales undergoing heat transfer. Topics include phase change, wetting and associated capillary phenomena, and boiling (e.g. at microfluidic scales). IMP and IMT academics can be found using this filterable list. The closing date for applications is 31 December 2019.
This is an excellent opportunity for mentoring a young researcher in the ambit of phase-change and heat transfer. If interested and not aware of the type of project that can be carried out, feel free to contact Daniel Orejon for more information on firstname.lastname@example.org and 0131 650 5735.
Link to the Eric Birse Trust: https://www.eng.ed.ac.uk/studying/postgraduate/research/phd/eric-birse-trust-chemical-engineering-phd-studentship
Recently I have proposed a new model of vapor compression heat pump for boiler flue gas waste heat recovery. The heat pump is employed for domestic water heating. I have used air as a refrigerant.
Although air is not a phase change fluid just like refrigerant but the simulation results are quite satisfied.
Now, if I publish my work, then the reviewer can raise the questions about using of air as it doesn't goes under the phase change and it also have low COP but on the other hand use of air at ambient temperature in cold climates can save the refrigerant cost as well as air have zero ODP and GWP.
How should i justify the reviewer about using air as a refrigerant?
Will the muon disappearance and appearance event rates be affected by a change in the value of the Dirac delta CP phase?
For eg. We have muon disappearance and appearance event rates at Delta CP=0, what will be the impact on these event distributions if the value of the Dirac phase is changed to -90?
I am currently doing a gas-liquid phase change simulation, but the false phase change near the gas-liquid interface occurs due to the spurious velocity. Is there any way to reduce or eliminate this non-physical phenomenon?
Thanks for your help
I have read that to know the composition of different phases in a ternary phase diagram of metals A,B,C (at a particular temp. T), we can apply lever rule along the tie line. But, I am not sure about how to draw the tie line and how to apply lever rule along it as some procedure says to use line and few have mentioned smaller triangles to draw (tie-triangles) to know the composition of the phases. Kindly illustrate on the concept. Thanks in advance for help.
In FLUENT, the only model available for phase change simulation is the Lee model.
Are there other models?
And there is an option to include only a single Saturation temperature. Can the entire P-T graphs be plotted into FLUENT for best results in phase change simulation?
Your help is heartily appreciated.
It is often said that there is a phase change in battery type material and no phase change in the intercalation pseudocapacitance. So can I assume that if our material's crystal structure is cubic in case of battery then it will change into hexagonal or something else phase during charging or discharging process. And this doesn't happen in intercalation pseudocapacitance. If it so then why it doesnt happen in intercalation ones. I am not able to pickup this point.Please help me to figure it out.
XRD of semiconductor material show phase change from crystalline to amorphous , but the optical band gap decresses, what is the reasons behind this ?
Desalination of salty groundwater and seawater could unlock the vast water resource and provide a sustainable source of water to water-stressed regions of the world. Desalination processes have been categorized into three main areas: i) thermal or phase change processes, ii) filtration-membrane processes and iii) intensified processes which involve integration of various processes (Gude et al., 2010). However, these methods are costly.
Objectives our project are as follows:
1: To introduce an economic and viable system to the desalinated ground-waters in order to support urban and agricultural prosperity and protecting the environment.
2: To set up the introduced system in the desired region.
I am so glad that anyone gives me useful advice and experience.
Hi every one can anybody guide me which White LED ( One -chip or Multi-chip type ) is used to analyse the phase change of light signal/pulse . Thanks
Hi, a very basic question here. hope someone can help.
I have a PCM which has a very small change in density during phase change i.e. it has a density of 0.90 kg/liter in solid phase (measure at 25 deg C) and a density of 0.89 kg/liter in liquid phase (measured at 80 deg C). The PCM has a melting range of 50-51 deg C. I want to impregnate this PCM in two different metal matrices and capture the differences in convective heat transfer indicated by buoyancy velocities.
What i fear is that this small difference in density over a huge temperature range (i.e. from 25 to 80 deg C) would not create any buoyancy (basic principle of buoyancy is differences in densities as a function of temperature). Therefore, the heat transfer in liquid phase would also be largely conduction dominated. Hence, i wont be able to capture the effect of metal matrix morphology in convective heat transfer.
Did i say it right?
Let's say I have a material with a stable phase A that transitions to another stable phase B at temperature T. If the material also has a metastable phase A', I know that if I cool B fast enough I would get:
B -> A'
and if I cool very slowly I'd get
If I were to look at the interface between B and the new phase and somehow extract all possible information (energy/mass transfer, etc), what signal would indicate to me that I would expect A' (metastable) to form over A?
I have a binary system of polyalcohols. When I cool the mixture down past it's solid-solid transition point, it usually forms a metastable phase. We know this because upon reheating promptly after the cooling, the transition temperature is different than if we let the sample anneal for a few days.
Is there an alternative to annealing for several days? How can we speed up the process by which it transitions to it's stable phase? Mechanical engineer here, I apologize if this is a rookie materials science question.
We are studying a heat transfer problem of maraging steel 300. There may be a phase change (from martensite to austenite, at ~600 deg C), and I wonder if the heat associated with that phase change is significant. Is there a way to look up the latent heat or standard heats of martensite and austenite? Thanks in advance.
How to find heat transfer coefficient within sphere containing water which is still in nature and undergoing phase change?
In sub-critical thermal power cycle, the thermodynamic fluid absorbs certain amount of latent heat during phase change from water to steam but in a super critical unit, this absorption is zero. Now question is, how much this factor helps in improving the cycle efficiency of a super critical thermal power cycle?
Practising Efficiency engineers in large thermal power plants can answer this question.
I would like to ask that, is there any solid material which change its lattice arrangement (Solid-Solid Phase change Material) due to heat flow and all the heat is used in transformation rather than increasing its temperature just like when heat is provided to ice, the phase change process occurs at constant temperature, latent heat of melting (Solid-liquid phase change material).
It is know that austenizing steel produces hard martensite after quenching, and the properties of it can be improved by tempering to create better toughness while making the metal softer and more ductile.
Yet say this method is used for a piston (which was quenched then tempered at 600 degrees C). What happens to the hardness of the low alloy steel in standard operating temperatures up to 425 degrees C?
Are there any further phase changes? Can something like precipitation hardening occur or are these temperatures too low for an already QT steel.
I am using Ansys/Fluent to model the ice melting and formation in a horizontal enclosure heated (+5degC) from both upper and lower plates (melting case) and cooled (-5degC) from both plates (freezing case).
For this purpose I am using a fixed grid method (enthalpy-porosity approach) where the mushy zone is considered as porous (applying the Darcy law).
The density was defined in the liquid fraction, meshy zone and solid fraction in order to account for the non-linear behaviour of the water density which is characterized by a maximum at 4degC:
In the liquid phase the density was defined as given by Gebhart and Mollendrof
In the meshy region I used a linear interpolation between the density of water in liq and solid phase
In the solid phase, the density was set to that corresponding to the solid fraction.
The phase change temperature range was set to ( -0.5..0.1deg C) --> Tsolidus=-0.5 and Tliquidus=0.01degC
All properties were defined using a piecewise linear functions to define properties in both phases.
Due to the relatively large density difference between the solid and liquid phases, it is supposed that the buoyancy forces will make the ice block floating upwards as it is melting. This is not a "real movement" as I am using a fixed grid (and not a moving mesh), but it is the change in the cell properties that will characterize their fractions and then "simulate a floatting"
Unfortunately this phenomena was not captured by the enthalpy-porosity method!
Someone can help?
Many thanks :)
I have a very basic question regarding the presence of interface ( presence of surface tension to be precise) between liquid or gas phase with supercritical phase.
For instance, consider oxygen (Tc ~ 150 K, Pc ~ 50 bar).
Let us consider:
1. Case 1 wherein liquid oxygen (T and P > Tc, Pc, say 100 K and 45 bar) is injected into a chamber filled with gaseous oxygen ( say T = 130 K, P = 45 bar). Then if I understand well, then there will be phase change and we will have surface tension present between these phases.
2. Case 2: Oxygen above the critical point (say T = 160 K, 55 bar) injected into supercritical oxygen say T = 180 K and 55 Bar), Both are in supercritical phase. In such case there will be just diffusion ( which I understand is due to difference in concentration/density and thus self diffusion). No interface or effects of surface tension will be present.
3. Now let us take a case, say liquid oxygen is injected into supercritical oxygen.
For sake of convenience, say initial T = 120 K and P = 60 bar ( i.e above Pc but below Tc), and injected into supercrtical phase of oxygen. ( T = 180 K, P = bar).
Is this case similar to case 2 or case 1 described above.
My main concern was will there be surface tension present or will there be just diffusion.
( I am assuming here that at no local point, the T and P will fall below Tc,Pc to avoid any liquid --> gas conversion)
More precisely, will it be reasonable to consider surface tension in analytical/numerical computations?
To my understanding, we incorporate surface tension to account for increase in energy due to interfacial energy/latent heat.But here we don't have anything of this sort but as we have liquid and Supercritical state, it's slightly confusing.
How will things change when instead of liquid injection, we do same case with gas state ( say T = 190 K, P = 40 bar i.e. T> Tc , P < Pc)
I'm trying to simulate the solidification and melting process of a PCM in ANSYS Fluent, using solidification and melting module. To do so, since properties for solid and liquid phases are different, I'm trying to apply these difference for these two phases separately. I've already tried using piecewise function for tempratures over and below phase change temprature. But it causes divergence in my simulation.
The thermal radiation is dependent on Temperature , and since during phase change (latent heat) the temperature stays the same, I was wondering whether the thermal radiation (intensity) would also stay the same?
Clouds are important for their hydrological, thermodynamical, and radiative effects. That is, they redistribute water all over the globe, transport energy by up-taking and releasing the latent heat, and scatter/absorb solar and terrestrial radiation fluxes.
One question lingering in my mind is: which cloud phase (i.e., ice & liquid) possesses the most cloud water? Ice or Liquid? The reason I am interested in this question is that the understanding of the facts of cloud phase and its representation in climate models are relevant to various key problems, for example cloud microphysics (aerosol-cloud-precipitation interaction) and cloud radiative feedback (how cloud phase change modulates the scattering/absorption properties of clouds in a warming climate).
I have sawn some publications (e.g. Huang et al., 2015, JGR, doi:10.1002/2014JD022779) showing that there is more ice water than liquid water, globally. But I also found the retrieval of cloud water, especially ice water, suffer from tremendous uncertainty. So, I want to hear from the many talented people here, about your knowledge and opinions on this question. Thank you very much.
The evaporation wave, or "free surface boiling", is a type of violent vaporization that occurs in absence of nucleation. I understand that the thermodynamic limit for the onset of evaporation wave could be the spinodal curve. However, the spinonal curve is also the limit of homogeneous nucleation. Thus, in the metastable region, what are the key factors that determine whether the system undergoes homogeneous nucleation or evaporation wave?
More recently, Manceau et al. demonstrated the THz polarization control via the accurate control of the surrounding gas pressure of two color filaments. The change of gas pressure will induce a wavelength dependent change of refractive index, resulting in the relative phase change of the two laser fields. What is the relationship between air pressure and refractive index? Who can help me to answer this question?