Evaporation Rate Of Liquid Research Articles

Fractional thermal load in cryogenically cooled Yb:YLF and Yb:YAG lasers

We present a method for the direct measurement of the fractional thermal load (FTL) in cryogenically cooled laser crystals. The experimental methodology involves characterizing the liquid nitrogen evaporation rate in a dewar containing the laser crystals, allowing for the accurate determination of FTL. The FTL is measured to be 1.7 × quantum defect (QD) for Yb:YLF and 1.5 × QD for Yb:YAG under continuous wave lasing conditions. The measured FTL values are then used to calculate the temperature distribution inside the crystals as a function of pump power, and the simulation results are found to be in very good agreement with the in-situ temperature measurements using contactless optical luminescence thermometry. The method and findings presented in this work hold great potential to benefit laser engineers and scientists working with cryogenic lasers to address and overcome temperature-dependent handicaps.

Ultra-stretchable, toughened composite ionogel via synergetic hydration and hydrogen bonding interaction

The majority of existing ionogels display weak toughness, which confines their potential applications. This manuscript presents a novel study on the development of ultra-stretchable, long-term stable and toughened composite ionogels manipulating hydration and hydrogen bond interactions. By leveraging the low evaporation rate of ionic liquids and their robust interactions with water, combined with the establishment of a hydrogen bond network between polyacrylic acid and fructose, the resulting optimized composite ionogel achieved a strain capacity of 2090% at room temperature. Remarkably, its toughness is further heightened under subzero temperatures (15.6 MJ/m³), representing a significant increase compared to its toughness at room temperature (4.4 MJ/m³). To exemplify its practicality, a wearable strain sensor is fabricated for the purpose of sensing and detecting motions in subzero temperature settings, potentially leading to the creation of freeze-yet toughened, ultra-stretchable materials for novel applications.

Liquid evaporation from nanochannel in the presence of non-condensable gas by direct simulation Monte Carlo

Liquid-vapor phase change in the form of evaporation and with the confinement of nanostructures is of vast importance in many engineering applications. The direct simulation Monte Carlo (DSMC) approach was employed to simulate the liquid evaporation from two-dimensional nanochannels in the presence of non-condensable (NC) gases. The thermodynamic properties of vapor and NC gas flow fields as well as the evaporation rate of liquid were calculated. Factors such as channel opening ratio, meniscus receding depth and the NC gas density were examined to reveal their impacts on the liquid evaporation rates. The results showed that the gas mixture flow field transforms to one-dimensional away from the channel exit. The overall vapor pressure drop can be divided into that across the liquid–vapor interface, that within the channel, outside the channel, as well as that caused by the binary diffusion. The effect of NC gas on the evaporation rate was found to be the most outstanding with pinned meniscus and with a wide channel opening, in which case the normalized evaporation rate drops to 0.43. Moreover, the Maxwell-Stefan equation could capture the evaporation data with modified diffusion lengths. For receded meniscus (250 nm deep) and small opening ratio (0.417), the effective diffusion length was as large as 1.6 times that in the one-dimensional case.

Water drops on nanofiber-coated substrates: Influence of wall temperature and coating thickness on hydrodynamics and wall heat flux distribution

Heat and mass transport during drop impact or a gentle deposition onto a heated substrate depends on the surface chemistry, morphology, thermal and mechanical properties of the substrate, as well as the substrate temperature. In particular, if a substrate is coated with a porous layer of a wettable material, the drop spreading is accompanied by the imbibition of a liquid into the layer. The wetted area is significantly enhanced in comparison with the area which can be covered by a drop spreading over a bare substrate. As a result, the liquid evaporation rate increases and the evaporation time decreases. Understanding the interaction between the liquid spreading, imbibition and evaporation is important, both for enhancement of heat transfer in cooling applications and for functionalizing of porous media. In our experimental studies, a disk of infrared-transparent calcium fluoride is used as the base substrate. The disk is coated with a submicrometer layer of black chromium nitride and an electrically conductive chromium layer, used for heating of the substrate by electrical current. Nanofiber coating layers are applied on top of the chromium layer using electrospinning. The dynamics of drop spreading is captured by a high-speed camera in a side view, the imbibition is observed with a top view camera, and the temperature distribution at the substrate-coating interface is captured by an infrared camera. Based on the transient temperature field, corresponding heat flux distributions are determined. For the detailed analysis of the interplay between hydrodynamics and heat transfer, the nanofiber coating thickness and substrate temperature have been varied. It has been found that the drop drying time and maximal imbibed area depend non-monotonously on the coating thickness. Changing the initial wall temperature leads to qualitatively different distribution of the heat flux at the substrate surface.

Simulation investigation of the effect of heating temperature and porosity of porous media on the water evaporation process

Abstract In the study, carbon fiber as porous media, water and vapor as liquid and gas phases, respectively, the evaporation process of multiphase fluid in carbon fiber was explored based on the pore network model. The Micro-CT technology was adopted to reconstruct the structure of carbon fiber. The applicability of the CFD model adopted in the simulation was validated by experiment. Effect of heating temperature and porosity on the evaporation process was investigated in detail. The study found that at various heating temperatures, fluid temperature increases gradually with time, and tends to be constant when it reaches a certain temperature. When heating temperature is high, the constant temperature is large, the time to arrive the constant temperature is short. The liquid evaporation rate V e and the heat absorbed by the fluid every 0.5 s Q 0.5 increase first, and decrease gradually when a maximum value is reached. When the heating temperature is high, the maximum that V e and Q 0.5 can be obtained is also large, the required time is also short. In porous media with different porosity, fluid temperature rises to an approximate constant. V e and Q 0.5 increase first, and decrease gradually after reaching a certain maximum value. The maximum values of V e and Q 0.5 in porous media with porosity of 0.598 are the largest.

Characterization of liquid flow and electricity generation in a glass channel based evaporation-driven electrokinetic energy conversion device

Evaporation-driven spontaneous capillary flow presents a promising approach for driving electrolytes through electrically charged channels and pores in electrokinetic energy conversion devices. However, there are no literature reports of detailed flow visualization in these systems and/or experimental observations relating the liquid velocity and evaporation rate to the generated voltage and current. In this manuscript, we describe such a visualization study for a glass channel based electrokinetic energy conversion device with one of its channel terminals left open to ambient air for facilitating the evaporation process. Fluorescence microscopy was used to measure the liquid velocity in the electrokinetic energy conversion channel by observing the advancement of an electrolyte solution dyed with a neutral tracer. The accumulation of the same dye tracer was also imaged at the open terminal of this glass conduit to estimate the rate of solvent evaporation, which was found to be consistent with the flow velocity measurements. Additionally, an electrochemical analyzer was employed to record the electrical voltage and current produced by the device under different operating conditions. The highest electrical power output was derived in our experiments upon flowing de-ionized water through a 1 μm deep channel, which also produced the fastest liquid velocity in it. Moreover, the energy conversion efficiency of our device was observed to increase for shallower channels and lower ionic strength electrolytes, consistent with previous literature reports on electrokinetic energy conversion platforms.

Effect of inter-pore interference on liquid evaporation rates from nanopores by direct simulation Monte Carlo

Liquid evaporation from micro/nanoscale pores is widely encountered in cutting-edge technologies and applications. Due to its two- or three-dimensional features, the nano-porous evaporation is less understood compared to the one-dimensional evaporation of a planar liquid surface. This paper reported a novel study of the inter-pore interference effect in nano-porous evaporation, clarifying the variation in the net evaporation rate from individual nanopores when the inter-pore distance, neighboring nanopore diameter, or liquid temperature were changed. Molecular simulation results showed that the reduction in inter-pore distance could enhance the evaporation rate from nanopores by augmenting the vapor convection effect and suppressing the condensation flux. This interference effect was more pronounced at lower evaporation intensity with the evaporation flux being different by up to 25% from the one-dimensional case. The inter-pore interference was equally observed for Knudsen numbers of 0.1 and 10. Additionally, the non-uniformity in nanopore size distribution had no influence on the evaporative mass flux within the present parameter range. The non-uniformity in nanopore temperatures, however, could affect the net evaporation from individual nanopores, similarly by modulating the vapor convection magnitude in adjacent to the interface and the condensation flux. The effect of inter-pore interference is found to be essential at low evaporation intensity, which is highly relevant in industrial applications such as water evaporation under atmospheric pressure.

Simple post-treatment of cotton fabric for efficient personal moisture management

Wet comfort is an important indicator for evaluating human wearing comfort, and personal moisture management fabrics can quickly transfer sweat from the skin surface to meet the human body's requirements for wet comfort. Although cotton fabrics have an excellent water absorption capacity, the inability of moisture to transfer quickly causes the fabrics to cling to the skin and causes discomfort. Here we demonstrate personal moisture management cotton fabric by two-step grafting treatments, which are relatively simple and usually do not fall off as easily as a simple coating process. Moreover, unlike traditional double-layer or sandwich structures that absorb water and grow heavy, the fabric's quick-drying qualities are accomplished by expanding the area of water evaporation. According to the results of liquid moisture management and water evaporation rate tests, this fabric's moisture diffusion radius is 5 mm larger than that of pure cotton fabrics, and its evaporation rate can reach 0.2082 g/(m2 · d). In addition, it is also suitable for high-volume apparel fabrics. This work paves the way for personal moisture management cotton fabric.

Ignition and vapor transfer behavior of liquid fuel ignited by radiation from neighbouring liquid pool fire

Ignition of liquid fuel by neighbouring fire occurs occasionally in the oil storage farm. The ignition behavior is simultaneously affected by heat transfer and liquid evaporation of the unburned pool. The thermal exchange and vapor transfer involving ignition of extremely flammable liquids by neighbouring pool fire are investigated. The mean radiative heat flux of the pool to be ignited is calculated by implementing the double integration of the horizontal viewing angle coefficient of cylinder flame model. The threshold value of the incident heat flow for ignition of heptane pool decreases from 1.3 to 0.7 kW/m2 as the non-dimensional interval distance increases from d/D = 0.4 to d/D = 1.35. The radiation heat transfer by the neighbouring pool fire plays the principal role in the ignition of liquid fuel while the convection heat transfer plays the secondary role. The evaporation rate model of liquid fuel to be ignited by nearby pool fire is established according to heat transfer analysis of the unburned pool. The relative error of the experimental and theoretical value of evaporation rate of liquid fuel is within 20%. The critical vapor concentration on liquid level of ignition of n-heptane and ethanol fuel is 12.2% and 10.94% respectively.

A multifunctional PAN/PVP nanofiber sponge wound dressing loaded with ZIF-8-derived carbon nanoparticles with adjustable wetness for rapid wound disinfection and exudate management.

Rapid and safe disinfection and exudate management are two major challenges in infected wound care. Therefore, in this work, we developed a novel wound dressing via encapsulating ZIF-8-derived carbon nanoparticles in a hydrophilic nanofiber sponge to address severe wound infection and heavy exudate problems. The dressing can effectively kill bacteria through chemo-photothermal synergistic therapy. Meanwhile, the hydrophilic nanofiber sponge can quickly absorb wound exudate around the wound and accelerate the evaporation rate of liquid through the photothermal effect and its own structure; therefore, it is possible to remove excess liquid and regulate its wetness. In this way, it prevents the problem of wound overhydration often caused by hydrophilic dressings. In our experiment, the dressing showed good antibacterial performance and biocompatibility in vitro and could effectively control wound infection, absorb wound exudate and promote skin wound healing in vivo. Its good therapeutic effect is not only due to effective infection control and wound exudate management, but also because the structure of nanofibers similar to an extracellular matrix provides basic physical support and structural signals conducive to skin tissue regeneration.

Using the screening layer of granulated foam glass to reduce the evaporation of hydrocarbon liquids

Introduction. The open surface of evaporation of hydrocarbon liquids during their storage in tanks (reservoirs) and in case of emergency spills are the fire hazards characterized by the mass rate of evaporation. The main way to reduce the fire hazard of hydrocarbon liquids is to isolate the evaporation surface of hydrocarbon liquids using various coatings, such as pontoons or floating roofs in tanks (reservoirs), and in case of emergency spills air-filled foam can be used, etc. An effective way to reduce the evaporation of hydrocarbon liquids is to isolate the evaporation surface using light slightly hygroscopic granular materials capable of being retained on the liquid surface by the Archimedean force. The authors address the analytical-experimental evaluation of a decrease in the mass rate of evaporation of hydrocarbon liquids when a layer of granulated foam glass shields the spill surface.Calculation methodology and results. A mathematical model has been developed to describe a reduction in the evaporation rate of hydrocarbon liquids through a “dry” layer of granulated foam glass, similar to the Bouguer – Lambert – Beer law. A method of experimental evaluation of the mass evaporation rate of hydrocarbon liquids through a shielding layer of granulated foam glass of different height has been developed. Screening coefficients for a number of hydrocarbon liquids and the averaged screening coefficient were identified using the results of an experimental research into parameters of evaporation of flammable liquids (acetone, gasoline AI-92, hexane, ethanol, kerosene, diesel fuel) through a “dry” layer of granulated foam glass of the Termoisol brand (fraction 5–7 mm) obtained using the methodology developed by the authors. Dependences between the rates of liquid evaporation through different thicknesses of a “dry” layer of granulated foam glass on the pressure of saturated vapours have been established. The area height, limited by the bottom concentration limit of the vapour flame, spreading during the evaporation of tested liquids from the free surface that may also have a shielding layer of Termoizol granulated foam glass is estimated analytically and experimentally.Conclusions. The developed mathematical model and the method of experimental estimation of the mass evaporation rate of hydrocarbon liquids allows to identify the evaporation rate of hydrocarbon liquids of different classes, and it can be used to study the parameters of evaporation shielded by materials having different granulo metric compositions.

Performance and exergy analysis of solar-operated vacuum fan and external condenser integrated double-slope solar still using various nanofluids.

Productivity, distillate exergy, and energy efficiency of the conventional passive single-basin double-slope solar still is minimum, due to low evaporation and condensation rate. This research article attempts to increase the production rate, distillate exergy, and energy efficiency of the single-basin glasswool-insulated double-slope solar still by attaching novel solar-operated vacuum fan, external condenser and adding 0.1% volume concentration of copper oxide, aluminium oxide, and zinc oxide nanofluid. Inclusion of vacuum fan and external condenser enhances the production rate in the modified solar still. It is evident that as the vacuum fan exhales the vapour in the basin, the temperature of water in the basin and transparent glass are reduced significantly and so the vaporization amount increases considerably. It makes that a large amount of vapour is extracted by the vacuum fan and allowed to pass though the condenser, and therefore, the entire condensate of the solar still is increased significantly. To attain a comparative study, conventional and modified double-slope solar still of identical dimensions were developed utilizing aluminium and an experimental investigation carried out during the peak of summer. The inclusion of solar-operated vacuum fan and external condenser in the modified glasswool insulated double-slope solar still enhances the maximum energy efficiency, exergy efficiency, and cumulative production by 28.37%, 78.60%, and 64.29% due to enhancement in the evaporation rate of liquid in the solar still basin. Also, the addition of 0.1% volume concentration of copper oxide, aluminium oxide, and zinc oxide nanofluid in the conventional double-slope solar still possess the maximum increase in the energy efficiency and exergy efficiency by 20.96%, 18.01%, 10.76% and 52.53%, 38.52%, 30.35% as compared to conventional solar still without nanofluid. It is primarily due to increase in the thermal conductivity and radiative property of nanofluid. The result also signifies that the addition of 0.1% volume concentration of copper oxide, aluminium oxide, and zinc oxide nanofluid in the modified double-slope solar still possess the maximum enhancement in the energy efficiency and exergy efficiency by 21.33%, 19.36%, 17.03% and 50.11%, 36.82%, 23.75% as compared to modified solar still without nanofluid. Combined effect of using solar-operated vacuum fan, water cooled condenser, and 0.1% volume concentration of copper oxide, aluminium oxide, and zinc oxide nanofluid in the double-slope solar still enhances the maximum production rate and cumulative production by 59.26%, 55.56%, 51.85% and 96.43%, 82.14%, 75% as compared to conventional double-slope solar still. Among the three different nanofluids, the copper oxide nanofluid produced the highest cumulative production, energy efficiency, and exergy efficiency.

An Experimental Validation Study on Ferrofluid Evaporation

The current research on the evaporation of ferrofluids mainly focuses on the characterization of ultra-low vapor pressure ferrofluids in vacuum and the theoretical analysis of the evaporation process. Few studies have focused on the experimental validation of the proposed evaporation rate equations and on the comparison of the differences in ferrofluid evaporation. In this study, based on the Bolotov’s model, an evaporation rate equation is deduced from the experimental model. The experimental study included a comparison of the evaporation, magnetic particle volume fraction, temperature, height of the fluid surface from the outlet, and magnetic field of a kerosene-based ferrofluid and its base carrier liquid. The prepared sample was evaporated in a test tube, and the evaporation rate was calculated by measuring the weight loss of the sample. The experimental results show that the evaporation rate of the base carrier liquid is higher than that of the ferrofluid. The smaller the volume fraction of the magnetic particles, the greater the evaporation rate. The magnetic particles play a key role in preventing evaporation of the base liquid. The higher the temperature, the smaller the deviation of the evaporation rate from the predicted value. The evaporation rates obtained by the two control groups at the height of the fluid surface from the outlet were lower than the predict value. The magnetic field had a certain promotional effect on the evaporation of the ferrofluid. The experimental results were consistent with the results obtained using Bolotov’s model. This research validates Bolotov’s model and shows that the model is somewhat biased but still responds well to different variables.

Diffusion-kinetic model of liquid evaporation from a Stefan tube: A solution to the Stefan diffusion problem

An analytic model that describes the kinetics of the process of liquid evaporation from a vertical tube with an open end (Stefan tube) into the surrounding gas is presented. This model takes into account the intrinsic kinetics of the liquid evaporation process. The case of liquid evaporation from a Stefan tube without consideration of the Stefan flow was examined. In addition, the case of liquid evaporation from a Stefan tube with consideration of the Stefan flow was examined. In the framework of the presented model, it is shown that there are three regimes of liquid evaporation from a Stefan tube: the kinetic, diffusion, and diffusion-kinetic regimes. In the kinetic regime, the rate of liquid evaporation from the Stefan tube is limited only by the intrinsic kinetics of the liquid evaporation process; in the diffusion regime, the rate of liquid evaporation from the Stefan tube is limited only by the intensity of the mass transfer of vapor molecules from the liquid surface to the top of the Stefan tube; and in the diffusion-kinetic regime, the rate of liquid evaporation from the Stefan tube is affected by both the intrinsic kinetics of the liquid evaporation process and the intensity of the mass transfer of vapor molecules from the liquid surface to the top of the Stefan tube. The calculated data obtained in the framework of the presented model are compared with the available experimental data on the kinetics of evaporation of n-pentane, n-hexane, and water from a Stefan tube into nitrogen. As a result of this comparison, the condensation coefficients of n-pentane and water were determined.

Combustion of liquid ethanol in an innovatory vortex-tube combustor with Self-evaporating and edge-like flame properties

The combustion performance of a novel self-evaporating vortex-tube combustor for liquid fuel proposed in this study was experimentally explored by taking liquid ethanol as fuel. The new combustor was developed via installing a double-layer self-evaporating tube made of stainless steel and copper into the center of a localized stratified vortex-tube combustor. The evaporation temperature and rate of liquid fuel can be controlled by adjusting the flow rate of cooling air flowing through the tube interlayer. The effects of global equivalence ratio and fuel flow rate on the stability limit, pressure fluctuation, flame configuration, and NOx and CO emissions were investigated. The results corroborate that the novel vortex-tube combustor can achieve full evaporation of ethanol up to 30 mL/min, corresponding to a heat output of 10.57 kW. The localized stratified distribution of species formed in the combustor results in an edge-like tubular flame structure and correspondingly a wide stability limit, which enables stable ultra-lean combustion with the global equivalence ratio as low as 0.22. The pressure fluctuation amplitudes are always less than 800 Pa throughout the entire operating map. The combustor can achieve low NOx and CO emissions below 18 ppm under appropriate conditions. The high-steady combustion procedure makes the ultra-lean combustion conducted, whilst the evaporating of liquid fuel can also decrease the temperature of the post-flame zone, then reducing the formation of thermal NOx. Furthermore, the high-temperature post-flame zone locates in the fuel-rich region with high concentrations of CO and H2, which can further inhibit the production of NOx.

In-situ monitoring of wine volume, barrel mass, ullage pressure and dissolved oxygen for a better understanding of wine-barrel-cellar interactions

The process of aging wine in oak barrels causes various mechanisms that modify wine quality. This study is devoted to understanding the gas and wine transfers that occur through the barrels depending on ambient conditions. Four barrels were instrumented in a cellar to monitor the liquid's height and evaporation rates, the ullage space pressure, the content of dissolved oxygen in the wine and the environmental conditions. The liquid wine progressed slowly through the wood and reached a stabilized position after approximately 100 days. Evaporation was initially very limited and then achieved an average rate of 20 mL per day after linearization of the moisture content profile. The evaporation rate was directly impacted by the cellar conditions. The negative pressure inside the barrels, created following the loss of wine, was also affected by the cellar conditions. Above a certain negative pressure, an air percolation threshold was reached, implying the rapid entry of air into the barrel.

Thermal Performance of a Cross-flow Rotating Spray Bed

This work examined the thermal performance of evaporative cooling of water by an air stream in an equipment wherein the liquid phase is sprayed between two coaxial disks. The contact between the two phases was in a cross-current mode. The performance of the spray bed in terms of thermal efficiency and evaporation rate of liquid were calculated by varying operational parameters like air flow rate, water flow rate, and rotational speed. Both the thermal efficiency (minimum = 0.183, maximum = 0.34) and evaporation rate (minimum = 0.009 kg/min, maximum = 0.032 kg/min) increased with rotational speed and air flow rate. However, the thermal efficiency decreased with liquid flow rate.

Modeling the size of small spills of pure volatile liquids for use in evaporation rate and air concentration modeling

Exposure modeling is a valuable tool for assessing chemical vapor exposures that occur during transient events such as small spills of volatile liquids. Models are available to estimate liquid evaporation rates and resulting air concentrations. However, liquid evaporation rate models require the surface area of the puddle in order to provide vapor generation rates in terms of mass per time. This study developed an approach to model the surface area of small spills of pure liquids. A theoretical equation exists relating puddle depth to a liquid’s surface tension, density, and contact angle. A contact angle is a characteristic of liquid-solid interactions at the edge of a puddle. If the depth of a puddle can be calculated and the volume of the liquid spilled is known, the surface area of the puddle can be determined. Values for density and surface tension are published. Contact angles, however, are not readily available. Five hundred and eighty experimental spills were conducted using acetone, ethanol and water. The effective contact angle for each spill was determined. Spill volumes varied from 1.0–30.0 mL. The height of the liquid release varied from 0–15 cm onto a variety of surfaces. The effective contact angle of a puddle was most strongly associated with the liquid’s polarity. The height of the liquid release and type of surface had significant, but smaller effects on the puddle size. The effective contact angle of a puddle from a spill can be estimated as ln(ϴeff) = 3.73 – 1.17 · 1χυ/f – 0.06 · h + S. In this equation, 1χυ/f is the polarity index of the liquid, h is the height of liquid release (cm), and S is a surface constant. ϴeff can be used with the liquid density, surface tension and volume to calculate the surface area of the puddle. The surface area of the puddle can then be used in evaporation rate models to determine a vapor generation rate for input to vapor concentration models.

Nanopore-Enhanced Drop Evaporation: When Cooler or More Saline Water Droplets Evaporate Faster.

The evaporation of water droplets on surfaces is a ubiquitous phenomenon in nature and has critical importance in a broad range of technical applications. Here, we show a substantial enhancement of liquid evaporation rate when droplets are on nanoporous thin film surfaces. We also reveal how this nanopore-enhanced evaporation leads to counterintuitive phenomena: cooler or more saline water droplets evaporate faster. We find indeed that, contrary to typical evaporation behavior of sessile droplets on nonporous surfaces, the droplets placed on nanoporous thin films evaporate more rapidly when salt concentration increases or when the temperature decreases. This peculiar droplet evaporation behavior is related to the key role of the steady wetted annulus that is self-generated into the nanopore network in the drop periphery, which leads to an effectively enhanced evaporation area that controls the overall evaporation process. Our results provide the prospect of conceiving fresh scenarios in the evaporation of drops on surfaces in both relevant applications and fundamental insights.

Cryostorage tank failures: temperature and volume loss over time after induced failure by removal of insulative vacuum.

To determine liquid nitrogen evaporation rates of intact liquid nitrogen storage tanks and tanks with their vacuum removed. Donated storage tank performance (LN2 evaporation) was evaluated before and after induced vacuum failure. Vacuum of each tank was removed by drilling through the vacuum port. Temperature probes were placed 2 in. below the bottom of the styrofoam cap/plug, and tanks were weighed every 3 h. Evaporation rate and time from failure to the critical temperature was determined. Storage tanks with failed vacuum have a much higher evaporation rate than those with intact vacuum; evaporation rates increased dramatically within 3 to 6 h in the smaller tanks, and time to complete depletion varied according to starting LN2 volume. Tanks with storage racks/specimens may have altered evaporation profiles compared to tanks without. Locating temperature probes 2 in. below the styrofoam cap/plug suggests that for most applications, alarms would sound approximately 1 h prior to reaching the critical warming temperature, approximately - 130 °C. External signs of vacuum loss were dramatic: vapor, frost, and audible movement of air. For the first time, we have data on how liquid nitrogen storage tanks behave when their vacuum is removed. These findings are conservative; each lab must consider starting volume, tank size/capacity, function (storage or shipping), age, and pre-existing evaporation behavior in order to develop an emergency response to critical tank failure. Times to complete failure/evaporation and critical warming temperature after vacuum loss are different; these data should be considered when evaluating tank alarm systems.