Droplet Lifetime Research Articles

High-temperature evaporation of water emulsion droplets used in thermal fluid treatment

High-temperature (over 500 K) evaporation of water, emulsions, slurries and solutions has been extensively studied over the recent years due to a number of prospective applications. Some of these are, for example, the evaporation or burnout of impurities in the course of for thermal wastewater treatment, gasification, as well as flue gas waste heat recovery by intermixing them with water and water vapor to create a new generation of heat transfer agents. Further development of these technologies is constrained by the fact that the approaches used so far are mostly empirical. Obtaining reliable experimental data on evaporation characteristics (vaporization rate and lifetime) of water emulsion droplets in the course of thermal evaporation and burnout of impurities is a pressing task. It is also desirable to experimentally cover all the temperature ranges, droplet sizes, and component concentrations, typical of advanced water treatment. In this research, we use high-speed hardware-and-software system to track the free surface of a droplet. We determine the dependence of heating and complete evaporation time as well as heating and vaporization rate on the gas environment temperature, droplet size, and emulsion component concentration. We then derive the approximating equations for the dependences determined. The difference in evaporation conditions and characteristics is also defined for droplets of water and emulsions with different additive types and concentrations. Finally, we outline different modes of evaporation as well as the required conditions for monotonous evaporation or explosive breakup (pulverization).

Evaporation of water-ethanol binary sessile drop on fluoropolymer surfaces: Influence of relative humidity

Experimental results on the diffusive drop evaporation behavior of 2 μL pure water, pure ethanol and ethanol-water binary droplets under constant relative humidity and temperature conditions were reported on two flat fluoropolymer surfaces of TEFLON-FEP and PTFE. Contact angles, droplet heights, contact radius were monitored with a camera as a function of time. A roughly linear relationship between the initial static contact angles on fluoropolymer surfaces and ethanol concentration was found similar to the previously published results. It was determined that constant contact angle mode dominated for most of the duration of drop evaporation process after the initial stages. Volumes of the binary droplets were found to decrease nonlinearly over time for all of the compositions. The most important effect of the RH increase of the medium was found to be the increase of the adsorption quantity of water vapor from the environment onto pure ethanol and also binary ethanol-water droplets. For pure ethanol droplet under high RH conditions, the rate of evaporation declined after the evaporation of most of the ethanol in 250 s, then the remaining droplet evaporated with a much slower rate which was close to, but not equal to the rate of pure water drop evaporation, indicating that ethanol was present in the droplet until to end. The same behavior was seen for ethanol-water binary droplets. Evaporation rate of the binary droplet containing 25% ethanol by wt. was observed to be close to that of pure water and 75% ethanol by wt. was found to be close to that of pure ethanol with minor differences. However, evaporation of a binary droplet containing 50% ethanol by wt. was more complicated and it is hard to distinguish ethanol and water evaporation zones for this composition and there was a long transition stage where ethanol and water evaporated together for long durations. It was found that droplet life-times were generally longer on flat TEFLON-FEP substrate than that of slightly rough PTFE due to the higher initial contact angles on the former. The change of V(2/3) values with time for pure water drop evaporation was determined to be linear under all RH conditions obeying the constant contact angle mode. The values of (dV(2/3)/dt) decreased linearly with the increase in RH for pure water. Similar, but a non-linear decrease of the (dV(2/3)/dt) slopes were determined for ethanol-water and pure ethonol droplet evaporations indicating the adsorption of water from the environment.

A discrete multicomponent droplet evaporation model; effects of O2-enrichment, steam injection, and EGR on evaporation of diesel droplet

A discrete multicomponent (DMC) model for droplet evaporation in convective ambient is developed. Three different sets of correlations for Nusselt and Sherwood number are examined. The model is compared with experimental data for single and multicomponent droplet evaporation at different conditions and the most suitable set of correlations is selected. Having validated model, the diesel droplet evaporation under different ambient conditions and compositions is investigated. Increasing of oxygen mass fraction in N2–O2 mixture ambient from 0 to 1 first decreases and then increases the lifetime. Steam addition enhances the evaporation rate and it affects evaporation more significantly at higher temperatures. Exhaust gas recirculation (EGR) results in slight variations in droplet lifetime and its heating period.

Ethanol/Gasoline Droplet Heating and Evaporation: Effects of Fuel Blends and Ambient Conditions

This paper focuses on the modeling of blended ethanol/gasoline fuel droplet heating and evaporation in conditions representative of internal combustion engines. The effects of ambient conditions (ambient pressure, ambient temperature, and radiative temperature) and ethanol/gasoline fuel blend ratios on multicomponent fuel droplet heating and evaporation are investigated using the analytical solutions to the heat-transfer and species diffusion equations. The ambient pressures, gas and radiative temperatures, and ethanol/gasoline fuel ratios are considered in the ranges of 3–30 bar, 400–650 K, 1000–2000 K, and 0% (pure gasoline)–100% (pure ethanol), respectively. Transient diffusion of 21 hydrocarbons, temperature gradient, and recirculation inside droplets are accounted for using the discrete component model. The droplet lifetimes of all mixtures decrease when ambient temperatures increase, under all ambient pressures (3–30 bar). The combination of ethanol and gasoline fuels has a noticeable impact on drop...

Evaporation of a single emulsion fuel droplet in elevated temperature and pressure conditions

The evaporation characteristics of water/n-decane emulsion droplet at various temperatures and pressures were experimentally observed. Emulsion fuel was made by adding pure water to the base n-decane fuel with a volume ratio of 0.2. Span 80 was used as a surfactant, and ultrasonification was conducted for the mixing process. The temporal variation of the droplet diameter was optically observed by using a high-speed camera, and the changes in droplet temperature were also measured. The evaporation process of emulsion droplets was divided into three stages, namely, droplet heating, inflation/puffing, and pure evaporation. As the ambient temperature increased, the behavior of droplet inflation shifted to puffing during the inflation/puffing stage. A decline in the inflation/puffing incidence rate was noted at high-pressure conditions. The evaporation rate during the pure evaporation stage and the overall droplet lifetime were affected by the ambient temperature but not by the ambient pressure. The inflation of the droplet mostly occurred at relatively lower temperature and pressure conditions; it changed to puffing, however, at higher temperature and pressure conditions.

PM from the combustion of heavy fuel oils

This work presents an experimental study investigating the formation and oxidation of particulate matter from the combustion of heavy fuel oil, HFO, droplets. The study includes results from both a falling droplet in a drop tube furnace and a suspended droplet in a heated convective flow. The falling droplets in a heated coflow air with variable temperature path and velocity were combusted and the resulting particles, cenospheres, were collected. To characterize the microstructure of these particles, scanning electron microscopy (SEM), and energy dispersive X-Ray (EDX) analysis were used. The particles were found to have either a porous or a skeleton/membrane morphology. The percentage of particles of either type appears to be related to the thermal history, which was controlled by the heated co-flow velocity. In the suspended droplet experiments, by suspending the droplet on a thermocouple, the temperature inside the droplet was measured while simultaneously imaging the various burning phases. A number of specific phases were identified, from liquid to solid phase combustion are presented and discussed. The droplet ignition temperature was seen to be independent of the droplet size. However, the liquid phase ignition delay time and the droplet lifetime were directly proportional to the initial droplet diameter.

Flame spread between two droplets of different diameter in microgravity

This research investigates the flame-spread characteristics between two droplets, Droplets A and L, of different diameter. n-Decane droplets are placed at intersections of 14 µ SiC fibers. The flame spread from Droplet A to Droplet L was observed in microgravity. The results show that the flame-spread rate decreases with an increase in the droplet spacing or the initial diameter of Droplet L for a constant initial diameter of Droplet A. The flame-spread time is approximated as the summation of the thermal conduction time from the flame around Droplet A to Droplet L and the heating time of Droplet L, which is the time required to activate the vaporization of Droplet L. Both the thermal conduction time and the heating time of Droplet L increase with the droplet spacing. The latter also linearly increases with the squared initial droplet diameter of Droplet L. The results suggest that the ratio of the heating time of Droplet L to the thermal conduction time depends roughly on the droplet diameter of Droplet L alone for a constant initial diameter of Droplet A. The flame-spread-limit droplet spacing gradually decreases with an increase in the initial droplet diameter of Droplet L and increases sharply with the initial droplet diameter of Droplet A. The flame-spread time is limited by the burning lifetime of Droplet A and about 80% of the burning lifetime of Droplet A under the near-flame-spread-limit condition. The flame-spread limit is discussed considering the burning lifetime of Droplet A, the thermal conduction time, and the heating time of Droplet L.

Functional Surfaces with Enhanced Heat Transfer for Spray Cooling Technology

In this study the effects of nano/microstructuring and surface chemistry on wettability, evaporation rate and the Leidenfrost temperature are experimentally investigated. The functional surfaces with two alternative patterns were originally fabricated via direct femtosecond laser surface processing of polished silicon wafer in air at a fluence slightly above ablation threshold. The droplet lifetime method was used to measure the evaporation rate of a water droplet (4.5 μL) at surface temperatures of 25–350°C and to determine the Leidenfrost temperature. Generally, after processing the functional surfaces with hierarchical surface morphology demonstrate enhanced wetting behavior, evaporation rate enhancement and positive shifts in the Leidenfrost temperature. The functional surfaces with a microgrooved surface pattern, extensively covered by flake-like nanostructures, exhibit strong superhydrophilicity, resulted in a significant temperature-dependent enhancement of evaporation rate (up to 6 times) and an increase of about 30°C in the Leidenfrost temperature relative to the polished surface. The functional surfaces with a microcratered surface pattern being only hydrophilic demonstrate a nearly twofold temperature-independent enhancement of evaporation rate. Thermostability tests showed the heating of the functional surfaces above 340°C to be resulted in a drastically deteriorated wettability and a reduction of evaporative heat transfer performance under repeated experiments.

GHI calculation sensitivity on microphysics, land- and cumulus parameterization in WRF over the Reunion Island

The sensitivity of different microphysics and dynamics schemes on calculated global horizontal irradiation (GHI) values in the Weather Research Forecasting (WRF) model is studied. 13 sensitivity simulations were performed for which the microphysics, cumulus parameterization schemes and land surface models were changed. Firstly we evaluated the model's performance by comparing calculated GHI values for the Base Case with observations for the Reunion Island for 2014. In general, the model calculates the largest bias during the austral summer. This indicates that the model is less accurate in timing the formation and dissipation of clouds during the summer, when higher water vapor quantities are present in the atmosphere than during the austral winter. Secondly, the model sensitivity on changing the microphysics, cumulus parameterization and land surface models on calculated GHI values is evaluated. The sensitivity simulations showed that changing the microphysics from the Thompson scheme (or Single-Moment 6-class scheme) to the Morrison double-moment scheme, the relative bias improves from ~45% to ~10%. The underlying reason for this improvement is that the Morrison double-moment scheme predicts the mass and number concentrations of five hydrometeors, which help to improve the calculation of the densities, size and lifetime of the cloud droplets. While the single moment schemes only predicts the mass for less hydrometeors. Changing the cumulus parameterization schemes and land surface models does not have a large impact on GHI calculations.

Towards a bulk approach to local interactions of hydrometeors

Abstract. The growth of small cloud droplets and ice crystals is dominated by the diffusion of water vapor. Usually, Maxwell's approach to growth for isolated particles is used in describing this process. However, recent investigations show that local interactions between particles can change diffusion properties of cloud particles. In this study we develop an approach for including these local interactions into a bulk model approach. For this purpose, a simplified framework of local interaction is proposed and governing equations are derived from this setup. The new model is tested against direct simulations and incorporated into a parcel model framework. Using the parcel model, possible implications of the new model approach for clouds are investigated. The results indicate that for specific scenarios the lifetime of cloud droplets in subsaturated air may be longer (e.g., for an initially water supersaturated air parcel within a downdraft). These effects might have an impact on mixed-phase clouds, for example in terms of riming efficiencies.

The use of a fast pyrolysis oil – Ethanol blend in diesel engines for chp applications

The use of Fast Pyrolysis Bio-Oil (FPBO) in diesel engines can be a valuable approach for CHP applications. However, the properties of FPBO make this application very challenging. The purpose of this work is to develop and demonstrate the use of FPBO in modified engines.Proper atomization of the fuel is of utmost importance and a. o. influenced by the fuel surface tension. The final equilibrium value of the surface tension is only slightly higher than for diesel, but large deviations in surface tension are observed at the short droplet lifetimes occurring in an engine's cylinder. Addition of 10–20 mass% of ethanol to the FPBO can significantly improve the atomization properties.Two diesel engines are available at BTG, a one-cylinder (1C) and a four-cylinder (4C). Both engines have been modified and operated on FPBO. Additional safety measures have been implemented for the 1C-unit to enable unattended operation. So far, the longest continuous and stable run has been 52 h. In total, this 1C engine has been operated for nearly 400 h on FPBO or FPBO blends.More recently, the four cylinder, 48 kW diesel engine has been modified to enable fueling with FPBO. This engine can be seen as a prototype for a commercial CHP unit (100 kW–1 MW electrical output). The unit was successfully commissioned and initial tests are in line with the 1C experiments. Due to a lower calorific value, the volumetric fuel consumption is significantly higher in case of FPBO. However, the overall electrical efficiency is very similar to diesel.

Evaporation of water droplets with metallic inclusions

The dynamics of non-axisymmetric evaporating droplet with metallic inclusions heated in a high-temperature gas flow are experimentally studied. The type of metallic inclusion is found to play a critical role in the transient flow dynamics and associated heat transfer. Experiments were conducted with eight metals and alloys currently used in industrial applications. High-speed recording (up to 102–104 frames per second) allowed measuring lifetimes of water droplets with different metallic inclusions (1 mm or 2 mm in size) when increasing the gas temperature from ∼300 K up to about 900 K. We propose a candidate mechanism of evaporation that explains the differences between measured droplet lifetimes in the performed tests. Furthermore, the conditions to provide the most effective cooling are determined. They are based on the balance equations taking into account warm-up times of inclusions and the ratio between the latent heat of vaporization of water, the energy used to heat up water and the metallic particles.

Unsteady temperature fields of evaporating water droplets exposed to conductive, convective and radiative heating

In this paper, we present the rates and typical durations of high-temperature heating and evaporation of water droplets determined for the dominating conductive, convective or radiative energy supply. We developed three setups for heating a water droplet: on a substrate (conduction), in a muffle furnace (radiation), and in a heated airflow (convection). The heating temperature is up to 1000 °C to correspond high-temperature technologies, namely thermal cleaning of fluids, polydisperse fire extinguishing with low water consumption, etc. With the help using of a high-speed video recording system, we determine the water droplet lifetimes (the times of their complete evaporation). Using Planar Laser Induced Fluorescence, we establish the quantitative differences between the water droplet heating rates (heating time to lifetime ratios) on the three setups. Maximum temperatures are determined that the water droplets reach when exposed to different heating mechanisms. Furthermore, we obtain the criterial dependences to connect the main attributes of temperature field generation of an evaporating water droplet with the heating conditions. Finally, we identify possible implications of the research findings and ways to further improve the newly developed experimental approach.

A Numerical Study of Ethanol–Water Droplet Evaporation

The present effort focuses on detailed numerical modeling of the evaporation of an ethanol–water droplet. The model intends to capture all relevant details of the process: it includes species and heat transport in the liquid and gas phases, and detailed thermophysical and transport properties, varying with both temperature and composition. Special attention is reserved to the composition range near and below the ethanol/water azeotrope point at ambient pressure. For this case, a significant fraction of the droplet lifetime exhibits evaporation dynamics similar to those of a pure droplet. The results are analyzed, and model simplifications are examined. In particular, the assumptions of constant liquid properties, homogeneous liquid phase composition and no differential volatility may not be valid depending on the initial droplet temperature.

Experimental investigations on nucleation, bubble growth, and micro-explosion characteristics during the combustion of ethanol/Jet A-1 fuel droplets

The combustion characteristics of ethanol/Jet A-1 fuel droplets having three different proportions of ethanol (10%, 30%, and 50% by vol.) are investigated in the present study. The large volatility differential between ethanol and Jet A-1 and the nominal immiscibility of the fuels seem to result in combustion characteristics that are rather different from our previous work on butanol/Jet A-1 droplets (miscible blends). Abrupt explosion was facilitated in fuel droplets comprising lower proportions of ethanol (10%), possibly due to insufficient nucleation sites inside the droplet and the partially unmixed fuel mixture. For the fuel droplets containing higher proportions of ethanol (30% and 50%), micro-explosion occurred through homogeneous nucleation, leading to the ejection of secondary droplets and subsequent significant reduction in the overall droplet lifetime. The rate of bubble growth is nearly similar in all the blends of ethanol; however, the evolution of ethanol vapor bubble is significantly faster than that of a vapor bubble in the blends of butanol. The probability of disruptive behavior is considerably higher in ethanol/Jet A-1 blends than that of butanol/Jet A-1 blends. The Sauter mean diameter of the secondary droplets produced from micro-explosion is larger for blends with a higher proportion of ethanol. Both abrupt explosion and micro-explosion create a large-scale distortion of the flame, which surrounds the parent droplet. The secondary droplets generated from abrupt explosion undergo rapid evaporation whereas the secondary droplets from micro-explosion carry their individual flame and evaporate slowly. The growth of vapor bubble was also witnessed in the secondary droplets, which leads to the further breakup of the droplet (puffing/micro-explosion).

Planar laser-induced fluorescence diagnostics of water droplets heating and evaporation at high-temperature

Gas-steam-droplet technologies are widely used in systems operating at high temperatures ranging between 400 and 2000°C, namely: fire-fighting systems, thermal fluid cleaning, fuel compounding, industrial waste gasification and evaporation systems for advanced fuel components, cleaning of thermally loaded surfaces of power equipment, etc. System parameters are usually selected empirically via multiple tests and continuous trial operation of appropriate units, aggregates, assemblies, and installations. This situation is caused by insufficient basic knowledge of conditions and parameters of high-temperature (over 500°C) heating and evaporation of water and water-based emulsions, solutions, and slurries. Limited information is available regarding the evaporation rates dependent on the temperature of gaseous medium. Consequently, the up-to-date evaporation models allow the researchers to achieve adequate values (in good agreement with the experiment) of evaporation rates at air temperatures not exceeding 300–400°C. The paper presents a set of experiments on water droplets with the size ranging from 1 to 2mm, which is used to create the information database on high-temperature evaporation parameters. The approach to measuring the evaporation rate involves observation of the droplet size or more exactly its mean radius, and recording the time of its existence. A high-speed video camera and Tema Automotive software with different tracking algorithms are used for experimental observations. During gas heating, the distribution of highly non-homogeneous and non-steady temperature field in evaporating water droplets is detected by the hardware and software cross-correlation system and Planar Laser-induced Fluorescence optical diagnostics. Instantaneous and medium evaporation rates are computed for the whole period of the droplet lifetime. Highly nonlinear evaporation rate dependences are suggested for gas temperatures and the water droplet surface, size, and time of gas heating. Approximate relationships are described for the prediction of evaporation rates depending on the basic parameters. The evaporation rate is shown to increase several-fold during the heating of a water droplet in a high-temperature gaseous medium. The experimental data are described most accurately by exponential dependences of water evaporation rate versus the airflow temperature and velocity. This result makes it possible to predict the corresponding highly nonlinear dependences of evaporation rate versus the density of convective heat flux and the overall thermal conditions in the industrial chambers, evaporators, heat exchangers, etc. The mathematical expressions obtained can be used to identify the effective conditions of water droplet heating in a large group of high-temperatures applications as well as for developing high-temperature liquid evaporation models.

Experimental study on the evaporation of sessile droplets excited by vertical and horizontal ultrasonic vibration

Interaction between sessile droplets and solid surfaces is a fundamental science and engineering problem, with ubiquitous presence in various applications. In this paper, we study the effect of imposing vertical and horizontal ultrasonic vibration (40kHz) on dynamics (oscillations) and evaporation of sessile droplets of dimethylformamide (DMF), isopropyl alcohol (IPA) and water on Teflon and glass substrates. There is no or very few works considering dynamics and evaporation aspects of excited droplets, simultaneously. The theory concerning the force balance and pinning/depinning in pristine and excited sessile droplet systems is elucidated. Time varying left and right contact angles and contact radius are measured for the duration of the droplet lifetime, where the stick-slip phenomena are observed and interpreted for various liquids. Imposing substrate vibration results in significant decrease in droplet lifetime and affects the behavior of the stick-slip mechanism. Droplets excited by horizontal vibration have the shortest lifetime. It is also experimentally shown that in the case of vertical vibration, the left and right contact angles oscillate in-phase, whereas in the case of horizontal vibration, there is 180° phase difference between left and right contact angles.

Combustion dynamics of low vapour pressure nanofuel droplets

Multiscale combustion dynamics, shape oscillations, secondary atomization, and precipitate formation have been elucidated for low vapour pressure nanofuel [n-dodecane seeded with alumina nanoparticles (NPs)] droplets. Dilute nanoparticle loading rates (0.1%–1%) have been considered. Contrary to our previous studies of ethanol-water blend (high vapour pressure fuel), pure dodecane droplets do not exhibit internal boiling after ignition. However, variation in surface tension due to temperature causes shape deformations for pure dodecane droplets. In the case of nanofuels, intense heat release from the enveloping flame leads to the formation of micron-size aggregates (of alumina NPS) which serve as nucleation sites promoting heterogeneous boiling. Three boiling regimes (A, B, and C) have been identified with varying bubble dynamics. We have deciphered key mechanisms responsible for the growth, transport, and rupture of the bubbles. Bubble rupture causes ejections of liquid droplets termed as secondary atomization. Ejection of small bubbles (mode 1) resembles the classical vapour bubble collapse mechanism near a flat free surface. However, large bubbles induce severe shape deformations as well as bulk oscillations. Rupture of large bubbles results in high speed liquid jet formation which undergoes Rayleigh-Plateau tip break-up. Both modes contribute towards direct fuel transfer from the droplet surface to flame envelope bypassing diffusion limitations. Combustion lifetime of nanofuel droplets consequently has two stages: stage I (where bubble dynamics are dominant) and stage II (formation of gelatinous mass due to continuous fuel depletion; NP agglomeration). In the present work, variation of flame dynamics and spatio-temporal heat release (HR) have been analysed using high speed OH* chemiluminescence imaging. Fluctuations in droplet shape and flame heat release are found to be well correlated. Droplet flame is bifurcated in two zones (I and II). Flame response is manifested in two frequency ranges: (i) buoyant flame flickering and (ii) auxiliary frequencies arising from high intensity secondary ejections due to bubble ruptures. Addition of alumina NPs enhances the heat absorption rate and ensures the rapid transfer of fuel parcels (detached daughter droplets) from droplet surface to flame front through secondary ejections. Therefore, average HR shows an increasing trend with particle loading rate (PLR). The perikinetic agglomeration model is used to explain the formation of gelatinous sheath during the last phase of droplet burning. Gelatinous mass formed results in bubble entrapment. SEM images of combustion precipitates show entrapped bubble cavities along with surface and sub-surface blowholes. Morphology of combustion precipitate shows a strong variation with PLRs. We have established the coupling mechanisms among heat release, shape oscillations, and secondary atomizations that underline the combustion behaviour of such low vapour pressure nanofuels.

Puffing and Micro-Explosion Behavior in Combustion of Butanol/Jet A-1 and Acetone-Butanol-Ethanol (A-B-E)/Jet A-1 Fuel Droplets

ABSTRACTButanol is mainly produced by acetone–butanol–ethanol (A-B-E) fermentation. The higher costs associated with the separation of butanol from the A-B-E mixture has prohibited the large-scale production of butanol. The direct use of the intermediate product (A-B-E mixture) could be an economical pathway if utilized for clean combustion. The present investigation deals with the puffing and micro-explosion characteristics in the combustion of a single droplet comprising butanol/Jet A-1, A-B-E/Jet A-1 blends, and A-B-E. The complete sequence of processes leading to micro-explosion, i.e., onset of nucleation, growth of vapor bubble, and subsequent breakup of droplet, for various fuel blends has been analyzed from the high-speed images. It is witnessed that puffing plays a crucial role in enhancing the micro-explosion especially in droplets with 50/50 composition. The probability of micro-explosion in droplets with A-B-E blends was found to be higher than that of butanol blends. Although the rate of bubble growth was almost similar for all butanol and A-B-E blends, the final bubble diameter before the droplet breakup was found to be higher for 50/50 blends than that of 30/70 blends. The occurrence of micro-explosion shortened the droplet lifetime, and this effect appeared to be stronger for droplets with 50/50 composition. Micro-explosion led to the ejection of both larger and smaller secondary droplets; however, puffing resulted in relatively smaller secondary droplets. Bubble growth and subsequent puffing/micro-explosion were also observed in the secondary droplets, which might play an important role in enhancing the atomization and, hence, combustion.

Impact of droplet evaporation rate on resulting in vitro performance parameters of pressurized metered dose inhalers

Pressurized metered dose inhalers (pMDIs) are widely used for the treatment of pulmonary diseases. The overall efficiency of pMDI drug delivery may be defined by in vitro parameters such as the amount of drug that deposits on the model throat and the proportion of the emitted dose that has particles that are sufficiently small to deposit in the lung (i.e., fine particle fraction, FPF). The study presented examines product performance of ten solution pMDI formulations containing a variety of cosolvents with diverse chemical characteristics by cascade impaction with three inlets (USP induction port, Alberta Idealized Throat, and a large volume chamber). Through the data generated in support of this study, it was demonstrated that throat deposition, cascade impactor deposition, FPF, and mass median aerodynamic diameter of solution pMDIs depend on the concentration and vapor pressure of the cosolvent, and the selection of model throat. Theoretical droplet lifetimes were calculated for each formulation using a discrete two-stage evaporation process model and it was determined that the droplet lifetime is highly correlated to throat deposition and FPF indicating that evaporation kinetics significantly influences pMDI drug delivery.