Inlet Operating Conditions Research Articles

Numerical evaluation of passive autocatalytic recombiner performance under post-accident conditions

In the accident conditions, the operational behavior of passive autocatalytic recombiners (PARs) has garnered significant attention, particularly with regards to the complicated atmosphere in the containment. This paper aims to systematically study and analyze the PAR performance under post-accident conditions. CFD simulation resolving individual catalytic channels of PARs provide valuable insights into hydrogen consumption performance and temperature distribution. A simplified model of PARs, consisting of a gas channel and two catalyst plates, was developed using the CFD software STAR-CCM+. One-step reaction mechanism was used in this model to define the hydrogen consumption rate on the catalytic surface. To study the variation in gas concentration and temperature distribution, physical values of interest were extracted from designated locations. An analysis of catalyst section was conducted to provide a comprehensive understanding of the reaction process occurring within PARs. Subsequent tests were conducted using the developed simplified model to examine the effect of inlet gas components variation and operating conditions on PAR performance under post-accident conditions. Our findings show that the variation of steam concentration primarily alters the heat absorption capacity of the gas mixture, rather than the catalytic reaction rate. Furthermore, inlet velocity and operating pressure play a role in controlling the inlet mass flow rate, thereby influencing the reaction process of the gas channel by introducing varying amounts of hydrogen.

EFFECT OF NON-AXISYMMETRIC INLET PORTS AND OPERATING CONDITIONS ON DROP DYNAMICS OF AN INTERNAL MIXING ATOMIZER

The effect of a non-axisymmetric inlet ports configuration of an internal-mixing twin-fluid atomizer on the spray characteristics is experimentally investigated. Inside the atomizer, two water jets are impinged on each other and are further disrupted by a central gas stream coming from the top. The operating conditions consider the variation of the gas mass flow rate at Reynolds and Weber numbers in the order of 10<sup>4</sup>-10<sup>5</sup>. Phase Doppler anemometry (PDA) measurements at four radial, four axial, and two perpendicular azimuthal positions are combined with a patternator device to obtain droplet size, axial velocity, and mass flux distributions. An approach for evaluating the overall spray asymmetry based on the mass flux distributions is proposed, which enabled the detection of slight asymmetries throughout the azimuthal direction, where especially differences in droplet sizes and velocities measured between the two azimuthal positions are observed. Higher Sauter mean diameters (SMDs) and lower velocities in regions of the spray with higher liquid mass flux are observed when compared to the azimuthal position perpendicular to it. In general, the liquid is considerably faster in the spray center than at the boundaries, where the fluctuating component of the velocity is higher due to the interaction of small droplets with the surrounding air. Overall, an increase in the gas flow rate reduces the droplet sizes and increases the velocity across the spray.

Numerical study on inlet operational conditions in the outside vapor deposition process

Operational conditions at inlets of outside vapor deposition (OVD) play an important role in production yields and quality of optical fiber preforms. This work aims to numerically investigate the inner states and SiO 2 deposition performance of OVD under different inlet operational conditions. This is based on a recently developed Eulerian-Eulerian multiphase OVD process model which is extended to consider the SiO 2 particle nucleation and growth. The effects of inlet operational conditions are investigated in terms of the flow rate of SiCl 4 /O 2 -H 2 -O 2 , the mass fraction ratio of SiCl 4 /O 2 as well as different carrier gases (H 2 , N 2 or O 2 ). The simulations show that there exists an optimal SiCl 4 /O 2 flow rate to yield the maximum deposition efficiency. While the deposition efficiency decreases with increasing either O 2 or H 2 flow rate. The reduction of the mass fraction ratio of SiCl 4 /O 2 leads to a dramatic decline in deposition efficiency, whereas the averaged particle diameter of SiO 2 on the target is insensitive to the variations of the SiCl 4 /O 2 mass fraction ratio. In addition, using H 2 or N 2 as carrier gas instead of O 2 leads to a nonuniform SiO 2 distribution and a significant decline in SiO 2 particle sizes on the target. The results reveal that selecting inlet operational conditions is an effective tool to adjust deposition efficiency and control the quality of SiO 2 particles on the target. • Effects of inlet conditions on OVD inner states and SiO 2 deposition are studied. • This work is done by further developing an Eulerian-Eulerian OVD process model. • The SiO 2 nucleation and growth are considered to describe the particle behavior. • Results are analyzed in terms of multiphase flow and thermochemical behavior.

Flow Characteristics of a Mixed Compression Hypersonic Intake

The flow field in a two-dimensional hypersonic mixed-compression inlet in a freestream Mach numbers of M∞ =2.0, 3.0, and 5.0 are numerically solved to understand the effect of throat area variation. The exit area ratio variation is simulated by placing a plug insert at different axial locations at the exit of the model. The flow field is achieved computationally by solving the Reynolds Averaged Navier-Stokes equations in a finite volume framework. For each flow condition, the variation in shock structure is analyzed and the variation of the oblique shock wave angle with the mass flow rate is calculated theoretically and compared with the present CFD analysis. The variation in oblique shock angle is calculated in terms of the mass flow rate by considering the capture area and spillage flow through the inlet. The theoretical results suggest that the method can predict the inlet operating conditions at different freestream Mach numbers and area ratios. This method can quantify the reduction in mass flow rate due to the throttling effect by analyzing the flow field shock pattern. The effects of various important performance parameters such as free stream Mach number, total pressure recovery, and mass flow ratio were then numerically investigated. As the Mach number is increased, the total pressure recovery is reduced, but the maximum value of the mass flow rate is increased. The analysis is also focused on the effect of throat area variation on performance parameters at each Mach number. The characteristic curve of the inlet is then obtained for each free stream Mach number.

Performance evaluation of a rotary dryer in both co-current and counter-current configurations

A mathematical model was developed to simulate the process of superphosphates fertilizers drying in a rotary dryer in both co-current and counter-current configurations. Besides, the performance of the rotary dryer, installed in a local industrial unit, was assessed using the concept of energy and exergy analysis. Matlab software was used to develop the mathematical model, which is based mainly on mass and energy conservation equations. Good agreement between the simulated results and the experimental results from literature was obtained. The simulation results showed that the product’s moisture content was reduced from an initial value of 0,14 kgH2O / kg dry solid to 0.0912 and 0.0862 kgH2O / kg dry solid at the dryer's outlet for the co-current and the counter-current configurations, respectively. A parametric study was carried out to evaluate the effect of the length of the dryer and the inlet drying air temperature on the moisture content to compare both configurations. Energetic and exergetic indicators were formulated and then computed based on the inlet operating conditions. The energy efficiency and the specific energy consumption for the co-current and the counter-current configurations were, respectively, found to be 13% and 24% and 5762 and 3502 kJ per kg of water evaporated. The exergy indicators, namely the exergy loss, the exergy destruction rate, and the exergetic efficiency, were 11.37 and 17.82 kW, 1.026 and 1.098 kW, 25.86 and 41.38% for the co-current and the counter-current configuration, respectively. A sensitivity analysis was used to investigate the effect of varying the inlet drying air temperature on energetic and exergetic performance parameters.

Effects of loss of heat sink transient on flow characteristics in a closed natural circulation system

Flow characteristics during loss of coolant to the heat exchanger (HX) via the secondary loop cold leg of a natural circulation (NC) test facility referred here as loss of heat sink transient (LOHS) in a closed rectangular NC system having a single heated channel at two different heating powers and system pressures has been investigated experimentally. Two LOHS experiments (LOHS-1 and LOHS-2) were conducted in a well dimensioned closed loop NC test facility designed to represent the primary system of a nuclear reactor. Operating conditions were set and maintained at 6.0 kW and 9.0 kW with system pressures of 0.2 MPa and 0.5 MPa respectively for both single-phase and single-to-two-phase flow transition to determine their thermal hydraulic responses at these predetermined parameters. The transients were initiated by closing the cold leg of the secondary loop supplying coolant to the tube-in-shell heat exchanger while NC flow phenomena were monitored at each vital section along the flow map based on the pre-determined inlet operating conditions. LOHS experiment stops when critical heat flux (CHF) occurs or heat exchanger outlet (HXoutlet) temperature rises too high to approximately equal its inlet temperature. Results were acquired using a system-design platform and development environment LabVIEW, programmed in a dedicated computer that was interfaced with the coupled sensors in the measuring devices. Common computational tools which include MATLAB, Ms Excel and Origin software were used for the analysis of the acquired data. Results at the inlet and outlet of heated sections as well as the inlet and outlet of condensers of both tests were analyzed and discussed in details at various flow regimes with the associated phenomena. It is concluded that while stable flow was maintained before transient with slug flow occurring in the heating channel, the system experienced transient stability resulting in steady temperature increase and subsequently drops into an instability region when the transient scenario was activated. In addition, the NC system transited into stable two-phase flow and further loses stability when HXoutlet temperature surges to its inlet value with CHF occurrence. These results are presented to contribute to a more extensive utilization of NC systems and understanding of flow behavior during LOHS in advanced reactors.

Flow conditioning system for tri-sonic high pressure aerothermal testing

Blowdown testing offers a cost-effective experimental tool to replicate the aerothermal conditions in numerous high speed systems. The wind tunnel must replicate the inlet operating conditions, while the spatial and time dependent inlet flow conditions should be assessed carefully. This paper provides a design methodology and rules that ensure adequate flow conditioning in high inlet pressure wind tunnels suitable for subsonic and supersonic operation with mass-flow limits ranging from 1 kg/s to 25 kg/s, Reynolds numbers from 103 (1/m) to 4x107 (1/m), and Mach numbers from 0.01 up to 6. The quality of the proposed flow conditioning system was evaluated using stereo PIV measurements combined with hotwire, Pitot probe, and total flow temperature traverses.

Validation of the Molar Flow Rates of Oil and Gas in Three-Phase Separators Using Aspen Hysys

A three-phase separator is the first vessel encountered by well fluids. The application of separators has been of great value to the oil and gas industry. In order to generate the gas phase envelope that is applicable to the study of reservoir fluid and the selection of optimum operating conditions of separators, this research utilizes a specified reservoir fluid stream to simulate a three-phase separator executed in Aspen HYSYS. Subsequently, a comparative study of the effects of specified inlet operating conditions on the output of gas and oil streams was carried out. The results show that changing the inlet pressure of the separator from 1000 to 8000 kPa reduces the gas outlet flow from 1213 to 908.6 kg mol/h, while it increases the liquid flow rate from 374 to 838.0 kg mole/h. By changing the temperature of the separator feed stream from 13 to 83 °C, the gas outlet stream was raised from 707.4 to 1111 kg mol/h, while the liquid flow rate dropped from 1037.0 to 646.1 kg mol/h. It was observed that the concentration of the outlet methane product is not affected by changing the flow rate of the feed stream at a specific pressure and temperature. Therefore, the thermodynamic property method is appropriate to simulate the separation of reservoir fluids which was achieved by selecting the Peng–Robinson (PR) model. The operating conditions of the separator were at 8000 kPa and 43 °C, which lies right on the dew point line. This is comparable to similar work on CHEMCAD which was in turn validated by plant data. Thus, the gas flow rate and the oil flow rate were dependent on pressure and temperature conditions of the plant.

CFD NUMERICAL AND EXPERIMENTAL INVESTIGATION OF TWO-PHASE FLOW DEVELOPMENT AFTER AN EXPANSION DEVICE IN A HORIZONTAL PIPE

To optimize a vertical flash tank separator, the characteristics of the flow entering the separator are required to be known. A flash tank separator improves the performance of a refrigeration cycle by separating the liquid from liquid-gas flow and providing the evaporator with only liquid refrigerant. This technique improves the effective area and enhances the heat transfer coefficient in the evaporator. This paper investigates the influence of the inlet operating conditions to an expansion device, on the adiabatic two-phase flow development in a horizontal pipe downstream from the expansion device. This work also compares three dimensional numerical simulations and experimental observations for the two-phase flow development after the expansion device in the horizontal pipe. A general trend of the two-phase flow after the expansion device was gradually developed and the expansion length was identified at less than 200 mm from the inlet. The two-phase flow behaviour was recorded using a digital camera recording the flow behaviour at the upstream and downstream of the horizontal tube. The results revealed that an increase of the mass flow rate causes an increase in the void fraction and a reduction in the slip ratio in the developed region. The simulations underestimate the expansion length and the mean difference between the experimental data and the numerical results is 8 %.

Influence of design anode and cathode channel on (PEMFC) fuel cell performance

Abstract This paper is focussed on investigating into some key aspects relating to design of an integrated proton exchange membrane fuel cell. Analysis of all currently utilised storage mediums was undertaken. High and low inlet operating conditions were studied by determining the distributions of over potentials, velocity distribution, and pressure. At entrance and exit, a triangle channel flow-field was predicted to have better polarization performance and regular velocity distribution, whereas for rectangular that was performance differences among four serpentine flow-fields for hydrogen and air. The pressure in the triangle channels were monitored to have periodically similar plots and showed important low pressure drop. Considering low pressure drop of rectangular channel has mid effect between triangles and rectangular for the same dimension that depends on the hydraulic diameter, these flow-fields would be beneficial for the larger inlet channel area. The study found that the triangular channels produced a better performance than their square flow path counterparts.

Flow Asymmetry in a Y-Shaped Diverterless Supersonic Inlet: A Novel Finding

Extensive wind-tunnel tests were performed on a Y-shaped diverterless supersonic inlet (DSI). All tests were conducted at a free stream Mach number of , the design Mach number for this inlet, and at both zero degrees angle of attack (AOA) and angle of sideslip (AOS). The experiments were performed at various inlet operating conditions comprising supercritical, critical, and subcritical conditions that covered almost all ranges of the engine operating for this DSI. The results showed that the DSI had relatively acceptable performance characteristics when operating at its design condition. A symmetric supersonic flow pattern was observed at both supercritical and critical operating conditions of the present Y-shaped DSI. However, both symmetric and asymmetric supersonic flow patterns were observed during the subcritical operating conditions of the present inlet. At low subcritical operating conditions, the supersonic flow pattern remained symmetric, similar to that of the critical operating condition case. As the inlet experienced higher subcritical operating conditions, the supersonic flow structures became suddenly asymmetric and a new flow pattern was noticed. This flow pattern was seen to be highly unstable; and significant asymmetric shock wave oscillations, boundary-layer thickening, and shock-/boundary-layer interaction were observed for these situations. To the authors’ knowledge, this novel phenomenon of asymmetric flow behavior in a perfectly manufactured symmetric Y-shaped DSI encountering symmetric flow (0 deg AOA and AOS) has not been noticed by previous researchers and, if so, the results have not been published yet.

Effects of Slitting Size and Inlet Operating Conditions on Hydrogen Combustion Characteristics in a Micro-Combustor With a Controllable Vortex Slotted Bluff Body

Abstract Effects of controllable vortex slotted bluff body parameters (position of a bluff body, slit size, and controllable flow ratio) on the combustion characteristics of hydrogen/air in a micro-combustor with a bluff body were investigated numerically. The results illustrated that the combustion efficiency of hydrogen decreases with increasing distance (L1) between the front edge of the bluff body and the combustor inlet. The combustion characteristics of the micro-combustor are optimum when L1 is 0 mm. The blow-off limit of the combustor reaches a maximum (564 cm3/s) when the slit width (d) is 20% of the bluff body width. The blow-off limit first increases and then decreases when the equivalence ratio (φ) increases and reaches a maximum (732 cm3/s) when φ is 1.0, and the controllable flow ratio is 0.2. The combustion efficiency of hydrogen is gradually increased with the increase in the controllable flow ratio. When φ is less than 1.0, the optimal controllable flow ratio gradually decreases with the increase in the premixed gas flow rate, and the optimal controllable flow ratio basically remains at 0.6 when the premixed gas flow rate is less than 360 cm3/s.

Performance of desiccant heat exchangers with aluminum foam coated or packed with silica gel

Performance of two types of desiccant silica gel aluminum foam heat exchangers - desiccant coated heat exchanger (DCHE) and desiccant packed heat exchanger (DPHE) are evaluated experimentally and numerically. The DCHE is fabricated by coating silica gel over the ligaments of an aluminum foam, while the DPHE is built by packing an aluminum foam with silica particles. Equilibrium isotherms of the two heat exchangers are measured using the gravimetric approach. An open flow loop test rig is designed and built to measure the dry bulb temperature and humidity ratio of air upstream and downstream of the desiccant heat exchangers during the humidification and dehumidification process. In addition, a mathematical model is developed to investigate the heat and mass transfer process in the two desiccant heat exchangers. The experimental data obtained are used to validate the numerical results, and good agreement is established. The effects of heat exchanger length and inlet operating conditions on the performance of DPHE and DCHE are investigated. Experimental and numerical results indicate that the DPHE outperforms the DCHE in terms of cooling capacity and moisture removal capacity. It is observed that the performance of the DPHE is close to that of the DCHE in handling sensible heat loads but exceeds the latter in removing latent heat loads. The DPHE can provide dehumidified air for a longer time due to its higher moisture removal ability and higher density of the desiccant material compared to the DCHE.

Determination of distribution factors for heavy n-alkanes (nC12-nC98) in high temperature gas chromatography

The ultimate purpose of this research work is to get an insight into the incomplete elution of heavy n-alkanes which along with thermal cracking, is one of the two main factors questioning the reliability of High Temperature Gas Chromatography (HTGC) analysis of heavy oils. For this purpose, knowledge of how the Distribution Factors vary with temperature is an essential requirement in the GC modelling.This study provides an extension of the data set of distribution factors for n-alkanes up to nC98H198 in a HT5 GC column over the temperature range 10 °C–430 °C, and introduces a method to determine the distribution coefficient of heavy n-alkanes by using two complimentary HTGC modes: i.) High-Efficiency mode, for efficient resolution with a long column operated at low flow rate with n-alkanes elution rate up to nC64, and ii.) true SimDist mode, with a short column operated at high flow rate for inefficient resolution with n-alkanes elution rate up to nC100.Furthermore, this study demonstrates the use of the in-house obtained distribution factors as the main input in the in-house GC model for the prediction of the retention times. Its validation has been carried out using distribution factors obtained at both constant flow rate and constant inlet pressure operating conditions, with an average relative error in the GC modelling at the same operating conditions of 4.4% for the former and 1.5% for the latter.This new extension of the data set of heavy n-alkanes distribution factors provides the basis for studying the partitioning and incomplete elution of heavy n-alkanes in HTGC analysis. Also, these new distribution factors can be used as input in GC modelling, to determine the optimum analytical conditions to improve the separation process and thus the HTGC practices.

Modeling of two-phase transcritical CO2 ejectors for on-design and off-design conditions

CO2 two-phase ejectors are used as expansion work recovery components in refrigeration or heat pump systems. A new thermodynamic model is developed for both single choking and double choking conditions to design such ejectors and investigate their performances. This model, based on the homogeneous equilibrium model (HEM), solves the conservation equations using real fluid properties rather than ideal gas assumptions. The irreversibilities due to friction in the nozzles and the diffuser are accounted for by polytropic efficiencies. The performance of a two-phase ejector is predicted for a fixed ejector geometry and given inlet operating specifications at off-design conditions. The model can also evaluate the ejector dimensions for given inlet and outlet operating conditions (on-design). The results are compared and validated against published experimental data. The effects of the irreversibilities on the ejector dimensions are investigated in detail.

Thermodynamic Modelling of Supersonic Gas Ejector with Droplets

This study presents a thermodynamic model for determining the entrainment ratio and double choke limiting pressure of supersonic ejectors within the context of heat driven refrigeration cycles, with and without droplet injection, at the constant area section of the device. Input data include the inlet operating conditions and key geometry parameters (primary throat, mixing section and diffuser outlet diameter), whereas output information includes the ejector entrainment ratio, maximum double choke compression ratio, ejector efficiency, exergy efficiency and exergy destruction index. In single-phase operation, the ejector entrainment ratio and double choke limiting pressure are determined with a mean accuracy of 18 % and 2.5 % , respectively. In two-phase operation, the choked mass flow rate across convergent-divergent nozzles is estimated with a deviation of 10 % . An analysis on the effect of droplet injection confirms the hypothesis that droplet injection reduces by 8 % the pressure and Mach number jumps associated with shock waves occuring at the end of the constant area section. Nonetheless, other factors such as the mixing of the droplets with the main flow are introduced, resulting in an overall reduction by 11 % of the ejector efficiency and by 15 % of the exergy efficiency.

Unsteady simulation of quasi-periodic flows in Organic Rankine Cycle cascades using a Harmonic Balance method

Currently, turbomachinery design optimization methodologies are mainly restricted to steady state approaches, due to the high computational cost associated with time-accurate shape optimization algorithms. However, the possibility to include unsteady effects in turbomachinery optimization can significantly increase the level of accuracy of the design predictions, leading to a more realistic representation of the actual performance and ultimately to a substantial increase in operating efficiency. Unsteady effects are particularly relevant in Organic Rankine Cycle turbines. A trade-off between high-fidelity time-accurate unsteady simulations of the flow solution and computational cost is therefore needed at design level. In this paper, a first application of the harmonic balance method to non-ideal compressible flows is presented. The methodology allows to solve the unsteady flow equations for a set of specified frequencies only, with significant computational time savings. An algorithm is proposed for non uniform time sampling in order to resolve frequencies that do not need to be integral multiple of one fundamental harmonic. This enables the solution of quasi-periodically forced non-linear flow problems, in combination with complex fluid models based on accurate equations of state. The method is applied to the unsteady analysis of a supersonic Organic Rankine Cycle stator with quasi-periodic inlet operating conditions, showing about one order magnitude lower computational cost compared to time-accurate simulations.

Acoustic analysis of two small axial-flow fans in series

The noise signatures of two identical small axial-flow cooling fans installed in series with a flow straightener between them are experimentally measured and analyzed. A technique of noise source component decomposition is used to decompose the raw sound signals into tonal and broadband components, both further attributed to either the upstream or the downstream fan. Two major inlet flow conditions (unobstructed inlet and a distorted inlet flow case by the simplified circuit board) and a range of operating conditions under which the tested fan works are investigated. The tonal and broadband noises radiated by the upstream fan are greatly increased by inlet flow distortion, especially in the low workload region, while the two noise components radiated by downstream fan are hardly affected. The upstream fan and the flow straightener flush mounted between the two fans both play a significant role in keeping the downstream fan free from the influence of inlet flow distortion. Themagnitude relations among all the noise source components under different inlet flow and operating conditions are compared, which would definitely offermuch help in designing a quiet two-stage or even multiple-stage fan and adopting an appropriate method to efficient fan noise control and reduction.

Optimal monolithic configuration for heat integrated ethanol steam reformer

A design concept for optimal design of monolith catalyst is presented through modeling of transport–kinetic interactions in a monolith catalyst. We argue that reactors employing monolithic catalysts should be based on its optimal choice of geometry. In line with that argument, we present a thorough analysis of the geometrical parameters influencing the performance of non-isothermal reactor operation. In this study, an optimal monolith configuration is estimated to be a combination (dh, tw) of (0.9 mm, 0.2 mm) for a compact ethanol reformer to produce hydrogen for portable applications where maximum volumetric reactor activity exists. A three-dimensional modeling framework is developed for the resulting optimal monolithic catalyst design that couples the reforming section with a suitable heat source in a recuperative way. As a result, greater ethanol conversion is obtained from the monolith channels near the periphery of the block. The coupling with combustion could predict the formation of cold and hot spots inside the reactor, their nature being dependent on the flow configuration. Further, the effect of altering the feed inlet operating conditions over the variation of ethanol conversion and temperature inside the reactor is also analyzed. The increase in reforming inlet velocity decreases the outlet conversion and shifts the cold spot, forward and deeper in co-flow configuration. The decreasing inlet feed temperature enhances the transfer of heat, eliminating the cold spot.

Stochastic evaluation of the impact of sewer inlets’ hydraulic capacity on urban pluvial flooding

Sewer inlet structures are vital components of urban drainage systems and their operational conditions can largely affect the overall performance of the system. However, their hydraulic behaviour and the way in which it is affected by clogging is often overlooked in urban drainage models, thus leading to misrepresentation of system performance and, in particular, of flooding occurrence. In the present paper, a novel methodology is proposed to stochastically model stormwater urban drainage systems, taking the impact of sewer inlet operational conditions (e.g. clogging due to debris accumulation) on urban pluvial flooding into account. The proposed methodology comprises three main steps: (i) identification of sewer inlets most prone to clogging based upon a spatial analysis of their proximity to trees and evaluation of sewer inlet locations; (ii) Monte Carlo simulation of the capacity of inlets prone to clogging and subsequent simulation of flooding for each sewer inlet capacity scenario, and (iii) delineation of stochastic flood hazard maps. The proposed methodology was demonstrated using as case study design storms as well as two real storm events observed in the city of Coimbra (Portugal), which reportedly led to flooding in different areas of the catchment. The results show that sewer inlet capacity can indeed have a large impact on the occurrence of urban pluvial flooding and that it is essential to account for variations in sewer inlet capacity in urban drainage models. Overall, the stochastic methodology proposed in this study constitutes a useful tool for dealing with uncertainties in sewer inlet operational conditions and, as compared to more traditional deterministic approaches, it allows a more comprehensive assessment of urban pluvial flood hazard, which in turn enables better-informed flood risk assessment and management decisions.