Pressure Drop Increment Research Articles

Coral‐tentacle‐inspired antifouling membrane spacer: A natural solution for biofouling prevention

AbstractFouling of membrane spacers leads to increased pressure drop and reduced lifespan of membrane modules. Cleaning these fouled spacers is challenging due to strong foulant‐membrane spacer interactions. To address this issue, we introduce a novel spacer, PP‐N‐F, inspired by coral's antifouling properties. This spacer features on‐demand antifouling capabilities through a sequential growth process of functional polymer brushes on its surface. It not only possesses lower surface free energy characteristics than polypropylene spacers, but also exhibits controllable morphological changes similar to swaying coral tentacles. Temperature control strengthens the interfacial hydration layer, mitigating the trade‐off between anti‐adsorption and hydrophobicity of fluorinated surface. The temperature‐responsive surface changes enhance foulant desorption efficiency. Compared to a commercial spacer, PP‐N‐F shows an 89.3% reduction in foulant adsorption and a 61.7% decrease in pressure drop increment after 48 h cross‐flow filtration experiments. This work provides valuable insights for advanced anti‐fouling membrane module design.

Improved flow boiling characteristics in minichannel with open-cell porous ribs

Porous metal has been proven to exhibit significant heat transfer enhancement in minichannel. Focusing on fully utilizing the advantages of porous metal in heat transfer and reducing pressure penalty, a porous ribs minichannel (PRM) heat sink employing open-cell porous copper as rib was designed and fabricated. PRM heat sink has 19 minichannels that are 1 mm in width and 2 mm in depth. Commercial open-cell porous copper with a porosity of 0.85 and 120 PPI (Pore per Inch, PPI) was selected. Flow boiling experiments were carried out with ethanol as the working fluid. The flow patterns of two heat sinks were recorded with a high speed photograph system and comparative analyzed. High-frequency periodic motion of vapor core boundary in width direction of porous ribs minichannel was recorded. This is considered a fluctuation of density wave along the channel width direction. Cooperating with capillary force, movement of vapor core boundary induces mass transfer between adjacent channels, compensating for uneven flow distribution between channels. The results show that PRM heat sink has better heat transfer performances and flow stability with a slight increment in pressure drop compared with solid ribs minichannel (SRM) heat sink. The porous ribs minichannel heat sink provides a new way to relieve flow insatiability for heat exchangers and thermal management systems.

Thermohydraulic performance assessment of new alternative methods for anti-icing application against current application in an aircraft

In this study, anti-icing problems, which are mostly industrial problems in aerospace companies, have been numerically investigated. Herein, to enhance anti-icing performance of NACA0015, different jet-to-surface distances ( H/d), jet angles ( α), and slot jet designs with different aspect ratios ( ARs) have also been investigated. ANSYS Fluent 2020R2 commercial program has been utilized for all numerical calculations. In addition, the SST k-ω with low-Re correction wall treatment turbulence model has been used for solving turbulence equation. Furthermore, the average Nusselt number ( Nu) on the NACA0015's surface, pressure drop, and performance evaluation criteria (PEC) which define the anti-icing performance of novel proposed system have been presented section by section. As a result of the investigation, it has been obtained that the use of AR = 4 increases the Nu by 85.52% compared to circular jet for the H/d = 4 at α = 90°. The pressure drop value dramatically increases using AR = 4 around 307.85% compared to circular jet for H/d = 4 at α = 90°. Despite this drastic increment in pressure drop, the PEC value is kept as 1.14 using AR = 4, H/d = 4, and α = 90°. Finally, empirical correlations developed from existing findings have been presented with an error rate of lower than 5%.

Simulations of Flows via CFD in Microchannels for Characterizing Entrance Region and Developing New Correlations for Hydrodynamic Entrance Length.

Devices with microchannels are relatively new, and many correlations are not yet developed to design them efficiently. In microchannels, the flow regime is primarily laminar, where entrance length may occupy a significant section of the flow channel. Therefore, several computational fluid dynamic simulations were performed in this research to characterize the developing flow regime. The new correlations of entrance length were developed from a vast number of numerical results obtained from these simulations. A three-dimensional laminar flow for 37 Reynolds numbers (0.1, 0.2, …, 1, 2, …, 10, 20, …, 100, 200, …, 1000), primarily in low regime with water flow through six rectangular microchannels (aspect ratio: 1, 0.75, 0.5, 0.25, 0.2, 0.125), has been modeled, conducting 222 simulations to characterize flow developments and ascertain progressive velocity profile shapes. Examination of the fully developed flow condition was considered using traditional criteria such as velocity and incremental pressure drop number. Additionally, a new criterion was presented based on fRe. Numerical results from the present simulations were validated by comparing the fully developed velocity profile, friction factor, and hydrodynamic entrance length for Re > 100 in rectangular channels, for which accurate data are available in the literature. There is a need for hydrodynamic entrance length correlations in a low Reynolds number regime (Re < 100). So, the model was run numerous times to generate a vast amount of numerical data that yielded two new correlations based on the velocity and fRe criteria.

Numerical investigation on effects of fuel rod with different shapes of bow deformation on the subcooled boiling of coolant in a fuel assembly

AbstractThe Eulerian two‐phase boiling model of the subcooled boiling of coolant in a 3 × 3 fuel assembly is established and compared with the experimental data to verify its accuracy. The effects of four shapes of bow deformation on subcooled boiling flow and heat transfer characteristics are obtained by comparing and analyzing the distributions of thermal–hydraulic parameters, including the axial wall superheat, liquid phase temperature, axial void fraction, various heat fluxes, heat transfer coefficient, and turbulent kinetic energy. All shapes of bow deformation will lead to the redistribution of coolant among different subchannels, and the distributions of thermal–hydraulic parameters would be greatly affected. The bow deformation of fuel rod easily causes local boiling, which results in local high temperature of liquid phase and bubble accumulation, and a decrease in the area of high liquid phase heat transfer coefficient on the surface of bowing fuel rod. Additionally, the non‐uniform distribution of turbulent kinetic energy caused by bow deformation in different axial sections not only affects the heat transfer performance of coolant, but also causes the increment in pressure drop, which has negative effects on the safe operation of the nuclear reactor. This paper can provide data and theoretical support for engineering design.

Thermohydraulic performance of a semi-alternated twisted tape insert and cylindrical baffles in a tube with ternary nanofluid under sinusoidal wall temperature

This study numerically evaluates the thermohydraulic performance of a circular tube consisting of semi-alternated twisted tape mounted with cylindrical baffles and ternary nanofluid (SiO2 + ZnO + CaO) as a working fluid. The circular tube wall was exposed to a sinusoidal temperature that axially varied along the wall. The investigation was performed in the laminar flow regime over the Reynolds number 500–2000 and for nanofluid volume fraction 0.01%-0.05%. The semi-alternated twisted tape has pitch ratio 1.77–5.77, width ratio 0.38–0.68 and thickness ratio 0.019–0.033. The performance was analyzed for Nusselt number, pressure drop, thermal performance factor and pumping power. The results indicate, no significant pressure drop increment with volume fraction of the ternary nanofluid. For a fixed volume fraction of 0.01%, width ratio of 0.48 and thickness ratio of 0.019, there is an improvement in Nusselt number by 35–107%, pressure drop increased from 0.26 Pa to 3.5 Pa, pumping power was found to increase by 40%, and thermal performance factor by 1.35–1.67 times that of the smooth tube, when the pitch ratio decreases from 5.77 to 1.77. For a fixed pitch ratio of 1.77 and width ratio 0.38–0.68, the Nusselt number increased by 50–114%, pressure drop increased from 0.207 Pa to 11.1 Pa and thermal performance factor by 1.18–1.76 times as compared with smooth tube. The Nusselt number increased by 100–115% and thermal performance factor increased from 1.08 to 1.16 times the performance of the smooth tube when the thickness ratio was increased from 0.019 to 0.033.

Selection of turbulence promoters for retrofit applications through thermohydraulic performance mapping

Many new heat transfer enhancement devices have been reported in the open literature in the past decades exhibiting innovative geometries and better thermal and hydraulic performance. For a practical application in tubular heat exchangers, the selection of the best inserts out of the many different geometries available can be a cumbersome task. This work shows an approach to reduce the complexity of the search by graphically displaying the relative increase of heat load and pressure drop by means of performance mapping plots. The analysis includes the use of Nusselt and friction correlations and their application at different Reynolds numbers and different fluid viscosities. Out of the different geometries available, a group of 51 are compared in terms of the effect on heat duty and pressure drop. The approach is extended to analyse the exchanger irreversibility. For different operating conditions and fluid types, it is shown that the perforated twisted tape is the best performing insert. This insert produces an increase in heat transfer rate between 4% and 7.3% and an increment in pressure drop between 2 and 3.43 times that of the base case.

Thermo-hydraulic performance of magnetic baffles for cooling using magnetic nanofluid in a mini channel

Thermal and flow performance under influence of magnetic field is studied numerically. A water based Fe3O4 nanofluid (2 %Vol. constant throughout the numerical study) is flowing in a 2-Dimensional channel at low Reynold’s number i.e., Re = 150, 170,190 and 210 and at different magnetic field strength ranging from 1200 G to 2000 G are applied. The heat sink with dimensions of 40 mm X 4 mm consists of magnets placed at two different locations. The magnetic field is acting as a vortex generator which enhance heat transfer for highly concentrated heat fluxes. The heat transfer enhancement due to the magnetic field at x = 15 mm and 25 mm is studied. Results show that there is an increment of 6.13 %, 16.23 % and 37.38 % when magnetic fields of strength 1200 G, 1500 G and 2000 G are applied respectively, at x = 15 mm and the values are increased to 7.12 %, 19 % and 47.64 % for same magnetic fields applied at x = 25 mm. However, this enhancement comes with an increase of pressure drop and back flow. This can be explained due to formation of vortices due to the flow separation caused by the force of magnetic field. Nevertheless, in some cases, there is a net decrease in the pressure drop with increase in heat transfer due to decrease in frictional pressure drop, which dominate the increase in pressure drop due to vortices formation. Results show the decrease in pressure drop by 11.53 %, 17.53 % and 10.05 % when magnetic field of strength 1200 G, 1500 G and 2000 G are applied respectively, at x = 15 mm. Similarly, 8.19 % and 4.78 % pressure drop decrement is shown for 1200 G and 1500 G while an increment of pressure drop by 44.32 % for 2000 G at x = 25 mm.

Numerical simulation on heat transfer enhancement of free piston Stirling engine heater with composite cross section mini channels

Integral fin with micro-channels have been widely used in small free piston Stirling engines heater due to their high heat transfer rate, low flow loss, and high machining accuracy. A β-type free piston Stirling engine heater with composite cross section mini channels(CCSMH) is designed for heat transfer enhancement applying to solar dish power generation system. Investigation on heat transfer performance of the heater under oscillating flow is carried out by CFD method, which is compared with smooth annular tube heater. The influence of geometry parameters on the performance of heat transfer and pressure loss is investigated. A improved performance evaluation criteria PEC is proposed for the condition of equal flow velocity to evaluate the enhanced heat transfer performance of the heater. The results show that the maximum value of the comprehensive performance evaluation index PEC can reach 3.14, the maximum mean pressure drop increment of CCSMH compared with the smooth tube heater is 38.4 Pa, which is much lower than the minimum pressure of 2.3 MPa and can be neglected.

Experimental analysis on the heat transfer performance of gas-liquid Taylor flow in a square microchannel

The flow and heat transfer behaviors of gas–liquid Taylor flow in a 1 × 1 mm square microchannel are experimentally investigated in this paper, focusing on evaluating the slug length, void fraction β, and mixing velocity on the overall performance of Taylor flow in the microchannel. T-shaped junctions of varying widths were employed to control the slug length in the Taylor flow. The experimental results indicate that reducing the junction width can heighten the bubble generation frequency and shorten the bubble/slug length. This reduction in slug length can enhance the heat transfer performance of the Taylor flow in fixed cross-section microchannels, but the degree of enhancement is significantly influenced by the void fraction. When β = 0.5, reducing the slug length can significantly improve the heat transfer coefficient while maintaining a reasonable pressure drop increment, resulting in the best overall performance. The friction pressure drop increases significantly when β = 0.67, and the level of overall performance is low. When β = 0.33, the short slugs have little effect on the performance of Taylor flow, and the change of heat transfer and the friction coefficient is only within 3%. In general, increasing the mixing velocity can improve the overall performance of the Taylor flow. However, at a relatively low void fraction, the pressure drop increase outweighs the heat transfer coefficient, leading to a decline in overall performance. Finally, a correlation is proposed to predict the Nu number under Taylor flow in the three-sided heated rectangular microchannel, with an average error of 11.77%.

The evaluation of the first and second laws of thermodynamics for the pulsating MHD nanofluid flow using CFD and machine learning approach

Background: By developing high-tech instruments, especially digital devices, a need to have efficient and compact cooling is of crucial importance. In the current study, heat transfer enhancement in a microchannel for cooling two hot sources is numerically investigated. Methods: The effects of imposing a magnetic field, a pulsating flow, and using a hybrid nanofluid are tested. Further, the entropy generation is evaluated and the strength of irreversibility sources is discussed. Reynolds number, Hartmann number, nanofluid volume fraction, inlet velocity amplitude, and frequency are chosen as the independent parameters. An artificial neural network is applied to have a prediction tool for the mean Nusselt number and Bejan number. The analysis for choosing the best neuron number for MLP is conducted. The predictive mathematical description is fed to a multi-objective genetic algorithm (NSGA-II) to find the optimum operating conditions of thermal cooling. Significant findings: The results show that Intensifying the inlet amplitude from 0.1 to 0.8 makes the heat transfer and pressure drop increment respectively by 100% and 300%. However, the amplitude increment remains an inverse effect on the Bejan number by a decrement of about 3–4%. The sensitivity analysis shows the first rank of importance belongs to the Reynolds number the Hartmann number shows the least importance in the ranking.

Numerical analysis of heat transfer and flow characteristics of supercritical CO2-cooled wavy mini-channel heat sinks

In today's world, thermal management in the components of new electronic and electromechanical technologies has become one of the most critical challenges in this realm. Generally, there is a high heat flux generating part in these instruments, so a robust heat dissipation or cooling system is required to guarantee their reliability and lifetime. Recently, miniature heat sinks have attracted the attention of many researchers, and the performance of air- and liquid-cooled heat sinks having wavy miniature channels has frequently been investigated. However, the heat transfer and flow characteristics of these cooling systems utilizing critical or pseudocritical carbon dioxide (CO2) as the coolant have not been investigated yet and are still an unclear subject. To fulfill this gap, 3D simulations are carried out to scrutinize the thermal and hydraulic characteristics of CO2 flow inside a wavy mini-channel heat sink at a uniform heat flux of 1000 kW m−2. This study also aims to explore the effects of specific design factors, including wave amplitude (wa) and wavelength (wl), at different inlet temperatures (from 305 to 310 K) and mass fluxes (500–2000 kg m−2 s−1) of the CO2 flow. The simulations start with the validation of the numerical results with the available experimental data, in which the deviations lie within ±2%. The results endorse that replacing the straight mini-channels with the wavy ones can enhance the thermal performance of the heat sink by an average of 1.86 times associated with an average pressure drop increment of 1.58 times. The maximal heat transfer coefficient of 8.58 times is obtained at the lowest inlet temperature of 305 K, whereas the maximal pressure drop of 5.65 times is observed at the highest inlet temperature of 310 K. The results suggest that larger wave amplitudes and smaller wavelengths contribute to the larger heat transfer coefficient values. However, these factors become less influential when the inlet temperature increases. Imposing a lower inlet temperature can significantly improve the overall performance. A maximal performance index of 4.41 is obtained for a model with wa = 1.0 and wl = 5 mm at the inlet temperature of 305 K.

Effect of new design of elongated jet hole on thermal efficiency of solar air heater

Effect of new design of elongated jet hole on the thermal efficiency (ηth) of a solar air heater (SAH) has been numerically studied in this paper. Jet impingement technique, which is one of the important active techniques, has been implemented on the absorber plate of the SAH surface to increase the convective heat transfer performance. Several designs of elongated jet hole (EJH) technique (gradually increasing, gradually decreasing along the crossflow direction, and equally extended), which is highly effective application to get rid of cross-flow, has been inserted to the jet plate. The main interest of this paper is to investigate the effect of different EJH configurations on convective heat transfer performance and ηth of the SAH. 15 × 7 array of jets have been mounted on the confinement plate. Results have been compared with the conventional SAH, which has the jet impingement Case1. Numerical computations have been conducted using RNG k-ε turbulence model. Average Nusselt number (Nu) on the absorber plate surface, ηth of the SAH, and performance evaluation criteria (PEC) have been quantitatively investigated comprehensively. As a result of calculations, the Nu and ηth of SAH can be enhanced by 31.80 % and 2.46 %, respectively, using Case4 instead of Case1 at Re = 25000. Besides, the pressure drop of SAH dramatically rises by 10.26 %, when Case4 and Case1 compared with each other at Re = 25000. Despite increment in pressure drop, the PEC value achieves to 1.28. Finally, it is concluded that the equally extended EJH presents well performance compared to gradually increasing and decreasing EJH.

Influence of oblique angle variations on the thermo-hydraulic characteristics of the oblique fin heat sink with Al2O3 water nanofluid

The flow mixing through secondary flow is critical for improving the heat transfer of microchannel heat sinks. This study investigates oblique fin heat sinks (OFHSs) under forced convection conditions with Al2O3-water nanofluid under the Re 100–500. The study is referenced with a straight channel heat sink for benchmarking purposes. Five oblique angle configurations (15°, 25°, 35°, 45°, and 55°) were investigated at the constant fin pitch and constant width ratio (primary width-to-secondary width ratio) of 2:1. The RNG k-ε model has been employed with enhanced thermofluidic effect and wall treatment. The findings revealed that secondary flow generation leads the thermal boundary layer to redevelop at each fin, resulting in continuous fluid flow development. Pressure drop increment has been noticed with oblique angles 15° to 25°, and the variation is almost insignificant among the 35°, 45°, and 55° OFHS. The secondary flow rates were found to have a profound effect in all the cases. The 25° degree shows a higher average convection coefficient among all the OFHSs. Also, the convection coefficient varied in the following order for both water and nanofluid: 15° < 25° > 35° > 45° > 55°. The 25° OFHS enables a more uniform water/nanofluids temperature to build up in the streamwise direction than the 35°, 45°, and 55° OFHS. The thermofluidic analysis suggests that the proposed designs have superior heat convection performance than their flow resistance penalty. Therefore, the 25° OFHS offers a promising option for further parametric research in the future.

H-BN/DCM ve SiO2/DCM Nanoakışkanlarının Başınç Düşümlerinin İncelenmesi

The present study is about the investigation of the flow characteristics and pressure heads of h-BN &amp;amp; DCM and SiO2 &amp;amp; DCM nanofluids at various pipe diameters by using numerical methods. The pipe diameters are 0.0127 m, 0.0254 m, 0.0381 m, 0.0508 m, 0.0762 m. Dichloromethane (DCM) was used as base fluid in nanofluid preparation. Hexagonal boron nitride and silica were mixed into the base fluid by 1% when obtaining the nanofluids. Although nanofluids have been located in the center of many thermal and thermodynamic analyses, the scientific research about the energy losses caused by their increased viscosity compared to the base fluids have remained insufficient. This study investigates the pressure losses of several nanofluids and their behaviors in a pipe. It was found out that the highest increment in pressure drop was in SiO2-DCM which has the largest viscosity of 0.00056 kg/ms and the smallest increment in pressure drop is in DCM which has the lowest viscosity with 0.000413 kg/ms for a constant pipe diameter.

Thermal-hydrodynamic and exergetic study of two-phase flow in helically coiled pipe with helical wire insert

This paper presents a multi-objective experimental study, to enhance the thermal performance of the helically coiled pipe. The main objective of this study is the hydrothermal evaluation of single-phase (water) flow and two-phase flow (air-water) transition through a helically coiled tube at the presence and absence of helically coiled wire. Water flow rate was varied from 2 l/min to 8 l/min and air flow rate was varied from 1 l/min to 5 l/min which makes the volume fraction (VF) range of 0.110–0.714. Thermal-frictional and exergetic behavior of two-phase flow for a helically coiled tube with a helical wire insert have been studied. Results show that in exergy efficiency inside helical tube without turbulator for single-phase flow is 87% higher than when the turbulator is inserted. The second law analysis demonstrated that the exergetic efficiency decreases by the increment of VF and water flow rate. Generally, when pressure drop increment is less important than heat transfer augmentation, simultaneous use of two-phase flow and turbulator is recommended. Conversely, single-phase flow with turbulator is recommended when the desired pressure drop is low.

Thermohydraulic assessment of a novel hybrid nanofluid containing cobalt oxide-decorated reduced graphene oxide nanocomposite in a microchannel heat sink with sinusoidal cavities and rectangular ribs

The goal of this article is to assess the merit of utilizing an innovative water-based nanofluid containing the reduced graphene oxide‑cobalt oxide hybrid nanocomposite in a microchannel heat sink equipped with rectangular ribs and sinusoidal cavities. For this end, the two-phase mixture numerical model based on the finite volume technique and Coupled approach is used. The simulation is conducted at amounts of Reynolds number ranged from 100 to 500 with the nanofluid concentrations of 0.05%, 0.1%, and 0.2%. The thermophysical properties are temperature-dependent. The results indicate that though the created vortices decline by utilizing the nanofluid, the thermal features significantly improve due to enhanced thermal conductivity. The convective heat transfer coefficient, solid temperature, temperature uniformity, and thermal resistance promote by maximum amounts of 14%, 2.3%, 27%, and 25%, respectively. Also, considering the imposed pressure drop due to the use of the nanofluid, it was found that in all the cases, the nanofluid increases the heat transfer coefficient more than the pressure drop, which is an excellent outcome. Finally, it is unmasked that deploying the 0.2% nanofluid at Reynolds number of 500 improves the thermal features with the least pressure drop increment, and therefore, this case is recommended for practical applications.

Achieving ultra-high coefficient of performance of two-phase microchannel heat sink with uniform void fraction

Thermal management of high-power electronics/devices has been a very challenging issue for data centers, flourishing electric vehicle revolution as well as cooling of the first wall of a Tokamak fusion reactor. As a prominent cooling strategy, two-phase flow in microchannels has received extensive research over decades. However, inherent defects such as relatively low critical heat flux due to the dry out of liquid film near the exit of the channel and relatively high two-phase flow pressure drop at high heat flux still hinder extensive commercial applications. The present work proposes a robust microchannel heat sink design toward uniform void fraction distribution along the flow direction. The two-phase flow pressure drop will not increase significantly with increase in heat flux. This is made possible by an innovative and unique combination of diverging microchannel and counter-flow manifold, which enables extensive channel-to-channel heat transfer, especially near the end or inlet of the channels. Moreover, flow visualization reveals that nearly uniform void fraction distribution along the channel with relatively high bubble slug ratio is possible. For a relatively large area of 12 cm2 and under the limitation of wall temperature of 140 °C, a heat flux as high as 3525 kW/m2 is achieved without sign of reaching the critical heat flux with nearly negligible pressure drop increment comparing to single-phase convection for a relatively low mass flux of 600 kg/m2s. An ultra-high coefficient of performance of 75,675 is attained under a low inlet temperature and low mass flux.

Fully-developed laminar flow in trapezoidal ducts with rounded corners: a numerical solution and case study

PurposeThis paper aims to numerically solve fully developed laminar flow in trapezoidal ducts with rounded corners which result following forming processes.Design/methodology/approachA two-dimensional model for a trapezoidal duct with rounded corners is developed and conservation of momentum equation is solved. The flow is assumed to be steady, fully developed, laminar, isothermal and incompressible. The key flow characteristics including the Poiseuille number and the incremental pressure drop have been computed and tabulated for a wide range of: sidewall angle (θ); the ratio of the height of the duct to its smaller base (α); and the ratio of the fillet radius of the duct to its smaller base (β).FindingsThe results show that Poiseuille number decreases, and all the other dimensionless numbers increase with increasing the radii of the fillets of the duct; these effects were found to amplify with decreasing duct heights or increasing sidewall angles. The maximum axial velocity was shown to increase with increasing the radii of the fillets of the duct. For normally used ducts in hydrogen fuel cells, the impact of rounded corners cannot be overlooked for very low channel heights or very high sidewall angles.Practical implicationsThe data generated in this study are highly valuable for engineers interested in estimating pressure drops in rounded trapezoidal ducts; these ducts have been increasingly used in hydrogen fuel cells where flow channels are stamped on thin metallic sheets.Originality/valueFully developed laminar flow in trapezoidal ducts with four rounded corners has been solved for the first time, allowing for more accurate estimation of pressure drop.

Design of membrane humidifier using obstacles in the flow channels for ventilator

Inhalation gas humidification is a kind of major matter for patients using mechanical ventilation systems due to the necessity of keeping mucus layer at the suitable thickness and wetness. The performance of membrane humidifier with partially blocked gas channels, is investigated in this study. Three types of membrane humidifier channel arrangement, including a normal, wet channel with obstacles, and similar ones in both channels (wet and dry) are studied under various mass flow rates and temperatures. Flanged obstacles improve the thermal efficiency of the humidifier so that in this case the outlet dry air temperature can be increased about 4°by using 10 obstacles in both channels but they increase the pressure drop noticeably. PEC is calculated as a dimensionless parameter to compare the performance enhancement with pressure drop increment, simultaneously. Higher water recovery rate (WRR) and dew point temperatures at the dry side channel outlet, indicate the higher humidifier performance. At all mass flow rates, presence of obstacles improves the performance of the humidifier by increasing the dew point temperature and water recovery rate (WRR). Overall, the presence of obstacles on both channels amplifies the overall performance of the membrane humidifier in almost all cases.