Average Heat Transfer Coefficient Research Articles

Evaporation performance of propane in offset strip-fin plate heat exchanger for refrigerant-based battery thermal management in electric vehicles

This study investigates the potential of refrigerant-based cooling (RC) using a natural refrigerant (propane) and lightweight energy-efficient brazed plate heat exchangers (PHXs) in the battery thermal management systems (BTMSs) of the electric vehicles (EVs). Experimental assessments were conducted to analyze the evaporative heat transfer characteristics of propane within an offset strip-fin flow-structured PHX under various operational conditions resembling the BTMS operation. The battery discharge rates, often represented by the C-rate, are determined by the discharging current relative to the battery's capacity. In this study, a heat generation model based on the C-rate was employed to evaluate the thermal performance of the battery. Parameters, such as mass flux (G) at 30–70 kg/m2s, discharge rates (C-rate) of 1, 1.25, and 1.5C, and saturation temperatures (Tsat) of 16–24 °C were explored, with the inlet vapor quality (xin) in the range of 0.1–0.8. The influence of G and Tsat on the heat transfer performance showed that higher G values (60 and 70 kg/m2s) achieved the maximum heat transfer coefficients (HTC), which resulted in impractical pressure drops (PD). While higher HTC and lower PD were observed at a Tsat of 24 °C, concerns about increased inner wall temperature (Tiw) and safety emerged at this temperature. Hence, the optimum conditions of G (30 and 50 kg/m2s) and Tsat (16 and 20 °C) were investigated. The average HTC increased by 29, 27, and 21 % at 50 kg/m2s compared to that at 30 kg/m2s with Tsat of 20 °C, resulting in an average of 0.7, 0.9, and 1.2 °C reduction in the Tiw for C-rates of 1.5, 1.25, and 1C respectively. Compared to the Tsat of 16 °C, higher HTC and lower PD were observed at 20 °C, however, the Tiw was in the range of 21.12–20.47 °C for Tsat of 20 °C, which is 3.5–4 °C higher than that at Tsat of 16 °C. The results from the critical heat transfer coefficient analysis showed that the peak heat dissipation with minimal wall temperature was attained with optimal xm of 0.45–0.5, which enhanced the cooling efficiency for both the G values of 30 and 50 kg/m2s, and both the Tsat values (16 and 20 °C).

Experimental heat transfer results and flow visualization of horizontal Near-Saturated liquid nitrogen flow boiling in uniformly heated circular tube under Earth gravity

This study investigates 1-ge horizontal flow boiling of liquid nitrogen with a near-saturated inlet along a circular tube of dimensions 8.5-mm inner diameter and 680-mm heated length. Experiments are conducted using a payload developed for eventual parabolic flight experiments. The operating parameters varied are mass velocity of 406.76–1572.77 kg/m2s, inlet quality of −0.05 to −0.01, and inlet pressure of 336.29–493.07 kPa. High speed video recordings are presented to explain two-phase flow structure and regime transitions which are visualized through a transparent tube in a visualization section situated downstream of the heated tube. Recognized flow patterns are bubbly, plug, slug, stratified annular, and annular. Heat transfer results are presented and discussed in terms of flow boiling curve trends, streamwise wall temperature profiles, streamwise heat transfer coefficient (HTC) profiles, and average HTCs. Previous HTC correlations are evaluated against the measured HTC data, of which two are identified for superior accuracy in predicting cryogen data. Finally, this study confirms the reliability and readiness of the payload for subsequent parabolic flight experiments intended for acquisition of microgravity data.

Numerical and experimental investigation of the flow and heat transfer characteristics for cold storage heat exchanger

Decreasing the freezing time of the cold storage heat exchanger was an effective way to reduce the risk of cold chain breakage and the fluctuation of cold chain temperature. A validated unsteady mathematical model of the cold storage heat exchanger was established to analyze the transient evolution of temperature, velocity, ice distribution, and heat transfer coefficient for different diameters of heat transfer tubes and coolant temperatures. The results showed that there were four stages of temperature in the cold storage heat exchanger, namely the primary cooling stage, the freezing stage, the secondary cooling stage, and the constant temperature stage. The ice fraction distribution and the heat transfer coefficient were inextricably linked to the water's natural convection. The average heat transfer coefficient decreased with decreasing coolant temperature and increasing heat transfer tube diameters. The freezing time decreased with the coolant temperature and the diameter of the heat transfer tubes decreasing. The tendency of the inhomogeneity of ice distribution first increased with the ice fraction up to 0.75 and then decreased with the ice fraction over 0.75. The inhomogeneity decreased with the coolant temperature increasing when the diameter of the heat transfer tubes was greater than 2 mm.

3-D numerical simulation of the heat transfer of a fluidized bed with a horizontal tube bundle and Geldart D particles

In the present study, a numerical simulation is performed to analyse hydrodynamic and heat transfer of a fluidized bed in a vertical channel. As a novelty, MP−PIC method is applied to 3-D tube bundles immersed in a fluidized bed with Geldart D particles. The main results are compared and validated using the experimental results published in the literature.In both tube bundle distributions, the lowest heat transfer coefficients were obtained in the top region of the tube, which represents approximately 58% of the time average heat transfer coefficient of the surface tube. This behaviour differs at the bottom and sides, where particles are continuously being replaced by other particles, resulting in low particle volume fractions and higher heat transfer coefficients.Analysing each tube arrangement for the cases with the same gas velocity and particle diameter, the results numerically obtained were consistent with the experimental findings. The present study found that the time average heat transfer coefficient for the staggered arrangement was approximately 6%, 5% and 1.6% higher than that in-line, for the particle diameter of 1400, 1600 and 1850 μm, respectively. Some discrepancies can be highlighted when comparing the experimentally and numerically obtained time average heat transfer coefficients, with maximum differences close to 18%, which correspond to the cases with the highest gas velocity and particle diameter (1.71 m/s, 1850 μm).

Experimental study of R600a boiling in microfin tube

This paper presents experiments to investigate flow boiling and pressure gradients of R600a. The study employed microfin and smooth copper tubes simulating conditions in a domestic refrigerator, using low mass fluxes (MFs) and saturation temperatures (Tsat). The test sections featured a tube length of (400 mm), an inner diameter of (4.3 mm), and an outer diameter of (5 mm). Test conditions varied, including MFs of (25, 35, and 45 kg m−2 s−1), vapor quality from (0.18–1), Tsat of (−15, −9, and −5 °C), and HFs of (10, 14, and 18 kW m−2). Both tubes shared identical dimensions, clearly comparing microfin impact on flow boiling characteristics. The study evaluated enhancement factor (EF), penalty factor (PF), and overall efficiency (η) by comparing heat transfer coefficients (HTC) and pressure gradients in the microfin tube versus the smooth tube. Results indicate a significantly boosted HTC in the microfin tube compared to the smooth tube, with a reasonable increase in pressure drop. Under specific conditions (HF of 10 kW m−2, Tsat of −9 °C, and MFs of 25 kg m−2 s−1), the average HTC is enhanced by 325%, while the pressure drop is increased by 150%. Experimental HTC and frictional pressure gradient comparisons aligned well with values predicted by existing literature correlations.

Multi-tiered configurations improved flow boiling performance: Comparation investigation of leaf vein inspired two-tiered and three-tiered open microchannels

Microchannel heat sinks with expanding flow area along with the flow direction are able to suppress flow instability and reduce pressure drop during two-phase flow boiling by offering broadening volume for bubble elongation and growth that suppress the slug blockage and flow reversal. In this regard, microchannels with expanding area perpendicular to flow direction are supposed to obtain the comparable results, as the bubbles migrate to the downstream and top of microchannels simultaneously. However, the relevant study about multi-tiered microchannel heat sinks was limited and the corresponding flow boiling characteristics remained elusive. In this work, leaf vein inspired two-tiered open microchannel (LTWOMC) and three-tiered one (LTHOMC) were proposed and comparative flow boiling experiments were carried out. The outcomes indicated that LTWOMC obtained earlier ONB, which was 6.4 °C lower than LTHOMC at G = 220 kg/m2·s, the average local convective heat transfer coefficient (hcon) and average two-phase one (htp) of LTWOMC were maximumly enhanced up to 36.3% and 148.7% at G = 150 kg/m2·s, respectively. The pressure drop (ΔP) of LTWOMC was generally larger than LTHOMC at all mass fluxes, which led to the cooling coefficient of performances (COPs) of LTHOMC superior compared to LTWOMC under all working conditions. Moreover, LTHOMC exhibited better flow stability than LTWOMC with lower amplitudes and standard deviations of both wall temperature and pressure drop. In general, the three-tiered hierarchical configuration is more suitable than two-tiered one for flow boiling heat transfer.

NUMERICAL AND EXPERIMENTAL INVESTIGATIONOF STEAM FILM CONDENSATION ON A VERTICAL TUBE

NUMERICAL AND EXPERIMENTAL INVESTIGATIONOF STEAM FILM CONDENSATION ON A VERTICAL TUBE

Heat transfer on impingement cooled meshing spur gears: Experimental comparison of into-mesh, out-of-mesh and inclined impingement methods

Oil jet impingement cooling is the standard approach to cool high-speed high-power gears. The heat transfer between oil jets and gears is experimentally investigated in this paper. The three established methods of oil jet impingement cooling -into-mesh, out-of-mesh and inclined impingement on one of the gears- are studied. Heat transfer coefficients for these methods are experimentally determined. A loss correction approach is implemented for the evaluation of measurements. For the inclined impingement method, heat transfer on the non-impinged gear and the influence of meshing on the heat transfer coefficient are investigated. Gear meshing has an insignificant effect on the average heat transfer coefficient over the gear tooth. However, the spatial distribution of the heat transfer coefficient depends on the meshing configuration. Significant cooling on the non-impinged gear is observed with the inclined impingement method. The inclined impingement method is superior to the into-mesh and out-of-mesh methods at all measured operating points.

Air Equalizing Mechanism in Cooling Performance Improvement of Vertical Delta-Type Radiators

Based on the design and measured data of one actual tower, a three-dimensional numerical model for a natural draft dry cooling tower (NDDCT) was created and validated under constant heat load. This enabled the performance improvement mechanism of air equalizing on vertical delta-type radiators (VDRs) to be clarified by detailed analysis of key parameters, such as the exit water temperature, heat transfer coefficient, and mass airflow. Under the impact of typical ambient crosswind, all VDRs were retrofitted with air-side-equalizing devices. It was found that the exit water temperatures of the whole NDDCT decreased by 0.865 °C, 0.593 °C and 0.186 °C under the studied ambient crosswind speeds of 2.5 m/s, 4 m/s and 12 m/s, respectively. The performance improvement mechanism of air-side equalizing was investigated for three VDRs, which were located on the upwind, tower lateral, and downwind sides under crosswind impacts. Besides the studied VDRs, the performance of the neighboring VDRs behind them was also improved by the optimized aerodynamic field and the reduced hot wind recirculation around them. In addition, the average heat transfer coefficients of the VDRs were enhanced, which could lay the foundation for improving the cooling performance of thermodynamic devices with VDRs.

A hybrid approach towards evaluation of average heat transfer coefficient in twin-roll strip casting mold

Continuous casting stands out as one of the most efficient and productive methods for producing billets, slabs, or thin sheets while conserving energy. Understanding the solidification dynamics and achieving defect-free sheets in continuous casting necessitates the accurate prediction of heat transfer coefficient (HTC) at the mold metal interface. Accurate prediction of HTC helps in selecting process parameters such as superheat temperature and casting velocity, which directly affect the production rate and quality of the cast component. Determining the HTC is a complex process, as it is influenced by various process parameters such as casting size, casting speed, superheat temperature, surface roughness, type of water used as a coolant, nozzle design and wettability. Therefore, the present study proposed a hybrid approach for finding HTC in a twin roll strip casting mold through a solidified shell shape, which is influenced by the factors affecting the heat transfer at the mold-metal interface. This approach integrates the experimental and simulation investigations. The numerical investigation used a three-dimensional coupled fluid flow and heat transfer equations with an assumed range of HTC (100–2000 W/(m2K)). The solidified shell shape for different HTCs was compared with the experimental solidified shape form at the outer wall of the mold using the solidification criteria. Results indicate that the initial HTC range of 100–1000 W/(m2K) does not lead to blockage of the graphite mold outlet. However, as HTC values approach 1000 W/(m2K) to 1400 W/(m2K), the melt obstructs the mold exit based on solidification criteria. The HTC values (1350 ± 150 W/(m2K)) obtained from the proposed methodology for mold, align well with the HTC values (1183 ± 593 W/(m2K)) calculated using lamellar spacing of the Al-Mg2Si composite microstructure. This hybrid approach presents a novel and straightforward method for determining HTC, offering accurate predictions that can enhance the precision of continuous casting models and provide a more nuanced understanding of solidification behavior.

Effect of immersed tubes configurations on mixing and heat transfer of mixed biomass and silica sand in a bubbling fluidized bed using CFD-DEM and statistical experimental design analysis

The presence of immersed tubes within fluidized beds enhances mixing efficiency and heat transfer. However, the influence of design parameters remains unexplored systematically. This study investigates the impact of design parameters on mixed biomass fluidized beds with immersed tubes employing a combined approach of CFD-DEM simulations and 2k factorial design analysis. Findings reveal that the angle between tubes and tube diameter are primary influential parameters, significantly influences particle mixing and heat transfer efficiency. Optimal conditions, identified through analyses of averaged mixing index and heat transfer coefficient, point to a staggered configuration with specific dimensionless of tube diameter per column width of 0.0515 and a tube spacing per tube zone height of 0.14. These insights offer valuable guidance for optimizing and emphasize the significance of design parameters incorporating immersed tubes, providing practical guidelines for enhancing mixing efficiency and heat transfer in various applications, especially those employing mixed biomass and silica sand.

Numerical study of flow and thermal characteristics of pulsed impinging jet on a dimpled surface

This research comprehensively investigates the flow and thermal characteristics of a pulsating impinging jet over a dimpled surface. It analyzes the impact of key parameters (e.g., inlet velocity pulsation functions, pulsation frequency, amplitude, dimple pitch, dimple depth, Reynolds number) on flow patterns and heat transfer. Validated computational fluid dynamics and the Re-normalization group turbulence model are employed to accurately simulate complex turbulent flow behavior. Local and average heat transfer coefficients are calculated and compared to steady impingement cases, revealing the potential benefits of pulsation for heat transfer enhancement. The study also examines how pulsation-induced flow modulation and thermal mixing affect heat transfer mechanisms. Results indicate that combining fluctuating flow with a dimpled surface can improve heat transfer rates. In summary, increasing pulsation amplitude consistently enhances heat transfer, while the effect of frequency varies between impinging and wall jet zones.

Effect of an Exhaust Heat Exchanger with Inserts on the Performance of Thermoelectric Generators

A thermoelectric generator is used as a waste heat recovery system for generating electric power. The thermoelectric generator system consists of an exhaust heat exchanger, a thermoelectric module, and a water heat exchanger. The aim of the current work is to explore different types of inserts used in the test section of the exhaust heat exchanger and power generation of thermoelectric generators at different operating conditions. An experimental setup has been developed for conducting experimental investigation on thermoelectric generators to find the effect of the exhaust heat exchanger (EHE) with inserts on the performance of thermoelectric generators. The cone (G-type test section) and cone-cylinder (H-type test section) type inserts were introduced to enhance the performance of the thermoelectric generator. Compared with an insert-free (empty, F-type) thermoelectric generator with cone and cone-cylinder type inserts in terms of the output power, the average heat transfer rate and convection heat transfer coefficient of F-type, G-type, and H-type test sections of the EHE are 358, 468, and 459 W and 76, 100, and 97 W/m2K, respectively. It shows that the G-type test section of EHE exchanges more heat from engine exhaust to the hot surface of the thermoelectric module through the wall of the EHE. The G-type test section created more temperature difference; obviously, it generated more power output. It was observed that the G-type and H-type test sections of exhaust heat exchangers improved average maximum output power by 29.49% and 26.11% than that by the F-type test section of heat exchanger, respectively. The F-type, G-type, and H-type test sections of exhaust heat exchangers showed a maximum average efficiency of 0.80, 0.78, and 0.70%, respectively.

Influence of Entrance Geometry and Thermal Boundary Conditions on Heat Transfer in a Rectangular Channel with 45 Deg Angled Ribs on One or Two Principal Walls

The purpose of this paper is to numerically investigate the influence of the entrance geometry and thermal boundary conditions on the local and averaged heat transfer coefficient in a ribbed rectangular channel with an aspect ratio of 5. Ribs, angled at 45°, were periodically deployed on one or two opposite sides, while the remaining walls of the rectangular channel were assumed to be smooth and unheated. The effect of entrance conditions was addressed by considering either a smooth or a ribbed unheated section upstream of the ribbed heated section. The effect of the thermal boundary condition was studied by considering a uniform heat flux imposed at the inter-rib region, or at the inter-rib and the rib baseplate, or at the whole interface between the ribbed surface and the coolant. Results, presented in the form of spatially resolved and spatially averaged Nusselt numbers, show that a ribbed section preceding the heated test section affects the heat transfer coefficient, relative to a smooth entrance section, for several repetitive modules. The influence of the thermal boundary condition was found to be mainly concentrated in the surface regions immediately upstream and downstream of each rib, with small differences, in terms of spatially averaged Nusselt numbers. The presented investigation is meant to point out that heat transfer experiments on ribbed channels, massively provided by the heat transfer community according to the current technical literature, should provide an exhaustive description of the entrance and thermal boundary conditions assumed in the experiments and eventually to discuss how they could potentially affect the results.

An experimental and numerical investigation of thermofluidic properties on the novel curved microchannel heat sink with slotted section

The current work proposes the development of a novel curved microchannel heat sink by modifying the existing flat microchannel heat sink for enhancing the heat dissipation in the electronic device without significant pressure drop penalty. The inspiration for the curved channel is taken from a NACA airfoil. The microchannel comprises two sections: a curved section and a slotted straight section. Experimental and numerical investigations are performed on the proposed geometry to study the thermofluidic properties for Reynolds number (Re) ranging from 200 to 500 using DI water as working fluid. Fluid flow and heat transfer are analysed by carrying out a full domain numerical simulation in ANSYS Fluent 19.0. The thermofluidic properties of the curved microchannel heat sink (CMCHS) and straight microchannel heat sink (SMCHS) are compared numerically by keeping the geometrical parameters (hydraulic diameter, foot area and fin area) and inlet parameters (inlet velocity and heat flux) identical. The average heat transfer coefficient (havg) of CMCHS is enhanced over SMCHS due to the formation of vorticities in the slotted region owing to the fluid intermixing and boundary layer disruption. The presence of curved section leads to reducing pressure drop penalty pertaining to gravitational effects. Together, the curved section and slotted section enhance the performance factor of CMCHS over SMCHS. The vortices formed increase as the Reynolds number increases, enabling an increase in the heat transfer coefficient. Therefore, the performance factor also increases as the Reynolds number is increased. An enhancement of ≈ 67.6 % in havg is achieved for Re = 500 in CMCHS compared to SMCHS with DI water as the working fluid.

Aerothermal performance of cavity tip with flow structure effects in a transonic high-pressure turbine blade

Understanding the mechanisms of leakage flow control and heat load distribution is important in optimizing the structure of cavity tips in gas turbines. This paper investigates the aerothermal performance of cavity tip in a transonic high-pressure turbine stage. By analyzing flow structure, the effects of squealer height, squealer width and gap height on aerothermal performance are explained. It has been found that both the leakage flow and heat load distribution are influenced by the structure of vortices in the cavity. The leakage flow is controlled by the suction-side cavity vortex and the scraping vortex. The heat load distribution relates to the “M-shaped” leakage flow induced by the scraping vortex. The geometric parameters can affect the structure of vortices, which then impacts the aerothermal performance of cavity tip. As the squealer height is 2.5τ0, both the leakage flow rate and average heat transfer coefficient decrease by 0.64 % and 6.6 %, respectively. A multi-objective optimization with a feedforward neural network prediction is conducted to determine the distribution characteristics of optimal design parameters. The optimal values are approximately 2.34 for the expansion ratio, 0.5τ0 for the squealer width and 0.5τ0 for the gap height. The optimal squealer height ranges from 1.5τ0 to 2.5τ0.

Three-dimensional transient CFD simulation of lignite chemical looping gasification in a circulating fluidized bed

In this work, a full-loop 3D computational fluid dynamics (CFD) numerical simulation of the chemical looping gasification (CLG) process of lignite in a circulating fluidized bed (CFB) was performed using a two-fluid Eulerian-Eulerian model. The results showed that the CFD simulation effectively captured the axial and radial velocities of the particles. More radial flow occurred in the bottom part of the riser and inside the cyclone. The exothermic reaction became dominant within 7s, while the heat-absorbing reaction became dominant between 7 and 15s. The aggregation regions of syngas moved up with that of the high-temperature zone, and CO was the main contributor to the syngas. The particle size in the range of 175–225 μm was inversely proportional to the size of the average heat transfer coefficient (HTC) in the riser. Extremely small particle size saturated the bed, suppressing the HTC. The peak of the HTC was 387.7 W/(m2·K), which occurred in the upper-middle region of the riser and reached. The maximum HTC average value was 180.6 W/(m2·K). Finally, experimental data were used to verify the reliability of the model.

On the Aero-Thermal Performance of Rim Film Cooling in the Squealer Tip of a Linear Turbine Cascade

Abstract The present study proposes a novel rim film cooling design, motivated by the fact that the suction-side rim and the cavity floor near the leading edge of a conventional squealer tip with a camber-line film hole array are directly subjected to high-temperature gas. The new design consists of cooling injection for rim-hole or -slot cooling at the leading edge. The parameters of injection geometry and cavity depth are also discussed in this study. The flow physics, leakage flowrate, heat transfer characteristics, and vortices in the cavity are carefully analyzed. The results show that rim film cooling can substantially inhibit tip heat transfer and the amount of hot leakage flow. Compared with the typical design, the maximum and average heat transfer coefficients of the blade tip of the rim slot case are reduced by 12.83% and 5.43%,, respectively. The variation in cavity depth is sensitive to the heat transfer on the cavity floor of the squealer tip blade. With the optimal design, the average and maximum heat transfer coefficients are reduced by 14.42% and 14.21%,, respectively. In addition, the leakage flowrate can be reduced by a maximum of 3.67% by rim injection compared with the conventional squealer tip.

Experimental evaluation of performance, drying and thermal parameters of guava slabs dried in a forced convection indirect solar dryer without and with thermal energy storage

The forced convection indirect solar dryer (FISD) provides better quality food products for lower duration than open sun drying (OSD). The drying experiments on guava slices were executed on an FISD without a thermal energy storage (TES) (model-1) and with TES (model-2) to determine the impact of TES on drying. The guava slices attained a final moisture content in 14 and 9 sunshine hours in model-1 and model-2, respectively. The drying models appropriate to describe guava slices in model-1, model-2 and OSD were Page and modified Page models. The drying rate in model-1 and model-2 was found to be 0.3936 and 0.5728 kg/h, while the effective diffusivity was 7.98 × 10−9 and 8.63 × 10−9 m2/s (average), respectively. The average heat and mass transfer coefficients were 4.842 W/m2K and 4.20 × 10−3 m/s in model-1 & 5.394 W/m2K and 4.68 × 10−3 m/s in model-2. The average drying efficiency and specific moisture extraction rate were 6.84 % and 0.597 kg/kWh in model-1 & 9.77 % and 0.972 kg/kWh in model-2. The specific energy consumption and activation energy were decreased by 38.57 % and 5.25 % in model-2 compared to model-1. The performance, drying and thermal parameters were found to be better in model-2.

3D Simulations of Nucleate Boiling with Sharp Interface Vof and Localized Adaptive Mesh Refinement in Ansys-Fluent

Abstract The present work demonstrates the use of customized Ansys-Fluent in performing 3D numerical simulations of nucleate boiling with a sharp interface and adaptive mesh refinement. The developed simulation approach is a reliable and effective tool to investigate 3D boiling phenomena by accurately capturing the thermal and fluid dynamic interfacial vapor-liquid interaction and reducing computational time. These methods account for 3D sharp interface and thermal conditions of saturation temperature refining the mesh around the bubble edge. User-Defined-Functions (UDFs) were developed to customize the software Ansys-Fluent to preserve the interface sharpness, maintain saturation temperature conditions, and perform effective adaptive mesh refinement in a localized region around the interface. Adaptive mesh refinement is accomplished by a UDF that identifies the cells near the contact line and the liquid-vapor interface and applies the adaptive mesh refinement algorithms only at the identified cells. Validating the approach considered spherical bubble growth with an observed acceptable difference between theoretical and simulation bubble growth rates of 10%. Bubble growth simulations with water reveal an influence region of 2.7 times the departure bubble diameter, and average heat transfer coefficient of 15000 W/m2-K. In addition, the results indicate a reduced computational time of 75 hours using adaptive mesh compared to uniform mesh.