Pitch Ratio Research Articles

Effect of Tube Bundle Arrangement on the Performance of PCM Heat Storage Units

The results of a comprehensive study on the charging and discharging of latent heat storage systems (LHSS) are presented. Multi-tube shell-and-tube units with variable layouts of tube bundles are examined. Two tube arrangements—in-line and staggered—are tested. A variable number of tubes and different tube positions in a bundle are investigated. Moreover, two pitch ratios are studied. Three commercially available substances are used as phase change materials (PCM). The results show that increasing the number of tubes reduces both the charging and discharging times. It is found that for a bundle of seven tubes with a pitch ratio s/d = 4.5, the in-line tube arrangement results in a shorter charging time, but the discharging time is shorter for a staggered tube arrangement.

Experimental investigation of heat transfer characteristics of steam generator with circular-ring turbulators

Heat transfer has been improved by creating turbulence in the fluid flow of heat exchangers through introducing various techniques. The present study investigated the heat transfer characteristics of steam generator with circular-ring tabulators with an inclination angle of 45° and a blocked ratio (BR) of 0.20 mm. The length ratios (LR) of 25%, 50%, 75% and 100%, pitch ratios (PR) of 1.0, 2.0, 3.0 and 4.0 and water flow rates of 12, 24 and 36 l/h were studied. The heat source used waste lubricating oil as fuel to produce steam. The results showed that the heat exchanger with circular-ring inserts provided a higher steam rate than that of a smooth tube by 6.88–10.35%, vapor quality (x) by 0.21–0.92, heat transfer by 1.27–1.55 times and the thermal efficiency by 0.46–0.68 depending on the PR, LR and FR. The optimum insert ratio was LR = 50% while 75% and 100% were not significantly different. The circular-ring inserts changed the flow behavior to turbulent flow. This increased the surface area, causing boundary layer interruptions leading to more heat exchange on the tube surface.

Study the dynamic performance of PM machines for different rotor topologies

<p>For hybrid and electric vehicle drive-train (automotive applications) achieving high torque and efficiency at a wide range of operating conditions can be considered an important matter. Therefore, precise structure optimization of the permanent magnet synchronous machines (PMSMs) is recommended. Consequently, the effect of the main leading design parameters (such as PM arrangement, magnet thickness, pole arc to pole pitch ratio, airgap length as well as the effect of shaft material) for a different number of rotor poles configuration of PMSM can achieve optimum design results in electric motors with economical cost and excellent performance. This paper submits a comparative analysis of different rotor topologies of (PMSM). Moreover, the dynamic performances of the suggested rotor geometry topologies are investigated based on investigation of finite element analysis (FEA). The analysis offers a piece of complete information about the magnetic flux distribution and magnetic flux density over the motor geometry. Gained results from the analysis are used to give a decision for the selection of a suitable PMSM design.</p>

Evaluation of efficiency, thermohydraulic performance evaluation criterion, and field synergy principle improvement of the parabolic solar collector containing the hybrid nanofluid using spring turbulators

In this paper, the study and simulation of turbulent flow inside a parabolic solar collector tube equipped with two spring insert samples with two different pitch ratios (P/D = 0.22, 0.44) and a specific cross-section are investigated. Heat transfer and properties of Cu–Fe3O4/Water hybrid nanofluid with volume fractions of φ = 1%, 3%, and 5% for the range of Reynolds numbers of 7000, 9000, and 11000 are selected and investigated using the single-phase method. The tube is used as the adsorbent pipe of a parabolic solar collector to investigate the performance of the parameters such as volume fraction, Nusselt number, pressure drop, parabolic solar collector efficiency, performance evaluation criterion, and field synergy principle. The results show that with decreasing the pitch ratio, Nu and solar collector efficiency increase. The maximum efficiency is 2.53 for a tube with P/D = 0.22 (Re = 7000, φ = 1%). The maximum efficiency is obtained under the same conditions in a tube containing the spring insert with P/D = 0.44 is equal to 2.39. At the same Reynolds numbers, the average of these velocities is significantly higher than a plain tube. Field Synergy Principle is a reliable criterion to investigate the mechanism of heat transfer increase that this coefficient value in the tube equipped with a spring insert is much higher than in a plain tube. This increase indicates the positive performance of the spring insert on the heat transfer rate and solar collector efficiency improvements. Therefore, spring inserts with a lower P/D are more desirable to achieve the highest efficiency of solar collectors as a source of renewable energy.

Heat Transfer Intensification in a Heat Exchanger by Means of Twisted Tapes in Rib and Sawtooth Forms

This experimental study aimed to intensify the aerothermal performance index (API) in a round tube heat exchanger employing twisted tapes in rib and sawtooth forms (TTRSs) as swirl/vortex flow generators. The TTRSs have a constant twist ratio of 3.0, a constant rib pitch ratio (p/e) of 1.0, and six different sawtooth angles (α = 20°, 30°, 40°, 50°, 60°, and 70°). Experiments were carried out in an open flow using air as the working fluid for Reynolds numbers between 6000 and 20,000 in the current study, which was conducted in a heated tube under conditions of uniform wall heat flux. A typical twisted tape (TT) was also tested for comparison. The experimental results suggest that TTRSs yield Nusselt numbers ranging from 1.42 to 2.10 times of those of a plain tube. TTRSs with larger sawtooth angles (α) offer superior heat transfer. The TTRSs with α = 20°, 30°, 40°, 50°, 60°, and 70° respectively, enhance average Nusselt numbers by 158%, 162%, 166%, 172%, 180%, and 187% with average friction factors of 3.51, 3.55, 3.60, 3.67, 3.75 and 3.82 times higher than a plain tube. Additionally, TTRSs with sawtooth angles (α) of 20°, 30°, 40°, 50°, 60°, and 70° offer APIs in the ranges of 0.99 to 1.19, 1.01 to 1.21, 1.03 to 1.26, 1.05 to 1.31, 1.07 to 1.42, and 1.09 to 1.48, respectively, which are higher than those of the typical twisted tape (TT) by around 5%, 7%, 11%, 16%, 25%, and 31%, respectively. This demonstrates that twisted tapes in rib and sawtooth form (TTRSs), with appropriate geometries, give a promising trade-off between enhanced heat transfer and an increased friction loss penalty.

CFD Simulation of Heat Transfer Characteristics in a Rectangular Duct with Trapezoidal Turbulence Promoters

The heat transfer rate from the hot surface to the coolant flow increases by placing the ribs on the surface of the coolant flow passage. The effect of turbulence promoters with different angle of attack and with a fixed tapered angle on the heat transfer characteristics in a rectangular stationary duct is considered for this study. Here turbulence promoters increase the heat transfer in the duct. The examination has been conducted on the rectangular smooth duct and rectangular duct with inverted V-shaped ribs of a different angle of attack. The rib angle attack of 45º, 60º, 90º and tapered angle 20º (fixed) on the top surface of the rib are considered. The rib blockage ratio and pitch ratio are 0.0553 and 10 respectively. The heat transfer characteristics are compared with Reynolds number of 6000. The heat transfer and computational flow analysis are conducted by k-epsilon turbulence model in ANSYS FLUENT. The tapered angled cross-sectional inverted V-shaped ribs of 60º shown high average heat transfer coefficients among the 45º, 60º and 90º smooth duct.

Entropy generation and thermal performance of tubular heat exchanger fitted with louvered corner-curved V-baffles

The current article deals with an experimental study on entropy generation analysis and thermohydraulic performance of a uniform heat-flux tube equipped with louvered corner-curved baffle tape (LCBT). Air was drawn into the inserted tube for the Reynolds number (Re) between 4760 and 29,300. The V-shaped LCBT arranged by V-tip in downstream direction was introduced with three baffle pitch ratios (PR = 1–2) and six louver angles (θ = 0–90°) for a fixed attack angle (α) of 30° and baffle height ratio (BR = 0.25). The impacts of investigated parameters on the thermal enhancement factor (TEF), Nusselt number (Nu), friction factor (f), and total entropy generation (S˙gen′) were examined. The measurements showed that the LCBT with the smallest values of PR = 1, θ = 0° give the largest Nu and f at about 4.4 and 19.2 times above the plain tube values, respectively. However, the greatest TEF around 2.23 was seen for employing the LCBT at PR = 1, θ = 45°. The entropy analysis also showed that the S˙gen′ is found to decline with the increment of PR and θ, whereas the minimal S˙gen′is at PR = 1, θ = 0° for lower Re but at PR = 1, θ = 45° for higher Re. Furthermore, the Nu and f empirical correlations for employing LCBTs were also proposed.

Thermal assessment of solar concentrated system with utilizing CNT nanoparticles and complicated helical turbulator

Turbulent flow of nanomaterial (mixture of CNT and water) within the circular tube of solar system as an absorber has been simulated numerically in this article. The circular tube has been equipped with complex swirl flow device to make the impingement of fluid with wall stronger and in this way warmer fluid can be achieved from this system. To concentrate the solar radiation, ten mirrors were utilized and geometric parameters have been calculated mathematically to reach the maximum optical performance. The maximum fraction of CNT is 0.025, thus involving single phase formulation is logical. Three configurations of device have been utilized in which two range of pitch ratio (S = 0.1, 0.25) were utilized in addition to configuration without twisting (WT). K-ϵ model was utilized in simulation which was based on finite volume method. Four ranges of flow rate (Q = 8, 12, 16, 20 Lit/min) was applied with inlet temperature of 291.15 K. As CNT utilizes with fraction of 0.025, the thermal performance (ηth) improves around 0.68% for Q = 20 which is 1.72 times stronger than that impact of Q = 8 L/min. Switching from WT to configuration of S = 0.1, leads to augmentation of ηth about 2.19% when Q = 20. When S = 0.1, elevate of Q causes friction factor (f) to decrease around 26.03% while convective factor (h) augments around 84.72%. As pitch ratio changes from 0.25 to 0.1, the amount of h increases around 14.13% while f augments around 47.88%.

Fluid flow and heat transfer in a rectangular ribbed channel with a hierarchical design for turbine blade internal cooling

• New design concept to develop high-performance internal cooling of turbine blades. • Greatly reduced pressure loss is achieved with negligible heat transfer reduction. • The underlying physics of pressure drop and heat transfer performance is clarified. • Various designs are examined to verify the feasibility of the new design concept. For internal cooling of a turbine blade, various advanced rib turbulators can markedly contribute to the heat transfer enhancement while suffering a great increase in pressure loss. In those designs, ribs with the same configuration are periodically and evenly mounted on the channel wall. In this context, this work proposes a hierarchical design concept to optimize the rib arrangement with the desired reduction in pressure loss. In terms of the rib height, this new design concept is implemented to construct three new rib configurations. Based on an established turbulence model, three-dimensional (3D) numerical simulations are entirely adopted to verify the feasibility of the new configuration in a wide Reynolds number range. The numerical results demonstrate that the optimal configuration with a linearly decreasing rib height can greatly reduce the pressure loss with a slight heat transfer deterioration. The negligible reduction in the heat transfer performance results from the enhanced fluid impingement on the reattachment region because of the lowering effect of the mainstream, although small ribs weaken the fluid impingement. The marked pressure drop reduction comes from the combination of the lowering effect and small ribs which constrains the separation vortex behind ribs. Furthermore, the comparison of the overall thermal performance is carried out considering a wide range of the Reynolds number, pitch ratios, and aspect ratios. The optimal configuration can greatly enhance the overall thermal performance up to 138.3% for the factor ( Nu / Nu 0 )/( f / f 0 ) and up to 32.5% for the factor ( Nu / Nu 0 )/( f / f 0 ) 1/3 . Eliminating the entrance effect of developing flow, the increment in the overall thermal performance is considerably reduced but still keeps at a high level. Finally, it is significantly highlighted that as a simple but effective improvement, the hierarchical design concept presents great potential in developing high-performance internal cooling of turbine blades.

Parametric study on the pull-out performance of screw connections in cold-formed thin-walled steel structures

Screw connections have been extensively used in cold-formed steel constructions due to convenient construction and high capacity. However, little attention has been paid to the pull-out performance and parametric effects of screw connections. In this paper, the pull-out performance of screw connections is experimentally and numerically investigated. The objective of this study is to develop a refined finite element (FE) model that can be used to parametrically analyze the pull-out performance of screw connections. Eight sets of experimental results are selected for comparison with the FE results to validate the accuracy of the FE model. Based on the validated FE model, parametric analyses of the main variables in screw connections are conducted to discuss the effects of the tensile strength, the steel plate thickness, screw diameter and the ratio of thread pitch to plate thickness on the pull-out performance of screw connections. The results indicate that the failure modes of specimens are mainly classified into screw hole extrusion and thread shear failure. It is also found that the tensile strength, the steel plate thickness, screw diameter and the ratio of thread pitch to plate thickness have significant effects on the pull-out resistance of screw connections. Particularly, the numerically obtained pull-out resistance are used to assess the accuracy of the codified design rules for screw connections, as given in the Chinese Code, North American Specification, British Standard and European Norm. The evaluation results reveal that the current design formulas are relatively conservative. The formula proposed by one referenced paper is insecure, while the distribution trend is basically consistent with the straight line of PS/PFEM = 1.0 (the ratio of the calculated values to the FE values is equal to1.0), therefore, it can be used as a good reference for calculating the pull-out resistance of screw connections. Besides, the modified design formula in this study has good applicability.

Electrochemical Characteristics of Pitch Coated Silicon/Graphite Anode Composites Using Surface Modification Process

The electrochemical characteristics of pitch coated graphite / silicon composites were investigated as anode material in lithium ion batteries. The anode materials were prepared with etched graphite using nickel chloride hexahydrate to create spherical pores on the graphite surface. The pore size was controlled depending on the calcination retention time and optimized for the insertion of silicon nanoparticles. Scanning electron microscopy, x-ray diffraction and thermogravimetric analysis were used to analyze the physical properties of pitch coated graphite / silicon composites. The electrochemical characteristics of the batteries were investigated by charge-discharge cycle, rate performance, cyclic voltammetry and electrochemical impedance spectroscopy tests in the eletrolyte of 1.0 M LiPF6 ( EC : DMC : DEC = 1 : 1 : 1 vol % ). Graphite/silicon/pitch electrode showed better electrochemical properties than the graphite electrode, and even nickel etched graphite was superior to graphite. Also, it was confirmed that both capacity and rate performance were significantly improved when the ratio of graphite, silicon, and pitch is 8 : 1 : 1 ( G8 Si1 P1 ). It is found that G8 Si1 P1 have the initial discharge capacity of 680 mAh / g, the capacity retention ratio of 90 % during 100 cycles and the retention rate capability of 91 % in 2 C / 0.1 C, 87 % in 5 C / 0.1 C.

Flow-Induced Vibrations of Two Flexible Tubes in Cross Flow

To further investigate fluid-structure–interaction problems that occur in the nuclear field such as the behavior of pressurized water reactor fuel rods, steam generator tubes, and other heat exchanger tubes, the flow-induced vibrations of two flexible tubes in tandem, side-by-side, and in staggered arrangements are investigated. First, a three-dimensional numerical model for fluid-structure interaction of flexible tubes in cross flow is developed. It is a three-dimensional fully coupled approach with solving the fluid flow and the structure vibration simultaneously. Second, results are presented in the form of force coefficients, dynamic response, trajectories, and wake vortex pattern. The effects of pitch ratio, tube arrangement, and flow velocity on the vibration response and the flow field characteristic are investigated. Critical pitch and critical velocity are obtained successfully. The critical velocity depends heavily on pitch ratio. Under the same pitch ratio and velocity, the side-by-side tubes have the maximum value of fluid force and vibration amplitude, followed by the staggered tubes the and tandem tubes in sequence. The trajectory and wake vortex pattern are highly dependent on tube arrangement, pitch ratio, and flow velocity.

Experimental and numerical study to optimize flow and heat transfer of airfoil-shaped turbulators in a double-pipe heat exchanger

This paper analyses heat and flow transfer in a double-pipe heat exchanger (DPHE). In the DPHE, the turbulators are added to the inner tube to raise its thermal performance. Although this approach increases the heat transfer, the pressure drop raises, leading to greater energy consumption. Therefore, the design of the turbulator should be optimized. This study optimizes the heat transfer and pressure drop of a DPHE with symmetrical 4-digit NACA airfoils with zero angle of attack as a turbulator. These airfoils have been exploited in a DPHE for the first time to reduce pressure drop according to their negligible production vortices. The thermal performance of four types of airfoil-shaped turbulators with different sets of the thickness (t), pitch ratio (PR), and Reynolds number (Re) have been assessed through experimental and computational fluid dynamics. In this context, the correlation of the Nusselt number (Nu) and friction factor (f) has been computed experimentally. Then, an objective function including the friction factor minimization and Nusselt number maximization has been optimized through Genetic algorithm to find the Pareto front. The results highlighted that ƞ enhances under small sets of Re. Further, an increase of t and PR drop result in a greater f and Nu, raising ƞ in overall. Finally, the maximum ƞ = 1.91 has been reached under Re = 6000, t = 0.3, and PR = 1.11.

Two-stage thermal-hydraulic optimization for Pillow Plate Heat Exchanger with recirculation zone parameterization

• PPHE is a promising alternative to conventional heat exchangers. • A two-stage thermal-hydraulic optimization method is proposed. • The developed PPHE model is evaluated with existing experimental data. • Average PEC of the two-stage optimized PPHE is improved by 29.3%. Pillow plate heat exchanger (PPHE) has become a promising alternative to conventional heat exchangers due to their satisfactory heat transfer performance and geometric flexibility. Nevertheless, the presence of recirculation zone (RZ) greatly restricts its thermal-hydraulic efficiency. In this study, a two-stage thermal-hydraulic optimization method with RZ parameterization was proposed. At the first stage, a genetic particle swarm optimization algorithm was developed, which combines a genetic algorithm with particle swarm optimization to maximize the thermal-hydraulic performance of PPHE. While at the second stage, the optimization objective was refined to further enhance the heat transfer characteristics based on geometrical parameters of RZ. The developed CFD model of PPHE was evaluated against existing experimental data and found to be in satisfactory agreement in terms of hydraulic diameter, Nusselt coefficient and pressure drop. Compared to the baseline design, the average PEC of the two-stage optimized PPHE was improved by 29.3% over a Reynolds number ranging from roughly 4,000 to 8,000, while the heat transfer area of RZ was reduced by 25.3% in average. The results revealed that a decreased welding spot pitch ratio contributes to the flow mixing between mainstream and the stagnant fluid downstream of the RZ, while smaller welding spot can significantly improve the turbulent energy dissipation of the mainstream, and therefore enhance the overall heat transfer.

Design of Magnetron Injection Gun and Solenoid for G-Band Gyro-TWT Based on Collaborative Optimization Method

In this article, a collaborative design method for gyrotron magnetron injection gun (MIG) and solenoid is proposed for the first time. On this basis, the shape of the electrodes and solenoid sizes is optimized by the means of global optimization techniques. Simplified theory and numerical methods of MIG have been developed, and the results agree well with the PIC simulation. By using the new method, the calculation time is reduced and the numerical stability has been greatly improved compared with that directly solving the Lorentz equation. As an example, a helical electron beam with a velocity pitch ratio of 1.20 and a transverse velocity spread of 1.65% is obtained for G-band gyro-TWT.

Влияние относительного продольного и поперечного шага на характеристики потока шахматного пучка каплевидных труб

The present work has been conducted to clarify flow behavior across staggered drop-shaped tubes bundle at various longitudinal and transversal pitch ratios (the tubes bundle configures in 18 cases). The investigation covers the effects of key design parameters of Reynolds numbers Re = (1,78–18,72)  103, longitudinal pitch ratios (PL = 1,44, 1,54, 1,64, 1,74, 1,84 and 2.04) and transversal pitch ratios (PT =1,24, 1,44, 1,64 and 1,82). ANSYS Fluent software package is used to predict the flow pattern around tubes. The results of this study showed that at a constant longitudinal pitch ratio, the minimum friction factor varies with the Reynolds number and transversal pitch ratio. As the Re increases, the friction factor decreases. The minimum values of the friction factor were achieved for (PL = 1,24 and PT = 1,44) at Re = 1,78  103, and (PT = PL = 1,64) at Re > 1,78  103. Correlation of the friction factor for the studied models were presented.

Analytical investigation of jet impingement solar air heater with dimple-roughened absorber surface via thermal and effective analysis

In this study, the thermal and effective efficiencies (ηthe and ηeff, respectively) of a dimple-roughened jet impingement solar air heater (DRJISAH) are analytically examined. The analysis is performed based on the following conditions: Reynolds number (Re) = 3000–24000; solar irradiance (Isr) = 700–1000 W/m2; dimple height ratio (ed/Dhd) = 0.016–0.031; dimple pitch ratio (pd/Dhd) = 0.269–0.810; arc angle (αd) = 30°–75°. An enhancement in ηthe by 18%–29% is achieved, which is corresponding to the ηthe of a jet impingement solar air heater. The ηeff of a DRJISAH is greater than that of a flat-plate solar air heater (FPSAH). However, at high values of Re, the useful thermal energy gain is dominated by frictional losses in the duct; thus, the FPSAH has a higher ηeff value than the DRJISAH. The optimum ηthe and ηeff for the DRJISAH are 74% and 70%, respectively, at ed/Dhd = 0.031, pd/Dhd = 0.269, αd = 60°, and Isr = 1000 W/m2. In addition, each dimple parameter is plotted against Re to obtain the best ηeff for the specified Re.

Experimental and numerical investigation of hydrodynamic performance of a new surface piercing propeller family

Today, passenger and racing boats increasingly utilize surface-piercing propellers. This type of propeller operates in two distinct phases of water and air simultaneously. As a result, this propeller type has additional characteristics that must be investigated separately from conventional propellers. A new family of surface piercing propellers was investigated using experimental and numerical methods. The family consisted of five propeller models with varying geometric features operating at an immersion ratio of 0.7. Experiments were conducted in the Sharif University of Technology's hydrodynamic group's cavitation tunnel. Additionally, using Star-CCM + software, the numerical simulation was performed using the RANS method for implicit unsteady flow with a sliding mesh technique in free surface conditions. The results indicate that by increasing the pitch ratio from 1.074 to 1.61, the critical advance coefficient value, which is in the range of 0.4–0.6, moves to 0.8–1 interval. Also, the efficiency enhances by 14% while raising the pitch ratio. The amplitude of force and moment fluctuation components increases at higher than 0.5 values of the advance coefficient by increasing pitch ratios. The expanded area grows proportional to an increased number of blades and as a result, the thrust and torque coefficients increase, but the efficiency does not improve significantly. Furthermore, the fluctuation amplitude of forces and moments applied to the key blade increases up to the critical advance coefficient in all models and then decreases for above critical values.

Analysis of numerical and grey relation method of the effect of helical tape insert density on the hydrothermal performance

In this study, the hydrothermal performance of the Double pipe heat exchangers(DPHEs) with a continuous and variable helical tape insert(HTI) conducted on the outer surface of the inner pipe was numerically investigated by using the generated three-dimensional(3D) computational fluid dynamics(CFD) models. The numerical analyzes were performed under variable pitch ratios (0.167≤λ≤0.500), annulus side Prandtl number(Pr) (5.9≤Pran≤7.8) and Reynolds numbers(Re) (4200≤Rean≤16000) conditions. The numerical model was first validated for the conventional equal HTI DPHE model by comparison with experimental data obtained from the literature and empirical correlations. The validated model was then used to determine the effects of the variable HTI on the outer surface of the inner pipe. The relationship between the Nusselt number(Nu) and Darcy friction factor(f) was examined by using Grey Relation Analysis(GRA) method. The using of the denser HTIs on the tube side inlet region increases Nu about 9% compared with the conventional model. The f values of the models with variable HTI densities were calculated as higher than the Equal model under all Re conditions. The obtained results from the GRA method, conventional Equal model can be used for low Re, but the Inlet model can be preferred for 14000 and above Re conditions.

Analysis of Uncertainties in Open Water Test of B-Series Propeller at Indonesian Hydrodynamic Laboratory

A propeller’s performance characteristics in open water typically refer to the variation of its thrust, torque, and efficiency with speed and revolution rate. This investigation provides a method for gaining a better understanding of the achievable accuracy. of the open water propeller test and presents an example of how to conduct a comprehensive uncertainty analysis of prediction models4 blades B-series model propeller, diameter 157.59 mm, pitch ratio 1.133 and Blade Area Ratio (BAR) 0.65 was carried out for this study. The methodologies presented using the ITTC recommended procedure to obtain individual measurement systems, measurement of individual variables, data reduction and experimental results. The bias limits for the individual measurement systems are estimated: propeller geometry, speed, thrust, torque, propeller rate of revolution, and temperature/density. The precision limits for single and multiple runs have been determined for the thrust coefficient (K T ) and torque coefficient (K Q ) for one advance coefficient (J), 5 sets of tests with 3-speed measurements in each set are conducted, totaling 15 test runs. The experimental test results have represented as relative numbers the bias for K T represents 98.1 % and the bias for K Q represents 99.4 % of the total uncertainty for the mean value of 15 tests. The uncertainty analysis results of the open water propeller were recommended in an acceptable range of the 95% level of confidence.