Highest Thermal Performance Factor Research Articles

Effect of the lengths of multiple splitter plates on the flow past a bank of cylindrical tubes

ABSTRACT A two-dimensional numerical study of the crossflow past a staggered cylindrical tube bank with multiple splitter plates attached behind the tube was performed. Simulations were conducted by keeping the central splitter plate’s length equal to the tube diameter while varying the lengths of the other two splitter plates positioned at the top and bottom of the central one. The results were validated by means of a grid independency study and via comparison with available experimental and numerical studies in the open literature. The Nusselt number, friction factor (f), and thermal performance factor (η) variations at length ratios to tube diameter ranging from 0.1 to 1 were investigated as a function of the Reynolds number between 5500 and 14,500. The friction factor was found to be around 0.25 at low length ratio case where it increased up to 2.4 at high length ratios on average within the Reynolds number range investigated. The Nusselt number was found to be higher for all the length ratio values when compared with the use of one splitter plate, and it showed an increasing trend along with the increasing lengths of the two additional splitters. It increased from 81 to 155 on average within the Reynolds number range investigated due to the additional splitter plates. The η for the tube with additional splitters that had a length ratio of 0.4 was calculated as 1.42, which was an average of 13% higher when compared with the one splitter plate case that showed a thermal performance factor equal to 1.26. This length ratio was determined to be optimum based on the highest thermal performance factor and the increase of 35% and 8% in the Nusselt number when compared with the bare tubes and the one plate case, respectively.

Numerical investigation on vortex cooling flow and heat transfer characteristics for gas turbine blade with variable coolant chamber cross-sectional shapes

In this paper, according to the actual size of gas turbine blade interior space, eight vortex cooling models with different cross-sectional shapes of coolant chambers are established. Rectangular, Circle, Trapezoidal up, Trapezoidal down, Ellipse up, Ellipse down, Sine up and Sine down are the eight coolant chamber shapes. Functions of variable coolant chamber structures on vortex cooling flow and heat exchange characteristics are numerically analyzed by verifying the Standard k- ω turbulence model and conducting grid independence analysis. Research results show that the heat exchange ability of Sine up coolant chamber is the best compared with the other coolant chambers. The cool air enters the vortex chamber at a faster speed and impacts on the target surface to form a high-pressure area and a low-temperature swirl. The more the cool air moves downstream, the greater the turbulent kinetic energy becomes, which is more conducive to the heat transfer. Therefore, Sine up coolant chambers have the highest thermal performance factor. Due to the low drag coefficient and high target surface average Nusselt number of Ellipse up, its thermal exchange performance is second only to that of Sine up. Circle coolant chamber will not bring favorable factors to engineering application because of the slowest flow speed and the worst heat exchange capacity. For Trapezoidal up and Trapezoidal down, the flow velocity, pressure distribution, turbulent kinetic energy intensity and heat transfer uniformity are almost the same as Rectangle coolant chamber. The models of Ellipse down and Sine down coolant chambers exhibit less turbulent kinetic energy strength to heat transfer and higher temperature in the vortex chamber, and it is not suggested for cooling system optimal design.

Thermal performance of elliptical pins on a semicircular concave surface in the staggered array jet impingement cooling

In a jet impingement cooling, decreasing heat transfer on the last jet's region due to the strong crossflow significantly increases thermal stress on the material. Thus, the main objectives of this study are to achieve relatively more uniform heat transfer distribution and enhance heat transfer on the surface compared to conventional jet impingement cooling (CJIC) configuration by mounting elliptical pins on the impingement regions. From this point of view, we have investigated the thermal performance of elliptical pins mounted on the impingement region of a staggered array jet impingement cooling (SJIC) on the semicircular concave surface. Numerical analyses were performed under various Reynolds numbers (Re = 5000, 15000, and 25000), jet nozzle-to-target surface spacing (0.5 ≤ G/d ≤ 8.0), and dimensionless orifice plate-target surface gaps (H/d = 4.0 and 8.0). Average Nusselt (Nu) numbers, local Nu contours, flow properties, and Thermal Performance Factor (TPF) on pinned and smooth target surfaces were studied in detail. Results showed that the local and area-averaged Nu numbers increased with reducing G/d and roughening of the surface with elliptical pins compared to conventional SJIC. Maximum heat transfer enhancement was obtained as 55.68% at H/d = 8.0 with extended jets (G/d = 0.5) and elliptical pin roughening surface design. Besides, the highest TPF on the pinned surface is achieved as 1.10 by G/d = 2.0 and H/d = 8.0 at Re = 25000. Furthermore, mounting elliptical pins on the surface provided more uniform heat transfer distribution on the surface compared to flat surface by means of significantly enhancing heat transfer on the last jet region.

Numerical investigation of heat transfer augmentation and frictional loss characteristics in heat exchanger tube with the use of novel perforated rectangular cut twisted tape

ABSTRACT This paper focuses on augmentation of heat transfer and thermal performance factor of tubular heat exchanger by using a novel Perforated Rectangular Cut Twisted Tape (PRCTT) and comparison was made with Plain Tube (PT), Simple Twisted Tape (STT) and Rectangular Cut Twisted Tape (RCTT). Analysis of Nusselt number and friction factor for the twisted tape insert having twist ratio (TR) of 3, rectangular cuts of 2 mm width and 1 mm depth is done. Rectangular cuts of different pitch, that is, 3 mm, 5 mm and 7 mm is used for the analysis. To reduce the friction factor, further analysis has been done with perforation of circular hole in the same RCTT with perforation ratio (d/w) of 0.55 in the core of insert. Numerical analysis shows that in turbulent zone (4000<Re > 16000), highest enhancement in Nusselt number is 2.3 times and highest enhancement of friction factor by 3.2 times with comparison to plain tube when reducing the pitch of rectangular cuts. Perforation further decreases the friction factor by 20%. Highest thermal performance factor is observed 1.48 with the use of Perforated Rectangular Twisted Tape (PRCTT) at Re = 4000.

Experimental investigation of the effect of flexible/rigid flag on heat transfer

This experimental work investigated the heat transfer characteristics of rectangular channels equipped with a flexible flag vortex generator (FFVGs) and a rigid flag vortex generator (RFVGs). The FFVGs and RFVGs are mounted at the entrance of the channel using four different obstacle geometries. The experiments were performed in a rectangular duct with FFVGs and RFVGs under four different Reynolds numbers (9965, 19,930, 29,985, and 34,875), four different obstacle geometries (triangle-shaped obstacle (T-SO), cylinder-shaped obstacle (C–SO), rectangular-shaped obstacle (R–SO) and half cylinder-shaped obstacle (HC–SO), four different FFVGs and RFVGs lengths (L) (50 mm, 100 mm, 150 mm, and 200 mm), four different FFVGs and RFVGs width (w) (10 mm, 20 mm, 30 mm, and 45 mm), and two different FFVGs and RFVGs channel height clearance (c) (1 mm, and 4 mm). To reduce the number of trials, the Taguchi technique was utilized, thereby reducing the number of trials from 1024 to 16. The highest thermal performance factor was determined as approximately 1.32 in Case 12, which was observed in Case 12 with, l*=0.36, w*=0.036, c*=0.014, Re = 34,875, FFVGs, and R–SO. The heat transfer results of the FFVGs and RPVGs were compared with those of a smooth plate. The best heat transfer performance was obtained with the FFVGs. The presence of the vortex generators produced higher heat transfer coefficients than the smooth plate surfaces.

Effect of pipe rotation on heat transfer to laminar non-Newtonian nanofluid flowing through a pipe: a CFD analysis

Abstract The present numerical study is aimed at investigating the effect of rotation on heat transfer to non-Newtonian nanofluid flowing through a pipe. Non-Newtonian fluid flow under laminar condition with heat transfer finds the applications in various industries like food processing, pharmaceutical and polymer etc. Various proportions (1–3%) of copper nanoparticles are mixed with water to study the heat transfer rates non-Newtonian nanofluid flowing through the rotating pipe. Effect of rotation rate on heat transfer rates are also studied. In this study for 1% nanofluid at a constant rotation rate of 0.8, the Nusselt number is increased by 119.45%. The highest thermal performance factor (TPF) is 1.74, observed at N = 0.8, Pe = 5000, and for 1% volume concentration of non-Newtonian nanofluid.

Effect of vibration on heat transfer to laminar non-Newtonian nanofluid flowing through a circular pipe: A numerical analysis

The present study is aimed at investigating the effect of vibration on heat transfer to non-Newtonian nanofluid under laminar condition flowing through a pipe. Various volume fractions of 0.5, 1.5 and 2.5% copper nanoparticles are mixed with water to study the heat transfer rates of nanofluid flowing through the vibrating pipe for Reynolds number varying from 50 to 1,000. Effect of frequencies from 20 to 40 Hz and amplitudes from 0.5 to 1 mm are also studied. The highest Thermal Performance Factor is 3.7 for Re = 100, F = 20 Hz, A = 1 mm and φ = 2.5%.

Thermal performance investigation of Therminol55/MWCNT+CuO nanofluid flow in a heat exchanger from an exergy and entropy approach

Nanofluids have been extensively studied in recent decades and have been regarded as “next-generation heat transfer fluids” due to their superior properties. However, dispersion stability and application at higher temperatures are among the challenges that must be overcome. In this work, a new class of stable hybrid nanofluid based on multi-walled carbon nanotube (MWCNT) + cupric oxide (CuO) nanocomposite is produced with Therminol55 (TH55) as the base fluid. Nanofluids' thermophysical characteristics are investigated at varying concentrations (0.005–0.08 wt%), and they are subsequently employed as the heat transfer medium in a tube heat exchanger (HEX) for the turbulent flow regime. Thermal conductivity was significantly increased by 128.4% at the maximum nanocomposite concentration of 0.08 wt%. Despite this, nanocomposites enhanced the nanofluids' viscosity, which climbed gradually with concentration to a maximum enhancement of around 25% at 0.08 wt%. The heat transfer performance of the formulated nanofluids was numerically assessed and found to be good; for example, when compared to pure TH55, the heat transfer coefficient improved by up to 128%. The highest increase in Nu was 38.4%, while the maximum increase in pumping power was determined to be 103.88%. Furthermore, the maximum exergy efficiency was 47.84% at a 0.08 wt% concentration and a Reynolds number (Re) of 12500, which is somewhat higher than the 40.96% attained with pure TH55. The highest thermal performance factor was 1.31 for 0.08 wt %, exceeding the maximum thermal performance factors of 1.17, 1.11, 1.08, and 1.03 for 0.04, 0.02, 0.01, and 0.005 wt %, respectively. Consequently, a nanofluid made of MWCNT + CuO/TH55 might be a promising candidate for usage as a heat transfer fluid.

A three-dimensional numerical study of the effects of various twisted tapes on heat transfer characteristics and flow field in a tube: Experimental validation and multi-objective optimization via response surface methodology

The main aims of the current three-dimensional numerical study are scrutinizing the effects of various twisted tapes on hydraulic-thermal performance and optimizing the geometrical parameters of a twisted tape geometry via response surface methodology. This study is carried out in three various phases. In the 1st phase, heat transfer characteristics of testing fluid through a tube which have a simple twisted tape is investigated. In this phase, numerical, experimental, and theoretical results are compared to each other. Then, the effects of different inserts on three key parameters, i.e., Nusselt (Nu) number, friction fraction (f), and thermal performance factor are investigated. After determining the superior twisted tape from the thermal performance factor aspect, in the final phase, an optimization study via response surface methodology is performed based on different objectives. According to the results, amidst the different inserts, the clockwise-counterclockwise and alternate axis twisted tapes ranked first from the highest thermal performance factor (1.46) and Nu number (34.27) standpoints, respectively. The lower friction fraction belonged to clockwise-counterclockwise type (f = 0.4068). The optimum value for twisted ratio, connection angle, and number of clockwise-counterclockwise strips, in order, is 3.02, 44.55°, and 1. Compared to tubes with and without simple insert, the Nu number increased by 46.2% and 221%, respectively, utilizing optimized clockwise-counterclockwise insert.

Inducing swirl flow inside the pipes of flat-plate solar collector by using multiple nozzles for enhancing thermal performance

In this numerical study, an attempt has been made to improve the thermal performance of the flat-plate solar collector (FPSC) by inducing the swirl flow inside the tube by the considered nozzles. To this end, the effect of the number of circumferential nozzles and their inclination angles was taken into the account. The considered number of nozzles was "single", ''dual'', ''triple'', and ''quad''. For each of the said cases, the inclination angle of nozzles was taken 30°, 45°, 60°, and 90° (A30, A45, A60, A90). Moreover, the mass flow rate of single-nozzle pipe was considered 0.2 kg/s, 1 kg/s, and 2 kg/s. To analyze all of the cases under identical conditions, the said mass flow rates were distributed equally among all of the nozzles (for ''dual'', ''triple'', and ''quad''). All of the characteristics were defined in a form of "A…-D…-N…-M…'' where ''A…'', "D…", "N…", and "M…" stand for angle of injection, diameter of pipe, nozzle cross-section edge, and mass flow rate, respectively. Numerical simulation (3-dimensional) of the system was performed by Finite Volume Method (FVM). The turbulence nature of flow was simulated by the k-omega SST (shear stress transport) turbulent model. Results showed that the "single-nozzle'' swirl generator had the highest thermal performance factor (TPF) so that for all cases its values were greater than unit. Mass flow rate growth increases Nu, heat extraction rate, and kinetic energy rate (KER) while drops friction factor and outlet temperature. Increment of injection angle increases outlet temperature and friction factor and reduces KER. The maximum and minimum values of TPF are 4.19 and 0.44 which belong to "single; A30-D50-N12.5-M0.2" and "quad; A90-D50-N12.5-M0.5", respectively.

Heat transfer enhancement of a double pipe heat exchanger by Co-Twisting oval pipes with unequal twist pitches

A double pipe heat exchanger composed of two co-twisting oval pipes with unequal twist pitches is proposed in this paper. The fluid flow and heat transfer characteristics are numerically studied for the twist pitch ratio of the outer to inner pipes ranging from 1.0 to 2.0 in the laminar regime. The results show that the heat transfer first increases and then decreases with the increase of twist pitch ratio. The corresponding increase in flow resistance is relatively less than the increase in heat transfer. The largest differences in Nusselt number and friction factor between different twist pitch ratios are 71.4% and 19.0%, respectively. The heat transfer enhancement is the largest when the twist pitch ratio is 1.5. The Nusselt number is enhanced by 97.0% with friction factor only increasing by 43.7% compared with the simple straight annular pipe. For the optimal twist pitch ratio 1.5 in terms of the best thermal performance, the highest thermal performance factor is 1.75 times as large as the simple straight annular pipe. Fitted correlations are also proposed with the deviations within ±12% for Nusselt number, ±6% for friction factor, and ±8% for thermal performance factor.

Impingement/effusion cooling with a hollow cylinder structure for additive manufacturing: Effect of channel gap height

The present study is to investigate the effect of gap height on heat/mass transfer for impingement/effusion cooling of gas turbine hot components, using a hollow cylinder structure created by three perforated plates with two channels. The detailed local heat/mass transfer coefficients on all surfaces of the structure are measured in the test section using a naphthalene sublimation method. Flow characteristics in the structure are revealed using a numerical simulation such as jet impingement, wall jets, and toroidal vortices. The hole spacing (P/D) and thickness of plate (t/D) in the present study are 6 and 1, respectively. The various gap height ratios, which mean the ratios between the gap height of the first channel and that of the second channel, are 1:4 (0.2D-0.8D), 1:1 (0.5D-0.5D), and 4:1 (0.8D-0.2D). Depending on the gap height ratios, heat/mass transfer distributions are obtained differently on each surface of the structure. The area-averaged Sherwood number on each surface shows a large variation ranging from 27% reduction in UM of the Case 3 and 42% increase in UB of the Case 3 with different gap heights at the Reynolds number (ReD) of 7,000. Considering the benefits of heat/mass transfer augmentation and the drawbacks associated with an increase in pressure drop, the structural configuration of the first channel of low gap height and the second channel of high gap height has the highest thermal performance factor, with an improvement of 4.8% at ReD = 7,000. The scale of gap height and wall thickness of the gas turbine hot components should be selected in terms of the total blade wall thickness, number of multi-layers, and manufacturing tolerance in additive manufacturing. Therefore, as gap height for the channel in the laminated structure is limited, the case of the gap height ratios of 1:4, which is the low gap height for the first channel and the high gap height for the second channel, offers the best cooling performance for gas turbine components compared to its counterpart having a high gap height of the first channel and a low gap height of the second channel.

Thermal Performance Assessment of a Tubular Heat Exchanger Fitted with Flower Baffles

This paper presents a numerical study of the hydrothermal air-side performance of a tubular heat exchanger fitted with flower baffles (FBs). The investigation was done by testing in-line and staggered FB arrangements for various baffles’ pitch ratios (, 1.5, 2, 2.5, and 3) with Reynolds number Re ranging from 3000 to 15,000. The results indicate that the use of the leads to stirring the stagnated zones downstream of the baffles, and improving the air mixture close to the tube walls, which, by consequence, presents an efficient solution to improve the thermal transfer coefficients. Also, the PR rise with a fixed blockage ratio of 0.5 leads to an increase of both the Nusselt number and friction factor values. The highest thermal performance factor η of 1.77 is achieved by using the in-line baffle arrangement at , , and . Finally, and for other useful applications, reliable correlations have been developed to predict Nusselt number and friction factor.

Numerical investigation of a novel jet hole design for staggered array jet impingement cooling on a semicircular concave surface

Staggered array jet impingement cooling (JIC) on a semi-circular concave surface has investigated numerically. The main objective of this work is to examine elongated jet holes on heat transfer and flow characteristics of the staggered array JIC and to elucidate its applicability on cooling of a turbine blade. Jet holes were elongated to the target surface by the nozzles. Numerical computations were performed with different jet Reynolds numbers (5000≤Re≤25000), normalized confinement plate-to-target plate distances (1.0≤H/d≤8.0) and jet nozzle-to-target plate gap (0.5≤G/d≤6.0). Average Nusselt (Nu) number, local Nu number distributions on the surface, flow characteristics and Thermal Performance Factor (TPF) were comprehensively investigated. Numerical results were compared with the normal staggered array JIC. Results showed that local Nu number and average Nu number increases with decreasing G/d. The highest enhancement of heat transfer using elongated jet hole is obtained as 20.16% by decreasing G/d to 0.5 at H/d = 8.0. However, highest TPF is estimated as 1.11 at H/d = 8.0 by G/d = 2.0 for Re = 25,000. Decreasing of G/d provides more uniform heat transfer on the surface of interest in comparison with normal staggered array JIC. Consequently, elongating jet hole is a feasible heat transfer enhancement design for the staggered array JIC on a semicircular concave surface.

Experimental heat transfer and flow simulations of rectangular channel with twisted-tape pin-fin array

In this study, an innovative twisted-tape pin-fin array was proposed for passive heat transfer enhancement (HTE) to improve the aerothermal performance of channel flows. The full-field Nusselt number distributions, Fanning friction coefficients and thermal performance factors of an improved channel were measured at Reynolds numbers of 5000, 7500, 10,000, 12,500, and 15,000. The turbulent channel flows were numerically explored using the ANSYS-Fluent code to perform correlative analysis between the aerothermal measurements and numerical flow results. A set of aerothermal data and numerical flow results was selected to illustrate the properties of HTE and the responsive flow mechanisms. Because of the vortical flows induced by each twisted tape in the array, the average measured Nusselt numbers and Fanning friction coefficients of the improved channel were 5.26–4.73 and 39.4–38.5 times higher than those of a plain tube, respectively; thus, the thermal performance factor (TPF) of the improved channel was 1.55–1.39 when 5000 <Re< 15,000. Compared with the pin-fin channels with different geometries reported in the literature, the twisted-tape pin-fin channel designed in this study provided a higher degree of HTE and thus a higher TPF at the same pressure drop penalty and pumping power. On the basis of the experimental results, two empirical correlations that were used to evaluate the average endwall Nusselt number and Fanning friction coefficient of the designed pin-fin channel were proposed for relevant applications.

Thermo-hydraulic performance of mesoporous silica with Cu nanoparticles in helically grooved tube

High-performance heat transfer fluids significantly affect the efficiency and overall performance of high heat flux systems. A novel nanocomposite containing mesoporous silica with high dispersity decorated with copper nanoparticles with a high thermal conductivity was synthesized. Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were conducted to characterize the synthesized nanocomposite. The present study investigated the thermal and hydraulic characteristics of hybrid nanofluids developed through dispersing the synthesized nanocomposite (Cu/SBA-15) in water in a helically-grooved tube. Changes in thermo-hydraulic characteristics by a Reynolds number of Re = 5000–12000 and the nanocomposite weight fraction concentration (deionized water, C = 0.012 wt%, 0.017 wt% and 0.023 wt%) were examined. Adding the nanocomposite to the base fluid with C = 0.023 wt% resulted in the maximum increase of 33.45% in heat transfer. The Nusselt number was found proportional to the Reynolds number and the nanocomposite weight fraction concentration. The highest thermal performance factor can be got when Re = 7780 and C = 0.023 wt%. The experimental results were employed to propose an experimental correlation for predicting the thermal performance factor, friction factor, viscosity and the Nusselt number of the hybrid nanofluid.

Experimental and numerical investigation of swirling turbulent flow and heat transfer due to insertion of twisted tapes of new models in a heated tube

In this work, the effects of new tapered configurations of twisted tape on thermal and hydrodynamic fields in a heated tube were studied experimentally and numerically to determine the best configuration that provides the highest thermal performance factor. The tube surface was under constant heat flux and air was chosen as the working fluid, with a turbulent flow of 10,000 ≤ Re ≤ 40,000. The RNG k-ε turbulent model was used in the numerical part. For the first time, the tapered region was varied in its length (l) and starting width (SW), which represents the novelty of this work. The maximum increase recorded in the experimental and numerical results was 75% and 100% respectively for the Nusselt number, and 220% and 226% respectively for the friction factor. Similarly, the maximum experimental and numerical thermal performance factor was 1.19 and 1.37, respectively. Subsequently, the experimental data obtained for the Nusselt number, friction factor, and thermal performance factor were described using empirical correlations.

Modeling of heat transfer performance of carbon nanotube nanofluid in a tube with fixed wall temperature by using ANN–GA

In this research, the heat transfer performance of carbon nanotube (CNT)/water nanofluid in a horizontal tube with a fixed wall temperature with a turbulent regime flow condition is experimentally analyzed. The heat transfer performance is monitored through an evaluation of the heat transfer coefficient and friction factor. To perform this investigation, the affecting performance variables of nanofluid such as volume concentration, twist ratio, and Reynolds number are defined and considered within certain ranges of 0.2–1.2%, 2–8, and 4000–20,000, respectively. It is monitored that insertion of nanoparticles of CNT increases the heat transfer coefficient in comparison with the water and its value is also boosted in higher concentrations and Reynolds number. It is found that simultaneous utilization of nanofluids and twisted tape influences the heat transfer more efficient than employing either nanofluid or twisted tape, individually. In overall, under the designed circumstances, the highest thermal performance factor is obtained at CNT concentration of 1.2% and twist ratio of 2.

Heat transfer and flow characteristics in a sinusoidally curved converging-diverging channel

The objective of this work is to present the thermal performance characteristics and to examine the hydrodynamic structure of the fluid which improves the rate of heat transfer in parallel with the penalty of pressure drop by means of the time-averaged streamlines topology, <Ψ>, streamwise velocity distribution, <u>, vorticity concentration, <ω> and turbulent Reynolds stress, u'v'‾/U2 for the sinusoidal wavy channel. A wide range of experiments were performed for Reynolds numbers, Re ranging from 4 × 103 to 1 × 104 in order to determine the heat transfer rate and the friction factor, f with varying the channel height expansion/contraction ratio, M = Hmin/Hmax such as 0.5, 0.35 and 0.28. The results revealed that a significant heat transfer enhancement was achieved with a considerable penalty of pressure drop. The highest thermal performance factor, TPF was obtained as 1.46 for M = 0.5. Numerical simulations were conducted to confirm the experimental results for the same parameters. The Shear Stress Transport k-w (SST k-w) turbulence model was used to perform numerical analyses. After ensuring the consistency of experimental thermal performance results with numerical predictions, the Particle image velocimetry (PIV) system was utilized for investigating the flow physics in the sinusoidally curved converging-diverging channel for all M values at Re = 4 × 103 where the TPF is maximum.

Numerical study on heat transfer enhancement and flow characteristics of double pipe heat exchanger fitted with rectangular cut twisted tape

In the present study, the heat transfer, friction factor and thermal performance factor of rectangular cut twisted tape (RCT) that are inserted in inner tube side of a double pipe heat exchanger (DPHE) are numerically examined. The obtained results have been compared with the performance of heat exchangers, which are equipped/unequipped by typical twisted tape (TT). The RCTs have constant twist ratio (Y = 3.0) and are used in different cut depth ratios (DR = 0.15, 0.24 and 0.33) and cut width ratios (WR = 0.15, 0.24 and 0.33). The investigated Reynolds number range is from 6000 to 18,000 and the working fluid is considered to be water. Hot water with a variable mass flow rate is flowing through the inner pipe but cold water has counter flow through annulus side with constant mass flow rate. For the selection of the turbulence model and validation, the obtained numerical results for plain double pipe heat exchanger (P-DPHE) and heat exchanger with TT are compared with empirical correlations. Then the more accurate model was used to simulate the RCTs cases. Comparing the simulation results for RCTs and TT, it was determined that Nusselt number, friction factor and thermal performance factor will have higher value when using RCTs. This behavior is directly and inversely proportional to the DR and WR respectively. In this study, the highest thermal performance factor is about 1.46 which is obtained for RCTs in DR = 0.33 and WR = 0.15 conditions. In addition, new empirical correlations have been offered for calculating a Nusselt number and friction factor for inserted rectangular cut twisted tape in a tube.