Experimental Analysis of Heat Transfer on the Tubular Tube Heater with a Variable of Twisted Tape Inserts and Wire Coil to Prevent the Icing Contaminated Tailplane Stall

An anti-icing system has the purpose of protecting the leading edge of the tailplane from contamination during aircraft flight. An anti-icing system in a turboprop aircraft employs heaters that use electrical energy as their power source or heat generated by the bleed air. Protecting the tailplane from contamination is preventing the aircraft stall from occurring that triggers dangerous flight conditions. The aluminum prototype tailplane is assembled with a variable of twisted tape insert and wire coil. The twisted tape insert comes in three different geometries with twist ratio T3 = 9.3; T4 = 7; and T5 = 5.6, as well as a wire coil with fixed geometry. This study shows the best heat transfer rate occurs in T3 with a value of 33.90 W. The consequence of this condition is an decrease in pressure drop that occurs. Twisted 3 has the greatest pressure drop when compared to other geometry, with an average value of 4.72 Pa.

Pool boiling heat transfer enhancement by using perforated twisted tape fins

The application of twisted tape fins showed a considerable enhancement in pool boiling heat flux. The present study experimentally investigates the effect of solid and perforated twisted tape fins on pool boiling of water by varying the twist ratio (y) and perforation index (PI) from 3 - 4.3 and 5 - 10, respectively. An arrangement of five twisted tape fins with twist ratio of 3 showed 18.6% enhancement as compared to the plain surface whereas an arrangement of five perforated twisted tape fins having perforation index (PI) of 7 and twist ratio of 3 showed a maximum enhancement of 28.7%.

Influence of twisted tape fins on heat transfer and friction factor characteristics for impinging jet solar air heater

In this work, an experimental study was carried out to investigate the enhancement of heat transfer and friction factor characteristics of an impinging jet solar air heater integrated with twisted tape fins. During the analysis, the Reynolds number fin design parameters namely twist ratio (Y), and pitch ratio (py) are varied from 3500 –13500, 5.5–9.5, and 0.1–0.3, respectively. During the experimentation, the constant heat flux of 1000 W/m2 was maintained on the absorber plate. From the results, it was observed that the heat transfer rate increases while increasing the twist ratio up to 7.5 and further increase in twist ratio diminishes the performance. It was also concluded that the rise in pitch ratio (py) deteriorates the rate of heat transfer. The present work enhances the heat transfer and friction factor by the maximum of 1.9 and 1.81 times as compared with the conventional jet impingement solar air heater at identical operating conditions.

Experimental and numerical thermal performance analysis with exergy destruction on nanofluid flow in tube with double strip helical screw inserts

Experimental and numerical analysis is arranged with exergy destruction to evaluate thermal performance of system on nanofluid flow in tube with single and double strip helical screw inserts at different values of twist ratio in laminar flow regime. CFD analysis has occurred on the fluent workbench of ANSYS software. The Nusselt number attained enhancement with the flow of nanofluid in double strip helical screw inserts as compared with single strip helical screw inserts at decreasing values of twist ratio and increasing values of Reynolds number. Maximum enhancement of 421% is found with Nusselt number in the flow of nanofluid in tube with double strip helical screw insert at 1.5 of twist ratio and lower value of Reynolds number as compared with the flow of water in plain tube. Common correlations of Nusselt number and friction factor are generated. Exergy destruction number is attained less than one value for both types of inserts at different values of twist ratio and Reynolds number, whereas attained lower value with the flow of nanofluid in tube with double strip helical screw insert at twist ratio of 1.5 and low value of Reynolds number. Heat transfer enhancement number is attained more than one value for both types of inserts with different values of twist ratio and Reynolds number, whereas double strip helical screw inserts attained maximum value at twist ratio of 1.5 in the range of Reynolds number. Therefore, double strip helical screw inserts are the best inserts as compared with single strip helical screw inserts to compact the size of heat exchangers, whereby size of many thermal applications could be compact such as solar water heater, electronic cooling devices, automobile radiator, power plants etc.

Evidence for abnormal deformational reserve in hypertrophic obstructive cardiomyopathy on exercise: is this a true fingerprint?

Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by muscle hypertrophy and fibrosis, interfering with force generation and relaxation. Abnormal ventricular (LV) myocardial deformation have been demonstrated in patients with HOCM at rest, but there is lack of data regarding the deformational mechanics in exercise in obstructive HCM. Aims To assess the adaptability of LV deformational behaviour to physical exercise in HOCM patients as compared to healthy controls and to examine if Deformational Imaging (DMI) can provide additional information. Methods 28 obstructive HOCM (age 51.2±14.2yrs; 16 men, LVOT-obstruction 56±19mmHg at rest or on Valsalva maneuver) and 32 control subjects (50.9±6.8 yrs, 19 men from the MAGYAR-PATH Registry) underwent bicycle stress Echo (ESE) with full conventional 2D- and Doppler TTE, 2D- and 3D-Speckle Tracking Analysis (DMI) and 3D-Full Volume assessment both at rest and on submaximal ESE. Results At rest, the HOCM group had lower GLS (−14.6±4.5 vs 18.4±2.6%, p<0.01) but higher CS (−32.9±5.1 vs 28.8±2.3%) and Twist (9.9±2.6 vs 6.1±2.2°) than in control subjects. Exercise induced an increase in all strains in control subjects but less in HOCM (GLS: −21.4±3.5 vs 15.1±3.0% and CS: −33.9±3.6 vs 34.1±4.2% in controls). The increase of LV twist was blunted in HOCM (Δ1.2 vs Δ3.6° in controls). The PSS was more pronounced in HOCM on ESE (46.6±12.0 vs 21.2±9.6%, AUC: 0.71 for predicting HOCM), the UTR was slower (118±2.1 vs 133.1±14.1°/s) and occurred later in HOCM. The MD of Strain increased in HOCM on ESE (Δ85.1 vs Δ8.1ms in controls). The Twist had positive correlation with LVOT-obstruction (R2=0.54, p<0.01) and inverse correlation with UTR (R2=−0.72, p<0.02). The UTR/Twist ratio diminished only in HOCM on exercise (−6.0±0.8 vs −13.1±2.5 1/s). The MD, the PSS on ESE and the UTR/Twist ratio predicted the HOCM deformation phenotype accurately (AUC: 0.72, cut-off 6.0 1/s). Conclusions The HOCM patients had attenuated Strain and Rotational response on exercise implying impaired deformational adaptability with post-systolic shortening and pronounced mechanical dispersion of peak Strain on exercise which was more accurate to identify the HOCM phenotype than other Echo-indices. These findings support evidence for reduced systolic-diastolic coupling efficiency in HOCM patients on exercise which can contribute to the development of exercise-related breathlessness, dynamic LVOT-obstruction and arrhythmias in patients with HOCM. These distinct deformational patterns on exercise can help in the differential diagnosis of patients with LV hypertrophy of unknown aetiology with good sensitivity and specificity and can also aid in the risk stratification workup in HOCM. DMI Predictors for HOCM Funding Acknowledgement Type of funding source: Public hospital(s). Main funding source(s): Milton Keynes University Hospital Research Founding

Review on Heat Transfer Enhancement by Insert Devices

The scientists revise the heat transfer enhancement techniques time to time to achieve better performance and to obtain optimized designs of heat exchangers. The present study reviews the performance and techniques of heat transfer enhancement using various insert devices such as twisted tape and wire coil insert as well as completely different forms of other inserts like air-foil shape inserts, X-shaped twisted tape inserts, baffles and V-winglets inserts with various types of medium and nanofluids. According to the summary of recent significant researches on the heat transfer enhancement by using different types of inserts and combinations of these inserts with various nanofluids showed that insert can indicatively enhance the heat transfer rate by modifying its geometry or configurations like twist ratio, length ratio, pitch ratio, segmented tape, perforated tape, angle of arrangements and insert quantities and so on which caused a considerable impact on performance characteristics of heat transfer enhancement along with the pressure drop and friction factor. It is revealed through reviewing the related literature that the highest value of equivalence heat transfer enhancement is as maximum as 400%, 300% and 9% for the twisted tape insert with helical tube, the air foil shaped inserts and for the wire coil inserts, respectively when compared with the smooth tube. In the case of baffles in nanofluids, as maximum as 255% equivalence heat transfer enhancement could be achieved when compared with that of baffles without nanofluids.

CFD Analysis of Twisted Tape Heat Exchanger with Twist Ratio of 3 in Metallic and Ceramic Nano Fluids

The heat transfer enhancement is primary objective in the heat exchangers. The heat exchangers are employed for cooling, heating and evaporation purposes in the industries. Many of the heat exchangers designed as the heat transfer fluid flow inside the tube. So, in this research, the double tube heat exchanger is considered with unit length. The passive method is one in which the flow resistance is to be introduced to enhance the heat transfer rate without affecting the pumping force. So, the tube inserts with twist ratio of 3 is considered. The water and water-copper oxide nano fluid and water-silicon dioxide nano fluid were considered for investigation. The flow properties such as pressure, temperature, velocity and turbulence kinetic energy were varied and discussed. The thermal performance, friction factor and enhancement factors are compared and discussed. The SiO2-water nano fluid has outperformed than the other fluids studied.

Effect of Conical Strip Inserts and ZrO2/DI-Water Nanofluid on Heat Transfer Augmentation: An Experimental Study

There is a significant enhancement of the heat transfer rate with the usage of nanofluid. This article describes a study of the combination of using nanofluid with inserts, which has proved itself in attaining higher benefits in a heat exchanger, such as the radiator in automobiles, industries, etc. Nanofluids are emerging as alternative fluids for heat transfer applications due to enhanced thermal properties. In this paper, the thermal hydraulic performance of ZrO2, awater-based nanofluid with various volume concentrations of 0.1%, 0.25%, and 0.5%, and staggered conical strip inserts with three different twist ratios of 2.5, 3.5, and 4.5 in forward and backward flow patterns were experimentally tested under a fully developed laminar flow regime of 0–50 lphthrough a horizontal test pipe section with a length of 1 m with a constant wall heat flux of 280 W as the input boundary condition. The temperatures at equidistant position and across the test section were measured using K-type thermocouples. The pressure drop across the test section was measured using a U-tube manometer. The observed results showed that the use of staggered conical strip inserts improved the heat transfer rates up to that of 130.5%, 102.7%, and 64.52% in the forward arrangement, and similarly 145.03%, 116.57%, and 80.92% in the backward arrangement with the twist ratios of 2.5, 3.5, and 4.5 at the 0.5% volume concentration of ZrO2 nanofluid. It was also seen that the improvement in heat transfer was comparatively lower for the other two volume concentrations considered in this study. The twist ratio generates more swirl flow, disrupting the thermal hydraulic boundary layer. Nanofluids with a higher volume concentration lead to higher heat transfer due to higher effective thermal conductivity of the prepared nanofluid. The thermal performance factor (TPF) with conical strip inserts at all volume concentrations of nanofluids was perceived as greater than 1. A sizable thermal performance ratio of 1.62 was obtained for the backward-arranged conical strip insert with 2.5 as the twist ratio and a volume concentration of 0.5% ZrO2/deionized water nanofluid. Correlations were developed for the Nusselt number and friction factor based on the obtained experimental data with the help of regression analysis.

Thermal Performance With Entropy Generation Analysis of Fluid Flow in a Heat Exchanger Pipe With Single and Double Strip Helical Screw Tape Inserts

In heat exchangers, twisted tape insert is a technique to enhance heat transfer. In this paper, the experimental investigation is arranged to analyse thermal performance and entropy generation analysis on fluid flow in helical screw inserts with number of strips. The Nusselt number is achieved enhancement with double strip as compared to single strip helical screw inserts at decreased values of twist ratio and increased values of flow rates. The Nusselt number is achieved maximum enhancement of 112% with double strip helical screw insert than plain tube at 4000 of Reynolds number, whereas it is found higher value at Reynolds number of 16000. The common correlations of Nusselt number and friction factor with repect of Reynolds number, number of the strips and twist ratio are generated. The entropy generation analysis is also performed. The thermal performance factor is found increment with double strip than single strip helical screw inserts at twist ratio of 2.5 and 3, whereas, it is attained maximum value of 1.5 at twist ratio 2.5 and Reynolds number of 16000 with double strip helical screw insert. The double strip helical screw inserts are suitable for reducing the size of heat exchanger, which could dercrease the size of many thermal applications as solar water heater, radiator, electronic cooling systems.