Enhancement and Prediction of Heat Transfer Rate in Turbulent Flow Through Tube With Perforated Twisted Tape Inserts: A New Correlation

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
J. U. Ahamed ◽  
M. A. Wazed ◽  
S. Ahmed ◽  
Y. Nukman ◽  
T. M. Y. S. Tuan Ya ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Circular Tube ◽  
Twisted Tape ◽  
Pumping Power ◽  
Plain Tube ◽  
Flow Through

An experimental investigation has been carried out for turbulent flow in a tube with perforated twisted tape inserts. The mild steel twisted tape inserts with circular holes of different diameters (i.e., perforation) are used in the flow field. An intensive laboratory study is conducted for heat transfer and pressure drop characteristics in the tubes for turbulent flow with various airflow rates. Heat transfer and pressure drop data are engendered for a wide range Reynolds number (1.3×104–5.2×104). Tube wall temperature, pressure drop, air velocity, and its temperature are measured both for plain tube and for tube with perforated twisted tape inserts. Heat transfer coefficients, Nusselt number, pumping power, and heat transfer effectiveness are calculated for both cases. Experimental results showed that perforated twisted inserts of different geometry in a circular tube enhanced the heat transfer rate with an increase in friction factor and pumping power for turbulent flow. The pumping power, heat transfer coefficient, and effectiveness in the tube with the twisted tape inserts are found to increase up to 1.8, 5.5, and 4.0 times of those for the plain tube for same Reynolds number, respectively. Finally, a correlation is developed for prediction of the heat transfer rate for turbulent flow through a circular tube with perforated twisted tape inserts.

Convective Heat Transfer and Pumping Power Requirement Using Nanofluid for the Flow Through Corrugated Channel

2015 ◽  
Author(s):  
Shafi Noor ◽  
M. Monjurul Ehsan ◽  
M. S. Mayeed ◽  
A. K. M. Sadrul Islam
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Pumping Power ◽  
Power Requirement ◽  
Corrugated Channel ◽  
Flow Through

Convective heat transfer rate for turbulent flow using nanofluid through both plain and corrugated channel has been investigated numerically in the present study. Three different types of nanofluids namely Al2O3-water, TiO2-water and CuO-water of different volume fractions (1%, 2%, 3%, 4% and 5%), are used as the working fluid flowing through the channel. The corrugated channels have wall geometries of trapezoidal shape of different amplitude-wavelength ratios. Grid independence study was carried out for all the geometries. The obtained results in case of base fluid-water flowing through parallel plate channel have been validated with well-established correlations. The study has been conducted by finite volume method to solve the transport equation for the momentum, energy and turbulence quantities using single phase model of the nanofluids where the thermophysical properties of the nanofluids are calculated by using different correlations from the literature. In this study, the heat transfer enhancement using nanofluids compared to that using base fluid-water is presented for a range of Reynolds number- 15000 to 40000. The pumping power required for the flow through the channels increases with the increase in the viscosity of the fluid which justifies the increase in pumping power requirement in case of nanofluids compared to that with water. While using corrugation at the wall of the channels, in addition to the enhancement in the convective heat transfer rate, there is an increase in the pumping power requirement for the same Reynolds number. However, for a given requirement of heat transfer rate, the required pumping power can be reduced by using nanofluids. This study includes the trend and limit of volume fraction of nanofluid during this pumping power reduction phenomenon. The results show that with the increase in the volume fraction of the nanofluids, the convective heat transfer rate increases which is same for all the geometries of the fluid domain. Addition of nanofluid reduces the pumping power requirement for a constant heat transfer rate. The volume fraction of the nanofluids with which the maximum reduction of pumping power takes place at the optimum working condition is also found in the present study. This study draws a comparison among three different nanofluids in terms of the enhancement in the convective heat transfer rate and corresponding pumping power requirement for the flow through the trapezoidal shaped corrugated channel of various amplitude-wavelength ratios in order to find out the best nanofluids for its optimum results within a specified range of working conditions.

scholarly journals Enhancement of Heat Transfer in a Rouletted Copper Tube Employing Delta Winglet Twirled Type Insert

2018 ◽  
Vol 3 (5) ◽  
pp. 47
Author(s):  
Mohammad Taukir Hossain ◽  
Nesar Ali ◽  
Muhammad Sadekul Karim
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Copper Tube ◽  
Twisted Tape ◽  
Enhancement Of Heat Transfer ◽  
Plain Tube ◽  
Wire Coil ◽  
Delta Winglet ◽  
Pitch Length

Heat transfer is a process or a system of thermal engineering that concerns the generation, use, conversion, transfer, internal or external molecular formation and exchange of thermal energy (heat) between physical systems. The research work has been experimented for the turbulent flow heat transfer in a tube having delta winglet twisted tape and then separately with water as working fluid. The test section consisted of a circular copper tube of 26.6 mm inner diameter, 900 mm length with five K-type thermocouples. Bulk temperature and pressure drops have been measured. Material of both the delta winglet twisted tape insert was stainless steel. Delta winglet twisted tape insert had a length of 795mm, width of 20mm, thickness of 2mm, pitch length of 120mm, twist ratio of 6 while wire coil insert had the same length as that of delta winglet twisted tape insert, wire diameter of 1mm, mean coil diameter of 22mm and pitch length of 30mm. Heat transfer rate, convective heat transfer coefficient, Nusselt’s number, friction factor and heat transfer efficiency have been calculated to analyze heat transfer performance of circular copper tube fitted with or without inserts in turbulent regimes (4000<Re<15000). Nusselt’s numbers for combination of delta winglet twisted tape and wire coil insert, wire coil insert only, delta winglet twisted tape insert only increased by 1.29 to 1.47, 1.19 to 1.34 and 1.10 to 1.15 times respectively than the plain tube. They increased by 17.95% to 27.61%, 15.97% to 20.20%, 8.90% to 12.02% and average of 21.65%, 17.44%, 8.95% respectively than the plain tube. Heat transfer rates also increased by 1.12 to 1.20, 1.06 to 1.09 and 1.03 to 1.05 times respectively compared to the plain tube. Heat transfer efficiencies increased by 1.36% to 1.62%, 1.24% to 1.47% and 1.14% to 1.34% respectively compared to the plain tube. Friction factors increased by 1.44 to 1.62, 1.34 to 1.43, 1.22 to 1.27 times respectively compared to the plain tube. The delta winglet twisted tape was the best arrangement for the enhancement of heat transfer rate as compared to the other inserts.

scholarly journals PERFORMANCE ENHANCEMENT FOR ROTARY AIR PREHEATER OF A THERMAL POWER PLANT

2020 ◽  
Vol 24 (06) ◽  
pp. 57-67
Author(s):  
Sinan Mazin Hazim ◽  
◽  
Mohammed H. Alhamdo ◽  
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Power Plant ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Thermal Power Plant ◽  
Transfer Rate ◽  
Thermal Power ◽  
Pumping Power ◽  
Air Preheater

The corrosion phenomenon is considered the main problems for air preheater in thermal power plant. The boiler flue gas contamination leads to decrease the air preheater performance and increases the maintenance cost, which causes the degradation of the cold end heating elements and thus leads to decrease the heat recovery rate. In this study, an experimental investigation was done for the transient thermal behavior and the pressure drop of the standard regenerative air preheater (Pmatrix) model, evaluating the performance factor, then modifying the air preheater (P+CG) model by changing the plates at the cold end last basket to the coarse gravel media. Since the gravel media have low thermal conductivity and predicted to give a high pressure drop, a new technique was done for the modified air preheater to compensate the low heat transfer rates and reduce the pressure drop in the gravel media by inserting bypass tubes at ratios (i and s), Which, the (i) model represents the inner aperture of tubes for the hot baskets facing to the inner aperture of tubes for the cold basket. While (s) model the insertion the tubes of the hot baskets as a staggered distribution with the tubes for the cold basket. The experimental investigation was carried out for the Reynolds number based on the test duct hydraulic diameter at a range of 24500<Re < 98000 for each charge and discharge periods. The experimental results are presented in terms of the average heat transfer rate and the pumping power for matrix models. The experimental measured results corroborated that the bypass tubes have a significant impact on improving the heat transfer rate and the pressure drop reduction of the modified air preheater matrix. The results showed that the best performance factor was achieved in the air preheater (P+CG+Ts) model which found to be in the range of 0.7-0.31 at high and low Reynolds. However, this improvement increased the pumping power by 13% than the (Pmatrix) model.

HEAT TRANSFER AND PRESSURE DROP IN TURBULENT FLOW THROUGH A TUBE WITH LONGITUDINAL PERFORATED STAR-SHAPED INSERTS

2011 ◽  
Vol 18 (6) ◽  
pp. 491-502 ◽  
Author(s):  
Andrew Mintu Sarkar ◽  
M. A. Rashid Sarkar ◽  
Mohammad Abdul Majid
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Flow Through

Thermal Performance Assessment of Turbulent Flow Through Dimpled Tubes

2010 ◽  
Author(s):  
Pornchai Nivesrangsan ◽  
Somsak Pethkool ◽  
Kwanchai Nanan ◽  
Monsak Pimsarn ◽  
Smith Eiamsa-ard
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Staggered Arrangement ◽  
Plain Tube ◽  
Pitch Ratio ◽  
Surface Patterns

This paper presents the heat transfer augmentation and friction factor characteristics by means of dimpled tubes. The experiments were conducted using the dimpled tubes with two different dimpled-surface patterns including aligned arrangement (A-A) and staggered arrangement (S-A), each with two pitch ratios (PR = p/Di = 0.6 and 1.0), for Reynolds number ranging from 9800 to 67,000. The experimental results achieved from the dimpled tubes are compared with those obtained from the plain tube. Evidently, the dimpled tubes with both arrangements offer higher heat transfer rates compared to the plain tube and the dimpled tube with staggered arrangement shows an advantage on the basis of heat transfer enhancement over the dimpled tube with aligned arrangement. The increase in heat transfer rate with reducing pitch ratio is due to the higher turbulent intensity imparted to the flow between the dimple surfaces. The mean heat transfer rate offered by the dimpled tube with staggered arrangement (S-A) at the lowest pitch ratio (PR = 0.6), is higher than those provided by the plain tube and the dimpled tube with aligned arrangement (A-A) at the same PR by around 127% and 8%, respectively. The empirical correlations developed in terms of pitch ratio (PR), Prandtl number (Pr) and Reynolds number, are fitted the experimental data within ±8% and ±2% for Nusselt number (Nu) and friction factor (f), respectively. In addition, the thermal performance factors under an equal pumping power constraint of the dimple tubes for both dimpled-surface arrangements are also determined.

Pressure Drop and Heat Transfer Characteristics of Louvered Fin Heat Exchangers

2013 ◽  
Vol 465-466 ◽  
pp. 500-504 ◽  
Author(s):  
Shahrin Hisham Amirnordin ◽  
Hissein Didane Djamal ◽  
Mohd Norani Mansor ◽  
Amir Khalid ◽  
Md Seri Suzairin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Considerable Effect ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Louvered Fin

This paper presents the effect of the changes in fin geometry on pressure drop and heat transfer characteristics of louvered fin heat exchanger numerically. Three dimensional simulation using ANSYS Fluent have been conducted for six different configurations at Reynolds number ranging from 200 to 1000 based on louver pitch. The performance of this system has been evaluated by calculating pressure drop and heat transfer coefficient. The result shows that, the fin pitch and the louver pitch have a very considerable effect on pressure drop as well as heat transfer rate. It is observed that increasing the fin pitch will relatively result in an increase in heat transfer rate but at the same time, the pressure drop will decrease. On the other hand, low pressure drop and low heat transfer rate will be obtained when the louver pitch is increased. Final result shows a good agreement between experimental and numerical results of the louvered fin which is about 12%. This indicates the capability of louvered fin in enhancing the performance of heat exchangers.

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