scholarly journals Experimental investigation on heat transfer and pressure drop of conical coil heat exchanger

2016 ◽  
Vol 20 (6) ◽  
pp. 2087-2099 ◽  
Author(s):  
Pramod Purandare ◽  
Mandar Lele ◽  
Raj Gupta
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Flow Rate ◽  
Cone Angle ◽  
Tube Diameter ◽  
Flow Rates ◽  
Side Flow ◽  
Coil Heat

The heat transfer and pressure drop analysis of conical coil heat exchanger with various tube diameters, fluid flow rates, and cone angles is presented in this paper. Fifteen coils of cone angles 180? (horizontal spiral), 135?, 90?, 45?, and 0? (vertical helical) are fabricated and analysed with, same average coil diameter, and tube length, with three different tube diameters. The experimentation is carried out with hot and cold water of flow rate 10 to 100 L per hour (Reynolds range 500 to 5000), and 30 to 90 L per hour, respectively. The temperatures and pressure drop across the heat exchanger are recorded at different mass flow rates of cold and hot fluid. The various parameters: heat transfer coefficient, Nusselt number, effectiveness, and friction factor, are estimated using the temperature, mass flow rate, and pressure drop across the heat exchanger. The analysis indicates that, Nusselt number and friction factor are function of flow rate, tube diameter, cone angle, and curvature ratio. Increase in tube side flow rate increases Nusselt number, whereas it reduces with increase in shell side flow rate. Increase in cone angle and tube diameter, reduces Nusselt number. The effects of cone angle, tube diameter, and fluid flow rates on heat transfer and pressure drop characteristics are detailed in this paper. The empirical correlations are proposed to bring out the physics of the thermal aspects of the conical coil heat exchangers.

A Variable-Curvature Spiral-Coil Heat Exchanger for Automobile Exhaust Heat Recovery

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Yu Zhu ◽  
Fengye Yang ◽  
Yueguang Guo
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Recovery ◽  
Heat Transfer Performance ◽  
Cone Angle ◽  
Spiral Coil ◽  
Variable Curvature ◽  
Exhaust Heat ◽  
Coil Heat Exchanger ◽  
Coil Heat

Abstract To improve the fuel efficiency of automobile engines and reduce pollution owing to automobile exhaust, this study discusses a fixed-curvature spiral-coil heat exchanger that recovers exhaust heat. Herein, the heat transfer performance of the spiral coil is studied via experimental testing and numerical simulation. In this study, a new type of variable-curvature spiral coil is designed to improve the efficiency of the heat exchanger. The effect of different conical angles on the resistance and heat transfer performance of the spiral coil within a range of Reynolds numbers of 4000–14,000 was analyzed. The heat exchange efficiency is a combination of the convective heat transfer and the overall heat recovery. The results of this study indicate that for a spiral-coil tube of length L, increasing the cone angle improves the convective heat transfer outside the tube. However, as the flow resistance increases, the exhaust heat recovery of a variable-curvature spiral-coil heat exchanger (VSE) is up to 18.8% higher than that of a constant curvature spiral-coil heat exchanger. The combined performance of VSE is excellent when the cone angle is 15 deg.

Experimental Investigation of Coil Curvature Effect on Heat Transfer and Pressure Drop Characteristics of Shell and Coil Heat Exchanger

2014 ◽  
Vol 7 (1) ◽  
Author(s):  
M. R. Salem ◽  
K. M. Elshazly ◽  
R. Y. Sakr ◽  
R. K. Ali
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Average Nusselt Number ◽  
Transfer Coefficients ◽  
Nusselt Numbers ◽  
Fanning Friction Factor ◽  
Coil Heat

The present work experimentally investigates the characteristics of convective heat transfer in horizontal shell and coil heat exchangers in addition to friction factor for fully developed flow through the helically coiled tube (HCT). The majority of previous studies were performed on HCTs with isothermal and isoflux boundary conditions or shell and coil heat exchangers with small ranges of HCT configurations and fluid operating conditions. Here, five heat exchangers of counter-flow configuration were constructed with different HCT-curvature ratios (δ) and tested at different mass flow rates and inlet temperatures of the two sides of the heat exchangers. Totally, 295 test runs were performed from which the HCT-side and shell-side heat transfer coefficients were calculated. Results showed that the average Nusselt numbers of the two sides of the heat exchangers and the overall heat transfer coefficients increased by increasing coil curvature ratio. The average increase in the average Nusselt number is of 160.3–80.6% for the HCT side and of 224.3–92.6% for the shell side when δ increases from 0.0392 to 0.1194 within the investigated ranges of different parameters. Also, for the same flow rate in both heat exchanger sides, the effect of coil pitch and number of turns with the same coil torsion and tube length is remarkable on shell average Nusselt number while it is insignificant on HCT-average Nusselt number. In addition, a significant increase of 33.2–7.7% is obtained in the HCT-Fanning friction factor (fc) when δ increases from 0.0392 to 0.1194. Correlations for the average Nusselt numbers for both heat exchanger sides and the HCT Fanning friction factor as a function of the investigated parameters are obtained.

scholarly journals Experimental Study on the Heat Transfer Characteristics of the Enhanced Fin-Tube Heat Exchanger Applied a Coiled Turbulator

2017 ◽  
Author(s):  
Sun-Joon Byun ◽  
Sang-Jae Lee ◽  
Jae-Min Cha ◽  
Zhen-Huan Wang ◽  
Young-Chul Kwon
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Water Flow ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Water Flow Rate ◽  
Transfer Performance ◽  
Tube Heat Exchanger ◽  
Fin Tube

This study presents the comparison of heat transfer capacity and pressure drop characteristics between a basic fin-tube heat exchanger and a modified heat exchanger with the structural change of branch tubes and coiled turbulators. All experiments were carried out using an air-enthalpy type calorimeter based on the method described in ASHRAE standards, under heat exchanger experimental conditions. 14 different kinds of heat exchangers were used for the experiment. Cooling and heating capacities of the turbulator heat exchanger were excellent, compared to the basic one. As the insertion ratio of the coiled turbulator and the number of row increased, the heat transfer performance increased. However, the capacity per unit area was more effective in 4 rows than 6 rows, and the cooling performance of the 6 row turbulator heat exchanger (100% turbulator insert ratio) was down to about 6% than that of 4 row one. As the water flow rate and the turbulator insertion ratio increased, the pressure drop of the water side increased. This trend was more pronounced in 6 rows. In the cooling condition, the pressure drop on the air side was slightly increased due to the generation of condensed water, but was insignificant under the heating condition. The power consumption of the pump was more affected by the water flow rate than the coiled turbulator. The equivalent hydraulic diameter of a tube by the turbulator was reduced and then the heat transfer performance was improved. Thus, the tube diameter was smaller, the heat flux was better.

Passive Heat Transfer Enhancement in Microchannels Using Wall Features

2007 ◽  
Author(s):  
Ravi Arora ◽  
Anna Lee Tonkovich ◽  
Mike J. Lamont ◽  
Thomas Yuschak ◽  
Laura Silva
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Flow Rate ◽  
Transfer Rate ◽  
Transfer Enhancement ◽  
Flow Rates ◽  
Feature Design

The two important considerations in the design of a heat exchanger are — the total heat transfer rate and the allowable pressure drop. The allowable pressure drop defines the maximum flow rate through a single microchannel and economics drives the design towards this flow rate. Typically the flow rate in the microchannel is in laminar flow regime (Re < 2000) due to smaller hydraulic diameter. The laminar flow heat transfer in a smooth microchannel is limited by the boundary layer thickness. Commonly the heat transfer rate is enhanced by passively disrupting the laminar boundary layer using protrusions or depressions in the channel walls. More often these methods are best applicable at small range of Reynolds number where the heat transfer rate enhancement is more than the pressure drop increase and break down as the flow rate is changed outside the range. The benefit of a flow disruption method can be reaped only if it provides higher heat transfer enhancement than the increase in the pressure drop at the working flow rates in the microchannel. A heat transfer efficient microchannel design has been developed using wall features that create stable disrupted flow and break the laminar boundary layer in a microchannel over a wide range of flow rates. The paper experimentally investigates the developed design for the heat transfer enhancement and pressure drop increase compared to a smooth wall microchannel. A simple microchannel device was designed and fabricated with and without wall features. The experiments with single gas phase fluid showed promising results with the developed wall feature design as the heat transfer rate increase was 20% to 80% more than the pressure drop increase in the laminar regime. The wall feature design was an important variable to affect the magnitude of performance enhancement in different flow regime. A general criterion was developed to judge the efficacy of wall feature design that can be used during a microchannel heat exchanger design.

Optimal Analysis of Entropy Generation and Heat Transfer in Parabolic Trough Collector Using Green-Synthesized TiO2/Water Nanofluids

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Eric C. Okonkwo ◽  
Muhammad Abid ◽  
Tahir A. H. Ratlamwala ◽  
Serkan Abbasoglu ◽  
Mustafa Dagbasi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Entropy Generation Rate ◽  
Convection Coefficient ◽  
Parabolic Trough ◽  
Volumetric Concentration ◽  
Flow Rates

This study presents an experimental nanoparticle synthesis and the numerical analysis of a parabolic trough collector (PTC) operating with olive leaf synthesized TiO2/water nanofluid. The PTC is modeled after the LS-2 collector for various operating conditions. An analysis of the heat transfer and entropy generation in the PTC is carried out based on the first and second laws of thermodynamics for various parameters of nanoparticle volumetric concentration (0 ≤ φ ≤ 8%), mass flow rate (0.1 ≤ m˙ ≤ 1.1 kg/s), and inlet temperatures (350–450 K) under turbulent flow regime. The effect of these parameters is evaluated on the Nusselt number, thermal losses, heat convection coefficient, outlet temperature, pressure drop, entropy generation rate, and Bejan number. The results show that the values of the Nusselt number decrease with higher concentrations of the nanoparticles. Also, the addition of nanoparticles increases the heat convection coefficient of the nanofluid compared to water. The thermal efficiency of the system is improved with the use of the new nanofluid by 0.27% at flow rates of 0.1 kg/s. The entropy generation study shows that increasing the concentration of nanoparticles considerably decreases the rate of entropy generation in the system. It is also observed that increasing the volumetric concentration of nanoparticles at low mass flow rates has minimal effect on the rate of entropy generation. Finally, a correlation that provides a value of mass flow rate that minimizes the entropy generation rate is also presented for each values of inlet temperature and nanoparticle volumetric concentration.

Thermal Performance of Microencapsulated Phase Change Material Slurry in a Coil Heat Exchanger

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Min-Suk Kong ◽  
Kun Yu ◽  
Jorge L. Alvarado ◽  
Wilson Terrell
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Phase Change ◽  
Thermal Performance ◽  
Mass Fraction ◽  
Microencapsulated Phase Change Material ◽  
Coil Heat Exchanger ◽  
Change Material ◽  
Coil Heat

An experimental study has been carried out to investigate the convective heat transfer and pressure drop characteristics of microencapsulated phase change material (MPCM) slurry in a coil heat exchanger (CHX). The thermal and fluid properties of the MPCM slurries were determined using a differential scanning calorimeter (DSC) and a rotating drum viscometer, respectively. The overall heat transfer coefficient and pressure drop of slurries at 4.6% and 8.7% mass fractions were measured using an instrumented CHX. A friction factor correlation for MPCM slurry in the CHX has been developed in terms of Dean number and mass fraction of the MPCM. The effects of flow velocity and mass fraction of MPCM slurry on thermal performance have been analyzed by taking into account heat exchanger effectiveness and the performance efficiency coefficient (PEC). The experimental results showed that using MPCM slurry should improve the overall performance of a conventional CHX, even though the MPCM slurries are characterized by having high viscosity.

Computational Study and Optimization of Laminar Heat Transfer and Pressure Loss of Double-Layer Microchannels for Chip Liquid Cooling

2013 ◽  
Vol 5 (1) ◽  
Author(s):  
Gongnan Xie ◽  
Yanquan Liu ◽  
Bengt Sunden ◽  
Weihong Zhang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Double Layer ◽  
Flow Rate ◽  
Single Layer ◽  
Parallel Flow ◽  
Heat Fluxes ◽  
Liquid Cooling ◽  
Counter Flow ◽  
Flow Rates

The problem involved in the increase of the chip output power of high-performance integrated electronic devices is the failure of reliability because of excessive thermal loads. This requires advanced cooling methods to be incorporated to manage the increase of the dissipated heat. The traditional air-cooling can not meet the requirements of cooling heat fluxes as high as 100 W/cm2, or even higher, and the traditional liquid cooling is not sufficient either in cooling very high heat fluxes although the pressure drop is small. Therefore, a new generation of liquid cooling technology becomes necessary. Various microchannels are widely used to cool the electronic chips by a gas or liquid removing the heat, but these microchannels are often designed to be single-layer channels with high pressure drop. In this paper, the laminar heat transfer and pressure loss of a kind of double-layer microchannel have been investigated numerically. The layouts of parallel-flow and counter-flow for inlet/outlet flow directions are designed and then several sets of inlet flow rates are considered. The simulations show that such a double-layer microchannel can not only reduce the pressure drop effectively but also exhibits better thermal characteristics. Due to the negative heat flux effect, the parallel-flow layout is found to be better for heat dissipation when the flow rate is limited to a low value while the counter-flow layout is better when a high flow rate can be provided. In addition, the thermal performance of the single-layer microchannel is between those of parallel-flow layout and counter-flow layout of the double-layer microchannel at low flow rates. At last, the optimizations of geometry parameters of double-layer microchannel are carried out through changing the height of the upper-branch and lower-branch channels to investigate the influence on the thermal performance.

scholarly journals Design and Analysis of double- stacked Heat Exchanger for Brewery Application

2020 ◽  
Vol 9 (1) ◽  
pp. 1793-1798
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Flow Rate ◽  
Transfer Rate ◽  
Working Fluid ◽  
Support Weight ◽  
Tube Heat Exchanger ◽  
Shell And Tube

A heat exchanger is a device intensively used for enhancing the transfer of heat energy between two or more working fluids at different temperature, which are in thermal contact. The optimal design and efficient operation of heat exchanger and heat transfer network are of a great significance in any of the process industry. The heat transfer efficiency depends on both design of heat exchanger and property of working fluid. From various types of heat exchanger, the double stacked shell and tube heat exchanger with straight tube and single pass is to be under study. Here the redesign of heat exchanger takes place with the key objectives of optimizing the pressure drop, optimizing the heat transfer rate and reducing the saddle support weight used for cooling purpose in brewery application. The design calculations are carried out using the Kerns and Bell Delwar method and other important parameters dealing with material selection and geometries are also taken into consideration. FEA analysis for optimizing the saddle support weight is carried out using Dassault systeme’s Solidworks while the CFD analysis for optimizing pressure drop and heat transfer rate is carried out using Dassault systeme’s Solidworks analysis software and the design and working of Shell and tube heat exchanger is determined in terms of variables such as pressure ,temperature ,mass flow rate ,flow rate ,energy input output that are of particular interest in Shell and tube heat exchanger analysis.

scholarly journals Thermo-Hydraulic Performance Analysis on the Effects of Truncated Twisted Tape Inserts in a Tube Heat Exchanger

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1652
Author(s):  
Mehdi Ghalambaz ◽  
Ramin Mashayekhi ◽  
Hossein Arasteh ◽  
Hafiz Muhammad Ali ◽  
Pouyan Talebizadehsardari ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Tube Heat Exchanger ◽  
Twisted Tapes ◽  
Plain Tube

This paper investigates the convective heat transfer in a heat exchanger equipped with twisted tape elements to examine effects of the twisted tape truncation percentage, pitch value, position and Reynolds number using 3D numerical simulation. A symmetric heat flux is applied around the tube as the studied heat exchanger. Based on the influences in both heat transfer enhancement and pressure drop, the performance evaluation criterion (PEC) is utilized. Inserting twisted tape elements and reducing the pitch value significantly augment the Nusselt number, friction coefficient and PEC number compared to the plain tube. For the best case with a Reynolds number of 1000, the average Nusselt number increases by almost 151%, which is the case of fully fitted twisted tape at a pitch value of L/4. Moreover, increasing the twisted tape truncation percentage reduces both heat transfer and pressure drop. Furthermore, the highest heat transfer rate is achieved when the truncated twisted tape is located at the entrance of the tube. Finally, it is concluded that for P = L, L/2, L/3 and L/4, the optimum cases from the viewpoint of energy conservation are twisted tapes with truncation percentages of 75, 50, 50 and 0%, in which the related PEC numbers at a Reynolds number of 1000 are almost equal to 1.08, 1.24, 1.4 and 1.76, respectively.

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