Investigation of Two-Phase Liquid-Droplet Flow With Particle Deposition in the Heat Exchanger

This article presents a numerical study of particle deposition in two fluids, i.e., liquid and droplet flow in a single row tube bundle heat exchanger. The tubes in the heat exchanger are modeled as heating sources. Two level-set functions are used to capture the liquid-droplet interface and the liquid-deposit front. The effects of different parameters, including Damköhler number, thermal conductivity of the deposit, viscosity of the liquid, and the heating power of the tube on the flow and heat transfer, are investigated. The deposit profiles on the tube surface are analyzed. Comparison is made for the averaged Nusselt number for the case without and with deposition. It is found that the tube surface has a thicker deposit at the upstream facing side compared with that of the downstream facing side. Generally, the heat transfer rate reduces with the growth of the deposit. Under certain conditions, heat transfer can be increased because of the increase in fluid velocity due to blockage of the flow area by the deposit. The averaged Nusselt number oscillated temporally in response to the droplet movement across the tube. Generally, the temperature at the liquid-deposit front decreases with thicker deposit formed. The averaged Nusselt number along the liquid-deposit front increases to a critical value initially, and it starts to decrease with the growth of the deposit.

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Natural Convective Flow and Heat Transfer in a Collector Storage with an Immersed Heat Exchanger: Numerical Study

Journal of Solar Energy Engineering ◽

10.1115/1.1934735 ◽

2005 ◽

Vol 127 (3) ◽

pp. 324-332 ◽

Cited By ~ 17

Author(s):

Yan Su ◽

Jane H. Davidson

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Heat Exchanger ◽

Numerical Study ◽

Storage System ◽

Fluid Motion ◽

Heat Transfer Process ◽

Strong Mixing ◽

Scale Analysis ◽

Three Dimensional Model

A three-dimensional model and dimensionless scale analysis of the transient fluid dynamics and heat transfer in an inclined adiabatic water-filled enclosure with an immersed cylindrical cold sink is presented. The geometry represents an integral collector storage system with an immersed heat exchanger. The modeled enclosure has an aspect ratio of 6:1 and is inclined at 30deg to the horizontal. The heat exchanger is represented by a constant surface temperature horizontal cylinder positioned near the top of the enclosure. A scale analysis of the transient heat transfer process identifies four temporal periods: conduction, quasi-steady, fluctuating, and decay. It also provides general formulations for the transient Nusselt number, and volume-averaged water temperature in the enclosure. Insight to the transient fluid and thermal processes is provided by presentation of instantaneous flow streamlines and isotherm contours during each transient period. The flow field consists of two distinct zones. The zone above the cold sink is nearly stagnant. The larger zone below the sink is one of strong mixing and recirculation initiated by the cold plume formed in the boundary layer of the cylindrical sink. Correlations for the transient Nusselt number and the dimensionless volume-averaged tank temperature predicted from the model compare favorably to prior measured data. Fluid motion in the enclosure enhances heat transfer compared to that of a cylinder in an unbounded fluid.

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Experimental and numerical studies of a spiral plate heat exchanger

Thermal Science ◽

10.2298/tsci130317131r ◽

2014 ◽

Vol 18 (4) ◽

pp. 1355-1360 ◽

Cited By ~ 5

Author(s):

Rajavel Rangasamy

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Heat Exchanger ◽

Numerical Study ◽

Numerical Models ◽

Plate Heat Exchanger ◽

Test Fluid ◽

Plate Heat ◽

Plate Spacing ◽

Spiral Plate

An experimental and numerical study of heat transfer and flow characteristics of spiral plate heat exchanger was carried out. The effects of geometrical aspects of the spiral plate heat exchanger and fluid properties on the heat transfer characteristics were also studied. Three spiral plate heat exchangers with different plate spacing (4mm, 5mm and 6 mm) were designed, fabricated and tested. Physical models have been experimented for different process fluids and flow conditions. Water is taken as test fluid. The effect of mass flow rate and Reynolds number on heat transfer coefficient has been studied. Correlation has been developed to predict Nusselt numbers. Numerical models have been simulated using CFD software package FLUENT 6.3.26. The numerical Nusselt number have been calculated and compared with that of experimental Nusselt number.

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Numerical Study of Shellside Performance of Heat Transfer and Flow Resistance for Heat Exchanger with Trefoil-Hole Baffles

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.557-559.2141 ◽

2012 ◽

Vol 557-559 ◽

pp. 2141-2146

Author(s):

Yong Hua You ◽

Ai Wu Fan ◽

Chen Chen ◽

Shun Li Fang ◽

Shi Ping Jin ◽

...

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

Heat Exchanger ◽

Heat Transfer Rate ◽

Pressure Loss ◽

Transfer Rate ◽

Numerical Study ◽

Shell Side ◽

Tube Heat Exchanger

Trefoil-hole baffles have good thermo-hydraulic performances as the support of heat pipes, however the published research paper is relatively limited. The present paper investigates the shellside thermo-hydraulic characteristics of shell-and-tube heat exchanger with trefoil-hole baffles (THB-STHX) under turbulent flow region, and the variations of shellside Nusselt number, pressure loss and overall thermo-hydraulic performance (PEC) with Reynolds number are obtained for baffles of varied pitch with the numerical method. CFD results demonstrate that the trefoil-hole baffle could enhance the heat transfer rate of shell side effectively, and the maximal average Nusselt number is augmented by ～2.3 times that of no baffle, while average pressure loss increases by ～9.6 times. The PEC value of shell side lies in the range of 16.3 and 73.8 kPa-1, and drops with the increment of Reynolds number and the decrement of baffle pitch, which indicates that the heat exchanger with trefoil-hole baffles of larger pitch could generate better overall performance at low Reynolds number. Moreover, the contours of velocity, turbulent intensity and temperature are presented for discussions. It is found that shellside high-speed jet, intensive recirculation flow and high turbulence level could enhance the heat transfer rate effectively. Besides good performance, THB-STHXs are easily manufactured, thus promise widely applied in various industries.

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Numerical Study of Flow and Heat Transfer Enhancement by Using Delta Winglets in a Triangular Wavy Fin-and-Tube Heat Exchanger

Journal of Heat Transfer ◽

10.1115/1.3139106 ◽

2009 ◽

Vol 131 (9) ◽

Cited By ~ 20

Author(s):

Liting Tian ◽

Yaling He ◽

Pan Chu ◽

Wenquan Tao

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Fluid Flow ◽

Heat Exchanger ◽

Friction Factor ◽

Numerical Study ◽

Attack Angle ◽

Geometrical Parameters ◽

Tube Heat Exchanger ◽

Delta Winglet

In this paper, three-dimensional numerical simulations with renormalization-group (RNG) k-ε model are performed for the air-side heat transfer and fluid flow characteristics of wavy fin-and-tube heat exchanger with delta winglet vortex generators. The Reynolds number based on the tube outside diameter varies from 500 to 5000. The effects of different geometrical parameters with varying attack angle of delta winglet (β=30 deg, β=45 deg, and β=60 deg), tube row number (2–4), and wavy angle of the fin (θ=0–20 deg) are examined. The numerical results show that each delta winglet generates a downstream main vortex and a corner vortex. The longitudinal vortices are disrupted by the downstream wavy trough and only propagate a short distance along the main flow direction but the vortices greatly enhance the heat transfer in the wake region behind the tube. Nusselt number and friction factor both increase with the increase in the attack angle β, and the case of β=30 deg has the maximum value of j/f. The effects of the tube row number on Nusselt number and friction factor are very small, and the heat transfer and fluid flow become fully developed very quickly. The case of θ=5 deg has the minimum value of Nusselt number, while friction factor always increases with the increase in wavy angle. The application of delta winglet enhances the heat transfer performance of the wavy fin-and-tube heat exchanger with modest pressure drop penalty.

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Natural Convective Flow and Heat Transfer in a Collector Storage With an Immersed Heat Exchanger: Numerical Study

Solar Energy ◽

10.1115/isec2005-76004 ◽

2005 ◽

Author(s):

Yan Su ◽

Jane H. Davidson

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Heat Exchanger ◽

Numerical Study ◽

Storage System ◽

Three Dimensional ◽

Heat Transfer Process ◽

Strong Mixing ◽

Scale Analysis ◽

Three Dimensional Model

A three-dimensional model and dimensionless scale analysis of the transient fluid dynamics and heat transfer in an inclined adiabatic water-filled enclosure with an immersed cylindrical cold sink is presented. The geometry represents an integral collector storage system with an immersed heat exchanger. The modeled enclosure has an aspect ratio of 6:1 and is inclined at 30 degrees to the horizontal. The heat exchanger is represented by a constant surface temperature horizontal cylinder positioned near the top of the enclosure. A scale analysis of the transient heat transfer process identifies four temporal periods: conduction, quasi-steady, fluctuating and decay. It also provides general formulations for the transient Nusselt number, and volume averaged water temperature in the enclosure. Insight to the transient fluid and thermal processes is provided by presentation of instantaneous flow streamlines and isotherm contours during each transient period. The flow field consists of two distinct zones. The zone above the cold sink is nearly stagnant. The larger zone below the sink is one of strong mixing and recirculation initiated by the cold plume formed in the boundary layer of the cylindrical sink. Correlations predicted with the model for the transient Nusselt number and the dimensionless volume averaged tank temperature expressed in terms of the initial Rayleigh number compare favorably to prior measured data.

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Numerical Study of Heat Transfer Enhancement in Contour Corrugated Channel Using Water and Engine Oil

CFD letters ◽

10.37934/cfdl.12.12.1737 ◽

2020 ◽

Vol 12 (12) ◽

pp. 17-37

Author(s):

Naseer Dawood khata ◽

Zena Khalefa Kadim ◽

Kamil Abdulhussein Khalaf

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Heat Exchanger ◽

Wave Height ◽

Thermal Performance ◽

Numerical Study ◽

Hydraulic Performance ◽

Performance Criteria ◽

Engine Oil ◽

Corrugated Channel

Improving the design of geometrical parameters of heat exchanger leads to enhance heat transfer and makes it further compacted which in turn increases the efficiency of the thermal process, leading to save operating costs. In the present investigation, thermal and hydraulic performance of laminar flow of the trapezoidal, sinusoidal, and straight counter heat exchanger with water and engine oil was carried out numerically over Reynolds number ranges of 1100-2300 for water and 250 for engine oil. The effect of wave height and wavelength of both trapezoidal and sinusoidal on the thermal properties and hydraulic performance are studied. The numerical study showed that the effect of wave height on the Nusselt number was greater than that of wavelength in both trapezoidal and sinusoidal channels. The study also showed that the trapezoidal channel's influence on Nusselt number was higher than that of the sinusoidal channel and straight channel respectively. Thermal and flow characteristics are explored with the help of the streamwise velocity and isotherms contours for trapezoidal and sinusoidal-corrugated channels. In addition, the success of the heat exchanger design was evaluated by the results of the thermal performance criteria. The results of the thermal performance criteria at all wave heights and wavelength of the corrugated channel were greater than 1, which is indicating that the heat transfer rate is higher than the friction losses. Consequently, the use of corrugated surfaces in Contour heat exchangers can improve heat transfer in many applications.

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Natural convection heat transfer performance of additively manufactured tube bundle heat exchangers with novel fin design

Heat and Mass Transfer ◽

10.1007/s00231-020-03014-5 ◽

2021 ◽

Author(s):

Sebastian Unger ◽

Matthias Beyer ◽

Heiko Pietruske ◽

Lutz Szalinski ◽

Uwe Hampel

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Nusselt Number ◽

Heat Exchanger ◽

Flux Density ◽

Heat Flux Density ◽

Tube Bundle ◽

Convection Heat Transfer ◽

Pin Fins ◽

Fin Design

AbstractWe studied the heat transfer of finned heat exchanger configurations with a novel design. These novel fin designs use integrated pins to enhance the heat conduction from the fin base to the fin tip as well as the air-side heat transfer on the fin surface. Oval tubes with conventional circular plain fins (CPF) as well as novel circular integrated pin fins (CIPF) and serrated integrated pin fins (SIPF) were additively generated by a Selective Laser Melting (SLM) process and installed at the bottom of a 6.5 m long chimney. All heat exchanger designs were tested in a 2-row and 3-row configuration with Rayleigh numbers between 25,000 and 120,000. We found the average Nusselt number of SIPF to be higher and the Nusselt number of the CIPF to be lower than for the CPF. Moreover, the 2-row configuration achieved a higher Nusselt number compared to the 3-row configuration for all heat exchanger designs. The analysis of the individual tube rows showed the highest Nusselt numbers at the first tube row and the lowest one at the last tube row for both configurations. However, for the SIPF the difference between the first and second tube row is smaller compared to the CPF and CIPF. In order to evaluate the compactness of the heat exchanger, the volumetric heat flux density was considered. Similar to Nusselt number the volumetric heat flux density enhanced for the SIPF and reduced for the CIPF compared to the conventional design. Also the 2-row configuration reached greater thermal performance compared to the 3-row configuration. Additionally, the volume and the surface area of the heat exchanger are 6.9% and 30.7% lower for the SIPF compared to the CPF. The experimental data were used to develop an empirical heat transfer correlation between Nusselt number, Rayleigh number, fin design and tube row number.

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