VOLUME: 07, Special Issue 07, Paper id-IJIERM-VII-VII, October 2020
120 CFD ANALYSIS OF A PARALLEL FLOW HEAT EXCHANGER: A REVIEW1Deobrat Kumar Bhaskar, M.Tech, Student
2Dr. Anoop Kumar Pathariya,
1,2Technocrat Institute of Technology, Bhopal 1. INTRODUCTION
1.1 Heat Exchanger
Warmth exchanger gadget is utilized to send heat energy starting with one liquid then onto the next liquid. Condenser and evaporators utilized in different cooling units and fridges are exceptionally normal warmth exchangers utilized in our everyday life. Warmth exchangers are additionally utilized in numerous other modern cycle in which a fluid or gas is needed to be either cooled or warmed.
Heater and condensers are likewise instances of huge mechanical warmth exchangers. Warmth exchangers are additionally utilized in vehicles as radiator and oil cooler. Warmth exchangers are richly utilized in substance and cycle businesses. There is a wide assortment of warmth exchangers accessible for the wide scope of uses.
Nonetheless, heat exchangers can likewise be ordered based on basic plan includes rather than assortment.
1.2 Double Pipe Heat Exchanger
Twofold line heat exchanger is vital in various modern cycle. It is developed by two concentric lines. Two liquids move through the inward and external lines.
Generally liquids stream in inverse ways.
This is the least difficult kind of warmth exchanger, named twofold line heat exchanger on account of the concentric cylinder development. In such warmth exchanger one liquid streams under the line and different streams between the line and another concentric line which encompasses the first. The stream might be equal or counter in twofold line heat exchanger.
1.3 Objective of work
From the writing survey, it tends to be perceived that addition of wound tape in a round cylinder is one of the viable expansion draws near. The embedded wound tape creates twirling stream, longer way and blockage of the stream
which are the major affecting variables for heat move upgrade.
Truth be told, utilizing bent tape increments both attractive warmth move rate and bothersome erosion misfortune (pressure drop). In this manner, the need of suitable wound tape alteration is a test task as an appropriate plan of turned tape is a primary key for heat move upgrade at a sensible erosion misfortune.
Aside from curved tape plan for the upgrade of warmth move punctured plate is pursued for the satisfaction of present work.
2. LITERATURE SURVEY
Mohamad Omidi1 et al [2017] explored the expansion in warmth move rate alongside diminishing size and cost of the modern device appropriately. The improvement strategy that this sort of warmth exchanger experienced has been dissected in subtleties and the warmth move upgrade techniques in previously mentioned heat exchangers have likewise been broadly talked about. In this audit, relationships of generally Nusselt number and pressing factor drop coefficient are introduced.
It is accepted that this survey gave new experiences to additional examinations. Sometimes, the warmth move rate discovered to increment around 400 percent, while the most pressing factor drop decline was 1000 percent in contrast with smooth cylinder. In large numbers of these examinations, auxiliary stream assumes a huge part in expanding the warmth move rate. In some examination, the warmth upgrade strategies, for example, snaked wires were likewise utilized in the annulus of the twofold line heat exchanger.
Anas El Maakoul 2 et al [2017]
investigated the design and thermo- hydraulic performance of a double pipe heat exchanger with helical baffles in the annulus side. The numerical model was first validated for a simple double pipe
VOLUME: 07, Special Issue 07, Paper id-IJIERM-VII-VII, October 2020
121 heat exchanger by comparison withempirical correlations. The model was then used to investigate the helical baffles effects.
The results obtained for a helically baffled annulus side provide enhanced heat transfer performance and high- pressure drop compared to the simple double-pipe exchangers. In addition, empirical correlations expressing the results were developed based on curve fitting. The results indicate that, compared to the conventional annulus side, using helical baffles in the annulus side augments the convective heat transfer by 5%, 17%, 30% and 45% on average with an increase in pressure drop equal on average to 2, 5, 11 and 21 time the pressure drop for a conventional annulus side, for B equal to 100 mm, 50 mm, 33.3 mm and 25 mm respectively.
M. Sheikholeslami3 et al [2016]
tentatively examined heat move and constrain misfortune in an air to water twofold line heat exchanger. Average roundabout ring (TCR) and punctured roundabout ring (PCR) turbulators are put in annular line. The examinations are directed for various overseeing boundaries to be specific; wind stream Reynolds number (6000–12,000), pitch proportion (1.83, 2.92 and 5.83) and number of punctured opening (0, 2, 4 and 8).
Connections for rubbing factor, Nusselt number and warm execution are introduced by trial information. Results showed that utilizing PCRs prompts get lower heat move upgrade than the CRs due to decrease of convergence point between the speed and the temperature field. Warm execution increments with increment of N yet it diminishes with increment of Reynolds number and pitch proportion. The impacts of the pitch proportion and number of punctured opening on stream and warmth move qualities are thought of. The connections of the Nusselt number, erosion factor and warm execution are introduced.
P.V. Durga Prasad4 et al [2015]
presented trapezoidal-cut twisted tape insert in a double pipe U-tube heat exchanger Experimental data is generated at flow rates ranging from 0.0333 kg/s to 0.2667 kg/s. Experimental data is generated with water and nano-fluid for Reynolds number in the range
3000<Re<30000, the Nusselt number of entire pipe for 0.03% concentrations of nano-fluid with trapezoidal-cut twisted tape inserts of H/D = 5 is enhanced by 34.24% as compared to water.
The friction factor of entire pipes for 0.03% concentration of nano-fluid with trapezoidal-cut twisted tape inserts of H/D=5 is enhanced by 1.29 times as compared to water. Convective heat transfer, friction factor as well as thermal performance factor tends to an increase by increasing Al2O3 concentration of nano-fluid and twist ratio of trapezoidal- cut tape inserts.
Ojha Pramod Kailash5 et al [2015] utilized warmth exchanger having tube with balance and without balance.
The balances were taken as semi- roundabout sort masterminded in exchanging route with dividing of 50mm.
The blades were just given on the internal cylinder to making disturbance of cold water. The quantities of blade were 18 and its tallness and thickness 10 and 1.6mm individually. Various boundaries were acquired and thought about for basic internal cylinder and finned tube.
They found For = 17161.05, the general warmth move coefficient utilizing semi- round balance diminishes is more than 300 % which shows that enormous expansions in by and large warmth move territory.
Nonetheless, the warmth move improvement coefficient acts oppositely, as this amount increments with increments in warmth move zone. For mass stream rate 0.3832 kg/sec, the declines in convective warmth move coefficient for the virus side is around 220
% more than for basic cylinder consequently indicating better warmth move. While for more sizzling side the worth increments around 125%.
The expansions in rubbing factor for the virus side for finned tube is around 140 % more than straightforward cylinder for = 15954.24 while for the hot side the estimation of erosion factor remains roughly same for both cylinder.
The pressing factor drop because of contact in virus side for the finned tube is around 450 % more than the straightforward cylinder.
VOLUME: 07, Special Issue 07, Paper id-IJIERM-VII-VII, October 2020
122 Tzu-Chen Hung 6 et al [2015]used computational fluid dynamics (CFD) to simulate a three-dimensional concentric high temperature heat exchanger. They used helium gas and molten salt as hot and cold streams respectively in a counter-flow mode. Flow fields and heat transfer characteristics of the two concentric channels are examined extensively.
A design with an optimal performance of the heat exchanger is achieved by maximizing the effectiveness of the heat exchanger (ε-NTU method) using the following parameters as optimizing variables; the width of the flow channel, the length, pitch, thickness, and angle of the fins. The number of CFD simulation are substantially reduced by Taguchi method, and the optimal configurations of the concentric high temperature heat exchanger are found with a channel width of 1 mm, a fin length of 11 mm, an angle of fin of 2.6, and a fin thickness of 1.125 mm.
Jibin Johnson7 et al [2015]
validated analytical design of the exchanger based on the results obtained from the CFD analysis. CFD analysis is based on the standard k-ε modeling. The solution of the problem yields the optimum values of inner pipe diameter, outer pipe diameter and utility flow rate to be used for a double pipe heat exchanger of a given effective length, when a specified flow rate of process stream is to be treated for a given inlet to outlet temperature.
By observing the velocity contours we can infer that the velocity distributions inside the pipes are in the lower range of colour code. That means the velocity distribution is minimum to enhance the heat transfer rate. Also the temperature path lines show that the temperature distribution is in the maximum scale range, which shows the perfect heat transfer rate.
H.A. Mohammed8 et al [2012]
examined the impact of utilizing louvered strip embeds put in a roundabout twofold line heat exchanger on the warm and stream fields using different sorts of nano-fluids. Two diverse louvered strip embed courses of action (forward and in reverse) are utilized in this examination with a Reynolds number scope of 10,000
to 50,000. The impacts of different louvered strip incline points and pitches are likewise researched.
The mathematical outcomes demonstrate that the forward louvered strip plan can advance the warmth move by roughly 367% to 411% at the most elevated inclination point of α=30° and least pitch of S=30 mm. The maximal skin grating coefficient of the improved cylinder is around multiple times than that of the smooth cylinder and the estimation of execution assessment basis (PEC) lies in the scope of 1.28–1.56. It is discovered that SiO2 nano liquid has the most elevated Nusselt number worth, trailed by Al2O3, ZnO, and CuO while unadulterated water has the least Nusselt number.
Ebru Kavak Akpinar9 [2006]
evaluated experimentally by mounting helical (spring shaped) wires of different pitch in the inner pipe in a double pipe heat exchanger. In the experiments, hot (air) and cold (water) fluids flowed through the inner pipe and annulus, respectively.
The experiments were performed for both parallel and counter current flow modes of the fluids at Reynolds numbers between 6500 and 13,000.
An augmentation of up to 2.64 times in Nusselt number compared to the empty pipe was obtained in the helical system. The increase in friction factor was about 2.74 times that of the empty pipe, depending on Reynolds number and the pitch or helical number. An augmentation of up to 1.16 times in the dimensionless energy loss compared to the empty pipe was obtained in the helical system.
3. CFD MODELLING
3.1 Computational Fluid Flow Analysis Liquid mechanics is the part of science, which manages liquid stream. The conditions which portray the movement of liquid substances are Navier Stokes conditions, which were created by Navier and Stokes in the mid nineteenth century.
These conditions are set of coupled differential conditions and can be tackled for a given stream issue by utilizing techniques from analytics.
In any case, practically speaking, these conditions are too hard to ever be settled logically. Before, engineers made further approximations and
VOLUME: 07, Special Issue 07, Paper id-IJIERM-VII-VII, October 2020
123 rearrangements to the condition set tobuild up a gathering of conditions that they could tackle. As of late, high velocity PCs were utilized to address approximations to the conditions utilizing an assortment of procedures like limited distinction, limited volume, limited component, and ghastly techniques. This territory of study is alluded to as Computational Fluid Dynamics or CFD.
4. RESEARCH METHODOLOGY
In all of these approaches the same basic procedure is followed.
1. Preprocessing
2. The geometry (physical bounds) of the problem is defined.
3. The volume occupied by the fluid is divided into discrete cells (the
mesh). The mesh may be uniform or non uniform.
4. The Mathematical modelling is defined
5. Boundary conditions are defined.
This involves specifying the fluid behaviour and properties at the boundaries of the problem.
6. Processing
7. The simulation is started and the equations are solved iteratively as a steady-state
8. Postprocessor
9. Result is generated during processing is used for the analysis and visualization of the resulting solution.
10. Parametric value is being generated.
Figure 1 Sectional View Perforated Plate
VOLUME: 07, Special Issue 07, Paper id-IJIERM-VII-VII, October 2020
124 Figure 2 Sectional View of Concetric TubeThe penetrated plate with five comparably space opening are is being outfit with the thickness of 1mm. The penetrated domain perfectly healthy. The numerical assessments are finished with the assortment of this (penetrated zone) indirect estimation. Though the zone is pretty much nothing yet it is sufficient to perceive the effect of warmth move with this penetrated plate. The penetrated plate is given on focus scope of concentric line heat exchanger. Other component of the glow exchanger is given in the table.
The worm liquid (Benzene fluid) stream in the external line and Cold liquid (Water) stream inside the cylinder in a counter- ebb and flow arrangement.
4.1 Modelling Setup and Governing Equations
The first step in completing a CFD analysis of a system is to set up the governing equations. The equations involved in incompressible flow are continuity equation, momentum equation, and energy equation. [12]
∂ ρu
∂x +∂ ρv
∂y +∂ ρw
∂z = 0 Navier Stokes equation
ρ u∂u
∂x+ v∂u
∂y+ u∂u
∂z
=ρX −∂p
∂x +1
3μ ∂
∂x
∂u
∂x+∂v
∂y+∂w
∂z +μ∇2u
ρ u∂v
∂x+ v∂v
∂y+ u∂v
∂z
=ρX −∂p
∂x +1
3μ ∂
∂y
∂u
∂x+∂v
∂y+∂w +μ∇2u ∂z
ρ u∂w
∂x + v∂w
∂y+ u∂w
∂z
=ρX −∂p
∂x +1
3μ ∂
∂z
∂u
∂x+∂v
∂y+∂w
∂z +μ∇2u
Energy Equation ρCp u∂T
∂x+ v∂T
∂y+ u∂T
∂z
= u∂p
∂x+ v∂p
∂y+ w∂p
∂z + k∇2T +μ∅
Where,
∅ = 2 ∂u
∂x
2
+ ∂v
∂y
2
+ ∂w
∂z
2
+ ∂u
∂y+∂v
∂x
2
+ ∂v
∂z+∂w
∂y
2
+ ∂w
∂x+∂u
∂z
2
−2 3
∂u
∂x+∂v
∂y+∂w
∂z
2
4.1.1 Standard k-ε Model
The easiest "complete models" of disturbance are the two-condition models in which the arrangement of two separate vehicle conditions permits the fierce speed
VOLUME: 07, Special Issue 07, Paper id-IJIERM-VII-VII, October 2020
125 and length scales to be autonomouslydecided. The standard k-ε model in ANSYS FLUENT falls inside this class of models and has become the workhorse of viable designing stream counts in the time since it was proposed by Launder and Spalding. Vigor, economy, and sensible precision for a wide scope of tempestuous streams clarify its fame in modern stream and warmth move reenactments.
It is a semi-observational model, and the induction of the model conditions depends on phenomenological contemplations and experimentation. As the qualities and shortcomings of the standard k-ε model have gotten known, upgrades have been made to the model to improve its presentation. Two of these variations are accessible in ANSYS FLUENT, the RNG k-ε model and the feasible k-ε model. The standard k-ε model is a semi-experimental model dependent on model vehicle conditions for the disturbance active energy (k) and its dissemination rate (ε).
The model vehicle condition for k is gotten from the specific condition, while
the model vehicle condition for ε was acquired utilizing actual thinking and bears little likeness to its numerically correct partner. In the inference of the k-ε model, the supposition that will be that the stream is completely violent, and the impacts of atomic consistency are irrelevant. The standard k-ε model is thusly substantial just for completely tempestuous streams.
5. VALIDATION OF CFD CODE
The current work, a CFD demonstrating is completed to see of the warmth move rate for concentric line heat exchanger outfitted with punctured plate at the center range of inward line. This work is approved as underneath. To show case the capacity of the CFD in foreseeing the liquid stream and warmth move in the cylinder outfitted with punctured plate, the CFD code is approved with considering the plain cylinder and the recreated grating component across the cylinder are contrasted and try completed by [2]
Figure 3 The comparison between the experimental and simulated 6. CONCLUSION AND SCOPE FOR
FUTURE WORK
The examinations of warmth move coefficient and warmth move rate for punctured plate fitted in inward line of the concentric line heat exchanger at mid range of warmth exchanger have been contemplated. Diverse measurement of hole opening in the plate with various
mass stream pace of water (internal line liquid) has been mathematically researched. In post examination it has been distinguished that for increment of mass stream pace of water increment the warmth move rate for lower measurement of hole. Thus lessening of hole distance across upgrade the warmth move rate as contrast with higher breadth of hole.
0 0.01 0.02 0.03 0.04 0.05 0.06
0 0.00005 0.0001 0.00015
Friction Factor
m3/sec
validation
friction factor simulated
Experimental data paper
VOLUME: 07, Special Issue 07, Paper id-IJIERM-VII-VII, October 2020
126 REFERENCES1. Mohamad Omidi et al. “A comprehensive review on double pipe heat exchangers”
Applied Thermal Engineering Science Direct.
2. Anas El Maakoul et al. “Numerical design and investigation of heat transfer enhancement and performance for an annulus with continuous helical baffles in a double-pipe heat exchanger.” Energy Conversion and Management 133 (2017) 76–86 Science Direct.
3. M. Sheikholeslami et al. “Experimental study on turbulent flow and heat transfer in an air to water heat exchanger using perforated circular- ring” Experimental Thermal and Fluid Science 70 (2016) 185–195 Science Direct.
4. P.V. Durga Prasad et al. “Investigation of Trapezoidal-Cut Twisted Tape Insert in a Double Pipe U-Tube Heat Exchanger using Al2O3/Water Nano-fluid.” Procedia Materials Science 10 (2015) 50 – 63, 2nd International Conference on Nano- materials and Technologies (CNT 2014).
5. Ojha Pramod Kailas et al. “Design and experimental analysis of pipe in pipe heat exchanger” | IJMER | ISSN: 2249–
6645 | Vol. 5 | Iss.3| Mar. 2015 | 42|.
