Top PDF Round-Tube and Microchannel Heat Exchanger Modeling at Wet Air Condition

Round-Tube and Microchannel Heat Exchanger Modeling at Wet Air Condition

Round-Tube and Microchannel Heat Exchanger Modeling at Wet Air Condition

ABSTRACT This paper discusses the modeling of round tube plate fin heat exchanger (RTPF) and microchannel heat exchanger (MCHX) under wet air conditions. The heat exchanger models are based on finite volume method. In each control volume, the empirical heat transfer and pressure drop correlations for refrigerant and air are adopted and the effectiveness-NTU method is applied for heat transfer calculation. For the round tube heat exchanger, the tube circuiting is considered. For microchannel heat exchanger, both uniform distribution and maldistribution among parallel microchannel tubes are investigated and compared. When the inlet air dew point temperature is higher than the heat exchanger surface temperature, dehumidification of air occurs. Two methods are compared to simulate the wet air condition: (1) the air side is simulated based on the total enthalpy method; (2) the air side is simulated based on heat and mass transfer method. The heat exchanger models are validated against the experimental results of a 2.5 ton residential air-conditioning system. The experiment was conducted based on AHSI/AHRI standard 210/240 at A, B (wet coils), and C (dry coil) conditions with either round tube evaporator or microchannel evaporator. The microchannel heat exchanger was tested at both direct expansion (DX) and flash gas bypass (FGB) conditions. The modeling results show good accuracy compared to the experimental results. The capacity errors are within ±10%.
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Experimental Study on Microchannel and Round Tube Plate Fin Evaporators in a Residential Air Conditioning System

Experimental Study on Microchannel and Round Tube Plate Fin Evaporators in a Residential Air Conditioning System

2472, Page 4 3. EXPERIMENTAL RESULTS 3.1 Air Side Pressure Drop Air-side pressure drop of two heat exchangers were measured under dry condition with the temperature around 26.7℃ (required by AHRI conditions) and various face velocity. Since RTPF A coil has 3 row staggered design, it has higher pressure drop than microchannel heat exchanger with 2 slabs design under the same face velocity. 0.42m 3 /s indoor air flow rate will be used for later experiments, which translates to 0.7m/s and 1.3m/s air velocity for RTPF and MC evaporators respectively. Through linear extrapolation, the pressure drops under this circumstance are 24.4 Pa for RTPF evaporator and 19.3 Pa for MC evaporator.
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Experimental Study on Heat Transfer and Flow Characteristics of Air Cooling through Cross-flow Microchannel Heat Exchanger

Experimental Study on Heat Transfer and Flow Characteristics of Air Cooling through Cross-flow Microchannel Heat Exchanger

number, and j factor increased with fin height where as little effect of fin height on f factor . They also proposed the correlations for heat transfer and pressure drop for wavy fins and these correlations can predict 95% of experimental results within ±10%. Tang et al. (2009) studied experimentally on air-side heat transfer and friction factor characteristics of five kinds fin–and–tube heat exchangers with 12 number tube rows and 18 mm outside tube diameter within the range of Reynolds number from 4000 to 10000.They found that crimped spiral fin showed the higher heat transfer rate and pressure drop compared with other four types fins. Park and Jacobi (2009) studied experimentally the air-side thermal-hydraulic performance of flat-tube aluminum heat exchangers with serpentine louvered, wavy, and plain fins maintaining the air face velocities from 0.5m/s to 2.8m/s for dry and wet surface conditions. They founded that the effect of fin spacing on j and f influenced the other fin design parameters at high Reynolds number in case of louver fin geometry, but fin spacing did not make any significant impact on j and f factor for wavy-fin tube heat exchangers.
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Experimental Study of Heat Transfer Rate in a Shell and Tube Heat Exchanger with Air Bubble Injection (TECHNICAL NOTE)

Experimental Study of Heat Transfer Rate in a Shell and Tube Heat Exchanger with Air Bubble Injection (TECHNICAL NOTE)

4. 1. Effect on the Heat Transfer Rate The quantity of heat transferred between hot and the cold fluid depicts the performance of any heat exchanger. The heat transfer rate takes place due to the difference of temperature between hot and cold side. From Equations (4) and (5), it has been observed that the more the temperature difference, the more will the heat transfer. From the experimental analysis, it has been observed that the heat transfer rate increases with the increase in the Reynolds Number. Injecting air at different points shown, enhances the heat transfer rate as compared to the situation without injection of air bubbles. Injecting air bubbles throughout the tube shows more enhancement as compared to the other methods due to the fact that the bubbles while rising up create a void which is filled by the nearby fluid. Earlier studies have proved that with more number of bubbles injected, higher heat transfer is obtained. So, injecting air throughout the tube increases the turbulence and hence carries more heat from the surface. Injecting air bubbles at the tube inlet along with water also enhances the heat transfer, but as compared to the previous case, it shows less enhancement. The reason behind this can be that the bubbles while rising creates more turbulence than the bubbles entering along with the water in the tube and injecting bubbles throughout the tube has more number of air bubbles than injecting at the tube inlet and thus less turbulence is created. Injecting air bubbles at shell inlet creates turbulence in the shell side and this enhances the heat transfer rate compared to the situation where no air is injected to any of the sides. From the results shown in Figure 2, it has been observed that injecting air bubbles throughout the tube enhances the heat transfer rate by 25-40% depending upon the Reynolds Number while injecting air at tube inlet enhances the heat transfer rate by 20-30% and injecting air bubble at the shell inlet enhances the heat transfer rate by 10-15% depending on the Reynolds Number (see Figure 4).
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Cfd Analysis Of Heat Transfer Rate In Tube In Tube Helical Coil Heat Exchanger

Cfd Analysis Of Heat Transfer Rate In Tube In Tube Helical Coil Heat Exchanger

[7] Genic Srbislav B., Jacimovic Branislav M., Jaric Marko S., Budimir Nikola J., Dobrnjac Mirko M., Research on the shell-side thermal performances of heat exchangers with helical tube coils, International Journal of Heat and Mass Transfer, vol.-55 (2012) 4295–4300. [8] Ghorbani Nasser., Taherian Hessam., Gorji Mofid., Mirgolbabaei Hessam., An experimental study of thermal performance of shell-and-coil heat exchangers, International Communications in Heat and Mass Transfer, vol.-37 (2010) 775–781.

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Performance of finned tube heat exchanger – Review

Performance of finned tube heat exchanger – Review

Another common configuration is the shell-and-tube heat exchanger . Specific forms differ according to the number of shell-and- tube passes, and the simplest form, which involves single tube and shell passes, is shown in Fig 4. Baffles are usually installed to increase the convection coefficient of the shell-side fluid by inducing turbulence and a cross-flow velocity component relative to the tubes. In addition, the baffles physically support the tubes, reducing flow-induced tube vibration. Baffled heat exchangers with one shell pass and two tube passes and with two shell passes and four tube passes are shown in Fig 5.a and Fig 5.b respectively. [4]
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Augmentation of Heat Transfer Using Twisted Tube Heat Exchanger

Augmentation of Heat Transfer Using Twisted Tube Heat Exchanger

transfer and friction characteristics for water, ethylene glycol and ISOVG46 turbine oil flowing inside four tubes with three dimensional internal extended surfaces and copper continuous or segmented twisted tape inserts within Prandtl number range from 5.5 to 590 and Reynolds numbers from 80 to 50,000. They found that for laminar flow of VG46 turbine oil, the average Stanton number could be enhanced up to 5.8times with friction factor increase of 6.5fold compared to plain tube. Betul Ayhan Sarac (Betul Ayhan Sarac et al., 2007)[29] conducted experiments to investigate heat transfer and pressure drop characteristics of a decaying swirl flow by the insertion of vortex generators in a horizontal pipe at Reynolds numbers ranging from 5000 to 30000. They observed that the Nusselt number increases ranging from 18% to 163% compared to smooth pipe. Experimental investigation on heat transfer and friction factor characteristics of circular tube fitted with right-left helical screw inserts of equal length and unequal length of different twist ratios was done by (Sivashanmugam et al., 2007)[30]. They observed that heat transfer coefficient enhancement for right left helical screw inserts is higher than that for straight helical twist for a given twist ratio. A maximum performance ratio of 2.97 was obtained by helical screw inserts. Heat transfer, friction factor and enhancement efficiency characteristics in a circular tube fitted with conical ring twisted tubes and a twisted-tape swirl generator were investigated experimentally by Promvonge (Promvonge et al., 2007)[31]. Air was used as test fluid. Reynolds number varied from 6000 to 26000. The average heat transfer rates from using both the conical-ring and twisted tape for twist ratios 3.75 and 7.5, respectively are found to be 367% and 350% over the plain tube. The effect of two tube insert wire coil and wire mesh on the heat transfer enhancement, pressure drop and mineral salts fouling mitigation in tube of a heat
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CFD ANALYSIS ON SHELL AND COILED TUBE HEAT EXCHANGER FOR HEAT TRANSFER AUGMENTATION DUE TO AIR BUBBLES INJECTION

CFD ANALYSIS ON SHELL AND COILED TUBE HEAT EXCHANGER FOR HEAT TRANSFER AUGMENTATION DUE TO AIR BUBBLES INJECTION

Heat Exchangers are available in many types of construction, each with its advantages and limitations. The main heat exchanger types are: Shell & Tube – The most common heat exchanger design type consists of a parallel arrangement of tubes in a shell. One fluid flows through the tubes and the other fluid flows through the shell over the tubes. Tubes may be arranged in the shell to allow for parallel flow, counter flow, cross flow, or both. Heat exchangers may also be described as having tube layouts in single pass, multi-pass, or U-tube arrangements. Due to its tubular construction, this type of exchanger can handle large pressures. The exchanger may have one or two heads on the shell and multiple inlet, outlet, vent, and drain nozzles.
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A Review Paper on Earth Tube Heat Exchanger

A Review Paper on Earth Tube Heat Exchanger

Abstract-The aim of this work is to investigate by modeling the possibility of reducing the operational energy of a typical house without negatively affecting its embodied energy. This is done through consideration of different building materials coupled with the use of an earth to air heat exchanger (EAHE) for fresh air supply and cooling.It is found that the use of an optimal wall configuration in each zone coupled with the EAHE results in 76.7% energy savings compared with the reference case with conventional cooling.A single pass earth-tube heat exchanger (ETHE) was installed to study its performance in cooling and heating mode. ETHE is made of 50 m long MS pipe of 10 cm nominal diameter and 3 mm wall thickness. ETHE is buried 3 m deep below surface. Ambient air is pumped through it by a 400 w blower.Air velocity in the pipe is 11 m/s. Air temperature is measured at the inlet of the pipe, in the middle (25 m), and at the outlet (50 m), by thermistors placed inside the pipe. Cooling tests were carried out three consecutive days in each month..
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Dynamic modeling of a heat exchanger

Dynamic modeling of a heat exchanger

The program PsxCad is continuously developing. During my internship a lot of changes have been made to improve the performance, stability and accuracy of the program. Regarding performance, model 1 is not useful as a model for the heat exchanger, the iterative calculations cost too much computational power. Model 2 is more suitable as an advanced heat exchanger model. Including the heat capacitance of the wall and the discretization of the heat exchanger in smaller elements lead to more stable and realistic results during the startup compared to the LMTD model. In the new model the number of initial values and process parameters is increased, the process parameters makes the setup of the process becomes more difficult. But on the other hand there a more possibilities to fine tune the process.
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Temperature Analysis of Shell and Tube Heat Exchanger

Temperature Analysis of Shell and Tube Heat Exchanger

With the advent of computers, design procedures have become sophisticated even though the basic design remains the same. Because it is possible to specify an infinite number of different heat exchangers that would perform the given service, one has to identify the specific heat exchanger that would do it to certain constraints. These constraints can be based on allowable pressure drop considerations either on shell side or tube side or both and usually include that of minimizing cost. The flow of experimental as well as simulation work carried out on the heat exchanger is mentioned in detail in section III.
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Failure Analysis of Tube and Shell Heat Exchanger

Failure Analysis of Tube and Shell Heat Exchanger

Abstract: This paper will present an over view on the different types failures occurring in heat exchangers and the maintenance procedure adopted for smooth operation of the heat exchanger. Heat exchanger is present as a static equipment at Hindustan Organic Chemicals Limited. The operation of this heat exchanger involves the production of Phenol from TAR COLUMN. The case study deals with the failure analysis of heat exchanger in which its design is checked. In HOCL, a shell and tube heat exchanger is used in the production line of phenol. Hot oil at 328°C and 10.5 kg/cm2 is passing through the exchanger tubes. SS316 material is used in the tubes. 120 tubes at the top of the heat exchanger fails regularly and hence the plant have to be closed down for at least 2 days on each failure. The failure causes loss of hot oil (therminol) which cost approximately Rs 850 per litre. About 1cm drop in oil level costs about 5 lakhs. In order to overcome this problem, the design of this heat exchanger is analysed for finding out the reason behind this failure.
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Review on Comparative Study between Straight Tube Heat Exchanger and Helical Coil Heat Exchanger

Review on Comparative Study between Straight Tube Heat Exchanger and Helical Coil Heat Exchanger

Abstract: The main purpose of this study is to determine the relative advantage of using a helically coiled heat exchanger over a straight tube heat exchanger. It is found that the heat transfer in helical circular tubes is higher as compared to Straight tube due to their geometrical shape. Helical coils offer advantages over straight tubes due to their compactness and increased heat transfer coefficient. The increased heat transfer coefficients are a consequence of the curvature of the coil, which induces centrifugal forces to act on the moving fluid, resulting in the development of secondary flow. The curvature of the coil governs the centrifugal force while the pitch (or helix angle) influences the torsion to which the fluid is subjected to. The difference in velocity sets-in secondary flows. The fluid particles flowing at the core of the pipe have higher velocities than those flowing near to the pipe wall. Thus the fluid particles flowing close to the tube wall experience a lower centrifugal force than the fluid particles flowing in the tube core. This causes the fluid from the core region to be pushed towards the outer wall. This additional convective transport increases heat transfer and the pressure drop when compared to that in a straight tube.
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Experimental Investigation of Heat Transfer and Flowing Resistance for Air Flow Cross over Spiral Finned Tube Heat Exchanger

Experimental Investigation of Heat Transfer and Flowing Resistance for Air Flow Cross over Spiral Finned Tube Heat Exchanger

Figure 2. Experiment system of heat transfer wind tunnel Experimental system is composed of air cycling system and cooling water cycling system. Air is pressured by blower 4, heated in electric heater 5, flows to test section, cooled by water in heat exchanger, flows back to blower 4 and forms cycling, air flow is adjusted by the valve 6. Water flows from the high water tank 1, pressured by pump 3, heated in the test section, flows back to water tank and form cycling, water flow is adjusted by the valve 2, cooling water flows inside of spiral finned tube, hot air flows outside of spiral finned tube. Air average temperature, outer diameter of tube is used as calculating parameters in the experimental data process.
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Experimental Investigation of U tube heat exchanger using Plain tube and Corrugated tube

Experimental Investigation of U tube heat exchanger using Plain tube and Corrugated tube

P. B. Borade, K. V. Mali had done comparative analysis made on CFD analysis and Thermal design of U-shaped heat exchanger tube. Kettle Re-boiler used u-shaped tubes in shell and tube heat exchanger. The construction of U-tube is done by SA 213 304 tubing. R22 and Chlorosilanes fluids flow across the shell and tube respectively. Thermal designing was done by Kern’s method to investigate heat transfer rate and pressure drop. A CFD ANSYS Fluent v12.1 has been used to investigate the pressure and temperature variation across U-tube. Comparison between thermal designing and CFD analysis shows that less pressure drop occurs across the tube while Temperature at inlet and outlet is maintained. [2]
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Air to Air Heat Exchanger with DX Coil Unit

Air to Air Heat Exchanger with DX Coil Unit

When you have noticed that some kind of trouble (such as when an error display has appeared, there is a smell of burning, abnormal sounds are heard, the Air to Air Heat Exchanger with DX Coil Unit fails to cool or heat or water is leaking) has occurred in the Air to Air Heat Exchanger with DX Coil Unit, do not touch the Air to Air Heat Exchanger with DX Coil Unit yourself but set the circuit breaker to the OFF position, and contact a qualified service person. Take steps to ensure that the power will not be turned on (by marking “out of service” near the circuit breaker, for instance) until qualified service person arrives. Continuing to use the Air to Air Heat Exchanger with DX Coil Unit in the trouble status may cause mechanical problems to escalate or result in electric shocks or other failure.
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Design and Development of Shell & Tube Heat Exchanger for Beverage

Design and Development of Shell & Tube Heat Exchanger for Beverage

In the first part of this paper, a simplified approach to design a Shell & Tube Heat Exchanger [STHE] for beverage and process industry application is presented. The design of STHE includes thermal design and mechanical design. The thermal design of STHE involves evaluation of required effective surface area (i.e. number of tubes) and finding out log mean temperature difference [LMTD]. Whereas, the mechanical design includes the design of main shell under internal & external pressure, tube design, baffles design gasket, etc. The design was carried out by referring ASME/TEMA standards, available at the company. The complete design, fabrication, testing and analysis work was carried out at Alfa Laval (India), Ltd., Pune-12. In the second part of this paper detail view of design optimization is presented by flow induced vibration analysis [FVA].
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Effectiveness Improvement of Shell and Tube Type Heat Exchanger

Effectiveness Improvement of Shell and Tube Type Heat Exchanger

ABSTRACT: Generally, 35-40% of the heat exchangers used in industries are shell and tube heat exchanger. Here an experiment on shell and tube type heat exchanger is conducted. There are problems like scaling, fouling, welding defects and maintenance cost. In this experiment, design of shell and tube type heat exchanger baffle is changed. Considering this design as the basis, effectiveness of shell and tube type heat exchanger is measured. Performance in terms of effectiveness is firstly measured for normal flat baffle having 3:2 cutting ratio. Then performance in terms of effectiveness is measured for helical baffle. After measuring the performance for both types of baffle, results of both experiments are compared. Also the turbulence gained due to helical baffle helps to reduce the fouling effect in the heat exchanger.
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Post Experimental Analysis of Tube-In-Tube Helical Coil Heat Exchanger

Post Experimental Analysis of Tube-In-Tube Helical Coil Heat Exchanger

used CFD tool ANSYS CFX 12.2 for finding out the temperature profile at various sections of single tube helical coil heat exchangers. He found that the variation in the temperature profile goes on increasing with increase in pitch of the coil. Resultantly, thermal loading on coil goes on increasing with increase in pitch. Also, he plotted pressure contour along the wall at fluid inlet velocity of 1 m/s. after doing such analysis he concluded that the helical coil with 60mm pitch is better as compared to coil with 30mm pitch with limitation in space and pressure drop. In this way, without actual conducting the experiment, the most economical heat exchanger can be designed and redesigned. J.S. Jaykumar [4] did the CFD analysis at constant wall temperature boundary condition
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Exergy of heat flows of the air to air plate heat exchanger

Exergy of heat flows of the air to air plate heat exchanger

The diagrams depicted in Figs. 3, 5 and 7 show the percentage distribution of the exergies of heat flows in the heat exchanger. At all values of κ the heat loss exer- gy ∆E accounts for the biggest portion. The measured values along with the computation results confirmed the conclusion arising from the equation (5). Not only does the heat loss exergy ∆E depend on the temperature gra- dient ∆t i,e1 = T i – T e , but it is also influenced by the level

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