Tube Rows Research Articles

Numerical Simulation of Heat Transfer Characteristics of Finned Tube Heat Exchanger at Different Flow Velocities

A heat exchanger is an important component where high-temperature hot air and normal-temperature water exchange heat. The heat exchange area of the finned tube heat exchanger is calculated by the rated working conditions. However, with the decrease of the heat storage temperature, the hot air temperature at the outlet of the thermodynamic energy storage device changes in a large range, directly affecting the heat exchange capacity and efficiency of the finned tube heat exchanger. This paper’s three-dimensional model is established. The heat exchanger of the finned tube is designed according to the temperature of the outlet section and the return section temperature of the heat storage system. The thermodynamic physical parameter property and characteristics of which heat exchanger’s finned tube in the air’s velocity range of 1∼10 m/s are simulated by fluent software. The velocity, temperature, pressure, and heat exchanger coefficient distribution characteristics at different positions along the airflow direction are obtained. The simulation results show that the mean flow velocity is 2.0 m/s and 5.0 m/s at the inlet cross-section. The average temperature difference between the inlet and outlet is 69.5 K and 100.5 K, respectively. The fin surface temperature difference between the first and eighth rows of finned tubes is 12.5 K and 14.4 K, respectively. The air pressure loss at the air channel inlet’s section and outlet’s section is 16.1 Pa and 69.4 Pa, respectively. When the inlet flow rate change from starting at 1.0 m/s and ending at 10.0 m/s, the tube’s wall coefficient of heat transfer, which is the second level of finned tubes, only increases by 1.8 times. The tube’s wall coefficient of heat transfer of the eighth level of finned tubes increases by the maximum, to 5 times the original, but the heat energy exchange capacity of which the second level of finned tubes is always the strongest.

Study on Heat Transfer Performance and Parameter Improvement of Gravity-Assisted Heat Pipe Heat Transfer Unit for Waste Heat Recovery from Mine Return Air

One of the effective methods for energy conservation and emission reduction in coal mines is to utilize waste heat recovery technology to recover mine return air waste heat. The gravity heat pipe is widely used in mine return air waste heat recovery due to its sustainable and economic advantages, but its heat transfer is a complex process influenced by multiple parameters. A single-tube heat transfer resistance model and a heat transfer calculation model based on enthalpy difference were established for the heat exchange tubes. Four typical application cases of a low flow rate and a low number of tube rows were selected, and their heat transfer characteristics were tested onsite and analyzed. It was found that there were problems such as a low overall heat transfer efficiency, a low fresh air outlet temperature, and a risk of icing in the final tube section. The effects of the gravity heat pipe parameters on the heat transfer performance were studied, such as the tube outer diameter, tube spacing, and the finned tube outer diameter. It was found that the air-resistant force of the heat exchanger increased with the increase of the tube spacing and the finned tube outer diameter, the heat transfer resistance increased with the increase of the tube spacing and the decrease of the finned tube outer diameter, and the heat transfer coefficient first increased and then decreased with the increase of the tube outer diameter. A configuration improvement scheme with a high flow rate and a high number of tube rows is proposed here. Taking Case 2 as an example, the temperature distribution of the heat tube before and after improvement is compared and analyzed. The results show that the heat transfer performance of the heat exchange system significantly improved. Without increasing the air resistance of the heat tube, the temperature of the return air outlet after improvement was reduced to 1.1 °C, 4.1 °C lower than that before improvement, further recovering the waste heat of the mine return air. The temperature of the condensate water film was greater than 0.5 °C, avoiding the icing problem of the condensate tube section, the fresh air outlet temperature reached 5.2 °C, an increase of 7.8 °C compared to that before improvement, and the overall heat transfer efficiency increased from 56.7% to 66%.

Fluid-elastic Instability Effect of Groove Cylinder in Heat Exchanger

The fluidelastic instability impact of groove cylinders in heat exchangers are investigated in this study, and explores associated phenomena of flow-induced vibration and fluidelastic instability. The primary focus is on investigating the performance of various rows of tubes in the tube bundle, with a particular emphasis on the largest instability identified in the third row. The analysis also considers the impact of a triangular arrangement of tubes within the tube bundle. The addition of groove tubes in the heat exchanger proved to greatly delay the onset of fluidelastic instability, lowering the possibility of flow induced vibration. Despite the improved impact of groove cylinders, the study found that the third row of tubes in the tube bundle had a higher degree of instability than the other rows. This result emphasizes the significance of tube location and arrangement throughout the design phase in reducing fluidelastic behavior. Overall, this study shows that groove tubes may delay fluidelastic instability and reduce the frequency of flow-induced vibration in heat exchangers. The design may significantly improve the operating efficiency and reliability of the heat exchanger by using groove cylinders and carefully studying tube designs and optimize heat exchanger performance.

Experimental Analysis of Flow Induced Vibrations in Heat Exchanger Tube Bundles with P/D of 1.54 Subjected to Crossflow

This paper presents an experimental analysis of flow-induced vibrations in a heat exchanger tube bundle subjected to crossflow. The study focuses on the characterization and insights gained from the investigation. The tube bundle configuration consists of plain tubes with a single flexible tube, arranged in a squared pattern. The primary objective is to assess the flow-induced vibration behavior and identify any potential instabilities within the system. To analyze the flow-induced vibrations, various parameters were considered, including the P/D ratio (tube pitch to tube diameter ratio), which was found to be 1.54. The experiments were conducted under different flow velocities, and the vibration responses of the tube bundle were measured using suitable sensors. The results revealed that the third row of tubes in the bundle exhibited the highest level of instability compared to the other rows. This finding suggests that the positioning of the tubes within the bundle significantly influences the flow-induced vibrations. The vibrations were observed to vary with the flow velocity, indicating a strong fluid-structure interaction. It can be concluded that the squared arrangement of tubes in the tube bundle, along with the specific P/D ratio, contributes to the flow induced vibration characteristics. Understanding these effects is crucial for optimizing the design and operation of heat exchanger systems, as excessive vibrations can lead to mechanical failures and reduced heat transfer efficiency.

Analysis of factors affecting the performance of a novel micro-channel heat pipe PV-Trombe wall system for space heating

Building energy consumption accounts for about 1/3 of the world's total energy consumption. Photovoltaic Trombe wall (PV-TW) is an effective way to reduce a building's energy consumption, but it still has disadvantages such as low energy efficiency and uneven indoor temperature distribution. To address these issues, a novel system with a PV-TW and a micro-channel heat pipe (MCHP) was initially presented in this research. By cooling the PV cell with both air and refrigerant, the system can reduce its surface temperature and improve its electrical performance. To promote thermal performance and user comfort, an air-cooled condenser is also employed to regulate the room's heat transfer. This paper establishes the system's dynamic mathematical model for winter and theoretically evaluates its performance. Besides, the key factors influencing the system’s performance were examined. In winter, the total power generation and average daily electrical efficiency are 3.12 MJ and 13.52%, respectively, with a maximum indoor temperature of 21.46 °C and a daily average thermal efficiency of 56.76%. The system’s performance is all improved with the incremental change of the factors besides the size of the micro-channel flat tube (MAFT), and the performance is not sensitive to the change of the air channel width. The optimal number and width of the MAFT in the evaporator section are 11 and 45 mm. The indoor air-cooled condenser should have about 10 rows of tubes and an ideal air volume of 540 m3/h. The recommended airflow channel thickness is between 5 cm and 10 cm.

Experimental investigating the thermal and hydraulic performance of heat exchangers with helix wire finned tube

In this study, the helix wire finned tube is introduced as a novel design to increase the performance, reduce weight, and manufacturing price of the heat exchangers. The helix wire fin can make turbulence in the fin-side flow, creates a larger contact surface, more flow trapping and increment in the residence time for enhancement of the heat transfer. The effect of Reynolds number inside and outside of the finned tube and inter-tube distance on the thermo-hydraulic performance of the heat exchanger has been investigated experimentally. The results show that increasing the Reynolds outside the finned tube causes an 80% enhancement in the performance evaluation criterion of the heat exchanger. Also, helix wire finned tubes provide a maximum of 65% and 57% better thermal performance compared to spiral and serrated fins. Increasing the Reynolds number of the outside and inside tube flow causes a 40% and 50% enhancement in the Nusselt number of the fin-side flow, respectively. Moreover, increasing the longitudinal distance between the tube rows reduces the Nusselt number and friction factor of the fin-side flow by 20% and 45%, respectively. Finally, an experimental correlation is derived to calculate the Nusselt number of the air-side flow.

Research on the heat transfer performance of an improved elastic tube bundle heat exchanger under fluid-induced vibration

The heat transfer performance (HTP) of an improved elastic tube bundle (IETB) was analyzed using a bi-directional fluid-structure interaction calculation method. The vibration-enhanced HTP of heat exchangers with different inlet velocities (Uin) and row number N were studied. The results show that the amplitude gradually increases as the Uin increase with a maximum increase of 309.98%. The amplitude with fixed shell side length (FL-heat exchanger) is generally higher than that with variable shell side length (VL-heat exchanger) under different row numbers. The average amplitude of the three directions increased by 4.55%, 11.54%, and 7.41%, respectively. The heat transfer coefficient (h) is directly proportional to Uin, and the comprehensive HTP gradually decreases with the increase of Uin. With the increase in the row numbers, h generally showed a downward trend. For the VL-heat exchanger, h decreases as the row number increases, which increases from N=6 to N=9, and h decreases by 13.85%. For the FL-heat exchanger, h first increases and then gradually decreases. The comprehensive HTP also maintained the same trend. Compared VL-heat exchanger and FL-heat exchanger, reducing the spacing between tube rows increases heat transfer per unit volume, leading to improved comprehensive HTP of the IETB heat exchanger.

Numerical investigation of water and heat recovery from flue gas by using nanoporous ceramic membrane tubes

Direct emission of high humidity flue gas results in great wastage of water and thermal energy. Ceramic membrane technology has been widely regarded as a potential technology for water and heat recovery from flue gas. This study presents numerical investigations of water and heat recovery processes from flue gas by using nanoporous ceramic membrane tubes (CMTs). A comprehensive mathematical model is developed based on the Kelvin equation, and the Hagen–Poiseuille equation is applied to calculate the bilateral pressure difference needed for continuous recovery operation. Decreasing the pore size of the separation layer of the ceramic membrane improves the capillary condensation flux but also drastically increases the required bilateral pressure difference. CMT with a pore size of 20 nm is appreciated for the studied conditions. The performances of the CMTs located in the last rows along the flow direction are limited by local low gas temperature and humidity. Twelve rows of tubes are suggested to be arranged along the gas flow direction for ceramic membrane devices with pore sizes of 20 nm and higher. A low transverse spacing obviously improves the overall water and heat recovery efficiency of the device, decreases the performance of each tube, and enhances the gas flow resistance. A transverse spacing ratio of less than 1.4 is suitable for the studied conditions. A combined arrangement by substituting the tubes located in the last rows with those of smaller pore size is a better method than using uniform tubes. The device with combined 20 and 10 nm CMTs is suggested for the studied conditions.

CFD simulation and optimization of turning different waste gases into energy in an industrial steam methane reformer

BackgroundOne of the most important processes of industrial hydrogen production is steam methane reforming (SMR). However, the biggest drawback of steam reformer processes is high energy consumption. In methanol production units, 40% of the energy consumed in the steam reformer is provided by methane burning. The best solution to reduce the consumption of methane gas is to use the waste gases of the units. InnovationTo boost the thermal performance of the furnace, as well as the reduction in natural gas utilization, the effects of the kinds of fuel in an industrial unit are investigated. Furthermore, the waste gas is studied to whether it can be used as fuel in an SMR or not. SignificanceCFD is one of the most powerful tools for simulation of the industrial by which a new unit can be set up or the performance of the old units can be developed. Additionally, the effect of diverse parameters on industrial processes can be examined, and the optimal operating conditions of the industrial unit can be found. MethodsIn this study for five different cases of fuel, the furnace of an industrial SMR unit, at the operating conditions, was simulated using Computational Fluid Dynamics, (CFD) and the results were validated by the industrial data. Moreover, regarding the higher thermal efficiency of the furnace and the lower consumption of natural gas, two cases called design, and the suggested modes, were investigated and suggested mode was proposed as the most suitable fuel. FindingBased on the results, removing purge gas and adding waste gases with lower hydrogen content are recommended. Compared with the operational fuel, the suggested mode decreases the flue gas temperature by 11.78 K and increases the temperature of the first row of the reformer tubes by about 4.17 K, while declining the natural gas molar flow rate by 32%. A 64% reduction in hydrogen content of the suggested mode leads to an increase 10% flame length and 14% enhancement of adsorbed radiative heat flux. Moreover, in the suggested mode it is possible to recycle the purge gas to the methanol synthesis reactor and enhance the methanol production to 1% which is 50 ton/day.

Thermodynamic assessment and optimization on louver fin with non-uniform arrangement at different tube rows by desirability approach

The parametric study explores the thermodynamic performance of louver fin with non-uniform arrangement at different tube rows based on three factors: Reynolds number (Re), number of slotted at first tube row (Ns1), and number of slotted at second tube row (Ns2). The distributions of local entropy generation are displayed and analyzed in detail. Thermal entropy generation is mainly concentrated in the first row, but the viscous entropy generation of the first row is roughly the same to the second row. Compared with plate fin, the louver fins can effectively reduce thermal entropy generation, but also bring greater viscous entropy generation at variable Re. The thermal entropy generation and viscous entropy generation increase, but the thermal entropy generation per unit mass flow decreases and the viscous entropy generation per unit mass flow increases as the increasing Re. It is found that the increase in Ns1 will lead to a far greater improvement in thermal performance than the increase in Ns2. However, the increase in resistance caused by the increase in Ns1 is approximately equal to the increase in resistance caused by the increase in Ns2. Meanwhile, the correlations of the thermal performance and resistance are given, which facilitates the design of the heat exchanger. The non-uniform arrangement is quantitatively optimized using the desirability approach, and the arrangement of first-dense-then-sparse at Re = 900, Ns1 = 8, Ns2 = 4 is given. The arrangement of first-dense-then-sparse can reduce the resistance without reducing the thermal performance evidently.

Experimental evaluation of the performance of newly designed tubular SAH with infinity (∞) shaped inner tubes

A new design of tubular solar air heater (SAH) is examined experimentally in this work. The SAH absorber consists of one row of adjacent equal tubes forming flat pack. Each tube contains two adjacent inner tubes, the diameter of each of which equals the radius of the outer tube. The two inner tubes form the shape of infinity (∞), therefore, the new design is expressed as infinity shaped tubular SAH (∞TSAH). The performance of the ∞TSAH is examined against ordinary tubular SAH (OTSAH)) having tubular absorber consists of one row of only adjacent equal tubes. The comparison is performed at different mass flow rates of the air (MFRs) and under single pass flow (SPF) and double pass flow (DPF) of the air. The findings show clearly that the output air temperature, energy efficiency and thermohydraulic efficiency, of ∞TSAH are better than that of OTSAH. The maximum output air temperature rise is about 47.1 °C and 37.1 °C for ∞TSAH and OTSAH, respectively at MFR of 0.017 kg/s and DPF condition. In addition, the ∞TSAH achieves maximum energy efficiency of 84.5% at MFR of 0.079 kg/s and DPF condition with percentage increment of 8.4% relative to OTSAH which achieves energy efficiency of 77.3% at the same condition. Moreover, the ∞TSAH achieves maximum thermohydraulic efficiency of 79% at MFR of 0.052 kg/s and DPF condition, while OTSAH achieves a value of 72.6% at MFR of 0.079 kg/s and DPF condition.

Simulation research on corrosion and thinning characteristics of water wall tubes based on electric field array

During service, the water wall tube will inevitably corrode due to various corrosive gases such as SO2, HCl, H2S, etc. To prevent the occurrence of tube burst accidents caused by thinning and income-pressure resistance of the water wall tube, it is necessary to monitor the wall thickness of the water wall tube row in real-time. This paper proposes an array-based method for monitoring the thickness of the water wall tube row, and the different corrosion characteristics models of the water wall tube row are established by using the finite element analysis software Maxwell. Based on the model, the influence of tube wall thickness and material on measurement accuracy is analyzed by current density distribution and electric field intensity. The error of calculation formula is analyzed by simulating different corrosion conditions of tube wall thinning. The calculation formula of the wall thickness after the corrosion of the water wall tube row and the correction formula of the wall thickness of a single water wall tube with the correction coefficient α of 3 are determined. And put forward to define the ”generalized average thickness” of the water wall corrosion of multiple tubes, and determine the correct formula for calculating the thickness of the water wall tube row with a correction coefficient β of 0.85 to 0.95.

Numerical analysis of vibration response of elastic tube bundle of heat exchanger based on fluid structure coupling analysis

Abstract A tube bundle heat exchanger is a typical heat exchange equipment that exchanges heat between two fluids with different temperatures. Through this equipment, one fluid can be cooled down and another fluid can be heated up to meet their respective needs. The equipment is widely used in chemical, petroleum, pharmaceutical, energy, and other industrial sectors, and is one of the indispensable and important equipments in chemical production. To improve the heat transfer performance and service life of the heat exchanger, a numerical analysis of the vibration response of the elastic tube bundle in the heat exchanger based on fluid–structure coupling analysis is proposed. Using the weak coupling method of fluid–structure coupling, the vibration response of multiple rows of elastic tube bundles induced by shell side fluid in a heat exchanger with different tube row spacing and different tube row numbers is studied numerically, and the effects of shell side fluid and tube side fluid on the vibration response of elastic tube bundles are compared and analyzed. The results show that the maximum relative error of monitoring point amplitude is 43.36% when H = 40 mm and 10.17% when H = 70 mm. For connection IV, the maximum relative error of monitoring point amplitude is 31.71% when H = 40 mm and 24.08% when H = 70 mm. This is because when H is small, the interaction between rows of tube bundles is strong, so the amplitude changes violently with the number of the tube bundle. The step-by-step calculation strategy of rough calculation and actuarial calculation proposed in this article can greatly reduce the calculation time and improve the calculation efficiency.

Effect of Tube Rows on Two-Phase Heat Transfer Characteristics of Water Over Staggered Tube Bundles Under Flow Boiling Mode

Abstract Tube bundles are an integral part of the two-phase heat exchangers and are employed in numerous commercial applications. Present research compares two kinds of horizontal staggered tube bundles under upward crossflow boiling to see how tube rows affect the heat transfer coefficient (HTC). The experimental setup developed houses the tube bundle for temperature measurements and facilities the recording of high-speed images at different operating conditions. The investigation is carried out for heat fluxes of 10–75 kW/m2, mass fluxes of 20–100 kg/m2s, and P/D ratios of 1.25, 1.6, and 1.95, with distilled water as the working fluid. It is observed that both tube bundles show an increase in overall HTC with an increase in heat flux. However, the 5 × 3 tube bundle resulted in a greater heat transfer rate as compared to the 2 × 3 tube bundle due to the bundle effect. Further, both tube bundles have a diminishing trend of HTC with a rise in mass flux. The rate of rising in HTC was found to decrease with an increase in the number of tube rows in the tube bundle and with an increase in the P/D ratio. Therefore, interestingly it is observed that the increase in bundle average HTC of 5 × 3 tube bundle is not twice that of 2 × 3 tube bundle rather it is quite lesser which further deteriorates with an increase in P/D ratio. The row-wise and bundle average HTC obtained is also predicted with a dimensionless correlation within an error of ± 15%.

A general correlation for flat tube-and-fin radiator based on parametric CFD analysis

The work numerically predicted a Fin-and-flat tube heat exchanger with an experimental validation. The unit was firstly redefined as five basic modules. Based on L9(34) orthogonal tests involving vertical fin spacing, horizontal tube spacing, fin length, and fin thickness, the formed overdetermined equations were solved and discussed by regression and F significance test. After a derivation, the general correlation was compared with published, fitted, and numerical results. Finally, its applicable range was numerically clarified. It is found that the maximum 3.62% error of heat transfer coefficient and 4.51% error of pressure loss, respectively. The fitted correlation can predict over 88.9% of j under 3.10% average error and 96.30% of f under 2.33%. 2.6-4.0 mm vertical spacing, 16-100 mm fin length, 5-8 mm horizontal spacing, 0.03-0.09 mm fin thickness, 3-4.4 mm hydraulic diameter, 1-5 tube rows, and Reynolds number of 550-3290 might work for the efficient deployment of the general correlation.

Numerical analysis of tube arrangements with one, two, and four degrees of freedom for heat transfer with pseudoplastic fluids

The association of the Constructal Design Method and Response Surface Methodology was used to investigate the best configuration of tube arrangements for heat transfer with pseudoplastic fluids, aiming to maximize heat transfer density. Systems consisting of a row of tubes and additional smaller tubes were analyzed. The problem consisted of three cases, characterized by one, two and four degrees of freedom. The effect of the sizes of the additional cylinders and the distances between cylinders were investigated. The systems were modeled and solved with Computational Fluid Dynamics (CFD). The power-law model was employed to predict the viscosity of Newtonian and pseudoplastic fluids. An open-source code was used to design the experiments by the Central Composite Design method and to adjust the Response Surfaces via polynomial regression. Considering both Newtonian and pseudoplastic fluids, the results showed that the heat transfer density was highly dependent on the distance between cylinders and that most pseudoplastic fluids had higher performance in terms of heat transfer density. The optimal configurations differed considerably for non-Newtonian fluids – as the pseudoplasticity increased, the geometry tended to be more packed, lower spacing and bigger cylinders. Adding degrees of freedom allowed the system to evolve to increase the heat transfer density, guaranteeing the best performance compared to simpler designs.

Numerical Modelling of Steam Superheaters in Supercritical Boilers

This paper presents a numerical model of a four-pass supercritical steam superheater with a complex flow system. The specific heat of steam is a function of temperature and pressure, and the specific heat of flue gas is a function of temperature. Pressure and temperature changes along the length of the tubes were also determined. The modified Churchill equation was used to calculate the steam-side friction factor of Darcy–Weisbach. The flue gas temperature variations behind the individual superheater tube rows were calculated. The steam and wall temperature distributions were determined in each tube row along its length. Knowing the temperature of the tube walls and the steam along the flow direction enables the selection of the correct steel grade for the tubes. Thanks to this advantage of the proposed method, the investment can be reduced in superheater construction without the danger of overheating the tube material. The results of the superheater simulation were compared with the results of measurements on the actual object. The proposed numerical method can find application in steam superheaters’ design and performance calculations. It can also be used to monitor superheater operating parameters, which are difficult to measure due to the high flue gas temperature.

Dropwise and liquid-jet laminar flow of subcooled water falling over horizontal tube banks

Falling-film heat exchangers are widely used to promote heat and mass transport within industrial environments. In contemporary condensers, for example, liquid films continuously form over a tube row and impact multiple tubes beneath, resulting in a rich variety of two-phase flow phenomena, including the classical Rayleigh-Plateau instability. It is widely known that altering the contact angle of the tubes influences the heat exchangers’ heat and mass transfer characteristics by changing the falling films’ flow behaviour (i.e. dropwise or jet). Therefore, resolving interfacial flow characteristics, such as the Rayleigh-Plateau instability, is crucial for falling film studies as this instability may change the state of the falling film from being jet flow to dropwise/jet flow or even just dropwise. To explore this aspect, three-dimensional direct numerical simulations are used in the present work to replicate the jet instability behaviour. By employing certain mesh refinement strategies demonstrated from various case studies, the interfacial flow behaviour and jet instability have been captured, showing good agreement with experimental and theoretical data previously published. This is determined from the increased jet bifurcation and a maximum error of 2.2% of the film thickness in comparison to Nusselt's result within the bulk region of the tube. In addition, the average and local heat transfer coefficients across the first tube were compared with numerical solutions to give an average error of 3.2 and 14 %. Jet instability is found to be directly related to the amplitude of the axial pressure variations which is augmented by the growth rate of the capillary wave that travels upstream. Specifically, for contact angles of 30 and 60°, the flow is in a dropwise and dropwise/jet state due to the emergence of the Rayleigh-Plateau instability. Notably, the additional satellite droplets that materialize from the unstable jet lead to an increase in the local heat transfer coefficient of the film compared to without the Rayleigh instability improvement.

Numerical study of the cold finned-tube bundle heat exchanger under natural convection for a novel passive displacement cooling system

In a passive displacement cooling (PDC) system, conventional finned-tube heat exchangers are being employed and their performance is not optimal under natural convection. In this study, an experimental set-up has been established to validate the numerical model for finned-tube heat exchanger optimization under natural convection. The numerical difference between the predicted and measured data is less than 3.4%, showing that the numerical model could predict the heat transfer and flow rate accurately under natural convection. Subsequently, the effects of fin spacing, coil configuration, tube row number, and fin depth on the coil performance under natural convection have been investigated. The results show that the one-row coil performs better than the two-row coil for a PDC system with 8-10 fins per inch (FPI), despite the smaller heat transfer area. Compared with the conventional two-row circular-tube coil with 10FPI, the one-row circular-tube coil improves the mass flow rate and heat transfer rate by around 29.1% and 20.0% respectively. The findings enable a more responsive and energy-efficient PDC system for green buildings.

Adapting a slit model to determine the aeroacoustic response of tube rows

Cylindrical tubes in cross-flow, like the ones found in heat exchangers, are excellent acoustic dampers and as such have the potential to mitigate thermoacoustic instabilities. Flow separation and vortex shedding downstream of the tube row are key to significantly enhancing sound attenuation. However, constructing an analytical solution for the aeroacoustic response of tube rows in cross-flow is very challenging owing to the complex flow structure, vortex shedding and coupling with acoustics. To overcome this, we propose the adaptation of a slit model for tube row acoustic scattering (aeroacoustic response) predictions at low Strouhal numbers. The slit model was modified such that the loss coefficients across the slit and the tube row matches. The model is then validated against numerical predictions using Linearised Navier Stokes Equations and experimental measurements. The predictions for both magnitude and phase for transmission and reflection coefficients agree well with the simulations and experiments.