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A mathematical model of the plate-fin heat exchanger filled with catalyst (CFPFHX) is established to investigate the continuous cooling process coupled with ortho-para hydrogen conversion at 42–70 K. The flow and heat transfer performance and the efficiency of ortho-para hydrogen conversion in the CFPFHX are quantitatively evaluated, and the effects of the structural parameters on the flow and heat transfer coupled with ortho-para hydrogen conversion are analyzed. The results show that the Elovich model is the best existing kinetic models of ortho-para hydrogen conversion with an average relative deviation of 1.8%. The Colburn heat transfer factor (j factor) of the hot side of the CFPFHX is 4.3 times that of the plate-fin heat exchanger (PFHX), and the thermal enhancement factor (TEF) of the hot side is 37.7% of that of the PFHX. Meanwhile, for the CFPFHX, the j factor and the TEF of the hot side under different structural parameters are always about 8–10 times and 68%–93% of that of the cold side respectively. Therefore, the CFPFHX can ensure the flow and heat transfer performance and realize the ortho-para hydrogen continuous conversion. And a fin with the larger flow area (high fin height, wide fin spacing and small fin thickness) has a better flow and heat transfer performance and ortho-para hydrogen conversion. The outlet para-hydrogen ratio youtp-H2 and the mass space velocity vm in the CFPFHX have an approximate linear trend. When mass space velocity vm ≤ 0.6589 kg/(m3·s), the outlet para-hydrogen ratio youtp-H2 can meet the requirement at 42–70 K. Above all, the mechanism of flow and heat transfer coupled with ortho-para hydrogen conversion is revealed for the first time in this study, which can provide a theoretical guidance for the application of the integrated technology in large scale hydrogen liquefaction process.

As the pressure drop and pump power increase with the enhancement of heat transfer, it is of great value to investigate the comprehensive performance of the heat exchanger based on common accurate correlations of heat transfer and flow friction. This paper adopts a generalized air-side thermal-hydraulic correlation to study the comprehensive performances of the plate fin heat exchanger with wavy fins. To better understand the fin characteristics, performance indexes under the same flow rate, pressure drop and pump power are employed to estimate the comprehensive flow and heat transfer performances. The nonlinear optimization problem is established in consideration of the multiple independent variables with the maximum effectiveness or the minimum modified entropy generation number as the optimization objective function, which is solved by the genetic algorithm. Comparative analysis is conducted for results obtained from the parametric analysis and heat exchanger optimization, indicating that the objective function of the modified entropy generation number is effective for the design optimization of the comprehensive performance.

This study experimentally investigated the evaporation heat transfer and two-phase flow characteristics of a vertical upward flow using R1234ze(E) and R32 as test refrigerants in a plate-fin heat exchanger with offset fins. The adiabatic and evaporation flows of R1234ze(E) were visualized using a high-speed camera. Owing to the asymmetry of the inlet and outlet of the channel, a non-uniform velocity profile in the channel-width direction was observed under both adiabatic and evaporation flows. Evaporation flow accompanied by nucleate bubble generation at the lower area of the channel and the occurrence of a dry area at the upper side of the channel were observed. The heat transfer coefficients of R1234ze(E) and R32 were measured, and the effects of mass flux, quality, and heat flux on heat transfer were clarified. The heat transfer was strongly affected by forced convection at higher mass fluxes and qualities whereas nucleate boiling dominated at higher heat fluxes and lower qualities. The difference in the heat transfer characteristics at local positions in the channel was also investigated by measuring the local wall temperatures. Comparing refrigerants, the heat transfer coefficient of R32 was higher than that of R1234ze(E), regardless of the mass flux and quality, especially at lower mass flux conditions.

This study investigates the issues involved in the design of a compact two-phase thermosyphon in which the locations of evaporator and condenser need a high degree of freedom. Enhancement of boiling heat transfer in the compact evaporator space was achieved by a microfabricated structure. Anticipating situations where gravity does not provide sufficient potential to drive the condensate, a pump-assisted circulation loop was studied. The relative height between the evaporator and condenser and the pumping rate were systematically varied by utilizing two thermosyphon loops. Close examination of the data suggests that there could be an optimum point in the parametric domain where the thermal resistance is minimized with least assistance from the pump.

Heat transfer can be intensified in shell-and-tube heat exchangers for improved heat transfer performance. Such intensification has been widely studied from the point of view of individual heat exchangers (HEs). The use of heat transfer enhancement in Process Integration has many benefits. First, enhanced heat exchangers require less heat transfer area for a given heat duty because of higher heat transfer coefficients. Second, the heat transfer capacity for the given HE can be increased without changing physical size of the exchanger. Third, the use of enhancement can reduce pumping requirement in some cases, as enhanced HE can achieve higher overall heat transfer coefficients with lower velocities, which may lead to lower friction losses. Using enhancement techniques has practical advantages in Heat Exchanger Network (HEN) retrofit, as it can avoid modification of the network structure. The implementation of enhancement is a relatively simple task that can be easily achieved within a normal maintenance period, allowing production losses to be kept to a minimum level and no civil engineering requirement. This chapter provides an introduction to the enhancement methods of commercial shell-and-tube heat exchangers and their engineering application. The key aspects of enhancing shell-and-tube heat exchangers in HEN retrofit are presented and illustrated with examples involving both energy saving and fouling considerations.

Fluid inhomogeneous distribution affects heat transfer efficiency in the plate-fin heat exchanger (PFHE). In order to improve fluid uniform distribution in the exchanger, the irregular-shaped hole leading flow structure (IHLFS) was proposed for solving fluid inhomogeneous distribution among different layers of PFHE. The inlet distributor with irregular-shaped holes was designed according to different inlet flow velocities aiming at improving fluid uniform distribution. The results on fluid flow and heat transfer characteristics were carried out by the methods of CFD and experimental analysis, and finally, the fluid flow characteristics in inlet section of PFHE with IHLFS were achieved. Comparing with round hole leading flow structure (RHLFS), it can be observed that fluid distribution in PFHE with IHLFS is more uniform than that with round hole, however, the dynamic pressure increases accordingly and finally, increases the ratio of heat transfer and dynamic pressure. The comparison results also demonstrate that the IHLFS can improve fluid distribution, decrease fluid impact in inlet section of PFHE and finally, improve heat transfer enhancement.

This paper uses a multi-objective topology optimization method for thermal-fluid problems applied to the design of fins for primary use in plate-fin heat exchangers. The presented method was derive...

Plate-fin heat exchangers provide a broad range of applications in many cryogenic industries for liquefaction and separation of gasses because of their excellent technical advantages such as high effectiveness, compact size, etc. Correlations are available for the design of a plate-fin heat exchanger, but experimental investigations are few at cryogenic temperature. In the present study, a cryogenic heat exchanger test setup has been designed and fabricated to investigate the performance of plate-fin heat exchanger at cryogenic temperature. Major parameters (Colburn factor, Friction factor, etc.) that affect the performance of plate-fin heat exchangers are provided concisely. The effect of mass flow rate and inlet temperature on the effectiveness and pressure drop of the heat exchanger are investigated. It is observed that with an increase in mass flow rate effectiveness and pressure drop increases. The present setup emphasis the systematic procedure to perform the experiment based on cryogenic operating conditions and represent its uncertainties level.

Plate fin heat exchanger is a kind of smaller heat exchange device which has applications in cars, low temperatures, rockets space vehicles etc. The plate fin heat exchanger devices are mostly utilized for liquefaction of nitrogen. So that they are highly efficient because no liquid oxygen will be produced if the efficiency of the system is below the required value, and that is nearly 87%. That’s ‘why it is very necessary to check their efficiency before bringing them in actual application. This efficiency has been calculated here. The required heat exchanger has different shape and its effectiveness is tested experimentally in the heat and mass transfer lab. Experiment is carried out by putting the Quantity of hot and cold fluid same, but the result is obtained by taking different quantity of fluid for different experiment. It means that for one test quantity of both the fluid is taken same and this test is repeated for different quantity. So, in this way productiveness of the required exchanger is determined for different quantity.

The plate-fin heat exchanger has been widely applied in the field of air separation and aerospace due to its high specific surface area of heat transfer. However, the low heat transfer efficiency of its plate bundles has also attracted more attention. It is of great significance to optimize the structure of plate-fin heat exchanger to improve its heat transfer efficiency. The plate bundle was studied by combining numerical simulation with experiment. Firstly, according to the heat and mass transfer theory, the plate bundle calculation model of plate-fin heat exchanger was established, and the accuracy of the UDF (User-Defined Functions) for describing the mass and heat transfer was verified. Then, the influences of fin structure parameters on the heat and mass transfer characteristics of channel were discussed, including the height, spacing, thickness and length of fins. Finally the influence of various factors on the flow field performance under different flow states was integrated to complete the optimal design of the plate bundle.

Purpose The purpose of this paper is to present a novel and applied method for optimum designing of plate-finned heat exchanger network. Considering the total annual cost as the objective function, a network of plate-finned heat exchanger is designed and optimized. Design/methodology/approach Accurate evaluation of plate-finned heat exchanger networks depends on different fin types with 10 different geometrical parameters of heat exchangers. In this study, fin numbers are considered as the main decision variables and geometrical parameters of fins are considered as the secondary decision variables. The algorithm applies heat transfer and pressure drop coefficients correction method and differential evolution (DE) algorithm to obtain the optimum results. In this paper, optimization and minimization of the total annual cost of heat exchanger network is considered as the objective function. Findings In this study, a novel and applied method for optimum designing of plate-finned heat exchanger network is presented. The comprehensive algorithm is applied into a case study and the results are obtained for both counter-flow and cross-flow plate-finned heat exchangers. The total annual cost and total area of the network with counter-flow heat exchangers were 12.5% and 23.27%, respectively, smaller than the corresponding values of the network with cross-flow heat exchanger. Originality/value In this paper, a reliable method is used to design, optimize parameters and the economic optimization of heat exchanger network. Taking into account the importance of plate-finned heat exchangers in industrial applications and the complexity in their geometry, the DE methodology is adopted to obtain an optimal geometric configuration. The total annual cost is chosen as the objective function. Applying this technique to a case study illustrates its capability to accurate design plate-finned heat exchangers to improve the objective function of the heat exchanger network from the economic viewpoint with the design of details.

The cold box, which comprises of several plate-fin heat exchangers (PFHE), is largely utilized in different industries. In this research, the computational fluid dynamics (CFD) technique has been used for investigating the impact of different fluid distributors on the rates of heat and mass transfer, in an industrial complex cold box equipped with plate-fins. While inlet and outlet fluid distributors and channels were taken into account in the computational domain, the porous media technique was applied to the channels as an alternative to the fins in the original cold box. The mass transfer model including the phase change was accounted for by the flash calculations. Local thermal non-equilibrium (LTNE) between the porous medium and fluid flow with a mass transfer was used in the simulations. Three principal side distributors, i.e. diagonals A, B, and C, were used, and their performance was evaluated by CFD. It was found that using each of these types of distributors led to different CFD results in the cold box. The heat transfer rate in the case of the diagonal C was 73% more than that of the diagonal A. The flow uniformity index in the case of the diagonal C was 11.6% greater than that of the diagonal A in the stream C.

Heat flux and heat transfer coefficient may either be measured by a single measurement process, or they may require the measurement of several quantities before they may be estimated. Of course, it is best if the required quantity is directly measurable. We will give as much detail as possible, keeping in mind the target reader of the book. Many techniques are beyond the scope of the book and require direct reference to the appropriate research literature.

The particle deposition characteristics of plate-fin heat exchangers were studied using a particle deposition model with a random function method. The effects of the inlet velocity, particle size, and temperature difference on particle deposition and the distribution of the particles deposited in plate-fin heat exchangers were investigated. The simulation results showed that the thermal diffusion–induced motion of small particles was obvious at low velocities, the deposition of large particles was mainly limited by the critical velocity, there was a maximum deposition velocity in particle deposition and the maximum deposition velocity decreases with increasing particle size. Finally, large particles would rebound and deposit after secondary impacts. The temperature difference will increase the average deposition efficiency of 1 μm particles, and reduce the average deposition efficiency of 7 μm particles. The plate-fin heat exchanger should be designed with consideration for the particle size range and velocity seen in the intended application.

Fabricating perforations in fins causes improvement in heat dissipation rate with lower pressure drag up to a specific perforation number and size of perforation. Again knurled surfaces augment hea...

Fin and tube heat exchangers are widely used in air conditioning. In this study the effect of tube shape on air-side heat and mass performance was experimentally and numerically investigated under typical operating condition, varying both dry bulb temperature and air flow velocity. The experimental results showed that the dry-bulb temperature has little impact on sensible heat transfer rate, whereas the mass transfer rate increased with the increase of dry-bulb temperature. Compared with circular tube, the heat transfer coefficient of elliptic tube is about 66% higher and the dehumidifying coefficient is around 21% higher. However, the difference of the dehumidifying coefficient between two tube shapes shrinks towards equality when the dry bulb temperature reaches to 28 °C. To further discuss the heat transfer mechanism of circular and elliptic tube heat exchangers, three-dimensional numerical simulations were conducted based on the experiments. The results showed that the heat and mass transfer performance was closely related to the tube shape. When wet air flowed around elliptic tube, the streamline shape served to make the flow and temperature field uniform. The flow boundary layer as well as temperature boundary layer was thinned, especially on the upstream and downstream of tubes, so the influence of wake was reduced and the water vapor was efficiently removed. This results in improvement of the heat and mass transfer performance in the wake region of each tube. For the same heat duty, the plate fin heat exchanger with elliptic tube is more compact than that with circular tube.

The mal-distribution of gas–liquid mixtures has serious influences on the heat-transfer performance of plate–fin heat exchangers (PFHEs), which would result in an adverse effect on the stable and efficient operation of a natural gas liquefaction plant. Therefore, it is necessary to investigate the phase distribution performance of PFHEs and its influence on the natural gas liquefaction performance. In this study, a two-phase flow distribution experimental system was built to investigate the flow distribution characteristics of a PFHE under different working conditions. The effects of gas–liquid ratio, tilt angle, and sloshing on the gas–liquid distribution were studied. In addition, the influences of mal-distribution of the feed gas, nitrogen refrigerant, and mixed refrigerant (MR) on the heat transfer and natural gas liquefaction performance were analyzed through the Aspen Muse software. The results showed that the greater the gas–liquid ratio and tilt angle, the more uneven the liquid flow distribution. The efficiency of the MR process in the tilt condition was reduced by 5.2% to 18.5% compared to that in the horizontal condition. Compared with the tilt working condition, the sloshing could reduce the unevenness of the flow distribution. To satisfy the natural gas liquefaction rate of more than 90%, the critical standard deviation values of flow distribution unevenness of the feed gas, nitrogen refrigerant, MR, and MR under the tilt condition were 8.33, 2.95, 4.42 (liquid phase), and 1.42 (liquid phase), respectively. In the process design, to ensure the output and liquefaction rate, the amount of the refrigerant circulation and power consumption should be kept at the margin of approximately 6% and 4% for the nitrogen expander and MR liquefaction processes, respectively.

The compact heat exchanger is significant for hybrid and electric/fuel cell vehicles with high energy utilization efficiency. This contribution introduces the heat current method to propose a new solution for the design and optimization of heat exchanger structure by combining the empirical correlations of heat transfer and flow resistance. On the premise of decreasing the air flow length of a plate-fin heat exchanger, the tree traversal method is utilized to optimize the offset strip fins on both the hot and the cold fluid sides of a plate-fin cross-flow heat exchanger. Moreover, an experimental setup is built for testing the thermal-hydraulic performances of the original and improved heat exchangers. The results show that the difference between the experimental and the theoretical results is less than 3.23% which represents the heat current method is feasible for heat exchanger analysis and optimization. Meanwhile, the total heat transfer coefficient increases by 7.43% and the pressure loss on the air side reduces by 29.7% for the improved heat exchanger, which is more suitable and high-efficient for the limited space in a high-power vehicle. Finally, the corresponding functions of the total heat transfer coefficient and pressure loss with different air mass flow rates are constructed for future practical applications of the improved heat exchanger.

A novel caudal-fin-inspired hourglass-shaped self-agitator installed inside a plate-fin heat exchanger has been experimentally investigated to characterize its thermo-hydraulic performance. Because of fluid-structure interaction between the air and the caudal-fin-inspired hourglass-shaped self-agitator, there is periodic conversion between fluid kinetic energy and elastic strain energy. Vortices generated by the self-sustained vibration of the self-agitator enhance flow mixing and thus heat transfer performance. Experiments were conducted at a wide range of Reynolds numbers from 400 to 10,000, which covered the laminar-transitional-turbulent regime. Experimental correlations of pressure drop as a function of a dimension parameter, friction factor, and Nusselt number have been proposed. Mutual coupling motions and effects of multiple-row flapping caudal-fin-inspired hourglass-shaped self-agitators in parallel and tandem configurations were studied by using a high-speed camera. A stereo Particle Image Velocimetry system was used to conduct detailed flow field measurements to quantify the flow mixing level. Parameter studies for the stream-wise distance (i.e., the pitch) between the neighboring caudal-fin-inspired hourglass-shaped self-agitators have been investigated to exploit the best performance of the heat exchanger equipped with caudal-fin-inspired hourglass-shaped self-agitators. For the chosen plate-fin heat exchanger and assigned working conditions, the best heat transfer performance was obtained with twelve-row self-agitators with a pitch of 12.5 mm, which caused a 200% increase in the Nusselt number over the clean channel at the same Reynolds number. However, the best overall performance was obtained with six-row self-agitators with a pitch of 25 mm, which caused a 68% enhancement in thermal-hydraulic characteristics compared to the clean channel at the same Reynolds number.

A fin heat exchanger is a simple form of cooling device that is built for efficient heat transfer from one medium to another. Generally, it involves medium such as fluid to perform heat exchange via convective heat transfer. This study is aimed at investigating the effects of diverse designs (arrangements of the fins), qualities (the total surface area of the fin for heat exchange) and conditions (the surface characteristics) of fin heat exchanger on the degree of heat transfer from the experimental perspective. The fin heat exchanger was fabricated and tested. It was observed that by varying the arrangement and condition of the fins, the rate of heat transfer could be affected. However, varying the quality of the fin didn’t have much impact. Nevertheless, the quality aspect of the fin heat exchanger could play a significant role for heat exchanger of larger in scale and dimension. The coating, that is the condition of the fins, aided in decreasing the temperature at a much higher margin at all fan speeds.

Ceramic materials enable operation in high temperature and harsh environments and can so exceed the capabilities of comparable metal heat exchangers. For the use in power plant applications and high temperature processes a heat exchanger has to operate under both high temperature and high pressure levels. So far, the operation of a ceramic heat exchanger under such conditions has not been investigated. This work presents a ceramic heat exchanger prototype with modified offset-strip-fin design, which was experimentally investigated in a specifically designed test environment. Experimental tests were conducted with air as a heat transfer fluid at temperatures up to 800 °C, absolute pressures up to 5 bar and norm volume flows up to 160 N m3 h−1. The functionality under high temperatures and absolute pressures could be proven. The paper reports measured performances of the heat exchanger prototype, for which heat transferred up to six kilowatt and effectiveness up to 97% has been achieved. A comparison of Colburn and friction factors with correlations from literature was conducted, too. Good agreement for Colburn prediction of the flue gas channels could be shown, but the investigation also reveals a limited applicability for the friction factor and the Colburn factor of the process gas channel.

Double-pipe heat exchangers are devices that provide the transfer of thermal energy between two fluids at different temperatures. The major use of these heat exchangers is the sensible heating or cooling process of fluids where small heat transfer areas are required. The oil cooler is an example of these processes. In this study, fouled finned, clean finned, fouled unfinned, and clean unfinned double-pipe heat exchangers used as an oil cooler in ships have been compared. In thermal design, suggested different Nusselt number equations have been used, and the results of these equations have been shown in tables and figures. As a result, it is evaluated that using fouled finned double-pipe heat exchanger as oil cooler in ships is the most appropriate selection. 1. Introduction A double-pipe heat transfer exchanger consists of one or more pipes placed concentrically inside another pipe of a larger diameter with appropriate fittings to direct the flow from one section to the next. One fluid flows through the inner pipe (tube side), and the other flows through the annular space (annulus). The inner pipe is connected by U-shaped return bends enclosed in a return-bend housing. A typical double-pipe heat transfer exchanger is shown in Fig. 1. Double-pipe heat exchangers can be arranged in various series and parallel arrangements to meet pressure drop. The major use of the double-pipe heat exchanger is the sensible heating or cooling process of fluids where small heat transfer areas (up to 50 m2) are required. This configuration is also very suitable for one or both of the fluids at high pressure because of the smaller diameter of the pipes. The major disadvantage is that they are bulky and expensive per unit of heat transfer surface area. These double-pipe heat exchangers are also called hairpin heat exchangers, and they can be used when one stream is a gas, viscous liquid, or small in volume. These heat exchangers can be used under severe fouling conditions because of the ease of cleaning and maintenance. The outer surface of the inner tube can be finned, and then, the tube can be placed concentrically inside a large pipe, as shown in Fig. 2. In another type, there are multi tubes, finned or bare, inside a larger pipe. The fins increase the heat transfer surface per unit length and reduce the size and, therefore, the number of hairpins required for a given heat duty. Integrally, resistance-welded longitudinal fins have proven to be the most efficient for double-pipe heat exchangers. Fins are most efficient when the film coefficient is low.

The current work reports an experimental study on hydrothermal improvement in a chevron plate-fin heat exchanger combined with holes and winglets. The experiments are performed for water fl...

Bypass flow deserves a deep research as it is the important phenomenon in plate-fin heat exchanger and is of great influence on the thermal performance. Present studies had consulted this problem, but did not conduct a throughout study and restricted in a limited geometry. Therefore, in this paper an experimental bench is built for the research. Numerical simulations are also carried out on the models with and without bypass flow. The discrepancy of average heat transfer coefficient in simulation with bypass flow increases with air velocity and the maximum difference reaches 82.76% at the velocity of 10 m/s when compared to the model without that, but reduces to be 19.1% when compared to experimental results. After experimental validation, top bypass flow is analyzed with different ratios of top duct height to fin height and varied air velocities. A relationship between air velocity and its minimum height ratio is gained for the estimation in initial design of plate-fin heat exchanger. The optimization with varied fin numbers and interval distances is also carried out, and it is found that the optimized ratio of frontal fin area to frontal plate-fin heat exchanger area is almost keeping at an approximate value of 0.5 for all cases, but thinner fin and narrower air flowing channel can make better heat transfer effect. This paper reveals the influence of top bypass flow on thermal performance and design principle of plate-fin heat exchanger, which is hopeful to be an instruction for its future application in many fields.

In recent years, lot of work in the field of cryogenics is going on because its applications are now more prominent with the advancement of technology. Many researches have been done on fin geometry of the plate fin heat exchangers but only few works have been published on cryogenic nanofluid performance. This research work is focused on the enhancement of liquid He cryocooling heat exchange performance in rectangular plate fin heat exchanger. Four types of nanoparticles namely Al2O3, CuO, Fe3O4 and Single Wall Carbon Nanotube (SWCNT) are mixed with base fluid liquid helium to compare their performance as a plate fin heat exchanger fluid. A CFD analysis is done for fluid flow in the turbulent region. Comparison of the nanofluids at cryogenic temperature is compared with heat transfer performance parameter Colburn j-factor and pressure drop performance parameter Fanning’s friction factor(f). It has been found that around 15-30% enhancement of thermal performance is achieved with nanoparticles in comparison with liquid He without any nanoparticles. It has also been observed that there is an improvement of \(\frac{j}{{f^{1/3} }}\) factor representing heat transfer enhancement without much increasing pumping pressure.

In this paper, a concept of balance is used to improve the important parameters of the thermal systems. In fact, using this concept give the designer to propose some new configuration which is more efficient. To show the benefit of this concept, firstly, the proposed balancing method is introduced for a simple case study after that its application is used in optimization of thermal systems. In this regard, to achieve the better optimal results in each problem, the unbalanced factors are detected and some solutions are presented to reduce the system unbalancing. Three case studies including Rankine cycle, plate fin heat exchanger, and double pipe heat exchanger are discussed and optimized to show the benefits of this method.

Compact parallel-flow three-fluid heat exchanger (TFHX) of plate-fin type is optimized for attaining the minimum entropy generation unit. Four different types of plate-fins (plain rectangular, offset strip, corrugated louvered, and wavy fin (WF)) which are embodied within heat exchanger have been selected for the study under both cocurrent and countercurrent flow arrangements. The range of the decision variables are 0.3≤ma, mb, mc≤3, 0.1≤Ø≤0.95, 0.1≤Lx, Ly≤2, 0.015≤H≤0.033, 100≤n≤700, 0.0001≤tf≤0.0002, 0.001≤l≤0.009, 0.01≤Lwav≤0.09, and 0.001≤A≤0.005. Genetic algorithm is selected as an optimization tool that is apt in handling various continuous and discrete variables and the problems with the complexities in the objective function as well as in constraints. Validation of the optimization model is carried out by comparing the optimum results with that obtained from the experiments, particle swarm optimization (PSO) (under without heat duty constraint), and graphical method (under with heat duty constraint). It is observed that for a specified heat duty (180 kW) and given operating conditions, corrugated louvered fin (CLF) with countercurrent flow arrangement offers the minimum entropy generation among all. It is riveting to learn that the optimum results occur for most of the considered cases when the flowrate of the central hot fluid is lower than that of the adjacent fluids. At fixed Re = 3000 for all the fin types, off-set strip fin is the most favorable one, and plain rectangular fin (PRF) offers the worst solution comparatively.

High-efficiency heat exchangers are essential to liquefy hydrogen, which is spotlighted as a next-generation energy source. Among the heat exchangers, plate-fin heat exchanger has a very large effective heat transfer area per unit volume, which allows the simultaneous exchange of several fluids, so it is specialized in the hydrogen liquefaction process. However, very few studies have been conducted for heat transfer analysis of plate-fin heat exchangers. Therefore, in this paper, the single-phase convective heat transfer coefficients were calculated using the modified Wilson plot method, and pressure drop was compared with other correlations. The main results are summarized as follows. The pressure drop agrees well with the previous correlation, but the convective heat transfer coefficients has different from others. Therefore, based on the experimental results, a new single-phase heat transfer correlation for the plate fin heat exchanger is presented.

Plate-fin heat exchanger (PFHE) is a popular and featured compact heat exchanger, which transfers heat at relatively low-temperature differences and has a high heat transfer surface area to volume ratio. Due to the compact size and light weight, it has been widely used in various engineering areas such as energy, transportation and aerospace. The optimal design of PFHE aims to minimize the economic cost or maximize the efficiency, formulating a mixed integer nonlinear optimization problem which challenges the optimization tools. In this paper, the number of entropy generation units is formulated as the objective functions. Given the strong non-linear behaviors, a recent proposed meta-heuristic algorithm named sine cosine algorithm (SCA) is adopted to solve the problem of the design and optimization of the PFHE and compared with the results of several classical and new algorithms. Test results show that the sine cosine algorithm is the a competitive solver for PFHE optimal design problems.

Parametric models of ARX structure express the relationship between an input u ( t ) and one output y a r x ( t ) . The purpose of the study is first to identify such a transient model through temperature measurements in a calibration experiment. It relates the output, that is the temperature response at the outlet of each of the two fluids that flow inside the heat exchanger, to the temperature increase at the inlet of the hot fluid, considered as a transient thermal input. This model is validated in a different experiment and transient perturbation experiments are run with maldistribution or flowrate changes. They are processed in order to detect such structural changes with respect to the calibrated model and to get the steady state characteristics, transmittances and effectivenesses, of the exchanger. The advantages and drawbacks of this non-destructive technique, which does not rely on any heat transfer correlation, are detailed and discussed.

A large size multistream plate fin heat exchanger (MSPFHE) is developed for an in-house-developed modified Claude cycle-based helium liquefier. The development of this heat exchanger, including the...

An experimental investigation is performed using liquid R113 to study the thermohydraulic characteristics of plate-fin heat exchanger with plain, serrated and perforated fins. Meanwhile, three performance evaluation criteria j/f, j/f1/2 and j/f1/3 are used to qualitative compare their comprehensive performance. Further, to study the effects of heating condition and Prandtl number on heat transfer, a numerical model of serrated fins is carried out. The fin channels with a uniform heat flux at bottom end or at both bottom and upper ends are studied as two types of heating conditions, namely, single-fold and two-fold modes. Besides, using air (Pr = 0.744), R113 (Pr = 9.02) and ethylene glycol (Pr = 51.65) aqueous solution as working media, the Prandtl number effect is discussed. The results reveal that the comprehensive performance of serrated fins is the best. Colburn factor j of single-fold mode is lower than that of two-fold mode. The Colburn factor j decreases as the Prandtl number increases in laminar flow and it is independent of Prandtl number in turbulent flow. A modified Colburn factor j based on the Manglik & Bergles correlation is proposed as functions of (Pr/Prair)−0.04827 in laminar flow. The conclusions provide the guidance on the design of plate fin heat exchanger.

Creep-fatigue life prediction is essential to plate-fin heat exchangers (PFHE) work at high temperatures and pressures in addition to thermal cycles. As the core of PFHE, the plate-fin structure is a complex pore structure and it is pretty difficult to carry out the stress analysis by conventional finite element method. Thus in this paper, a homogeneous method is proposed to do the strength design for plate-fin structure. This method treats the pore structure as an equivalent solid structure, and the key is to calculate the equivalent material properties and the equivalent stress. The equivalent mechanical properties have been obtained in our previous work [1], and in this paper the equivalent thermophysical properties including thermal conductivity, coefficient of thermal expansion, specific heat and density have been derived. This equivalent method is also verified by the three-dimensional finite element method. Besides, creep and fatigue tests of plate-fin structure are applied to calculate the stress and strain magnification factors. Basing on the equivalent material properties, a full scale stress analysis of PFHE by the equivalent finite element model has been carried out successfully to calculate the equivalent stress. After that, we multiply the equivalent stress-strain by the stress and strain magnification factors to calculate the local stress and strain. Then the creep and fatigue damages are predicted according to design curves of base metal. The result of equivalent model agrees well with that of the classical model, which concludes that this homogeneous method is effective to predict the macroscopic performance of plate-fin structure.

In heating, ventilation and air-conditioning (HVAC) systems, air-to-air plate-fin heat exchangers (PFHEs) can be used as heat recovery devices to reduce the building energy consumption. However, existing heat exchanger models have limitations in simulating the performance of air-to-air PFHEs. For example, some models adopt heat transfer correlations which are not suitable for PFHEs, while others require detailed geometric data which are usually difficult to access, etc. To address these limitations, we developed a new model for air-to-air PFHE without dehumidification. Based on empirical correlations dedicated to air-to-air PFHEs, the mathematical models of the heat transfer and the flow resistance were built. The new model considers the impacts of the changing air flow rates and temperatures. Additionally, it only requires readily available nominal parameters as inputs and does not need any geometric data. Furthermore, no numerical discretization is needed to solve the equations, which makes the model computationally more efficient than models using the finite-element method. To evaluate the performance of the new model, it is implemented using an object-oriented, equation-based modeling language Modelica. Case studies show that the new model can predict the results with a relative deviation less than 10% compared to the experimental data.

A one-dimensional model of catalyst-coated fin in plate-fin heat exchanger reactors was developed in this study to consider the effects of heat of reaction on the fin efficiency. The results of the model showed that the occurrence of a surface reaction must be treated carefully since it drastically changes fin behaviour compared to conventional thermal fins. The impact of dimensionless numbers representing the coupling between fin geometry, surface reaction and heat and mass transfer was investigated, and limit conditions where a reactive fin behaves as a conventional thermal fin was circumscribed according to these parameters. The results of the developed reactive fin model were also compared to computational fluid dynamics simulations and showed very good representativeness for all heat transfer, reaction and by-pass effects. The comparison demonstrated that this simplified model is strong enough to represent reactive fins on the surface of which a catalytic surface reaction occurs, for both laminar and turbulent flows in square millichannels.

The two-phase (liquid and gas) flow distribution in the header of a plate-fin heat exchanger was experimentally investigated. Small mass fractions of the liquid phase in the liquefaction process of natural gas were considered in this study. The liquid and gas flow velocity were measured using optical methods such as PIV/PTV/LIF. The flow maldistribution of liquid and gas flows was quantified and addressing this problem by attaching a porous baffle or modifying the inlet nozzle configuration was studied. The results showed that a vane swirler with a diffuser enhanced the flow distribution of both the liquid and gas phases fluid.

This paper presents a derivation of design guidelines for plate heat exchangers used for evaporation of zeotropic mixtures in heat pumps. A mapping of combined heat exchanger and cycle calculations for different combinations of geometrical parameters and working fluids allowed estimating the trade-off between heat transfer area and pressure drops on the thermodynamic and economic performance indicators of the cycle. Compressor running costs constituted the largest cost share, and increased due to a steep decrease of the heat pump coefficient of performance at high refrigerant pressure drops. It was found that the pressure drop limit leading to infeasible designs was dependent on the working fluid, thereby making it impossible to define a guideline based on maximum allowable pressure drops. It was found that economically feasible designs could be obtained by correlating the vapour Reynolds number and the Bond number at the evaporator inlet as Re V − 0.42 Bd 0.26 ≈ 0.040 . The use of the proposed guideline was illustrated for the mixture Propane/Iso-Pentane (0.5/0.5), leading to evaporator designs with net present values deviating maximum −4.4% from the best value found in the mapping. The presented methodology can be applied in different scenarios to develop similar guidelines, thereby decreasing the cost of combined cycle and component optimizations.

The flow distribution and head loss in the distributor of a plate-fin heat exchanger were experimentally investigated using quantitative and qualitative flow visualization methods. The flow distribution and head loss are important parameters related to the thermal performance and economic design of the heat exchangers. The effect of the different distributor angles (30°, 45°, and 60°) and the alignment configuration at the junction in the distributor were studied. The Reynolds number based on the hydraulic diameter was varied from 100 to 1200. Flow visualization using the dye injection and hydrogen bubble methods was applied to capture the qualitative flow structure inside and around the distributor. Digital particle image velocimetry was used to measure the instantaneous velocity fields, and the flow maldistribution was quantified by using the averaged velocity information. The qualitative flow visualization showed the variation of streamwise velocity in the end of the distributor and the existence of the secondary flow at the junction. From the velocity and pressure measurement, we found that the 30° model has the worst flow distribution and the smallest head loss among other models and the 60° model with misaligned configuration has the best flow distribution and the largest head loss.

As a novel hybrid optimization approach, the single and multi-objective BAHPSO are investigated for thermal designing of the cross-flow plate fin heat exchanger (PFHE) under given heat duty and pressure drop constraints. Because both of the Particle Swarm Optimization (PSO) and Bess Algorithm (BA) are operating with a random primary population of solutions, the current study combined their searching abilities for the first time, and presented a novel searching procedure named BAHPSO. In the current investigation, Multi-Objective optimization (MO) of BAHPSO is simultaneously employed to acquire the maximum effectiveness and the minimum total annual cost (TAC) of a heat exchanger as two contradict objectives and then results are compared with MOPSO and MOBA. Hot and cold side length, fin frequency, number of fin layers, fin thickness, fin height, and fin lance length are chosen as seven decision parameters. Also, a sensitivity analysis is performed to study the impact of geometrical parameters on each objective function. Finally, accuracy and efficiency of the presented algorithm is proven via illustrative single-objective optimization case studies which adopted from the references. Results demonstrate that the BAHPSO can detect optimal shape with higher accuracy compared to other algorithms.

The forced convective turbulent flow of Al2O3-water nanofluid through the offset-strip channel is studied numerically. The mixture model is applied to model the Al2O3-water nanofluid flow. The studied parameters are the channel height (5, 10, and 15 mm), channel length (50, 100, and 150 mm), strip length (5, 10, and 15 mm), strip pitch (5, 10, and 15 mm), strip thickness (0.5, 1.0, and 1.5 mm), Reynolds number (6000–22,000), and nanoparticles concentration (0–4%). It is found that the channel height has the greatest effect on thermal-hydraulic performance of the offset-strip channel, and the strip thickness comes in the second. Also, the nanofluid shows a better performance in comparison with the base fluid. Finally, generalized regression equations are developed for the Al2O3-water nanofluid flow across the offset-strip channel, as function of Reynolds number, nanoparticles concentration, and geometrical parameters.

The maldistribuiton of gas-liquid mixtures has serious influences on the heat-transfer characteristics of plate-fin heat exchangers (PFHEs) and restricts the development of PFHEs in the floating liquefied natural gas (FLNG) field. To efficiently use PFHEs for FLNG, it is necessary to investigate the gas-liquid distribution at the entrance of PFHEs under sloshing conditions. In this study, an experimental gas-liquid distribution system was built, and the distribution characteristics of a PFHE distributor were investigated under sloshing conditions using air and water as mediums. The influence of sloshing form, sloshing amplitude, and sloshing period on the gas-liquid distribution is discussed with flow ratio m∗k and standard deviation STDk as the distribution index. The results showed that in the experimental condition the non-uniformity of two-phase mixture under sloshing conditions increase by 1.25–18.03% on the basis of steady condition with the increase of sloshing amplitudes and decrease with the increasing sloshing periods. The variation range of two-phase uniformity under mixed sloshing conditions is 14.8–27.9% on the basis of steady condition. These results provide constructive instructions for the design and safe operation of PFHEs in the FLNG field.