Channel Of Plate Heat Exchanger Research Articles

Reduced order model for flow distribution in tapered headers of U-type heat exchangers

Flow maldistribution in the channels of plate heat exchangers (PHEs) results in uneven temperature distribution leading to thermal distortion of the plates, increased pressure drop, and reduced thermal efficiency. Ensuring a uniform flow distribution is paramount for the efficiency and reliability of these systems. Using a modified header shape has the potential to improve flow conditions. To date, there is no mathematical model to predict flow distribution for tapered headers in PHEs. In this context, a reduced-order model has been developed to rapidly assess the potential impact of tapered headers on flow distribution. This model marks a pioneering effort in developing a comprehensive model for estimating flow distribution and pressure drop applicable to both uniform and tapered headers of U-type PHEs, providing valuable insights without necessitating significant computational resources. Key structural parameters, such as header diameter, number of channels, channel area, and taper ratio, that influence flow distribution have been identified by solving the differential equations numerically. For tapered headers, a more uniform flow distribution occurs with fewer plates for the same flow resistance, i.e., the average total head loss coefficient (ζ). Beyond a critical header diameter, the flow remains nearly uniform, regardless of the ζ value. For higher ζ values, there is a channel area range where flow uniformity either increases or remains nearly uniform. One of the most significant findings is the identification of the conditions where tapered headers provide more flow uniformity compared to straight headers. Validated by existing literature, this model shows promising practical applications in the rapid design and optimization of plate heat exchangers.

Estimating parameters of plate heat exchanger for condensation of steam from mixture with air as a component of heat exchanger network

The condensation of vapours in the presence of non-condensable gas is happening in a number of industries. Its efficient realisation must be considered in optimisation of Heat Exchanger Networks (HENs) to increase efficiency of energy usage. In these processes, Plate Heat Exchanger (PHE) with enhanced heat and mass transfer can be effectively used. The method of preliminary selection of the PHE heat transfer area, plate size and corrugation geometry is proposed for the case of steam condensing from its mixture with air. The method uses the developed earlier one-dimensional mathematical model, modernized for PHE consisting from commercially produced plates. The heat transfer area of PHE is minimised by proper selection of plate sizes and geometrical characteristics of its corrugation. The optimisation variables are the corrugation angle to the main flow direction inside PHE channel, the corrugations depth and the length of plate. The case study illustrates the application of the method in case of utilisation low grade heat from exhaust gases after process of drying by superheated steam. The method is implemented as a computer program which can be included as a Dynamic Link Library module in software for HEN optimisation.

Thermal Condition in the Channels of Plate Heat Exchangers

Equipping heat points with plate-type heat exchangers is an integral structural element of the 3rd generation heat and power network and a component of the reliability of the heat supply system as a whole. It has been established that the optimization calculations of heat exchangers of this type are difficult due to the absence of dependences on heat transfer and hydraulic resistance between the channels in the structural space of the heat exchanger.Purpose of research. To clarify the method of calculating plate heat exchangers, excluding the equality of thermal and hydraulic conditions from the generally accepted assumptions.Methods. The research methodology is based on the use of the law of conservation of mass in order to determine the temperature parameters of working fluids in each channel. The solution of this problem is proposed in the form of a system of equations, each of the equations of which characterizes the thermal balance of the channel under consideration. A computer model of the heat exchanger is constructed in order to conduct a numerical study of the thermal regime of the heat exchanger.Results. It is indicated that as an assumption in the well-known mathematical model for calculating the thermal regime of a plate-type heat exchanger, the condition of equal distribution of fluid flows between channels is accepted. This restriction leads to equalization of liquid temperatures in each channel. Taking into account the geometric arrangement of the channels, the excess of the final temperature of the heating and heated coolant in the first and last channels with respect to known data is up to 10%. The results of the study confirm the hypothesis of uneven heating of the coolant along the length of the plate package due to the uneven flow distribution between the channels.Conclusion. The results of analytical calculation and modeling in the SolidWorks environment of the temperature regime in the channels of a plate-type heat exchanger indicate a significant influence of the geometric arrangement on the thermal regime in the channels. The formulated provisions of the mathematical description of the unevenness of the thermal regime of heat exchange channels, taking into account the location of the plates, are recommended to be used when improving the design parameters of plate-type heat exchangers.

PHE (Plate Heat Exchanger) for Condensing Duties: Recent Advances and Future Prospects

Increasing energy usage efficiency requires enhanced heat energy recuperation between process streams in the industry and civic sector with waste heat utilization. The condensation of different vapours is the process encountered in many industrial applications. Increasing the heat recuperation in this process is possible with efficient heat transfer equipment, among which a Plate Heat Exchanger (PHE) is at the leading position. A number of research works have been conducted in recent years concerning construction development and heat transfer enhancement in conditions of limited pressure drop to increase PHE performance in condensation processes. The results of studies on heat transfer and pressure drop in the two-phase condensing flow inside channels of PHE with different geometries of corrugations are discussed. In many implementations, the total pressure drop allowable for gaseous streams in heat exchangers is relatively small. The structure of two-phase flow in PHE channels of complex geometry is very different than in tubes and flat wall channels. The relative differences in approaches to enhance PHE performance in condensation processes based on its modelling, optimisation and design are analyzed. The directions and prospects for future developments are formulated, and potential savings for the economy and the environmental footprint is presented.

Digital image analysis of gas-liquid flow in a cross-corrugated plate heat exchanger channel: A feature-based approach on various two-phase flow patterns

High-resolution photographs of the air-water flow in a transparent cross-corrugated channel are analyzed using digital image processing. Gas-liquid distribution is controlled via several inlet nozzles. Flow direction is varied between upward, downward, and horizontal flow.The image analysis algorithm is applied to a wide range of void fractions and flow patterns including bubbly, intermediate and film flow. Large bubble clusters are separated using edge detection. Local film and bubbly flow are identified with texture analysis. The method is suitable for locally inhomogeneous two-phase flow which is difficult to analyze visually.Objective and reproducible results are obtained by measuring features in the processed images: Mean and maximum bubble diameter, and the ratio of local film flow are determined. For non-uniform gas injection, expansion of two-phase flow across channel width is measured. Impact of flow direction and maldistribution on two-phase flow is demonstrated by calculating differences of the features. Uncertainties of image processing results are quantified. Bias is discussed based on visual analysis of the photographs in a previous study.Models for maximum bubble diameter and local film flow ratio, used to model flow pattern transitions in a previous study, are verified: For uniform two-phase distribution, models generally agree with measured values.

The effect of trapezoidal baffles on heat and flow characteristics of a cross-corrugated triangular duct

The cross-corrugated triangular duct is a common flow channel in plate heat exchangers. To further improve the heat transfer in the cross-corrugated triangular duct, trapezoidal baffles were inserted in the flow channel in this study. The apex angle and baffle position on heat and flow characteristics of the flow channel are investigated. The flow fields, velocity contours, and temperature contours were obtained through calculation. Numerical results of friction factor (f), Nusselt number (Nu), and Performance Evaluation Criterion (PEC) for various channel structures were analyzed. The variations of apex angle and baffle position make the field more complex in the flow channel than that of without baffles. For various apex angles, the f of flow channels with an apex angle of 60° or 90° are close in value, higher than that of 120°. The same trend is found for Nu. When the baffles are in the center of the upper half of the channel, the flow duct owns the highest f, Nu, and PEC values. When the Reynolds number is less than 1000, the PEC value for the flow channel with a particular baffle position at the apex angle of 120° may be lower than that of without baffles.

The influence of plate corrugation geometry on heat and mass transfer performance of plate heat exchangers for condensation of steam in the presence of air

Processes of steam condensation in the presence of air, as non-condensable gas, was studied in experiments with the models of plate heat exchanger (PHE) channels formed by plates with corrugations of different geometry. Validity of the developed mathematical model for the calculation of local process parameters is confirmed, and it is used to facilitate the analysis of experimental results. Sets of experiments were performed on five samples modelling PHE channel main corrugated field. The corrugations angle to plate vertical axis in three experimental samples was 30°, 45° and 60° at the same corrugations’ height of 5 mm. Another two samples had corrugations height 7.5 mm and 10 mm at the same corrugations angle 60°. Various effects of plate sizes and geometrical parameters of corrugations on the performance of PHE as a condenser for steam–air mixture and local process parameters profiles are discussed. Presented analysis shows that the specified process conditions on temperature and pressure drop in PHE can be satisfied by varying corrugations angle and channel spacing at plates of different lengths. To maintain the same temperature program with a decrease of plates corrugation angle from 60° to 30° require the plates with a length bigger from 2 to 2.6 times, depending on specific process conditions. These plate parameters are recommended for use as variables in solving the problem of PHE plate geometry optimisation with the use of the proposed mathematical model.

Digital Image Analysis of Gas-Liquid Flow In a Cross-Corrugated Plate Heat Exchanger Channel:A Feature-Based Approach to Quantify the Impact Of Two-Phase Distribution and Flow Direction on Flow Patterns

Digital Image Analysis of Gas-Liquid Flow In a Cross-Corrugated Plate Heat Exchanger Channel:A Feature-Based Approach to Quantify the Impact Of Two-Phase Distribution and Flow Direction on Flow Patterns

The Influence of Plate Corrugations Geometry on Performance of PHE as Condenser of Steam from its Mixture with Air

The condensation of steam from its mixture with air in channels of plate heat exchanger (PHE) is studied experimentally and with calculations based on a mathematical model developed earlier and based on correlations for local process parameters. The experiments are done for five experimental samples modelling the corrugated field of PHE channel with corrugation angle to the main flow direction 30 degrees, 45 degrees, 60 degrees and channel spacing 5 mm, 7.5 mm and 10 mm. The mathematical model validity is confirmed by comparison of calculated temperature program for cooling of air-stream mixture with experimental data for all five samples. The influence of plates corrugations geometry on overall PHE performance in air-stream condensation and local process parameters distribution is discussed. The analysis reveals that to satisfy the required temperature program, PHE with smaller corrugations angle should have plates of bigger length, as well as PHE with bigger channel spacing. Both these parameters can be used as independent variables in the optimisation of plates corrugations geometry for specified process conditions using examined mathematical model.

Impact of velocities and geometry on flow components and heat transfer in plate heat exchangers

• Influence of velocity on flow is investigated experimentally and numerically. • The flow is mainly determined by substreams velocity and angle β . • Higher velocities promote furrow component and at fixed Re entail lower f and Nu. • Redefined Re , Nu and f shall reflect substreams flow path and velocity. • Numerical results are best validated in terms of heat flux and pressure drop. This study aims at better understanding of the complex flow phenomena in plate heat exchangers. This is identified in the literature to be crucial for improvement of numerical models and generalized heat transfer and pressure drop correlations with respect to their applicability in heat exchanger optimization. 3D numerical simulations of the flow in corrugated channels of plate heat exchangers with different corrugation angles ( β 28° and 65°) were performed in order to investigate in detail complex flow patterns and their influence on the heat transfer and pressure drop at laminar, transient and turbulent flow conditions. The study is supported by the visualization and thermal–hydraulic tests ( Re = 0.1–6037) carried out on the channels with corresponding chevron angles, using fluids of different viscosity to explore effects of different velocities at fixed Re numbers. Consequent alternation of flow patterns is believed to cause recorded differences in heat transfer and pressure drop data. Results from the simulations are analysed in different sections of the channels in light of the flow substreams, velocity distribution, wall shear stress and wall heat flux distribution. They confirm assumptions from the present visualization tests on the longitudinal and furrow substreams interactions and characteristics, as well as on the thermally and hydrodynamically developing flow conditions within a basic cell. A suitability of comparing simulations and experimental data in terms of Fanning friction factor and Nusselt number is discussed relative to the definitions of characteristic length, hydraulic diameter and mean velocity at different flow patterns. The computed heat transfer and pressure drop is in a relatively good agreement with the performed tests and literature data. The presented numerical-experimental analysis outlines importance of the substreams velocity on their interactions and flow components size, which in turn determines PHE channel heat transfer and pressure drop characteristics. The present findings may serve for improvement of CFD modelling, generalized correlations and definition of Re , Nu and f to allow for comparison of heat transfer and pressure drop data at different geometries and flow conditions.

Pressure drop in two phase flow of condensing air-steam mixture inside PHE channels formed by plates with corrugations of different geometries

The pressure drop in the two-phase condensing flow of air-steam mixture inside channels of plate heat exchanger (PHE) with different geometries of corrugations is studied based on experiments and one-dimensional mathematical modelling. The experiments were made with five samples of the PHE channel. In three of them plates with corrugations inclination angles 30, 45 and 60° at the same height of corrugations 5 mm. The other two plates corrugations height was 7.5 and 10 mm at the same pitch to height ratio and inclination angle of 60°. The correlation of pressure drop data for all experimental samples by average process parameters is not able to give acceptable accuracy. The correlation for local pressure gradients in two-phase condensing flow is identified using a developed one-dimensional mathematical model. The model of separated flows of phases is employed for channel zones close to air-steam mixture entrance. Further on channel length with an increase of liquid phase quantities, its combination with the dispersed annular flow structure model is used. The proposed equations can be included in the mathematical model when designing PHE and optimising the geometrical form of corrugations on its plates for steam condensation processes from an air-steam mixture.

Two-phase pressure drop and void fraction in a cross-corrugated plate heat exchanger channel: Impact of flow direction and gas-liquid distribution

Two-phase pressure drop is studied in a transparent cross-corrugated channel for uniform and non-uniform gas–liquid distribution. Both uniform and non-uniform distribution are created by injecting air and water through different numbers of nozzles directly into the channel. The frictional pressure drop clearly indicates the impact of maldistribution.The single channel is pivot-mounted to allow horizontal, vertical upward and downward flow. Two-phase frictional pressure drop can be directly measured only for horizontal flow, neglecting acceleration pressure drop. In vertical flow, a void fraction model is necessary to deduct gravitational pressure drop from the measured pressure difference.The two-phase friction factors of all flow directions are compared to the correlation of single-phase flow. In this manner, homogeneous flow is distinguished from slip. Homogenous flow is confirmed for homogeneous void fractions up to 0.7 at uniform and up to 0.25 at non-uniform gas injection. The single-phase correlation is valid for homogeneous flow when inserting two-phase variables. The experimental two-phase multiplier is compared to correlations from literature.The pressure measurement data are used to determine the actual void fraction. The results are compared to published void fraction models. The homogeneous model fits best for uniform two-phase distribution. For maldistribution, the correlations of Margat et al. (1997) and of Rouhani and Axelsson (1970) predict the experimental void fractions reasonably well, except for very small flow rates.Analysis of experimental results is facilitated by previously published research on flow pattern visualization and modelling in the same test channel. The cross-corrugated geometry generates a swirling motion inducing centrifugal forces often much larger than buoyancy, which thus loses impact on flow pattern, pressure drop and void fraction. The ratio of buoyancy to centrifugal force is expressed by the corrugation Froude number. Slip independent of buoyancy is identified by introducing the hydrostatic correction factor to evaluate friction factors deviating with flow direction.

Numerical Analysis with Experimental Validation of Single-Phase Fluid Flow in a Dimple Pattern Heat Exchanger Channel

A plate heat exchanger with a dimple pattern heat plate has a large number of dimples. The shape of dimples defines the characteristics of the plate heat exchanger. Although such heat exchangers have become increasingly popular due to their beneficial characteristics, knowledge of the flow characteristics in such kind of channel is poor. A good knowledge of the flow conditions inside of such channel is crucial for the successful and efficient development of new products. In this paper single-phase water flow in dimple pattern plate heat exchanger was investigated with application of computational fluid dynamics and laboratory experiments. Numerical analysis was performed with two turbulence models, Realizable - with enhanced wall treatment function and - SST. The first predicts a slightly smaller pressure drop and the second slightly larger compared to the results of laboratory measurements. Our research found that despite the relatively low velocity of the fluid, turbulent flow occurs in the channel due to its shape. We also found that there are two different flow regimes in the micro plate heat exchanger channel. The first regime is the regime that dominates the heat transfer, and the second is the regime where a recirculation zone appears behind the brazing point, which reduces the surface for heat transfer. The size of the second regime does not change significantly with the velocity of the fluid in the volume considered.

Shell and Tube and Plate Feedwaterheaters Effectiveness Comparison

The article presents the results of optimization computational experiments, which evaluated the effectiveness of the use of plate and shell and tube heat exchangers as feedwater heaters. The condensate is heated by water flowing through E35-3.9-440 steam boiler fire-grate cooling circuit. This boiler operates on sunflower husk. The capacity of bioelectric power stations, for which the computational experiment was done, varies from 2 to 27 MW. The steam pressure of the turbine inlet is 40 bar, the temperature is 440 °C. The heater in question is located on the main condensate line before the deaerator. It was done the comparison of the effectiveness of shell and tube and plate apparatus for this application. The optimal fluid velocities for both types of heat exchangers were also analyzed. The limitations of apparatuses design are considered. The computational experiment was done according to the "total costs" optimality criterion, only the design parameters of the heat exchangers were optimized. The experiment shows that the effectiveness of plate heat exchangers is higher in this case. An interesting dependence has also been recovered that relates the water temperature in the plate heat exchanger channels and its optimal velocity. The higher the water temperature, the higher its optimal velocity, which is associated with a decrease of viscosity when increasing the water temperature. This dependence is quite significant, and this fact makes it possible to consider that it is necessary to do optimization when designing this type of heat exchangers.

CFD Modeling Of Turbulence in Channels Of Plate Heat Exchangers

CFD Modeling Of Turbulence in Channels Of Plate Heat Exchangers

An experimental investigation on the heat transfer and friction coefficients of a small plate heat exchanger with chevron angle

In the present study, a small brazed and commercial plate heat exchanger (PHE) with chevron angle 60° and symmetrical layout, was experimentally investigated. New correlations for calculating heat transfer and friction coefficients of hot flow channels were presented. Few studies have been done on the small PHEs and due to the industrial needs, it is necessary to conduct new researches in this field. For this purpose, an experimental model was designed to calculate the single-phase water flow, heat transfer, and friction coefficients. The previously presented correlations were not successful in predicting the mentioned coefficients for the small PHEs and showed a 34% difference with the results of this study. Chevron grooves on the PHE plate can enhance the heat transfer as well as increasing the pressure drop. Defining $$ \left(\frac{j}{f}\right) $$ factor, it was revealed that with the increase of Reynolds number, heat transfer increased more than friction. In previous studies, with increasing Reynolds, $$ \left(\frac{j}{f}\right) $$ factor is almost constant in large PHEs but the results of the present study showed that this increase may be 5-fold higher in the small PHEs as compared with the larger ones. As there was no temperature and heat transfer coefficient value in the hot flow channels of PHE, the Nusselt number was calculated by the modified Wilson plot method.

Flow visualization of two-phase R-245fa at low mass flux in a plate heat exchanger near the micro-macroscale transition

Two-phase R-245fa flow in a plate heat exchanger (PHE) is experimentally investigated to understand the unique flow regimes found during adiabatic operation at low mass flux. A transparent PHE replica with 3.4 mm hydraulic diameter is 3D-printed for flow visualization using high-speed videography. Observed flow regimes support that the thermofluidic characteristics peculiar to PHE operation are due to the macro-microscale transitional two-phase flow from the coexistence of fluid inertial forces and surface tension effects, corresponding to the operating conditions. Maximum stable bubble diameter is bigger at low mass flux than at high mass flux, and the bubbles can become big enough to be fully confined in the millimeter-scale PHE channel to be deformed or elongated. This represents the main thermo-physical characteristics of two-phase flow in mini- and microchannels, which is different from turbulent mixing flow found at high-mass-flux operation or in channels of conventional macroscale. Flow morphology involving bubble coalescence and breakup dynamics is captured and analyzed in relation to the fluid properties and geometric obstructions provided by the heat exchanger channel. Current observations validate some previously published findings that suggest potential microscale boiling mechanisms in PHEs.

Visualization and modelling of flow pattern transitions in a cross-corrugated plate heat exchanger channel with uniform two-phase distribution

Plate heat exchangers are often used for two-phase applications such as evaporation or absorption. In order to predict heat and mass transfer and pressure drop more accurately, knowledge of flow patterns is essential.Most of the published flow pattern maps for plate heat exchangers are biased by non-uniform inlet conditions. The objective of this study is to eliminate inlet effects, to which end, a uniform and steady two-phase distribution is implemented.An adiabatic air-water mixture is visualized in a transparent cross-corrugated single channel. The flow direction is varied between horizontal, vertical upward and downward. Both phases are injected directly into the channel via multiple nozzles. All superficial velocities are determined for the actual operating conditions.Flow patterns are mostly not affected by flow direction. Instead, the centrifugal force often dominates over buoyancy due to the swirling flow induced by the corrugations. A corrugation Froude number is defined to explain the findings. So-called slug flow is not observed, although being reported by other authors. This is attributed to the inlet design.Simple model assumptions regarding flow pattern transitions in tubes are adapted to the cross-corrugated channel. An additional model is proposed to account for the gradual transition of flow patterns at higher void fractions. The minimum kinetic energy for bubble breakage is also modelled to explain the gas accumulation observed at slow down-flow.

Heat transfer characteristics of concave and convex curved vortex generators in the channel of plate heat exchanger under laminar flow

The geometric shape of vortex generator (VG) is an important contributory factor to heat transfer enhancement. In this paper, concave and convex curved delta winglet VGs in a channel of plate heat exchanger under laminar flow are studied and compared with the normal plane delta winglet VG to optimize the shape of VGs. The effects of the central angles ranging between 10° and 80° and the angles of attack (20°, 30°, 40°) of the concave and convex curved delta winglet VGs on the characteristics of heat transfer and pressure loss are presented for different Reynolds number (Re) ranging from 200 to 1400. The results showed that Nusselt number (Nu) increases with the increase in the central angle of the concave curved delta winglet VG, while Nu decreases with the increase in the central angle of the convex curved delta winglet VG. Comparing with the normal plane VG, the concave curved delta winglet VG is beneficial to heat transfer enhancement, while the convex curved delta winglet VG is disadvantageous to heat transfer enhancement. Optimum values of the central angle and the angle of attack exist for the concave curved delta winglet VG in terms of the best heat transfer performance. The largest values of Nu and surface goodness factor (JF) for the concave curved VG are larger by 19.7% and 11.35% respectively than those for the convex curved delta winglet VG in the studied range of parameters. Correlation equations for both Nu and friction factor (f) as a function of Re, central angle and angle of attack are presented for both concave and convex curved delta winglet VGs.

Mathematical Model of Plate Heat Exchanger for Utilisation of Waste Heat from Condensable Gaseous Streams

The mathematical model of vapour condensation from the mixture with noncondensing gas in Plate Heat Exchanger (PHE) channels is presented. The model accounts for the change of process parameters along the heat transfer surface and local features of heat and mass transfer processes in PHEs channels with plates of different corrugations geometry. It consists of the system of ordinary differential equations with considerably nonlinear right parts. The software for its solution by finite difference method is developed. The validity of the model is confirmed by comparison with the experiment for steam-air mixture condensation in a PHE channel sample.