Chevron-type Plate Heat Exchangers Research Articles

A simplified LMTD approach to assess the effectiveness of a chevron-type plate heat exchanger

A simplified LMTD approach to assess the effectiveness of a chevron-type plate heat exchanger

Performance evaluation of novel plate-type condenser for an absorption/adsorption refrigeration system: Experimental and CFD study

Plate heat exchangers are widely used in many industries, such as refrigeration and air conditioning. Traditionally, the condenser in an absorption system comprises a shell and tube heat exchanger. However, we have innovatively replaced the conventional tubes with chevron plates in this system. The following variables were measured: condensation pressure (5.75–7.00 kPa), wall subcooling (0.2–1.8 °C), and channel Reynolds number (350–1400). In alignment with experimental results, the CFD simulation shows a higher condensation rate and large droplet size at the higher subcooling, and lower heat flux as the saturation pressure is decreased. Moreover, the overall heat transfer coefficient and the pressure drop of the chevron-type plate heat exchanger are increased by 1.60–5.00 times and 1.30–3.00 times, respectively, compared to the shell and tube condenser.

Flow pattern visualization and definition of transition criteria for two-phase flow in Chevron-type corrugated channels

This study aims to highlight the factors influencing flow patterns in Plate Heat Exchangers (PHEs) operated with two-phase flows. Our focus is on providing precise definitions of flow regimes and proposing transition boundaries by comparing diverse experimental datasets. To accomplish this, we designed an experimental apparatus for flow visualization through high-speed videos. The videos clarify flow patterns in an upward-flowing air-water mixture within a chevron-type plate heat exchanger. We introduce a new, clearly defined nomenclature and present the results in the form of a flow regime map. Moreover, we reclassify previously documented flow patterns in the literature using our established nomenclature, creating a unified and comparable database of visualization data. Subsequently, we explore semi-theoretical transition criteria and establish new transition boundaries based on the compiled experimental data. These newly determined transition lines are integrated into a comprehensive global flow regime map, advancing our understanding of two-phase flow behavior in PHEs.

Experimental investigation of two-phase flow in Chevron-type compact plate heat exchangers: A Study on pressure drops and flow regimes visualization

Compact plate heat exchangers are a very promising technology and lately they are being considered for potential use as steam generators in Small Modular Reactors. However, there is a lack of scientific literature on their operation with two-phase flows, especially with non-refrigerant fluids. In this study, we conducted experiments to visualize and measure the pressure drop of a two-phase flow in a Chevron-type Plate Heat Exchanger. An air–water mixture was used in adiabatic conditions as the operating fluid in upward-flow configuration. Visualization was achieved through high-framerate videos. This study covers a wide range of operating conditions, surpassing those documented in existing literature by specifically analyzing also the region of very low mass flux for both phases. The tested conditions ranged from 6 to 365 kg/m2s of water and from 0.02 to 5 kg/m2s of air. Single-phase pressure drops were measured to establish a correlation for the Darcy friction factor. Instead, measurements of the pressure drop in two-phase conditions were processed and presented using a non-dimensional form referred to as the two-phase multiplier. The adoption of a void-fraction model played a crucial role in accurately extrapolating the frictional component of the pressure drop from the measurements, resulting in less scattered data on the Lockhart–Martinelli plot. In addition, the observed flow structures were categorized into distinct regimes (fine-coarse bubbly, Taylor-like bubbly, heterogeneous, partial film, and film flow) based on visual observation and were represented on a flow map. Finally, these data were used to develop new criteria for predicting flow pattern transitions.

Condensation Performance of Symmetrical and Parallel Capsule Plate Heat Exchangers

Condensation characteristics of symmetrical and parallel capsule plate heat exchangers were experimentally investigated in this article. Plate heat exchangers with parallel capsule corrugation, symmetrical capsule corrugation, and chevron-type corrugation are manufactured as the test sections, each containing 41 plates. Pure steam and water are the hot and cold fluids, respectively. The experiments covered a range of equivalent Reynolds number from 9,000 to 25,000, mass flux of condensing fluid from to 18 to 49 kg/(m2·s), liquid Prandtl number from 1.37 to 1.71, average vapor quality from 0.5 to 0.7, and condensation pressure from 110 to 240 kPa. The correlations of condensation heat transfer coefficient and friction factor of the symmetrical and parallel capsule plate heat exchangers are developed. Compared with chevron-type plate heat exchangers, capsule plate heat exchangers show low friction pressure drop, and 33% higher energy efficiency index for condensation flow and heat transfer. Specifically, the energy efficiency index of the symmetrical capsule plate heat exchanger is 8.6% higher than that of the parallel capsule plate heat exchanger, indicating the superiority of counter-rotating longitudinal vortices over co-rotating longitudinal vortices in condensation, similar to what is observed in single-phase flow and heat transfer.

Experimental study of flow and thermal behaviour in single and multi-pass chevron-type plate heat exchangers

The present experimental study brings about the flow maldistribution in the single and multi-pass plate heat exchanger. The different plates packages of 11, 23, 36, and 44 plates are configured in 1–1 pass, whereas 23 and 44 plates are individually configured in 2–2, 3–3, and 4–4 multi-pass arrangements. The experiments have been performed with mixed chevron angle in the Z-type flow configuration of the PHEs for Reynolds number, Re=297–2730, mass flow rate,(m˙)=0.55−1.28kg/s, volumetric flow rate, V˙=2000−4600LPH, inlet temperature for hot and cold fluids, Thi=40∘CandTci=14∘C respectively. The findings indicate that as the number of plates rises, the flow distribution becomes more non-uniform, whereas the increment in the number of pass arrangements brings the flow uniformity inside the channels of the PHEs. It is also found that a multi-pass gives a better thermal performance as compared to a single-pass arrangement. The correlations are established on experimental data for the effectiveness and friction factor using non-linear regression analysis for all configurations of the PHEs.

Study of thermo-hydraulic performance of chevron type plate heat exchanger with wire inserts in the channel

The effect of wire inserts in the channel flow path on the thermal and hydraulic performance of single-pass plate heat exchangers (PHEs) is experimentally investigated. This work is also carried out for Reynolds number, Re = 967–2700; volumetric flow rate for both working fluids, V=˙ 2000–4600 LPH; and inlet temperatures of working fluids (hot and cold) maintained at 45°C and 14°C, respectively. In the present work modified Wilson plot method is proposed for calculating heat transfer coefficient in an unequal flow rate of working fluids. In error estimations of heat transfer coefficient, errors in fit parameters are also considered. The heat transfer enhancement by 10% for 60°/60°chevron angle plates costs a pressure drop of 72.12%, which results in the increment of the tremendous amount of pump works. At the same time, heat transfer enhancement is observed 22 and 15% in 30°/30°and 30°/60°chevron angle plates by increasing pressure drop 29.91 and 33.38% respectively. Based on experimental results, individual correlations are proposed for both the Nusselt number and effectiveness for all geometrical configurations of the PHEs.

Numerical simulation of flow and cooling heat transfer of supercritical pressure refrigerants in chevron-type plate heat exchanger

In industrial fields, heat sources exceeding 130°C are necessitated; hence, the development of industrial high-temperature heat pump systems is anticipated. For the heat release process in such heat pump systems, the use of a plate heat exchanger (PHE), in which high-pressure working refrigerant flows, is examined. In this study, to predict the cooling heat transfer coefficient and pressure drop of supercritical pressure refrigerants flowing in a chevron-type PHE, a computational fluid dynamics model is developed. HFC134a and HFO1234ze(E) are selected as the working refrigerants. Calculations are performed by changing the inlet fluid enthalpy under three reduced pressure conditions from 1.01 to 1.21 and two mass flow rate conditions. The heat transfer coefficient and pressure drop obtained from the simulation reproduced the experimental results well, including the effects of pressure and mass velocity. Therefore, the present model can be applied to existing and new refrigerants if their physical properties are available. Furthermore, it can be used to optimize the plate shape of chevron-type PHEs. Finally, based on the simulation results, the characteristics of the flow behavior and heat transfer of refrigerants in the PHE are discussed.

The Generalized Lévêque Equation and its application to flat tubes without and with passive inserts

Searching for an analogy concept between heat transfer and pressure drop is anything but new, nevertheless it is still the subject of researches as it enables the prediction of heat transfer from pressure drop data, which helps reducing experimental effort for heat transfer measurements. The Generalized Lévêque Equation (GLE) is a widely-used analogy concept, which allows the prediction of heat transfer from pressure drop data, if hydrodynamic boundary layer is developed or still developing. This analogy concept has been successfully applied to flow situations with practical relevance like chevron-type plate heat exchangers, packed beds and in tube bundles, where the boundary layers are forced to reform continuously. In this contribution, the GLE is applied to flat tube flow without and with passive inserts, investigating the impact of passive inserts, which force the boundary layers to reform continuously, on the application of the GLE.This paper presents results of an experimental investigation on pressure drop and heat transfer in flat tubes without and with passive inserts, covering a wide range of Prandtl number (8 < Pr < 60) and Reynolds number values (40 < Re < 3500). These parameter ranges and the passive inserts represent the typical conditions and design used for the liquid side of single-phase flat tube heat exchangers used in the automotive industry. 238 experimental data points for heat transfer coefficients are compared to heat transfer coefficients calculated from pressure drop data with the GLE.The results show that the GLE is not applicable to flat tubes without passive inserts, yet becomes applicable with passive inserts, which are forcing a re-formation of boundary layers in the whole range of investigated Reynolds and Prandtl numbers.

Relationship between inclination angle and friction factor of chevron-type plate heat exchangers

The inclination angle is a key design parameter of chevron-type plate heat exchangers. An increase of the inclination angle can possibly raise the flow friction by two orders of magnitude. According to our review, previous works concerning experimental measurements and correlations of the friction factor in plate heat exchangers are highly inconsistent. In order to establish a benchmark, we use the Large Eddy Simulation to model the fully-developed flow in cross-corrugated channels of the plate heat exchanger, and then calculate the friction factor for various conditions with the inclination angle ranging from 18∘ to 72∘, and the Reynolds number varying from 10 to 6000. Based on the numerical data, well-defined equations are derived to correlate the friction factor with the inclination angle in a general way for both laminar and turbulent flow regimes. Moreover, we derive novel correlations to predict the critical point of laminar-to-turbulent transition in the plate heat exchanger. Then we use these established correlations to draw a friction factor diagram for plate heat exchangers. The diagram maps the relationship between the friction factor and the inclination angle for a wide Re range, which resembles the Moody diagram. Furthermore, the vortex structure and the mean flow properties for different inclination angles are analysed. The results suggest that a larger inclination angle leads to more intensified vortexes and span-wise secondary flows in the channel, resulting in a larger friction factor.

Sınırlı Deneysel Verilerle Yapay Sinir Ağı Kullanılarak Chevron Tipi Isı Değiştirici için Termal Modelleme ve Performans Analizi

The problem of heat exchange between two or more fluids at different temperatures is one of the most important and most common problems of engineering applications. In order to solve this problem efficiently, the transfer of energy between two liquids at different temperatures is carried out by heat exchangers. Heat exchangers increase the energy efficiency as they can transfer the energy contained in the system to another part of the process instead of just pumping and wasting. A plate heat exchanger, a variant of heat exchanger, use a series of thin plates to transfer heat between two liquids. Thermal modelling of the heat exchanger is important due to determination of the outlet temperature of fluids depending on the system parameters. In this paper, an artificial neural network (ANN) model is used to simulate the thermal performance of a chevron type plate heat exchanger using water as working fluid. The ANN algorithms have a widely usage in thermal analysis studies of heat exchangers such as modelling of heat exchangers, estimation of heat exchanger parameters, estimation of phase change characteristics in heat exchangers and control of heat exchangers. The outer temperatures of the water are estimated depending on the cold water mass flow rate, inlet hot water temperature and inlet cold water temperature by using limited experimental data. Then the experimental results and the estimated results are compared for testing the accuracy and reliability of the developed algorithm. The results show that the experimental and estimated results have a good agreement. The developed network structure estimates the outlet temperatures with 2.58 % and 1.80 % for hot and cold water, respectively. In addition, the predicted performance of the network developed by applying untested input parameters was examined. Estimation accuracy was compared with theoretically calculated output temperatures by thermal analysis using the same inputs. According to the obtained results, it is seen that the theoretical results and prediction results are compatible with each other in determining the output for new inputs and the reliability of the developed network is proved in different inputs according to this result. After that, experimentally not obtained variations of the heat transfer rate, overall heat transfer coefficient and energy efficiency are determined depending on the inlet temperatures and mass flow rate of cold water.

Effect of Secondary Vortex Flow Near Contact Point on Thermal Performance in the Plate Heat Exchanger with Different Corrugation Profiles

The present study numerically investigates thermal performance and turbulent flow characteristics of chevron-type plate heat exchangers with sinusoidal, trapezoidal, triangular, and elliptical corrugation profiles. The commercial code of ANSYS Fluent (v. 17.0) is used for computational fluid dynamics (CFD) simulation with the realizable k-ε model. In particular, we focus on the influence of configuration shape on a substantial change in flow direction near the contact point, yielding local vorticity. As a result, secondary vortical motions are observed in the flow passage with vorticity that is distributed locally and which changes near the contact point. Higher flow mixing generated and distributed by the secondary vortical motions contributes to the increase of the Colburn j-factor as well as the friction factor. The highest Colburn j-factor and friction factor are obtained for an elliptical profile, compared to other shapes, because of the increase in the vortex strength near the contact point.

Heat transfer enhancement of plate heat exchangers with symmetrically distributed capsules to generate counter-rotating vortices

Capsule-type plate heat exchanger takes advantages of low flow resistance and high overall performance. To obtain greater energy efficiency, a new type named symmetrical capsule plate heat exchanger (SCPHE) is constructed based on the idea of counter-rotating vortices. For SCPHEs, the adjacent capsules distribute symmetrically at the same-side of the plate, and the capsules keep an angle of 45° with the main flow direction. The heat transfer enhancement and the influences of capsule geometries were studied numerically. Counter-rotating vortices generating in the channels promote the swirl flow and disturb the boundary layer. Both fluid impinging and the vortices dominate the heat transfer enhancement, which become much stronger under smaller capsule, resulting in higher heat transfer coefficient. The correlations of Nu and f considering the effects of the capsule geometries are developed. SCPHEs show higher energy efficiency than capsule-type plate heat exchangers and chevron-type plate heat exchangers in the view of PEC and EEI.

Thermo-hydraulic performance analysis of multi-pass chevron type plate heat exchanger

Thermo-hydraulic performance of PHE in Z-type flow arrangement under the steady state in four different pass arrangements 1–1, 2–2, 3–3 and 4–4 for both isothermal as well as non-isothermal conditions is experimentally investigated. This work is reported for Reynolds number, Re = 330–2850 and Prandtl number, Pr = 4.5–5.0. The present experimental investigation is carried out for mass flow rate, ṁ=0.63-1.35kg/s, volume flow rate same for both hot and cold fluid, V̇ = 2000–5000 LPH and mixed chevron angle for chevron plates (30° and 60° plates alternatively). Multi-pass arrangements are made for the equal number of pass for both hot and cold fluids with counter flow arrangements. The present study brings about the effect of an increasing number of pass on the thermo-hydraulic behaviour of PHE. The results show that with a high number of the pass, increase in velocity may be counterproductive in terms of effectiveness and Nusselt number enhancement at the same mass flow rate condition. However, for the same NTU condition higher number of pass brings to decrement in the effectiveness of PHEs. On the basis of experimental data, correlations have been proposed for Nusselt number, effectiveness and friction factor individually for each 1–1, 2–2, 3–3 and 4–4 pass arrangements of PHE.

Cooling and condensation heat transfer and pressure drop of a refrigerant at high pressures in a chevron-type plate heat exchanger with high chevron angle

Cooling and condensation heat transfer and pressure drop of a refrigerant at high pressures in a chevron-type plate heat exchanger with high chevron angle

Investigation of heat transfer and hydraulic resistance in small-scale pillow-plate heat exchangers

Pillow-Plate Heat Exchangers (PPHEs) represent an innovative equipment type, with space-effective, light and pressure-resistant construction. In this work, an experimental study of air cooling by water in small-scale PPHEs was carried out and an analysis of the hydraulic resistance and heat transfer was performed based on the experimental data. A semi-empirical correlation for friction factor inside pillow-plate panels which is based on main geometric parameters is proposed. This correlation is reliable in a wide range of Reynolds numbers, both for laminar and turbulent flow regime. For the external channel between pillow-plate panels, the correlations for pressure drop and heat transfer were obtained based on experimental data. The CFD simulations were carried out to investigate heat transfer in the external channel of the PPHE. The deviation between the experimental and simulated values of heat transfer coefficient is maximum 17%. The received correlations enable to calculate the overall heat transfer and pressure drop in small-scale PPHEs and can be applied for preliminary design of PPHEs. The case study of the PPHE application for water heating is considered. The designed heat exchanger with minimal heat transfer area has 30% less surface area then chevron-type plate heat exchangers traditionally used for such application.

An approach for pillow plate heat exchangers design for single-phase applications

Pillow-plate heat exchangers (PPHEs) represent a novel equipment type. For their application in industry, reliable preliminary design techniques are required. In this article, the existing methods for heat exchangers design are analysed and the approach for selecting the PPHE design with minimal heat transfer area is proposed. It is based on the mathematical model of thermal and hydraulic PPHE behaviour, in which the overall heat transfer coefficient and pressure drop in PPHEs are expressed through the fluid velocity. The estimation of fluid velocities in PPHE channels is based on the condition that the predefined allowable pressure drop is fully exploited. Two case studies for water heating and crude oil preheat train operating conditions are discussed, in which the flowrates of the fluids on the hot and cold sides differ significantly. The PPHE design with minimal heat transfer area for the considered case studies is presented, with specified pillow-plate geometry parameters and distance between pillow-plate panels. The resulting pressure drops and velocities in PPHEs channels as well as the obtained heat transfer surface areas are compared with existing data for chevron-type plate heat exchangers (PHEs) designed for the same operating conditions. This comparison shows that PPHEs have higher velocities in channels, longer plates and lower heat transfer area. It can be concluded that PPHEs can be successfully used for operating conditions, under which the flow rates for hot and cold fluid are significantly different and the application of chevron-type PHEs with single-pass arrangement is complicated.

Effect of the Chevron Angle on Cooling Heat Transfer Characteristics of Supercritical Pressure Fluids in Plate Heat Exchangers

ABSTRACTFor the development of industrial heat pump systems supplying a high-temperature heat source over 130°C, the authors have studied on cooling heat transfer of supercritical pressure fluids flowing in chevron-type plate heat exchangers (PHEs). In this study, to examine the effect of chevron angle on cooling heat transfer of supercritical pressure refrigerants, experiments were conducted for HFC134a and HFO1234ze(E) flowing in the PHEs with the chevron angles from 30° to 65°. In the experiments, cooling heat transfer coefficients were obtained in the wide range of bulk fluid enthalpy from vapor-like high temperature to liquid-like low temperature, changing the pressure in the reduced pressure range from 1.01 to 1.2 at the mass flow rates of 7 and 11 kg/min. Especially for the enthalpy region of the pseudo critical point and its vicinity in which good heat transfer appeared, the effect of chevron angle on heat transfer of supercritical pressure fluids was clarified based on the measurements. Furthermore, the effect of chevron angle was examined for the wide angle range from 0° to 90° with estimating the heat transfer coefficient for the angles 0° and 90° from appropriate correlations. Besides, the present data were compared with some conventional heat transfer correlations.

Experiment and numerical simulation of flow characteristics in chevron type plate heat exchangers

Experiment and numerical simulation of flow characteristics in chevron type plate heat exchangers

Thermal and hydraulic optimization of plate heat exchanger using multi objective genetic algorithm

In this paper thermal and hydraulic optimization of water to water chevron type plate heat exchanger is presented. The optimization is performed using the multi objective genetic algorithm in MATLAB optimization environment. Constrain matrix is a set of different geometrical parameters of plate heat exchanger within the logical bounds. The two objective functions are pressure drop of hot side and heat transfer. Due to conflicting nature of these objective functions, no single solution can satisfy both of the objective function simultaneously. The increase in heat transfer will results in increase in pressure drop, therefore, optimization results are presented as Pareto Front. Multi objective genetic algorithm tool was employed to find a set of optimum solution which was trade-off between pressure drop and heat transfer. At the end, sensitivity analysis was performed to analyse the effect of geometrical parameters of heat exchanger on thermal and hydraulic performance. The sensitivity results show that the heat transfer and pressure drop are greatly affected by the vertical port centre distance, plate spacing and number of thermal plates.