Plate Heat Exchanger Research Articles

Pulsating heat pipe performance enhancement through porous metallic surfaces produced via physical dealloying

Physical dealloying (PD) is explored in this work as a way of creating a porous layer on metallic surfaces to be used for the enhancement of Pulsating Heat Pipe (PHP) thermal performances. PD can be applied to metal alloys consisting of components with a high difference between their partial vapour pressure, such as copper and zinc. Commercially available brass (Cu/Zn alloy) capillary tubes with OD = 2 mm and ID = 1.3 mm were shaped into a four-turn PHP, with a total length of 949 mm. One standard PHP with the same tube diameter, number of turns and total length was tested as benchmark, while other two PHPs were subjected to PD for 0.5 and 2 h, respectively. All PHPs were tested in the range of heat load between 3 and 40 W at a fixed 50 % filling ratio with ethanol as working fluid. The performed tests show that PHPs after PD display up to 30 °C lower average temperature at the evaporator and up to 7 °C lower average temperature of the condenser compared to the benchmark. PD was capable to lower the PHP thermal resistance by up to 4.2 times, from 11.2 to 2.65 K/W, at low heat powers. Furthermore, in the case of PD-treated PHP, the start-up takes place at lower power and temperatures when compared to untreated PHP. This characteristic holds significant value as it expands the range of applications for PHPs, while simultaneously enhancing their reliability, safety, and overall lifespan when used for thermal management in equipment. It is worth noting that this straightforward approach can be tailored for a wide range of thermal management equipment, including conventional, plate, and micro heat exchangers, as well as HVAC systems. This method is particularly suitable for situations where heat transfer takes place through phase change processes.

The Hydrothermal Performance Investigation of Gasketed Plate Heat Exchangers Using Taguchi, ANOVA, and GRA Methods

The Hydrothermal Performance Investigation of Gasketed Plate Heat Exchangers Using Taguchi, ANOVA, and GRA Methods

Heat recovery analysis of a fixed plate energy recovery ventilator

As building becomes more leak-tight, air refreshment to improve indoor air quality is needed for healthy living standards. In the quest to ensure comfortable indoor climatic conditions, energy recovery ventilators (ERV) are used to provide air refreshment and thermal comfort. In this study, a fixed plate air-to-air ERV was analysed to determine its effectivity in terms of energy recovery during air refreshment. A customized test bench was built and used to acquire the instantaneous surface temperatures of the heat exchanger plates contained in the ERV during air refreshment. Also, a numerical model of the ERV was developed and validated by comparing its output from simulation with experiment results under the same conditions. The model consisted of a single heat exchanger plate and the air across the plate surface. To capture the effect of heat transfer between the air and the heat exchanger plate in 3D, the model was discretized into numerous cells. From the experiment and simulation results, the air-to-air ERVs were more effective in recovering thermal energy at low flow velocity than at high flow velocity. At lower flow velocity, it will take a longer time duration before any significant impact is made on the thermal conditions of the building, comparatively. The prediction of the model was within acceptable margins and could be used to provide insight on the ERVs performance improvement.

Dynamic simulation of a combined solar system including phase change material storage and its experimental validation

Thermal energy storage is a key issue in efficient energy system applications, especially in renewable energies. In this respect, phase change materials (PCM) have attracted interest as an active solution for efficient energy management, particularly in the building sector. This paper presents a modelling of a PCM thermal battery in solar system assisted by heat pump. The storage stores the heat produced by unglazed solar panels (Batisol®) and releases it into a heat pump. Then this heat is sent to two other PCM storages. In this way, the low-temperature heating and domestic hot water needs of a commercial building in winter are met. The storage consists of a block of PCM contained between two plates of heat transfer fluid. It acts as a plate heat exchanger that can be charged and discharged simultaneously. The objective of the study is to dynamically simulate the thermal behaviour of this storage for different hot inlet temperature profiles. A rectangular profile is used to validate the model using experimental results. Then, a solar system assisted by heat pump and three PCM storages is dynamically simulated. This 2D model would be useful to validate a simpler model for optimising the operational parameters of the system.

Evaporation of Binary Mixtures in a Pillow Plate Thermosiphon Reboiler

AbstractPillow plate heat exchangers show promising performance in extending the operating range of thermosiphon reboilers. Here, the evaporation of binary mixtures during natural circulation evaporation in a pillow plate apparatus was investigated. The experimental results show that the thermal performance is dominated by mixture effects and a component system‐dependent minimum is found. The model approach according to Bennett and Chen has proven to reliably estimate the product‐side heat transfer coefficient for pure substances and mixtures with a low boiling point distance. For wide‐boiling mixtures and low pressures the approach must be adjusted.

Squeezing hydromagnetic nanofluid flow between two parallel plates with joule heating effects and induced magnetic field

Over the years, cooling high energy devices has become a major challenge to most industries. Thus, squeezing hydromagnetic nanofluid flow between two parallel plates has garnered alot of attention. In the present study, an unsteady, incompressible, hydromagnetic gold and water nanofluid flow squeezed between two parallel plates with Joule heating and a magnetic field that is induced is considered. The model considers the impacts of Joule heating,Viscous dissipation and induced magnetic field. In contrast with other studies which may have focussed on only one or two of these aspects this comprehensive approach provides a more accurate depiction of the flow pattern. Employing the finite difference method, the flow's non-linear differential equations are numerically solved and then implemented in MATLAB. The effect of changing various parameters on flow variables such as velocity, magnetic induction and thermal profiles are determined and the results obtained are presented graphically. Increasing magnetic parameter and Prandtl magnetic number caused a decline in temperature,velocity and magnetic induction profiles. Further, increasing the Eckert number and Joule heating parameter lead to an increase in temperature profiles. This findings have a direct impact on high-energy cooling devices which frequently experience heat dissipation. Additionally, engineers can ensure optimal performance and the longevity of plate heat exchangers in industries.

Effect of liquid-vapor two-phase flow maldistribution on the thermal performance of brazed plate heat exchangers

The effect of liquid-vapor two-phase flow maldistribution on the thermal performance of brazed plate heat exchangers (BPHEs) is investigated experimentally and numerically. The two-phase refrigerant flow distributions among different channels of the BPHEs are first experimentally quantified based on the infrared radiation images of the heat exchanger sidewalls. To assess the performance degradation due to two-phase flow maldistribution, the thermal performance of the maldistributed BPHEs is measured and compared with that of the uniform-distributed BPHEs, predicted using an experimentally validated BPHE model. Several factors that affect the performance degradation are analyzed, including refrigerant inlet vapor quality and flow rate, exit superheat, and water-side flow distribution. The results show that, under the tested conditions, the two-phase refrigerant flow maldistribution causes up to a 29.8 % degradation in heat exchanger capacity and a 4 K decrease in evaporation temperature. Furthermore, the vulnerability of the BPHEs to two-phase flow maldistribution is significantly influenced by the operating conditions. This is closely related to the varying size ratios of superheated and two-phase regions within the BPHEs under different operating conditions. Reducing the refrigerant exit superheat is verified to help overcome the adverse effect brought by the flow maldistribution in the evaporators, but brings challenges in the system control. Matching the flow distributions of liquid refrigerant and water also proves beneficial to the BPHE evaporators.

Thermal performance comparison of vertical and diagonal flow configurations in corrugated plate heat exchanger

Thermal performance comparison of vertical and diagonal flow configurations in corrugated plate heat exchanger

Optimizing thermal efficiency: Advancements in flat plate heat exchanger performance through baffle integration

Compact heat exchangers have been gaining popularity in many industrial applications. Various types of passive turbulising structures such as corrugations, protrusions and ribs are introduced in the flow path to increase the effective heat transfer area and the level of turbulence in the flow path. This study investigates the impact of introduction of baffles on the performance of PHEs in terms of flow characteristics, pressure drop, and heat transfer. Two distinct types of baffle structures, namely wedge and aerofoil configurations, were introduced at varying numbers - 1, 3, and 5. An extensive experimentation is conducted for a FPHE in a thermal power plant of 500 × 2 MW and various flow and thermal parameters are measured. Computational Fluid Dynamics is utilized in this study to find the optimum baffle configuration. A detailed validation study is executed to obtain the correct computational algorithm, that is the right mesh count, optimum turbulence model, and precise numerical algorithm by comparing the numerical results with the available experimental results. Wedge- type baffles create increased turbulence and pressure drop, while aerofoil-type baffles minimize stagnation and exhibit lower pressure drop. Both baffle configurations lead to a substantial increase in heat transfer, with the 5-wedge-baffle setup showing the highest up to a 55% enhancement of Nusselt number. The Performance Evaluation Criterion (PEC) of wedge and aerofoil type is about 1.24 to 1.3 and 1.22 to 1.24 to that of conventional one respectively.

Effect of the surface form of the herringbone aluminum plate in a plate heat exchanger on the boiling heat transfer performance of ammonia

In this study, ammonia boiling heat transfer coefficient and the overall heat transfer were measured in a plate evaporator for an ocean thermal energy conversion (OTEC) system using aluminum plates. The OTEC system used ammonia as the working and a plate heat exchanger (PHE) that combined titanium plates. In this study, we used an anodized aluminum herringbone plate with two chevron angles of 45 and 60° installed in a PHE and measured the boiling heat transfer coefficients of ammonia and overall heat transfer coefficients for both plates to compare their heat transfer performances. The experimental conditions included a hot water flow rate of 1 – 12 L/min, a working fluid mass flux of 7 – 30 kg/m2s, a hot water inlet temperature of 30 – 40 °C, and a system pressure of 700 kPa.It was observed that anodized aluminum can be used as a heat-transfer plate for the PHE. In addition, the maximum overall heat transfer coefficient of chevron angle of 45° was 4 kW/m2K, and that of 60° was 3.5 kW/m2K, respectively. The maximum ammonia boiling heat transfer coefficient of 45° was 12.5 kW/m2K, and that of 60° was 13 kW/m2K, respectively. The heat transfer coefficient values are similar. Additionally, the correlation between the nondimensional heat transfer and the Lockhart-Martinelli parameter of aluminum plates was also clarified for comparison with the previous ammonia plate heat transfer in a flat plate. By comparing the correlation equations, the aluminum plate exhibited a value twice that of the flat plate.

Thermally Induced Moisture Flow in a Silty Sand under a 1-D Thermal Gradient

Thermally induced moisture flow in unsaturated soils involves complex coupled thermal–hydro processes with the moisture flow in both the vapor and liquid phases. The accurate measurement of the moisture flow in unsaturated sands remains a challenging task due to low moisture migration, the temperature effect on moisture sensors, and the gravity effect on moisture flow. This study aims to accurately measure transient moisture flow, heat transfer, and thermal conductivity in a silty sand with 35% non-plastic fines in a closed heat cell with a controlled 1-D temperature gradient. The heat cell consists of two temperature-controlled heat exchanger plates, heat flux sensors, moisture sensors, thermocouples, and thermal conductivity sensors. The soil moisture sensors were calibrated in the test soil at room temperature and then at elevated incremental temperatures. Soil samples compacted at various initial moisture contents were tested under a constant 1-D temperature gradient of 4 °C/cm. Soil moisture redistribution, temperature, and thermal conductivity profiles were determined from the test results. Transient temperature responses indicated that a lower initial moisture content led to a higher temperature drop after reaching the peak, or a more concaved temperature profile in a steady state due to enhanced moisture migration driven by the temperature gradients. Dry soils exhibited uniform thermal properties, while moist soils showed varying thermal conductivity profiles. A critical moisture content was identified when the maximum moisture migration occurred. Thermal conductivity in soils increased with the distance from the heat source due to thermally induced moisture migration. These findings provide valuable insights into coupled moisture–heat flow dynamics in unsaturated sands.

Comparative Study of Heat Transfer and Flow Friction in Plate Heat Exchangers with CarboxyMethyl Cellulose and Sodium Alginate

Abstract: Study of Plate heat exchanger (PHE) with power law fluid is a very interesting topic now a days as there is improvement of thermal performance of heat exchanger. Power law fluids show complex flow behavior due to its rheological properties. The parameters which differ these power law fluids from Newtonian fluids are rheological properties like flow behavior index and power law index. Hence flow behavior index and power law index are the two parameters which affect the heat transfer rate. Now to enhance rate of heat transfer we should know how Nusselt number changes with change in flow behavior index and power law index. Hence the aim of present study was to observe how Nusselt number and friction factor changes with change in flow behavior index and power law index. For this purpose thermal performance of PHE have been studied with CorboxyMethyl Cellulose (CMC) and sodium alginate as a cold fluids. Comparison of Nusselt number and friction factor of CMC and sodium alginate have been done. It was observed that Nusselt number for CMC solution was more compared to sodium alginate solution with less friction factor than sodium alginate.

Experimental Study on the Impact of Lubricant on the Performance of Gravity-Assisted Separated Heat Pipe

Gravity-assisted separation heat pipes (GSHPs) are extensively utilized in telecommunications base stations and data centers. To ensure year-round cooling, integrating GSHPs directly with a vapor compression refrigeration system is a viable solution. It is unavoidable that the refrigeration system’s lubricant will infiltrate the heat pipe loop, thereby affecting its thermal performance. This paper examines the performance of a GSHP, which features a water-cooled plate heat exchanger as the condenser and a finned-tube heat exchanger as the evaporator, when the working fluid (R134a) is contaminated with a lubricant (POE, Emkarate RL-46H). The findings are compared with those from a system free of lubricant. The experimental outcomes indicate that the presence of lubricant degrades the heat transfer efficiency, particularly when the filling ratio is adequate and no significant superheat is observed at the evaporator’s outlet. This results in a 3.86% increase in heat transfer resistance. When the charge of the working fluid is suboptimal, the average heat transfer resistance remains relatively constant at a 3% lubricant concentration yet increases to approximately 5.27% at a 4–6% lubricant concentration, and further to 12.32% at a 9% lubricant concentration. Concurrently, as the lubricant concentration fluctuates between 3% and 9%, the oil circulation ratio (OCR) varies from 0.02% to 0.11%.

Effect of Chevron Angles on the Thermal Performance of Corrugated Plate Heat Exchanger (CPHEs)

Corrugated plate heat exchangers (CPHEs) possess a greater surface area for heat transfer and a heightened level of turbulence as a result of the corrugations. This study presents an experimental analysis comparing the thermal performance of a flat plate heat exchanger and a corrugated plate heat exchanger (CPHE) with varied corrugation angles. The analysis was conducted using water as the test fluid. The comprehensive testing has been carried out on CPHEs with different chevron angles (β) of 30°/30°, 45°/45°, and 60°/60°. Experimental data is collected under steady- state conditions, with a single phase (water-water) system, covering Reynolds numbers (Re) ranging from 900 to 1250. The test fluid's mass flow rate, ranging from 0.05 to 0.16 kilograms per second, is measured together with the accompanying steady state temperatures. Each plate was equipped with four thermocouple sensors to detect the bulk temperature of the cold and hot fluids at the intake and output. The performance was evaluated using both parallel and counterflow configurations. Experimental observations are utilized to estimate the temperature difference (∆T) between the inlet and output streams, the logarithmic mean temperature difference (LMTD), and the exergy (E). The measured ∆T and E values for corrugation angles (30°, 45°, and 60°) of CPHE were compared to those of flat plate heat exchangers. For corrugation angles of 30°, 45°, and 60°, the values of ∆T and E (efficiency) increase as the mass flow rate of the fluid increases. An increase in the corrugation angle leads to an increase in turbulence in the flow, which in turn enhances heat transmission. In addition, the thermal effectiveness (ε) was calculated using the NTU method and compared for all of the plates. Key Words: Corrugated plate heat exchanger, Thermal performance, Chevron angle, heat transfer coefficient.

Measurement of local boiling heat transfer coefficient (HTC) within a brazed plate heat exchanger (BPHE) and heat transfer assessment of low-GWP R134a replacements

This article shows the local boiling HTCs of R134a and three low-GWP replacements, R1234yf, R1234ze(E) and R152a within a (BPHE). The experimentation was performed in a test-section specially set up for the measurement of the local two-phase HTC at a saturation temperature of 10 °C, with a refrigerant mass velocity from 9.5 to 35.2 kg m−2 s−1, incoming vapour quality between 0.2 and 0.3 and almost complete vaporisation. Both nucleate boiling and forced-convection boiling play an important role in these tests, depending, mainly, on the location along the plate. The comparison with theoretical models shows that both Longo et al. (2015) and Amalfi et al. (2016) models reproduce very well the experimental HTCs. The measurement of local temperature profiles within the BPHE allows to couple the evaluation of thermal and hydraulic performances of refrigerants into a single parameter named Total Temperature Penalty (TTP). The TTP analysis highlights similar boiling performance for R134a, R1234yf and R152a refrigerants, while R1234ze(E) displays worse performance.

Design of the Cooling Water System Upgrade for 42 T Resistive Magnet at the CHMFL

Abstract To meet the operation requirements of the 42 T resistive magnet which will be built by the Chinese High Magnetic Field Laboratory (CHMFL) in the future, the cooling water system needs to be upgraded accordingly. The cooling water system will improve its performance based on the existing cooling system. This article will make a detailed analysis of the system upgrading and transformation plan. In terms of refrigeration, to meet the requirements of larger refrigeration temperature difference, a new centrifugal chiller with large temperature difference will be added in series with the existing unit of refrigeration. With the increase in heat load, the system will connect a new plate heat exchanger in parallel on the basis of the original heat exchange capacity. However, the circulating cooling water flowrate of the 42 T resistive magnet is expected to exceed 1200 m3/h, the purification flowrate of the deionized water also needs to be upgraded, and the purification ratio is expected to reach more than 6%. In addition, the control system will be also combined with the new equipment and pipelines to realize a variety of chilled water storage and supply modes to better meet the operation of the new-built magnet.

The effect of operating conditions on heat transfer for parallel plate heat exchangers of thermoacoustic standing wave systems

Thermoacoustic systems represent a promising technology for clean cooling and/or power generation. However, understanding of the behavior of oscillatory flow inside the system under high drive ratio operating conditions, at elevated mean pressures, range of frequencies, and high flow amplitudes, remains limited and poses challenges for designing efficient systems with minimal losses. This paper presents a numerical investigation into the flow and heat transfer characteristics across a coupled cold and hot parallel-plate heat exchanger operating under standing-wave type oscillatory flow conditions. The models were developed for various conditions, spanning frequencies from 13 Hz to 100 Hz and mean pressures between 1 and 20 bar, using both nitrogen and helium as working fluids. The study reveals significant phenomena such as heat accumulation and annular effects in both temperature and velocity/vorticity fields. These findings were discussed in the context of their impact on the heat transfer performance of the heat exchanger. Specifically, the emergence of vortices was examined in relation to mean pressure, alongside jet-like velocity profiles and natural convection effects. Furthermore, the paper includes a comparative analysis between the heat transfer model employed in this study and previous works, aiming to validate the findings. This research enhances the understanding of fluid dynamics and heat transfer phenomena within heat exchangers of thermoacoustic devices, thereby contributing to advancements in future design improvements.

Energy expenditure in the Z-type plate heat and mass exchanger based on the concept of heat-integrated distillation column

Thermal separation of substances typically involves the use of rectification columns equipped with condensers and reboilers. This conventional method is notably energy-intensive, necessitating substantial heat input to the reboiler and leading to significant waste heat discharge through the condenser into the environment. This paper presents our further study on an innovative alternative technology for thermal separation. The proposed approach involves conducting thermal separation within flow channels of a Heat and Mass Exchanger (HME), which are composed of plates with intricate geometries. In this system, heat distribution is maintained through the diaphragm, i.e., the channel walls, facilitating both heat exchange and simultaneous thermal separation of substances.This paper focuses on both laboratory and numerical investigations of two-phase flow within various channel geometries. Experimentally, four distinct channel designs were examined using an air–water mixture, aiming to identify a new geometry that facilitates countercurrent flow patterns in this challenging substance combination. The experimental phase led to the selection of a channel geometry that demonstrated the most effective countercurrent flow for intensive cases, then used for ethane-ethylene mixture. Subsequently, this selected geometry was subjected to numerical calculations using the mathematical model of the Heat and Mass Exchanger (HME). These calculations encompassed flow dynamics, thermal behavior, and the sizing of the HME, tailored specifically for the newly identified channel geometry.

Characterisation of a plate heat exchanger working as condenser. Comparative analysis

This paper presents a method to evaluate the heating capacity of a plate heat exchanger working as condenser. As in previous works with phe evaporators and single phase heat exchangers, the proposed methodology relays on a discretisation of the heat exchanger in cells, in such a way that the outlet temperature is assumed and the heat transferred is calculated by integrating along the heat exchanger by means of a 1D approach which allows us to determine the outlet variables iteratively based on a heat transfer area calculation.The input variables of the model are pressure, enthalpy, and flow rate of both fluids at the inlet of the heat exchanger .The study presents the method, pays attention the heat transfer coefficient correlations utilised, and is used to comparatively determine the heat transferred by the refrigerant to the secondary fluid. Experimental results are used for validation and to analyse the goodness of the different correlations tested. Some conclusions are finally drawn.

Local condensation heat transfer analysis of three-component mixture refrigerant R455A in plate heat exchanger

Plate heat exchangers are gaining popularity as condensers for their compact design and high efficiency. However, the uneven fluid distribution in channels poses a challenge to effective heat transfer. Existing literature lacks experimental analysis of local heat transfer coefficients for pure and zeotropic mixture refrigerants in plate heat exchangers. This study experimentally analyzed the local heat transfer of the three-component zeotropic mixture R455A at various conditions (mass flux 20, 30, and 50 kg m−2 s−1 and saturation temperatures 30 and 35 °C). Results show that the heat transfer coefficient increases with flow rates and decreases with saturation temperature. However, results indicated lower heat transfer coefficients compared to pure refrigerants due to mixture effects. In addition, the local distribution of the heat transfer coefficient revealed that the heat transfer coefficient is highest at the center compared to the edges of the channel due uneven distribution of refrigerants within the channel. This HTC pattern confirms an asymmetrical flow within the plate. A new correlation is being developed to predict the heat transfer coefficient of the ternary mixture, showing improved accuracy than previously proposed correlations.