Brazed Plate Heat Exchanger Research Articles

Thermal-hydraulic performance of R1234yf in brazed plate heat exchanger at low saturation temperature and mass flux conditions: Experimental investigation

This study investigated the heat transfer coefficient (hr) and two-phase frictional pressure drop during the evaporation of R1234yf within an offset strip fin (OSF)-structured brazed plate heat exchanger (BPHE). The work is conducted at a saturation temperature (Ts) of −3 to 3 °C, with mass flux (G) ranging from 25 to 45 kg m−2 s−1 and heat flux (q) between 15 and 23 kW m−2 across a vapor quality (x) range of 0.1–0.8. Understanding these behaviors is critical for optimizing BPHEs in low-temperature applications, such as heat pumps, where energy efficiency is essential. The novelty of this work lies in its exploration of operating conditions that are less studied in the literature, particularly the impact of low Ts, low G, and high q on hr and two-phase frictional pressure drop in an OSF-BPHE with R1234yf. Unlike prior studies focusing on convection-dominated boiling, our findings reveal a coexistence of nucleate and convective boiling mechanisms, especially at different vapor qualities. The hr is significantly influenced by q at x < 0.6, G at x > 0.6, and Ts across all x. In contrast, evidence of dryout at high x highlights the importance of these parameters in managing heat transfer efficiency. The results indicate a strong correlation between the two-phase frictional pressure drop and G, with a marked increase in it at higher G. Besides, this study reveals flow characteristics commonly linked with both macrochannel and minichannel flows, enhancing novelty by bridging the gap between these two regimes. These findings challenge existing literature correlations that predominantly emphasize convection-dominated behavior and contribute to a better understanding of the dual boiling mechanisms in BPHEs.

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.

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.

Comparative analysis of R290 and R1234yf cooling performance in offset strip-fin plate heat exchanger for electric-vehicle battery thermal management

This study compares the performances of two-phase refrigerant cooling (TPRC) using two refrigerants, namely R290 and R1234yf, in battery thermal management systems. A compact and energy-efficient brazed plate heat exchanger with an offset strip fin is employed as a cold-plate evaporator and experiments are conducted to examine its heat-transfer characteristics. Key performance parameters including the heat-transfer coefficient (HTC), pressure drop (PD), and wall temperature (Tw) are assessed at discharge rates (C-rates) of 1, 1.25, and 1.5C, saturation temperatures (Tsat) of 16 °C and 20 °C, the mass flux of 50 kg/m2s, and inlet vapor-quality values of 0.1–0.8. The results show that R290 offers a higher HTC and lower PD for all C-rates compared with R1234yf for Tsat = 16 °C and 20 °C. The HTC increases by 107%–113% for 1.5–1C at Tsat = 16 °C, and 84% (1.5 and 1C) and 70% (1.25C) at 20 °C. Similarly, the PD decreases by 6.7%–10.1% for 1–1.5C at Tsat = 16 °C and approximately 10% for all C-rates at 20 °C. Compared with R1234yf, R290 maintains a Tw that is 1.1 °C and 0.7 °C lower at Tsat = 16 °C and 20 °C, respectively. Results of critical heat transfer coefficient (CHTC) analysis confirm that R290 performs better than R1234yf at Tsat = 16 °C in terms of HTC increment and Tw reduction and that the critical HTC of R290 is higher than that of R1234yf by 80% and 40% for Tsat = 16 °C and 20 °C, respectively. Additionally, using R290 instead of R1234yf in the TPRC system yields a higher level of cooling efficiency at vapor-quality values of 0.4–0.5. In addition, an artificial neural network model is used to predict the experimental results, where a root-mean-square error of 2.3%–3.5% is indicated. Using this trained model, the HTC and PD are predicated at intermediate C-rates (1.1–1.4C) and the results are discussed.

Flow boiling of R32 and R410A inside brazed plate heat exchangers with different geometries

A proposed midterm substitute of R410A, mixture with 1924 GWP100 (Global Warming Potential over 100 years), is R32 (GWP100 = 677), which, although mildly flammable, is pure, relatively cheap, already available on the market, with different suppliers due to the absence of patents. Moreover, its thermo-physical properties are already well known. Increasingly stringent energy saving regulations are boosting the residential heat pump market, which typically requires reversible brazed plate heat exchangers to be used both as evaporators and condensers. This work reports an experimental analysis of the two refrigerants during flow boiling in brazed plate heat exchangers, varying the channel volumes. The number of plates of the heat exchangers ranges from 4 (1 refrigerant channel) to 120 (59 refrigerant channels in parallel). The heat transfer coefficient and the pressure drop have been measured for R410A and R32 at saturation temperature between 1.5 °C and 5.5 °C, outlet vapour superheating of 5 K, heat flux from 4 to 31 kW m−2, mass velocity from 8 to 87 kg m−2 s−1 and inlet channels vapour quality from 0.2 to 0.3. The number of plates affects the distribution of the liquid-vapour mixture in the channels and its effect is discussed by comparing the heat transfer coefficients. It is shown that the differences in performance between the two fluids increase with the mass velocity, suggesting the influence of a convective component on the heat transfer coefficient. This is further confirmed by comparing the data with the results of two different models from literature.

Thermal−hydraulic characteristics of R32 and R410A condensation in plate heat exchangers with 1 mm chevron depth

Compact brazed plate heat exchangers (BPHEs) with low chevron depths are widely used in new heat pumps and air-conditioners for reducing inventory and improving efficiency. This study analyses the complete condensation of R410A and R32 inside BPHEs with a chevron depth of 1 mm. The effects of the mass flux and chevron patterns (V-shaped and W-shaped) on the heat transfer coefficient (HTC) and frictional pressure drop are investigated. The HTC of R32 is 30–50 % higher than that of R410A, which has a 10–20 % higher friction factor at high mass fluxes and vice versa at low mass fluxes. The HTC of R410A monotonically increases with the mass flux, whereas that of R32 does not. The W-shaped pattern results in 30 % and 15 % higher pressure drops compared with the V-shaped pattern for R410A and R32, respectively. The friction factor of R32 decreases more sharply than that of R410A as the mass flux increases, particularly at low mass fluxes. The correlations developed by Longo et al. and Zhang et al. show the best agreement with the experimental data for the HTCs of R32 and R410A, respectively, with mean absolute percentage deviations (MAPDs) of 15 %. The friction factor correlation of Zhang et al. accurately predicts the pressure drop of R32 for the W-shaped and V-shaped patterns. In addition, it accurately predicts the pressure drop of R410A for the W-shaped pattern, with an MAPD of less than 10 %, but over-estimates it by 37 % for the V-shaped pattern.

Evaporation performance of propane in offset strip-fin plate heat exchanger for refrigerant-based battery thermal management in electric vehicles

This study investigates the potential of refrigerant-based cooling (RC) using a natural refrigerant (propane) and lightweight energy-efficient brazed plate heat exchangers (PHXs) in the battery thermal management systems (BTMSs) of the electric vehicles (EVs). Experimental assessments were conducted to analyze the evaporative heat transfer characteristics of propane within an offset strip-fin flow-structured PHX under various operational conditions resembling the BTMS operation. The battery discharge rates, often represented by the C-rate, are determined by the discharging current relative to the battery's capacity. In this study, a heat generation model based on the C-rate was employed to evaluate the thermal performance of the battery. Parameters, such as mass flux (G) at 30–70 kg/m2s, discharge rates (C-rate) of 1, 1.25, and 1.5C, and saturation temperatures (Tsat) of 16–24 °C were explored, with the inlet vapor quality (xin) in the range of 0.1–0.8. The influence of G and Tsat on the heat transfer performance showed that higher G values (60 and 70 kg/m2s) achieved the maximum heat transfer coefficients (HTC), which resulted in impractical pressure drops (PD). While higher HTC and lower PD were observed at a Tsat of 24 °C, concerns about increased inner wall temperature (Tiw) and safety emerged at this temperature. Hence, the optimum conditions of G (30 and 50 kg/m2s) and Tsat (16 and 20 °C) were investigated. The average HTC increased by 29, 27, and 21 % at 50 kg/m2s compared to that at 30 kg/m2s with Tsat of 20 °C, resulting in an average of 0.7, 0.9, and 1.2 °C reduction in the Tiw for C-rates of 1.5, 1.25, and 1C respectively. Compared to the Tsat of 16 °C, higher HTC and lower PD were observed at 20 °C, however, the Tiw was in the range of 21.12–20.47 °C for Tsat of 20 °C, which is 3.5–4 °C higher than that at Tsat of 16 °C. The results from the critical heat transfer coefficient analysis showed that the peak heat dissipation with minimal wall temperature was attained with optimal xm of 0.45–0.5, which enhanced the cooling efficiency for both the G values of 30 and 50 kg/m2s, and both the Tsat values (16 and 20 °C).

Seasonal performance assessment and experimental investigation of R32 drop-in and BPHX size in an R410A chiller when using two compressor modulation strategies

The decrease in fossil fuel reserves and high energy consumption by HVAC&R equipment require the use of compressors with better efficiencies and capacity modulation strategies. Usually, seasonal performance studies focus on compressor capacity modulation methods, however the current study explores the idea of improving the seasonal performance of two compressor modulation techniques: a two-stage and a variable speed compressor with different capacity modulation ranges by using larger condensers in an R410A water ethylene glycol chiller system. The analysis shows that oversizing the heat exchangers has larger benefits with the compressor modulation strategy with lower range. Additionally, the seasonal performance estimated according to AHRI 551/591 (2020) of a two-stage compressor with oversized condenser is higher than a basic single speed compressor with a better motor indicating that oversizing brazed plate heat exchanger (BPHX) might yield higher performance than improving the compressor motor efficiency. Due to the high global warming potential (GWP) of R410A, there is a focus on replacing it with low GWP refrigerants such as R32 to reduce CO2 emissions. This study would also compare the performance when using R32 as a drop-in refrigerant in the two different R410A compressor capacity modulation strategies with comparable cooling capacity. When the refrigerant was changed from R410A to R32, the integrated part load value (IPLV.SI), an efficiency metric for variable speed compressor remains relatively constant at 5.5 while it increases from 3.9 to 4.4 for the two-stage compressor. It is hypothesized that low refrigerant mass flow rate (m˙ref) provided by the variable speed compressor when matching the load at the lower part load conditions leads to refrigerant maldistribution in BPHX and reduced IPLV.SI.

Experimental analysis of a tri-partite brazed plate gas cooler for CO2 heat pump water heaters

Gas cooler is a crucial component in CO2 systems, and its performance significantly influences the overall efficiency of the CO2-based heat pump system. Brazed plate heat exchangers feature a compact design, reduced refrigerant charge, enhanced heat transfer coefficient, and lower pressure drop, resulting in space savings and improved system performance. This experimental study investigates a water-cooled tri-partite brazed plate gas cooler in a CO2 heat pump. The tri-partite brazed plate gas cooler has a double effect: it allows matching the temperature glide of CO2 with that of water and meeting the requirements for both domestic hot water and space heating simultaneously. The experiments are conducted in only domestic hot water and combined space and domestic hot water operative modes. The effects of different operating parameters on heat duty, supply temperature, temperature approach, and pinch point location are evaluated. The actual conductance of gas coolers is calculated, and a new definition is adopted to determine the ϵ−NTU of gas coolers. Results show that preheating gas cooler (GC3) has a higher heat duty at pressures near the critical pressure. As the inlet pressure increases, the domestic hot water supply temperature increases, the pinch point moves to the cold end of GC3, and the temperature approach decreases. The LMTD method may result in an undersized or oversized CO2 gas cooler by up to ±50% for different pressures. The errors reach their maximum values when the temperature difference is low at the cold end and high at the hot end. The effectiveness ranges from 0.56 to 0.94 and the NTU ranges from 2.64 to 5.41. The gas cooler shows promising performance. The outcomes of this research are anticipated to serve as a valuable reference for enhancing the design and optimization of transcritical CO2 systems.

Characterization of brazed plate heat exchanger performance based on experimental and coupled heat-fluid-solid numerical simulation

A physical and mathematical model of a complete brazed plate heat exchanger (BPHE) with three layers and two channels was presented. Experiments were conducted on the BPHE using water as the fluid, and the experimental results were compared with the simulation results in terms of heat transfer efficiency and pressure drop. An analysis of the relationship between the Nusselt number and drag factor of the BPHE at a specific Reynolds was also provided, with a focus on identifying any errors. Furthermore, the internal flow and heat transfer characteristics of the BPHE were analyzed. The thermal stress and lifetime of the BPHE at different operating temperatures were simulated by using the heat-flow-solid coupling method. The results reveal that the presence of stress concentration points and the thermal stress increases while the lifetime decreases with the rise in operating temperature. In summary, the study demonstrates that the BPHE experiences stress concentration points and their intensity varies with the working temperature, thereby affecting the overall lifetime of the BPHE.

A state-of-the-art review on thermo fluid performance of brazed plate heat exchanger for HVAC application

A state-of-the-art review on thermo fluid performance of brazed plate heat exchanger for HVAC application

Numerical Simulation of a Brazed Plate Heat Exchanger using Al2O3- Water Nanofluid with Periodic Boundary Conditions

Brazed plate heat exchangers are used as evaporators, condensers, and single-phase heat exchangers in the industry. This complex piece of engineering has the effectiveness and compactness to give it an edge over many conventional heat exchangers. Solar power plants and organic Rankine cycle systems do use these heat exchangers as a part of heat recovery systems. The complex channels formed by the angled sinusoidal plates allow the fluid to be in a turbulent zone at a low Reynolds number, thus promoting better heat transfer characteristics. The challenge of simulating these heat exchangers is the large computational requirements. This can be solved by using periodic boundary conditions where a single repeating element is simulated to analyze the heat transfer characteristics of the entire channel. Varying concentrations of Al2O3 Nanofluid were considered as the working fluid for this study. The variation in the concentration did not affect the Nusselt number showing that the heat transfer coefficient was completely dependent on the hydraulic diameter and the thermal conductivity of the fluid. The friction factor also did not change with varying concentrations but the pressure drop increased as the chevron angle, pitch, and concentration increased.

Thermo-hydraulic efficiency of lung-inspired compact plate heat exchangers made using additive manufacturing techniques with steel, aluminum and titanium powders

The selection of material for compact plate heat exchangers (CPHEs) is of increasing importance due to global economic and supply constraints. Additionally, the influence of material selection on the thermo-hydraulic characteristics of CPHEs is an area of ongoing research. This study aims to address these issues by analyzing the thermo-hydraulic performance of CPHEs made from steel, aluminum, and titanium materials with small, complex channels. Using an additive manufacturing method (specifically Direct Metal Laser Sintering), lung-inspired CPHEs of identical geometry and roughness were manufactured from steel, aluminum and titanium powders. The thermo-hydraulic characteristics of CPHEs as well as that of a traditional one with Chevron-type, were investigated using both experimental and numerical techniques under specific operating conditions to determine the optimum between maximum heat transfer and minimum pressure drop. The findings of this study reveal that as the temperature difference between the inlet on the hot and cold sides, as well as the flow rate, were increased, there was a corresponding increase in both amount of heat transferred and loss of pressure across all investigated CPHEs. Compared to the chevron type brazed plate heat exchanger, the CPHE made from aluminum showed a 75.2 % and 11.2 % increase in heat transfer and a 31.8 % and 10.9 % reduction in pressure drop at 3 and 6 L/min, respectively, for a temperature difference of 90–40 °C. This study suggests that the use of materials with different thermal conductivities in CPHEs may offer a promising solution to achieve elevated heat transfer rates while minimizing pressure drop.

Thermal performance and flow analysis in a brazed plate heat exchanger using MWCNT@water/EG nanofluid

In recent years, the growth of energy consumption and the need to optimize it have drawn the attention of researchers to technologies that can increase the performance of heat transfer devices such as plate heat exchangers. One of these solutions is the use of nanoparticles in common fluids. Despite the many advantages of MWCNT, not enough attention has been paid to its application in plate heat exchangers. The purpose of this study is to investigate the thermal performance and flow of a brazed plate heat exchanger using MWCNT nanoparticles in the cooling fluid of water/Ethylene glycol. The results of the UV spectrum showed that the concentration of 0.05 wt% nanofluid has the most stability. Therefore, the tests required for the two factors of the volume flow rate of cold fluid and temperature of hot fluid were performed at three levels using the response surface method. The results show that at 55 ̊C temperature of hot fluid and volume flow rate of 23.4 l/min of cold fluid, the convection heat transfer coefficient and the heat transfer rate are increased by 20.97% and 34.3% compared with the base fluid. Also, The Nusselt number, pressure drop, friction factor, and pumping power increased by enhancement of the hot fluid temperature and volume flow rate of cold fluid. These parameters of nanofluid at 23.4 l/min and 55 ̊C compared to base fluid increased by 94.45%, 11.25%, 12.87%, and 11.36%, respectively. This study shows better performance at high temperatures compared to similar studies.

Condensation heat transfer of superheated vapour of R1234ze(E) and R134a inside a brazed plate heat exchanger

The recent restrictions on the use of refrigerants with high Global Warming Potential (GWP) have pushed the research to consider alternative solutions, such as the HydroFluoroOlefins, as possible replacements. Even though they are generally mildly flammable, their GWP is significantly lower compared to those of the HydroFluoroCarbons. This paper presents experimental measurements of R1234ze(E) and R134a heat transfer coefficients during condensation inside a brazed plate heat exchanger. Experimental tests during condensation heat transfer have been conducted considering different degrees of superheating, subcooling and outlet vapour quality. The condensation temperature varies between 34.6 °C and 42.3 °C and the refrigerant mass flux is between 9 kg m−2 s−1 and 49 kg m−2 s−1. The results showed that the heat transfer coefficients measured with R134a are between 4% and 8% higher than those of R1234ze(E). Complete condensation experiments showed that an increase in the liquid subcooling degree significantly reduces the thermal performance at low refrigerant mass velocities. In some cases, the plate area occupied by liquid refrigerant reached almost 30% of the overall heat transfer area, thus decreasing by 2.7 times the average heat transfer coefficient when passing from 3 K to 8 K subcooling degree. A comparison with the predictions of some empirical models is also presented to assess which one can better predict the experimental data.

Experimental comparison on energy consumption and heat transfer performance of corrugated H-type and L-type brazed plate heat exchangers

Global energy agencies and commissions highlight the importance of energy efficient and high performance systems to maintain a sustainable environment. At this point, brazed plate heat exchangers provide enhanced thermal performance with design compactness and reduce high energy consumption caused by the pumping power. This experimental work uncovers the thermal and hydraulic performance of the corrugated H-type and L-type brazed plate heat exchangers. The selected heat exchanger systems satisfy two main criteria: identical total heat transfer surface area and total volume of fluid within the systems. The experiments are conducted between 50 L/h and 200 L/h flow rates, and the temperature levels vary in a range of 10 °C to 50 °C. The uncertainty analysis for the experimental equipment and components have been documented. Furthermore, the experiments have been repeated three-times to eliminate the measurement errors and discrepancies. The findings indicate that heat transfer rate experienced by the H-type BPHE is higher than the L-type topology for the entire volumetric flow rates, and heat transfer enhancement reaches up to 7.4%. In contrary to the thermal performance, the L-type brazed plate heat exchanger yields lower energy consumption than the H-type system (except 50 L/h flow rate). The experimental findings show that total energy consumption between 100 L/h and 200 L/h flow rates decreases up to 10.5% via the L-type corrugated topology.

Detailed Thermal Evaluation of Brazed Plate Heat Exchanger Using Infrared Thermography

AbstractInfrared thermography of brazed plate heat exchangers for evaporators and condensers recently was used to quantify maldistribution. With the knowledge of the secondary fluids heat transfer coefficient and a given secondary fluids distribution, the local heat transfer coefficient of the primary fluid (refrigerant) and its distribution to the channels can be calculated. A sensitivity analysis shows ± 10 % difference of the surface temperature to the wall center temperature at the expected ratios of heat transfer coefficients. The method is presented in this paper using an exemplary infrared picture.

Experimental investigation on heat transfer and pressure drop of brazed plate heat exchanger using LiBr solution

To improve the performance and miniaturization of the absorption system, it is required to use a plate heat exchanger as a solution heat exchanger and to predict its performance accurately. In this study, the thermal performance of solution heat exchangers was investigated under operating conditions of the solution heat exchanger in the double-effect absorption system and new correlations of Nu and Fanning friction factor were developed and compared. As a result, the hot-side Nu of the high-temperature solution heat exchanger was 6.3–23.1, which was higher than that of the low-temperature solution heat exchanger (4.8–20.1). The thermal properties of the LiBr solution depending on the temperature were significantly sensitive. The developed Nu correlation (Nu = 0.273Re0.693Pr1/3) had a high accuracy with experimental results. In addition, the Fanning friction factor correlation was proposed as f = 1.601/Re0.123. The developed Fanning friction factor was lower than in other literature because the Fanning friction factor was affected by geometry parameters (chevron angle, pitch, height, and size).

Simulation and Optimization of the Fluid Solidification Process in Brazed Plate Heat Exchangers

Simulation and Optimization of the Fluid Solidification Process in Brazed Plate Heat Exchangers

Effect of single-phase flow maldistribution on the thermal performance of brazed plate heat exchangers

This paper presents an experimental and numerical investigation of the effect of single-phase flow maldistribution on the thermal performance of brazed plate heat exchangers (BPHEs). A thermal performance model of the BPHEs is developed with the consideration of flow maldistribution among the channels. The proposed model is validated against the experimental results. The model simulations reveal that the flow maldistribution has a trivial impact on the overall thermal capacity of the BPHEs if two fluid streams are supplied from the same side of the heat exchangers; if two fluid streams are supplied from the opposite side, the overall thermal performance is significantly deteriorated due to mismatched flow distributions of two fluid streams. Moreover, other factors are also proven to act in this issue, including the number of plates, plate length, header/port size, sudden expansion flow at the heat exchanger entrance, and heat capacity rate ratio of two streams. They either directly change the flow distribution or potentially affect the thermal effectiveness of the BPHEs. Based on the simulation results, correlations are generated, which can evaluate the thermal capacity degradation due to flow maldistribution without the necessity of knowing the detailed flow distribution and building heat exchanger models.