Countercurrent Exchange Research Articles

Effect of air bubble injection on the thermal performance of a vertical helical coiled tube heat exchanger: an experimental study

This study investigates the effect of air bubble injection on the thermal performance of a vertical counter-current coiled tube heat exchanger. A cylindrical PVC shell (height: 500 mm, diameter: 152.4 mm) was constructed to carry a copper coil with 11 regular turns and covered approximately 76% and 75% of the total shell height and diameter, respectively. The key operational parameters involving the shell side flow rate (2–10 L/min), the coil side flow rate (1–2 L/min), the air flow rate (0–10 L/min) and the temperature difference between the hot and cold fluids ((20 °C, 30 °C and 36 °C) were tested to determine the overall heat transfer coefficient (U). Air was injected into the shell side of the heat exchanger as bubbles with an average diameter of approximately 100 μm via a porous sparger. The results showed that air injection significantly enhanced U, with the highest improvement (158%) occurring at an air flow rate of 6 L/min, while the minimum improvement was 34%. Furthermore, the ratio of the overall heat transfer coefficient with air injection to that without air injection had its maximum value at a shell side flow rate of 6 L/min.

Model Predictive Control (MPC) of a Countercurrent Flow Plate Heat Exchanger in a Virtual Environment.

This research proposes advanced model-based control strategies for a countercurrent flow plate heat exchanger in a virtual environment. A virtual environment with visual and auditory effects is designed, which requires a mathematical model describing the real dynamics of the process; this allows parallel fluid movement in different directions with hot and cold temperatures at the outlet, incorporating control monitoring interfaces as communication links between the virtual heat exchanger and control applications. A multivariable and non-linear process like the plate and countercurrent flow heat exchanger requires analysis in the controller design; therefore, this work proposes and compares two control strategies to identify the best-performing one. The first controller is based on the inverse model of the plant, with linear algebra techniques and numerical methods; the second controller is a model predictive control (MPC), which presents optimal control actions that minimize the steady-state errors and aggressive variations in the actuators, respecting the temperature constraints and the operating limits, incorporating a predictive model of the plant. The controllers are tested for different setpoint changes and disturbances, determining that they are not overshot and that the MPC controller has the shortest settling time and lowest steady-state error.

Analysis of nanofluid and nano-enhanced phase change material (NEPCM) in a heat exchanger for thermal management of electronic devices

Thermal management of high-power electronic devices is essential to control their enormous heat generation, which is usually the cause of their damage. Scientists have found several solutions for cooling electronic devices, but a counter-current heat exchanger has never been used. In the same context, numerical research on the thermal performance of a proposed new cooling system based on a counterflow heat exchanger combined with a heat sink is conducted in this article. Cu-H2O nanofluid, n-Docosane nano-enhanced phase change material, and water were selected as coolants, and they are compared in terms of temperatures, Nusselt number, heat transfer coefficient, pressure drop, friction factor, and performance enhancement coefficient using a two-phase mixture transient model based on Finite Volume method. Two cases of the proposed system are studied to find the optimal distance between heat exchanger pipes and the hot surface. Results are compared with previous experimental data to demonstrate that the system under study is accurate. They revealed that integrating the heat exchanger with the heat sink using Cu-H2O nf as a coolant maintained the hot surface temperature below 308 K with improved heat transfer by 31.22% compared to water. 0.25 mm is the optimum distance to find the highest thermal performance of the cooling system.

Abstract WP311: Novel Computational Framework for Modelling the Effects of Temperature on Survival Time in Ischemic Stroke

Introduction: The detrimental influence of cerebral hyperthermia is well known, with notably deleterious effects in the ischemic brain, where even mild increases (<1°C) may rapidly potentiate ischemic injury. Experimental models of ischemic hyperthermia are undermined by the lack of pragmatic means for temporally- and spatially-resolved, direct cerebral thermometry. Computational models of cerebrovascular ischemia are well-suited to such exploration, and the use of digital phantoms for sophisticated biophysical modeling has been facilitated by emergent hardware, software, and computational solutions. We present a realistic computational environment for the simulation of thermal disturbance in cerebrovascular ischemia, permitting multiscale demonstration of hemodynamic, metabolic, and thermal aberrations in ischemic brain Methods: A multi-tissue biophysical numerical model of the human head and brain was extended to incorporate the dynamics of nutritive flow, metabolic need, tissue heating, and cytotoxicity. By restricting perfusion in a region of brain using a rudimentary representation of vascularization, we could quantify tissue heating arising from impaired radiative cooling, and time-dependent cell death. The procedure was iterated with an expected proportionality between temperature and metabolic rate Results: Fig 1 demonstrates simulated hypoperfusion affecting one hemisphere with resultant cerebral hyperthermia arising from impaired countercurrent heat exchange. Incorporating the effects of hyperthermia upon metabolic demand, the downward influence of heating on survivability is apparent, with ~30-minute acceleration to cytotoxicity. Conclusion: We present a combined model for tissue physiology and survival time following ischemic stroke using a multi-tissue model of whole-head bio-thermodynamics to examine effects of critical temperature disturbance on predicted tissue survival time.

Experimental and numerical investigation of heat transfer and flow of water-based graphene oxide nanofluid in a double pipe heat exchanger using different artificial neural network models

In this study, a water-based graphene oxide nanofluid was utilized in a counter-current flow double pipe heat exchanger (DPHE). The inner pipe carried the hot fluid (deionized water-based fluid). In the outer pipe, the cold fluid was flown, in which the experiments were performed once for deionized water-based fluid and once for graphene oxide nanofluid. These experiments were conducted at various inlet hot fluid temperatures of 35, 45, and 55 °C, volumetric concentrations of 0.01, 0.055, and 0.1% for nanofluid, and cold fluid flow rates of 14.4, 18.9, and 23.4 ml/s to evaluate the thermohydraulics of the DPHE. The results demonstrated that an increase in the flow rate and concentration of nanoparticles led to an improvement in the heat transfer coefficient (HTC) . It is also observed that inlet hot fluid temperature had a negligible effect on this coefficient compared to the concentration and flow rate. Additionally, the results showed that the friction factor and pressure drop of nanofluid were higher than those of the basefluid and their values were increased by increasing the concentration. The maximum increase compared to the basefluid was 72% for the friction factor and 111%, for the pressure drop. Besides, radial basis function neural network (RBFNN) and multi-layer perceptron neural network (MLPNN) models were designed for estimating the HTC. Both models accurately predicted the coefficient, but the RBFNN model exhibited higher accuracy than the MLPNN model. The results further indicated that the nanofluid outperformed the basefluid in terms of HTC. Due to the exceptionally high thermal conductivity of graphene nanoparticles, the HTC of the nanofluid was improved by up to 85% compared to the basefluid. The optimum value of HTC was achieved at a temperature of 55 °C, a volume concentration of 0.1%, and a flow rate of 23.4 ml/s.

Gill function in an early arthropod and the widespread adoption of the countercurrent exchange mechanism.

Rising but fluctuating oxygen levels in the Early Palaeozoic provide an environmental context for the radiation of early metazoans, but little is known about how mechanistically early animals satisfied their oxygen requirements. Here we propose that the countercurrent gaseous exchange, a highly efficient respiratory mechanism, was effective in the gills of the Late Ordovician trilobite Triarthrus eatoni. In order to test this, we use computational fluid dynamics to simulate water flow around its gills and show that water velocity decreased distinctly in front of and between the swollen ends, which first encountered the oxygen-charged water, and slowed continuously at the mid-central region, forming a buffer zone with a slight increase of the water volume. In T. eatoni respiratory surface area was maximized by extending filament height and gill shaft length. In comparison with the oxygen capacity of modern fish and crustaceans, a relatively low weight specific area in T. eatoni may indicate its low oxygen uptake, possibly related to a less active life mode. Exceptionally preserved respiratory structures in the Cambrian deuterostome Haikouella are also consistent with a model of countercurrent gaseous exchange, exemplifying the wide adoption of this strategy among early animals.

Nasal turbinates of the dicynodont Kawingasaurus fossilis and the possible impact of the fossorial habitat on the evolution of endothermy.

The nasal region of the fossorial anomodont Kawingasaurus fossilis was virtually reconstructed from neutron-computed tomographic data and compared with the terrestrial species Pristerodon mackayi and other nonmammalian synapsids. The tomography of the Kawingasaurus skull reveals a pattern of maxillo-, naso-, fronto- and ethmoturbinal ridges that strongly resemble the mammalian condition. On both sides of the nasal cavity, remains of scrolled maxilloturbinals were preserved that were still partially articulated with maxilloturbinal ridges. Furthermore, possible remains of the lamina semicircularis as well as fronto- or ethmoturbinals were found. In Kawingasaurus, the maxilloturbinal ridges were longer and stronger than in Pristerodon. Except for the nasoturbinal ridges, no other ridges in the olfactory region and no remains of turbinates were recognized. This supports the hypothesis that naso-, fronto-, ethmo- and maxilloturbinals were a plesiomorphic feature of synapsids, but due to their cartilaginous nature in most taxa were, in almost all cases, not preserved. The well-developed maxilloturbinals in Kawingasaurus were probably an adaptation to hypoxia-induced hyperventilation in the fossorial habitat, maintaining the high oxygen demands of Kawingasaurus' large brain. The surface area of the respiratory turbinates in Kawingasaurus falls into the mammalian range, which suggests that they functioned as a countercurrent exchange system for thermoregulation and conditioning of the respiratory airflow. Our results suggest that the environmental conditions of the fossorial habitat led to specific sensory adaptations, accompanied by a pulse in brain evolution and of endothermy in cistecephalids, ~50 million years before the origin of endothermy in the mammalian stem line. This supports the Nocturnal Bottleneck Theory, in that we found evidence for a similar evolutionary scenario in cistecephalids as proposed for early mammals.

Economic aspects of hydrodynamic extraction in the production of extracts from sprouted grain of cereals

Introduction. This study delves into the creation of functional beverages via nutrient extraction from sprouted grain raw materials, focusing on the extraction of biologically active compounds. The significance of the extraction method on the efficacy of bioactive compound extraction is a pivotal scientific fact, with hydrodynamic extraction previously studied under high-frequency currents. This research explores hydrodynamic extraction of sprouted grains of cereal crops using an experimental setup. Materials and Methods. The study utilized hydrodynamic extraction, a prevalent method encompassing infusion, mixing, filtering (with or without filtration) through membranes, and counter-current mass exchange between raw materials and extractants. Hydrodynamic extraction was chosen for its ability to intensify the process, reduce extraction time, increase the yield of extracted substances, and lower energy consumption. The experiment determined the extract yield from sprouted grains of cereal crops using this method. A rotatable second-order plan (Box plan) was employed for regression equation development, incorporating over 20 experiments and 10 equation coefficients. Results. The experiments established two factors influencing the extraction process’s effectiveness: extraction duration (t, min) and sprouted grain concentration (C, %). These factors impacted the optimization criteria - extract yield. The research outcomes are presented in detailed tables and diagrams, providing a comprehensive understanding of the process dynamics and optimization for maximum extract yield from various grains. Scientific Novelty. The study introduces a new perspective in the field of hydrodynamic extraction, emphasizing the impact of specific variables like extraction time and grain concentration on the yield and quality of extracts from sprouted cereal grains. The mathematical processing of data and the regression equations formulated offer a novel approach to understanding and optimizing the hydrodynamic extraction process. Practical Significance. The research findings are crucial for the economic sector, particularly in the production of functional beverages. Understanding the variables that influence the extraction process can lead to more efficient production methods, enhancing the quality and nutritional value of the beverages. The cost analysis has been undertaken and economic effect of proposed variants of production were calculated and compared. The study’s insights into the biochemical composition of extracts, especially from sprouted triticale, reveal their potential as valuable ingredients in the beverage industry, enriched with polyphenols, flavonoids, organic acids, and vitamins. This knowledge can guide economic strategies in functional beverage production, emphasizing cost-effectiveness and resource optimization.

A modified ε-NTU analytical model for the investigation of counter-flow Maisotsenko-based cooling systems

In this work the ε-NTU method has been adapted for the application of a countercurrent evaporative heat exchanger featuring a complex heat transfer surface. The study highlights some challenges related to extending analytical models that were validated on simple geometries and proposes the calibration of the ε-NTU method by experimentally measuring the overall heat transfer coefficient (UA) of the heat exchanger. Through a laboratory prototype of the M-cycle, two different operating conditions were investigated (mild and hot-dry climates) which reported almost constant UA values of 14.8 W/K and 16.1 W/K respectively. The obtained results from the model prediction were compared with the experimental data obtaining average errors on the outlet temperatures and on the cooling capacity lower than 1.5% in the case of simulation of hot and dry climate. The positive results allowed to extend the calculation to operating conditions not tested experimentally, highlighting how it is necessary to have NTU over 2–2.5, while the recirculation rate must be kept below 0.4 to make efficient use of the water. The aim is to support the implementation of the technology in full-scale applications, where the M-cycle is used alone or to complement a vapor compression system.

Aortic branches and rete mirabile of the limbs of two-toed sloth (Choloepus didactylus).

Choloepus didactylus has reduced metabolism and difficulty in thermoregulation owing to its low body mass, and there are few studies related to the vascularization of abdominal and thoracic organs in this species. Therefore, we macroscopically described the arteries that comprise the aortic arch, thoracic aorta, and abdominal aorta. Six specimens were used, and their arterial systems filled with red latex before fixation in 10% formaldehyde, and fragments of the rete mirabile were processed for histological analysis using light and scanning electron microscopy. In these species, the aortic arch had two branches: the brachiocephalic trunk and left subclavian artery. The initial portion of the abdominal aorta presented four different ramifications, besides to the peculiarities of the adrenal, renal, and iliac arteries. Microscopy of the rete mirabile revealed a muscular artery surrounded by smaller muscular arteries, veins, nerves, and lymphatic tissue joined by connective tissue. Thus, the data obtained have clinical and surgical importance, with applicability in procedures involving vascularization of the thoracic and abdominal organs. We suggest that the rete mirabile is an efficient thermoregulatory structure because it allows the accumulation of blood and the countercurrent heat exchange, as there is no blood mixing.

Directly irradiated fluidized bed autothermal reactor (DIFBAR): Hydrodynamics, thermal behaviour and preliminary reactive tests

The advancements of the Concentrating Solar Thermal (CST) technologies in the heat and power sector are pushing researchers to find new ways to exploit solar energy. Solar-driven thermochemical processes can open new scenarios and set a milestone towards a greener industry. This paper presents the development of a Directly Irradiated Fluidized Bed Autothermal Reactor (DIFBAR), that exploits fluidization technology and the principle of an autothermal reactor to carry out solar chemical processes with high efficiency. The viability of recovering the sensible energy of the solid products to preheat the reactants is studied in an experimental prototype that couples a cavity receiver/reactor and a countercurrent double-pipe heat exchanger. The prototype is operated as a circulating fluidized bed: the inner tube of the heat exchanger is a fluidized bed riser, the receiver works as a gas–solid separator, the outer tube (annulus) of the heat exchanger is an overflow standpipe and a buffer tank (reservoir) connects the annulus to the riser, closing the loop. The reservoir can also be operated as a fluidized bed reactor like in a dual-fluidized bed system. The first experimental results are reported using a Geldart B sand as bed inventory. A hydrodynamic study has been carried out to verify proper control of the system. Solid circulation rates have been determined and match the design target of 1.4 g/s. Pressure measurements have been used to control bed levels and the flow of the sand through the standpipe. The effects of gas velocities and outlet pressure drops are reported. Internal gas flow patterns have been determined by a gas tracing technique. Undesired gas by-passing streams are very small and can be zeroed by regulating the operating conditions. High temperature experiments have been conducted with a high-flux solar simulator under inert and reactive conditions, to prove the operating principle of the reactor. Steady state temperature profiles have been analyzed to assess the performance of the heat exchanger: the heat transfer coefficient ranges between 340 and 490 W/(m2 K). The operability of a solar-driven chemical process has been proved by calcining a batch of magnesium carbonate (MgCO3) particles, added to the inventory.

Sodium Magnetic Resonance Imaging Shows Impairment of the Counter-current Multiplication System in Diabetic Mice Kidney.

Sodium magnetic resonance imaging can non-invasively assess sodium distribution, specifically sodium concentration in the countercurrent multiplication system in the kidney, which forms a sodium concentration gradient from the cortex to the medulla, enabling efficient water reabsorption. This study aimed to investigate whether sodium magnetic resonance imaging can detect changes in sodium concentrations under normal conditions in mice and in disease models such as a mouse model with diabetes mellitus. Methods: We performed sodium and proton nuclear magnetic resonance imaging using a 9.4-T vertical standard-bore super-conducting magnet. Results: A condition of deep anesthesia, with widened breath intervals, or furosemide administration in 6-week-old C57BL/6JJcl mice showed a decrease in both tissue sodium concentrations in the medulla and sodium concentration gradients from the cortex to the medulla. Further, sodium magnetic resonance imaging revealed reductions in the sodium concentration of the medulla and in the gradient from the cortex to the medulla in BKS.Cg-Leprdb+/+ Leprdb/Jcl mice at very early type-2 diabetes mellitus stages compared to corresponding control BKS.Cg-m+/m+/Jcl mice. Conclusions: The kidneys of BKS.Cg-Leprdb+/+ Leprdb/Jcl mice aged 6 weeks showed impairments in the countercurrent multiplication system. We propose the utility of 23Na MRI for evaluating functional changes in diabetic kidney disease, not as markers that reflect structural damage. Thus, 23Na MRI may be a potential very early marker for structures beyond the glomerulus; this may prompt intervention with novel efficacious tubule-targeting therapies.

Computer Modelling of Non-Stationary Flows with Phase Transitions in Countercurrent Heat Exchangers

Computer Modelling of Non-Stationary Flows with Phase Transitions in Countercurrent Heat Exchangers

History of the iron furnace using the physical-chemical blast furnace model

The physical–chemical blast furnace model first built by Michard and Rist has proven to be a very efficient tool to predict and drive the present blast furnaces. It mostly describes the iron blast furnace as a counter current gas-solids dual heat and oxygen exchanger. The onset of coke gasification (orelse of iron oxide direct reduction), leads to a two-zones exchange model. This theory is used to look back at the operation of the earlier and smaller iron furnaces such as the early XIXth century charcoal blast furnace or the much older low shaft furnaces. It shows the interest of using physical-chemical models to better understand the operation of past production tools.

Prospective Randomized Controlled Trial Comparing Laparoscopic Palomo Surgery versus Scrotal Antegrade Sclerotherapy in Adolescent Varicocele.

Varicocele is a common condition in adolescence and the most common correctable cause of infertility. This study aimed to analyze and compare the outcomes of scrotal antegrade sclerotherapy (SAS) and laparoscopic Palomo surgery (LPS) in a tertiary referral centre. Patients with left grade 3 varicocele indicated for surgery were prospectively enrolled and randomly allocated to the SAS and LPS groups, with their respective contralateral normal testes taken as controls. The primary outcome measures were clinical varicocele recurrence, testicular catch-up growth, and post-operative hydrocele. All patients were evaluated clinically and using Doppler ultrasound by radiologists. From 2015 to 2020, 113 patients completed the study and were statistically analyzed (SAS, n = 57; LPS, n = 56). All patients had significantly smaller testes pre-operatively that the testicular volume differences with control testes were -23% in SAS and -19% in LPS. At 12-month follow-up, there were no statistical significant difference in clinical recurrences between the 2 groups (SAS = 5.3% vs LPS = 5.4%, P>.05, non-inferiority test). Testicular catch-up growths were observed in both groups, the mean testicular volume difference between the treatment and control testes reduced from -23% to -8.1% in SAS (P<.001) and -19% to -9.3% in LPS (P<.001) at 12-month follow-up. There was no post-operative hydrocele in SAS compared to 7 in LPS (0% vs 13%, P = .006). Both SAS and LPS are safe and effective procedures for treatment of adolescent varicocele with significant positive effect on testicular catch-up growth. SAS is not inferior to LPS in terms of clinical recurrence rate and with significantly less post-operative hydrocele.

Analysis of human thermoregulatory mechanisms using 2-D computational model

A numerical investigation is reported comparing various human thermoregulation mechanisms under hot and cold stress. The passive system of the developed model consists of 12 spherical/cylindrical segments and is modeled using the Pennes bioheat equation and finite difference method. The active system accounts for all regulatory responses, including the counter current heat exchange between veins and arteries; the respiratory heat loss; and threshold, gain, and maximum intensity of response mechanisms. The developed code analyzes various thermoregulatory defense mechanisms under hot and cold environments. Results indicate that shivering and sweating are more effective than other defense mechanisms under cold and hot conditions, respectively. Suppressing shivering will be more effective than the stoppage of vasoconstriction for inducing therapeutic hypothermia. The normal basal metabolic heat generation is essential to maintain a constant body temperature. It is seen that the changes in threshold temperatures of thermoregulatory mechanisms significantly affect the core more than the peripheral regions. The result may be helpful for better management of therapeutic hypothermia, hot/cold stress management, and design of drug protocols.

Thermodynamic Characteristics Study with Pyrolysis Steam Coupled Multi-Stage Condensers

A four-stage condensers in series system was adopted to solve the problems of insufficient condensation of high-temperature pyrolysis steam and difficulty in the classification and recovery of pyrolysis oil, where the internal fluids conducted countercurrent convection heat exchange. A steady-state physical and mathematical model of a single condenser was established to clarify the discipline of heat transfer between the internal fluids. Meanwhile, the model of pyrolysis steam coupled multi-stage condensers was proposed with the help of the model compound firstly. A numerical simulation was carried out and the results showed that when the number of condensers in series was four, the heat transfer process of the system reached saturation, and the heat exchange of the cold and hot fluids was completely realized, and it was of little significance to continue to connect more condensers in series for the condensation of pyrolysis steam. To quickly condense the hot fluid, the key was to increase the mass flow rate of the cold fluid in the first-stage condenser. Compared with the experimental values, the calculated values of hot fluid outlet temperature were not higher than 10%, indicating that the model was highly reliable.

The Method for Optimization of a Countercurrent Recuperative Heat Exchanger for a Cryogenic System Used in Superconducting Transport Power Plants

The Method for Optimization of a Countercurrent Recuperative Heat Exchanger for a Cryogenic System Used in Superconducting Transport Power Plants

Novel feedwater preheating system for parabolic trough solar power plant

Several improvements in the referenced parabolic trough power plant (PTPP) model (Andasol II) have been implemented by APROS software. The main advantage of this novel feedwater preheating system is to improve electricity production and evening operation hours at a low cost for modifying an existing PTPP in Spain. This in turn leads to less dependence on fossil fuels during the evening and cloudy periods. The reference model is improved by an increase in the collector loops in the reference solar field (SF) model to 208 loops rather than 156 loops to increase the absorbed thermal power, increasing the capacity of the thermal storage system (TSS) from 1017 MWth h to 1,360 MWth h to improve the night operating period, replacing the Feedwater/Steam circuit with a Feedwater/HTF circuit using five shell and tube counter-current heat exchangers that are used instead of condenser heat exchangers. The HTF enters the fifth low-pressure preheater with 128 kg/s and 393 °C in the daytime and 377 °C at night. The main advantage of this improvement is to use the entire generated steam within the steam turbine and not to heat the feedwater in the feedwater circuit. In addition, the control circuits are modified and added new controllers with new limitations for controlling the new operating conditions. This development is the first attempt in the field of research to use a Feedwater/HTF circuit in the PTPP in order to enhance performance. This improvement (optimization 1) in turn leads to a raise in the total HTF mass flow and the quantity of stored molten salt, as well as increasing the mass flow of HTF to the power block (PB). According to optimization 1, no steam will be taken out of the HP and LP-turbine toward the feedwater circuit. Therefore, the feedwater fed through new preheaters is heated by thermal oil instead of steam extractions. The predictions obtained from this optimization are compared to the simulated results that were previously extracted from the reference model on clear and cloudy days for evaluation of the behaviour of the optimized PTPP. It should be mentioned here that it can be used the same turbine and generator in the actual power plant to achieve this increase in the performance of the power plant, according to the technical data of manufacturers. Finally, an economic study of the cost was conducted for referenced and the optimized PTPP depending on the levelized energy cost (LEC). The findings reveal that the levelized energy cost of the optimized PTPP with storage energy is about 10.5% lower than that of the referenced PTPP.

Microchannel counter-current heat exchanger analysis highlighting equitability of conventional heat transfer theory in both macro and micro domains

Some of the early experimental investigations on microchannel surfaces could not be explained using the macroscale heat transfer theory, creating doubts regarding its applicability. However, the data analysis in those studies has often been done neglecting performance deteriorating effects like axial heat conduction. The axial conduction effect is often overlooked in macroscale applications depending on the operating conditions. Nevertheless, recent studies have proved that the axial conduction effect becomes significantly dominant when the fluid free-flow area and solid cross-sectional area are comparable with the scaling down channel dimensions. Anticipating that the axial conduction effect overshadows the actual information of the microscale heat transfer characteristics, an approach taking care of the latter should be adopted. Kroeger’s analysis, an established macroscale method, has been used to analyze microchannels heat exchangers. The results are compared against those obtained from a three-dimensional conjugate computational model of a miniaturized exchanger. A good agreement between them indicates that the macro-scale exchanger analysis (including axial conduction) with the conventional correlations usually recommended for macro channels can also predict the thermal performance of the heat exchanger in the micro-realm. If axial conduction is neglected, performance deterioration in microscale heat exchanger effectiveness can be as high as 43%.