Counter-flow Heat Exchanger Research Articles

Evolutionary design of compact counterflow heat exchanger

Abstract This investigation includes a geometric optimization for a compact heat exchanger built from hexagonal channels with the rely of Constructal design. A three-dimensional numerical analysis based on the finite volume method (FVM) are conducted to identify hydrodynamic and thermal behaviors of the counterflow arrays. We considered several configurations for the inactive channel emerged from packing the hexagonal channels within the compact heat exchanger, considering the easier access for the heat from the hot fluid to the cold fluid. The hexagonal arrays considered for the CFD study is first assumed to be well insulated. The hot and cold fluids (water) flow with variable Reynolds numbers; 10, 100, 200 and 300. The results are presented in term of heat transfer effectiveness, thermal conductance, and the thermal-to-flow performances ratio. The CFD code was verified with an experiment work to assess the accuracy of the current numerical analysis. Triangular channels (β = 1) employed in the inactive region showed better performance for the counterflow hexagonal bundle. High pressure drop is associated with the trapezoidal shape especially with smaller hydraulic diameter (small cross-sectional area).

Numerical analysis of heat transfer of a nanofluid counter-flow heat exchanger

One of the most significant facts for every economy is energy, regardless of big or small. The need for energy does not expire however it increases day by day, and this brings along the renovation activities. The energy sector is the most effective sector, especially in the climate change problem we have encountered during the recent years. Increasing the thermal capability of heat exchangers in almost every area where there is heating and cooling is very significant in terms of energy efficiency and savings.The numerical analysis of water and nanofluids with water as base fluid in a double-pipe, counter-flow heat exchanger with corrugated tube inside was performed using computational fluid dynamics in this research. The results of a different study were validated by the mathematical method to be utilized in the study. The analyzes we have performed for the heat exchanger we have discussed, the thermal performances of nanofluids obtained with Al2O3, CuO, TiO2 nanoparticles, whose base liquid is water, were analyzed according to different Reynolds numbers, different volumetric concentrations, each other and water.Optimum values were determined by making comparisons of many parameters with each other. It was determined that the use of nanofluid improves heat transfer compared to water, the heat transfer increases based on the increasing nanoparticle volume fraction, the increase in the Reynolds number of the workflow decreases the heat transfer, the increase in the Reynolds number of the refrigerant increases the heat transfer and the highest heat transfer is obtained in the CuO-H2O nanofluid and in heat transfer, and a 23.6% improvement was observed.

Study on the influence of distributed Joule-Thomson effect on the performance of microchannel cryocooler

At present, the pros and cons of distributed Joule-Thomson (J-T) effect in throttling refrigeration systems have been controversial. In this paper, a microchannel J-T cryocooler is used as the prototype. The distributed J-T effect is produced by the friction loss in the throttling channel. The refrigeration performance of the cryocooler at 6.0 MPa is analyzed. Then, according to the dependence of the J-T coefficient on pressure and temperature, a fully distributed J-T effect microchannel is designed to replace the separate counterflow heat exchanger and throttling device on the high-pressure side. The characteristics are simulated and compared with the prototype. The results show that the refrigeration ability of the fully distributed J-T cryocooler is slightly inferior to that of the prototype under the same pressure drop, and excessively increasing or reducing the cross-sectional size of the channel is not conducive to cooling. However, the fully distributed J-T effect structure can effectively delay the occurrence of choked flow due to the low velocity of the fluid. Under 6.0 MPa inlet pressure, the limited mass-flow rate of fully distributed cryocooler is 7.51 g/s, and the lowest temperature can reach 147.7 K, which is significantly lower than 163.3 K that the prototype can reach in the choked state. In addition, this paper also explores the influence of distributed J-T effect on the low-pressure side, which is beneficial to precooling the high-pressure fluid more efficiently using a little distributed J-T effect. A proper part of the friction loss in the low-pressure channel helps improve the refrigeration ability. At 6.0 MPa inlet pressure, the best cooling effect is obtained when the pressure drops in the low-pressure channel account for 15.85 % of the total pressure drop.

Analisis Perpindahan Kalor Pada Double Pipe Heat Exchanger Beraliran Lawan Arah Menggunakan Sirip Trapesium Dengan Fluida Cair

<p><em>This study aims to analyze the counter flow performance of a double pipe heat exchanger using an experimental method with the influence of the flow rate of hot and cold substances. The results showed that the counter-flow double-pipe heat exchanger produced a total heat transfer coefficient of 69.229 W/m2</em><em>℃</em><em>. The double pipe heat exchanger produces Reynolds number of 82.17 and Nusselt number of 1.18 in hot fluids, while in cold fluids it produces Reynolds number of 4.528.42 and Nusselt number of 31.52. The double pipe heat exchanger has an effectiveness rate of 116.16%.</em></p>

Analysis study of nano fluids and longitudinal fins on the heat transfer in the counter flow double pipe heat exchanger

In this paper, the heat transfer enhancement in a counter-flow double pipe heat exchanger with longitudinal rectangular fins on the outer surface of the inner tube was numerically investigated by ANSYS 20.R1 software using CFD package and finite volume method. Hot water flows in the inner tube at 60℃ while cold water flows in the outer tube at 25℃. The flow is laminar with five mass flow rates from 0.012kg/s to 0.02kg/s) for hot side and from 0.01kg/s to 0.03kg/s for cold side. Two types of nanoparticles Al₂O₃ and SiO₂ have been added to produce nanofluids as heat transfer fluid in the external channel (cold fluid flow) with four different concentrations from 0.04% to 1%. Results showed, as the concentration of Nanofluids increased, the heat transfer rate also increased. At 1% concentration, the maximum heat transfer coefficient was belonged to Al₂O₃/water nanofluid by 22.3% enhancement in comparison with distilled water, while the SiO₂/water nanofluid has enhancement of 19% in heat transfer coefficient in comparison with the distilled water. Both nanofluids show higher pressure drop compared with distilled water where the SiO₂/water nanofluid gives a higher drop of (33.2%), while the Al₂O₃/water nanofluid has (32.1%) of the pressure drop.

Cryogenic performance of a compact high-effectiveness mesh-based counter-flow heat exchanger

Compact effective Counter Flow Heat EXchangers (CFHEX) are critical components of almost all thermodynamic cycles, e.g. cryocooler-based remote cooling circuits that can enable a large number of high technology cryogenic applications. It is essential for such applications that these CFHEXs match the overall performance of the system. This paper presents the test setup, experimental performance results and the analysis of a novel mesh-based CFHEX in the 50 K–290 K temperature and 1 bar–5 bar pressure ranges. The measurements are compared to the numerical predictions for a range of mass flow rates and fluid stream pressures. A maximum average effectiveness of 94.9 % (NTU = 18.6) is achieved with a combined pressure drop of only 15 mbar at nominal system operating conditions with helium gas. The static loss along the CFHEX is measured and analysed. The numerical model is correlated with the experimental findings and further improvements to the design are suggested. In addition, a new friction factor model is proposed for the woven mesh matrix. Global implications of the CFHEX performance on the remote cooling system are quantified and discussed.

High performance, microarchitected, compact heat exchanger enabled by 3D printing

• Microarchitected gyroid heat exchanger was realized via additive manufacturing. • Lightweight (∼240 kg/m 3 ) exchanger possesses a surface to volume ratio of 670 m 2 /m 3. • Exchanger shows an overall heat transfer coefficient of 120 – 160 W/m 2 K. • Exchanger exhibits a 55 % increase in exchanger effectiveness. Additive manufacturing has created a paradigm shift in materials design and innovation, providing avenues and opportunities for geometric design freedom and customizations. Here, we report a microarchitected gyroid lattice liquid–liquid compact heat exchanger realized via stereolithography additive manufacturing as a single ready-to-use unit. This lightweight (∼240 kg/m 3 ) compact heat exchanger (with conjoined headers), with an engineered porosity of 80% and a separating wall thickness of 300 μm, has a surface to volume ratio of 670 m 2 /m 3 . X-ray computed tomography imaging confirms a defect-free 3D printed heat exchanger. The thermo-hydraulic characteristics were experimentally measured using water as the working fluid. The measurements indicate that the heat exchanger evinces an overall heat transfer coefficient of 120 - 160 W / m 2 K for hot fluid Reynolds number Re h in the range of 10 - 40 . Additionally, finite element analysis was conducted to evaluate the thermo-hydraulic characteristics of the gyroid lattice heat exchanger. The experimental results show -a 55 % increase in exchanger effectiveness for the additively manufactured gyroid lattice heat exchanger in comparison to a thermodynamically equivalent, most-efficient, counter-flow heat exchanger at one tenth of its size. The superiority of our architected heat exchanger to extant work is also demonstrated.

Modelling and Analysis of Viscoelastic and Nanofluid Effects on the Heat Transfer Characteristics in a Double-Pipe Counter-Flow Heat Exchanger

This study computationally investigates the heat transfer characteristics in a double-pipe counter-flow heat-exchanger. A heated viscoelastic fluid occupies the inner core region, and the outer annulus is filled with a colder Newtonian-Fluid-Based Nanofluid (NFBN). A mathematical model is developed to study the conjugate heat transfer characteristics and heat exchange properties from the hot viscoelastic fluid to the colder NFBN. The mathematical modelling and formulation of the given problem comprises of a system of coupled nonlinear partial differential Equations (PDEs) governing the flow, heat transfer, and stress characteristics. The viscoelastic stress behaviour of the core fluid is modelled via the Giesekus constitutive equations. The mathematical complexity arising from the coupled system of transient and nonlinear PDEs makes them analytically intractable, and hence, a recourse to numerical and computational methodologies is unavoidable. A numerical methodology based on the finite volume methods (FVM) is employed. The FVM algorithms are computationally implemented on the OpenFOAM software platform. The dependence of the field variables, namely the velocity, temperature, pressure, and polymeric stresses on the embedded flow parameters, are explored in detail. In particular, the results illustrate that an increase in the nanoparticle volume-fraction, in the NFBN, leads to enhanced heat-exchange characteristics from the hot core fluid to the colder shell NFBN. Specifically, the results illustrate that the use of NFBN as the coolant fluid leads to enhanced cooling of the hot core-fluid as compared to using an ordinary (nanoparticle free) Newtonian coolant.

An inverter-driven heat pump with a multi-tubular tube-in-tube heat exchanger for domestic hot water supply

An inverter-driven heat pump prototype to supply domestic hot water (DHW) was built, within which a multi-tubular tube-in-tube counter-flow heat exchanger as condenser was installed including a desuperheater section and a condenser section. The heating coefficient of performance (COP) is reduced approximately 10% if the feed water temperature increases from 9 °C to 24 °C. When the inlet temperature of primary brine is 24 °C, the compressor frequency does not show any effect on the heating COP. While when the inlet temperatures of primary fluid are 5, 10, and 17 °C, the COP increases with the rise of the compressor frequency at first, but it stays almost constant when the compressor frequency is within 40–55 Hz. It is considered that the effects of opposite dependencies of heat transfer and the pressure drop in the condenser onto COP tend to cancel each other out to obtain a constant heating COP. When the produced hot water is 65 °C, the heating COP of our developed heat pump for DHW is the largest among those of other three different heat pumps.

Operator & Fractional Order Based Nonlinear Robust Control for a Spiral Counter-Flow Heat Exchanger with Uncertainties and Disturbances

This paper studies operator and fractional order nonlinear robust control for a spiral counter-flow heat exchanger with uncertainties and disturbances. First, preliminary concepts are presented concerning fractional order derivative and calculus, fractional order operator theory. Then, the problem statement about nonlinear fractional order derivative equation with uncertainties is described. Third, the design of an operator fractional order controller and fractional order PID controller and determination of several related parameters is described. Simulations were performed to verify tracking and anti-disturbance performance by comparison to different control cases; verification is described and concluding remarks provided.

Development of a silicon carbide ceramic based counter-flow heat exchanger by binder jetting and liquid silicon infiltration for concentrating solar power

A silicon carbide ceramic counter-flow heat exchanger with integrated headers was printed by binder jetting additive manufacturing process. Multiple phenolic binder infiltration cycles (3 or 5) followed by pyrolysis were conducted to increase the net carbon content of the printed SiC specimens. Subsequently, to attain full densification, silicon melt infiltration was used. The microstructure and mechanical properties were comprehensively characterized on the densified material. The chemical compositions and visual distribution of the various regions in the specimens were determined via scanning electron microscopy, while X-ray diffraction and synchrotron μ-computed tomography were used to provide a quantitative assessment of the volume fractions of the identified phase regions. Microhardness measurements showed dependence on the local microstructure. The fracture strength of the material was correlated with the specimen density and agreed with the reported values in the literature. High-temperature exposure at 750 °C for up to 200 h did not degrade the strength for the specimens with three phenolic-binder infiltrations; however, the strengths degraded for ones with five phenolic-binder infiltrations. The associated fracture toughnesses of the specimens were ∼3.4 MPam1/2 at room temperature and 750 °C, and the thermal conductivities varied from >150 W/mK at room temperature to ∼45 W/mK at 750 °C. Hence, this study validated the use of the binder-jetting printed SiC ceramic materials for high-temperature heat exchanges. Finally, we also present in this work the first successful fabrication of a binder-jetting printed one-piece dense SiC ceramic heat exchanger body with unblocked channels that can be used for the flow of heat transfer fluids.

Remote cooling systems with mesh-based heat exchangers for cryogenic applications

In the refrigeration technologies available for the 2 W - 5 W cooling power range at 4.5 K, innovative designs for intermediate cooling options are proposed between the large-scale cryogenic plants and small-scale commercially available cryocoolers. This paper presents a number of remote cooling solutions, which use high-effectiveness mesh-based counterflow heat exchangers (CFHEX) to support the aforementioned refrigeration domain. Additionally, the cooling power is aimed to be provided in a remote, distributed and non-disturbing manner (i.e. reduced mechanical vibrations and magnetic disturbances) for high-technology cryogenic applications that require very low background noise levels. The proposed remote cooling options are analysed in terms of their cooling power performance. Designs and sizing of individual system components, i.e. CFHEXs and cooling interface options, for superconducting radio frequency (SRF) cavity cooling application are also proposed. CFHEX compactness and influence of their individual effectiveness values on the performance of the remote cooling systems are assessed, and capillary cooling interface performance is analysed.

Design and analysis of the helium purification system for the NSRRC cryogenic system

Helium is an expensive consumable in cryogenic facilities and is used widely in space, medical and energy research. At NSRRC, liquid helium is used as a coolant for superconducting magnets and SRF cavities . Minor contaminants such as nitrogen, oxygen, moisture and oil will be picked up when liquid helium circulates in large scale cryogenic systems and such contaminants can crystalize and cause damage to the cold box turbo expanders resulting in system damage and failure . Therefore, a helium purification system is designed as an integral part of the cryogenic system to conserve helium by providing 99.9995% pure helium to the liquefier after eliminating contaminants. The NSRRC helium purification process is based on two principles, the first one being a cryo-sorption device using activated charcoal and a molecular sieve and the other being a cryo-condensation unit using a tubular heat exchanger. The purifier has been designed to purify impure helium with overestimated contaminants of as much as 2.5% nitrogen and 2.5% oxygen with a mass flow rate of 475 nm3/hr and delivering a pressure of 17 bar(a) of impure helium to the purifier, the actual impurity will be much lower than the actual design contaminants. In this paper, calculation and design of the helium purification system and components composed of one double pipe counter flow heat exchanger, one vessel and tube heat exchanger, one pre-cooler and one charcoal vessel will be discussed together with charcoal mass requirement calculations and design of other components. In NSRRC, helium is liquefied and is used as a coolant for the SRF system and for cryogenic undulators. During a cryogenic cycle in the cryogenic system, helium may pick up contaminants such as moisture, oxygen, oil, and nitrogen, which have a higher freezing point than liquid helium and will crystalize. These frozen impurities will then affect plant capacity and operation such as alternating flow characteristics, damaging moving parts like turbines in the cold box causing the overall cooling efficiency to drop. Eliminating the contaminants is therefore very important for the cryogenic system.

Particle-to-fluid direct-contact counter-flow heat exchanger: Simple-models validation and integration with a particle-based central tower system

This paper presents validation studies of two theoretical models of a direct-contact counter-flow particle-to-air heat exchanger. It also describes the integration of the proposed heat exchanger with a particle-based central tower system. Two basic models are analyzed: (1) the mixing model, which treats falling particles as an isolated particle falling downward in unbounded-atmospheric air, and (2) the simple-equilibrium model (SEM), which assumes that both the media reached thermal equilibrium in every segment along the exchanger. The mixing model predicted the outlet temperature quite accurately for the particles with 0.5 mm diameter. For CARBOEAD particles of 0.5 mm diameter, the predicted heat rate was within ±5% of the experimental results. The SEM overpredicted the outlet temperature regardless of particle size. A simple modification was added to the SEM, which led to improve the model predictions greatly. An integrated conceptual system design is also presented and discussed. The use of a double dump valve introduces many advantages towards a practical integrated system. Finally, employing particle strainers at the exchanger outlet is crucial to reduce/eliminate risks about the swept particles.

Analysis and design of an air to air heat exchanger used in energy recovery systems

With the continuous worldwide energy use increase, energy efficiency is gaining high importance. Consequently, many methods have been investigated for potential energy savings. One of these methods is the use of heat recovery systems. These systems basically re-use waste heat and reduce energy consumption. Also, they are increasingly used to reduce heating and cooling demands of buildings. Their main feature is to provide fresh air to the place which is heated by the exhaust air with the help of a heat exchanger (HEX) working between two different temperature sources. The most commonly used types of heat exchangers in ventilation systems are cross-flow and counter-flow heat exchangers. Cross-flow heat exchangers have a thermal efficiency in the range of 50-75% while counter-flow heat exchangers have 75-95%. Many studies have been carried out to increase the efficiency of this type of heat exchangers. In this study, different designs of cross-flow and counter-flow exchangers are compared using ANSYS Fluent software. The aim is to determine how the plate surface geometry affects heat transfer and pressure drop. It is aimed to find the optimum design with maximum efficiency, high heat transfer and low pressure drop for heat exchangers. As a result, it has been observed that thermal efficiency increased from 18% to 60% when changing from cross flow to counter flow in flat plate design, while it increased from 25% to 77% in enhanced plate designs. For enhanced designs, counter flow heat exchanger is 52% more efficient than cross flow heat exchanger. Also, improvements to increase the surface area and turbulence in both flow types have increased heat transfer and thermal efficiency.

The Effect of Heat Exchanger Design on Heat transfer Rate and Temperature Distribution

The heat exchanger (HE) is a device that is used to complete the process of heat transfer between different matters without direct mixing. Therefore, it is of great importance in the transfer of energy and the completion of various energy transition processes. In the processes of HE between different energy systems, many factors influence and play a major and important role in the efficiency of transformation and exchange in forms of energy, such as the length, the material type, the exchange fluid, the surrounding environment, and many other factors. In this work, the effect of the HE length of the parallel and counter flow HEs was investigated based on the use of computer simulation programs. There was a significant impact of the exchange factors, especially the length of the HEs in both the parallel and counter-flow HEs, on the quality and efficiency of the HE and the temperature distribution. The overall evaluation shows that by increasing the length of the HE for both parallel and counter-flow HEs, the heat transfer is increased and the heat distribution becomes more homogeneous, which aids in enhancing the transfer of energy efficiency inside the HEs. Doi: 10.28991/ESJ-2022-06-01-010 Full Text: PDF

Enhancement of Heat Transfer in a Concentric Tube Counter Flow Heat Exchanger using CuO Nanofluids

Engineers and Scientists have always tried to increase the rate of heat transfer. The most commonly used base fluids do not provide a very high rate of heat transfer. This research work aims to investigate the enhancement of heat transfer rate in a concentric type (double pipe) counter flow heat exchanger using CuO nanofluids at different volume concentrations (0.01%, 0.05% and 0.1%). The experiments conducted on nanofluids showed that, at 0.1% volume concentration of nanofluid at 2.5 LPM, the heat transfer rate, Reynolds’s number and effectiveness were increased by 16.25%, 15.52% and 2.88% respectively compared to base fluid without nano-particles. Hence it was concluded that, CuO nanofluid is having a great potential to be used as a better heat transfer fluid in heat exchangers.

Role of beryllium oxide on the thermal efficiency of microchannel heat exchanger with an optimum fin structure

High-efficiency microchannel heat exchangers (MHEs) can remarkably meet the thermal requirements in many areas of technology. Several active and passive techniques can improve the efficiency of heat exchangers; the improvement enables engineering processes to decrease operational costs through waste heat reduction. In the present article, two different passive techniques are applied to improve the heat transfer efficiency of a counter-flow heat exchanger. To do this, four various microchannels with airfoil fins, circular fins, trapezoidal fins, and triangular fins are designed. First, the temperature distribution and effectiveness for each microchannel are calculated and compared with each other. Results of the comparison showed that the optimum structure belongs to the microchannel with trapezoidal fins. Second, BeO ceramic is utilized as the microchannel heat exchanger's material. At a given mass flow rate of 30.5 kg/h, the superior thermal features of BeO lead to more uniform temperature distribution, and also it makes an improvement of 219% in the effectiveness of MHE with trapezoidal fins compared to alumina-made MHE with simple channels.

Numerical Investigation and Ann Based Prediction of the Heat Transfer Characteristics of the Use of Ring Turbulator in a Counterflow Heat Exchanger

Numerical Investigation and Ann Based Prediction of the Heat Transfer Characteristics of the Use of Ring Turbulator in a Counterflow Heat Exchanger

Experimental analysis of copper coated helical coiled tube heat exchanger using nanofluid and water

Many studies focused on improving heat transfer by increasing the electrical, industrial, and transportation processes that are required to achieve a higher heat transfer rate. In general, there are two types of heat transfer enhancement techniques: active and passive. External power inputs such as pulse flow, vibratory force, and a magnetic field are used in the active approach. The heat transfer rate is increased upto 20 % in the passive technique by adding more devices or changing the heat transfer surface. The nanoparticle suspension is a heat transfer improvement approach in this study. An experimental investigation used Al2O3-water nanofluid in the counter flow heat exchanger to improve heat transfer in the range of 20 %. Experiments with varied volume concentrations 0.1 and 0.15 and mass flow rates of nanofluid were carried out. The arrangements are utilized to assess the situation. The temperature fluctuations were measured using the setups and the acquired values are compared to prior nanofluid performance results, and the result demonstrates that the heat transfer rate has risen upto 20 %. It also shows that the Al2O3-water nanofluid performed better than water.