Heat Exchange Efficiency Research Articles

Heat transfer and flow characterisation of aircraft heat exchangers considering manufacturing constraints

Abstract With the progress and development of the times, the traditional aircraft power system and difficult to meet the needs of the current aviation development, for the aircraft power and heat exchanger research has been more and more extensive attention. This study takes the heat exchanger of the aircraft loop control system as an example, constructs the thermal management system of the aircraft according to the mechanism of its heat transfer and flow characteristics, and optimizes it under the consideration of manufacturing constraints. Based on the theory of fluid mechanics, the aircraft heat exchanger is simulated, and control equations based on heat transfer and flow characteristics are established. In this paper, the temperature difference of the heat exchanger is increased by 6.5°C and 5.4°C, respectively, and the heat transfer coefficient is between 11 and 14 kW/m²k. Furthermore, the fluid temperature has risen from 0.05 to 0.5 to 0.30 to 0.87 with the increase in flow rate. The maximum deviation values were 8.3%, 6.7%, and 8.6%, respectively, and the confidence intervals were all above 90%. This study can effectively improve the efficiency of aircraft heat exchangers compared to traditional heat exchangers and has more advantages in heat transfer performance, which provides a reference value for the development of the aviation field.

ANALYSIS OF THE SINGLE-BLOW TRANSIENT TESTING TECHNIQUE FOR NONMETALLIC HEAT EXCHANGERS

For measuring the efficiency of nonmetallic heat exchangers, a mathematical model was established based on the principle of the single-blow testing technique, in which the conductive thermal resistance across nonmetallic plates of the exchangers was taken into account. The analytical solution was obtained by means of the Laplace transformation and numerical inverse transform method. The accuracy of the model was verified by comparing it with the literature. The effect of the plate Bi number on the evaluated number of transfer units (NTU) was analyzed. Based on the single-blow transient testing technique and the present model, the heat transfer performance and frictional pressure drop of four types of nonmetallic plates with different structural parameters were experimentally studied. The correlations for heat transfer and frictional pressure drop of nonmetallic heat exchange structures are established.

Enhancing thermal efficiency of earth-air tunnel heat exchangers (EATHE) through response surface methodology

Enhancing thermal efficiency of earth-air tunnel heat exchangers (EATHE) through response surface methodology

INVESTIGATION OF ENERGY, EXERGY, AND EMISSION PERFORMANCE OF TURBULATORS INSERTS HEAT EXCHANGER WITH TERNARY HYBRID NANOFLUID COOLANT

The improvement of technologies necessitates using a meticulous heat dissipation method to enhance the exergy efficiency of small air heat exchangers. To improve thermal performance, plain tube (PT) heat exchangers (HX) use passive inserts, such as dimpled twisted turbulator inserts (DTTI) and twisted turbulator inserts (TTI) filled with a ternary hybrid nanofluid (THNF) based on water. Energy, exergy use, and environmental impacts in the future are the primary foci of the inquiry on THNF replacement inserts. Using water as the operating fluid, copper oxide (CuO), aluminum oxide (Al<sub>2</sub>O<sub>3</sub>), and titanium oxide (TiO<sub>2</sub>) nanoparticles are dissolved. The resultant THNF is injected at 0.06%, 0.09%, and 0.12%. Energy, exergy, and emissions are used to study certain features of control fluid flow. The results of the experiments show that using TTI and DTTI along with THNF makes a small air heat exchanger much more efficient at heating and cooling. When DTTI and TTI turbulator plugs are used in regular tubes with THNF of 0.12% (v/v) concentration, friction factor, heat transfer, reversibility, and exergy change all get much better. When DTTI or TTI turbulator plugs are put into the core of the tube, the carbon dioxide (CO<sub>2</sub>) release goes up by 2.6 to 2.1. People who use DTTI with THNF of 0.12% (v/v) concentration as the operating fluid and a tube plug will get performance evaluation criterion (PEC) numbers between 1.076 and 1.04. A careful study of friction factor, heat transfer, exergy efficiency increase, and environmental effect shows that DTTI is a superior passive device for enhancing heat transfer efficiency, particularly when combined with THNF of 0.12% (v/v) concentration.

Assessing the Thermal Efficiency of Horizontal Air-Ground Heat Exchangers for Heating and Cooling Buildings in the Northwestern Algeria Region

Assessing the Thermal Efficiency of Horizontal Air-Ground Heat Exchangers for Heating and Cooling Buildings in the Northwestern Algeria Region

Influencing law of key parameters on the thermal efficiency of single-well closed-loop heat exchanger

The single-well closed-loop heat extraction technology can realize efficient exploitation of mid-to-deep geothermal resources. A two-dimension heat transfer model is established. The effects of flow rate, inlet temperature, length and diameter of insulated tubing on heat extraction power and outlet temperature were investigated by the two-way absolute grey correlation analysis method. Results indicate that thermal power increases with the increase of displacement and length of insulated tubing, and decreases with the increase of injection temperature, outer diameter of insulated tubing and inner diameter of insulated tubing.

Analysis of influence of running time on heat transfer efficiency of buried tube heat exchanger under different working conditions

Analysis of influence of running time on heat transfer efficiency of buried tube heat exchanger under different working conditions

INVESTIGATIONS ON OPEN-CELL METAL FOAM–FITTED TUBES FOR HEAT TRANSFER ENHANCEMENT – A DISCUSSION ON ENHANCEMENT MECHANISMS

Metal foams are drawing increasing attention due to their high surface area-to-volume ratio, high thermal conductivity, and low density. Heat exchanger manufacturers are constantly looking for innovative methods toward building highly efficient and compact heat exchangers. To enhance heat transfer, the effective thermal conductivity, fitment of foam on pipe, influence of working fluids, and effect of the bonding method are major areas of investigation. This paper aims to present a review of various investigations conducted on open-cell metal foam for enhancing heat transfer. The pore size distribution of metal foam directly influences the effective thermal conductivity. Recent progress toward bimodal pore size distribution has been reviewed and discussed. There exists a tradeoff between enhancing heat transfer and the corresponding pressure drop. Different configurations of fitting metal foam on pipes, such as fully filled, partially filled, and tubes wrapped with metal foam, are critically reviewed, and their performance is compared. The working fluid and its conditions used with metal foam has tremendous potential toward enhancing heat transfer. The influence of nonrefrigerants, refrigerants, and nanofluids has been presented in this regard. Different bonding methods and their influence on thermal resistance are also reviewed. To date, there is hardly any literature that addresses the performance of metal foam–fitted tubes in condensers and evaporators for vapor compression refrigeration systems. Metal foam-fitted tubes have shown promising results in terms of heat transfer enhancement. The outcome of this review provides insights into further research on the use of metal foam–fitted tubes for refrigeration applications.

Investigation of the suppression effect of inert dust on the pressure characteristics of gas coal dust explosion

The suppression effect of inert powder on gas-induced suspension coal dust explosions was investigated using a semi-closed pipeline experimental platform. The shock wave overpressure propagation characteristics of gas explosions with different concentrations of mixed dust (calcium carbonate and coal dust) were measured and analyzed. The suppression mechanism of inert powder on the explosion process was also discussed. The results indicate that when the coal dust concentration is 200g/m?, the peak overpressure of the explosion decreases gradually with increasing inert powder concentration, and the peak overpressure ratio in the pipeline shows a decreasing-increasing trend; the acceleration of the explosion pressure reduces with increasing mixed dust concentration, and when high concentration of mixed dust is involved in the explosion, the acceleration of the explosion pressure is lower than that when only coal dust is involved; The inhibitory effect of calcium carbonate on dust explosion increased linearly with its concentration when the ratio of inert dust to coal dust was 1:2.; Inert powder mainly suppresses the explosive power by physical heat absorption and reducing heat exchange efficiency. The experimental results established the theoretical basis for inert dust suppressing coal dust participation in explosions, and have reference significance for formulating mine explosion suppression measures.

Performance analysis and effect of various material fin-perforations in a plate-finned heat exchanger

Finding increasingly efficient heat exchangers requires a critical task: the development of fin profiles for prolonged life of equipment. The present study uses numerical analysis for better plate-finned heat exchangers hydraulic and thermal performance. Fin patterns are used in the analysis to evaluate a four-tube in-line heat exchanger. The proposed approach involves use of simulation and numerical methods to solve the heat transfer problem on different materials and wind velocity data as boundary conditions for improved heat transfer. The Reynolds-Averaged Navier-Stokes (RANS) model will be used to correct the average turbulent air flow over finned tubes in three dimensions using the ANSYS-Fluent software. The evaluation plan compares the current findings with published Nusselt number empirical correlations for the justification. Finally, the presentation of a parametric study on the impact of fin perforation size and shape on different materials and the behaviour of fluid dynamics and heat transfer. Larger fin perforation sizes (circular, rectangle, rhombus, and ellipse shapes) are found to enhance the heat exchangers' overall PEC and thermal efficiency for sustainability of the thermal equipment. The comparison was made between non-perforated and perforated fin types. Ultimately, it was determined that the best option for plate fin heat exchangers is the circular type perforated fin. When compared to without perforated fins, the circular type perforated fin has a higher heat transfer coefficient. A circular perforated fin has high performance, and the rhombus type perforated fin has lower performance.

Intensification of Heat Transfer during Steam Condensation in Process Condenser of NPP Unit Cooling System

The paper investigates heat transfer during condensation of water vapor on vertical pipes of the process condenser of the cooling system of a nuclear power unit. The numerical study was performed at different mass flow rates of steam in the range of its change from 20 kg/s to 40 kg/s. Intensification of heat exchange is provided by the use of highly efficient heat exchange profiled tubes. The study used a set of heat exchange tubes (25 mm in diameter and 1.4 mm wall thickness) with the following values of the distance between the grooves of the profiled tube: 0.007075 m, 0.00875 m, 0.00925 m, 0.0105 m. The effect of the groove depth (from 0.0007 to 0.0009 m) on heat transfer during water vapor condensation on vertical pipes was also studied. The study was carried out for the range of changes in the Reynolds number for the condensate film from 5254.2 to 10508.5. The study obtained data indicating an increase in the heat transfer coefficient on the pipe with an intensifier compared to the heat transfer coefficient on a smooth pipe. This analysis did not take into account the change in tube wall temperature.

Accelerated Recombination of Lophyl Radicals in Micelles: Rapid Controlled Self-Assembly of Micelles Formed by Amphiphilic Lophine Dimers and Release of Solubilized Substance by Photoirradiation.

Controlling the morphology of molecular assemblies formed by surfactants by photoirradiation enables the controlled release of incorporated substances, which can be applied to delivery systems for drugs and active ingredients. On the other hand, conventional photoresponsive surfactants and molecular assemblies have a slow response speed, making it difficult to control their functions at the desired time. In this review, I discuss our recent progress in the accelerated control of functions of photoresponsive molecular assemblies by using lophine dimer as a photochromic compound. The lophine dimer derivative dissociates into a pair of lophyl radicals that upon ultraviolet (UV) light irradiation, and these radical species thermally recombine although the recombination reaction is extremely slow due to the diffusion of lophyl radicals. By using the confined inner space of micelles formed by surfactants, the recombination reaction was extremely accelerated. With UV light irradiation, rapid morphological changes in micelles, formed by amphiphilic lophine dimers were observed by using in situ small-angle neutron scattering (in situ SANS) system. Moreover, the rapid controlled release of calcein as a model drug was achieved by UV light irradiation using the photoresponsive micelles. This rapid system can realize the controlled release of drugs truly at the desired time, developing an efficient and precise drug delivery system (DDS). Furthermore, it can be applied in a wide range of fields such as release control of active ingredients, efficient heat exchange control, and actuating systems.

AN INNOVATIVE METHODOLOGY TO DESIGN GYROID HEAT EXCHANGERS FOR METAL ADDITIVE MANUFACTURING

This study demonstrates an innovative approach to the automatic design of compact gyroid heat exchangers using the advanced engineering software nTopology, which is based on implicit modeling technology. The aim is to provide a modern enhancement to traditional 'Shell and Tube' type heat exchangers. Utilizing functions in implicit modeling and parametric design features, complex internal gyroid structures can be used as an alternative heat transfer interface in 'Shell and Tube' type heat exchangers. The most striking aspect of the methodology is its ability to fully automate the design process. By consolidating specific parameters into a single function block and entering scalar values, a fast and flexible workflow is activated, automatically generating the final geometry. Gyroid structures with high thermal performance and fluid dynamics are automatically adapted for various volumes and geometries. These structures can improve the overall efficiency of heat exchangers and offer significant advantages, especially in specialized application areas such as aerospace and space industries. In the design and sizing process of the gyroid heat exchanger, if manufacturing is planned, it is necessary to pay attention to the design principles for metal additive manufacturing. In conclusion, this study demonstrates that the advanced engineering software known as nTopology can create a synergistic effect in the rapid and easy design of gyroid heat exchangers and in establishing the automation of the design process.

Разработка методологии создания энергоэффективных вентиляторов для аппаратов воздушного охлаждения

Introduction. Increasing the competitiveness of enterprises in the mining and oil and gas sectors of the Russian economy in combination with industrial safety requirements actualizes the task of developing a methodology for creating energy-efficient fans for air cooling devices with a dominant nature-like proportionality. Research methods and materials. The research method for creating adaptive fans is based on the scientific hypothesis of a nature-like proportionality in the aerodynamics of the profiles of the impeller blades. The results of the research. In the course of research, it was established that the most significant source of increasing the efficiency of AVO fan installations is an increase in the aerodynamic quality of the profiles of the blades of their impellers as the range of angles of attack increases. Discussion of research results. The use of modifications of conformal transformations with the proposed hypothesis of nature-like proportionality makes it possible to solve the problem of improving the aerodynamic quality of the blade profiles. Conclusions of the article. The creation of fans based on the principle of nature-like proportionality makes it possible to adequately and simultaneously with minimal energy costs ensure the necessary parameters of the cooling air and the stable efficiency of heat exchangers. Suggestions for practical application and direction of future research. The research results can be obtained when creating and modernizing a wide class of high-speed axial fans.

Mathematical analysis of Williamson nanofluid flow under radiation effects through slender cylinder

ABSTRACT Current research work demonstrates Williamson nanofluid flow through a slender cylinder. A slender cylinder has not been discussed before with Williamson nanofluid under thermal radiation effects, which is the novelty of the problem. The mass and heat transfer are analyzed under the different assumptions of viscosity, density, and thermal conductivity. Conservation of momentum and energy is modeled to exhibit the impact of the problem. Flow governing equations are initially transformed into ordinary differential equations and then demonstrated numerically by using MATLAB bvp4c. The significance of the present study is to understand how radiation interacts with Williamson’s fluid inside a slender cylinder, which is vital for optimizing heat transfer processes. This knowledge can be applied to design more efficient heat exchangers, boilers, and cooling systems in industries ranging from power generation to manufacturing. The effects of dimensionless numbers on the non-dimensional fields are investigated and shown graphically. The main findings are that the velocity curve reveals the decreasing behavior for curvature and buoyancy parameters. Radiation parameter and Prandtl number boost the temperature profile. The thermophoresis parameter decreases the concentration profile, while the Brownian parameter increases it. The heat transfer curve goes up, while skin friction and Sherwood number go down under the effects of different parameters.

Identifying regularities of fluid throttling of an inertial hydrodynamic installation

The article presents the results of experimental research conducted on a specially designed setup for pressurizing various types of fluids through throttle orifices. To determine the optimal operating mode of the thermal system, throttle nozzles of different diameters, specifically 1.5 mm, 2 mm, and 3 mm, were utilized. One of the primary advantages of vortex heaters is their high heat exchange efficiency. This is attributed to the vortical motions and turbulence generated within the device, which promote more vigorous fluid mixing, thus enhancing heat transfer efficiency. However, vortex heaters do have certain drawbacks. Vortical components may experience wear and require regular maintenance and replacement. Subsequently, during the course of experimental work, an alternative inertia-based hydrodynamic system for heating heat carriers was developed and installed in a laboratory experimental facility. The research focus was on technical water. The results indicated that the static pre-pressure generated by the supply of water from the water main into the system decreases as the rotor's angular velocity increases. Experimental investigations demonstrated that rotor rotation leads to a redistribution of flow characteristics in throttle orifices for both static and dynamic inertial fluid discharge. Given that any static column of liquid results in level flow through throttle orifices, their flow static parameters were established. Furthermore, the research revealed that with the increase in rotor angular velocity, the fluid pressure at the throttle orifices rises, while the share of fluid discharge from the initial static pressure decreases in the overall fluid flow

CFD Analysis of Refrigerator Integrated with Atmospheric Water Generator

This Research article discuss about the study of performance analysis. This system is a combination of refrigerator and Atmospheric Water Generator (AWG). The purpose behind integrating two devices is to get benefit of both products together, refrigerator will act as a domestic refrigerator plus the atmospheric water system will generate the fresh distilled water to drink. This system is designed to generate a water of 20 liters per day. Also, it is designed in such a way that, this AWG can attach with various capacity is the refrigerator. Performance evaluation of this system is done with the help of computational fluid dynamics. Fluent module is used in ANSYS software. Various levels of parameter are evaluated, variables considered in the study were Relative humidity, velocity of air in AWG heat exchanger, and temperature of air. The output parameters evaluated like water generation capacity of AWG, Coefficient of Performance (COP) of AWG and refrigerator and heat exchanger efficiency. The results of CFD shows positive results as per design. 24th case has given highest COP 1.26. General, range of COP lie between 1.127 to 1.260. COP of Standard Refrigerator remain between 1.437 to 1.593. Also, it means COP of other two cases are more. As far as COP of Refrigerator concern, COP with AWG is heist i.e. 1.91. But it cannot be clearly state that, COP with AWG is more than COP without AWG.

Numerical study of the vortex generators effects in a corrugated channel for turbulent flow

Vortex Generators (VGs) are one of many techniques used to improve the efficiency of heat exchangers. In this paper, we will investigate in a numerical study a rectangular winglet and a long winglet VGs inside a corrugated channel with a change of Rynolds number from 5000 to 17500. The role of VGs is to manupilate flow, which increases the Nusselt number (Nu) and increases the friction coefficient, which are considered disadvantages. For that, we calculate the thermal performance coefficient PEC to see if VGs give us more heat compared to what we will lose from friction, and the results show a good PEC greater than 1, and comparing between rectangular and long VGs, we have almost the same results with a small difference in NU for rectangular VGs being higher than long VGs, and the coefficient of friction is smaller, which means we are battered. The results are discussed in detail in this paper.

Plant Waste Drying in an Isothermal Model

The paper highlights advantages of using furnaces for processing vegetable waste, including the absence of condensation, minimal ash production, stable coolant temperature, and efficient heat exchange. To improve this machine and intensify the drying process, it is necessary to gather data on the heat and mass transfer characteristics during high-temperature drying of moisture-laden particles. Due to the inherent challenges of studying the drying process in a real furnace, the experiment was conducted using an isothermal (cold) model under laboratory conditions closely resembling real-world processes. (Research purpose) The research aims to assess the effectiveness of the proposed aerodynamic models for drying plant waste and validate the mathematical model for drying particles in a suspended bed. (Materials and methods) The study employs two suspended bed models with distinct vortex flow aerodynamics (flare and cyclone) in combustion chambers. The study investigates the drying kinetics of two specific fractions of sunflower husks, each with an equivalent particle diameter of 0.25 and 1.5 millimeters, and initial moisture levels of 15 and 18 percent. At various time intervals, measurements were taken for both the temperature and humidity of the husk particles, in addition to recording the temperature and relative humidity of the drying agent as it exited. The drying process operated in a cyclical mode. (Results and discussion) When the sunflower husk particles had an initial moisture content of 15 percent, two phases of increasing drying rates were observed, while at an 18 percent moisture content, three such periods were identified, with the first period displaying a constant rate. The results suggest that when the husks start with an initial moisture content of 15 percent, the drying curves exhibit minimal linear segments. This observation implies that the process is occurring as the drying rate decreases. (Conclusions) The experiment reveals the most effective drying mode in terms of intensity. It becomes evident that both the flarevortex and cyclone-vortex aerodynamic modes facilitate particle drying, with the cyclone-vortex mode delivering a notably more intense drying process. When transitioning from a model to a real-world process, it is essential to undertake a comparison of estimated processes with practical operational conditions, as exemplified by the particle drying model in a suspended bed.

New trilobular geometry using advanced materials for experimentally validated enhanced heat transfer in shallow geothermal applications

The Adapted Conductivity Trilobular (ACT) design, comprising an up-flow central pipe and three satellite downward pipes, represents a novel configuration of a borehole heat exchanger. The novelty lies not only in the geometry of the heat exchanger, but also in the use of materials perfectly adapted to the thermal use for which they have been specified. The central pipe is constructed of a composite bilayer material with very low thermal conductivity, whereas the satellite pipes are based on a novel highly conductive plastic material. The primary objective behind this design was to simplify installation, by using essentially the same drilling and grouting methods used for conventional single-U or double-U borehole heat exchangers. In response to the rising demand for more efficient and affordable ground heat exchangers to be connected to Ground Source Heat Pump (GSHP) systems, this innovation was one of the promising outcomes of the GEOCOND European project. To assess ACT performance, the Geothermal Laboratory on the campus of the Universitat Politècnica de Valencia conducted a number of thermal response tests (TRTs), the experimental results of which are collected and analyzed in this paper. Additionally, a modified version of the Composite Two Region Line Source modeling scheme is described and used to assess the experimental data. A total of four demonstration boreholes – two single-U baseline and two ACT boreholes – have been tested. The experimental investigation using the C2RLS methodology reveals that the ACT configuration has a significantly lower thermal than the typical BHE arrangement and allows a greater specific heat injection rate. Specifically, a borehole resistance drop from 0.149 (m.K)/W to 0.07 (m.K)/W allowing higher injection rates to be achieved without an unsustainable increase in ground temperature. These findings may have significant implications for the development of more efficient and cost-effective GSHP systems.