Analysis and Performance Evaluation of Counter Flow Hairpin Heat Exchangers

Among a variety of heat exchanger types and configurations, hairpin heat exchangers are widely used in engineering processes, especially in chemical and petrochemical industries. They have several operating advantages, such as flexibility and ease of maintenance. The aim of this work is to develop a computer program that is able to evaluate and predict the performance of counter-flow hairpin heat exchangers under different flow conditions. The mathematical framework for thermal and hydraulic calculations is introduced. The developed MATLAB code has been tested for reliability and accuracy against some of the available and approved designs of single-finned tube and bare multi-tube hairpin heat exchangers. Then, it was successfully applied to analyze existing hairpin heat exchangers operating in Alsarir oil field and the Tubrok oil refinery of Arabian Gulf Oil Company (AGOCO) in Libya as case studies. The results show that by changing the operating conditions such as mass flow rates or inlet temperatures of working fluids, the thermal performance of hairpin heat exchangers can be enormously improved without exceeding the allowable pressure drop

A Review of Recent Passive Heat Transfer Enhancement Methods

[EN] Improvements in miniaturization and boosting the thermal performance of energy conservation systems call for innovative techniques to enhance heat transfer. Heat transfer enhancement methods have attracted a great deal of attention in the industrial sector due to their ability to provide energy savings, encourage the proper use of energy sources, and increase the economic efficiency of thermal systems. These methods are categorized into active, passive, and compound techniques. This article reviews recent passive heat transfer enhancement techniques, since they are reliable, cost-effective, and they do not require any extra power to promote the energy conversion systems' thermal efficiency when compared to the active methods. In the passive approaches, various components are applied to the heat transfer/working fluid flow path to improve the heat transfer rate. The passive heat transfer enhancement methods studied in this article include inserts (twisted tapes, conical strips, baffles, winglets), extended surfaces (fins), porous materials, coil/helical/spiral tubes, rough surfaces (corrugated/ribbed surfaces), and nanofluids (mono and hybrid nanofluids).Ajarostaghi, SSM.; Zaboli, M.; Javadi, H.; Badenes Badenes, B.; Urchueguía Schölzel, JF. (2022). A Review of Recent Passive Heat Transfer Enhancement Methods. Energies. 15(3):1-55. https://doi.org/10.3390/en1503098615515

Performance Enhancement of Double Tube Heat Exchanger Using Coiled Fins

The effect of inserting coil wire in the shell side of a doublepipe heat exchanger on the heat transfer and pressure drop areexperimentally investigated. The experiments are performedusing water as the hot and cold working fluid under the turbulentflow condition. Nine coils with different wire diameter (dw = 2, 4and 6 mm) and different coil pitch ratio (P/ dw = 2.5, 5 and 7.5)are used in the study. Results presented an increasing up to 1.59in the heat transfer coefficient while the pressure drop increased10 times compared with the smooth pipe. Results also showedthat the increase in the heat gain is very big than the loss in thepumping power

FIBERGLASS CIRCULAR TURBULATOR IN COUNTER FLOW DOUBLE PIPE HEAT EXCHANGER: A STUDY OF HEAT TRANSFER RATE AND PRESSURE DROP

This preliminary investigation studied the effect of circular turbulator vortex generator on heat transfer rate and pressure drop in a circular channel countercurrent double pipe heat exchanger with water working fluid. Increasing the number of circular turbulator yielded increasing heat transfer rate and pressure drop. The problem generated when increased pressure drop occurred in relation to more energy consumption of the water pumping system. Therefore, optimization in circular turbulator number is necessary to minimize the pressure drop about distance length between circular turbulator, tube diameter and thickness, type of material and crystal lattice, as well as the geometrical shape of fluid passage (circular or square). This study applied PVC outer tube and copper alloy inner tube, as well as fiberglass circular turbulator. The optimum results showed that seven parts of circular turbulator increasing heat transfer rate by 30% and pressure drop by 80% compared to that passage in the absence of circular turbulator at cool water debit of 7 L/min

Advanced thermal energy management: A thermal test bed and heat pipe simulation

Work initiated on a common-module thermal test simulation was continued, and a second project on heat pipe simulation was begun. The test bed, constructed from surplus Skylab equipment, was modeled and solved for various thermal load and flow conditions. Low thermal load caused the radiator fluid, Coolanol 25, to thicken due to its temperature avoided by using a regenerator-heat-exchanger. Other possible solutions modeled include a radiator heater and shunting heat from the central thermal bus to the radiator. Also, module air temperature can become excessive with high avionics load. A second preoject concerning advanced heat pipe concepts was initiated. A program was written which calculates fluid physical properties, liquid and vapor pressure in the evaporator and condenser, fluid flow rates, and thermal flux. The program is directed to evaluating newer heat pipe wicks and geometries, especially water in an artery surrounded by six vapor channels. Effects of temperature, groove and slot dimensions, and wick properties are reported

A Critical Review of Experimental Investigations about Convective Heat Transfer Characteristics of Nanofluids under Turbulent and Laminar Regimes with a Focus on the Experimental Setup

In this study, several experimental investigations on the effects of nanofluids on the con- vective heat transfer coefficient in laminar and turbulent conditions were analyzed. The aim of this work is to provide an overview of the thermal performance achieved with the use of nanofluids in various experimental systems. This review covers both forced and natural convection phenomena, with a focus on the different experimental setups used to carry out the experimental campaigns. When possible, a comparison was performed between different experimental campaigns to provide an analysis of the possible common points and differences. A significant increase in the convective heat transfer coefficient was found by using nanofluids instead of traditional heat transfer fluids, in general, even with big data dispersion from one case to another that depended on boundary condi- tions and the particular experimental setup. In particular, a general trend shows that once a critic value of the Reynolds number or nanoparticle concentrations is reached, the heat transfer perfor- mance of the nanofluid decreases or has no appreciable improvement. As a research field still under development, nanofluids are expected to achieve even higher performance and their use will be crucial in many industrial and civil sectors to increase energy efficiency and, thus, mitigate the en- vironmental impact

Thermal performance investigation of double pipe heat exchanger embedded with extended surfaces using nanofluid technique as enhancement

In the present work, a numerical investigation of heat transfer enhancement in a “double pipe heat exchanger” embedded with an extended surface on the inner tube's outer surface with the addition of “Alumina nanofluid” has been carried out. Through the annuli, water with varying mass flow rates (0.03–0.07 kg/s) and hot de-ionized water with varying Reynolds numbers (250–2500) flows, while hot de-ionized water flows through the inner tube. One type of nanoparticle (Al2O3) having volume concentrations (1%, 3%, and 5%) was used during simulation. Numerical analysis was performed using Computational Fluid dynamics, and the Solid works was used to generate the model. A Semi-Implicit Method for Pressure Linked Equations technique was used to solve the governing equations and discretized using the finite volume method. The simulated results show that the use of a finned tube heat exchanger resulted in an improvement ratio between (2.3) and (3.1). The coefficient of convective heat transfer increased numerically as the volume concentration and Reynolds number increased. The heat transfer coefficient and thermal conductivity rise by 20% and 4.7%, respectively, at a volume concentration of 5%. © 2023 The Author

Thermal Performance of a Double-Pipe Heat Exchanger with a Koch Snowflake Fractal Design

Double-pipe heat exchangers are the simplest type of heat exchanger and are widely utilized in industrial applications. The effectiveness of double-pipe heat exchangers can be increased by using various heat transfer enhancement techniques. Passive heat transfer enhancement methods are desirable as they do not require moving components and are easy to manufacture and maintain. The focus of this study is to implement a passive heat transfer enhancement method and to investigate how thermal performance is impacted. Specifically, the inner pipe in a heat exchanger will be modified to have a cross-section in accordance with the Koch snowflake fractal pattern. The Koch snowflake fractal pattern, when utilized in the heat exchanger, results in an increase in surface area. A validated and verified model of a double-pipe heat exchanger will be used to evaluate the effectiveness of double-pipe heat exchangers inspired by the first three iterations of the Koch snowflake fractal pattern. The performance of the fractal heat exchangers will be compared to a traditional double-pipe heat exchanger operating under identical conditions. It was found that a double-pipe heat exchanger with a cross-section in accordance with the second iteration of the Koch snowflake fractal pattern resulted in an increase in the overall heat transfer coefficient and heat transfer rate of 18% and 75% respectively when compared with a traditional double-pipe heat exchanger with a circular cross-section