Flow Heat Exchanger Research Articles

Comparative Study of Helical Coil, Spiral Coil and Conical Coil (90O) Heat Exchanger for Single Phase Fluid Flow

In the present study experimental analysis of the helical, spiral and conical coil with cone angle 90O for single-phase fluid flow is reported. Three different coil configurations are analysed under steady-state conditions. These three different coils (helical, spiral and conical coils) are formed with the same average coil diameter, tube diameter and tube length. For the analysis, an experimental setup with suitable instrumentation is developed. For each coil, sufficient numbers of test runs are conducted and readings are recorded with constant inlet temperature of cold and hot fluids as well as constant flow rate in every test run, to ensure the steady state. From the recorded results of the experimentation, heat transfer coefficients are calculated and the calculations are extended to calculate the Nusselt number (Nu) and effectiveness. The comparison of the results is presented from the analysis. Furthermore, the analysis is extended to predict the outlet temperature of hot and cold fluid, which shows good agreement with the experimental values. Major Findings: The helical coil exhibited the highest Nusselt number (Nu), while the spiral coil had the lowest Nu. The conical coil demonstrated intermediate Nu values. The effectiveness (ε) of the coiled tube heat exchanger is inversely proportional to the parameter Z. Consequently, the effectiveness of the system can be readily predicted using graphical patterns.

Experimental Investigation of Thermo-Hydraulic Characteristics and Sustainability Measure of a Novel Multi-Fluid Heat Exchanger for Turbulent Water-Based Nanofluid Flow Through the Inserted Brazed Helix Tube

Abstract A novel multi-fluid heat exchanger deployed for simultaneous heating of water and space is experimentally investigated to predict its thermo-hydraulic, exergetic, and sustainability performance for distinct Al2O3, TiO2, and CuO nanofluid (NF) flow of 50 ppm concentration of each through the inserted brazed helix tube (BHT). The input parameters such as flowrates, helix tube diameters, and nanofluid types are varied throughout the experiments to evaluate their effect on output performance parameters i.e., Nusselt number (Nu), friction factor ( f), entropy generation number (Ns), JF factor (JF), exergy efficiency (ƐE), and sustainability index (SI). The NF flowing through the BHT is the heating fluid that simultaneously heated the cold water, and cold air flowing through the outer shell and inner conduit of the BHT respectively. A distinct Nusselt number correlation for turbulent nanofluid flow inside BHT was developed, compared, and validated reasonably with the current result. For Al2O3 NF at a Reynolds number of 5698 with a 1/2-in. diameter helix tube, the best results for JF, ƐE, and SI are found to be 0.009, 0.72, and 3.53, respectively. Furthermore, for Al2O3 and TiO2 NF at a Reynolds number of 14,250 and a helix tube diameter of 3/8 in. and 1/2 in., f, and Ns are found to be 0.0047 and 0.043, respectively are minimum. It is observed that the use of Al2O3 NF, higher helix tube diameters, and lower flowrates all make the proposed heating application more sustainable.

Thermohydraulic performance of a printed circuit heat exchanger with ribbed cross-connected semicircular channel

The printed circuit heat exchanger is a highly efficient device characterized by its compact design and exceptional resistance to high temperatures and pressures, enabling its widespread application in various fields. This study introduces a novel channel design for the printed circuit heat exchanger, where a ribbed cross-connected channel structure is implemented to enhance heat transfer performance compared to traditional designs. The Finite Volume Method is employed to simulate the effects of rib structure parameters (d/e) on the printed circuit heat exchanger's flow and heat transfer characteristics under laminar flow conditions. The results demonstrate that incorporating a unique ribbed channel design generates stronger longitudinal vortices, leading to a more uniform mixing of the fluid in the channel. At the same time, the presence of ribs reduces the thickness of the thermal boundary layer, thereby leading to more effective heat exchange in compact spaces. Compared to channels without ribs, Nu for the ribbed cross-connected channels increased by up to 24.51%, with a corresponding 32.02% increase in f. The study reveals that the optimal heat transfer performance is obtained with a height-to-width ratio of 5, whereas the best overall performance is attained with a height-to-width ratio of 4. When d/e = 4, the performance evaluation criterion is enhanced by 14.5% compared with the channel without ribs. The proposed ribbed cross-connected channel can significantly enhance thermohydraulic performance, offering substantial potential for practical applications in printed circuit heat exchangers.

In-building direct wastewater heat recovery solutions for enhancing thermal efficiency in domestic hot water systems

Enhancing energy efficiency in buildings is necessary for reducing environmental impact and operational costs, with domestic hot water (DHW) systems accounting for a significant portion of residential energy consumption. This paper provides a comprehensive overview of in-building direct wastewater heat recovery (WHR) systems as a means to improve thermal efficiency in DHW systems. Various direct WHR technologies are explored, focusing on vertical and horizontal heat exchangers, detailing their design, operation, and efficiency. The study analyses factors influencing the performance of these systems, including heat exchanger design, temperature differentials, flow rates, and maintenance requirements. Case studies are presented to demonstrate the practical applications and energy savings potential of WHR systems in residential and commercial buildings. Despite the clear benefits, challenges such as installation complexity, maintenance needs, usage patterns, and initial costs hinder widespread adoption. Retrofitting existing buildings poses significant hurdles due to space constraints and plumbing modifications, while maintenance is essential to prevent efficiency losses from fouling. The effectiveness of WHR systems is also influenced by the synchronization of hot water usage and wastewater production, which can be intermittent in residential settings. Economic considerations, particularly the upfront investment, can deter stakeholders despite favourable long-term returns.

Performance analysis of parallel flow heat exchanger based on water and R134a

Performance analysis of parallel flow heat exchanger based on water and R134a

Design Optimization of a Shell-and-Tube Heat Exchanger Based on Variable Baffle Cuts and Sizing

Abstract This article investigates the optimization of a shell-and-tube heat exchanger design through the optimization of baffle spacing and cut. This study focuses on the impact of baffle spacing (20–35%) and baffle cut percentage (20–35%) on heat transfer performance while considering the effect of the presence or the absence of seals. This study aims to optimize the heat exchanger design by using computational fluid dynamics (CFD) to reduce the pressure drop and increase the heat transfer. Studying the flow in heat exchangers is challenging due to its complex physics, especially in nonstandard geometries or novel fluid systems, which makes traditional methods relatively less accurate compared to modern approaches. The following fluid is so far uninvestigated for CFD analysis of heat exchangers: a mixture of 80% ethanol and 20% water is used as the tube-side fluid and water is used as the shell-side fluid. The Bell–Delaware method is employed for initial thermal analysis, followed by CFD simulations using ansys fluent to assess the influence of design modifications on heat transfer efficiency and pressure drop. The presence of seals is shown to improve the heat transfer efficiency by about 10.9% compared to the case when seals are absent, while optimal baffle spacing and baffle cuts are able to increase the efficiency of the heat exchanger by about 110% not inclusive of the effect of seals. Our findings show that the performance of a shell-and-tube heat exchanger is improved dramatically by the addition of seals and optimal selection of baffle cut and spacing.

Enhancement of heat transfer using elliptical twisted inner pipe with convergent conical ring turbulator for turbulent flow in double pipe heat exchanger

Enhancement of heat transfer using elliptical twisted inner pipe with convergent conical ring turbulator for turbulent flow in double pipe heat exchanger

New Two-Phase Multiplier Model for Phase-Change Flows in Plate Heat Exchangers

A complete thermo-hydraulic understanding of condensing and evaporating flows in heat exchangers requires predictive modeling and analysis of not just heat transfer but also the hydraulics of the flow. While modeling the friction factor and pressure gradient yields a quantitative understanding of the pressure drop, only the two-phase multiplier and void fraction, in combination with the Martinelli parameter, help better understand the relative contributions of the liquid and vapor fractions to the overall pressure drop. This article reports the empirical modeling, analysis, and meta-analysis of the two-phase multiplier for condensing and evaporating flows in plate heat exchangers. Over three thousand data compiled from forty-two sources were modeled using various regression techniques to develop correlations for predicting the two-phase multiplier for condensing and evaporating flows in plate heat exchangers. The Weber number for most studies was less than one, indicating that drop condensation and pool boiling were impossible. Further, the Bond number for most studies was also much higher than one, indicating that the buoyancy effects were significant during condensation and evaporation. Meta-analysis for evaporators was statistically significant and positive, strongly recommending plate heat exchangers.

Experimental Evaluation of Gas-Dynamic Conditions of Heat Exchange of Stationary Air Flows in Vertical Conical Diffuser

Conical diffusers are widely used in technical devices (gasifiers, turbines, combustion chambers) and technological processes (ejectors, mixers, renewable energy). The perfection of flow gas dynamics in a conical diffuser affects the intensity of heat and mass transfer processes, the quality of mixing/separation of working media and the flow characteristics of technical devices. These parameters largely determine the efficiency and productivity of the final product. This article presents an analysis of experimental data on the gas-dynamic characteristics of stationary air flows in a vertical, conical, flat diffuser under different initial boundary conditions. An experimental setup was created, measuring instruments were selected, and an automated data collection system was developed. Basic data on the gas dynamics of air flows were obtained using the thermal anemometry method. Experimental data on instantaneous values of air flow velocity in a diffuser for initial velocities from 0.4 m/s to 2.22 m/s are presented. These data were the basis for calculating and obtaining velocity fields and turbulence intensity fields of the air flow in a vertical diffuser. It is shown that the value of the initial flow velocity at the diffuser inlet has a significant effect on the gas-dynamic characteristics. In addition, a spectral analysis of the change in air flow velocity both by height and along the diffuser axis was performed. The obtained data may be useful for refining engineering calculations, verifying mathematical models, searching for technical solutions and deepening knowledge about the features of gas dynamics of air flows in vertical diffusers.

Numerical Investigation of Flow and Thermal Fields in Heat Exchanger with Two Porous Vertical Baffles

Numerical Investigation of Flow and Thermal Fields in Heat Exchanger with Two Porous Vertical Baffles

Heat transfers in heat exchangers in steady and oscillating flows

Heat exchangers are a key constitutive element in thermoacoustic machines. Although they are required to operate with oscillating gas, their design is mostly guided by direct extrapolation of the knowledge applicable to steady flow heat exchangers, due to the lack of objective criteria for the design of oscillating flow heat exchangers. Most of the works in the literature present theoretical or numerical results, but very few experimental data are available to confirm (or refute) the strong hypothesis leading to the extrapolation. This study presents the comparative measurements of the heat transfers capabilities of triangular louvered fin heat exchangers in steady and oscillating flows under otherwise similar conditions.

Experimental study on the heat storage characteristics of rock bed heat storage system with different packing structure

Experimental study on the heat storage characteristics of rock bed heat storage system with different packing structure

Prediction of thermo-hydraulic properties of flow in an innovative plate heat exchanger using machine learning algorithms

Reducing fuel consumption and toxic gas emissions is a major concern in modern energy research. This paper investigates the performance and heat transfer enhancement of an innovative plate heat exchanger (IPHE) using machine learning techniques. By optimizing the geometric parameters of the plate, we predict thermohydraulic characteristics—represented by the Nusselt number (Nu), coefficient of friction (f), and performance (P) within the Reynolds number range of 500–5000 based on numerical modeling data. This study addresses the need for improved efficiency in plate heat exchangers (PHEs) amid rising energy demands and environmental concerns. Traditional methods like numerical simulations or costly experiments have limitations, prompting interest in artificial intelligence (AI) and machine learning (ML) for thermal analysis and property prediction in PHEs. Various ML models, including Decision Trees, XGBoost, Gradient Boosting, and ensemble methods, are evaluated in predicting f, Nu, and overall performance (P). Our comprehensive experimentation and analysis identify top-performing models with robust predictive capabilities. For f, the highest R2 score was 0.98, indicating excellent prediction accuracy, with mean squared error (MSE) values consistently below 0.0016. Similarly, for Nu and P, top models achieved R2 scores of 0.979 and 0.9628, respectively, with MSE values below 0.0347 and 0.05. These results highlight the effectiveness of machine learning techniques in accurately predicting thermohydraulic properties and optimizing PHE performance.

Investigation of MHD Heat Exchange in a Liquid Metal Flow through a Tube-in-Channel System under Conditions Close to the Thermonuclear Reactor Blanket Module

Investigation of MHD Heat Exchange in a Liquid Metal Flow through a Tube-in-Channel System under Conditions Close to the Thermonuclear Reactor Blanket Module

Analysis on heat transfer enhancement mechanism in a cross-wavy primary surface heat exchanger based on advection thermal resistance method

Analysis on heat transfer enhancement mechanism in a cross-wavy primary surface heat exchanger based on advection thermal resistance method

EXPERIMENTAL STUDIES OF THE AIR FLOW HEATING PROCESS IN A VERTICAL SOIL HEAT EXCHANGER

The article considers the possibilities of using the soil as a source of low-potential heat in Ukraine, where it maintains a constant temperature at a depth of more than 10 meters +9…12 °C throughout the year. This creates favorable conditions for efficient use of heat pumps. The analysis of technical means of extracting thermal energy from the surface layers of the soil shows that vertical soil heat exchangers are the most effective for achieving the required parameters of the microclimate in livestock premises. The study of the process of heating the air flow in the vertical soil heat exchanger was carried out under production conditions at the pig farm of the Agrofirma Napadivska Agricultural Company in the Vinnytsia region. To increase the efficiency of the clean air injection system, a U-shaped vertical soil heat exchanger is installed, which is connected to the ventilation system of the pig fattening room. Research was conducted at different levels of air flow (200, 500, 800 m³/hours) and air temperature in the soil heat exchanger, which was fixed six times a day. Indicators of climatic conditions were determined by measuring temperature and air humidity, as well as by monitoring temperature dynamics throughout the year. According to the results of experimental studies of the process of heating the air flow in a U-shaped vertical soil heat exchanger in production conditions, the dynamics of temperature changes throughout the year were determined. The obtained regression equations of the second order of changes in air flow temperature ΔTa and effective heat capacity NE from temperature Tin and expenses Qin air flow at the entrance to the U-shaped vertical soil heat exchanger.Statistical comparison of experimental data with theoretical dependence by the Pearson correlation coefficient – 0,95 and Fisher's test – F = 1,93 < Fт = 2,98 indicates the high adequacy of theoretical dependencies.

Experimental investigations on thermo-fluid performance of perforated baffle aided with oppositely oriented sawtooth deflector in tubular heat exchanger

Purpose The investigation concentrated on studying a distinct category of tubular heat exchanger that uses swirling airflow over tube bundle maintained at constant heat flux. Swirl flow is achieved using a novel perforated baffle plate with rectangular openings and multiple adjustable opposite-oriented saw-tooth flow deflectors. These deflectors were strategically placed at the inlet of the heat exchanger to create a swirling flow downstream. Design/methodology/approach The custom-built axial flow heat exchanger consists of three baffle plates arranged longitudinally supporting tube bundle maintained at constant heat flux. The baffle plate equipped with saw-tooth flow deflector of various geometry represented by space height ratio(e/h). Next, ambient air was then directed over the tube bundle at varying Reynolds number and the effect of baffle spacing (PR), Space height ratio (e/h) and inclination angle(a) of deflectors on performance of heat exchanger was experimentally analyzed. Findings The heat transfer augmentation of heat exchanger for given operating condition is strongly dependent on geometry, inclination angle of deflector and baffle spacing. Originality/value An average improvement of 1.42 times in thermal enhancement factor was observed with inclination angle of 30°, space height ratio of 0.4 and a pitch ratio of 1.2 when compared to a heat exchanger without a baffle plate under similar operating conditions.

Experimental study on flow and heat transfer of High-Pressure helium flow in compact helical tube heat exchanger in HTGR

Experimental study on flow and heat transfer of High-Pressure helium flow in compact helical tube heat exchanger in HTGR

Experimental investigation of the effects of metal foam porous rings on non-Newtonian fluid flow in a double pipe heat exchanger

Experimental investigation of the effects of metal foam porous rings on non-Newtonian fluid flow in a double pipe heat exchanger

Gas dynamics and heat exchange of stationary and pulsating air flows during cylinder filling process through different configurations of the cylinder head channel (applicable to piston engines)

Gas dynamics and heat exchange of stationary and pulsating air flows during cylinder filling process through different configurations of the cylinder head channel (applicable to piston engines)