Conventional Heat Exchanger Research Articles

Numerical investigation into thermo-hydraulic characteristics and mixing performance of triply periodic minimal surface-structured heat exchangers

The expansive specific area and intricate tortuous topology of triply periodic minimal surfaces (TPMS), which evenly partition three-dimensional space into two separate yet interwoven domains, rendering them highly promising candidates for heat exchanger configurations. Furthermore, advancements in additive manufacturing technology have broken through the limitations of traditional manufacturing methods, enabling the fabrication of triply periodic minimal surfaces no longer out of reach. In this study, a three-dimensional, steady-state, conjugate heat transfer numerical model based on OpenFOAM is developed to compare the performance of four TPMS-structured heat exchangers with that of conventional compact heat exchangers across four dimensions: heat transfer, flow resistance, volume, and weight. Additionally, the flow characteristics within TPMS-structured heat exchangers are investigated. It was discovered that the overall performance evaluation coefficient of three TPMS structures, i.e., Gyroid, Diamond, and IWP, increased by 90–110% compared to printed circuit heat exchanger within Re range of 200–500. This can be attributed to the “merge-split” phenomenon within the channel which enhances both flow mixing and heat transfer. Furthermore, the mixing performance of TPMS structures fluid channels was visualized, quantified, and compared to heat transfer capacity.

Melting performance of nano-enhanced phase change materials in a triple-tube heat exchanger with zigzag-shaped tubes

This study aims at evaluating the melting behavior of nano-enhanced phase change materials (NePCM) inside a triple-tube heat exchanger with a zigzag-shape channel configuration. To assess the performance of the proposed geometry, a zigzag tube with different angles and heights is numerically simulated and the results are compared with the conventional triple-tube heat exchanger. Cu, CuO, Al2O3 and Ag nanoparticles with various concentrations are used to improve the thermal conductivity of NePCMs. The main finding of this research is a significant improvement in the melting performance of a triple-tube heat exchanger by employing a middle zigzag tube. The zigzag configuration with a 67.5° angle and 15 mm height is found as the optimum case with a great potential to (i) reduce the melting time from 4654 s in the case of a straight tube to just 827 s and (ii) increase the heat retrieval rate from just ∼47 W in case of a straight tube to ∼185 W. Among the type of nanoparticles analyzed in this research, Al2O3 has the highest melting performance with ∼14 % increase in the melting rate and heat charge rate at 4 % concentration. Increasing the concentration of Al2O3 nanoparticles from 2 % to 6 % improves the heat charge rate by ∼2.3 %.

DESIGN OF PLATE HEAT EXCHANGER FOR HEAT TREATMENT INDUSTRY

This study discusses the design of plate type heat exchangers (PHE). Conventional heat exchangers have many drawbacks, including difficult maintenance, high cost, and increased area usage. In contrast, plate heat exchangers have a number of benefits over traditional heat exchangers. Because the liquid spreads across the plate, PHE has a bigger surface area. The study discusses and explains the design of the plate type heat exchanger, plate material, chevron angle, and gasket material since the plate allows for faster heat transmission. Key Words: Plate heat exchanger, Design, materials.

Investigation on the Effect of Length and Amplitude of Sinusoidal Wavy Vortex Generators on the Heat Transfer Rate, Pressure Drop, and London Factor in Compact Heat Exchangers

Compact heat exchangers (CHE) improve the heat transfer rate with lighter weight and lower volume than other counterparts. An important point in CHEs is their higher pressure drop relative to conventional heat exchangers. This study aims to investigate the heat transfer rate and pressure drop in some proposed models of these heat exchangers with/without vortex generators (VGs) in different cases. A hot fluid of temperature 350°C flowing through tubes and a cold fluid of temperature 300°C circulating inside the shell are assumed. To this end, several VGs with sinusoidal wavy shapes are designed and examined with different amplitudes of the sine wave and different lengths to determine the effects of these parameters on the heat transfer rate of tubes and pressure drop along the heat exchanger length. In the 2D steady-state laminar fluid flow, governing equations are discretized using the finite element method and analyzed for Reynolds numbers 400 to 1000 in the ANSYS software. Finally, with a 5.06% increase in the Nusselt number, the sinusoidal VGs of amplitude 1 and length 6 mm quantitatively indicated the best performance in terms of the heat transfer rate and pressure drop (London factor) among the studied cases.

Study on the Dynamic Generation of Subcooled Water Using a Compact Heat Exchanger

The dynamic generation of ice slurry from subcooled water is one of the most promising ways to make ice; this process is utilized widely in ice storage air-conditioning systems. However, the random occurrence of ice blockage during the generation of subcooled water using conventional heat exchangers prevents the increase in subcooling, thereby reducing the efficiency of the release of the subcooled water and converting it into ice slurry. A more efficient approach to reducing the fluid passage time is to employ a compact heat exchanger with a highly efficient heat transfer performance, a heat transfer length of only 21.5 mm, and a hydraulic diameter of 0.32 mm. A compact heat exchanger was used to build a dynamic generation setup for subcooled water, and 40 wt% of non-freezing liquid and tap water was used as the working fluid for heat exchange to generate subcooled water. The results show that the compact heat exchanger can achieve a greater subcooling degree (3.8 K) and longer duration (108 min). This study further explored the potential for dynamic ice making from deep, subcooled water and improved the overall structure of the compact heat exchanger used. The experimental setup is recommended based on the analysis of the results.

Technology for Hot Spring Cooling and Geothermal Heat Utilization: A Case Study for Balneology Facility

Reducing energy costs in Europe is more challenging than before due to extreme price increases. The use of local renewable energy sources is one way to contribute to this effort. In the case of spa resorts, the use of heat from hot springs for therapeutic baths is an option. It is necessary to cool down this thermal mineral water to a temperature acceptable to the human body. However, due to the high mineral content of this water, heavy fouling can be a problem for conventional heat exchangers. The purpose of this study is to identify the suitable cooling technology in terms of required cooling capacity and waste heat recovery capability. The cooling technology was selected on the basis of a literature search. A pilot cooling unit consisting of vacuum cooler and plate heat exchanger was designed and tested in a real spa resort for six months. Both selected technologies have demonstrated the ability to cool thermal mineral water in long-term operation, as well as the possibility to utilize waste heat for domestic hot water heating. However, fouling problems occur in the plate heat exchanger. The vacuum cooler demonstrated greater operational robustness and resistance to encrustation.

Numerical investigation of thermal-hydraulic design of a printed circuit steam generator

Steam generator is the biggest component of SMR. Therefore, reducing the size of the steam generator will ultimately affect the overall size of the module. Printed Circuit Heat Exchanger (PCHE) is a compact type of heat exchanger that offers a promising prospect for replacing conventional U-tube heat exchangers. Due to its high heat transfer surface area to volume ratio and its capability in high-pressure applications, PCHE can be used as steam generators in SMRs. This study investigates the possibility of using PCHE heat exchanger as a steam generator using Computational Fluid Dynamics (CFD). CFD study was performed on a reduced numerical model consisting a of single unit cell of the PCHE block keeping in view of the periodic structure of the geometry. CFD model was validated against the results of Haratyk et al. Thermal hydraulic performance of zigzag channel geometry was also analyzed for various bend angles ranging from 15°, 25°, 35°, and 45° for mass fluxes ranging from 1000 kg/m2s to 2250 kg/m2s. The friction factor, Nusselt Number and performance factor are calculated for various mass flow rates. Nusselt Number increases with bend angle and mass flux, whereas the friction factor decreases with mass flux and increases with bend angle. A maximum value of 1.45 for the performance factor was attained for a bend angle of 35° in comparison to the straight channel. The performance factor was improved further to 1.5 by introducing a short straight section having a length of 5 mm at each zigzag bend with a bend angle of 35°.

Enhanced thermal and mechanical performance of 3D architected micro-channel heat exchangers

Many crystals in nature have simple interatomic microstructures, such as simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC) lattice symmetries, making these structures extremely stable. Inspired by these arrangements, a series of architected micro-channel heat exchangers with rationally designed 3D microstructures were established. A multi-physics mathematical model using thermal-fluid-structure interaction (TFSI) was employed to investigate the coupled heat transfer performance and mechanical properties of these architected heat exchangers. When compared with the corrugated straight plate (CSP) microchannel heat exchanger, the thermal-hydraulic performance factors (TPC) of FCC and BCC microchannel heat transfer were 2.20 and 1.70 times that of SC microchannel heat exchanger, respectively. The micro-channel heat exchanger with FCC architectures could enhance the convective heat transfer performance by 201.0%, while the micro-channel heat exchanger with SC architectures reduced the Von-Mises equivalent (VME) stress by 20.0% when compared with the conventional 2D CSP heat exchanger. The proposed architected micro-channel heat exchangers could find a wide range of potential applications ranging from power electronics in electric vehicles to concentrated solar power systems, where both good convective heat transfer performance and high mechanical strength are simultaneously pursued.

Investigating the effect of stream reflux on optimum design of heat exchanger using Particle Swarm Algorithm

BackgroundA heat exchanger is a device that is used to transfer thermal energy between two or more fluids, between a solid surface and a fluid at different temperatures in thermal contact. In this paper, plate fin heat exchanger (PFHE) is optimally designed for a waste heat recovery purpose. MethodsFor optimal design of PFHE, total annual cost as well as effectiveness are considered as two objective functions and a multi-objective particle swarm optimization (MOPSO) algorithm is used. In addition, six design parameters related to the heat exchanger and fin variables are selected. Stream reflux is considered as a new idea to improve the thermoeconomic result of heat exchanger. As a result, an additional design parameter named “reflux ratio” is also considered in the case of heat exchanger with stream reflux. The optimum results in the case of stream reflux were compared with those without stream reflux (conventional heat exchanger). Significant findingsThe optimization results revealed that 4.42% improvement in the maximum effectiveness is obtained by refluxing the stream as compared with conventional case. In addition, the thermoeconomic improvement was obtained by stream reflux for the effectiveness higher than 0.8859. For example, 4.11% improvement in the effectiveness is observed in the case of stream reflux as compared with the conventional case for the fixed TAC=553.6 $/year. As it is predicted, the zero value for reflux ratio is selected for the effectiveness lower than 0.8859. On the other hand, the reflux ratio is selected in the range of 0–0.9311 for the effectiveness higher than 0.8859. In addition, the results reveal that the higher reflux ratio is required for the higher effectiveness.

The effect of minichannels on the overall heat transfer coefficient and pressure drop of a shell and tube heat exchanger: Experimental performance comparison

Channels with small hydraulic diameters improve the overall heat transfer coefficient (OHTC) and compactness of shell and tube heat exchangers (STHEs). Intensified compactness decreases both the weight and volume of heat exchangers and allows us to use less working fluid. This study experimentally investigated the effects of minichannels on the OHTC and pressure drop performance of a STHE for five different thermal and hydrodynamic operating conditions. Present study also compared the experimental OHTC and pressure drop results of the mini-channel shell and tube heat exchanger (MC-STHE) with those of previously reported experimental results of conventional STHEs under different conditions. The MC-STHE had an OHTC of 1.1–6.6 times as high as the conventional heat exchangers. Besides, the minichannels increased the OHTC of the STHE to ∼6700 W/m2K and yielded a higher pressure drop than the macro tube heat exchangers at Re ≅ 14,000 (∀˙ = 600 L/h).

Numerical study of the cold finned-tube bundle heat exchanger under natural convection for a novel passive displacement cooling system

In a passive displacement cooling (PDC) system, conventional finned-tube heat exchangers are being employed and their performance is not optimal under natural convection. In this study, an experimental set-up has been established to validate the numerical model for finned-tube heat exchanger optimization under natural convection. The numerical difference between the predicted and measured data is less than 3.4%, showing that the numerical model could predict the heat transfer and flow rate accurately under natural convection. Subsequently, the effects of fin spacing, coil configuration, tube row number, and fin depth on the coil performance under natural convection have been investigated. The results show that the one-row coil performs better than the two-row coil for a PDC system with 8-10 fins per inch (FPI), despite the smaller heat transfer area. Compared with the conventional two-row circular-tube coil with 10FPI, the one-row circular-tube coil improves the mass flow rate and heat transfer rate by around 29.1% and 20.0% respectively. The findings enable a more responsive and energy-efficient PDC system for green buildings.

Study of Particulate Fouling Inhibition Characteristics on a Novel Composite Coating

Particulate fouling is a common fouling in heat exchange equipment, it causes tube corrosion and increases flow resistance. Particulate fouling increases the hidden danger of equipment and requires high treatment costs. In this paper, a novel Ni−P−TiO2 composite coating is prepared on 316 stainless steel using electroless plating and the fouling inhibition characteristics of the novel composite coating are studied using a dynamic monitoring experimental system. The experimental results show that the fouling thermal resistance of the Ni−P−TiO2 composite coating is obviously lower than that of 316 stainless steel under the same working conditions. With the increase in cooling water velocity and inlet temperature, the surface fouling thermal resistance decreases, while, with the increase in particle concentration, the fouling thermal resistance increases. Based on DLVO theory, it is found that the surface energy of Ni−P−TiO2 composite coating is close to the best surface energy for inhibiting particulate fouling deposition, which can significantly inhibit particulate fouling deposition. Compared with the stainless-steel surface of a conventional plate heat exchanger, the Ni−P−TiO2 composite coating not only inhibits the accumulation of particulate fouling, but also reduces the adhesion strength of particulate fouling; additionally, the fouling is easier to strip off the heat exchange surface, which realizes the lasting and efficient fouling inhibition on the heat exchange surface. The research results can provide a data reference for the fouling inhibition design and daily efficient operation of heat exchangers.

Performance of a thermoelectric heat pump with recirculation and regenerative heat recovery

In this paper, the thermoelectric heat pump performance is enhanced by air recirculation and regenerative energy recovery. Compared to conventional vapor-compressed heat pumps, TEHP is more stable, safer, and flexible in arrangement, but is relatively less efficient. Therefore, the use of air recirculation combined with regenerative heat recovery is dedicated to increasing the efficiency of the heat pump and recovering some of the energy, thus reducing energy consumption. Experimental results show that the COP of the air recirculation TEHP is as high as about 3.7. At 1 m/s air velocity, the COP with recirculation is 51–73% higher than without recirculation. In the system experiments for heat exchanger test applications, the percentage of regenerative heat recovery was up to 12%. The combination of regenerative heat recovery and air recirculation further improved the energy efficiency of the heat exchanger test system to a maximum energy efficiency ratio of 2.85. The energy-saving measures of TEHP with recirculation and regenerative heat recovery resulted in better energy savings than the conventional heat exchanger test device with resistance heating. It is of great reference significance in fields of thermoelectric technology applications.

Numerical study on heat and flow transfer characteristics in rectangular mini-channel with S-shaped turbulator inserted

The mini-channel heat exchanger has better heat and flow transfer characteristics than conventional heat exchanger. In this study, we use the S-shaped turbulator inserted, which is simple to install and inexpensive, to improve the heat exchange. The fluid-flow and heat transfer characteristics in smooth and inserted S-shaped turbulator rectangular mini-channels are simulated by numerical simulation under constant wall temperature heating in the Reynolds number 198.77-1987.67. The results of the numerical simulation show that compared with the smooth mini-channel, the pressure drop of the three rectangular mini-channels with different inserted S-shaped turbulators with radii on the horizontal axis of 1 mm, 1.5 mm, and 2 mm increase by 334.8-774.3%, 275.9-606.4%, and 234.6-500.4%. The average Nusselt numbers grow by 28.7-98.6%, 18.8-92% and 11.1-88.5%. The total thermal resistances reduce by 22.43-50.15%, 15.91-48.40%, and 10.08%-47.45%. The field coordination numbers increase by 30.36%-115.29%, 19.72-106.94%, and 19.72-104.72%. Moreover, the non-linear regression method establishes the prediction formulas of the pressure drop and average Nusselt number. In most cases, the deviation between predicted and simulated values is between ?4.6% and ?14%.

Study on an advanced borehole heat exchanger for ground source heat pump operating in volcanic island: Case study of Jeju island, South Korea

This paper presents an advanced borehole heat exchanger that has been developed in order to apply a ground source heat pump to a volcanic island where the existing borehole heat exchangers are inapplicable by local ordinance. The advanced borehole heat exchanger was fabricated and installed at a verification-test site to evaluate its heat capacity in terms of refrigeration ton (RT). The proposed heat exchanger was also compared with the conventional heat exchanger that was made of high-density polyethylene (HDPE) heat exchanger. The thermal response test was carried out by flowing water at various temperatures into the heat exchangers at the fixed flow rate of 180 L/min. The results revealed that the maximum heat capacity for the developed heat exchanger was measured at 63.9 kW, which is 160% higher than that of the high-density polyethylene heat exchanger (39.9 kW). It was also found that the developed HX has the highest heat gain achieving 94 kW as compare to 21 kW for high-density polyethylene-Hx.

Experimental and numerical study on the heat transfer and flow characteristics of convex plate heat exchanger based on multi-objective optimization

The convex plate heat exchanger is one of the new types of plate heat exchangers that have specific functional properties compared to conventional plate heat exchangers, the structural parameters of convex plate heat exchangers are important in affecting the heat transfer performance. In this paper, based on two-layer multi-objective optimization which is aimed at maximum performance evaluation criterion (PEC) and maximum field synergy number (Fc), the heat transfer and flow characteristics of convex plate heat exchanger are investigated experimentally and numerically. The optimization findings are broken down into single factor, response surface, and sensitivity analysis. The optimal results under different objective functions are analyzed and the optimal structural parameters obtained which are the welding hole radius (R) is 5.81 mm, the ellipse radius (L) is 5.02 mm, and the welding hole spacing (P) is 64.00 mm; Compared to the structure before optimization, the size-optimized structure may enhance the temperature differential between the inlet and outflow of the cooling water by less than 8.27%, the heat transfer performance is increased by 20.43%, and the comprehensive performance is improved by 2.3∼19.59%.

Turbulent thermal-hydraulic characteristics in a spiral corrugated waste heat recovery heat exchanger with perforated multiple twisted tapes

Waste heat recovery technology can undoubtedly improve energy saving and reduce carbon emissions, as one of the key equipment, heat exchangers always determine the waste heat recovery efficiency. In this study, to improve the heat transfer potentiality of conventional plain tube heat exchangers, a synergistic thermal enhancement technology of a spiral corrugated tube (SCT) with multiple twisted tapes (TTs) was devised by taking liquid-gas heat exchanging as a typical waste heat recovery scenario. The impacts of the TTs numbers, transverse space ratios (S/D), and longitudinal perforation length ratios (L/D) on tubular turbulent heat transfer-fluid flow characteristics were numerically investigated, consisting of flow fields, temperature contours, local Nusselt number (Nu) distributions, vortex structures, and turbulent kinetic energy contours, as well as average Nu, friction factor (f), and overall thermal performance evaluation index (η). The findings proved that the fitting of multiple TTs into the SCT greatly homogenized the flow fields and temperature distributions, and increased the Nu and f, in which both of them also raised with the increase of the number of TTs. The η dropped and subsequently augmented as the quantity of TTs increased. Furthermore, perforations on the surface of the quadruple TTs could attenuate the f with a relative less reduction in the Nu, which caused higher η values than the ones without perforations. Notably, as demonstrated by the vortex structures, this could be ascribed to the fact that the perforations reduced excessive longitudinal vortex interactions in the mainstream regime without reducing the impingement to the thermal boundary layer too much. Both the Nu and f generally declined with rising S/D and L/D. Overall, by means of simple mounting perforations on the surface of the quadruple TTs, the maximum η could be further enhanced up to around 7.9% and a maximum η of 1.23 was obtained by the SCT with S/D = 0.152 and L/D = 0.348.

Simulation of nanofluid micro-channel heat exchanger using computational fluid dynamics integrated with artificial neural network

Waste heat utilization has been prioritized especially in various industries and sectors. Many researchers have developed heat recovery processes by designing suitable waste heat recovery units (WRU), such as heat exchangers, using water as a coolants to receive heat from the waste heat fluid in the production process. The conventional heat exchanger has limitations such as its equipment size, space for installation, and flexibility. The microchannel heat exchanger is one of many ideas for resolving these limitations. Moreover, the coolant on the cold side can be upgraded by adding nanometer-sized solid particles which is called “Nanofluid”. To reduce the high investigation cost and time, a new efficient and cost-effective simulation method was selected to use for investigating the performance of a microchannel heat exchanger with nanofluids in this study. To analyze the heat recovery at low temperature, i.e. around 100–200 °C, nanofluid property predictive models were developed using an artificial neural network (ANN). Then, the predictive models were embedded and integrated into computational fluid dynamics to design a microchannel heat exchanger. It is found that the use of nanofluids improved the heat transfer efficiency of this heat exchanger. The suitable nanofluid types and concentrations were selected based on the thermal–hydraulic​ performance. Here, the 3% weight TiO2/Water fluid with a 1.03 thermal–hydraulic​ performance ratio was found to be the most promising nanofluid for using in this condition.

Design and performance prediction of desiccant coated heat exchanger using ANFIS–AI tool and dynamic model

• Development of ANFIS–AI tool for design and performance optimization of DCHE. • Predicted optimal design and inlet condition of DCHE using ANFIS–AI tool. • Investigated the influence of design and inlet parameters on DCHE performance. • Assessed adsorption kinetics of DCHE using dynamic model based on Laplace transform. • Examined the interactive effect of Lewis and Stanton numbers on performance of DCHE. To improve indoor air quality, enhance the energy exchange capabilities and minimize the spread of microbial pollutants, desiccant coated heat exchanger seems a promising alternative to conventional heat exchangers such as rotary wheel and adsorber beds. Thus, precise prediction of the design and performance characteristics of desiccant coated heat exchanger is vital for improving the overall air conditioning system performance. Therefore, in the present investigation, an adaptive neuro-fuzzy inference system with artificial neural network fuzzy logic has been implemented to predict the exit parameters of desiccant coated heat exchangers. The advantage of an adaptive neuro-fuzzy inference system is its structure that combines the neural network's learning ability, excellent information representation capability of fuzzy logic, and adaptive algorithm. Silica gel is taken as the coated desiccant. The impact of inlet and design parameters on the performance characteristics of desiccant coated heat exchanger during dehumidification has been evaluated using the artificial intelligence adaptive neuro-fuzzy inference system. Also, the optimal design/inlet conditions for the given operating and design parametric range are obtained. For the obtained optimal conditions, the maximum valves of dehumidification capacity, vapor pressure difference ratio, and sensible energy load ratio are 2.01 kg/h, 0.84, and 0.135, respectively. Further, a dynamic model based on the Laplace transform is developed to assess desiccant coated heat exchangers' adsorption kinetics and thermal effects. Moreover, the interactive effect of Lewis number and Stanton number on the performance parameters has been examined judiciously. Adsorption kinetics of silica gel shows that the water adsorped per mass desiccant is about 0.1129 g/g at the end of sorption time.

Numerical investigation of lamella heat exchanger for engine intake charge air cooling utilizing refrigerant as coolant medium

Intercooler heat exchangers (IHE) are used to improve engine charge air temperature, which enhances engine efficiency and reduces emissions. The current study introduces a novel intercooler heat exchanger designed to improve combustion and engine performance by providing cold intake air. Lamella heat exchanger is proposed, based on space availability in existing engines, operated as an evaporator utilizing a refrigeration unit, the same used for vehicle compartment cooling. A numerical investigation is carried out for a 1.496 L naturally aspirated engine at rpm 4000, 5000, and 6000. The intake air temperature is taken as 45 °C to examine the proposed four models: model A, model B, model C & model D bearing aspect ratios of 21.6 mm, 27 mm, 36 mm & 43.2 mm, respectively. The study aims to obtain high heat transfer with minimal pressure loss. For that, the evaluation criteria for all models are heat transfer, temperature drop, number of transfer units, logarithmic mean temperature difference, and pressure drop. As a result, all models under consideration are ranked from high to low; model D, model C, model B, and model A. The maximum heat transfer of 1.55 KW and the maximum temperature drop of 24.06 °C are observed for model D at rpm of 6000 and 4000, respectively. Likewise, the maximum pressure drop is recorded for model D at all rpm ranges; still, the pressure drop for model D is less than 28 % of the reference model used in this study at 6000 rpm. The simulated results indicate that all evaluation parameters except LMTD are directly proportional to the aspect ratio of the lamella. Due to their compactness, the proposed heat exchanger designs offer more surface area per unit volume, resulting in higher thermal capacity than the other conventional intercooler heat exchangers.