CFD-Based Optimization of a Shell-and-Tube Heat Exchanger

The main objective of this study is the technical optimization of a Shell-and-Tube Heat Exchanger(STHE).In order to do so,a simulation model is introduced that takes into account the related gas-phase circulation.Then,simulation verification experiments are designed in order to validate the model.The results show that the tem-peraturefield undergoes strong variations in time when an inlet wind speed of 6 m/s is considered,while the heat transfer error reaches a minimum of 5.1%.For an inlet velocity of 9 m/s,the heat transfer drops to the lowest point,while the heat transfer error reaches a maximum,i.e.,9.87%.The pressure drop increasesfirst and then decreases with an increase in the wind speed and reaches a maximum of 819 Pa under the 9 m/s wind speed con-dition.Moreover,the pressure drops,and the heat transfer coefficient increases with the Reynolds number.

Analysis of influence of heat exchangerfouling on heat transfer performancebased on thermal fluid coupling

A study on heat transfer performance by thermal fluid coupling simulation for the fouling in a shell-tube heat exchanger used in engineering was presented. The coupling simulation was performed in a fluid and solid domains under three different fouling conditions: fouling inside the tube, fouling outside the tube, and fouling inside the shell. The flow field, temperature, and pressure distributions in the heat exchanger were solved numerically to analyze the heat transfer performance parameters, such as thermal resistance. It is found that the pressure drop of the heat exchanger and the thermal resistance of the tube wall increase by nearly 30% and 20%, respectively, when the relative fouling thickness reaches 10%. The fouling inside the tube has more impact on the heat transfer performance of the heat exchanger, and the fouling inside the shell has less impact.

Simulation and Optimization of the Fluid Solidification Process in Brazed Plate Heat Exchangers

When a brazed plate heat exchanger is used as an evaporator,the working mass in the channel may undergo soli-dification,thereby hindering the refrigeration cycle.In this study the liquid solidification process and its optimi-zation in a brazed plate heat exchanger are investigated numerically for different inlet velocities;moreover,different levels of corrugation are considered.The results indicate that solidificationfirst occurs around the con-tacts,followed by the area behind the contacts.It is also shown that deadflow zones exist in the sharp areas and such areas are prone to liquid solidification.After optimization,the solidification area attains its smallest value when a corrugation spacingλ=4.2 mm is considered.

Evaluation of Shell and Tube Heat Exchanger Performance by Using ZnO/Water Nanofluids

To examine and investigate the impact of nanofluid on heat exchanger performance,including the total heat transfer,the effect of friction factor,the average Nusselt number,and the thermal efficiency,the output heat transfers of a shell and tube heat exchanger using ZnO nanoparticles suspended in water has been conducted numerically.The governing equations were solved using finite volume techniques and CFD simulations with ANSYS/FLUENT Solver 2021.The nanoparticles volume fractions adopted are 0.2%and 0.35%that used in numerical computations under 200 to 1400 Reynolds numbers range.The increasing of temperature is approximately 13%from the bottom to the top of heat exchanger,while the maximum enhancement of Nusselt number is about 10%,19%for volume fractions 0.2%and 0.35%respectively.The elevated values of the friction factor at the volumetric ratios of 0.2%and 0.35%are 0.25%and 0.47%respectively.The findings demonstrate that the performance efficiency of shell and tube heat exchanger is enhanced due to the increase in Nusselt number.

Experiment Study on the Exhaust-Gas Heat Exchanger for Small and Medium-Sized Marine Diesel Engine

This paper aims to design a special exchanger to recover the exhaust gas heat of marine diesel engines used in small and medium-sized fishing vessels,which can then be used to heat water up to 55°C–85°C for membrane desalination devices to produce fresh water.A new exhaust-gas heat exchanger of fins and tube,with a reinforced heat transfer tube section,unequal spacing fins,a mixing zone between the fin groups and four routes tube bundle,was designed.Numerical simulations were also used to provide reference information for structural design.Experiments were carried out for exhaust gas waste heat recovery from a marine diesel engine in an engine test bench utilizing the heat exchanger.The experimental results show that the difference between heat absorption by water and heat reduction of exhaust gas is less than 6.5%.After the water flow rate was adjusted,the exhaust gas waste heat recovery efficiency was higher than 70%,and the exhaust-gas heat exchanger’s outlet water temperature was 55°C–85°C at different engine loads.This means that the heat recovery from the exhaust gas of a marine diesel engine meets the requirement to drive a membrane desalination device to produce fresh water for fishers working in small and medium-sized fishing vessels.

The Use of Models to Evaluate Corrosion Effects on Mild Steel Heat Exchanger in Water and Mono Ethanol Amine (MEA)

Heat exchanger is an important equipment used in process industries for cooling and heating purposes. Its design configuration which involves the flow of cold and hot fluids within the exchanger subjects it to corrosion attack. The article utilized the principle of mass and energy conservation in the development of weight and temperature models to study the effect of corrosion on mild steel coupon inside the exchanger containing water and Mono ethanol amine (MEA). The models developed were resolved analytically using Laplace Transform and simulated using Excel as simulation tool and data obtained from experiment in the laboratory to obtain profiles of weight loss and temperature as a function of time. The weight loss and performance of mild steel under various corrosive conditions were examined which indicates the effect of corrosion on the mild steel heat exchanger in water and MEA media. The result shows that water is more corrosive than MEA at higher temperatures and at lower temperatures of 35°C and 1 atm, MEA has inhibitive properties than water as indicated by the weight loss result with time. The comparative analysis between the results obtained from the model simulation and experimental results shows that the result obtained from the model is more reliable and demonstrated better performance characteristics as it clearly shows mild steel heat exchanger experiences more corrosive effect in water medium than MEA at higher temperatures. And at lower temperatures, MEA becomes more inhibitive and less corrosive than water. The model simulation results correlate with various literatures and hence, it is valid for future referencing.

Localized Theoretical Analysis of Thermal Performance of Individually Finned Heat Pipe Heat Exchanger for Air Conditioning with Freon R404A as Working Fluid

This work contributes to the improvement of energy-saving in air conditioning systems. The objective is to apply the thermal efficiency of heat exchangers for localized determination of the thermal performance of heat exchangers with individually finned heat pipes. The fundamental parameters used for performance analysis were the number of fins per heat pipe, the number of heat pipes, the inlet temperatures, and the flow rates of hot and cold fluids. The heat exchanger under analysis uses Freon 404A as a working fluid in an air conditioning system for cooling in the Evaporator and energy recovery in the Condenser. The theoretical model is localized and applied individually to the Evaporator, Condenser, and heat exchanger regions. The results obtained through the simulation are compared with experimental results that use a global approach for the heat exchanger. The thermal quantities obtained through the theoretical model in the mentioned regions are air velocity, Nusselt number, thermal effectiveness, heat transfer rate, and outlet temperature. The comparisons made with global experimental results are in excellent agreement, demonstrating that the localized theoretical approach developed is consistent and can be used as a comprehensive analysis tool for heat exchangers using heat pipes.

Localized Theoretical Analysis of Thermal Performance of Individually Finned Heat Pipe Heat Exchanger for Air Conditioning with Freon R404A as Working Fluid

This work contributes to the improvement of energy-saving in air conditioning systems. The objective is to apply the thermal efficiency of heat exchangers for localized determination of the thermal performance of heat exchangers with individually finned heat pipes. The fundamental parameters used for performance analysis were the number of fins per heat pipe, the number of heat pipes, the inlet temperatures, and the flow rates of hot and cold fluids. The heat exchanger under analysis uses Freon 404A as a working fluid in an air conditioning system for cooling in the Evaporator and energy recovery in the Condenser. The theoretical model is localized and applied individually to the Evaporator, Condenser, and heat exchanger regions. The results obtained through the simulation are compared with experimental results that use a global approach for the heat exchanger. The thermal quantities obtained through the theoretical model in the mentioned regions are air velocity, Nusselt number, thermal effectiveness, heat transfer rate, and outlet temperature. The comparisons made with global experimental results are in excellent agreement, demonstrating that the localized theoretical approach developed is consistent and can be used as a comprehensive analysis tool for heat exchangers using heat pipes.

A Comprehensive Review of the Influence of Heat Exchange Tubes on Hydrodynamic,Heat,and Mass Transfer in Bubble and Slurry Bubble

Bubble and slurry bubble column reactors(BCRs/SBCRs)are used for various chemical,biochemical,and petro-chemical applications.They have several operational and maintenance advantages,including excellent heat and mass transfer rates,simplicity,and low operating and maintenance cost.Typically,a catalyst is present in addition to biochemical processes where microorganisms are used to produce industrially valuable bio-products.Since most applications involve complicated gas-liquid,gas-liquid-solid,and exothermic processes,the BCR/SBCR must be equipped with heat-exchanging tubes to dissipate heat and control the reactor’s overall performance.In this review,past and very recent experimental and numerical investigations on such systems are critically dis-cussed.Furthermore,gaps to befilled and critical aspects still requiring investigation are identified.

Application of Technology of Additive Manufacturing in Radiators and Heat Exchangers

Radiators and heat exchangers play a key role in the long-term and stable operation of the equipment. The emergence of additive manufacturing technology has released the freedom of design, enabling many innovative structures of radiators and heat exchangers to be manufactured. The paper reviews the application of additive manufacturing in new radiators and heat exchangers. The technology of additive manufacturing boosts the development of new radiators and heat exchangers, which improves heat dissipation performance and heat exchange efficiency. This paper will provide a new idea and method for the development of radiators and heat exchangers via the application of additive manufacturing.

Performance comparison for oil-water heat transfer of circumferential overlap trisection helical baffle heat exchanger

The performance tests were conducted on oil–water heat transfer in circumferential overlap trisection helical baffle heat exchangers with incline angles of 12°, 16°, 20°, 24° and 28°, and compared with a segmental baffle heat exchanger. The results show that the shell side heat transfer coefficient h_o and pressure drop Δp_o both increase while the comprehensive index h_o/Δp_o decreases with the increase of the mass flow rate of all schemes. And the shell side heat transfer coefficient, pressure drop and the comprehensive index ho/Δpo decrease with the increase of the baffle incline angle at a certain mass flow rate. The average values of shell side heat transfer coefficient and the comprehensive index h_o/Δp_o of the 12° helical baffled scheme are above 50% higher than those of the segmental one correspondingly, while the pressure drop value is very close and the ratios of the average values are about 1.664 and 1.596, respectively. The shell-side Nusselt number Nu_o and the comprehensive index Nu_o·Eu_(zo)^(-1) increase with the increase of Reynolds number of the shell side axial in all schemes, and the results also demonstrate that the small incline angled helical scheme has better comprehensive performance.

Simulating the Turbulent Hydrothermal Behavior of Oil/MWCNT Nanofluid in a Solar Channel Heat Exchanger Equipped with Vortex Generators

Re-engineering the channel heat exchangers(CHEs)is the goal of many recent studies,due to their great importance in the scope of energy transport in various industrial and environmental fields.Changing the internal geometry of the CHEs by using extended surfaces,i.e.,VGs(vortex generators),is the most common technique to enhance the efficiency of heat exchangers.This work aims to develop a newdesign of solar collectors to improve the overall energy efficiency.The study presents a new channel design by introducing VGs.The FVM(finite volume method)was adopted as a numerical technique to solve the problem,with the use of Oil/MWCNT(oil/multi-walled carbon nano-tubes)nanofluid to raise the thermal conductivity of the flow field.The study is achieved for a Re number ranging from12×10^(3) to 27×10^(3),while the concentration(φ)of solid particles in the fluid(Oil)is set to 4%.The computational results showed that the hydrothermal characteristics depend strongly on the flow patterns with the presence of VGs within the CHE.Increasing the Oil/MWCNT rates with the presence of VGs generates negative turbulent velocities with high amounts,which promotes the good agitation of nanofluid particles,resulting in enhanced great transfer rates.

Optimization of a Heat Exchanger Using an ARM Core Intelligent Algorithm

In order to optimize heat transfer in a heat exchanger using an ARM(advanced RISC machine)core intelligent computer algorithm,a new type of controller has been designed.The whole control structure of the heat exchange unit has been conceived on the basis of seven functional modules,including data processing and output,human-computer interaction,alarm,and data communication.The main controller and communication controller have been used in a combined fashion and a new MCU(micro control unit)system scheme has been proposed accordingly.A fuzzy controller has been designed by using a fuzzy control algorithm,and a new mode of heat transfer for the heat exchanger has been implemented by combining the fuzzy controller and the PID(proportioning integral derivative)controller.Finally,the model has been applied to an actual heat exchange station to test and verify the performances of the new approach.

Heat Exchanger Network Retrofit for Optimization of Crude Distillation Unit Using Pinch Analysis

Crude distillation unit(CDU)is regarded as the main energy consumer in the entire refinery process.In this paper,the process simulation software and the energy management software are used to simulate the flowsheet and analyze the energy consumption,respectively.Stream data obtained from an existing CDU are applicable in the pinch analysis.To reduce the amount of cross-pinch heat transfer,three approaches of resequencing,repiping,and adding heat exchangers are adopted.Compared with the existing CDU,the results demonstrate that the inlet temperature of the furnace can be increased by 25.4℃,the amount of hot and cold utilities can be reduced by 15.1%and 19.6%,respectively.The economic evaluation indicates that the operating cost is saved by 8×106$/a,and the payback period is about 9 months.

Heat Exchanger Network Retrofit of Diesel Hydrotreating Unit Using Pinch Analysis

Diesel hydrotreating unit(DHT)is an integral part of the refinery,and its energy-saving optimization is of great significance to the enterprise.In this paper,process simulation software and energy management software are used to simulate the flowsheet and analyze the energy consumption,respectively.Stream data obtained from an existing DHT are applied in the pinch analysis for retrofitting the heat exchanger network(HEN)to achieve maximum energy utilization by using pinch analysis.Since DHT is constrained by pressure,the pressure factor is considered in the process of retrofitting.The results show that the amount of cross-pinch heat transfer is reduced,the inlet temperature of the furnace is increased by 55℃,and the amount of hot and cold utilities can be reduced by 70.25%and 50.16%,respectively.The economic evaluation indicates that the operating cost is saved by 4.39×10^(6)$/a,and the payback period is about 2 months.

Flexibility analysis and design of heat exchanger network for syngas-to-methanol process

The heat exchanger network(HEN)in a syngas-to-methanol process was designed and optimized based on pinch technology under stable operating conditions to balance the energy consumption and economic gain.In actual industrial processes,fluctuations in production inevitably affect the stable operation of HENs.A flexibility analysis of the HEN was carried out to minimize such disturbances using the downstream paths method.The results show that two-third of the downstream paths cannot meet flexibility requirements,indicating that the HEN does not have enough flexibility to accommodate the disturbances in actual production.A flexible HEN was then designed with the method of dividing and subsequent merging of streams,which led to 13.89%and 20.82%reductions in energy consumption and total cost,respectively.Owing to the sufficient area margin and additional alternative heat exchangers,the flexible HEN was able to resist interference and maintain production stability and safety,with the total cost increasing by just 4.08%.

Corrosion risk analysis of tube-and-shell heat exchangers and design of outlet temperature control system

This study deals with the high-risk shell-and-tube heat exchangers in the effluent system of hydrogenation reaction of the petrochemical industry.The process of hydroprocessing reactor effluent system is simulated in Aspen Plus to study the distribution of corrosive medium in the three phases of oil,gas and water.The least-squares method is utilized to calculate the ammonium salt crystallization temperature.Then,the heat exchanger with risk of ammonium salt crystal corrosion is identified.Dynamic mathematical modeling of the heat exchanger is established to determine the transfer function.A temperature control system with proportional integral derivative(PID)control of the heat exchanger outlet is designed,and fuzzy logic is used to implement self-tuning of PID parameters.After MATLAB simulation,the results show the control system can achieve rapid control of the heat exchanger outlet temperature.

Simulation of heat transfer performance using middle-deep coaxial borehole heat exchangers by FEFLOW

Due to its large heat transfer area and stable thermal performance,the middledeep coaxial borehole heat exchanger(CBHE)has become one of the emerging technologies to extract geothermal energy.In this paper,a numerical modeling on a three-dimensional unsteady heat transfer model of a CBHE was conducted by using software FEFLOW,in which the model simulation was compared with the other studies and was validated with experimental data.On this basis,a further simulation was done in respect of assessing the influencing factors of thermal extraction performance and thermal influence radius of the CBHE.The results show that the outlet temperature of the heat exchanger decreases rapidly at the initial stage,and then tended to be stable;and the thermal influence radius increases with the increase of borehole depth.The heat extraction rate of the borehole increases linearly with the geothermal gradient.Rock heat capacity has limited impact on the heat extraction rate,but has a great influence on the thermal influence radius of the CBHE.When there is groundwater flow in the reservoir,the increase of groundwater velocity will result in the rise of both outlet temperature and heat extraction rate.The heat affected zone extends along with the groundwater flow direction;and its influence radius is increasing along with flow velocity.In addition,the material of the inner pipe has a significant effect on the heat loss in the pipe,so it is recommended that the material with low thermal conductivity should be used if possible.

Experimental study on thermal resistance of fouling in heat exchangers of sewage source heat pumps

To investigate the formation of fouling in sewage heat exchangers,a model of thermal resistance with time is developed based on the experiments in a practical engineering site. And this model is asymptotic exponential function. According to the characteristic of sewage heat exchangers,the effective thermal resistance and effective coefficient of heat transmission during the formation of fouling are defined. A model for pressure loss of fouling of asymptotic distribution is presented based on the model of thermal resistance of fouling. And the maximum absolute margin of error of the fouling thermal resistance is smaller than the typical allowable error range. The maximum relative error of the heat transfer coefficient is 12% . These can meet the requirements of engineering. The results of experiments provide a basis for further study and application of swage heat exchangers.

Experimental Investigation of Two-Phase Flow Maldistribution in Plate Heat Exchangers

After conducting a critical survey of the different categories of existing heat exchangers,the results of several experiments about the behaviour of a two-phase current in an open channel are reported.The results confirm the complexity of the problems induced in heat exchangers by flow maldistribution,especially when two-phase flows are considered in multi-channel systems.It is shown that severe misalignment of heat exchangers can lead to a loss of economic performance of more than 25%.Improper distribution of fluid flow causes longer fluid coils to form,and the liquid cochlea can eventually occupy a large space,thereby reducing heat transfer and disrupting the considered biphasic system.The use of a small diameter distribution pipe with properly spaced outlet holes seems to be a promising approach to fix many of these issues.It is found that the current distribution in the channels,in addition to the header pressure distribution,also depends on factors such as the geometry and the initial flow regime in the header.