Heat Exchanger Arrangement Research Articles

Air Flow Analysis for Triply Periodic Minimal Surface Heat Exchangers

Due to the increasing popularity of additive manufacturing technologies, more varied and complex shapes of heat exchangers can be produced, that can be optimized to be more compact and efficient. In this paper a triply minimal periodic surface – gyroid structure is designed to study the applicability of such structures in air-to-air heat exchangers used in residential ventilation recuperation systems. Gyroid surface structures are useful to decrease overall heat exchanger size, pressure and increase heat transfer. Several geometry variations with different flow rate values were analysed to compare the efficiency of heat exchanger designs, as well as basic counterflow plate heat exchanger arrangement was analysed, to compare the gyroid designs to conventional methods. To calculate the pressure difference, temperature and heat transfer in each variation, SolidWorks Flow Simulation was used. The results showed that by using gyroid structures, heat exchanger energy transfer can be optimised for required back pressure and heat transfer, while reducing the overall dimensions, compared to conventional heat exchangers. By incorporating low cost, printed thermal recuperators, thermal efficiency of residential buildings can be improved. Suitable materials, manufacturing methods and application limitations are discussed.

Residential Micro-CHP system with integrated phase change material thermal energy storage

This paper presents an analysis and experimental investigation of the effect of integrating Phase Change Material (PCM) within a heat exchanger within a Micro Combined Heat and Power (Micro-CHP) system intended for residential applications. A commonly used Micro-CHP layout is replicated in a test rig to characterise the performance of two alternative heat exchanger arrangements. The first is a conventional arrangement where the exhaust gas produced by the prime mover is directed to an air-to-water heat exchanger to heat water and store it in a tank. In the second arrangement, PCM material is encapsulated within specially designed compartments in a heat exchanger to store part of the exhaust thermal energy from the prime mover while heating the water in the storage tank. The time needed to heat the water and discharge heat is compared for both cases, as well as the amount of thermal energy stored during the same operating period. The study also explored the potential to improve the designed unit by using different PCM materials. The test results show that adding 4.7 L capacity paraffin compartments within the heat exchanger extended the discharge time of the hot water by over 400 %, which reflects a marked improvement in the heat storage capacity of the system. This would result in a significant increase in the viable operating period of a CHP system. The one-dimensional analysis revealed that replacing the paraffin with ClimSel C58 PCM can reduce the charging time of the water tank by around 54 % improve the heat storage capacity by factor of 2.35 comparing to Paraffin. The proposed heat exchanger with encapsulated PCM has a potential in other applications such as storage of excess renewable energy or integration with heat pumps to improve matching of supply and demand and thus flexibility of an energy system with integrated intermittent renewables.

Thermal Management for a Stadium Power Supply Container Using a Rack-Level Air Cooling Strategy

This study investigates the airflow and thermal management of a compact electric energy storage system by using computational fluid dynamic (CFD) simulation. A porous medium model for predicting the flow resistance performance of the battery modules in a battery cabinet is developed. By studying the influence of rack shapes, the effects of heat exchanger arrangements and other parameters on the airflow and battery thermal distribution are analyzed. When applying a larger bottom air channel, the inlet flow uniformity of each battery cabin in the cabinet increases by 5%. Meanwhile, temperature standard deviation decreases by 0.18 while raising the flow rate from 3 m/s to 8 m/s, indicating better temperature uniformity in the battery cabin. When the charge–discharge ratio reaches 0.5 C, the temperature deviation of the entire cabinet significantly increases, reaching 8 K. Furthermore, a rack-level thermal management scheme is proposed to effectively reduce the thermal deviation of the container electric energy storage system and improve the overall temperature uniformity. Results reveal that the rack-level thermal management of the wavy cabinet in the electric storage container can effectively improve the thermal uniformity of the distributed battery cabin, and the overall thermal deviation is controlled within 1.0 K.

Research and evaluation of the arrangement of heat exchangers in electric vehicle thermal management systems for CO2 refrigerant

The application of transcritical CO2 cycle in the thermal management system of electric vehicles has become increasingly prevalent, but the existing thermal management system architecture has not been optimized to specifically enhance the performance of CO2 refrigerant. This paper analyzes the impact of various heat exchanger arrangements on CO2 thermal management system and evaluates system configurations based on a new performance index, cycle coefficient of performance. The effects of air temperature, ambient temperature, and heat load on system performance are conducted with a high precision model. The chiller is connected in parallel-series with indoor heat exchangers, resulting in a maximum coefficient of performance improvement of 27.89% at an indoor air inlet temperature of 10 °C, and a maximum coefficient of performance improvement of 21.69% at an ambient temperature of 5 °C, under simultaneous heating conditions. The radiator is placed on the windward of gas cooler, leading to a maximum coefficient of performance increase of 4.85% in heating mode, but a maximum coefficient of performance decrease of 9.84% in cooling mode. The evaluation of these configurations across different operating cycles reveals that the parallel-series connection is well-suited for the new European driving cycle, showing an 18.4% improvement in cycle coefficient of performance compared to the series-parallel connection. The windward arrangement of radiator proves effective for highway fuel economy test cycle in winter and the new European driving cycle in summer. This study provides effective instruction for configuration design and evaluation of transcritical CO2 vehicle thermal management systems.

Performance evaluation of heater and recuperator in Brayton cycles for power and energy storage

The performance of heat exchangers matters in the Brayton cycles for power and energy storage systems. However, the understanding of how heat exchanger performances affect cycle efficiency is still highly inadequate. The existing methods, including the performance evaluation criteria (PEC) and exergy/entropy analysis, are insufficient in evaluating the contributions of heat transfer enhancement or flow resistance reduction to the cycle performance. Also, the coupling analysis only provides the solutions for the cases under specific operation parameters of a specific cycle layout, in addition to their high computational cost and technical complexity. In the present work, a novel evaluation method, a performance recovery coefficient (PRC), was proposed to evaluate the effect of heat exchanger performances on the cycle efficiency simply using the component-scale parameters, avoiding complex coupling analysis. The applications of PRC in both heaters and recuperators were demonstrated, under different layouts, parameters and working fluids, of Brayton cycles for power generation, and integrated power generation and storage. Finally, it is shown that the PRC can facilitate the type selection and arrangement of heat exchangers of both direct and indirect heating, and deliver a cycle efficiency enhancement by 1.4 and 0.4 percentage points, respectively. Overall, the present method provides clear insights into how the interplay between heat transfer and flow resistance in heat exchangers contributes to cycle performance.

Analysis of gyroid heat exchangers for superconducting electric motors

In this study, gyroid structured heat exchangers are critically analysed in a counterflow arrangement. These are to be analysed to measure their performance in the case of superconducting electric motors using cryogenic fluids at low temperatures. Gyroid structures are useful in heat exchanger design, as they offer more varied and complex geometries that can optimise heat transfer to be more efficient, compared to traditional heat exchanger designs. The manufacture of these heat exchangers is made possible using additive manufacturing, as the complex shape of these structures cannot be made through traditional methods. Simulation analysis results of the gyroid structures are compared to a basic tubular counterflow heat exchanger arrangement, which can be made from more traditional methods. Physical printing of the model is also demonstrated to show its practicality. The comparison of results elucidated the overall effectiveness of the gyroid structures, and how geometries can optimise overall energy transfer, considering heat transfer from fluids, and pressure loss from fluid flow.

Research on dimensionless structure size of coil heat exchanger in heat discharging process of molten salt single tank heat storage system

• Optimum dimensionless size of coil heat exchanger was studied by simulation. • The optimal size of heat exchanger appears under the combined action of vortex and molten salt flow rate. • When the dimensionless pitch L/d =4, the heat exchanger has the best heat discharging performance. • When the dimensionless pitch is the best, the optimal dimensionless diameter is 0.25. There has been an increasing attention on single-tank thermal energy storage, attracted by the low cost, high efficiency and compactness in the operation. However, the most researches on single-tank thermal energy storage focused on the way of heat discharging and the arrangement of heat exchangers. Few studies on the dimensionless size of heat exchanger, which is important for the design of single-tank thermal energy storage, were carried out. In order to obtain higher heat exchange efficiency and design criteria of coil heat exchanger, the optimal dimensionless size of heat exchanger is studied by numerical simulation. The results show that both the dimensionless pitch and the dimensionless pipe diameter of the coil heat exchanger have a great influence on the heat discharging performance when the air is used as the heating medium and the molten salt is used as the heat storage medium. With the change of dimensionless pitch, the heat discharging performance and the flow field of molten salt are affected. When the dimensionless pitch L / d = 4, the heat discharging power and heat release are the highest. At this time, the temperature and flow field of molten salt are evenly distributed, and no temperature stratification and vortex are formed. When the dimensionless pipe diameter is changed on the premise of the optimal dimensionless pitch, the heat discharging power increases first and then decreases with the increase of dimensionless pipe diameter. When the dimensionless pipe diameter d / a =0.25, the molten salt flow rate in the single tank is relatively large and no vortex hindering heat transfer, and the heat discharging performance is the best. Therefore, under the joint action of molten salt velocity and vortex, the optimal dimensionless pitch and pipe diameter appear. The research results provide a theoretical basis and an example for the design of single tank energy storage system.

Impulse Air Jet Action on the Convective Heat Exchange Tubular Surfaces in Boilers

Calculation and experimental investigations were carried out to determine the parameters of the impulse air jet created by the pneumatic generator of the air-impact system of the cleaning of tubular heat exchangers in boilers. Two configurations (lengthwise and checkerboard) of the arrangement of tubular heat exchangers located at distances from 1.0 m to 2.5 m of nozzle exit were experimentally investigated and the forces acting on them were determined. Numerical modeling of the impulse jet impact on heat exchange tubes was carried out. It was shown that an increase in the pressure of the generated impulse jet to 2.35 MPa makes it possible to significantly increase the acting force from 78 N to 1881 N at a large distance from the exhaust nozzle. The results obtained can be used in the development of specific systems for air impact cleaning systems of boiler units with other sizes and configurations of the heat exchange tubes.

Technical Performance Optimization of a Novel Geothermal Hybrid Power Generation System

Geothermal Aided Power Generation (GAPG) technology is a geothermal hybrid power system that geothermal energy has been integrated into the fossil fired plant to preheat the feedwater, and displace the extraction steam of fossil fired plant. In such a power system, the heat exchange process between extraction steam and geo-fluid occurs in a heat exchange between. When the geo-fluid in the heat exchanger quench to lower temperature for heat transfer purpose, silica scaling would occur in the heat exchanger system. The performance of the GAPG plant would be influenced by the configuration of the heat exchanger and silica scaling in the heat exchanger. For a GAPG plant, it has two possible configurations for a heat exchanger system: series arrangement and parallel arrangement. The different configuration also impacts on the technical performance of the GAPG plant. The silica scaling in the heat exchanger system would harm the performance of the GAPG plant. In this study, a GAPG power system from a 300 MW power plant is used as a case study to understand the impact of displacement selections and heat exchanger arrangement on the performance of the GAPG plant. It was found that there is no silica scaling occurring in heat exchangers system if geo-fluid is used to displace to high-grade extraction steam only. Furthermore, the Parallel arrangement is better than the Series arrangement in terms of the additional power output. Moreover, the GAPG plant has protentional to reduce carbon dioxide emissions by 13%.

Study on thermal performances of a horizontal ground heat exchanger geothermal system with different configurations and arrangements

Horizontal ground heat exchanger (HGHE) is a low-cost shallow geothermal exploitation method compared with vertical ones, but it needs more land area. Optimizing geometrical configurations and arrangements of ground heat exchangers is desirable to enhance heat exchange per unit land area. However, a comprehensive study on different HGHE configurations and arrangements considering atmosphere-soil-HGHE interaction is still inadequate. To this end, thermal performances of four configurations, including slinky, spiral, multi-tube with serial connection and tiled tubes, are compared based on a 3D numerical model for HGHE considering atmosphere conditions variation and humidity migration. Effects of main geometrical parameters on HGHE performance and economical efficiency are investigated for these four configurations. Finally, different tube arrangements of multi-tube HGHE are designed and their thermal performances are analyzed. Results indicated that longer HGHE tube length has better thermal performance but lower economical efficiency, thus being not advisable for the HGHE design. Among these four configurations, multi-tube with serial connection shows the best thermal performance. Increasing the tube spacing is beneficial for reducing the tube mutual interference and enhance the heat exchange per unit land area, which is recommendable. Results are expected to provide meaningful suggestions for the HGHE design.

Optimization of a Tube Heat Exchanger Arrangements Using Simulated Annealing, Finite-Volume, and Blocked-Off Methods

Optimization of a Tube Heat Exchanger Arrangements Using Simulated Annealing, Finite-Volume, and Blocked-Off Methods

Numerical Demonstration of an Unconventional EGS Arrangement

A new EGS arrangement, Robust EGS (REGS), is studied for its potential benefits for wide-spread applications for clean, carbon-free, electrical energy generation. Numerical simulations are carried out to prove the key benefit of REGS in a simple, but effective, geologic heat exchanger arrangement with large, stabilized fracture aperture and controlled flow zones. The numerical model results show the estimated potential energy capacity and the converted value to electrical energy generation over a 30-year operation time period for two simple REGS arrangements. The results may assist EGS investors and drilling companies in deciding whether the investment and operation can be made profitable for the wide-scale application of REGS for green energy generation.

Comparison of Heat Transfer rates for Water and Ethylene Glycol mixtures for Diesel engine exhaust gas heat recovery using Shell and Tube Heat Exchanger.

Most of the researchers have claimed that high compression engines (diesel engines) are performing slightly above of 1/3rd of their potential and remaining heat energy is wasted in the form of exhaust gas. Efforts are going on to improve the design of these engines and investigations are being carried out to recover this waste energy from exhaust gases and utilize for different applications.In the present work, initially water is used as a heat exchange medium for three different loads on diesel engine viz., 50%, 60% and 70%, which extracts heat energy to evaluate the exhaust heat attainable from exhaust gases of the engine. The exhaust gas is passed through the tube side of the heat exchanger which is obtained from an exhaust manifold of a four stroke single cylinder diesel engine. Water is passed through the shell side of the shell and tube heat exchanger. Later this work is repeated for two different cooling medium i.e. water-ethylene glycol mixtures with 25% and 50%. The results are compared for 60% engine load conditions. The counter flow type heat exchanger arrangement is considered for the analysis. The temperatures were recorded for hot gases and cold medium at inlet and outlet points of the shell side and tube side flow. Heat calculations are carried out for each combination and detailed in the result–discussion and conclusion chapter. The objective of this work is to assess the exhaust gas heat recovery capacity using the ethylene glycol-water mixture and come out with a mixture for higher heat recovery capacity. This work is undertaken with segmental baffle heat exchanger of zero degree inclination. Also the work is repeated for inclined baffle heat exchangers of 10-degree and 20-degree baffle inclination to assess the effectiveness of liquid in recovering the heat from exhaust gases. It is observed that the water and Ethylene glycol mixtures have performed satisfactorily in all three baffle setups showing only 1.5% - 2.0% less heat recovery when compared with only water.

Investigation on heat exchanger arrangement in solar enhanced natural draft dry cooling towers under various crosswind conditions

Solar enhanced natural draft dry cooling tower (SENDDCT) is a novel heat rejection device for thermal power plant, which uses solar energy to reheat the air after the heat exchanger and therefore improves the ventilation of the tower for performance enhancement. This paper develops 3-D models to compare the effects of circular/sawtooth arrangements of heat exchanger on cooling performance of a 140 m high SENDDCT. The result shows that sawtooth arrangement can improve the ventilation and heat dissipation rate of SENDDCTs. Under no crosswind condition, the flow field distributions of sawtooth and circular arrangements are similar in the tower. The ventilation and heat dissipation rate of sawtooth arrangement increases by 34.0 % and 46.8 % respectively when compared with circular arrangement under no crosswind condition. Under crosswind condition, the flow field of sawtooth arrangement is less affected by crosswind than that of circular arrangement. The ventilation rate and heat dissipation rate of sawtooth arrangement increases by 38.5 % and 65.0 % respectively when compared with circular arrangement at crosswind speed of 3 m/s. This study verifies that the sawtooth arrangement can weaken the crosswind effect and improve the cooling performance of SENDDCT and provides guidance for the optimal arrangement of heat exchanger for the SENDDCT.

Manufacturing and Characterization of Tube-Filled ZA27 Metal Foam Heat Exchangers

This study investigates the heat transfer performance of a novel ZA27 metal foam heat exchanger. An open-celled metal foam is combined with a thin-walled copper tube in a single-step casting process. The heat transfer between two separated water streams flowing through the copper tube and foam, respectively, is measured and compared to an equivalent shell tube heat exchanger arrangement. Heat transfer enhancement of up to 71% and a heat transfer rate exceeding 30 kW are observed and attributed to the increased surface area of the metallic foam. However, overall performance was limited by the inefficient heat transfer between the internal mass stream and the copper tube.

Pumping Power & Flow rate comparison of Double Pipe Corrugated Heat Exchanger (DPCHE) against Smooth Double Pipe Heat Exchanger (SPHE)

Heat Exchangers are indispensable in the development of various industrial and daily use systems. However, the effectiveness of the heat exchangers depends on the geometry, working fluids, type, and arrangement of the flow-through heat exchangers. A lot of experimentalists are working around the globe to find out the methods on how to enhance the productivity of different fluids with varied properties.

On the acoustic effects of sonic crystals in heat exchanger arrangements

Heat exchangers can be found in a large number of technical systems and installations. They are usually operated in combination with other machines, such as axial fans, in order to remove or supply heat to a system. The heat exchanger can influence the existing flow field and thus lead to increased noise emission from fans located downstream of the heat exchanger. This can be observed, for example, in air conditioning units in which axial fans operate in combination with heat exchangers. Even though this mechanism is known, it is not yet understood how the heat exchanger affects the sound propagation of the sound produced by the downstream machine. For example, the heat exchanger may lead to a change in directional characteristics or specific frequencies may be attenuated. In order to better understand the interaction of the heat exchanger with the sound field, sound power measurements were carried out on various heat exchangers and the sound propagation was simulated numerically. It was shown that the sound attenuation due to the interaction with the periodic tube array is detectable in heat exchangers and that this leads to a sound reduction at the Bragg frequency. Based on its filling factor, the heat exchanger can reduce the sound propagation in certain frequency bands by up to 10 dB if the geometrirical properties are selected suitably. The simulations of a single unit cell confirm in very good agreement with the experimental results. This allows the conclusion that the approach presented in this paper is a cost-effective way to model acoustic effects of heat exchangers. Furthermore, sound attenuation effects by the heat exchanger were caused by thermoviscous effects on the cooling fins and dimensions of the heat exchanger housing.

Numerical investigation of molten salt/SiO2 nano-fluid in the solar power plant cycle and examining different arrangements of shell and tube heat exchangers and plate heat exchangers in these cycles

BackgroundSolar towers use heliostat to direct a lot of sunlight into a receiver. When concentrated solar radiation is converted to heat, it can drive a steam turbine connected to a power generator, which generates electricity. The purpose of this research is to design and analysis of a solar power plant in the climatic condition of Jeddah, Saudi Arabia. MethodBoth TRANSYS and THERMO FLEX software are applied for such purpose. The intended power plant is composed of two sections of a solar cycle with molten salt as working fluid and a Rankine cycle with working fluid of water for power generation. COMSOL software is applied to simulate the preheater heat exchangers. ResultsThe results of this study indicated that the solar power plant generates the most electricity during June and July. The efficiency during these two months is 25% for molten salt nanofluid and 24% for molten salt. In addition, the use of molten salt nanofluid can improve the heat transfer in the solar receiver and produce more electricity in the power plant compared to the use of molten salt. Moreover, the use of two preheaters instead of one increases the efficiency of the cycle by up to 3%.

Bed-to-tube heat transfer characteristics with an immersed horizontal tube in the pressurized fluidized bed at high temperature

High-temperature and high-pressure conditions have great effects on the heat transfer characteristics of the immersed horizontal tube and understanding them will provide an industrial reference for the arrangement and optimization of heat exchanger in the pressurized fluidized bed furnace. In this study, the pressurized fluidized bed apparatus was developed to investigate the effects of factors such as pressure, temperature, particle size and gas velocity on the local and average heat transfer coefficients of the immersed horizontal tube. The experimental results showed the improved heat transfer at elevated pressure and high temperature. When the bed temperature increased from 400 °C to 800 °C, the proportion of the radiative heat transfer increased significantly, but it did not exceed 15%. The maximum heat transfer coefficients in the process of increasing the fluidization number were also measured in this study and fit well with the prediction results of the Shah model. The distribution of circumferential local heat transfer coefficients showed differences at low fluidization numbers and high fluidization numbers. The model proposed for the immersed horizontal tubes in the pressurized fluidized bed predicted the experimental data points from this study and other different sources well with the absolute average deviation of 11.86%.

Unisim Based Simulation and Analysis of Crude Oil Distillation

Crude distillation is the process of separating the hydrocarbons in crude oil based on their boiling point. Though refining process consists of a wide variety of units the major part is done in Crude Distillation Unit (CDU). In this study an attempt is made to make a train of heat integration network for the crude distillation process. Steady state simulations of cases with different arrangement of heat exchangers were studied in this work. Since the cost of energy has increased dramatically in last year’s, the ability to optimize the use of resources and in particular of energy is becoming an extremely important skill for chemical engineers. Steady state simulation and dynamic simulation of crude plant with optimized heat exchanger design were then performed using Unisim software.