Heat Exchanger Module Research Articles

Experimental study on frost growth patterns and surface wettability effects of precooler module

A thorough understanding of frosting and frost layer growth mechanisms inside the precooler of a hypersonic precooled engine is of crucial importance for controlling the deterioration of heat transfer and pressure loss caused by frosting, and ensuring the normal operation of the engine. In this study, ultra-fine thermocouples were used to measure temperature variations longitudinally during the frosting process of the precooler module. Combined with optical images, an investigation was conducted into the frost layer growth patterns of precooler heat exchange modules and the influence of surface wettability. The research results indicate that there are two different frosting patterns in the precooler: under low Reynolds numbers (≤1500), the pattern is CRT, while under high Reynolds numbers (≥2000), the pattern is ALT. Frosting at Re ≤1500 may cause serious deformation of the precooler tubes. The collapse phenomenon caused by the instability of the frost layer structure reduces the pressure loss coefficient relative to the local maximum by 4 % to 7 %. The higher the incoming Reynolds number, the later the collapse occurs. When Re is too low, collapse will not occur. The surface wetting characteristics reduce the pressure loss coefficient by 13.3 % to 24.2 % in the local range of Reynolds numbers from 1500 to 2800, and cause the pressure loss coefficient curve to rotate clockwise as a whole, enhancing heat transfer to some extent. Last but not least, the normal distribution of surface temperature cooling rates and the functionalization of axial temperature gradients of the tube indicate the possibility of a rapid prediction method for three-dimensional frosting under complex engineering conditions in precooler.

Energy transfer and conversion in the Allam cycle with a multi-stream heat exchanger

The Allam cycle is renowned for its high efficiency and low emissions in power generation, utilizing supercritical carbon dioxide as the working fluid. The regenerator, one of the key heat exchangers, plays a crucial role in the system. However, modeling the regenerator is challenging due to the presence of multiple pinch points. This study proposes a regenerator model that employs three multi-stream heat exchanger modules in Aspen Plus. A thermodynamic and economic analysis of the system was conducted and compared with a conventional system utilizing the two multi-stream heat exchanger modules. Simulation results show that the combustion chamber has the highest exergy loss in the system, accounting for 46.9 % of the total exergy loss. The turbine is identified as the most capital-intensive component, representing 44.9 % of the total equipment investment. Furthermore, a sensitivity analysis was conducted on key parameters. The results indicate that under certain operating conditions, the heat provided by the air separation unit is insufficient to reduce the temperature difference at the hot outlet of the regenerator. Compared to the conventional Allam cycle system using the 2R model, the 2R model predicts deviations of up to 28.9 %. This proposed model provides a new approach for the efficient allocation of energy utilization in the multi-stream heat exchange process within the Allam cycle system.

Design of Modular Test Facility for Particle/sCO2 Heat Exchanger Evaluation

Heliogen has designed a 1.3 MW particle and supercritical carbon dioxide (sCO2) test loop to retire technical and manufacturing risks. The data from this facility will be used to validate near commercial-scale particle heat exchanger modules. The heat exchanger is scaled to capture all features of the full-scale modules. Testing will be conducted with CARBOBEAD HSP 16/30, a larger particle size than other recent testing. The system was designed to ASME codes with the constraint that sCO2 piping and other major components are stainless steels.

A study on flow distribution characteristics of heat exchanger module integration scheme for aircraft environmental control system based on CFD

With the rapid development of the civil aviation industry, the performance requirements of the environmental control system for domestic commercial large aircraft are gradually improved, and the ram air inlet heat exchanger system is its main component. Generally speaking, a ram air heat exchanger system mainly includes an air conditioning system heat exchanger, air preparation system heat exchanger, and auxiliary cooling system heat exchanger. The integration mode of the heat exchanger will directly affect the flow and flow distribution characteristics of the ram air heat exchanger system. This paper develops three integration schemes referring to the integration mode of heat exchangers in Boeing 787 and Airbus 350 aircraft. Based on Fluent software, the calculation and simulation of three integrated scheme models under the seven working conditions of taking off, climbing, cruising, descent, hovering, emergency, and landing during flight were carried out, and the flow distribution and flow resistance values of different schemes were obtained, which were compared to meet the heat transfer requirements.

Hierarchical Deployment of Vortex Generators for Wake Management in Finned-Tube Heat Exchanger

While developing thermal management systems, volumetric compactness of the heat exchange module is a critical design factor. This three-dimensional computational analysis seeks to boost the thermal compactness of fin-and-tube heat exchangers by employing winglet-type vortex generators. Due to the fact that the thermo-hydraulic performance of vortex generators in such thermal systems is determined by three distinct design parameters, namely the attack angle, spatial location, and geometric aspect ratio, a concurrent parametric analysis of all three design parameters is conducted to gain a thorough understanding. In addition, regression analysis is applied to develop functional correlations that can predict the enhanced thermo-hydraulic performance of the heat exchangers. The improvements in wake-affected heat transfer brought on by the modifications are also specifically explored, along with other aspects of the augmentation mechanism. The highest thermal augmentation over the wake-affected fin is seen as 120%. Based on a thermo-hydraulic tradeoff, the friction factor increases exponentially with the attack angle, and the rate of increase is lowest for 15–30 degree range of attack angle and highest for 45–60 degree range. Certainly, there are multiple locations where winglets can be erected, and heat transfer enhancement by each potential location incurs linearized increase in the friction factor.

Latent heat thermal energy storage solution for CSPs: Integration of PCM heat exchangers

In the last few decades, alternate and renewable energy harvesting techniques, such as Concentrated Solar Power (CSP), have attracted attention as a unique source of electricity. However, the intermittent nature of solar energy results in discontinuous electricity generation. Thus, the integration of a Latent Heat based Thermal Energy Storage (LHTES) system will help in managing this issue. This numerical study explores the heat storage and discharge abilities of Phase Change Material (PCM) to design an efficient energy storage system. In this study, a 2D novel geometrical model is introduced to enhance the performance of PCM based heat exchanger module. Finite Volume Method (FVM) has been used to simulate the complex phase change problem via ANSYS Fluent solver. The double pipe heat exchanger with concentric cylinders is considered as the base case and multiple design modifications with augmented heat transfer areas have been provided. Comparison of different configurations by varying geometrical parameters with base case is carried out. The improvement in the rate of phase change is observed as the base case tube is replaced by semi-circular tubes in the system. The reduction in sensible heat storage is large during initial stages of charging, a reduction is observed as 46%, 43.5% and 48.9% respectively for all three cases. The time taken to achieve a maximum storage and discharge effectiveness of 82%, 85% respectively is less for novel configurations as compared to base case. It is observed that both novel configurations can be useful to store and release faster which can be used in meeting the energy demand on time.

Integration of winglet type vortex generators in finned-tube heat exchangers for a sizeable capacity augmentation

Compact size of the heat exchange module is an important design consideration in majority of the thermal management systems. Using winglet type vortex generators, a sizeable improvement in the compactness of a widely used finned-tube array is attempted through this study. Since the degree of thermal augmentation changes with the generators’ position, around the tubes, this 3D comprehensive computational investigation aims to develop phenomenological correlations for the positional optimization, which are applicable over a wide range of operating conditions. Besides, this article is dedicated to understanding different aspects of the augmentation mechanism, including the tube-wake management and the performance improvement caused by the best design(s). Based on a parametric investigation, designs that are best suited for obtaining a sizeable performance augmentation of the system are identified. Furthermore, a critical assessment of the best designs is carried out to evaluate their impact on the heat transfer from wake-affected surfaces, both fins and tubes. It is encouraging to observe that the wake-affected surfaces also experience sizeable thermal augmentation, which increases further with the Reynolds number. While the total fin surface experiences a highest Colburn j-factor augmentation of 53.6%, the wake-affected fin undergoes 205.1% rise. An evident manifestation of the augmented Colburn j-factor is the reformed temperature distribution, which bears lower values all over the fins.

Numerical and Experimental Studies of the Plate Heat Exchanger Module of the Small-Sized Gas Turbine Engine with Heat Recovery

Numerical and Experimental Studies of the Plate Heat Exchanger Module of the Small-Sized Gas Turbine Engine with Heat Recovery

Heat transfer and pressure drop characteristics of the silicone-based plate heat exchanger

The paper presents an experimental investigation of a silicone based heat exchanger, with passive heat transfer intensification by means of surface enhancement. The main objective of this paper was to experimentally investigate the performance of a heat exchanger module with the enhanced surface. Heat transfer in the test section has been examined and described with precise measurements of thermal and flow conditions. Reported tests were conducted under steady-state conditions for single-phase liquid cooling. Proposed surface modification increases heat flux by over 60%. Gathered data presented, along with analytical solutions and numerical simulation allow the rational design of heat transfer devices.

Theoretical analysis of thermoelectric module

A thermoelectric generator was used to recover waste heat from a heat source, such as engine exhaust. The key elements of the thermoelectric generator are heat exchanger and thermoelectric module. Thermoelectric modules convert heat energy to electrical energy using the Seebeck effect. A temperature difference between the hot and cold sides of the thermoelectric module is required to generate electric power. A theoretical model was developed to predict thermoelectric current, voltage, and power output. A bismuth Telluride thermoelectric module was used for analysis. It was observed that the thermoelectric voltage increased with the external load resistance, and the thermoelectric power output increased at a certain load resistance and then decreased. Under the match load condition, the maximum thermoelectric power output was obtained.

COMPARATIVE ANALYSIS OF EXERGETIC LOSSES IN HEAT RECOVERIES OF GLASS FURNACES

The paper presents the results of a comparative analysis of the exergy losses of heat recovery units of various types included in the waste gas heat recovery systems of glass melting furnaces. Based on the principles of universality and additivity of exergy characteristics, as well as design features of heat recoveries, a comprehensive methodology for studying exergy losses in heat recoveries has been developed. With the help of the developed technique, exergy losses in hot water and hot air heat recoveries, as well as in individual heat exchanger modules, were calculated. A comparative analysis of exergy losses and technological features of heat recovery units included in various schemes for the utilization of waste gases from glass melting furnaces has been carried out. For water-heating heat recoveries, the value of energy losses is less than the value of losses for air-heating heat recoveries. When using water-heating heat recovery units in heat recovery schemes, the coefficient of heat using of the furnace fuel increases, on average, by 20%. Despite the higher level of exergy losses in hot air heat recoveries, taking into account a number of important technological factors determined their competitiveness in heat recovery technologies of glass melting furnaces. At the same time, the heat utilization factor of the furnace fuel increases, on average, by 12.5%.

Improving the efficiency of drying Eisenia Fetida by using a technique with induced heat and mass transfer

This paper substantiates the need to rationalize the drying process of such a vermitechnology object as Eisenia Fetida worms to utilize them as feed for industrial animal husbandry and poultry farming. This will contribute to improving the energy efficiency of vermitechnology application in the production of agricultural products. A technique of drying with the effect of induced heat and mass transfer has been adapted for raw materials with a low amount of dry substances, which is a homogenate of worms. Two adaptation techniques are proposed: drying the homogenate in a heat and mass exchange module with artificially created obturators; drying a mixture of homogenate with grain bran with the spontaneous formation of obturators from raw materials. Studies of various homogenate drying techniques have established that the longest duration of dehydration is achieved by convective drying technique. This is 1.2 times larger compared to the conductive technique and 2 and 3 times larger than drying with the effect of induced heat and mass transfer depending on the technique of obturator formation. It has been established that the final moisture content of dried products is the smallest for techniques involving the effect of induced heat and mass transfer. It is in 2...3 times less compared to convective and conductive techniques. Drying with the effect of induced heat and mass transfer of mixtures with the following mass ratio of the homogenate to grain bran was investigated: 1:1; 2:1; 3:1. It was established that for a sample with a ratio of 3:1, the nature of the kinetics of drying is different from the typical kinetics for the effect of induced heat and mass transfer. The consequence is an increase in the duration of dehydration compared to samples of 1:1 and 2:1 by 1.3 times. The results can be used in agriculture, namely, industrial animal husbandry, poultry farming, and vermitechnology

Energy and exergy analysis of a novel direct-expansion ice thermal storage system based on three-fluid heat exchanger module

Direct-expansion ice thermal storage (DX-ITS) system can overcome the mismatch between cold energy supply and demand, and also exhibit the characteristics of high energy efficiency, simple pipeline and minimal installation space. However, existing DX-ITS failed to achieve simultaneous high-efficiency heat transfer in the processes of charging and discharging, thereby limiting its widespread use. This study developed a novel DX-ITS system based on three-fluid heat exchanger modules employing micro heat pipe arrays to address the proceeding issue. Temperature distribution, pressure, charging and discharging power, energy efficiency ratio, exergy efficiency and ice packing factor during the charging and discharging processes at different compressor speeds, cooling-air temperature and flow rates were experimentally studied. Results demonstrated that maximum charging power, energy efficiency ratio, exergy efficiency, ice packing factor and discharging power of proposed system using a 4 HP compressor under experimental conditions reached 5.71 kW, 2.31, 11.12 %, 82.1 % and 4.99 kW, respectively. Moreover, cooling-air temperature had a more significant effect on system performance compared with cooling-air flow rate and compressor speed. The 11.7 %, 25.9 %, 24.3 %, and 20.6 % reductions in charging power, energy efficiency ratio, exergy efficiency, and ice packing factor were observed with an increase of cooling-air temperature from 18 °C to 35.5 °C.

Deformation characteristics and performance evolution of superalloy capillary drawn by electrically assisted microforming

Thin-walled superalloy capillaries are considered the core components of the heat exchanger in the hypersonic vehicle. To achieve the precise and efficient fabrication of capillaries, this study proposes an electrically assisted (EA) microforming process and investigates the deformation characteristics and performance evolution of capillaries under electric current. Experimental results show the EA drawing at 600 °C enhances the grain coordinated deformation capacity and dislocation recovery, while the ultrafast complete recrystallization and gradient grain microstructure are achieved by the EA annealing above 800 °C for 15 s. The microstructural evolution improves ductility and avoids macro defects, which is related to the reduction of activation energy of dislocation and grain boundary motion under the electroplastic mechanisms. In addition, the inhibition of the electric current on the increase in wall thickness is attributed to the increase in friction coefficient and the shedding of the oxide layer, while the electric current improves surface quality by forming ultrafine grains, oxidizing peaks, and healing troughs. Compared with the conventional manufactured capillaries, the surface quality, tensile strength, and elongation of the EA manufactured capillaries with the size of φ0.9 mm × 58 μm are increased by 129.0%, 31.1%, and 9.4%, respectively. A heat exchanger module integrated by the EA manufactured capillaries can cool the 25 m/s airflow from 1000 to 672 °C within 1 ms.

Single-Phase Dielectric Fluid Thermal Management for Power-Dense Automotive Power Electronics

This article describes the design and performance of a dielectric fluid cooling concept for automotive power electronics. The concept combines a low-thermal-resistance package (which eliminates metalized ceramic substrates) with a high-performance convective cooling strategy (slot jets impinging on finned surfaces). Modeling was first used to design the cooling system to maximize thermal performance and minimize pumping power. A prototype was then fabricated, and experiments were conducted to validate the model predictions using three fluids at various fluid flow rates (16.7 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /s [1 L/min] to 68.3 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /s [4.1 L/min]) and inlet temperatures (30 °C and 70 °C). The final design was compact (120-cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> total volume, including heat exchanger and conceptual power modules) and cooled 12 devices (e.g., silicon carbide [SiC]). The validated model was then used to predict the junction-to-fluid thermal resistance and pumping power for various conditions, including −40 °C fluid temperature. The results predict thermal resistance values as low as 19 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ·K/W is possible using the dielectric fluid cooling approach. The dielectric fluid cooling system is predicted to provide thermal resistance and pumping power values that are approximately 56% and 90% lower, respectively, compared to an automotive power electronics cooling system. Moreover, the dielectric fluids can be used for direct cooling of the bus bars, which can be an effective capacitor and gate driver cooling strategy and enable the use of new driveline fluids tailored for this application.

Development of an Air-Recirculated Ventilation System for a Piglet House, Part 2: Determination of the Optimal Module Combination Using the Numerical Model

As the pig industry develops rapidly, various problems are increasing both inside and outside pig houses. In particular, in the case of pig houses, it is difficult to solve the main problems even if automation and mechanization are applied with Information and Communications Technologies (ICT). The air recirculation technology can be applied as a technology that can solve these typical problems in the pig industry, such as growth environment, livestock disease, odor emission, energy cost, and pig productivity. The air recirculated ventilation system (ARVS) can minimize the inflow of air from the outdoors and recycle the internal thermal energy of the pig house. The ARVS consists of (1) an air scrubber module, (2) an external air mixing module, (3) a UV cleaning module, (4) a solar heat module, and (5) an air distribution module. In this study, the growth environment of piglets was predicted using a numerical model when the ARVS was applied. Since the concept of air recirculation was used, numerous equations for predicting the internal environment should be iteratively calculated. Furthermore, it was necessary to determine the optimum condition of the modules by applying various boundary conditions. Therefore, the model was designed for numerical analysis based on the balance equations of environmental factors inside the piglet room. For each module, the module coefficient and equations were considered based on the previous studies. The analysis was conducted according to the system diagram of each module, and the growth environment inside the piglet room was evaluated according to the various environmental conditions. As a result of calculating the numerical model, the ventilation rate of 40 CMM or more was advantageous to properly maintaining the gas environment. In the summer season, it was necessary to additionally use the cooling device and dehumidifier. In the winter season, when using a heat exchanger and solar module, was more advantageous for maintaining air temperature inside the piglet room.

Особенности проектирования высокотемпературных пластинчатых теплообменников для малоразмерных газотурбинных двигателей

An increase in the fuel efficiency of small-sized gas turbine engines can be achieved by regenerating the heat of the turbine exhaust gases. A rational layout solution in this case is a turboshaft scheme, where the effective power is generated on the shaft of a free turbine, and the turbine exhaust gases are released into the environment without doing useful work. When creating a turboshaft engine with heat recovery, the concept of developing engine family on the base of unified gas-generator was considered. The concept involves the development of a modular system, where the addition or exclusion of individual large units allows changing the type of engine at minimal cost. The article presents the layout solution of a small-sized turboshaft gas turbine engine with heat recovery, developed on the basis of a unified gas-generator and using a gearbox to transfer effective power to a propeller or a rotor. A plate heat exchanger module with a corrugated heat exchange surface for a small-sized turboshaft gas turbine engine has been designed. The heat exchange matrix was developed using a complex techniques of computer-aided design, calculation and manufacture of plate heat exchangers. Some design features of high-temperature plate heat exchangers are identified, the most important of which is the non-uniformity of temperature fields in the heat exchange matrix. Taking into account the non-uniformity of temperature fields, the heat exchanger module is a collapsible structure allowing the replacement of the heat exchange matrix and providing compensation for thermal expansion of the heat exchanger elements. The designed plate heat exchanger module for a small turboshaft gas turbine engine will be manufactured and tested on the bench

An integrated system of sinusoidal-corrugated plate heat exchanger and thermoelectric modules for wastewater heat recovery

This paper describes a new integrated system of sinusoidal-corrugated plate heat exchanger (SPHX) and thermoelectric modules (TEMs) applied in industrial wastewater heat recovery (IWWHR). The TEMs are mounted inside the baffles of SPHX, which is beneficial to minify the entire system volume and reduce the impact of TEMs on the heat transfer of SPHX. The complex SPHX prototype is fabricated by laser powder bed fusion (LPBF) technology and employed to validate the accuracy of built numerical SPHX model. To highlight the superior performance of designed SPHX, its capabilities on heat transfer are compared with a baseline plate heat exchanger (BPHX). The results show that the sinusoidal-corrugated structure is more beneficial for inducing vortices in the flow field. And the maximum heat transfer efficiency and overall heat transfer coefficient of SPHX can reach 70.94% and 2036.531 W/(m2⋅K), respectively, better than those of BPHX. The calculations of net output power show that enough output power can be generated to offset the pumping power of all working media in both the systems of SPHX and BPHX, indicating that the integrated system with SPHX and TEMs is appropriate to recover the heat from industrial wastewater. This study opens a new avenue for the design of HX and TEMs applied in IWWHR.

On the interactions of the induced flow field of heat exchangers with axial fans

In a large number of applications, heat exchanger modules consist of a combination of a heat exchanger and a turbomachinery. An axial fan is often used as the turbomachine in these scenarios. These modules are part of the daily life of people and are located in the direct vicinity of them. The interaction of the flow field with the heat exchanger generates disturbed inflow conditions upstream of the axial fan, which are characterized by increased turbulence properties. These disturbed inflow conditions often lead to increased sound radiation from the fan. In this study, the flow field of eight different heat exchangers was characterized and the effects on the sound emissions of the axial fan were analyzed. The main focus was on the geometry of the heat exchanger. By means of smoke visualization, the formation of significant turbulence points in the flow field of heat exchangers could be demonstrated. The spots with increased turbulence intensities are induced by the geometry transition from rectangular to round between the heat exchanger and the duct of the axial fan. It was found that a round geometry of the heat exchanger leads to a more homogeneous flow field and thereby reduces the sound emissions of the axial fan. Also a increase of the flow through area of the heat exchanger brings benefits for the acoustics of the axial fan. Especially the tonal components of the blade passing frequency of the fan were strongly dependent on the chosen heat exchanger. The tonal components could be reduced if the homogeneity of the flow field was increased by a round heat exchanger geometry.

Design and Verification of Calorimeter for CFETR Neutral Beam Injection System Prototype with Negative Ion Source

Currently, a neutral beam injection (NBI) system prototype with a 200-keV negative ion source, called the negative neutral beam injection (NNBI) system, is under construction for the China Fusion Engineering Test Reactor Project. In the NNBI system, the calorimeter is an extremely important high-heat-flux component, and its panels have to withstand a heat flux density of up to dozens of MW/m2 under some extreme conditions; thus, its efficient heat transfer enhancement design and the corresponding supporting structural design are most important, especially under the condition of a 3600-s long pulse. According to the detailed design requirements of the NNBI system, an overall design scheme of the calorimeter based on the heat transfer enhancement structure of the swirl tube (SW for short) is proposed in this paper. By using the gas-liquid two-phase flow boiling model and the supporting structure’s finite element model, the heat transfer performance of the heat exchange module, the mass flow distribution and pressure drop of the entire cooling circuit of the component, and the strength of the support structure are evaluated to verify the feasibility of the design scheme. Finally, based on the proposed design scheme, the detailed design of the temperature monitor system, which has high reliability and economy, is completed. This research provides important theoretical and engineering support for the structural development of the calorimeter for the NNBI verification prototype and will also provide references for the design and development of other internal components of large-scale fusion devices.