Plate-fin Heat Exchanger Research Articles

Preliminary Structural Design and Analysis of the Horizontal Cold Box for CFETR 25 kW@4.5 K Helium Refrigerator

The China Fusion Engineering Test Reactor cryogenic system mainly provides necessary supercritical helium for cooling superconducting coils and structure to transfer the static thermal load and the dynamic thermal load generated during plasma operation mode. According to the conceptual design of CFETR cryogenic system, the cooling capacity at 4.5 K is about 125 kW, with five 25 kW@4.5 K helium refrigerators in parallel. As one of the main components, a horizontal cold box provides a vacuum and insulating working environment for plate-fin heat exchangers, turbines, adsorbers, control valves and pipes. This paper presents a preliminary structural design for the 25 kW@4.5 K helium refrigerator horizontal cold box. The structural strength and static heat leakage of the cold box including support seats are analyzed through the finite element simulation method. The simulation results further verify the rationality and feasibility of the cold box structure design, and provide a certain reference for the subsequent detailed engineering design.

A comprehensive design and optimization of an offset strip-fin compact heat exchanger for energy recovery systems

• Parametric, sensitivity, and optimization of compact heat exchanger is presented. • A normalized sensitivity analysis is used to identify the critical parameters. • Geometric parameters and fluid velocity appeared as the most influential parameters. • The optimization reduced the operational cost by 78%, and the total cost by 77%. Energy recovery in conventional thermal systems like power plants, refrigeration systems, and air conditioning systems has enhanced their thermodynamic and economic performance. In this regard, compact heat exchangers are the most employed for gas to gas energy recovery because of their better thermal performance. This paper presents an economic optimization of a crossflow plate-fin heat exchanger with offset strip fins. A detailed software-based numerical code for thermal, hydraulic, economic, and exergy analysis is developed for three fin geometries. Genetic Algorithm, parametric, and normalized sensitivity analyses are used to discover the most influential parameters to optimize the total cost. The parametric study showed that with the increase of mass flow rates and plate spacing, outlet stream cost and operating cost increased due to the rise in pressure drops. Finally, the optimization reduced the operational cost by ∼78.5%, stream cost by ∼64.5%, and total cost by ∼76.8%.

Commissioning of a replacement subatmospheric cold box for Jefferson Lab’s Central Helium Liquefier

Jefferson Lab’s Cryogenics Department has designed, fabricated, installed, and commissioned a new subatmospheric cold box to replace one of the two existing units within our Central Helium Liquefier (CHL). The replacement cold box, dubbed SC1R, pumps saturated helium vapor at 0.0385 atm from Jefferson Lab’s continuous electron beam accelerator facility (CEBAF) cryomodules to maintain an operating temperature of nominally 2.1 K. This is accomplished using a five-stage cryogenic centrifugal compressor (cold compressor) system and a brazed aluminum plate-fin heat exchanger operating between 2.1 K and 4.5 K. In this paper we will describe our experience commissioning the SC1R cold box. We will discuss pump-down of the system to 2.1 K and steady-state operation at the cold compressor design flow rates of 170, 200, and 250 g/s. Performance of the heat exchanger and cold compressors has been mapped across a range of flow rates and optimized for CEBAF operations. This commissioning data will be used to monitor future performance and adapt to changing load requirements.

Geometric optimization of thermo-hydraulic performance of multistream plate fin heat exchangers in two-stage condensation cycle: Thermodynamic and operating cost analyses

LNG is an energy carrier with growing importance, but LNG cryogenic cycles are energy-intensive. Because the thermo-hydraulic performance of heat exchangers affects the operation and energy consumption of a compressor. The optimization of heat exchangers is key to improving the energy efficiency of a cryogenic plant. In this work, the screening analysis and optimization procedures are performed for a two-stage condensation plant to enhance the Coefficient of Performance (COP) as the operating performance criterion. Five geometric design categories of applied fins, such as fin type, fin height, fin thickness, fin frequency, and the number of layers of MPFHEs (Multistream Plate Fin Heat Exchanger) are selected as input parameters for the optimization process. Then, a thermodynamic analysis including the second law analysis and capital and operating costs assessment are carried out to show the improvements of applied optimization in the mentioned objectives. The results of the optimization procedure have indicated a considerable improvement in the COP of up to 13.7% and significant mitigation in total power consumption of up to 11.8 MW. Furthermore, the optimal configuration of heat exchangers presents an increase in exergy efficiency of up to 4.1%, a saving in exergy destruction of 10.2 MW and up to 8.6 M USD/year in the operating cost when compared with conventional cases.

Numerical investigation of condensation characteristics of a moist air-to-air plate-fin heat exchanger and experimental validation

The purpose of this study is to investigate the condensation characteristics of a moist air-to-air plate-fin heat exchanger (PFHE) used for dehumidification under high temperature and high humidity. A numerical simulation model of a PFHE was developed and an experimental system was established. Good agreement was observed between predicted and experimental data from two types of PFHEs with different fins. The effects of the operating parameters of both moist air side and cooling air side on the condensation characteristics of the PFHE were discussed in detail. The surplus potential of condensation (δ) is more affected by cooling air side especially the mass flow rate of cooling side (mca). When mca = 0.09 kg/s and mca = 0.03 kg/s, δ respectively changes from 0.625 to 0.919 and from 0.780 to 0.980 as the increase of the mass flow of dry air. Multiple operation strategies for energy saving of heat exchangers were proposed for the dehumidification process under high temperature and high humidity.

CFD Assessment of Flow Maldistribution in Plate Fin and Tube Heat Exchangers

The primary goal of this work is to use CFD assessment simulating framework is to anticipate the impact of injecting air flowing mal-distribution on heat exchanger architecture and thermal flow characteristics. Using CFD (computational fluid dynamics) simulation-studies, determine the impact of air intake flow unequal distribution or mal-distribution on the complete redesign as well as high - temperature hydraulic performing ability of HEX (heat exchangers). The findings demonstrate that a plate as well as tube fin heating element consisting of an elongated tubular setup slanted by 30 degrees can achieve the highest temperature transmission, having a heat transfer ability of 23.22 percent greater than a (SPHEX) spherical pipe heat exchanger.

Experimental and numerical investigation of additively manufactured novel compact plate-fin heat exchanger

Plate-fin heat exchanger (PFHX) is one of the vital compact heat exchangers due to its high heat transfer area per unit volume and promising potentials in industrial applications where dimensions and weight are limited. Additive manufacturing presents great potentials for fabricating novel compact heat exchangers. In this work, three types of compact heat exchangers including a PFHX with twisted fins, a PFHX with improved rectangular fins and a PFHX with conventional rectangular fins are manufactured using the laser powder bed fusion (LPBF) technology. The experimental tests together with numerical simulations are conducted to evaluate the thermal performance and pressure drop of the heat exchangers. The results show that PFHX with twisted fins exhibits superior thermal performance among the three heat exchangers, and the PFHX with improved rectangular fins has the highest experimental coefficient of performance (COP) and provides outstanding overall performance. Furthermore, the impact of LPBF accuracy on the performance of heat exchanger are discussed to provide guidance for future designs.

Passage Arrangement Optimization of Plate-Fin Heat Exchanger under Uncertain Operating Conditions

As the total flow rate and passage number increase, the quality of the passage arrangement has an important influence on the thermal efficiency of a multi-stream plate-fin heat exchanger (PFHE). The operating conditions are uncertain due to changes in environmental and product requirements, which affect the design of passage arrangements. If this influence is not considered enough in design, it will lead to the loss of heat transfer efficiency of the PFHE. Therefore, an optimization design method for passage arrangement is developed considering the influences of uncertain operating conditions. First, the uncertain operating conditions of the PFHE are represented using probability density functions of mass flow rates and temperature. Next, the optimization goals are chosen through the correlation calculation between the passage arrangement and the heat transfer indexes by the integral-mean temperature difference method. The particle swarm optimization algorithm is adaptively improved for the passage arrangement calculation. Then, the result under uncertain operating conditions is compared with the result under a single condition. The total heat transfer rate is increased, and the dimensionless mean square error of the cumulative heat load is decreased, so the method of designing the passage arrangement under uncertain operating conditions is effective.

A Review on Various Types of Fins Geometries in Plate fin and Tube Heat Exchangers

Fin-and-tube heat exchanging systems are the another very commonly utilised heat exchangers for thermal energy transformation, with implementations in air conditioners, cooling systems, the automotive sector, electrical gadgets, and other areas. The market for more effective refrigeration via smaller heat exchangers has resulted in extensive investigation on the subject. The thermal efficiency exploration methodologies and comprehensive flow and heat transfer analysing outcomes of fin-and-tube HEs are summarised in this review. This study also examined the massive heat transfer boosters, as well as their arrangement and shape. In addition, an overview of both theoretical and empirical research on the effectiveness of HEs is provided

Aerodynamic shape optimization of an electric aircraft motor surface heat exchanger with conjugate heat transfer constraint

Electrified aircraft benefit from the versatile ways electric motors can be integrated with an airframe. However, thermal management is needed to move waste heat out of the motors because the heat is not expelled with the exhaust as in a conventional engine. Plate-fin, fin, and surface heat exchangers are incorporated as air-side heat exchangers for electrified aircraft thermal management systems. Typically, analytic tools are used to design heat exchangers within these categories. However, analytic tools lack the fidelity required for detailed shaping and assessment of general heat exchanger configurations. Tools based on first principles, such as finite element analysis or computational fluid dynamics, can verify heat exchanger performance but are too costly to use in a manual design loop. Shape optimization can be used with first-principles-based models to design heat exchangers without limiting the geometry to those previously well studied. In this work, we apply this methodology to design a heat sink for the high-lift motor of an electric technology demonstrator, the X-57 Maxwell. We use a gradient-based optimizer to modify the thickness distribution of the heat sink to find designs that minimize drag while meeting the heat load constraint. To model the heat transfer from the motor, we use both convection-only and conjugate heat transfer models and compare the resulting differences in the optimized shapes. We found that the convection-only model under-predicted heat rejection and thus led to larger than necessary heat sinks when used in optimization. To study the effect of the heat load on the design, we compare the heat sinks designed for the baseline motor and heat sinks designed for less efficient motors. Our study results show how the heat exchanger’s geometry changes from uniformly thick to designs with fins as the heat load increases. Furthermore, we found that the variation in drag across designs is driven by differences in the pressure drag due to flow separation. Finally, we conclude with a comparison of the optimized designs to those representing more simple fin designs and find that the optimized designs have fins that are shifted forward to reduce the adverse pressure gradient, which mitigates separation on the aft part of the fin. The developed shape optimization method could also be applied to improve other heat exchangers, specifically those designed to reject relatively low amounts of heat.

System Simulation and Analysis of an LNG-Fueled SOFC System Using Additively Manufactured High Temperature Heat Exchangers

A laboratory-scale solid oxide fuel cell (SOFC) system using liquefied natural gas (LNG) as a fuel is designed to be used as an energy converter on seagoing vessels (MultiSchIBZ project). The presented system design phase is supported by thermodynamic system simulation. As heat integration plays a crucial role with regard to fuel recirculation and endothermic pre-reforming, the heat exchanger and pre-reforming component models need to exhibit a high degree of accuracy throughout the entire operating range. Compact additively manufactured tube-bundle and plate-fin heat exchangers are designed to achieve high heat exchange efficiencies at low pressure losses. Their heat transfer correlations are derived from experimental component tests under operating conditions. A simulation study utilizing these heat exchanger characteristics is carried out for four configuration variants of pre-reforming and heat integration. Their system behaviour is analyzed with regard to the degree of pre-reforming and the outlet temperature of the fuel processing module. The combination of allothermal pre-reforming with additively manufactured plate-fin heat exchangers exhibits the best heat integration performance at nominal full load and yields a partial load capability to up to 60% electrical load at net electrical efficiencies of 58 to 60% (LHV).

Investigation of the effects of fin perforations on the thermal-hydraulic performance of Plate-Finned heat exchangers

Design of fin profiles is a critical step in searching for more efficient heat exchangers. The present work performs a hybrid numerical-experimental analysis to obtain the thermal and hydraulic performances of the plate-finned heat exchangers. The analysis comprises a four-tube heat exchanger with in-line arrangement, being tested three fin patterns, i.e., rectangular with no insert (standard) and rectangular with diamond and circular perforations. The proposed methodology combines numerical simulation of the conjugate heat transfer problem (convection in the fluid/diffusion in the solid) with wind tunnel experimental data as boundary conditions. The ANSYS-Fluent® software is adopted to solve the three-dimensional average turbulent flow of air over the finned tubes within the framework of RANS model. The validation procedure compares the present results against empirical correlations for the Nusselt number available in the literature. Finally, a parametric study is addressed evaluating the influences of both the size and the shape of fin perforations upon the fluid dynamics and heat transfer behaviour. The main results indicate that larger sizes of the fin perforations (either circular or diamond shape) will enhance the comprehensive Performance Evaluation Criterion – the PEC parameter – and mass/volume thermal efficiency of the heat exchanger.

Heat transfer enhancement using non-equally structure in a plate-fin heat exchanger with offset fins

In this study, a cross-flow plate-fin heat exchanger with offset fins is optimized by considering the effects of flow maldistribution for air side. For this purpose, the study is focused on an increase in the rate of heat transfer, which can be achieved by using non-equally fin structure. Numerical simulations have been carried out to investigate the thermodynamic characteristics of the non-equally full-size plate-fin heat exchanger by using the porous media approach. Based on the numerical model, flow distribution, total heat rate and pressure drop of the plate-fin heat exchanger are studied. A asymmetric structure with heat transfer enhancement is presented in this study. After comparing numerical predictions of the total heat transfer rate and the pressure drop under various Reynolds number. It is observed that, the percentages of increase in effectiveness for the final non-equally structure are in the range of 2.5-6.2% and the pressure drop remains almost constant in the cases of air inlet velocity fixed at 9.5627 m/s. The increasing asymmetric structure is numerically verified to improve the flow distribution of the plate-fin heat exchanger.

Minimizing Heat Transfer Area of Plate-fin Heat Exchangers applying Class Topper Optimization

A variety of meta-heuristic optimization methods have recently been developed. Class Topper Optimization (CTO) is a new meta-heuristic optimization method to solve design related issues in mechanical devices for better manufacturing. Any mechanical system’s output is determined by how well the mechanical components are designed for manufacturing. The potency of the CTO based algorithm for designing certain mechanical systems, such as plate fin heat exchangers, is investigated in this piece of effort. In this research, the minimized area results acquired using the CTO method is compared to those achieved using other optimization strategies. Finally, the CTO algorithm outperforms compared to some existing meta-heuristic optimization algorithm for solving a mechanical issue.

Experimental Investigation on Prototype Latent Heat Thermal Battery Charging and Discharging Function Integrated with Solar Collector

This paper reports the performance investigation of a newly developed Latent Heat Thermal Battery (LHTB) integrated with a solar collector as the main source of heat. The LHTB is a new solution in the field of thermal storage and developed based on the battery concept in terms of recharge ability, portability and usability as a standalone device. It is fabricated based on the thermal battery storage concept and consists of a plate-fin and tube heat exchanger located inside the battery casing and paraffin wax which is used as a latent heat storage material. Solar thermal energy is absorbed by solar collector and transferred to the LHTB using water as Heat Transfer Fluid (HTF). Charging experiments have been conducted with a HTF at three different temperatures of 68°C, 88°C and 108°C and three different flow rates of 30, 60 and 120 l/h. It is followed by discharging experiments on fully charged LHTB at three different temperatures of 68°C, 88°C and 108°C using HTF at three different flow rates of 30, 60 and 120 l/h. It is found that both higher HTF inlet temperature and flow rate have a positive impact on stored thermal energy. However, charging efficiency was decreased by increasing the HTF flow rate. The highest charging efficiency of 29% was achieved using HTF of 108°C at a flow rate of 30 l/h. Most of paraffin melted in this case, while part of the paraffin remained solid in other experiments. On the other hand, the results from discharging experiments revealed that both recovered thermal energy and recovery efficiency increased by either increasing the LHTB temperature or HTF flow rate. Highest recovered thermal energy of 5,825 KJ at 35% recovery efficiency achieved at LHTB of 108°C using 120 l/h of HTF.

Comprehensive performance investigation and optimization of a plate fin heat exchanger with wavy fins

As the pressure drop and pump power increase with the enhancement of heat transfer, it is of great value to investigate the comprehensive performance of the heat exchanger based on common accurate correlations of heat transfer and flow friction. This paper adopts a generalized air-side thermal-hydraulic correlation study the comprehensive performances of the plate fin heat exchanger with wavy fins. To better understand the fin characteristics, performance indexes under the same flow rate, pressure drop and pump power are employed to estimate the comprehensive flow and heat transfer performances. The non-linear optimization problem is established in consideration of the multiple independent variables with the maximum effectiveness or the minimum modified entropy generation number as the optimization objective function, which is solved by the genetic algorithm. Comparative analysis is conducted for results obtained from the parametric analysis and heat exchanger optimization, indicating that the objective function of the modified entropy generation number is effective for the design optimization of the comprehensive performance.

Experimental Thermohydraulic Characterisation of Flow Boiling and Condensation in Additive Manufactured Plate-Fin Heat Exchanger

Experimental Thermohydraulic Characterisation of Flow Boiling and Condensation in Additive Manufactured Plate-Fin Heat Exchanger

Design Optimization of Plate-Fin Heat Exchanger in a Gas Turbine and Supercritical Carbon Dioxide Combined Cycle with Thermal Oil Loop

This paper presents an investigation on the optimum design for a plate-fin heat exchanger (PFHE) of a gas and supercritical carbon dioxide combined cycle which uses thermal oil as intermediate heat-transfer fluid. This may promote the heat transfer from low heat-flux exhaust to a high heat-flux supercritical carbon dioxide stream. The number of fin layers, plate width and geometrical parameters of fins on both sides of PFHE are selected as variables to be optimized by a non-dominated sorting genetic algorithm-II (NSGA-II), which is a multi-objective genetic algorithm. For the confliction of heat transfer area and pressure drop on the exhaust side, which are the objective indexes, the result of NSGA-II is a Pareto frontier. The technique for order of preference by similarity to ideal solution (TOPSIS) approach is applied to choose the optimum solution from the Pareto frontier. Finally, further simulation is performed to analyze the effect of each parameter to objective indexes and confirm the rationality of optimization results.

Inference of faults through symbolic regression of system data

We present the development of inferential sensors that use system input and output measurements to improve the accuracy and robustness of fault detection and isolation. These inferential sensors transform and augment the sensed information of a system to: (i) minimize the evidence of uncertainty in the inferred variables, decreasing the rates of false alarms and nondetections; and (ii) provide distinguishable estimates of the existence and/or severity of faults, decreasing the rate of misdiagnoses. The proposed method symbolically regresses the noisy and uncertain system measurements, using genetic programming, to evolve uniquely explainable mathematical functions that minimize a least-squares objective of the fault inference. A standard workflow utilizing the proposed algorithm for fault diagnostics is presented and illustrated in the classification of the severity of fouling in a cross-flow plate-fin heat exchanger. The effectiveness and robustness of the method are explored at different test designs, assessed using k-nearest neighbors classification, and compared to other traditional fault classification methods. The extension of the inferential sensors to information theoretic metrics, where the system model is augmented to improve the evidence of fault(s) is also discussed.

A Framework for Multi-Objective Optimization of Plate-Fin Heat Exchangers Using a Detailed Three-Dimensional Simulation Model

The design of a multi-stream plate-fin heat exchanger is a highly integrated task with multiple opposing objectives and many degrees of freedom. This work shows how it can be fully or partially automated by the combination of a detailed three-dimensional simulation model and an optimization routine. The desired task is formulated as the target of a multi-objective optimization and solved using a genetic algorithm. The workflow is presented using a cryogenic plate-fin heat exchanger with four process streams. The design is optimized towards high efficiency, low pressure drop, and low unit weight by adjusting the outer geometry, the inlet and outlet distributor configuration, and the detailed stream geometry. A detailed analysis of the Pareto-set gives a good overview of possible solutions, and the optimization routine can automatically find a feasible design with a reasonable tradeoff between the objectives. All elements of the framework are implemented in open source software. A highlight of this research is that a very comprehensive and detailed simulation model is employed in the optimization framework. Thus, the presented method can be easily adjusted to fit the needs of other engineering tasks.