Heat Exchanger Components Research Articles

Constitutive modelling of aluminium alloy sheet at warm forming temperatures

The formability of aluminium alloy sheet can be greatly improved by warm forming. However predicting constitutive behaviour under warm forming conditions is a challenge for aluminium alloys due to strong, coupled temperature- and rate-sensitivity. In this work, uniaxial tensile characterization of 0.5 mm thick fully annealed aluminium alloy brazing sheet, widely used in the fabrication of automotive heat exchanger components, is performed at various temperatures (25 to 250 °C) and strain rates (0.002 and 0.02 s-1). In order to capture the observed rate- and temperature-dependent work hardening behaviour, a phenomenological extended-Nadai model and the physically based (i) Bergstrom and (ii) Nes models are considered and compared. It is demonstrated that the Nes model is able to accurately describe the flow stress of AA3003 sheet at different temperatures, strain rates and instantaneous strain rate jumps.

Development and demonstration of a compact ammonia–water absorption heat pump prototype with microscale features for space-conditioning applications

This paper presents the development and demonstration of a compact packaged prototype of a single-effect ammonia–water absorption cooling system with a nominal cooling capacity of 3.5kW. The packaged unit encompasses a combustion module to supply thermal energy to the system where heat is exchanged between combusted gas and a heat transfer fluid. The heat transfer fluid provides heat to the desorber where refrigerant is generated. The heat and mass exchange components of the absorption system are integrated into two monolithic blocks. The sub-components of each monolith utilize microscale heat and mass transfer passages, which have higher heat and mass transfer coefficients compared to conventional designs, resulting in substantial reductions in the required size of the system. Semi-autonomous control algorithms are developed to enable stand-alone operation of the packaged unit. System performance is measured over a range of operating conditions and compared with predictions of the corresponding system model.

FEM Simulation of the FSW Process of Heat Exchanger Components

FEM Simulation of the FSW Process of Heat Exchanger Components

Testing, simulation and soft-optimization of R410A low-GWP alternatives in heat pump system

The environmental impact of high global warming potential (GWP) refrigerants pushed the HVAC&R industry to investigate alternative refrigerants. R410A is a common refrigerant for air conditioning and heat pumping applications, but has a GWP of 2088. Drop-in tests of three R410A low-GWP alternative refrigerants (R32, D2Y60 and L41a) in a 10.55 kW capacity split heat pump unit were performed. The results show that R32 and L41a are good replacement candidates for R410A. A finite volume heat exchanger model and component based vapor compression system simulation tools were validated against the experimental data. Most of the predicted COP and capacity results of R32 experiments lie within 5% of the measured values, which is in good agreement with the experiments. Further investigation was carried out by varying the size of the compressor and adding a suction line heat exchanger to the system to match the capacity to that of R410A.

A spectral model for transient heat flow in a double U-tube geothermal heat pump system

This paper introduces a semi-analytical model based on the spectral analysis method for the simulation of transient conductive-convective heat flow in an axisymmetric shallow geothermal system consisting of a double U-tube borehole heat exchanger embedded in a soil mass. The proposed model combines the exactness of the analytical methods with an important extent of generality in describing the geometry and boundary conditions of the numerical methods. It calculates the temperature distribution in all involved borehole heat exchanger components and the surrounding soil mass using the fast Fourier transform, for the time domain; and the complex Fourier and Fourier-Bessel series, for the spatial domain. Numerical examples illustrating the model capability to reconstruct thermal response test data together with parametric analysis are given. The CPU time for calculating temperature distributions in all involved components, pipe-in, pipe-out, grout, and soil, using 16,384 FFT samples, for the time domain, and 100 Fourier-Bessel series samples, for the spatial domain, was in the order of 3 s in a normal PC. The model can be utilized for forward calculations of heat flow in a double U-tube geothermal heat pump system, and can be included in inverse calculations for parameter identification of shallow geothermal systems.

Selection of Numerical Methods and Their Application to the Thermo-Ecological Life Cycle Cost of Heat Exchanger Components

Thermo-Ecological Cost with the inclusion of Life Cycle (TEC-LC) is defined as the cumulative exergy consumption of non-renewable natural resources associated with any product and its life cycle, taking into account the necessity to prevent and compensate losses caused by depletion of natural resources and the release of harmful substances into the environment. The problem of collecting data for solving TEC-LC equations is not the only one which can be faced in determining this indicator. The selection of the calculation method could also affect obtained results due to the accuracy of the selected algorithm. Numerical stability is particularly important in the case of large sets of data and in this case operations on large matrixes. The issue with a set of TEC-LC balanced equations is examined and compared on the basis of heat exchanger components.

Limitations of Additive Manufacturing on Microfluidic Heat Exchanger Components

This work describes the testing of microfluidic components created using additive manufacturing. An Objet Eden 250 was used to create microfluidic channel test coupons with passages ranging from 0.5 to 3.0 mm and wall thicknesses ranging from 0.032 to 0.5 mm. Coupons were cleaned and tested under flow to examine structural integrity. Microfluidic channels with wall thicknesses down to 0.032 mm could be printed, cleaned, and tested successfully, although plastic deformation was observed in coupons with wall thicknesses below 0.1 mm. Given these limits, additive manufacturing based microfluidic heat exchangers (HXs) offer cost and performance benefits in natural convection HX applications.

Characterization of high temperature tensile and creep–fatigue properties of Alloy 800H for intermediate heat exchanger components of (V)HTRs

Alloy 800H is considered as a candidate material for intermediate heat exchanger (IHX) components of (very) high temperature reactors (V)HTRs. Qualification of the this alloy for the aforementioned nuclear applications requires understanding of its high temperature tensile, low-cycle fatigue behavior and creep–fatigue interactions because the IHX components suffer from combined creep–fatigue loadings resulting from thermally induced strain cycles associated with start-up and shutdown cycles. To this end, in this paper, the tensile properties of the Alloy 800H base and tungsten inert gas (TIG) welded materials are studied at three different temperatures, room temperature 21, 700 and 800°C. Low cycle fatigue (LCF) behavior of the base material is investigated at 800°C with no-hold time (no-HT) and hold time (HT) to study creep–fatigue interactions. The tensile test results showed substantial differences between the strength and ductility properties of the base and weld materials at all 3 temperatures, however, the trends in temperature dependence of tensile properties are similar for both base and weld materials. LCF studies with no-HT and HT showed a strong influence of HT on the low cycle fatigue life of this alloy illustrating the substantial influence of creep mechanisms at 800°C. Finally, cumulative values of creep versus fatigue damage fractions are plotted in a creep–fatigue interaction diagram and these results are discussed with respect to the existing bi-linear damage summation curve for Alloy 800H in ASME Code Case N-47 in order to understand the synergetic effects of both the damage mechanisms.

Concurrent multi-response optimization of austenitic stainless steel surface roughness driven by embedded lean and green indicators

Abstract International ecodesign initiatives encourage drilling process improvements that are also attentive to energy and peripheral materials consumption. A stainless-steel heat-exchanger component is optimized for surface quality during drilling while taking into account lean-and-green improvements. A non-linear four-factor fractional factorial scheme has been utilized to investigate the surface roughness performance due to: 1) the feed rate, 2) the spindle speed, 3) the twist drill type and 4) the coolant concentration. We address simultaneously the cumulative effect of multiple consecutive drillings on the surface quality of the last machined hole of a tube-sheet test plate. The concurrent optimization effort regulated the weighted surface quality performance of the drilling process by suppressing consumptions for: 1) energy – monitored at the final drilling and 2) coolant fluid. The weighted distribution-free optimization scheme was repeated to compound information from a key lean process indicator, the drilling processing time. It was found that the feed rate (at 70 mm/min) and the spindle speed (at 350 rpm) commonly influence non-linearly the surface roughness response (predicted at 1.05 μm) in both multi-response scenarios. The drill type (Guhring No. 8520) was also a statistically important effect when excluding optimality with respect to improved lean and green process performance. In such a case, the spindle speed needed to be decreased to 300 rpm for a predicted surface roughness of 0.86 μm (confirmed within 3%).

Nickel-based HVOF coatings promoting high temperature corrosion resistance of biomass-fired power plant boilers

There are over 1000 biomass boilers in Europe, and the number is increasing due to actions for reducing greenhouse gas emissions. Biomass boilers often experience strong corrosion due to harmful elements in fuels. In biomass burning, detrimental components include especially chlorine, potassium and heavy metals, which can cause chlorine-induced active oxidation or hot corrosion by molten phases even at fairly low temperatures. In order to increase the corrosion resistance of heat exchanger components, either more alloyed steels or protective coatings should be applied. High velocity oxy-fuel (HVOF) sprayed coatings may provide corrosion protection for low alloy tube materials. Three nickel based thermal spray coatings (Ni–24Cr–16.5Mo, Ni–22Cr<5Fe–9Mo–4Nb and Ni–22Cr–10Al–1Y) were tested for two years in a 40MW circulating fluidized boiler (CFB), which had experienced severe corrosion and a tube failure. The coated tubes were installed to the cold and the hot economizer. After the exposure the coatings and the substrate materials were analyzed with SEM–EDX. The uncoated boiler tubes corroded strongly, whereas the thermal spray coatings exhibited excellent corrosion performance. This paper presents the tube failure at the cold economizer, exposure conditions, the analysis of the coated and uncoated samples, and the corrosion mechanisms of the steel tubes.

Membrane Oxygenator Heat Exchanger Failure Detected by Unique Blood Gas Findings

Failure of components integrated into the cardiopulmonary bypass circuit, although rare, can bring about catastrophic results. One of these components is the heat exchanger of the membrane oxygenator. In this compartment, unsterile water from the heater cooler device is separated from the sterile blood by stainless steel, aluminum, or by polyurethane. These areas are glued or welded to keep the two compartments separate, maintaining sterility of the blood. Although quality control testing is performed by the manufacturer at the factory level, transport presents the real possibility for damage. Because of this, each manufacturer has included in the instructions for use a testing procedure for testing the integrity of the heat exchanger component. Water is circulated through the heat exchanger before priming and a visible check is made of the oxygenator bundle to check for leaks. If none are apparent, then priming of the oxygenator is performed. In this particular case, this procedure was not useful in detecting communication between the water and blood chambers of the oxygenator.

Numerical Investigation of Internal Pressure in a shell and Tube type of Heat Exchanger by using FEA

Shell and Tube Heat Exchangers are one of the most popular types of exchanger in heat transfer applications. Due to the flexibility, the designer has to allow for a wide range of pressures and temperatures. They are widely used in petroleum refineries, chemical plants, petrochemical plants, natural gas processing, air-conditioning, refrigeration and automotive applications. It utilizes a bundle of tubes through which one of the fluids flows. These tubes are enclosed in a shell with provisions for the other fluid to flow through the spaces between the tubes. In most designs of this type, the free fluid flows roughly perpendicular to the tubes containing the other fluid, in what is known as a cross-flow exchange. In nuclear reactors fuel rods may replace the tubes, and the cooling fluid flowing around the rods removes the heat generated by the fission process.A comprehensive Finite Element Analysis (FEA) has been performed on the critical heat exchanger components in order to validate the results of the components designed using the prescribed codes. The computational analysis helps visualize the areas of high stress concentration thereby aiding the designer to identify the failure prone regions. The regions susceptible to failure can be suitably modified to safeguard against failure. This paper aims at performing a design outputs by IBR codes of critical components of a shell and tube type heat exchanger in an attempt to show the redundancy in designing the components. Furthermore FEA shown the values of stress getting developed in the components for given operating conditions are much lesser than the allowable values of stress for those respective material. Thus the components are safe against such loading.

Effect of long-term operational aging on the mechanical properties and microstructure of austenitic 18Cr-9Ni steel and the weld metal

The properties of materials of the heat-exchange equipment components of the fast breeder reactor BN-600 after 130000–170000 h of operation at 500–550°C are studied. The effect of long-term aging on the strength, ductility, impact strength, and fracture toughness of 18Cr-9Ni steel (type 304 stainless steel) and its welds is examined. The mechanisms that give rise to changes in the mechanical properties are analyzed on the basis of microstructural and fractographic studies. The predicted degradation of material properties is estimated as a function of operating temperature and time.

12 ways to take a temperature

12 ways to take a temperature

Application of PLC in the Control System of Fins-Former

The fins are the basic components of the plate-fin heat exchanger. And fins-former is the special device to produce heat-exchanger. In this paper, some fins-former is used as research subjects, and Mitsubishis FX2N Series 32MT high-performance small programmable controller (PLC) is chosen as the main control unit to design the control system of its nesting cutting device. Then the control program is prepared. AC servo is used in the motion control system and finally the automation and control of the nesting cutting process is realized. It provides a useful method and reference for the automation control and transform of the fins-former.

Application of PLC in the Control System of Fins-Former

The fins are the basic components of the plate-fin heat exchanger. And fins-former is the special device to produce heat-exchanger. In this paper, some fins-former is used as research subjects, and Mitsubishis FX2N Series 32MT high-performance small programmable controller (PLC) is chosen as the main control unit to design the control system of its nesting cutting device. Then the control program is prepared. AC servo is used in the motion control system and finally the automation and control of the nesting cutting process is realized. It provides a useful method and reference for the automation control and transform of the fins-former.

SiSiC Heat Exchangers for Recuperative Gas Burners with Highly Structured Surface Elements

Heat exchangers are used in gas burners as recuperators. Their efficiency is proportional to their surface which is usually limited by the burner length and diameter. Ceramic recuperators used nowadays in industrial burners are tubular. We studied and developed a new generation of ceramic heat exchanger with the final goal of increasing the efficiency or, at similar efficiencies, of reducing their size and weight. A commercial SiSiC heat exchanger component was used to guarantee safety and robustness. The use of structured textile geometries followed by their conversion into a ceramic is the main innovation of this work.

Modelling of organic Rankine cycle system and heat exchanger components

Numerical models of a standard organic Rankine cycle (ORC) system and the heat exchangers comprising the system are developed as a design tool platform for a flexible design. The objective is design of an efficient, cost-effective ORC power plant that can effectively exploit low-grade industrial waste heat or low to medium-temperature geothermal fluid. Typical heat exchanger configurations were modelled, including the circular finned-tube evaporator, air-cooled condenser, and flat-plate preheater. A published ORC configuration and process conditions from experiments are used for the thermodynamic cycle analysis in order to validate of the system model. Heat transfer correlations and friction factors are described for the modelling of the heat exchangers. The simulation results of the ORC system provide the design requirements for the heat exchangers. Geometric specifications and performance of the heat exchangers are determined by iterative simulations.

Optimization of silane sol–gel coatings for the protection of aluminium components of heat exchangers

Despite the relatively low mechanical properties respect to the aluminium alloys but due to high thermal exchange capacity, pure aluminium (AA1XXX series) is widespread for industrial applications for heat exchanger components or cooling systems (like refrigerator systems). The corrosion protection properties of aluminium components are commonly enhanced by applying organic coatings or by performing chemical conversion treatments on aluminium surface. One of the routes for the protection of aluminium components for heat exchangers is the application of silane sol–gel coatings. In this work, a thin silane sol–gel coating improving the corrosion protection of aluminum for heat exchanger and avoiding the loss of thermal exchange due to the presence of the protective layer was developed. Prior to deposit, the silane layer as a mixture of three different silicon alkoxides precursors (such as tetraethoxysilane, glycidoxypropyltrimethoxysilane and methyltrithoxysilane), the optimum surface chemical treatment of the 1050 aluminum alloy, widely employed in the heat exchanger and cooling system industry, was investigated using electrochemical impedance spectroscopy (EIS). In order to enhance protective properties, different amounts of nano‐sized sodium montmorillonite were embedded into the silane network. Through taking advantage of some parameters extracted from EIS, the most efficient concentration of nanoclay was determined, confirmed by scanning electron microscopy and Fourier transform infrared analysis as well. The resistance of the different sol–gel layers to thermal cycles (strictly related to the application in the heat exchanger industry) was carried out to stress the sol–gel coating. The behavior of the investigated sol–gel layer after the thermal cycles was evaluated by means of EIS. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Investigation on the applicability of turbulent-Prandtl-number models for liquid lead-bismuth eutectic

With the proposal of Accelerator Driven Sub-critical System (ADS) together with liquid lead-bismuth eutectic (LBE) as coolant for both reactor and spallation target, the use of accurate heat transfer correlation and reliable turbulent-Prandtl-number model of LBE in turbulent flows is essential when designing ADS components of primary loop and heat exchanger of secondary loop. Unlike conventional fluids, there is not an acknowledged turbulent-Prandtl-number model for LBE flows. This paper reviews and assesses the existing turbulent-Pandtl-number models and various heat transfer correlations in circular tubes. Computational fluid dynamics (CFD) analysis is employed to evaluate the applicability of various turbulent-Prandtl-number models for LBE in the circular tube under boundary conditions of constant heat flux and constant wall temperature. Based on the assessment of turbulent-Prandtl-number models, the reliable turbulent-Prandtl-number models are recommended for CFD applications to LBE flows under boundary conditions of constant heat flux and constant wall temperature. The present study indicates that turbulent Prandtl number has a significant difference in turbulent LBE flow between constant-heat-flux and constant-wall-temperature boundary conditions.