Mechanical

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On the microstructure and dynamic mechanical behavior of Cu–Cr–Zr alloy manufactured by high-power laser powder bed fusion
(Elsevier, 2025) Azizi, Nadia; Asgari, Hamed; Hasanabadi, Mahyar; Odeshi, Akindele; Toyserkani, Ehsan
This study explores high-power laser powder bed fusion (LPBF) processing of Cu–Cr–Zr alloy, focusing on its high strain rate dynamic mechanical response and microstructural evolution. The alloy undergoes significant strain hardening during dynamic impact loading, primarily attributed to intensified dislocation interactions and multiplication. This is accompanied by thermal softening induced by adiabatic heating, therefore improving strain accommodation. As the strain rate increases from 4400 s−1 to 11300 s−1, the ultimate compressive strength (UCS) enhances from 173 ± 8 MPa to 489 ± 14 MPa, demonstrating a high strain rate sensitivity (SRS) of ∼ 1. Microstructural examinations reveal that higher strain rates intensify the occurrence of adiabatic shear bands (ASBs), leading to severe localized plastic deformation. These ASBs generate localized stress concentrations, which in turn accelerate crack initiation and propagation through pore formation and coalescence within the ASBs. Despite this severe plastic deformation, texture analysis indicates that the crystallographic texture remains largely stable which suggests that the deformation mechanism is primarily governed by dislocation motion and interaction, rather than by crystal structure reorientation. Overall, the alloy balances strain hardening and strain accommodation at high strain rates, making it well-suited for applications requiring strength and resilience under dynamic impacts.
Coarse for Fine: Bounding Box Supervised Thyroid Ultrasound Image Segmentation Using Spatial Arrangement and Hierarchical Prediction Consistency
(IEEE Journal of Biomedical and Health Informatics, 2025) Chi, Jianning; Lin, Geng; Li, Zelan; Zhang, Wenjun; Chen, Jia-hui; Huang, Ying
Weakly-supervised learning methods have become increasingly attractive for medical image segmentation, but suffered from a high dependence on quantifying the pixel-wise affinities of low-level features, which are easily corrupted in thyroid ultrasound images, resulting in segmentation over-fitting to weakly annotated regions without precise delineation of target boundaries. We propose a dual-branch weakly-supervised learning framework to optimize the backbone segmentation network by calibrating semantic features into rational spatial distribution under the indirect, coarse guidance of the bounding box mask. Specifically, in the spatial arrangement consistency branch, the maximum activations sampled from the preliminary segmentation prediction and the bounding box mask along the horizontal and vertical dimensions are compared to measure the rationality of the approximate target localization. In the hierarchical prediction consistency branch, the target and background prototypes are encapsulated from the semantic features under the combined guidance of the preliminary segmentation prediction and the bounding box mask. The secondary segmentation prediction induced from the prototypes is compared with the preliminary prediction to quantify the rationality of the elaborated target and background semantic feature perception. Experiments on three thyroid datasets illustrate that our model outperforms existing weakly-supervised methods for thyroid gland and nodule segmentation and is comparable to the performance of fully-supervised methods with reduced annotation time. The proposed method has provided a weakly-supervised segmentation strategy by simultaneously considering the target's location and the rationality of target and background semantic features distribution. It can improve the applicability of deep learning based segmentation in the clinical practice. The source code and relative datasets will be available at https://github.com/LanLanUp/SAHP-Net.
Hydrogen uptake and embrittlement behavior in pipeline steels: Insights from slow strain rate testing and synchrotron micro-CT imaging
(Engineering Failure Analysis, 2025-02) Jack, Tonye; Webb, Mark Adam; Rahman, K.M. Mostafijur; Fazeli, Fateh; Szpunar, Jerzy
Hydrogen embrittlement (HE) presents a major challenge to the integrity of steel pipelines, often leading to premature failure. Traditional methods using two-dimensional (2D) analysis of damaged structures, often overlook critical features related to failure. Hence, this study investigates the hydrogen embrittlement susceptibility of two pipeline steels, X60 and X65, using a combination of mechanical testing, hydrogen diffusion and trapping studies, microstructural characterization, and synchrotron micro-computed tomography (micro-CT) imaging. The results highlight the critical role of hydrogen trapping and retention in HE, with steel microstructure significantly affecting hydrogen uptake and diffusion as well as crack nucleation and propagation. Synchrotron micro-CT imaging provided more accurate crack pattern assessments than traditional 2D methods, revealing potential misinterpretations from 2D cross-sectional analysis. This study concludes that simultaneous hydrogen ingress and mechanical loading is more damaging than pre-charging with high hydrogen concentrations, and that hydrogen retention capacity plays a greater role in embrittlement behavior than crack initiation. The failure mechanism of the hydrogen-charged steels shifted from being plasticity-based to decohesion-driven, based on the hydrogen content and retention in the steel, which is in line with the unified HELP+HEDE model.
A methodology for selection of solid desiccants in energy recovery ventilators
(Elsevier, 2025-01-15) Krishnan, Easwaran N.; Ramin, Hadi; Gurubalan, A.; Muneeshwaran, M.; Li, Kai; Nawaz, Kashif; Simonson, Carey
Controlling indoor humidity levels is essential for maintaining acceptable indoor air quality in buildings. The use of energy recovery ventilators (ERVs) is an energy-efficient way to regulate indoor air humidity. Fixed-bed regenerators and rotary wheels are widely used ERVs because of their high sensible and latent effectiveness. These ERVs are made of desiccant-coated substrates, which enable them to transfer moisture between the supply and exhaust air streams. However, the moisture transfer ability of ERVs depends on the physiochemical and sorption properties of desiccants. Extensive, full-scale experiments are required to determine the best desiccant material for these systems. This paper presents a simplified method of selecting suitable desiccant materials for ERVs. The methodology involves important characterization methods, literature correlations for performance prediction, and cost-effective testing methods prior to full-scale testing, and full-scale test methods are discussed in detail. Furthermore, the performance of a few newly derived materials is evaluated and compared with that of conventional desiccants such as silica gel and molecular sieves. The highest latent effectiveness was obtained for composite of super absorbent polymer (SAP) with potassium formate (SAP-HCO2K-50 %), all-polymer porous solid desiccant (APPSD) and metal organic framework (MOF)–MIL–101 (Cr), followed by activated carbon fibre felt (ACFF) Silica sol-LiCl30, SAP, silica gel, MOF–303, and molecular sieve. Researchers and manufacturers would benefit from the proposed methodology and presented data in developing new desiccant materials for ERV applications.
High strain rate compressive behavior of laser powder bed fused Inconel-718
(Elsevier, 2024-12-31) Hasani, Navid; CHALASANI, DHARMENDRA; Alaghmandfard, Reza; Keshavarzan, Mohsen; Forooghi, Foroozan; sanjari, mehdi; Shalchi Amirkhiz, Babak; Janaki Ram, G.D.; Pirgazi, Hadi; Kestens, Leo; Odeshi, Akindele; Mohammadi, Mohsen
Inconel-718 (IN718) is extensively utilized in the aerospace industry, notably in applications such as aircraft engines, facing a constant risk of foreign object impact loadings. Limited studies exist on the dynamic behavior of IN718 under high strain rate loadings, crucial for addressing the challenges of elevated operational temperatures and impact risks in aircraft engines. The dynamic deformation behavior of IN718 samples processed by laser powder bed fusion (LPBF) was studied at varying strain rates. True stress-strain curves showed rapid flow stress increase and semi-serrated stress-strain curves due to strain hardening and thermal softening competition. AMS 5664 heat treatment borrowed from the aerospace materials specifications (AMS) for nickel alloys led to a 28 % increase in ultimate compressive strength (UCS) at high strain rates. The aging treatment led to precipitation of uniformly distributed strengthening γ" and γ′ phases. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations revealed adiabatic shear band (ASB) formation during high strain-rate deformation, indicating local temperature rise. High-density dislocation networks and nanoscale γ" and γ′ precipitates enhanced IN718 strength by inhibiting dislocation motion. Electron backscatter diffraction (EBSD) analysis highlighted texture changes, and the impact of strain rate on grain size distribution was observed. Slip activity increased after heat treatment, influencing ductility. Analysis of twins, kernel average misorientation (KAM), low-angle grain boundaries (LAGBs), and high-angle grain boundaries (HAGBs) were performed to investigate their contribution to the strength properties. Fracture surface analysis at 5150 s 1 revealed a complex mechanism, with outer regions exhibiting ductile features and inner regions indicating shear fracture. The Chang-Asaro (CA) model predicted IN718 flow behavior under high strain rates, subsequently incorporated into ABAQUS Explicit software for numerical simulation. Lagrangian smoothed particle hydrodynamics (SPH) in combination with the VUHARD subroutine were employed to simulate the SHPB experiments. The constitutive model incorporated in the subroutine accurately captured the nonlinear behavior of the specimens, such as equivalent plastic strain and temperature. The results demonstrated a strong validation between the experimental and numerical methodologies.
Extrusion bioprinting from a fluid mechanics perspective
(ACCSCIENCE, 2024-08-30) Gharraei, Reza; Bergstrom, Donald; Chen, Xiongbiao (Daniel)
Bioprinting is an emerging technology for fabricating intricate and diverse structures that closely mimic natural tissues and organs for such applications as tissue engineering, drug delivery, and cancer research as well. Among the various bioprinting techniques, extrusion-based bioprinting stands out due to its capability to apply a wide range of biomaterials and living cells and its controllability over printed structures. In bioprinting, the bioink stored in a syringe is forced to flow through the nozzle connected to the syringe, and then to exit and deposit onto the printing stage to form three-dimensional (3D) structures. The bioprinting process involves the flow of bioink in both syringe and nozzle and then its flow or spreading on a printing stage. As a result, fluid mechanics plays a crucial role in extrusion bioprinting. Notably, the biomaterials used in bioprinting are typically non-Newtonian fluids, which have complex viscoelastic and thixotropic behaviors; and the influence of these behaviors on the bioprinting process has been drawn considerable attention by employing various methods, including the numerical simulations via computational fluid dynamics (CFD). This paper reviews the latest development in the fluid mechanics aspects of extrusion-based bioprinting to shed light on the challenges and key considerations involved. It covers the topics of extrusion bioprinting (including driving mechanisms, printability, cell viability), biomaterial rheology and its effect on bioprinting, multi-material bioprinting and numerical simulation of bioprinting. Key issues and challenges are also discussed along with the recommendations for future research.
MugenNet: A Novel Combined Convolution Neural Network and Transformer Network with Application in Colonic Polyp Image Segmentation
(Sensors, 2024-11) Peng, Chen; Qian, Zhiqin; Wang, Kunyu; Zhang, Lanzhu; Luo, Qi; Bi, Zhuming; Zhang, Wenjun
Accurate polyp image segmentation is of great significance, because it can help in the detection of polyps. Convolutional neural network (CNN) is a common automatic segmentation method, but its main disadvantage is the long training time. Transformer is another method that can be adapted to the automatic segmentation method by employing a self-attention mechanism, which essentially assigns different importance weights to each piece of information, thus achieving high computational efficiency during segmentation. However, a potential drawback with Transformer is the risk of information loss. The study reported in this paper employed the well-known hybridization principle to propose a method to combine CNN and Transformer to retain the strengths of both. Specifically, this study applied this method to the early detection of colonic polyps and to implement a model called MugenNet for colonic polyp image segmentation. We conducted a comprehensive experiment to compare MugenNet with other CNN models on five publicly available datasets. An ablation experiment on MugenNet was conducted as well. The experimental results showed that MugenNet can achieve a mean Dice of 0.714 on the ETIS dataset, which is the optimal performance on this dataset compared to other models, with an inference speed of 56 FPS. The overall outcome of this study is a method to optimally combine two methods of machine learning which are complementary to each other.
Highly Stabilized Ni-Rich Cathodes Enabled by Artificially Reversing Naturally-Formed Interface
(Advanced Energy Materials, 2024-11) Ma, Jinjin; Sun, Yipeng; Wu, Duojie; Wang, Changhong; Yu, Ruizhi; Duan, Hui; Zheng, Matthew; Ruying, Li; Danny Gu, M; Zhao, Yang; Zhou, Jigang; Sun, Xueliang
A significant obstacle in the manufacturing and practical application of Ni-rich cathode materials is decreasing the manufacturing cost without sacrificing the cycling stability. Here a high-energy, ultrahigh-Ni, and nearly Co-free cathode with outstanding cycling performance is proposed. This promising cathode is enabled by artificially constructing an “outside-in” interface structure toward LiNi0.94Co0.05Mn0.01O2 (NCM94) cathodes. Combining theoretical prediction and experimental results, it is revealed that high interfacial stability is achieved by a specific surface chemistry with an outside-in structure composed of an inner organic layer and an outer inorganic layer. Benefiting from the protection effect of the robust outside layer and the strain relieve function of the inside layer, the intrinsic challenges of interfacial reactions, transition metal (TM) dissolution, and micro-crack propagation have been mitigated for the Ni-rich cathode. As a result, the “outside-in” strategy enables superior cycling stability with a 92.7% retention after 200 cycles and an excellent rate capability of 149.1 mAh g−1 at 10 C, achieved by adding only 0.5% of the production cost. This study unlocks the possibilities of achieving outstanding performance for ultrahigh Ni cathode by spending minimum cost through the facile surface chemistry method.
Methodology to evaluate design modifications intended to eliminate frosting and high discharge temperatures in air-source heat pumps (ASHPs) in cold climates
(Elsevier, 2024-06-01) Gollamudi, Siddhartha; Krishnan, Easwaran N; Fauchoux, Melanie; Ramin, Hadi; Joseph, Albin; Simonson, Carey
Air-source heat pumps (ASHPs) operating in cold climates experience problems with frosting and high refrigerant temperatures. These problems increase energy consumption, and their severity depends on the climatic conditions. In the present paper, a methodology for identifying the prevailing problem between frosting and high discharge temperatures is presented. Three performance indices, the frosting index (FI), the discharge index (DI), and the total loss index (TLI), are proposed to quantify the impacts of frosting and high discharge temperatures on the annual performance of ASHPs in different climatic conditions. The FI and DI show which problem (frosting or high discharge temperature) dominates, and the TLI indicates the combined effect of frosting and high discharge temperatures on the performance of an ASHP. A thermodynamic model of an ASHP coupled with the TRNSYS building simulation tool is used to estimate the performance of an ASHP and the proposed loss indices to estimate the impact of both frosting and high discharge temperatures for 45 cities in Canada. The results can be extended to other parts of the world that experience similar climatic conditions The results reveal that in cities in ASHRAE climatic zones 5 and 6 (classified as cold regions) where the ambient air temperatures are predominantly between −15 °C to 6 °C, ASHPs are heavily impacted by frosting. The problem of high discharge temperatures in ASHPs is predominant in cities in climate zones 7 and 8 (classified as very cold and subarctic regions) where the temperatures are frequently below −20 °C in winter. Among the cities considered, St. John, NL has the highest fraction of heating hours experiencing frosting (90 %), where the annual increase in energy consumption due to frosting is 13.5 % of the annual heating energy consumption. The highest annual increase in energy consumption due to high discharge temperatures is in Isachsen, NU (zone 8), where the increase is 30 % of the annual heating energy consumption. Based on the proposed indices, another index called the performance gain index (PGI) is created, which can be used as a first step to assess the energy-saving potential of design modifications applied to ASHPs to solve the problems of frosting and high discharge temperatures. The PGI will aid in developing climate specific ASHPs. One possible design modificationis the use of a two-stage ASHP with an economizer. It is observed that the two-stage ASHP with economizer can mitigate high discharge temperatures and improve performance in very cold and subarctic regions (zones 7 and 8). However, it is not as beneficial in zones 5 and 6, where the impact of high discharge temperatures on performance is minimal and frosting dominates. Finally, a case study, using the PGI to evaluate the economic and environmental effectiveness of a two-stage ASHP with economizer is presented for the city of Saskatoon.
Energy recovery ventilators to combat indoor airborne disease transmission: A Sustainable approach
(Taylor & Francis, 2024-09-17) Annadurai, Gurubalan; Mathews, Ashwin Joseph; Krishnan, Easwaran Nampoothiry; Gollamudi, Siddhartha; Simonson, Carey
Ventilation plays a crucial role in preventing indoor airborne disease transmission. Nevertheless, ventilation increases the energy consumption of heating, ventilation, and air conditioning (HVAC) systems. Therefore, energy efficiency measures or alternative methods must be adopted to reduce the energy demand of HVAC systems which is necessary to achieve sustainability in the building sector. The present study proposes a method of utilizing an Energy Recovery Ventilator (ERV) to provide supplementary ventilation to reduce the airborne disease transmission. The proposed method is tested for an office building with one source room (with an infected occupant) and two connected rooms (no infection source). The contributions of the present study are (i) the development and verification of a new supplement ventilation method using ERV to reduce the probability of infection from airborne pathogens and (ii) providing the economic and environmental benefits of the proposed method to promote its adaption by the building managers/HVAC engineers. The results of the present study show that the proposed method can reduce the probability of infection by 10 to 40% and demonstrate that utilizing ERV is the sustainable and economical method to improve ventilation to reduce indoor airborne disease transmission.
Investigation of the Filling of a Spherical Pore Body with a Nonwetting Fluid: A Modeling Approach and Computational Fluid Dynamics analysis
(Springer, 2024-07-23) Salama, Amgad; Kou, Jisheng; Shuyu, Sun; Hefny, Mahmoud
Understanding the dynamics of the filling process of a pore body with a nonwetting fluid is important in the context of dynamic pore network models and others. It can justify many of the assumptions behind the different rules that describe how the network behaves during imbibition and drainage processes. It also provides insight into the different regimes pertinent to this system. The filling process starts with the contact line pinning at the pore entrance. Three regimes can be identified during the filling process that is related to how the contact line advances. In the first two regimes, the contact line pins at the pore entrance while the emerging droplet develops, and in the third one, the contact line departs the entrance of the pore and advances along the pore surface. During the first regime, which is brief, the curvature of the meniscus increases, and likewise, the corresponding capillary pressure, while in the other two regimes, the curvature decreases and so does the capillary pressure. Such behavior results in the rate at which the nonwetting fluid invades the pore to change. It initially decreases, then increases as the meniscus advances. The radius of curvature of the meniscus, eventually, increases to infinity for which the interface assumes a flat configuration. A one-dimensional modeling approach is developed that accounts for all these regimes. The model also considers the two immiscible fluids over a wide spectrum of contrast in viscosity. Information about the mean velocity of the invading fluid, the location of the contact line, the radius of curvature of the meniscus, the volume of the emerging droplet, and several others are among the details that the model provides. A computational fluid dynamics (CFD) simulation has also been considered to confirm the proposed fates of the interface and to provide a framework for comparisons. The results of the validation process show, generally, a very good match between the model and the CFD analysis.
A Comprehensive Review of Dehumidifiers and Regenerators for Liquid Desiccant Air Conditioning System
(Elsevier, 2021-07) A, Gurubalan; Simonson, Carey J
Liquid desiccant air conditioning systems (LDAS) are an energy-efficient and eco-friendly alternative to conventional air conditioning systems. The performance of a LDAS significantly depends on its simultaneous heat and mass transfer components, namely dehumidifier and regenerator. These components are referred to as liquid desiccant energy exchangers (LDEEs) since the working fluids (air and desiccant) exchange both heat and moisture. There has been a lot of research on LDEEs over the last two decades to improve their performance, thereby enhancing the efficiency of the LDAS. The main objective of this comprehensive review paper is to summarize the developments of LDEEs. The desiccant material, and design, operating, and performance parameters of LDEEs are explained in detail. Even though a lot of research has been done on LDEEs, they are not much utilized in the practical heating, ventilation, and air conditioning (HVAC) systems. To address this issue, future research should prioritize its focus on (i) practical problems of LDEEs such as cross contamination, and leakage and blockage of the membrane, (ii) long term performance study in the practical systems, (iii) noncorrosive and inexpensive solution, (iv) compatible material for efficient heat and mass transfer, and (v) generalized design and performance control methodology. The discussions presented in this communication will be useful to ascertain the crucial research gaps that need to be addressed by future research studies.
Transient sensor errors and their impact on fixed-bed regenerator (FBR) testing standards
(Taylor and Francis, 2020-12) Ramin, Hadi; Krishnan, Easwaran K; Gurubalan, Annadurai; Alabi, Wahab O; Simonson, Carey J
Fixed-bed regenerators (FBRs) are a favorable option for energy recovery in building HVAC systems due to their high sensible effectiveness. Unlike other types of energy recovery exchangers, the air temperature at the outlet of FBRs varies with time, which creates challenges when measuring the outlet temperature and effectiveness of FBRs since the actual outlet air temperature will include the transient response of the FBR and the temperature sensor. In this article, a validated numerical model of FBRs that takes into account the sensor response is used to quantify the temperature and effectiveness errors that result due to sensors’ response characteristics over a wide range of design parameters. The main contributions of this article are the practical recommendations for the temperature measurement for different types of FBRs developed for HVAC applications. The recommendations presented in this article could be implemented in future versions of the current standards (ASHRAE 84 and CSA C439-18 standards) for performance testing of air-to-air energy exchangers.
A transient numerical model for desiccant-coated fixed-bed regenerators and compensation for transient sensor errors
(Taylor and Francis, 2021-12) Ramin, Hadi; Krishnan, Easwaran K; Gurubalan, A; Simonson, Carey J
Desiccant-coated fixed-bed regenerators (FBRs) can achieve high effectiveness due to high ratio of energy transfer area to volume, and therefore, they are favourable air-to-air energy recovery exchangers for HVAC systems. However, unlike other types of energy recovery exchangers, the air properties (i.e., temperature and humidity) at the outlet of FBRs vary with time. The variations in outlet airflow properties can cause errors in measurements because the measurements include the FBR and sensors transient responses. In this paper, a numerical model is developed to evaluate the performance of desiccant-coated FBRs and their transient operation. The model consists of an exchanger model (FBR model) and sensor (temperature and humidity) models to distinguish the actual performance of the FBR alone from the measured performance, which includes both the FBR and the sensor's response. The model is validated with experimental measurements and available results in the literature. The model can decouple the measured response of the FBR and sensors to predict the FBR performance. This paper's main contribution is an insight into the complex heat and mass transfer processes in desiccant-coated FBRs and measurement sensors. The results of this paper could be used to provide practical recommendations for humidity measurements of different types of desiccant-coated FBRs developed for HVAC applications. Furthermore, the measurement requirements in the current testing standards (ASHRAE 84 and CSA C439-18 standards) for FBRs are examined. Recommendations from this paper could be implemented in future versions of these standards.
Experimental Investigation on Thermo-Hydraulic Performance of Triangular Cross-Corrugated Flow Passages
(Elsevier, 2021-03) Krishnan, Easwaran N; Ramin, Hadi; Guruabalan, A; Simonson, Carey J
Heat exchangers made of corrugated flow passages generally have better thermo-hydraulic performance compared to parallel flow passages. The corrugation angle (), corrugation pattern, and the ratio of depth to pitch (hch/Pch) are critical geometrical parameters influencing the heat transfer and pressure drop in corrugated flow passages. This paper experimentally investigates heat transfer and pressure drop characteristics of triangular-shaped cross-corrugated flow passages for the range of 25°<<75° and 0.13
Suitability of bio-desiccants for energy wheels in HVAC applications
(Elsevier, 2021-12) Alabi, Wahab O; Krishanan, Easwaran N; Karoyo, Abdalla H; Dehabadi, Leila; Wilson, Lee D; Simonson, Carey J
This paper investigates the suitability of bio-desiccants for moisture recovery in energy wheels. Bio-desiccants are environment-friendly materials that have high water vapor adsorption capacities. The main contribution of this paper is that it reports the latent effectiveness of flax-fiber (bio-desiccant) coated energy wheels for a wide range of operating conditions and compares the effectiveness of the flax-fiber wheels with wheels that are coated with commercially available desiccants and other biomaterials. The moisture transfer performance of a flax-fiber coated exchanger is determined using a small-scale test facility and two different experimental methods: single step change tests and cyclic tests. The test results are used to verify the applicability of an effectiveness correlation from the literature. Using the energy wheel correlation and the sorption isotherms, the latent effectiveness of commercially available energy wheels coated with molecular sieve, ion exchange resin and silica gel desiccants are obtained and compared with that of bio-desiccants (flax fiber and starch particles). The highest latent effectiveness is obtained for silica gel followed by starch particles, ion exchange resin, flax-fiber and molecular sieve. The results from this study will be useful in research and development of bio-materials for energy recovery systems for building applications.
Development of a Small-Scale Test Facility for Effectiveness Evaluation of Fixed-Bed Regenerators
(Elsevier, 2020-06-25) Krishnan, Easwaran Nampoothiry; Ramin, Hadi; Shakouri, Mohsen; Wilson, Lee D; Simonson, Carey
Fixed-bed regenerators (FBR) transfer heat (and moisture) between supply and exhaust air streams in heating, ventilating and air conditioning (HVAC) systems to reduce building energy consumption. This paper presents a new small-scale testing facility to evaluate the performance (i.e. sensible effectiveness) of FBRs for HVAC applications. The major contributions of this paper are: development of a new small-scale experimental facility and methodology for testing FBRs, quantification of uncertainties, and verification of small-scale test data over a large range of FBR design conditions. A numerical model and two well-known design correlations are used to verify the results and testing methodology. The advantages of small-scale testing are that it requires low volume of conditioned airflow, has low uncertainty, requires less exchanger material and has a low cost per test. Moreover, the small-scale testing methodology of FBR would benefit heat exchanger manufacturers to perform detailed sensitivity studies and optimize the exchanger performance over a wide range of design and operating parameters prior to the fabrication of full-scale exchangers.
A TRANSIENT NUMERICAL MODEL FOR SENSIBLE FIXED-BED REGENERATOR IN HVAC APPLICATIONS
(Elsevier, 2021-06-16) Ramin, Hadi
Characterization of the evolution of crystallization fouling in membranes
(ACS, 2018-12) Olufade, A.O.; Simonson, C.J.
Effects of Variations in Incident Heat Flux When Using Cone Calorimeter Test Data for Prediction of Full-Scale Heat Release Rates of Polyurethane Foam
(Wiley, 2016) Robson, Luke; Torvi, David; Obach, Matthew; Weckman, Elizabeth
The development of methods to predict full-scale fire behaviour using small-scale test data is of great interest to the fire community. This study evaluated the ability of one model, originally developed during the European Combustion Behaviour of Upholstered Furniture (CBUF) project, to predict heat release rates. Polyurethane foam specimens were tested in the furniture calorimeter using both centre and edge ignition locations. Input data was obtained using cone calorimeter tests and infrared video-based flame area measurements. Two particular issues were investigated: how variations in incident heat flux in cone calorimeter tests impact heat release rate predictions, and the ability of the model to predict results for different foam thicknesses. Heat release rate predictions showed good agreement with experimental results, particularly during the growth phase of the fire. The model was more successful in predicting results for edge ignition tests than for centre ignition tests, and in predicting results for thinner foams. Results indicated that, due to sensitivity of the burning behaviour to foam specimen geometry and ignition location, a single incident heat flux could not be specified for generating input for the CBUF model. Potential methods to determine appropriate cone calorimeter input for various geometries and ignition locations are discussed.

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