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    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.
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    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.
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    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.
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    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
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    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.
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    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.
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    Characterization of the evolution of crystallization fouling in membranes
    (ACS, 2018-12) Olufade, A.O.; Simonson, C.J.
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    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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    Predicting Mechanical Strength of In-Use Firefighter Protective Clothing using Near-Infrared Spectroscopy
    (Springer, 2018) Rezazadeh, Moein; Bespflug, Christopher; Torvi, David; Noble, Scott; Fulton, Mackenzie
    The exact lifespan of in-use firefighter protective clothing is difficult to predict due to the large variations in use between individual garments. Furthermore, testing methods used to evaluate new protective clothing are destructive in nature and could not be applied to in-use garments. Various non-destructive techniques have been proposed for the evaluation of in-use clothing, each possessing its own advantages and disadvantages. The ability of near-infrared spectroscopy to predict the tensile strength of thermally aged fabrics used in protective clothing for wildland firefighters and other workers is investigated here. Fabrics were exposed to heat fluxes from 10 to 40 kW/m^2 for various durations using the cone calorimeter, after which the tensile strength of the fabrics was measured. Temperatures measured during the exposures and results of thermal gravimetric analysis tests were used to interpret changes in tensile strength. Multivariate linear regression was used to develop correlations between the tensile strength and the reflectance values measured between 1500 and 2500 nm for new and thermally aged fabrics. It was found that models based on reflectance measurements made at as few as three wavelengths could be used to estimate the tensile strength of the thermally aged specimens.