Household dishwashers must address several performance goals: maximize washing and drying performance, while minimizing cycle duration, energy consumption, and water consumption. This study develops and examines a novel thermoelectric heating and cooling (TEHC) system with thermal energy storage applied to a household dishwasher (DW), aiming to improve the energy and drying performance of a commercially-available dishwasher while maintaining its washing performance, water consumption, and cycle duration. Experimental testing conducted on the novel TEHC-DW system demonstrates an 8.7% reduction in total energy consumption, lowering the per-cycle usage to 0.952 kWh, and a 40% reduction in energy consumption for internal water heating. The novel TEHC-DW system also demonstrates better drying performance, shortening the drying time by 42% to reach the same remaining moisture content as a commercially-available system. Additionally, a resistance-capacitance network model is developed that predicts total drying time, total energy consumption, and the highest temperature reached in the tub (53.4 degrees C). The model accuracy is validated with experimental data (within +/- 1 K), and the model functions as a design tool via a parametric study to evaluate the nextgeneration design and the effect of the number of thermoelectric modules and thermoelectric driving force (i. e., current). Overall, this study demonstrates the potential for TEHC technology to improve energy efficiency and drying performance in household dishwashers.

Direct air capture (DAC), which captures CO2 from ambient air, is a critical technology to reduce greenhouse gases in the atmosphere in order to avoid climate disasters. Due to the relatively low concentration of CO2 (400 ppm), a large amount of air needs to be moved through DAC devices, which requires lots of energy. Currently, DAC technologies are deployed mainly in centralized systems and require extensive infrastructure and initial capital cost. A potential solution is to utilize existing infrastructure for DAC. In this study, we propose a distributed DAC system that utilizes existing commercial rooftop heating and air conditioning (HVAC) units to capture CO2 from the air. There are approximately 15 million such units already installed on commercial buildings in the United States, and they move a large amount of air every day. Adding DAC functionality to these units will significantly reduce the cost of infrastructure and operation. A modular approach was used to introduce DAC into a rooftop unit. Modules filled with triethylenetetramine-functionalized polyacrylonitrile sheets were developed and installed on the condenser coil side of the rooftop unit. The rooftop unit with DAC functions effectively captured CO2 from the air, and the addition of the DAC modules had little effect on the unit's original functionality. A preliminary techno-economic analysis was also conducted, and the results potentially suggest that utilizing existing commercial rooftop units for carbon capture is a feasible approach to reducing greenhouse gases. Direct air capture (DAC), which captures CO2 from ambient air, is a critical technology to reduce greenhouse gases in the atmosphere in order to avoid climate disasters.

In recent years, thermal energy storage (TES) has gained attention for its role in enhancing renewable energy solutions and sustainable energy consumption. The usage of strontium chloride hexahydrate (SCH), graphene nanoplatelet (GNP), and cellulose nanofibril (CNF) additives were investigated to enhance the performance of calcium chloride hexahydrate (CCH) based on the melting/solidification behavior for TES applications. In this work, we develop a promising phase-change-material (PCM) formulation by introducing these additives that reduce supercooling, improve the thermal conductivity and stabilizing the energy storage capacity of CCH. Rheological characterizations demonstrated that the addition of 1 wt% of CNF into CCH produced the required improvement in viscosity and boosted solid-like rheological behavior. Structural characterizations show a physical mixing of the materials within the PCM composites. Our observations show that the amphiphilicity of CNF enables the surface attachment to GNP via hydrophobic interactions providing effective dispersion of GNP throughout the PCM composite. The addition of a nucleating agent, SCH decreased the degree of supercooling of similar to 20 g of CCH from >20 degrees C to 3 degrees C at a cooling rate of 5 degrees C/min. Thermal characterization showed the resulting PCM composite has a latent heat of melting of 186 Jg(-1), phase change temperature of 32 degrees C, and stable thermal properties after being subjected to 70 melt-freeze cycles. Adding CNF and GNP to pure CCH increased its thermal conductivity by 76 %. The high thermal conductivity of GNP and its effective dispersion by CNF is responsible for this enhancement. The study highlights the use of biodegradable nanocellulose for the preparation of sustainable PCM composites with improved performance. These PCM composites are scalable, they have potential to increase energy efficiency and revolutionalize the heating/cooling applications in buildings and other TES systems.

The phase behavior of ionic liquids and ammonia is criticaldueto their application in various fields such as sorption-based heating/coolingcycles and direct ammonia capture. To date, various ionic liquidshave been developed and investigated to enhance the solubility ofammonia without compromising the reversibility due to recycling concernsand various thermodynamic models have been used to correlate the experimentalvapor-liquid equilibria data. Surely, high ammonia sorptioncapacities are required and understanding the interaction betweenammonia and ionic liquids can lead to synthesizing targeted ionicliquids for ammonia. In this study, we developed an extended Flory-Huggins model on ammonia and imidazolium-based ionicliquid systems, where both combinatorial and residual terms are considered,to understand the interaction between ammonia and ionic liquids. Theresults showed that the nonidealities in ammonia and imidazolium-basedIL mixtures are due to both entropic and enthalpic contributions.Therefore, increasing the size of the IL would not be enough to achievehigher solubilities. A deeper understanding of the molecular-levelinteraction between ionic liquids and ammonia can be investigatedvia molecular simulations.

The worldwide increasing energy demand and 2050 net zero carbon target urge the globe to solve the energy challenge. Thermal Energy Storage (TES) has received significant attention in recent years as TES can be integrated into heating, ventilation, and air-conditioning systems where the energy would be stored during low-demand times and dispatched during high-demand times, resulting in controlling the peak load and improving energy savings. Material development is an integral part of TES. Salt hydrates are appealing due to cost-effectiveness, low- to no toxicity, and their high melting enthalpy, where energy is stored as latent heat. However, most salt hydrates are prone to incongruent melting (i.e., phase separation upon melting), which results in poor stability and large supercooling. In this study, we produced a highly stable novel energy storage material at a composition of 32 wt% sodium sulfate decahydrate, 52 wt% sodium phosphate dibasic dodecahydrate, 12 wt% milled expanded graphite, and 4 wt% borax. The material has a melting temperature of 28°C and an energy storage capacity of 167 kJ/kg with a supercooling of less than 3°C. The system showed no loss in energy storage performance after 150 cycles. The findings suggest that the novel energy storage material developed in this might be utilized in building heating and cooling applications.

Refrigerant maldistribution is a common issue in microchannel heat exchangers. Refrigerant maldistribution can have significant negative effects on the heat transfer performance and increase the pressure drop, leading to increased superheat temperature at the outlet and increased compressor work, lowering system efficiency. A novel piezoelectric-driven magnetic actuator (PEDMA) was fabricated and inserted into the inlet header of the microchannel evaporator, with the goal of improving the non-uniformity of the flow distribution by regulating the flow in the header to the microchannels. Two prototype PEDMA designs were tested and showed significant impact on the refrigerant flow in the region of actuation. In the first design, the experimental data showed superheat reductions up to 9 degrees C when the individual channel temperatures were measured. The second design redistributed the refrigerant such that a 1% increase in capacity was calculated for the whole heat exchanger without significantly impacting the heating efficiency. The experimental results demonstrate the successful operation of the PEDMA devices and represent a new method of active flow distribution control which is based on a simple design with minimal additional energy consumption, and which can be inserted into microchannel heat exchanger headers to potentially relieve the refrigerant maldistribution.

Heating and cooling systems in building infrastructure utilize conventional materials that account for a considerable amount of energy usage and waste. Phase change material (PCM) is considered a promising candidate for thermal energy storage that can improve energy efficiency in building systems. Here, a novel salt hydrate-based PCM composite with high energy storage capacity, relatively higher thermal conductivity, and excellent thermal cycling stability was designed and developed. The thermal cycling stability of the PCM composite was enhanced by using dextran sulfate sodium (DSS) salt as a polyelectrolyte additive, which significantly reduced the phase segregation of salt hydrate. The energy storage capacity and the thermal conductivity of the composite were enhanced by the addition of various graphitic materials along with Borax nucleator. A significant increase in thermal cycling stability was observed for the DSS-modified composite, with over 100 thermal cycles without degradation. The final PCM composite exhibited as much as 290% increase in energy storage capacity relative to the pure salt hydrate, and approximately 20% increase in thermal conductivity. In addition, the PCM composite developed can be produced at larger scale, and can potentially change the future of heating/cooling system in building infrastructure.

Air dehumidification is essential since excess moisture in the buildings causes discomfort to the occupants, encourages the production of air pathogens such as mold or mildew, and causes corrosion and rotting that degrade building materials. Existing moisture removal processes are mainly focused on condensation and desiccant (liquid or solid) techniques with direct contact between air and desiccant. However, these methods are energy-intensive, or desiccant might be lost or cause corrosion in the process. The main objective of this study is to investigate an ionic liquid-based liquid desiccant absorber based on a membrane fiber bundle. A novel membrane contactor system was fabricated with a bundle of 10,000 polypropylene fibers. Each fiber has 0.3 micron outer diameter, with ionic liquid flowing inside, and air flowing outside. The fibers provide a high contact area among phases: 1.4 m contact surface area in a 0.00015 m volume (9,333 m/m ratio of surface area to volume). The ionic liquid as a sorbent has selectivity for water vapor (i.e., the ionic liquid has higher affinity for water vapor) prevents the loss of solvent in the operation due to negligible volatility, provides fast diffusion due to low viscosity compared to common ionic liquids, and has high affinity and solubility in water. The dehumidification capacity of the prototype membrane system was experimentally investigated using six modules with 10,000 fibers each. The experimental results show that the ionic-liquid based membrane system can effectively remove excess moisture from the air. The novel fiber bundle dehumidification system has a total system volume of 0.00798 m (7.98 L) and active heat and mass transfer surface area of 8.4 m. It achieved an average dehumidification of 320 ± 25 W with a volumetric air flowrate of 3.1 m/min (108 ft/min). Notice: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-publicaccess-plan). 18 International Refrigeration and Air Conditioning Conference at Purdue, May 24-28, 2021

Grocery stores provide essential services to communities all over the world. The COVID-19 pandemic has necessitated better understanding of the transport and dynamics of aerosolized viruses, particularly for the assessment of infection transmission risk within grocery stores and for other providers of essential services. In this study, a 3D computational fluid dynamics model was developed for a medium-sized grocery store in the United States using Ansys Fluent software. Different cases were simulated of a single infected person releasing viral aerosols with and without wearing a face mask. Results showed characteristic airflow and temperature distribution patterns inside the store that can drive the indoor dispersal of viral aerosols. Unsteady spatial distribution of mean age of air was used as a metric to indirectly quantify areas of higher risk of infection. Several factors affected the localization of suspended viral aerosols. Major recirculation patterns in certain locations of the store caused by persistent eddies were primarily attributed to increased mean age of air. The maximum mean age of air in the grocery store was found to be less than 30 min. Simulation results indicate that, without wearing a face mask, the aerosol particles released from a coughing infected person can be spread throughout nearly one-quarter of the grocery store in less than 6 min. The source-control strategy with a face mask showed significant reduction of viral aerosols being dispersed indoors.

The first vapor liquid equilibrium (VLE) measurements for the binary systems of ammonia (NH3) and three imidazolium-based ionic liquids (ILs) have been successfully measured using a gravimetric microbalance. ILs 1-butyl-3-methylimidazolium hexafluorophosphate ([C(4)C(1)im] [PF6]), 1-butyl-3-methylimidazolium tetrafluorob orate ([C4C1MI] [BF4]), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)C(1)im][NTf2]) were measured at temperatures of 283.15, 298.15, 323.15, and 348.15 K and at pressures up to 0.7 MPa using the new Hiden XEMIS gravimetric microbalance. The VLE data were correlated using the Peng-Robinson equation of state and the Non-Random Two Liquid (NRTL) activity coefficient models. Both models are in excellent agreement with the experimental data. The Fickian diffusivities of NH3 in imidazolium-based ILs were obtained fitting experimental concentration to the one-dimensional (1D) mass diffusion equation, and found to be about 3 to 5 times lower than the diffusion of NH3 in water (H2O). The semitheoretical Stokes-Einstein equation was used to model diffusivities and to obtain the diffusing radius of NH3 in imidazolium-based ILs.

The high-pressure vapor-liquid equilibrium for the binary systems of carbon dioxide (CO2) and a series of 1-alkyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids ([C(n)C(1)p(yr)][NTf2] (n = 3,4,6)) are reported at 298.15, 318.15, and 338.15 K and at pressures of up to 20 MPa. Experiments were conducted using gravimetric (IGA and XEMIS microbalances) and volumetric (high-pressure view cell) methods. The solubility of CO2 in pyrrolidinium ionic liquids increases with decreasing temperature and increasing pressure. The CO2 solubility also slightly increases with increases in alkyl chain length on the pyrrolidinium cation. The molar volume and volume expansion of CO2 + IL mixtures are also reported. The Fickian diffusion of CO2 in pyrrolidinium-based ionic liquids (similar to 10(-10) m(2).s(-1)) was calculated at pressures of up to 2 MPa and found to be slightly lower than the diffusivity of CO2 in an imidazolium-based ionic liquid with the [NTf2] anion.

Binary liquid-liquid equilibria (LLE) for mixtures of dihydroxy alcohols and three imidazolium-based ionic liquids (ILs) were measured. The dihydroxy alcohols were 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol, and the ILs were 1-ethyl-3-methyimidazolium tetrafluoroborate ([C(2)C(1)im][BF4]), 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide ([C(2)C(1)im][NTf2]), and 1-ethyl-3-methylimidazolium 1,1,2,2-tetrafluoroethanesulfonate ([C(2)C(1)im][TFES]). The experimental LLE data were well correlated using the nonrandom two-liquid (NRTL) activity coefficient model. All binary diol systems with [C(2)C(1)im][BF4] or [C(2)C(1)im][NTf2] have an upper critical solution temperature (UCST) between 310 and 360 K. An equimolar mixture of diols and [C(2)C(1)im][TFES] showed complete miscibility between 293.15 and 373.15 K. An increase in the alkyl chain length of the dihydroxy alcohols and/or changing the anion from [BF4-] to [NTf2 ] for a given [C(2)C(1)im] cation results in an increase in the UCST. The excess molar volume of diols with ILs was in most cases larger than those of ordinary solutions.

The beam balance is one of the oldest known measuring instruments. Until the 20th century, balances had been the most sensitive and precise instruments used for scientific measurements. The original balances used a beam supported at the center with pans hung from cords on both ends. The modern electronic beam balances still resemble those original designs; however, the resolution, accuracy, and capabilities have been significantly improved. This review provides a short introduction to the history of beam balances followed by a detailed description of three gravimetric microbalances manufactured by Hiden Isochema for measuring gas and vapor sorption in a variety of materials.