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Articles 6361 - 6390 of 50088
Full-Text Articles in Entire DC Network
Experimental Study Of The Heat Pump With Variable Speed Compressor For Domestic Heat Load Applications, Muhammad Abid, Neil Hewitt, Ming Jun Huang, Christopher Wilson, Donal Cotter
Experimental Study Of The Heat Pump With Variable Speed Compressor For Domestic Heat Load Applications, Muhammad Abid, Neil Hewitt, Ming Jun Huang, Christopher Wilson, Donal Cotter
International Compressor Engineering Conference
Capacity control for heat pump (HP) systems is essential to efficiently meet variable heating loads in domestic buildings. A low-to-medium temperature hot water supply within a 30 oC-55 oC range is commonly required for domestic heating load applications. In this study, the performance of a variable speed air source heat pump (ASHP) system was studied in the laboratory under a series of ambient conditions at -2 oC, 2 oC, 7 oC and 15oC, examining performance at different water supplying temperatures (WST) of 30 oC, 35 oC, 40 oC, 45 oC, 50 oC, and 55 oC. The performance of the variable …
Electrochemical Compression Of Ammonia/Hydrogen Blends For Heat Pump Application, Ashish Chouhan, Bamdad Bahar, Ajay K. Prasad
Electrochemical Compression Of Ammonia/Hydrogen Blends For Heat Pump Application, Ashish Chouhan, Bamdad Bahar, Ajay K. Prasad
International Compressor Engineering Conference
Ammonia is widely used as a refrigerant in air conditioning, food preservation and for fuel storage purposes. Ammonia is an attractive candidate for electrochemical compression (ECC). Electrochemical compressors can be an ideal replacement for mechanical compressors because of noiseless operation, higher efficiencies at lower voltages and the ability to operate without the use of Global Warming Potential (GWP) working fluids. This paper explores the electrochemical compression of ammonia with hydrogen as a carrier gas, using fuel cell type hardware. A perfluorosulfonic acid (PFSA) membrane allows the transfer of ammonia, using hydrogen as a carrier gas, by the conduction of NH4+ …
Quantitative And Qualitative Evaluation Of Various Positive-Displacement Compressor Modeling Platforms, Mohsin Mohsin Tanveer, Craig R. Bradshaw
Quantitative And Qualitative Evaluation Of Various Positive-Displacement Compressor Modeling Platforms, Mohsin Mohsin Tanveer, Craig R. Bradshaw
International Compressor Engineering Conference
Several regulatory measures aimed to mitigate climate change are forcing compressor manufacturers to replace current refrigerants to those with low Global Warming Potential (GWP). New refrigerants need to be evaluated to ensure adequate efficiency for use in modern products. Evaluation can be done heuristically, which is expensive and timeconsuming, while a carefully designed simulation model can provide similar outcomes for a significantly reduced cost. This paper presents a comparison between various userdeveloped and existing reciprocating compressor models to assist in the selection of a suitable modeling platform for a wideranging study. The reciprocating compressor is selected because of the simplicity …
A Generalized Approach For Automated Compressor Performance Mapping Using Artificial Neural Network, Jie Ma, Xin Ding, W. Travis Horton, Davide Ziviani
A Generalized Approach For Automated Compressor Performance Mapping Using Artificial Neural Network, Jie Ma, Xin Ding, W. Travis Horton, Davide Ziviani
International Compressor Engineering Conference
In the last decades, several research and development efforts led to new compressor technologies that have been successfully introduced into market such as hermetic compressors with variable-speed motors, compressors with economization lines (both vapor and liquid injection lines), hermetic linear compressors, novel capacity modulations, and oil-flooding among others. During the process of implementing new compressor technologies, performance mapping is essential to predict the system behavior across different operating conditions. However, current standard AHRI-540 for compressor performance rating utilizes a 10-coefficient polynomial model that has severe limitations to include compressor enhancement technologies and variable operating range. In addition, it is common …
Investigation Of Back-Diffusion Losses In An Electrochemical Hydrogen Compressor, Ashish Chouhan, Bamdad Bahar, Ajay K. Prasad
Investigation Of Back-Diffusion Losses In An Electrochemical Hydrogen Compressor, Ashish Chouhan, Bamdad Bahar, Ajay K. Prasad
International Compressor Engineering Conference
Hydrogen offers the potential to decarbonize the automotive and stationary power sectors and is therefore expected to play an increasingly significant role in meeting global energy demand. However, due to its low volumetric and gravimetric energy densities, it is important to find methods to efficiently store hydrogen in order to grow the hydrogen economy. Storing hydrogen as a compressed gas could be achieved by electrochemical compression (ECC), which is a membrane-based alternative to conventional mechanical compressors. ECC can be superior to mechanical compressors because of its higher efficiency, lack of moving parts and noiseless operation. Here, we report on the …
Development Of State-Of-The-Art Experimental Technique To Investigate Temperature Field In Leakage Flows Of Positive Displacement Machines, Brijeshkumar Patel, Ahmed Kovacevic, Md Nahinul Alam, Alexandros Charogiannis
Development Of State-Of-The-Art Experimental Technique To Investigate Temperature Field In Leakage Flows Of Positive Displacement Machines, Brijeshkumar Patel, Ahmed Kovacevic, Md Nahinul Alam, Alexandros Charogiannis
International Compressor Engineering Conference
Investigation of leakage flows in oil-free rotary positive displacement machines (PDMs) is necessary to get a real insight into attributes of leakage flows. Experimental study of heat transfer in the leakage flows of the oil-free positive displacement machines is challenging. The primary reason is complexities associated with actual machine running condition such as extremely small (micron-size) clearance gap, high speed of rotors, optical access of flows etc. Therefore, this studypresents the development of state-of-the-art experimentalsetup usingPlanar La ser-Induced Fluorescence (PLIF) technique to visualize the temperature field in the clearance flows of rotary machines. This study considers Roots blower to implement …
An Overset Mesh Methodology For Cfd Modelling Of Rotary Compressors, Wai Chang Poh, Kim Tiow Ooi, Basman Elhadidi
An Overset Mesh Methodology For Cfd Modelling Of Rotary Compressors, Wai Chang Poh, Kim Tiow Ooi, Basman Elhadidi
International Compressor Engineering Conference
Full 2D and 3D unsteady CFD simulations are gradually replacing the widely used lumped parameters simulations for rotary compressors. Lumped parameter models predict the overall thermodynamic processes; however, they cannot reveal the spatial and temporal variations in the working chamber and account for complex fluid interactions and losses. The complex and continuously deforming working chamber geometry is challenging for CFD. The overset method has been implemented here for the simulation of a 2D Coupled Vane Compressor (CVC). The method was compared to a dynamic mesh formulation using a remeshing technique and has shown; (1) it is 3-4 times faster computationally …
Cfd Analysis Of An Orc Vane Expander Using Openfoam Solver, Sham Ramchandra Rane, Giuseppe Bianchi, Ahmed Kovačević, Roberto Cipollone
Cfd Analysis Of An Orc Vane Expander Using Openfoam Solver, Sham Ramchandra Rane, Giuseppe Bianchi, Ahmed Kovačević, Roberto Cipollone
International Compressor Engineering Conference
Recent studies on the use of 3D Computational Fluid Dynamics (CFD) for the analysis and design of sliding vane machines has proved beneficial for the detailed evaluation and optimisation of the vane expanders for a given working fluid and operating condition. The authors have earlier developed a customised rotor grid generator for integration with commercial CFD solvers and validated it for use in typical small-scale ORC expanders for waste heat recovery. In this paper, this customised grid generation is extended to an open source CFD solver OpenFOAM, by using a connectivity methodology originally developed for roots blower and twin-screw machines. …
Carbon Dioxide Medium Temperature Refrigeration System With Thermal Storage, Kirill Ignatiev, Kyaw Wynn
Carbon Dioxide Medium Temperature Refrigeration System With Thermal Storage, Kirill Ignatiev, Kyaw Wynn
International Refrigeration and Air Conditioning Conference
Application of Carbon Dioxide as a natural, non-toxic, non-flammable refrigerant in refrigeration systems is steadily gaining interest, especially in locations with moderate climate, like Europe or Canada. However, it is a well-known fact that at higher ambient conditions, when CO2 system operates in transcritical mode, system efficiency is substantially reduced. Currently, there is a large variety of different techniques aimed at the CO2 refrigeration system efficiency enhancement at transcritical operation, like vapor injection, ejectors, expanders, multi-stage compression with intercooling (and combinations thereof) to name a few. On the other hand, thermal storage devices are gaining popularity in many applications including …
A Non Symmetric Interfacial Area Density Formulation For Transcritical Co2 Ejectors, Egoi Ortego
A Non Symmetric Interfacial Area Density Formulation For Transcritical Co2 Ejectors, Egoi Ortego
International Refrigeration and Air Conditioning Conference
The reduction of global warming potential gases emissions in industrial refrigeration devices requires the development of efficient cycles using low GWP gases. The supercritical C02 cycle assisted by a transcritical two phase ejector is a nice example of such cycles. The design of such ejectors is not obvious and an intense development of performance prediction tools is observed in literature especially regarding two-phase CFD modeling. The two phase flow CFD models are limited today by their lack of flexibility and difficulties to empirically calibrate them. The main drawback of classical Hertz-Knudsen or HRM phase change models is their difficulty to …
Field Evaluation Of Solar Thermal Air Collectors, Zachary Schreiber, James Rieser, William Hutzel
Field Evaluation Of Solar Thermal Air Collectors, Zachary Schreiber, James Rieser, William Hutzel
International High Performance Buildings Conference
This paper documents the performance of three different active flat plate solar thermal air collectors that were designed, built, and installed on the roof of a university building. The three collectors circulate air and use small fans for capturing and delivering supplemental heat for the building. These collectors are part of a larger solar energy installation used in a university setting for teaching and research about renewable energy. Each collector has a different configuration to illustrate how a solar collector’s design impacts its ability to capture thermal energy. A web-based building automation system provides real time data on solar collector …
Technical And Economic Analysis Of A Residential Heat Pump With Photovoltaic Solar Panels In Self-Consumption For Space Heating, Cooling And Dhw Production, Pedro Jorquera Ferrat, Michèle Mondot
Technical And Economic Analysis Of A Residential Heat Pump With Photovoltaic Solar Panels In Self-Consumption For Space Heating, Cooling And Dhw Production, Pedro Jorquera Ferrat, Michèle Mondot
International High Performance Buildings Conference
Two different thermodynamic systems for space heating, cooling, and domestic hot water production coupled to photovoltaic panels have been studied. The aim is to assess the PV electricity self-consumption variation with the heat storage volume and the applied control strategy. Each system has been studied using a 1D unsteady state modelisation software to simulate its performance in a house complying with the French building code (RT2012) having a DHW demand according to ErP’s load profile M and with Paris weather data. The main parameters studied are the electricity consumption of the thermodynamic system, the seasonal performance factor (SPF), the self-consumption …
Demand Side Management And Battery Storage Utilization To Increase Pv Self-Consumption Of A Modulating Heat Pump, Maria Pinamonti, Alessandro Prada, Paolo Baggio
Demand Side Management And Battery Storage Utilization To Increase Pv Self-Consumption Of A Modulating Heat Pump, Maria Pinamonti, Alessandro Prada, Paolo Baggio
International High Performance Buildings Conference
The combination of photovoltaic (PV) systems and heat pumps for heating and cooling of buildings is a promising solution to increase the share of renewable energy in the residential sector. The interaction between the system components is fundamental to assure a high performance of the system. The level of PV energy self-consumption is strictly dependent on the control strategy applied to the system. The solar source is intermittent and it does not always match the building loads for heating and cooling. Furthermore, even the heating and cooling demands are strongly time-dependent in high performance buildings. For these reasons, an efficient …
Material Selection And Sizing Of A Thermoelectric Generator (Teg) For Power Generation In A Self-Powered Heating System, Tim J. Laclair, Kyle R. Gluesenkamp, Hsin Wang, Ahmad Abuheiba, Praveen Cheekatamarla, Sandeep Alavandi, Hamid Abbasi, David Cygan, Alexander Kirk, Uttam Ghoshal
Material Selection And Sizing Of A Thermoelectric Generator (Teg) For Power Generation In A Self-Powered Heating System, Tim J. Laclair, Kyle R. Gluesenkamp, Hsin Wang, Ahmad Abuheiba, Praveen Cheekatamarla, Sandeep Alavandi, Hamid Abbasi, David Cygan, Alexander Kirk, Uttam Ghoshal
International High Performance Buildings Conference
By employing the high temperature heat source to directly generate the electricity needed to power auxiliary systems in a natural gas furnace, boiler or hot water heater, a “self-powered” heating system can provide several benefits. Compared with a traditional furnace, boiler or hot water heater, when overall fuel utilization is kept constant, the self-powered system will have a higher primary energy efficiency, lower operating costs, and dramatically improved building safety and resilience during electric grid outages. Furthermore, a self-powered heating system only has a single utility connection – natural gas, without an electric connection – thus simplifying installation. A thermoelectric …
Community Heat Pump Systems Utilizing Oil-Free Compressor Technology, Drew Scott Turner, Davide Ziviani
Community Heat Pump Systems Utilizing Oil-Free Compressor Technology, Drew Scott Turner, Davide Ziviani
International High Performance Buildings Conference
The goal to decarbonize buildings is quickly driving growth in the adoption of heat pumps to replace fossil fuel-based heating equipment. The trend is significantly driven by the integration of renewables in the electric grid, also replacing fossil fuel-based sources, to in-turn drive decarbonization. The impact of this change is greater if also changing out end-use fossil fuel-based heating equipment to electric-driven. With the trend to heat pumps, there is a critical choice on both the scale and corresponding heat source. The heat pumps can be implemented with ambient air as the heat source or with other higher temperature/efficiency sources …
Effect Of Inlet Duct Design On Fan Performance Of Indoor Air Handling Units With Pull-Through Fan Configuration (Ashrae Rp-1743), Khaled I. Alghamdi, Christian K. Bach
Effect Of Inlet Duct Design On Fan Performance Of Indoor Air Handling Units With Pull-Through Fan Configuration (Ashrae Rp-1743), Khaled I. Alghamdi, Christian K. Bach
International High Performance Buildings Conference
During testing indoor air handling units, ASHRAE Standard 37 requires installing an inlet duct that might increase the length of the testing setup to exceed the capability of some testing facilities. ASHRAE Research Project 1743 (ASHRAE RP1743) addresses this issue by evaluating the effect of inlet duct design on fan performance of indoor air handling units. The findings of the study will allow identifying alternative, shorter, inlet duct configurations maintaining the fan performance as of that obtained with ASHRAE Standard 37 inlet duct. The test matrix of the project includes various indoor units differing in motor type, such as Constant …
Simulation Of Efficiency Of Different Configurations Of Residential Hybrid Heating Systems Combining Boiler And Heat Pump, Erica Roccatello, Alessandro Prada, Paolo Baggio, Cristian Zambrelli, Marco Baratieri
Simulation Of Efficiency Of Different Configurations Of Residential Hybrid Heating Systems Combining Boiler And Heat Pump, Erica Roccatello, Alessandro Prada, Paolo Baggio, Cristian Zambrelli, Marco Baratieri
International High Performance Buildings Conference
The contribution of residential buildings primary energy consumption in the U.S. accounts for more than 20% of the total. In this context, improving the efficiency of heating systems represents a key point for keeping up with the carbon reduction goals. Air-to-water heat pumps are a promising technology that has been deeply studied in recent years. Their main advantage is to improve the share of renewables. Nevertheless, they have some drawbacks, such as the poor efficiency at low ambient temperatures and at high supply water temperatures, necessary e.g. for domestic hot water production and in high temperature heating systems. The latter …
The Case For Dc: Motivation Of Modern Topologies, Dc-Powered Solutions, And Applications Within Residential Environments, Jonathan Ore, Fatih Meral, Davide Ziviani, Eckhard Groll
The Case For Dc: Motivation Of Modern Topologies, Dc-Powered Solutions, And Applications Within Residential Environments, Jonathan Ore, Fatih Meral, Davide Ziviani, Eckhard Groll
International High Performance Buildings Conference
The more than a century-old debate between AC and DC has its roots in an electrical distribution challenge, tackled by rival inventors Nikola Tesla and Thomas Edison during the late 1800s. Although originally collaborating on the improvements of Edison’s work, the pair eventually parted ways due to conflicts in their personalities and business pursuits. Edison’s direct current (DC) system leveraged a constant voltage and current to supply electricity, which was initially sufficient for small locales and geographical regions. However, DC encountered a major obstacle when longer-range transmission was required; there was simply no way to easily convert it between higher …
Compressor Performance Comparison Of R454a And R454c For Refrigeration, Lars Sjoholm, Youngchan Ma, Gurudath Nayak, Matt Stinson
Compressor Performance Comparison Of R454a And R454c For Refrigeration, Lars Sjoholm, Youngchan Ma, Gurudath Nayak, Matt Stinson
International Compressor Engineering Conference
The intent of this paper is to compare compressor performance of two low GWP refrigerants that are mildly flammable. Since there are limited test capabilities for compressors with flammable refrigerants, the compressor tests in this paper are based on a non-flammable refrigerant, in this case R513A. The tested compressor is an open type screw compressor that is driven by an external motor and is vapor injected. A physical compressor model is created from test data. This compressor model is not based on maps for efficiencies, capacity, or power consumption, but rather a basis of physical bulk elements, such as pressure …
Investigation Of Air-Side Fouling Of Split System Outdoor Heat Exchangers: Characterization, Performance Effects, And Frost Formation Interactions, David Yuill, Yifeng Hu
Investigation Of Air-Side Fouling Of Split System Outdoor Heat Exchangers: Characterization, Performance Effects, And Frost Formation Interactions, David Yuill, Yifeng Hu
International Refrigeration and Air Conditioning Conference
Fouling is generally believed to have a negative impact on heat exchanger performance, and has been studied extensively. Split systems, such as those that serve typical residential air-conditioners, have an air-to-refrigerant coil located outdoors, where it is subject to many airborne fouling agents, such as grass clippings, leaves, and dust. This research project took novel approach to testing the effects of air-side fouling. Instead of applying standardized fouling agents in a laboratory test, we collected fouled outdoor coils from field-deployed air-conditioners, and tested them in a laboratory. This allowed tight control and measurement, but with real fouling. The effects on …
Steady-State Parametric Study Of Semi-Open Absorption Heat Pump Water Heater Performance, Navin Kumar, Kyle R Gluesenkamp, Zhiyao Yang, Ahmad Abu-Heiba, Viral Patel, Rohit Bhagwat, Sidharth Sanadhya, Richard Rode, Michael Schmid, Saeed Moghaddam
Steady-State Parametric Study Of Semi-Open Absorption Heat Pump Water Heater Performance, Navin Kumar, Kyle R Gluesenkamp, Zhiyao Yang, Ahmad Abu-Heiba, Viral Patel, Rohit Bhagwat, Sidharth Sanadhya, Richard Rode, Michael Schmid, Saeed Moghaddam
International Refrigeration and Air Conditioning Conference
Water heating and dehumidification are major energy consumers in buildings. The novel semi-open absorption heat pump design utilizes the heat of absorption from the dehumidification of space for water heating. The architecture of the system consists of (1) a plate and frame membrane-based absorber, (2) a membrane-based desorber and condenser unit, (3) heat exchangers, (4) ionic liquid, and (5) a 189.3 L (50-gal) water tank. The membrane-based absorber enables heat and mass transfer between three streams: moist air, ionic liquid, and the heat transfer fluid. The heat of vapor absorption elevates the ionic liquid temperature and, in turn, heats the …
High-Temperature Organic Rankine Cycle Utilizing Novel Scroll Expander And Pump, Junyan Ren, Nishad G. Damle, Stephen Caskey, Bryce R. Shaffer, Davide Ziviani, Eckhard A. Groll
High-Temperature Organic Rankine Cycle Utilizing Novel Scroll Expander And Pump, Junyan Ren, Nishad G. Damle, Stephen Caskey, Bryce R. Shaffer, Davide Ziviani, Eckhard A. Groll
International Refrigeration and Air Conditioning Conference
Organic Rankine Cycles (ORC) are widely employed to extracting work from different heat sources to improve the operational efficiency of thermal systems. High-temperature ORCs (> 250 – 300 °C) are still particularly challenging especially when hydrocarbons cannot be used as the working fluids. Generators for Small Electric and Thermal Systems (GENSETs) are one example of systems where ORCs can be used as a bottoming cycle. A 1 kWe ORC has been previously constructed to evaluate the feasibility of designing an ORC with a heat source inlet temperature of approximately 500 °C. The test stand utilizes microtube evaporator, an air-cooled microchannel …
Absorption Cooling For Data Centers Powered By Solid Oxide Fuel Cell Waste Heat, Alejandro Lavernia, Maryam Asghari, Mastropasqua Luca, Jacob Brower
Absorption Cooling For Data Centers Powered By Solid Oxide Fuel Cell Waste Heat, Alejandro Lavernia, Maryam Asghari, Mastropasqua Luca, Jacob Brower
International Refrigeration and Air Conditioning Conference
Thermal integration of a solid oxide fuel cell and a lithium bromide absorption chiller is proposed for air conditioning at data centers. Solid oxide fuel cells (SOFC) can be effectively implemented as primary energy producers at data centers due to their efficiency, environmental friendliness, and fuel flexibility. This study focuses on row-level SOFC power in the range of 150 – 200 kW. Operating at temperatures greater than 700°C, SOFC systems can produce high quality heat that can be utilized by absorption technology to provide supplemental cooling for the servers. This study investigates the operation of a triple-effect absorption chiller (AC) …
Reinforcement Learning Control For Vapor Compression Refrigeration Cycle, Tech Logg Ding, Alison Subiantoro, Stuart Norris
Reinforcement Learning Control For Vapor Compression Refrigeration Cycle, Tech Logg Ding, Alison Subiantoro, Stuart Norris
International Refrigeration and Air Conditioning Conference
Vapor compression refrigeration cycles (VCRC) control optimization is an effective method to increase its' reliability and energy efficiency. In modern VCRC systems, the introduction of inverter compressors, electronic expansion valves, fan speed, and pump speed control has significantly increased their controllability. These improvements led to the development of many multivariable and predictive control strategies that improved the system's temperature tracking performance and increased the coefficient of performance (COP) by up to 30% compared to conventional on/off and PID controls. However, a VCRC also has high nonlinearities and parameter couplings, making it difficult to apply these modern control laws. This problem …
Experimental Quantification Of Liquid Line Temperature Drop As A Feature To Detect Liquid Line Restriction Faults In A Residential Heat Pump, Yifeng Hu, David P. Yuill, Yuxuan Chen
Experimental Quantification Of Liquid Line Temperature Drop As A Feature To Detect Liquid Line Restriction Faults In A Residential Heat Pump, Yifeng Hu, David P. Yuill, Yuxuan Chen
International Refrigeration and Air Conditioning Conference
Liquid line restrictions (LL) in a vapor compression refrigeration cycle cause abnormal pressure drops in the liquid line and reduce the refrigerant mass flow. Although a thermostatic expansion valve (TXV) in the system can compensate for small restrictions, larger restrictions cause the TXV to fully open, at which point the LL can create significant impacts on system performance. Furthermore, in the presence of other faults, like undercharge (UC) or non-condensable gas (NC) in the refrigerant, this impact becomes more pronounced. Therefore, effectively detecting this fault and addressing it can improve the efficiency of system and reduce the cost of operation …
Impacts And Detection Of Non-Condensable Gas In A Residential Air Source Heat Pump, Yifeng Hu, David P. Yuill, Yuxuan Chen
Impacts And Detection Of Non-Condensable Gas In A Residential Air Source Heat Pump, Yifeng Hu, David P. Yuill, Yuxuan Chen
International Refrigeration and Air Conditioning Conference
Non-condensable gas (NC) introduced into a vapor compression air-conditioner or heat pump system by improper system evacuation during an installation or repair has negative impacts on the performance of the system. The NC’s partial pressure combines with the refrigerant pressure, increasing the condenser’s total pressure, hence increasing the compressor specific work, leading to reduced efficiency for the system. Although the impacts of NC can be significant and the fault is believed to be common, little research has been conducted on this fault, compared with other faults. This paper describes a study of NC faults that includes two experimental investigations. The …
Performance Analysis Of Ejector Cycles For Separate Sensible And Latent Cooling In Air Conditioning, Jim Carow, Daniel Bacellar, Cara Martin
Performance Analysis Of Ejector Cycles For Separate Sensible And Latent Cooling In Air Conditioning, Jim Carow, Daniel Bacellar, Cara Martin
International Refrigeration and Air Conditioning Conference
While the overall system efficiency of split air conditioning (AC) systems has improved over the last three decades, residential air handling units (AHUs) used in those systems have essentially stayed the same in size, shape, form, and efficiency. Incremental improvements have been made to AHUs to address safety, functionality, and energy-efficiency concerns, however, their overall structure has remained the same. A promising technology that addresses fundamental challenges with conventional cycle efficiencies are ejector-based cycles, more commonly employed in refrigeration applications, but with great potential in AC systems as well. An ejector employed as an expansion device can recover expansion losses, …
Thermodynamic Comparison Of Transcritical Carbon Dioxide Booster Architectures To An R-513a Booster System In Commercial Refrigeration, David Snyder, Andrew Pansulla, Charles Allgood
Thermodynamic Comparison Of Transcritical Carbon Dioxide Booster Architectures To An R-513a Booster System In Commercial Refrigeration, David Snyder, Andrew Pansulla, Charles Allgood
International Refrigeration and Air Conditioning Conference
As global regulatory framework has been introduced to phase down the manufacture and use of hydrofluorocarbon (HFC) refrigerants on a total carbon emissions basis, many end users have been tasked with finding alternatives to current refrigeration architectures and associated working fluids. Using commercial refrigeration as an example, transcritical R-744 (CO2) booster architectures have been studied, piloted, and compared to conventional R-404A centralized systems. Many studies show favorable energy consumption and COP (coefficient of performance) in colder climates for CO2 versus R-404A. Concurrent with the advances in CO2 technology is the development of the lower GWP (global warming potential) HFC alternative …
Parenting Amidst Covid-19: Pandemic-Related Stressors, Inequities, And Treatment Utilization And Perceptions, Rachel Wamser-Nanney, Viann Nguyen-Feng, Annett Lotzin, Xiang Zhou
Parenting Amidst Covid-19: Pandemic-Related Stressors, Inequities, And Treatment Utilization And Perceptions, Rachel Wamser-Nanney, Viann Nguyen-Feng, Annett Lotzin, Xiang Zhou
Department of Educational Studies Faculty Publications
Many parents of children under age 18 are faced with additional COVID-19 parenting- related stressors and may be experiencing increases in psychological difficulties; however, we have yet to investigate parent’s levels of posttraumatic stress symptoms (PTSS) and adjustment disorder. Further, COVID-19 has served as a sobering reminder of the significant public health disparities in our society and it is critical to identify risk factors for poorer clinical outcomes. The primary objectives of the present study were to: (a) determine whether parents are reporting higher levels of pandemic-related stress, PTSS, and adjustment disorder than controls, (b) identify specific individual-level factors (e.g., …
Study On Pmf Rotary Compressor For Unitary Air Conditioners In N.A. Market, Bin Gao, Qiang Gao, Huaming Li, Jiangqiang Huang
Study On Pmf Rotary Compressor For Unitary Air Conditioners In N.A. Market, Bin Gao, Qiang Gao, Huaming Li, Jiangqiang Huang
International Compressor Engineering Conference
Unitary air conditioner in N.A. market takes the non-bleed TXV as its throttle valve. When the system turns off, the TXV automatically shut down to maintain the pressure in heat exchangers. This is benefit for SEER and comfort in use. However, pressure maintaining resulted in a fast-restart issue to fix-speed rotary compressor applying in this kind of system. To solve this problem, this paper firstly gave two concepts and principles of passive pressure balance and active pressure balance to conclude the means to achieve pressure balance in rotary compressor. Then, designed the technical scheme of PMF (Pressure Maintaining and Fast-restart) …