Eckhard Groll | Purdue University (original) (raw)
Papers by Eckhard Groll
A hybrid desiccant dehumidification air conditioning system is proposed. The main features of thi... more A hybrid desiccant dehumidification air conditioning system is proposed. The main features of this proposed system include: (1) there are two options of dehumidification, desiccant dehumidification and dehumidification via vapor compression cooling; (2) for the subsystem providing the desiccant dehumidification process, the air regeneration process occurs inside a closed loop, and a CO2 heat pump is utilized inside this loop for air regeneration, which has the potential to significantly reduce energy consumption compared to a traditional regeneration process; (3) based on the distribution of sensible load and latent load, there are six operating modes. For the application of a typical storage tank for a liquefied natural gas (LNG) carrier during its construction, the operating performance of the entire system is simulated and analyzed under two typical operating conditions. Compared to the traditional vapor compression air conditioning system, the hybrid system can save approximately 50% to 90% of the energy consumption.
IOP Conference Series: Materials Science and Engineering, Nov 1, 2022
View the article online for updates and enhancements. You may also like An experimental technique... more View the article online for updates and enhancements. You may also like An experimental technique to simulate and measure leakages in twin-screw compressor Hitesh H Patel and Vikas J Lakhera-Use of CFD to Investigate Flow Characteristics and Oil Distribution Inside an Oil-injected Screw Compressor
IOP Conference Series: Materials Science and Engineering
Twin-screw compressor technology is widely employed in commercial and industrial HVAC&R applicati... more Twin-screw compressor technology is widely employed in commercial and industrial HVAC&R applications as well as in air-compression and gas processing industries. Twin-screw compressors are characterized by relatively high efficiencies at part- and full-loads, and high reliability. However, innovative designs and higher efficiency are needed to further reduce power consumption, improve the compression process, and minimize internal losses. This study focuses on developing a simulation model of a twin-screw compressor with internal cooling channels to achieve a near isothermal compression process. A complex coupling between compression process and heat transfer occurs during the operation of the compressor. To analyze the compressor and the interaction between solid (i.e., rotors) and fluid phases (i.e., air and coolant), a CFD model with conjugate heat transfer has been developed and validated. The CFD model is used to predict compressor performance parameters such as isentropic effi...
This document has been made available through Purdue e-Pubs, a service of the Purdue University L... more This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional information. Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at
Engineering programs must prepare students for a global engineering profession. In global markets... more Engineering programs must prepare students for a global engineering profession. In global markets, processes as well as products can be outsourced. Highly technical engineering work may be completed by large and diverse collaborations. Engineering students need to have foundational work in languages, cultural differences, and strategies for working with diverse colleagues. Historically only about 3 % to 4 % of engineering students pursue study abroad opportunities. Clearly, new and innovative programs must be devised to build “global competency ” in undergraduate engineers. In working toward that end, the authors suggest that interdisciplinary collaborations between departments of foreign
Naval vessels typically require several ship service diesel generators (SSDGs) for electricity ge... more Naval vessels typically require several ship service diesel generators (SSDGs) for electricity generation with an average thermal efficiency of approximately 40-45%. Waste heat SSDGs represents a significant opportunity to drive bottoming Organic Rankine Cycles (ORCs) to increase their fuel efficiency. Waste heat streams include both high-temperature exhaust gases and low-temperature cooling loops. In this work, a comprehensive numerical analysis is carried out to compare different cycle architectures to maximize the ORC power output at both full- and part-load SSDG conditions. Both subcritical and transcritical cycle architectures with evaporators in series and in parallel have been investigated. Novel, high-speed, spinning scroll expanders have been considered as expansion devices. Parametric studies were conducted to assess the trade-off between ORC output and effectiveness of operation to determine an optimum payback period.
Varying the orientation of a vapor compression cycle and describing observed effects is a researc... more Varying the orientation of a vapor compression cycle and describing observed effects is a research field that has received very little attention. This paper presents the design of a test stand that is dedicated to the investigation of body-force effects on a vapor compression cycle and is able to rotate 360° around one axis. Results could be useful for transport and microgravity applications and contribute to the understanding of two-phase flow in general. It is shown that at certain operating conditions, inclining the system can lead to a sudden decrease of subcooling.
Transportation refrigeration requires efficient, compact, and reliable technology, and these cons... more Transportation refrigeration requires efficient, compact, and reliable technology, and these constraints must be met with especially rugged designs when used in a military application. Additionally, industry trends towards efficiency and environmental concerns have motivated the development of low global warming potential (GWP) refrigerants and efficient technologies to utilize them. This research focuses on the theoretical analysis and physical design of a transcritical carbon dioxide (CO2) cycle for application in a U.S. Army Multi-Temperature Refrigerated Container System (MTRCS). The MTRCS has two separate refrigeration compartments of variable size and operating temperature. The proposed transcritical CO2 cycle utilizes a novel compressor-expander unit called the Energy Recovery Compressor (ERC), which is an axial multi-piston compressor-expander that uses the Sanderson Rocker Arm Mechanism (S-RAM) to convert the shaft rotation into linear piston movements. Integrating the ERC ...
8th International Conference on Compressors and their Systems, 2013
The past phase-out of CFC and HCFC refrigerants and the upcoming phase-out of HFC refrigerants, c... more The past phase-out of CFC and HCFC refrigerants and the upcoming phase-out of HFC refrigerants, combined with advances in compressor technology, such as reduced noise and vibration and mechanical capacity control, has motivated the development of novel compression concepts for use in vapor compression cycles. This paper provides an overview of several new developments for refrigeration, air-conditioning and heat pumping applications, including three novel compressors called bowtie compressor, rotary spool compressor, and z-compressor. The bowtie compressor offers an integrated method of capacity modulation for use in domestic refrigerators/freezers. It modulates the cooling capacity by changing the piston stroke without changes of the clearance volume for better thermodynamic efficiency. The bowtie compressor received its name due to its two sector-shaped, opposing compression chambers forming a bowtie. The novel rotary spool compressor combines various aspects of rotary and reciprocating devices. Studies to date have shown that the rotary spool compressor can achieve high efficiencies at low manufacturing costs. The z-compressor is a dual-chamber hermetic rotary compressor with opposing upper and lower compression chambers separated by z-shaped blade. The compressor offers significantly lower noise and vibration levels than a conventional rolling piston compressor. In addition to presenting these new compressor types, recent research on linear compressors and diaphragm compressors will also be presented.
The possible flow patterns of CO2 flow boiling in horizontal tubes were studied based on analyses... more The possible flow patterns of CO2 flow boiling in horizontal tubes were studied based on analyses found in the literature. Annular flow is found to be the predominant flow pattern for normal operating conditions. The mechanisms required to sustain annular flow were examined; the occurrence of dryout is an important phenomenon in annular CO2 flow. A model to predict the onset of dryout and the location of complete dryout for CO2 flow boiling in horizontal tubes is described and evaluated. (See also this Bulletin, references 2003-2191 and 2003-2192.)
Research efforts addressing large U.S. consumers can generate impactful reductions on the global ... more Research efforts addressing large U.S. consumers can generate impactful reductions on the global energy picture. 41% of U.S. energy consumption is from buildings, 22% residential versus 19% commercial. Household appliances combine to 27%, the second largest residential site energy usage. With many appliances converting electricity to heat and generating waste heat, the authors propose energy reduction through thermal integration of all major appliances. The novel approach will require adding equipment and modifications to existing appliances for thermal sharing. A Modelica model is built for each appliance and simulated to quantify energy savings. The dishwasher is the first appliance investigated by installing a heat exchanger to heat the process water via an external hot water loop instead of the electric calrod heater. The traditional function is first captured in the model and the predicted water sump temperature is compared to available experimental data from the manufacturer. ...
The 16th International Refrigeration and Air-Conditioning Conference is one of 3 Purdue Conferenc... more The 16th International Refrigeration and Air-Conditioning Conference is one of 3 Purdue Conferences presented on the same CD-ROM, held at Purdue, West Lafayette (Indiana), USA. 275 papers were presented on topics ranging from fundamental to applied, including heat transfer and fluid flow fundamentals, alternative refrigerants and working fluids, modeling of components and systems, heat exchanger enhancements and characterizations, controls, diagnostics, domestic, commercial and industrial refrigeration, heat pumps, transport refrigeration and air conditioning. The two other Purdue Conferences presented on the CD-ROM are: the 23rd International Compressor Engineering Conference (123 papers), and the 4th International High Performance Buildings Conference (80 papers).
For simulating the performance of unitary air conditioning and heat pumping equipment at design c... more For simulating the performance of unitary air conditioning and heat pumping equipment at design conditions, the amount of subcooling leaving the condenser is typically specified at design conditions and the required refrigerant charge necessary to achieve that subcooling is computed. For off-design conditions, the charge is fixed at the value determined for the design condition and the amount of subcooling is estimated. Previous studies have shown that existing models do not predict the effect of off-design charge very well, even when tuned at a design condition. The paper presents a method for tuning parameters associated with a charge correction equation that requires data for two operating points. The ability of a system model to predict off-design charge effects is significantly improved through the use of this tuning approach. This was confirmed through comparisons with measured results and predictions obtained from existing tuning approaches.
In approximately 150 years, the refrigeration industry, meaning the broad context of heating, coo... more In approximately 150 years, the refrigeration industry, meaning the broad context of heating, cooling and refrigeration applications, profoundly impacted human daily activities. From ice harvesting during the 19th century, to initial research on artificial refrigeration conducted by W. Cullen, to well-known scientists, chemists and engineers B. Franklin, J. Hadley, J. Perkins, F. Carre, and C. von Linde, among others, refrigeration technologies experienced transformational improvements, whose fundamental principles are still in use today. The “Miracle Substances” initially introduced by Thomas Midgley et al. in the 1930s, which were then further developed to mitigate environmental concerns, enabled modern refrigeration and heat pumping systems, as well as organic Rankine cycles for power generation from renewable and waste heat sources. Despite the tremendous positive impacts on lifestyle, nutrition, personal comfort, healthcare, industrial and transportation activities in general, ...
CO2 is being advocated as one of the natural refrigerants to replace CFCs and HCFCs in vapour com... more CO2 is being advocated as one of the natural refrigerants to replace CFCs and HCFCs in vapour compression cycles based on its environmentally friendly characteristics. However, the perceived lower efficiency of the basic transcritical CO2 refrigeration cycle compared to vapour compression systems using HFC and HCFC refrigerants is a major hindrance for the technology to make progress towards practical applications. In order to recover the expansion losses and increase the cycle efficiency, it has been proposed to replace the expansion valve with either a work producing expansion device or an ejector expansion device. A comparison of the two devices shows that the ejector expansion device offers the advantages of simplicity, reliability, and availability while work producing expansion devices have the potential to yield higher cycle efficiencies. In the paper, it is shown that the transcritical CO2 cycle with an ejector expansion device outperforms a basic transcritical CO2 cycle in ...
IOP Conference Series: Materials Science and Engineering, 2021
A new experimental test facility was designed to test vapor compression chillers of up to 145.9 r... more A new experimental test facility was designed to test vapor compression chillers of up to 145.9 refrigeration tons (approximately 513 kW). To implement such a large-capacity test facility in a university laboratory research environment, the system design is based on regenerative shell and tube heat exchangers. The capacity load on the chiller can be controlled via a bypass valve that allows a flow change over the internal heat exchangers. In addition to the internal sensors of the chiller, a variety of sensors in the system ensures a detailed recording of data as well as an automation of the test procedure. The test facility is constructed and commissioned to execute the performance according the AHRI Standard 550/590. The chiller has been tested in full load and part load rating conditions to achieve a characteristic performance line of the machine. Recorded data is averaged and evaluated according to the requirements of the AHRI standard. The results of the baseline testing and th...
IOP Conference Series: Materials Science and Engineering, 2019
A new system solution has been developed and tested by the authors and has been shown to improve ... more A new system solution has been developed and tested by the authors and has been shown to improve the Seasonal Energy Efficiency Rating (SEER) of fixed-speed condenser split-system residential heat pumps. This is achieved through the use of a low power electronic drive that allows components with PSC motors (such as fans and compressors) to operate at multiple low speeds or variable speeds when partial capacity is required. At full capacity, the electronic drive is disabled and the PSC motors are operated at fixed speeds dictated by the frequency of the power source. Previous research by the authors has shown that fixed-speed heat pumps driven by rotary compressors with PSC motors achieve significantly greater improvements in performance and in overall SEER when operated with the electronic drive than similar heat pumps driven by scroll compressors with PSC motors. The current research measures the compressor and drive performance through calorimeter testing. This paper presents the ...
IOP Conference Series: Materials Science and Engineering, 2019
All positive displacement compressors (PDC’s) experience pressure fluctuation at the discharge po... more All positive displacement compressors (PDC’s) experience pressure fluctuation at the discharge ports of the compression mechanism, and these fluctuations can adversely affect compressor performance. These pressure fluctuations are caused by the nature of PDC’s; when a pocket of working fluid is exposed to system piping at differing pressure levels, a wave of pressure equalization flows through the line, potentially causing the compressor and piping to vibrate and generate noise (Soedel 2007). Compressor manufacturers currently use serial muffler designs, discharge plenums, and valves to minimize this fluctuation, but pressure fluctuation may persist at the outlet of serial muffling methods. A parallel muffling design has been developed for use in Roots blowers, having significantly reduced noise and pressure fluctuation seen in these machines (Huang et al. 2014). To identify the potential for use of this parallel muffling design in refrigeration systems and PDC’s, the magnitude of f...
IOP Conference Series: Materials Science and Engineering, 2017
A comprehensive simulation model is presented to predict the performance of a hermetic reciprocat... more A comprehensive simulation model is presented to predict the performance of a hermetic reciprocating compressor and to reveal the underlying mechanisms when the compressor is running. The presented model is composed of sub-models simulating the in-cylinder compression process, piston ring/journal bearing frictional power loss, single phase induction motor and the overall compressor energy balance among different compressor components. The valve model, leakage through piston ring model and in-cylinder heat transfer model are also incorporated into the in-cylinder compression process model. A numerical algorithm solving the model is introduced. The predicted results of the compressor mass flow rate and input power consumption are compared to the published compressor map values. Future work will focus on detailed experimental validation of the model and parametric studies investigating the effects of structural parameters, including the stroke-to-bore ratio, on the compressor performance.
A hybrid desiccant dehumidification air conditioning system is proposed. The main features of thi... more A hybrid desiccant dehumidification air conditioning system is proposed. The main features of this proposed system include: (1) there are two options of dehumidification, desiccant dehumidification and dehumidification via vapor compression cooling; (2) for the subsystem providing the desiccant dehumidification process, the air regeneration process occurs inside a closed loop, and a CO2 heat pump is utilized inside this loop for air regeneration, which has the potential to significantly reduce energy consumption compared to a traditional regeneration process; (3) based on the distribution of sensible load and latent load, there are six operating modes. For the application of a typical storage tank for a liquefied natural gas (LNG) carrier during its construction, the operating performance of the entire system is simulated and analyzed under two typical operating conditions. Compared to the traditional vapor compression air conditioning system, the hybrid system can save approximately 50% to 90% of the energy consumption.
IOP Conference Series: Materials Science and Engineering, Nov 1, 2022
View the article online for updates and enhancements. You may also like An experimental technique... more View the article online for updates and enhancements. You may also like An experimental technique to simulate and measure leakages in twin-screw compressor Hitesh H Patel and Vikas J Lakhera-Use of CFD to Investigate Flow Characteristics and Oil Distribution Inside an Oil-injected Screw Compressor
IOP Conference Series: Materials Science and Engineering
Twin-screw compressor technology is widely employed in commercial and industrial HVAC&R applicati... more Twin-screw compressor technology is widely employed in commercial and industrial HVAC&R applications as well as in air-compression and gas processing industries. Twin-screw compressors are characterized by relatively high efficiencies at part- and full-loads, and high reliability. However, innovative designs and higher efficiency are needed to further reduce power consumption, improve the compression process, and minimize internal losses. This study focuses on developing a simulation model of a twin-screw compressor with internal cooling channels to achieve a near isothermal compression process. A complex coupling between compression process and heat transfer occurs during the operation of the compressor. To analyze the compressor and the interaction between solid (i.e., rotors) and fluid phases (i.e., air and coolant), a CFD model with conjugate heat transfer has been developed and validated. The CFD model is used to predict compressor performance parameters such as isentropic effi...
This document has been made available through Purdue e-Pubs, a service of the Purdue University L... more This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional information. Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at
Engineering programs must prepare students for a global engineering profession. In global markets... more Engineering programs must prepare students for a global engineering profession. In global markets, processes as well as products can be outsourced. Highly technical engineering work may be completed by large and diverse collaborations. Engineering students need to have foundational work in languages, cultural differences, and strategies for working with diverse colleagues. Historically only about 3 % to 4 % of engineering students pursue study abroad opportunities. Clearly, new and innovative programs must be devised to build “global competency ” in undergraduate engineers. In working toward that end, the authors suggest that interdisciplinary collaborations between departments of foreign
Naval vessels typically require several ship service diesel generators (SSDGs) for electricity ge... more Naval vessels typically require several ship service diesel generators (SSDGs) for electricity generation with an average thermal efficiency of approximately 40-45%. Waste heat SSDGs represents a significant opportunity to drive bottoming Organic Rankine Cycles (ORCs) to increase their fuel efficiency. Waste heat streams include both high-temperature exhaust gases and low-temperature cooling loops. In this work, a comprehensive numerical analysis is carried out to compare different cycle architectures to maximize the ORC power output at both full- and part-load SSDG conditions. Both subcritical and transcritical cycle architectures with evaporators in series and in parallel have been investigated. Novel, high-speed, spinning scroll expanders have been considered as expansion devices. Parametric studies were conducted to assess the trade-off between ORC output and effectiveness of operation to determine an optimum payback period.
Varying the orientation of a vapor compression cycle and describing observed effects is a researc... more Varying the orientation of a vapor compression cycle and describing observed effects is a research field that has received very little attention. This paper presents the design of a test stand that is dedicated to the investigation of body-force effects on a vapor compression cycle and is able to rotate 360° around one axis. Results could be useful for transport and microgravity applications and contribute to the understanding of two-phase flow in general. It is shown that at certain operating conditions, inclining the system can lead to a sudden decrease of subcooling.
Transportation refrigeration requires efficient, compact, and reliable technology, and these cons... more Transportation refrigeration requires efficient, compact, and reliable technology, and these constraints must be met with especially rugged designs when used in a military application. Additionally, industry trends towards efficiency and environmental concerns have motivated the development of low global warming potential (GWP) refrigerants and efficient technologies to utilize them. This research focuses on the theoretical analysis and physical design of a transcritical carbon dioxide (CO2) cycle for application in a U.S. Army Multi-Temperature Refrigerated Container System (MTRCS). The MTRCS has two separate refrigeration compartments of variable size and operating temperature. The proposed transcritical CO2 cycle utilizes a novel compressor-expander unit called the Energy Recovery Compressor (ERC), which is an axial multi-piston compressor-expander that uses the Sanderson Rocker Arm Mechanism (S-RAM) to convert the shaft rotation into linear piston movements. Integrating the ERC ...
8th International Conference on Compressors and their Systems, 2013
The past phase-out of CFC and HCFC refrigerants and the upcoming phase-out of HFC refrigerants, c... more The past phase-out of CFC and HCFC refrigerants and the upcoming phase-out of HFC refrigerants, combined with advances in compressor technology, such as reduced noise and vibration and mechanical capacity control, has motivated the development of novel compression concepts for use in vapor compression cycles. This paper provides an overview of several new developments for refrigeration, air-conditioning and heat pumping applications, including three novel compressors called bowtie compressor, rotary spool compressor, and z-compressor. The bowtie compressor offers an integrated method of capacity modulation for use in domestic refrigerators/freezers. It modulates the cooling capacity by changing the piston stroke without changes of the clearance volume for better thermodynamic efficiency. The bowtie compressor received its name due to its two sector-shaped, opposing compression chambers forming a bowtie. The novel rotary spool compressor combines various aspects of rotary and reciprocating devices. Studies to date have shown that the rotary spool compressor can achieve high efficiencies at low manufacturing costs. The z-compressor is a dual-chamber hermetic rotary compressor with opposing upper and lower compression chambers separated by z-shaped blade. The compressor offers significantly lower noise and vibration levels than a conventional rolling piston compressor. In addition to presenting these new compressor types, recent research on linear compressors and diaphragm compressors will also be presented.
The possible flow patterns of CO2 flow boiling in horizontal tubes were studied based on analyses... more The possible flow patterns of CO2 flow boiling in horizontal tubes were studied based on analyses found in the literature. Annular flow is found to be the predominant flow pattern for normal operating conditions. The mechanisms required to sustain annular flow were examined; the occurrence of dryout is an important phenomenon in annular CO2 flow. A model to predict the onset of dryout and the location of complete dryout for CO2 flow boiling in horizontal tubes is described and evaluated. (See also this Bulletin, references 2003-2191 and 2003-2192.)
Research efforts addressing large U.S. consumers can generate impactful reductions on the global ... more Research efforts addressing large U.S. consumers can generate impactful reductions on the global energy picture. 41% of U.S. energy consumption is from buildings, 22% residential versus 19% commercial. Household appliances combine to 27%, the second largest residential site energy usage. With many appliances converting electricity to heat and generating waste heat, the authors propose energy reduction through thermal integration of all major appliances. The novel approach will require adding equipment and modifications to existing appliances for thermal sharing. A Modelica model is built for each appliance and simulated to quantify energy savings. The dishwasher is the first appliance investigated by installing a heat exchanger to heat the process water via an external hot water loop instead of the electric calrod heater. The traditional function is first captured in the model and the predicted water sump temperature is compared to available experimental data from the manufacturer. ...
The 16th International Refrigeration and Air-Conditioning Conference is one of 3 Purdue Conferenc... more The 16th International Refrigeration and Air-Conditioning Conference is one of 3 Purdue Conferences presented on the same CD-ROM, held at Purdue, West Lafayette (Indiana), USA. 275 papers were presented on topics ranging from fundamental to applied, including heat transfer and fluid flow fundamentals, alternative refrigerants and working fluids, modeling of components and systems, heat exchanger enhancements and characterizations, controls, diagnostics, domestic, commercial and industrial refrigeration, heat pumps, transport refrigeration and air conditioning. The two other Purdue Conferences presented on the CD-ROM are: the 23rd International Compressor Engineering Conference (123 papers), and the 4th International High Performance Buildings Conference (80 papers).
For simulating the performance of unitary air conditioning and heat pumping equipment at design c... more For simulating the performance of unitary air conditioning and heat pumping equipment at design conditions, the amount of subcooling leaving the condenser is typically specified at design conditions and the required refrigerant charge necessary to achieve that subcooling is computed. For off-design conditions, the charge is fixed at the value determined for the design condition and the amount of subcooling is estimated. Previous studies have shown that existing models do not predict the effect of off-design charge very well, even when tuned at a design condition. The paper presents a method for tuning parameters associated with a charge correction equation that requires data for two operating points. The ability of a system model to predict off-design charge effects is significantly improved through the use of this tuning approach. This was confirmed through comparisons with measured results and predictions obtained from existing tuning approaches.
In approximately 150 years, the refrigeration industry, meaning the broad context of heating, coo... more In approximately 150 years, the refrigeration industry, meaning the broad context of heating, cooling and refrigeration applications, profoundly impacted human daily activities. From ice harvesting during the 19th century, to initial research on artificial refrigeration conducted by W. Cullen, to well-known scientists, chemists and engineers B. Franklin, J. Hadley, J. Perkins, F. Carre, and C. von Linde, among others, refrigeration technologies experienced transformational improvements, whose fundamental principles are still in use today. The “Miracle Substances” initially introduced by Thomas Midgley et al. in the 1930s, which were then further developed to mitigate environmental concerns, enabled modern refrigeration and heat pumping systems, as well as organic Rankine cycles for power generation from renewable and waste heat sources. Despite the tremendous positive impacts on lifestyle, nutrition, personal comfort, healthcare, industrial and transportation activities in general, ...
CO2 is being advocated as one of the natural refrigerants to replace CFCs and HCFCs in vapour com... more CO2 is being advocated as one of the natural refrigerants to replace CFCs and HCFCs in vapour compression cycles based on its environmentally friendly characteristics. However, the perceived lower efficiency of the basic transcritical CO2 refrigeration cycle compared to vapour compression systems using HFC and HCFC refrigerants is a major hindrance for the technology to make progress towards practical applications. In order to recover the expansion losses and increase the cycle efficiency, it has been proposed to replace the expansion valve with either a work producing expansion device or an ejector expansion device. A comparison of the two devices shows that the ejector expansion device offers the advantages of simplicity, reliability, and availability while work producing expansion devices have the potential to yield higher cycle efficiencies. In the paper, it is shown that the transcritical CO2 cycle with an ejector expansion device outperforms a basic transcritical CO2 cycle in ...
IOP Conference Series: Materials Science and Engineering, 2021
A new experimental test facility was designed to test vapor compression chillers of up to 145.9 r... more A new experimental test facility was designed to test vapor compression chillers of up to 145.9 refrigeration tons (approximately 513 kW). To implement such a large-capacity test facility in a university laboratory research environment, the system design is based on regenerative shell and tube heat exchangers. The capacity load on the chiller can be controlled via a bypass valve that allows a flow change over the internal heat exchangers. In addition to the internal sensors of the chiller, a variety of sensors in the system ensures a detailed recording of data as well as an automation of the test procedure. The test facility is constructed and commissioned to execute the performance according the AHRI Standard 550/590. The chiller has been tested in full load and part load rating conditions to achieve a characteristic performance line of the machine. Recorded data is averaged and evaluated according to the requirements of the AHRI standard. The results of the baseline testing and th...
IOP Conference Series: Materials Science and Engineering, 2019
A new system solution has been developed and tested by the authors and has been shown to improve ... more A new system solution has been developed and tested by the authors and has been shown to improve the Seasonal Energy Efficiency Rating (SEER) of fixed-speed condenser split-system residential heat pumps. This is achieved through the use of a low power electronic drive that allows components with PSC motors (such as fans and compressors) to operate at multiple low speeds or variable speeds when partial capacity is required. At full capacity, the electronic drive is disabled and the PSC motors are operated at fixed speeds dictated by the frequency of the power source. Previous research by the authors has shown that fixed-speed heat pumps driven by rotary compressors with PSC motors achieve significantly greater improvements in performance and in overall SEER when operated with the electronic drive than similar heat pumps driven by scroll compressors with PSC motors. The current research measures the compressor and drive performance through calorimeter testing. This paper presents the ...
IOP Conference Series: Materials Science and Engineering, 2019
All positive displacement compressors (PDC’s) experience pressure fluctuation at the discharge po... more All positive displacement compressors (PDC’s) experience pressure fluctuation at the discharge ports of the compression mechanism, and these fluctuations can adversely affect compressor performance. These pressure fluctuations are caused by the nature of PDC’s; when a pocket of working fluid is exposed to system piping at differing pressure levels, a wave of pressure equalization flows through the line, potentially causing the compressor and piping to vibrate and generate noise (Soedel 2007). Compressor manufacturers currently use serial muffler designs, discharge plenums, and valves to minimize this fluctuation, but pressure fluctuation may persist at the outlet of serial muffling methods. A parallel muffling design has been developed for use in Roots blowers, having significantly reduced noise and pressure fluctuation seen in these machines (Huang et al. 2014). To identify the potential for use of this parallel muffling design in refrigeration systems and PDC’s, the magnitude of f...
IOP Conference Series: Materials Science and Engineering, 2017
A comprehensive simulation model is presented to predict the performance of a hermetic reciprocat... more A comprehensive simulation model is presented to predict the performance of a hermetic reciprocating compressor and to reveal the underlying mechanisms when the compressor is running. The presented model is composed of sub-models simulating the in-cylinder compression process, piston ring/journal bearing frictional power loss, single phase induction motor and the overall compressor energy balance among different compressor components. The valve model, leakage through piston ring model and in-cylinder heat transfer model are also incorporated into the in-cylinder compression process model. A numerical algorithm solving the model is introduced. The predicted results of the compressor mass flow rate and input power consumption are compared to the published compressor map values. Future work will focus on detailed experimental validation of the model and parametric studies investigating the effects of structural parameters, including the stroke-to-bore ratio, on the compressor performance.