Eckhard Groll
Purdue University, Mechanical Engineering, Faculty Member
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... 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.
Research Interests:
Research Interests:
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... 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...
Research Interests:
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... 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, processes as well as products can be outsourced. Highly technical engineering work may be completed by large and diverse collaborations.... 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 generation with an average thermal efficiency of approximately 40-45%. Waste heat SSDGs represents a significant opportunity to drive bottoming... 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.
Research Interests:
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... 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.
Research Interests:
Research Interests:
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... 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 ...
Research Interests:
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... 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.
Research Interests:
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... 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 Interests:
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%,... 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. ...
Research Interests:
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... 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).
Research Interests:
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... 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.
Research Interests:
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... 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, ...
Research Interests:
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... 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 ...
Research Interests:
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,... 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...
Research Interests:
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... 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 ...
Research Interests:
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... 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...
Research Interests:
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... 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.
Research Interests:
Research Interests:
Research Interests:
Afin d'ameliorer la performance d'un cycle de refrigeration au dioxide de carbone transcritique, un tube d'expansion a vorticite utilisant l'effect de Ranque-Hilsch et, eu guise d'alternative, une machine... more
Afin d'ameliorer la performance d'un cycle de refrigeration au dioxide de carbone transcritique, un tube d'expansion a vorticite utilisant l'effect de Ranque-Hilsch et, eu guise d'alternative, une machine d'expansion sout proposes. Les performances de les machines sout comparies avec celle de valres d'expansion conventionelles isentlalpiques. Le pour et le coutre de les deux options sout discutes. De plus, l'impact de les options sur la performance globale d'un cycle transuitique est e'tudie a l'aide de simulations nomeriques.
Research Interests:
Un modele d'evaporateur de CO 2 a microcanal est presente. La conception generale est basee sur des tendances qualitatives favorables du calcul des temperatures et des distributions de flux de chaleur dans l'evaporateur. Les... more
Un modele d'evaporateur de CO 2 a microcanal est presente. La conception generale est basee sur des tendances qualitatives favorables du calcul des temperatures et des distributions de flux de chaleur dans l'evaporateur. Les calculs de la capacite volumetrique de refroidissement ont aussi suivi les tendances physiques attendues. En effet, le coefficient de transfert de chaleur refrigerant-paroi (h f ) a un effet negligeable sur la capacite volumetrique et le coefficient de transfert de chaleur air-paroi (h a ), une resistance thermique de deux ordres de grandeur superieure, a une forte influence car l'augmentation de la capacite est presque directement liee a h a . La validation du modele avec des donnees experimentales a aussi ete testee bien qu'une comparaison directe n'ait pu etre faite car la valeur de h a pour les donnees n'etait pas connue. Ces valeurs de capacite representent les valeurs optimales pour la situation etudiee ; elles constituent une estimation des limites de performance pour cette geometrie particuliere d'evaporateur et pour les valeurs citees ces coefficients de transfert de chaleur air-paroi et refrigerant-paroi. Il est vraisemblable que dans un appareillage reel, la baisse pression due aux frottements et le dessechement diminuent la valeur des capacites.
Research Interests:
L'article decrit une etude experimentale servant a evaluer l'impact de petites quantites d'huile de refroidissement entrainees dans l'ecoulement sur le coefficient de transfert de chaleur et la chute de pression du dioxyde... more
L'article decrit une etude experimentale servant a evaluer l'impact de petites quantites d'huile de refroidissement entrainees dans l'ecoulement sur le coefficient de transfert de chaleur et la chute de pression du dioxyde de carbone supercritique au cours du refroidissement a l'interieur d'un tube. Pour ce faire, des essais ont ete conduits avec du dioxyde de carbone pur, et avec 2 % et 5 % d'huile de refroidissement. Les resultats ont montre que de petites quantites d'huile ajoutees a l'ecoulement du dioxyde de carbone avaient un effet important sur le coefficient de transfert de chaleur, et notamment qu'une concentration d'huile de 5 % reduisait le coefficient de transfert de chaleur de l'ordre de 25 %, alors qu'une concentration en huile de 2 % le reduisait en moyenne de 15 %. Cependant, le pic du coefficient de transfert de chaleur se produit encore a la temperature pseudocritique. La chute de pression augmente par l'ajout de petits pourcentages d'huile. Il a ete demontre que la chute de pression est plus importante pour une concentration d'huile de 2 % que pour une concentration de 5 %.
Research Interests:
... HORTON WT (1) ; GROLL EA (1) ; SHARP E. (1) ; GRODEM B. (Commentateur) ; HRNJAK P. (Commentateur) ; RIVET P. (Commentateur) ; HAUKAS ... Institut international du froid, Paris, FRANCE (1965) (Revue) Institut international du froid,... more
... HORTON WT (1) ; GROLL EA (1) ; SHARP E. (1) ; GRODEM B. (Commentateur) ; HRNJAK P. (Commentateur) ; RIVET P. (Commentateur) ; HAUKAS ... Institut international du froid, Paris, FRANCE (1965) (Revue) Institut international du froid, Paris, FRANCE (1998) (Monographie ...
Research Interests: Physics and Humanities
Compression refrigeration plants are used widely in refrigerated warehouses. Most commonly, they are driven by electric power. The electric power drives the compressor, pump and fan motors. Therefore, to reduce the electricity bill of... more
Compression refrigeration plants are used widely in refrigerated warehouses. Most commonly, they are driven by electric power. The electric power drives the compressor, pump and fan motors. Therefore, to reduce the electricity bill of refrigerated warehouses, one method is to improve the efficiency of the electric systems of the plants. Improving the power factor is an important method for improving the efficiency of electric systems. This is not a new discovery. However, based on a 1999 survey of refrigerated warehouses conducted by the authors in the United States and Canada, the issue of improving the power factor was often overlooked. The measures and potentials of energy cost savings by improving the power factor are discussed in this article. A case study based on the survey follows.
Research Interests:
The 24th International Compressor Engineering Conference is one of 3 Purdue Conferences presented on the same CD-ROM, held at Purdue, West Lafayette (Indiana), USA. 132 papers were presented on specific compressor technologies such as... more
The 24th International Compressor Engineering Conference is one of 3 Purdue Conferences presented on the same CD-ROM, held at Purdue, West Lafayette (Indiana), USA. 132 papers were presented on specific compressor technologies such as reciprocating, rotary, scroll, screw, centrifugal, linear and novel compressors. In addition, there have been sessions that covered issues and present modeling and evaluation tools related to compressor design and reliability, such as noise control, vibration, gas pulsations, materials, lubrication, wear, and valves. The two other Purdue Conferences presented on the CD-ROM are: the 17th International Refrigeration and Air-Conditioning Conference (251 papers), and the 5th International High Performance Buildings Conference (91 papers).
Research Interests:
A comprehensive model of a linear compressor for electronics cooling was previously presented by Bradshaw et al. (2011). The current study expands upon this work by first developing methods for predicting the resonant frequency of a... more
A comprehensive model of a linear compressor for electronics cooling was previously presented by Bradshaw et al. (2011). The current study expands upon this work by first developing methods for predicting the resonant frequency of a linear compressor and for controlling its piston stroke. Key parameters governing compressor performance – leakage gap, eccentricity, and piston geometry – are explored using a sensitivity analysis. It is demonstrated that for optimum performance, the leakage gap and frictional parameters should be minimized. In addition, the ratio of piston stroke to diameter should not exceed a value of one to minimize friction and leakage losses, but should be large enough to preclude the need for an oversized motor. An improved linear compressor design is proposed for an electronics cooling application, with a predicted cooling capacity of 200 W a cylindrical compressor package size of diameter 50.3 mm and length 102 mm.
Research Interests:
Research Interests:
Research Interests:
This paper explores the feasibility of using electrostatically actuated diaphragm compressors in a miniature-scale refrigeration system for electronics cooling. A previously developed experimentally validated analytical model for the... more
This paper explores the feasibility of using electrostatically actuated diaphragm compressors in a miniature-scale refrigeration system for electronics cooling. A previously developed experimentally validated analytical model for the diaphragm compressor is used in conjunction with an optimization approach to determine the required dimensions for the compressor. The analysis reveals that the pressure rise and volume flow rate required for the electronics cooling application are not achieved using a single compressor because of material property limitations. A three-dimensional array of compressors is proposed instead with which the cooling requirements and the size restrictions for electronics cooling applications may be simultaneously satisfied
Research Interests:
Detailed models are crucial tools for engineers in designing and optimizing systems. In particular, mechanistic modeling of vapor compression systems for accurate performance predictions at both fulland part-load conditions have been... more
Detailed models are crucial tools for engineers in designing and optimizing systems. In particular, mechanistic modeling of vapor compression systems for accurate performance predictions at both fulland part-load conditions have been improved significantly in the past decades. Yet, fully deterministic models present still challenges in estimating charge inventory in order to optimize the performance. In this work, a generalized framework for simulating vapor compression cycles (VCC) has been developed with emphasis on a charge-sensitive model. In order to illustrate the capabilities of the tool, a direct-expansion (DX) cycle has been considered. In the cycle model, the compressor was mapped by employing dimensionless π groups correlation proposed by Mendoza-Miranda et al. (2016), the evaporator and the condenser were constructed based on the ACHP models (Bell, 2015). Furthermore, a TXV model was implemented based on Li and Braun (2008) formulation. With respect to the charge invento...
Research Interests:
The coefficient of performance and heating capacity of conventional air-to-air heat pumps decrease towards lower ambient temperatures. Heat pump systems are increasingly installed in residential homes but whereas they are already... more
The coefficient of performance and heating capacity of conventional air-to-air heat pumps decrease towards lower ambient temperatures. Heat pump systems are increasingly installed in residential homes but whereas they are already widespread in moderate climates, applications in very cold climates are limited. Since the heating load increases at low ambient temperatures, additional auxiliary heating systems are needed, which results in poor seasonal coefficients of performance. Oil-flooded compression is a technology to improve the performance of heat pump systems. This concept seeks to approach an isothermal compression process by injecting oil characterized by a higher specific heat than the refrigerant to absorb heat during the compression process. In a previous study (Yang et al. 2014), a 5-ton (17.6 kW) R410A packaged heat pump retrofitted with an oil injected compressor and regenerator was tested, in which one circuit within the indoor heat exchanger was modified to serve as an...
Research Interests:
Organic Rankine Cycles (ORC) are thermodynamic power cycles designed to generate work from low temperature heat sources. The low temperature heat input is, typically, between 80 °C to 270 °C. The efficiency of an ORC is highly dependent... more
Organic Rankine Cycles (ORC) are thermodynamic power cycles designed to generate work from low temperature heat sources. The low temperature heat input is, typically, between 80 °C to 270 °C. The efficiency of an ORC is highly dependent on the expander characteristics. This article experimentally evaluates the performance of a scroll expander with nominal capacity of 5 kW, built-in volume ratio of 3.5. Tests were conducted in an ORC test-rig using R245fa as the working fluid. The expander was tested over a full performance map consisting of two temperature sources 85°C and 110°C and five expander speeds, from 800 RPM to 3000 RPM. The scroll expander achieved a maximum isentropic efficiency of 0.58, for a volume ratio of 6.12, at the expander speed of 1600 RPM and temperature source of 110°C. The same temperature source also registered the maximum expander power output, 3.75 kW, at volume ratio of 6.55 and an expander speed of 2500 RPM. A semi-empirical model was developed to predict...
Research Interests:
Electrochemical cells have been widely explored for their use in high efficiency energy systems. In this paper a novel heat pump cycle is proposed that utilizes chemical looping driven by electrochemical cells. Chemical looping is a... more
Electrochemical cells have been widely explored for their use in high efficiency energy systems. In this paper a novel heat pump cycle is proposed that utilizes chemical looping driven by electrochemical cells. Chemical looping is a method that has been applied to various applications such as combustion and air separation. It consists of cycling a substance between different chemical compositions in order to produce a desired effect. When the chemical composition of a fluid changes, various properties such as its saturation pressure will also change. In the proposed concept, the chemical looping of electrochemically active fluids is leveraged to generate a heat pumping effect. A number of electrochemically active liquid organic hydrogen carriers including alcohols such as ethanol and isopropanol have been theoretically investigated for use in the proposed cycle. These organic fluids were integrated into a thermodynamic model of the proposed cycle. When operating as an air conditione...
Research Interests:
An increasing interest in organic Rankine cycle (ORC) technology has led to numerous simulation and optimization studies. In the open-literature different modeling approaches can be found, but general software tools available to the... more
An increasing interest in organic Rankine cycle (ORC) technology has led to numerous simulation and optimization studies. In the open-literature different modeling approaches can be found, but general software tools available to the academic/industrial community are limited. A generalized ORC simulation tool, named ORCSim, is proposed in this paper. The framework is developed using object-oriented programming that easily allows improvements and future extensions. Currently two cycle configurations are implemented, i.e. a basic ORC and an ORC with liquid-flooded expansion. The software architecture, the thermo-physical property wrappers, the component library and the solution algorithm are discussed with particular emphasis on the ORC with liquid-flooded expansion. A thorough validation both at component and cycle levels is proposed by considering the aforementioned cycle architectures.
Research Interests:
Current studies indicate that the method of economized vapor injection (EVI) increases both cooling capacity and coefficient of performance (COP) of vapor compression systems and enlarges the operating range of compressors by reducing the... more
Current studies indicate that the method of economized vapor injection (EVI) increases both cooling capacity and coefficient of performance (COP) of vapor compression systems and enlarges the operating range of compressors by reducing the discharge temperature. The design and analysis of EVI systems require comprehensive and comparable performance data of the compressor. In this work, a thermodynamic model was developed to simulate the potential benefit of EVI systems. Furthermore, the performance of a vapor injection (VI) scroll compressor has been experimentally investigated using a modified compressor calorimeter and the refrigerant mixture R407C. During the experiments, the injection flow was regulated by controlling the injection superheat. The experimental results confirm the predicted tendencies of the EVI model. The investigation also reveals that the injection pressure affects the VI compressor performance and needs to be included in the compressor performance evaluation.
Research Interests:
In recent years, research on economized vapor injected (EVI) compression systems showed potential improvements to both cooling capacity and coefficient of performance (COP). In addition, the operating range of compressors can be extended... more
In recent years, research on economized vapor injected (EVI) compression systems showed potential improvements to both cooling capacity and coefficient of performance (COP). In addition, the operating range of compressors can be extended by reducing the discharge temperature. However, the optimum operation of such systems is directly related to the amount of refrigerant charge, which often is not optimized. Therefore, an accurate charge estimation methodology is required to further improve the operation of EVI compression systems. In this paper, a detailed cycle model has been developed for the EVI compression system. The model aims to predict the performance of EVI systems by imposing the amount of required refrigerant charge as an input. In the cycle model, the EVI compressor was mapped based on the correlation of Tello-Oquendo et al. (2017), whereas evaporator, condenser and economizer heat exchanger models were constructed based on the available ACHP models (Bell, 2015). With re...
Research Interests:
This paper assesses the application of the second-law of thermodynamics in a military Environmental Control Unit (ECU) to evaluate the exergy destruction (or irreversibility) in each component when operating at high ambient temperature.... more
This paper assesses the application of the second-law of thermodynamics in a military Environmental Control Unit (ECU) to evaluate the exergy destruction (or irreversibility) in each component when operating at high ambient temperature. Experimental testings were conducted on three ECUs, 1.5 (5.3 kW), 3 (10.6 kW), and 5 (17.6 kW) tons of refrigeration (RT), to assess the potential contribution of each component to enhance the overall energy efficiency of the system, and to determine the feasibility of the thermodynamic model presented herein. The analysis provided for extreme high ambient conditions up to 51.7 °C (125 °F). The results yielded that the highest irreversibility was associated with compressors (32.4% to 42.5%). This is followed by the heat exchanges (19.6% to 32.9%) in the case of 1.5-RT and 3-RT units, whereas for the 5-RT unit, the highest irreversibility was associated with the evaporator followed by the one of the compressors. In the 3-RT ECU, the condenser’s second...