References of "Braun, James"
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See detailInnovative architecture to valorize the waste heat of a passenger car through the use of a Rankine cycle
Dumont, Olivier ULiege; Diny, Mouad; Lemort, Vincent ULiege et al

in Proceedings of purdue conference 2018 (2018)

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See detailA general methodology for optimal load management with distributed renewable energy generation and storage in residential housing
Georges, Emeline ULiege; Braun, James; Lemort, Vincent ULiege

in Journal of Building Performance Simulation (2016)

In the US, buildings represent around 40% of the primary energy consumption and 74% of the electrical energy consumption [U.S. Department of Energy (DOE). 2012. 2011 Buildings Energy Data Book. Energy ... [more ▼]

In the US, buildings represent around 40% of the primary energy consumption and 74% of the electrical energy consumption [U.S. Department of Energy (DOE). 2012. 2011 Buildings Energy Data Book. Energy Efficiency & Renewable Energy]. Incentives to promote the installation of on-site renewable energy sources have emerged in different states, including net metering programmes. The fast spread of such distributed power generation represents additional challenges for the management of the electricity grid and has led to increased interest in smart control of building loads and demand response programmes. This paper presents a general methodology for assessing opportunities associated with optimal load management in response to evolving utility incentives for residential buildings that employ renewable energy sources and energy storage. An optimal control problem is formulated for manipulating thermostatically controlled domestic loads and energy storage in response to the availability of renewable energy generation and utility net metering incentives. The methodology is demonstrated for a typical American house built in the 1990s and equipped with a single-speed air-to-air heat pump, an electric water heater and photovoltaic (PV) collectors. The additional potential associated with utilizing electrical batteries is also considered. Load matching performance for on-site renewable energy generation is characterized in terms of percentage of the electricity production consumed on-site and the proportion of the demand covered. For the purpose of assessing potential, simulations were performed assuming perfect predictions of the electrical load profiles. The method also allows determination of the optimal size of PV systems for a given net metering programme. Results of the case study showed significant benefits associated with control optimization including an increase of load matching between 3% and 28%, with the improvement dependent on the net metering tariff and available storage capacity. The estimated cost savings for the consumer ranged from 6.4% to 27.5% compared to no optimization with a unitary buy-back ratio, depending on the available storage capacity. Related reduction in CO2 emissions were between 11% and 46%. Optimal load management of the home thermal systems allowed an increase in the optimal size of the PV system in the range of 13–21%. [less ▲]

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See detailSimulation of a cold climate heat pump furnished with a scroll compressor with multiple injection lines
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in Proceedings of the International Conference on Compressors and their Systems 2013 (2013, September)

A detailed scroll compressor simulation has been developed as described in a companion paper. In this work, the compressor simulation code is used to investigate vapor injection in scroll compressors for ... [more ▼]

A detailed scroll compressor simulation has been developed as described in a companion paper. In this work, the compressor simulation code is used to investigate vapor injection in scroll compressors for cold climate heat pumps. The required analysis is developed for vapor injection in scroll compressors with one or two injection lines. The improvement in heat pump efficiency at a -20 C evaporation temperature with one injection line is as much as 10% while with two injection lines the increase in efficiency can be as much as 16% [less ▲]

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See detailExperimental Testing of an Oil-Flooded Hermetic Scroll Compressor
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Journal of Refrigeration (2013), 36

In this work, a residential air conditioning compressor designed for vapor injection has been modified in order to inject large quantities of oil into the working chamber in order to approach an ... [more ▼]

In this work, a residential air conditioning compressor designed for vapor injection has been modified in order to inject large quantities of oil into the working chamber in order to approach an isothermal compression process. The compressor was tested with oil injection mass flow fractions of up to 45%. At an evaporating temperature of -10C and condensing temperature of 30C, the overall isentropic efficiency was up to 70% at the highest oil injection rate. Overall, over the testing envelope investigated, there are no significantly negative effects experienced for the compressor and the compressor isentropic efficiency and refrigerant mass flow rate improve monotonically as the oil injection rate is increased. [less ▲]

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See detailDevelopment of a generalized steady-state simulation framework for positive displacement compressors and expanders
Bell, Ian ULiege; Lemort, Vincent ULiege; Groll, Eckhard et al

in Proceedings of the International Conference on Compressors and their Systems 2013 (2013)

In this paper, a generalized framework is presented that can be used to simulate the steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw ... [more ▼]

In this paper, a generalized framework is presented that can be used to simulate the steady-state performance of a wide range of positive displacement compressors and expanders (scroll, piston, screw, rotary, spool, etc.). The complete simulation algorithm is described, and an emphasis is placed on the numerical methods required to obtain robust behavior of the simulation. This formulation has been implemented into an open-source software package entitled PDSim written in the Python language. PDSim is the first open-source generalized compressor and expander simulation package. The source code can be freely obtained from http://pdsim.sf.net [less ▲]

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See detailOptimization of a scroll compressor for liquid flooding
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Journal of Refrigeration (2012), 35(7), 19011913

In two companion papers, simulation models for the working processes of liquid-flooded scroll compressors and expanders have been developed and validated against experimental data. In this study, analytic ... [more ▼]

In two companion papers, simulation models for the working processes of liquid-flooded scroll compressors and expanders have been developed and validated against experimental data. In this study, analytic models are presented for the modes of irreversibility generation in the liquid-flooded scroll compressor including built-in volume ratio maladjustment, pressure drop and leakage. A thermodynamic model is used to derive the ideal volume ratio for a liquid-flooded compressor, which is higher than that of dry compression. An optimum set of built-in volume ratio and scroll base circle radius is found which maximizes the overall isentropic efficiency by minimizing the leakage and pressure drop irreversibilities. The irreversibility generation models are used to optimize a scroll compressor for the Liquid-Flooded Ericsson cycle application. The model predicts scroll compressor overall isentropic efficiency of over 80% (based on the shaft power) at an oil mass fraction of 88%. [less ▲]

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See detailPerformance Comparison of Hydronic Secondary Loop Heat Pump and Conventional Air-Source Heat Pump
Bell, Ian ULiege; Braun, James

in International Refrigeration and Air Conditioning Conference at Purdue, July 16-19, 2012 (2012, July)

In residential heat pump systems, the motivation for secondary loop systems is to allow for the use of flammable or toxic refrigerants with lower global warming potentials than the currently employed HFC ... [more ▼]

In residential heat pump systems, the motivation for secondary loop systems is to allow for the use of flammable or toxic refrigerants with lower global warming potentials than the currently employed HFC refrigerants. The addition of radiant panels as integral building components (embedded in concrete at construction) is becoming more common. Combining the large surface area of the radiant panel and an efficient primary loop, the hydronic secondary loop heat pump system can greatly outperform the conventional air-to-air heat pump. The improvement in coefficient of performance is as much as 38% over the conventional air-to-air heat pump when the secondary loop hydronic system is employed. Due to the large area of the radiant panel, the condensing temperature of the primary loop for the hydronic secondary loop heat pump can be reduced by as much as 5°C at high ambient temperatures. [less ▲]

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See detailDerivation of optimal scroll compressor wrap for minimization of leakage losses
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Compressor Engineering Conference at Purdue, July 16-19, 2012 (2012, July)

The scroll wraps of a scroll compressor play a very important role in the compressor’s efficiency due to their impact on leakage and leakage irreversibilities. In this work, a short summary of the scroll ... [more ▼]

The scroll wraps of a scroll compressor play a very important role in the compressor’s efficiency due to their impact on leakage and leakage irreversibilities. In this work, a short summary of the scroll compressor geometry is presented. Using the geometry of the scroll wraps, an optimal scroll wrap geometry is derived for a given set of constraints on compressor displacement, scroll wrap thickness and volume ratio. This optimal scroll wrap geometry can be used as a starting point for further optimization in a detailed compressor model that includes the effects of mechanical losses. [less ▲]

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See detailLiquid flooded compression and expansion in scroll machines - Part II: Experimental testing and model validation
Bell, Ian ULiege; Lemort, Vincent ULiege; Groll, Eckhard et al

in International Journal of Refrigeration (2012), 35

The use of liquid-flooding in the compression and expansion of non-condensable gas in scroll compressors and expanders enables the possibility of quasi-isothermal working processes. Liquid-flooded scroll ... [more ▼]

The use of liquid-flooding in the compression and expansion of non-condensable gas in scroll compressors and expanders enables the possibility of quasi-isothermal working processes. Liquid-flooded scroll machines were installed in a fully-instrumented Liquid- Flooded Ericsson Cycle test rig to conduct entire cycle performance tests. In addition, detailed compressor and expander performance data was obtained. Oil mass fractions of up to 92% and 76% were added to the gas entering the scroll compressor and expander respectively. The overall isentropic efficiency of the scroll compressor based on the shaft power with flooding was up to 73% and the volumetric efficiency was above 92%. For the expander, the best overall isentropic and volumetric efficiencies achieved were 66% and 105% respectively. The mechanistic model presented in the companion paper was vali- dated against the experimental data for both the compressor and the scroll expander with good agreement, though the agreement is better for the scroll compressor. [less ▲]

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See detailLiquid-flooded compression and expansion in scroll machines - Part I: Model development
Bell, Ian ULiege; Lemort, Vincent ULiege; Groll, Eckhard et al

in International Journal of Refrigeration (2012)

A detailed mechanistic model has been developed for scroll compressors and scroll expanders with liquid flooding for application to the Liquid Flooded Ericsson Cycle. This model is based on the ... [more ▼]

A detailed mechanistic model has been developed for scroll compressors and scroll expanders with liquid flooding for application to the Liquid Flooded Ericsson Cycle. This model is based on the integration of a set of differential equations that arise from the conservation laws. The impact of the flooding liquid on the working process is also included through mixture properties as well as treatment of two-phase flow pressure drop. With the working process known, it is then possible to solve for the compressor power, total mass flow rate and other model outputs. The fine level of detail in the model allows for the investigation of the impact of design changes to the scroll machines. This model can also be readily extended to allow for the analysis of liquid flooded vapor compression refrigeration. [less ▲]

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See detailPerformance of vapor compression systems with compressor oil flooding and regeneration
Bell, Ian ULiege; Groll, Eckhard; Braun, James

in International Journal of Refrigeration (2011), 34(1), 225233

Vapor compression refrigeration technology has seen great improvement over the last several decades in terms of cycle efficiency through a concerted effort of manufacturers, regulators, and research ... [more ▼]

Vapor compression refrigeration technology has seen great improvement over the last several decades in terms of cycle efficiency through a concerted effort of manufacturers, regulators, and research engineers. As the standard vapor compression systems approach practical limits, cycle modifications should be investigated to increase system efficiency and capacity. One possible means of increasing cycle efficiency is to flood the compressor with a large quantity of oil to achieve a quasi-isothermal compression process, in addition to using a regenerator to increase refrigerant subcooling. In theory, compressor flooding and regeneration can provide a significant increase in system efficiency over the standard vapor compression system. The effectiveness of compressor flooding and regeneration increases as the temperature lift of the system increases. Therefore, this technology is particularly well suited towards lower evaporating temperatures and high ambient temperatures as seen in supermarket refrigeration applications. While predicted increases in cycle efficiency are over 40% for supermarket refrigeration applications, this technology is still very beneficial for typical air-conditioning applications, for which improvements in cycle efficiency greater than 5% are predicted. It has to be noted though that the beneficial effects of compressor flooding can only be realized if a regenerator is used to exchange heat between the refrigerant vapor exiting the evaporator and the liquid exiting the condenser. [less ▲]

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See detailUpdate on Scroll Compressor Chamber Geometry
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Compressor Engineering Conference at Purdue (2010, July)

The geometry of the scroll compressor determines the efficiency of the scroll compressor and controls all elements of its operation. It is therefore critical to be able to accurately model the volumes of ... [more ▼]

The geometry of the scroll compressor determines the efficiency of the scroll compressor and controls all elements of its operation. It is therefore critical to be able to accurately model the volumes of the compressor over the course of a revolution. This paper proposes a novel quasi-analytic formulation of the suction, compression and discharge chambers based on a change of variables from involute angle to polar integration angle. This solution has been compared against a reference polygon solution, and for the suction chamber this solution agrees to within 0.02%. The solutions for the compression and discharge chamber volumes are analytic and incur a negligible penalty to overhead of a detailed compressor model. In addition, the general nature of the solution presented allows for multiple compression chambers and more complex discharge geometry. [less ▲]

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See detailImpact of Oil Solubility and Refrigerant Flashing on the Performance of Transcritical CO2 Vapor Compression Systems with Oil Flooding and Regeneration
Bell, Ian ULiege; Groll, Eckhard; Braun, James et al

in International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2010 (2010, July)

Flooding the compressor of a vapor compression system with oil can allow for a more isothermal compression process. This can lead to significant improvements in performance, particularly when combined ... [more ▼]

Flooding the compressor of a vapor compression system with oil can allow for a more isothermal compression process. This can lead to significant improvements in performance, particularly when combined with a regenerative heat exchanger. For CO2 cycles with supercritical heat rejection, the superheat horn and throttle are major sources of irreversibility. The combination of flooding and regeneration attacks both of these losses with a relatively small impact on system costs. The improvement in system COP can be over 20% for sink and source temperatures of 30°C and -30°C, respectively, with an optimized oil mass fraction and oils that have low refrigerant solubility. However, when some amount of refrigerant is solved in the oil, the cooling capacity is decreased. At a refrigerant solubility of 20% by mass in the oil for fixed oil mass fraction, there is no improvement in system COP compared to the baseline system. [less ▲]

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