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A very high accuracy, straight vibrating tube type of density flow meter has been used online to measure oil concentraiton of flowing R-134a/oil mixtures. The calibrations covered oil concentrations from 0-6 wt.% oil over the temperature range from -9.4 to 5.9°C. The oil concentrations were correlated statistically as a function of density, temperature and liquid compressibility to an average error of 0.09 wt.% oil with a 95% confidence limit of 0.21 wt.% oil. In addition, a simplified method not requiring

Intube evaporation tests for R-407C and R-407C/oil are reported for a plain copper tube. The tests were run at a nominal inlet pressure of 6.45 bar (93.5 psia) at mass velocities of 100, 200 and 300 kg/m2s (73581, 147162 and 220743 lb/h ft2) over nearly the entire vapor quality range. Pure R-407C performed very similar to pure R-134a run previously in similar tests at all three mass velocities, differing only at high vapor qualities where the peaks in href vs. x were shifted slightly. For local vapor qualit

A new flow boiling model and generalized correlation are presented for evaporation inside of horizontal microfin tubes. The enhancement model incorporates the effects of the microfins on liquid-phase convection and nucleate boiling. The method predicts microfin test data for R-134a and R-123 over the mass velocity range from 100-500 kg/m2s, vapor qualities from 15- 85% and heat fluxes from 2-47 kW/M2. The model is the first general type of method to become available and can be applied to any 2-dimensional m

The effects and the consequences of transferring the ignition point of the conventional combustion chamber into a small unscavenged prechamber were evaluted through a numerical simulation based on the CFD-code KIVA- 3V. The prechamber flow characteristics at the location of the gap between the spark plug electrodes and in the crank angle period where the ignition is expected to occur were compared to the corresponding conditions in the conventional combustion chamber. The influence of the prechamber geometr

Intube evaporation tests for R-407C and R-407C/oil are reported for a microfin tube. The tests were run at a nominal inlet pressure of 6.45 bar (93.5psia) at mass velocities of 100, 200 and 300 kg/m2s (73581, 147162 and 220743 lb/h ft2) over nearly the entire vapor quality range. Pure R-407C performed similar to previous pure R-134a tests at the highest mass velocity, but lower for the other mass velocities, at similar operating conditions. Any amount of oil tended to decrease local R-407C micorfin heat tra

Concern for the environment has been steadily growing in recent years, and it is becoming more common to include environmental impact and pollution costs in the design problem along with construction, investment and operating costs. To economically respond ...

A medium size diesel engine converted to natural gas operation on the Otto principle has been studied under stoichiometric and lean burn operation in order to evaluate the potential to reduce the NOX exhaust gas emissions below the stringent limit prescribed by the Swiss Federal Clean Air Act - 250 mg/mN3, 5 % O2 (at normal (N) conditions, 5 % residual oxygen and dry). While both operational modes fulfill the prescribed NOX limit, lean burn operation, combined with turbocharging, provides a higher brake pow

The Second Law of thermodynamics is known to be an essential guide for the improvement of energy conversion systems. Throughout the years it has been applied to various engineering methods in particular in methods based on exergy [1] including the 2nd Law, ...

Two-phase flow pattern data have been obtained experimentally for R-407C flowing inside 12 mm bore sight glasses, which were located at the outlets of 3 m long, plain bore copper tube heat transfer test sections. The tests covered nominal mass velocities of 100, 200 and 300 kg/m2s, vapor qualities from 5-95%, and a wide range of heat fluxes, all taken at a fixed inlet saturation pressure of 6.45 bar to the evaporator test section. The flow pattern data were compared to the newly developed two-phase frow pat

Understanding mechanisms that affect degradation and durability of solid oxide fuel cell (SOFC) stacks and systems is becoming increasingly important as systems are being deployed around the world. A novel simulation approach accounting for state-of-the-art understanding of degradation mechanisms in the context of an operating SOFC system has been developed. Investigative tools simulating lifetime degradation have been applied to a physical SOFC system model designed and controlled to allow dynamic dispatch

Exergetic analysis is derived from the First and Second Laws of thermodynamics is shown to be an excellent tool to analyse and characterize industrial processes. A coherent link to pinch technology is shown which allows the designer to extend design considerations to friction and equipment fabrication losses. Paths to extend the approach to other environmental factors are also indicated. Applications examples linked to Organic Rankine cycles, plaster drying or distillation of chemical products are briefly a

LENI activities in SOFC are focused on development of a new planar stack concept based on anode supported cells in collaboration with the company HTceramix SA. Modeling of repeat element, stack and systems is starting in parallel. This work presents a mode ...

Details of the reliability and availability aspects of the thermoeconomic methodology presented in Part I (Olsommer et al., 1999) are given here in Part II of our series of two articles. These system details cannot be forgotten, particularly if the superconfiguration envisioned offers the choice of several technologies for the same function (redundancy) or if there are guarantees of availability which must be met. An original method, which is an extension of the event space method, is presented here for aut

The technology gap between liquid and gaseous fuels presents an obstacle in realising the environmental and performance potential of CNG vehicles. Therefore a gaseous fuel injector has been developed to cope with the considerable larger volume flow rated required for a gaseous fuel without additional penalties in response time. This injector has demonstrated a significant potential to reduce emissions from natural gas powered engines during transient operation.

Compared to other breweries, Brasserie du Cardinal achieves low specific energy consumption without applying “new” technologies like cogeneration or mechanical vapour recompression (MVR). MVR has been advocated for most types of breweries [1]. This case study shows how pinch technology (PT) helps in assessing the actual opportunity for an MVR system to be applied and highlights the corresponding need for extended heat recovery (HR). The study was carried out at Laboratoire d’énergétique industrielle (LENI)

For the most part, district heating demands can be met by an appropriate intergration of cogeneration and heat pumps units provided that advantages is taken of the fact that many urban regions are concentrated around surface waters. Despite the fact that the economics at the moment are unfavourable, substantial environmental improvements point to the promise of these concepts. Several district heating concepts using centralized and sometimes decentralized heat pumps are currently under study at the EPFL. A

The presence of oil in domestic heat pumps is a hindrance, particularly for enhanced surface evaporators and for advanced concepts based on two-stage cycles. Very compact oil-free dynamic compressor directly driven by high speed electric motors and supported on refrigerant vapor bearings represent a promising alternative. This paper presents a design analysis of the first stage prototype with the various tradeoffs between the impeller characteristics to follow the seasonable heat demand, the bearing and rot

Because of its non-toxicity and its availability steam is frequently used as an energy carrier in industrial processes. Steam is also the by-product of energy intensive processes such as drying, concentration, evaporation and distillation. Although the upgrading concept of open cycle heat pump, commonly called mechanical vapour recompression (MVR), has been known and applied from the beginning of the century, low pressure steam from many industrial processes has traditionally been vented away with its valua

A model for planar solid oxide fuel cell repeat elements and stacks has been developed. Distribution of concentrations, reaction rates and temperatures (both gases and solids) are computed as well as overall performance results. Specific experiments provide inputs to the model by a parameter estimation method. The modeling approach developed allows to compare several configurations. As the number of design parameters is large (from cell size, component thicknesses to gas flow configuration), the model is de

Results on solid oxide fuel cell stacks tested at 800° C with H2 fuel and using planar Ni-zirconia anode supported cells, 80x80x0.2 mm in size, are presented. Modeling and numerical simulation is used to interpret observed results and develop improved desi ...

Daniel Favrat

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Online Measurement of Oil Concentrations of R134a–Oil Mixtures with a Density Flowmeter

Intube Flow Boiling of R-407C and R-407C/Oil Mixtures. Part 2: Plain Tube Results and Predictions

Evaporation in Microfin Tubes: A Generalized Prediction Model.

Investigation of the prechamber geometrical configuration of a natural gas spark ignition engine for cogeneration: part. I, numerical simulation

Intube Flow Boiling of R-407C and R-407C/Oil Mixtures. Part 1: Microfin Tube

Environomic multi-objective optimisation of a district heating network considering centralized and decentralized heat pumps

Study of a Small Size Cogeneration Gas Engine in Stoichiometric and Lean Burn Modes: Experimentation and Simulation

Thermodynamics and the optimisation of energy systems: Strengths and Limits

Prediction of Two-Phase Flow Patterns for Evaporation of Refrigerant R–407C Inside Horizontal Tubes.

The Effects of Dynamic Dispatch on the Degradation and Lifetime of Solid Oxide Fuel Cell Systems

Exergy and Environmental Considerations in Process Integration

Modeling of cross-flow stack: sensitivity to thermal properties of the materials

An Approach for the Time-Dependent Thermoeconomic Modeling and Optimization of Energy System Synthesis, Design and Operation (Part II : Reliability and Availability)

Ultra Rapid Natural Gas Port Injection.

Process Integration Study at Brasserie du Cardinal: Energy and Cost Savings Opportunities Using Mechanical Vapour Recompression (MVR).

Cogénération et pompe à chaleur. Utilisation pour les réseaux de chauffage urbain

High-Speed Low Power Radial Turbocompressor For Oil-Free Heatpumps

Use of a twin screw compressor for steam compression

Generalized model of planar SOFC repeat element for design optimization

Modeling and experimental validation of solid oxide fuel cell materials and stacks