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See detailUnveiling the mystery of Combined Heat & Power (cogeneration)
Verbruggen, Aviel; Dewallef, Pierre ULg; Quoilin, Sylvain ULg et al

in Energy (2013), 61

The article unveils the mystery of cogeneration. Cogeneration is an add-on or embedded activity in thermal power plants, with as merit the use of part or whole of their point source heat exhausts. EU's ... [more ▼]

The article unveils the mystery of cogeneration. Cogeneration is an add-on or embedded activity in thermal power plants, with as merit the use of part or whole of their point source heat exhausts. EU's talk of “high-efficiency cogeneration” is an unfounded transfer of responsibility from the hosting thermal power generation plant onto CHP (Combined Heat & Power) activity. The quality of a CHP activity is univocally defined by its design power-to-heat ratio σ, a tombstone parameter derived from the design characteristics of the power plant. A thermal power plant may house more than one cogeneration activity. Identifying σ requires positioning the bliss point in the electricity–heat production possibility set of the cogeneration activity. The bliss point is where after electric output is maximized, the sum of that output and the maximum recoverable quantity of heat occurs. Once CHP's mystery of virtual bliss points is unveiled, the proper σ are found. With known σ by CHP activity, the quantity of cogenerated electricity is reliably assessed as best indicator of cogeneration performance. Our analysis is applicable on all relevant thermal power cycles that host CHP activities, and illustrated with a numerical example. Our lean method is necessary and sufficient for proper CHP regulation. [less ▲]

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See detailExperimental study on an open-drive scroll expander integrated into an ORC (Organic Rankine Cycle) system with R245fa as working fluid
Declaye, Sébastien ULg; Quoilin, Sylvain ULg; Guillaume, Ludovic ULg et al

in Energy (2013), 15

The present paper focuses on the experimental characterization of an open-drive scroll expander integrated into an Organic Rankine cycle using R245fa as working fluid. The expander is a commercially ... [more ▼]

The present paper focuses on the experimental characterization of an open-drive scroll expander integrated into an Organic Rankine cycle using R245fa as working fluid. The expander is a commercially available air compressor that was modified to operate in expander mode. The ORC (Organic Rankine Cycle) system is designed for a nominal heat input of 20 kW and a nominal net power output of 1.8 kW. A total of 74 steady-state operating points are measured to evaluate the expander performance over a wide range of conditions. The operating parameters that are varied include the inlet pressure (from 9 to 12 bar), outlet pressure (from 1.5 to 4 bar) and rotational speed (from 2000 to 3500 rpm). The maximum isentropic efficiency and shaft power are, respectively, 75.7% and 2.1 kW. A maximum cycle efficiency of 8.5% is reached for evaporating and condensing temperatures of 97.5 °C and 26.6 °C respectively. For most of the tests, hot water is produced in the condenser and the system therefore behaves as a CHP (combined heat and power). Depending on the water temperature requirement, a power to heat ratio varying between 1.9% and 11.8% is obtained. Water over 50 °C can be produced with a power to heat ratio higher than 8%. The experimental data points are then used to generate a performance map of the expander. This performance map allows for simulation of the use of such an expander in other ORC system [less ▲]

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See detailInfluence of fuel type, dilution and equivalence ratio on the emission reduction from the auto-ignition in an Homogeneous Charge Compression Ignition engine
Machrafi, Hatim ULg; Cavadias, Simeon; Amouroux, Jacques

in Energy (2010), 35(4), 1829-1838

One technology that seems to be promising for automobile pollution reduction is the Homogeneous Charge Compression Ignition (HCCI). This technology still faces auto-ignition and emission-control problems ... [more ▼]

One technology that seems to be promising for automobile pollution reduction is the Homogeneous Charge Compression Ignition (HCCI). This technology still faces auto-ignition and emission-control problems. This paper focuses on the emission problem, since it is incumbent to realize engines that pollute less. For this purpose, this paper presents results concerning the measurement of the emissions of CO, NOx, CO2, O-2 and hydrocarbons. HCCI conditions are used, with equivalence ratios between 0.26 and 0.54, inlet temperatures of 70 degrees C and 120 degrees C and compression ratios of 10.2 and 13.5, with different fuel types: gasoline, gasoline surrogate, diesel, diesel surrogate and mixtures of n-heptane/toluene. The effect of dilution is considered for gasoline, while the effect of the equivalence ratio is considered for all the fuels. No significant amount of NOx has been measured. It appeared that the CO, O-2 and hydrocarbon emissions were reduced by decreasing the toluene content of the fuel and by decreasing the dilution. The opposite holds for CO2. The reduction of the hydrocarbon emission appears to compete with the reduction of the CO2 emission. Diesel seemed to produce less CO and hydrocarbons than gasoline when auto-ignited. An example of emission reduction control is presented in this paper. (C) 2010 Elsevier Ltd. All rights reserved. [less ▲]

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See detailComputer simulation of a bivalent heating installation
Nicolas, Jacques ULg; Poncelet, Jean-Pol

in Energy (1986), 11(6), 551-562

A computer simulation program for a dwelling heating installation has been developed and tested. It uses principles and defined parameters, with simplifications to reduce the program size and execution ... [more ▼]

A computer simulation program for a dwelling heating installation has been developed and tested. It uses principles and defined parameters, with simplifications to reduce the program size and execution time. Integration of the differential equations describing the heat transfer in the system is performed with constant time steps (explicit scheme). The program is utilized to study the performance of the heating system and to perform parametric studies to determine the effects of changes in various parameters on performance. The influence of the time increment, thermal insulation, heat capacity and of other parameters on system performance has been analyzed. Included in the regulation software of a control system, the program is a design tool to optimize regulation and help in developing and testing modern regulators. [less ▲]

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