Investigation of waste heat recovery system at supercritical conditions with vehicle drive cycles

Waste heat recovery (WHR) for internal combustion engines in vehicles using Organic Rankine cycle (ORC) has been a promising technology. The operation of the ORC WHR system in supercritical conditions has a potential to generate more power output and thermal efficiency compared with the conventional subcritical conditions. However, in supercritical conditions, the heat transfer process in the evaporator, the key component of the ORC WHR system, becomes unpredictable as the thermo-physical properties of the working fluid change with the temperature. Furthermore, the transient heat source from the vehicle’s exhaust makes the operation of the WHR system difficult. We investigated the performance of the ORC WHR system at supercritical conditions with engine’s exhaust data from real city and highway drive cycles. The effects of operating variables, such as refrigerant flow rates, evaporator and condenser pressure, and evaporator outlet temperature, on the performance indicators of the WHR system in supercritical conditions were examined. Simulation of operating parameters and the boundary of the WHR system are also included in this paper

Experimental and thermodynamic analysis of a bottoming Organic Rankine Cycle (ORC) of gasoline engine using swash-plate expander

This paper deals with the experimental testing of an Organic Rankine Cycle (ORC) integrate in a 2 liter turbocharged gasoline engine using ethanol as working fluid. The main components of the cycle are a boiler, a condenser, a pump and a swash-plate expander. Five engine operating points have been tested, they correspond to a nominal heat input into the boiler of 5, 12, 20, 25 and 30 kW. With the available bill of material based on prototypes, power balances and cycles efficiencies were estimated, obtaining a maximum improvement in the ICE mechanical power and an expander shaft power of 3.7% and 1.83 kW respectively. A total of 28 steady-state operating points were measured to evaluate performance of the swash-plate expander prototype. Operating parameters of the expander, such as expander speed and expansion ratio, were shifted. The objective of the tests is to master the system and understand physical parameters influence. The importance of each parameter was analyzed by fixing all the parameters, changing each time one specific value. In these sensitivity studies, maximum ideal and real Rankine efficiency value of 19% and 6% were obtained respectively.This work is part of a research project called "Evaluation of bottoming cycles in IC engines to recover waste heat energies" funded by a National Project of the Spanish Government with reference TRA2013-46408-R.Galindo, J.; Ruiz Rosales, S.; Dolz Ruiz, V.; Royo Pascual, L.; Haller, R.; Nicolas, B.; Glavatskaya, Y. (2015). Experimental and thermodynamic analysis of a bottoming Organic Rankine Cycle (ORC) of gasoline engine using swash-plate expander. Energy Conversion and Management. 103:519-532. https://doi.org/10.1016/j.enconman.2015.06.085S51953210

Energy performance of buildings : bridging the gap between research and practice

peer reviewedA method to bridge the gap between research and practice, as far as estimation of the building envelope Heat Loss Coefficient is concerned, is to perform measurement of indoor temperature profiles during unoccupied periods when the solar heat gains are sufficient to reach significant indoor-outdoor temperature differences. An observation of indoor temperature profiles was conducted during summer 2014 in a passive house located in Belgium. The observation includes periods with and without occupancy. Occupants were asked to describe their behavior regarding windows opening, closing of external blinds, opening of internal doors. Electric devices were listed and the electricity consumption profile was characterized during occupancy and no occupancy. A calibration process is performed in order to reproduce the global heat balance of the whole building and the zone by zone heat balance. The calibrated model provides an estimation of the Building Heat Loss Coefficient. The influence of the assumptions related to occupants’ behavior in summer is confirmed and recommendations are made to better describe that behavior in terms of use of mechanical ventilation, internal doors opening and use of external blinds

Experimental characterization of a hermetic scroll expander for use in a micro-scale Rankine cycle

This paper presents the results of an experimental study carried out on a prototype of a hermetic scroll expander, integrated into a gas cycle test rig, whose working fluid is HFC-245fa. This system was designed to test only the performance of the expander. It is mainly made up of a scroll compressor, a scroll expander, a heat exchanger and a by-pass valve. The latter is used to adjust the pressure ratio imposed to the expander. The expander is originally a compressor designed for heat pump applications and characterized by a nominal power input of 2.5 kWe. Performance of the expander is evaluated in terms of isentropic effectiveness and filling factor as function of the main operating conditions. The study also investigates the impact of oil mass fraction on the expander performance. Maximum overall isentropic effectiveness of 71.03% is measured, which is partly explained by the good volumetric performance of the machine. Using the experimental data, parameters of a semi-empirical simulation model of the expander are identified. This model is used to analyze the measured performance of the expander. Finally, a polynomial empirical model of the expander is proposed for fast and robust simulations of ORC systems

A clinical correlation between hypozincemia and tinnitus.

We examined a group of 115 patients suffering from tinnitus and have attempted to find a statistically significant correlation between the tinnitus experienced and low blood zinc levels (hypozincemia). No particular correlation could be made between the nature of the tinnitus experienced and hypozincemia except for the continuation of head noises, these being more frequently associated with hypozincemia when they are intermittent. Two hypotheses of pathogenesis are proposed to explain this phenomenon and are based on the importance of zinc to the syntheses of enzymes and proteins

Des pustules stériles à hypopion

La pustulose de Sneddon-Wilkinson reste une pathologie rare, chronique et bénigne atteignant surtout les femmes caucasiennes d’âge moyen. Elle se caractérise par des pustules aseptiques flasques non folliculaires entourées d’une fine aréole érythémateuse et se groupant de façon circinée. Un niveau liquidien ou hypopion peut être visible au sein des pustules les plus volumineuses. Ces dernières se dessèchent, forment des croûtes mellicériques et s’effacent en laissant des macules hyperpigmentées. L’affection atteint principalement le tronc, la racine des membres et le voisinage des grands plis. L’association à une gammapathie monoclonale, surtout de type IgA, est fréquente et doit être systématiquement recherchée. Le traitement de choix est la disulone. Néanmoins, la colchicine constitue une alternative intéressante. La rareté de l’affection et sa présentation clinique didactique justifient l’intérêt de notre cas