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This study presents the numerical development of a generator–rectifier combined component (called a “combined-generator”) composed of plate heat exchangers, designed and meant to be integrated in a single-stage ammonia–water absorption cooling system. Investigations are made to find the most compact and efficient design. Numerical simulations are presented describing parameters such as the ammonia fraction in the vapor produced and the combined generator efficiency as a function of the inlet temperatures or mass flow rate of the heat transfer fluid. The combined generator produces vapor with a high ammonia mass fraction and high mass efficiency for a solution inlet temperature range of [315–320 K] and a mass flow rate of the heat transfer fluid between [0.4 and 0.6 kg.s−1]. The impacts of the length and number of plates as well as the adiabatic/heated ratio of the plates are also examined. The ammonia fraction increases with the increase in the adiabatic/heated ratio, and the combined generator efficiency increases with the increase in the plate aspect ratio of length/width. The proposed system is developed to be operated in compact and medium-capacity absorption chillers (approximately 5 kW cold) for air-conditioning.

Thermodynamic and exergoeconomic assessment of a combined cooling and power cycle  Study based on an existing ammonia water experimental prototype  Scale-up of the considered plant predicted to reach exergy efficiency around 24%  Unit cost of produced exergy of 28.

Given the ever-increasing global demand for energy and the attention to be paid to environmental issues and climate change, research is developing more and more about new cold production technologies using renewable sources or recovery. This cooling demand is mainly covered by technologies conventional machines, in particular vapor compression machines, which leads to a high increased demand for electricity. In this context, absorption systems (Herold et al. 2016), lend themselves well to the recovery of heat at low temperature for the production of cold. The advantage of these machines is that the mechanical compression is replaced by a compression thermochemical that uses heat. Although characterized by a low level of maturity technology (TRL 3-4), an even more ambitious study concerns combined systems based on exploitation of thermal energy at low temperatures, in which electrical power and cooling are produced in the same cycle. The present work focuses on the analysis of a pilot installation (Figure 1) of combined production cooling and electricity (CFE) in parallel, from a low temperature source [80 -150°C] and from maximum thermal power of the generator 15 kW.

International audience; Ejector refrigeration cycles offer an alternative to traditional systems for the production of cooling using low temperature heat. In this paper, a real gas thermodynamic model based on the mass flow rate maximisation is presented. This model has the advantage of simplifying the calculation algorithm and avoiding a complex description of the double choking mechanism taking place within the ejector. First, the model hypothesis and calculation algorithm are presented. The impact of each efficiency is evaluated and a tuning procedure is developed to calibrate the model on experimental data. Validation is performed on multiple datasets relative to two different fluids: R600a and R134a. The ejector model is then used to simulate a SERS (single ejector refrigeration system) cycle, to validate its robustness and capability to be used in the prediction of thermodynamic cycles performance. A comparative analysis of different fluids is carried out on the SERS, highlighting the important role played by the choice of the superheating. Finally, the model is used to predict performance in the case of a two-phase primary flow pointing out the limits of the model and the need of further experimental studies for the inclusion of appropriate semi-empirical corrections.

Summary Background Cryptococcal meningitis has fatality rates of 40%‐70%, resulting in 200 000 deaths each year. The best outcomes are achieved with amphotericin combined with flucytosine but flucytosine is expensive and unavailable where most disease occurs. More effective and affordable treatments are needed. Tamoxifen, a selective oestrogen receptor modulator frequently indicated for breast cancer, has been found to have synergistic activity against the Cryptococcus neoformans type strain when combined with amphotericin or fluconazole. It is cheap, off‐licence, widely available and well‐tolerated, and thus a pragmatic potential treatment for cryptococcal disease. Objectives We wanted to determine the susceptibility of clinical isolates of C. neoformans to tamoxifen alone and in combination with other antifungals, to determine whether there is sufficient evidence of activity to justify a clinical trial. Methods We used the CLSI broth microdilution protocol to test the susceptibility of 30 randomly selected clinical isolates of C. neoformans to tamoxifen, in dual combination with amphotericin, fluconazole or flucytosine, and in triple combination with amphotericin and fluconazole. Evidence of drug interactions was assessed using the fractional inhibitory concentration index. Results The MIC50 and MIC90 of tamoxifen were 4 and 16 mg/L, respectively. The combination of tamoxifen and amphotericin suggested a synergistic interaction in 20 of 30 (67%) isolates. There was no interaction between tamoxifen and either fluconazole or flucytosine. Synergy was maintained in 3‐Dimensional chequerboard testing. There was no evidence of antagonism. Conclusions Tamoxifen may be a useful addition to treatment with amphotericin and fluconazole for cryptococcal meningitis; a trial is justified.

International audience

International audience; The present work is focused on the investigation of an absorption cycle integrated with an impulse axial turbine for the combined production of cooling and electric power. This technology holds great promise for its ability to harness low-temperature heat sources, more effciently in comparison to separate production with simple cycles. By developing a 1D model of the expander, and integrating it into a 0D model of the complete cycle, it is possible to evaluate the performance of the cycle and its variation with respect to the operating parameters, namely the temperature of the external resources. Pending an experimental validation of the results, this study showed the importance of correctly defining the temperature of the sources - namely the generator temperature - in order to satisfy the technological needs while also maximising the effciency of the cycle. Finally it was highlighted how the integration of a supersonic impulse turbine strongly limits the flexibility during operation given the constant mass flow rate treated by the expander.

Cryptococcus neoformans most frequently causes disease in immunocompetent patients. However, in Vietnam and east Asia, disease is frequently reported in apparently immunocompetent patients. We have previously shown that almost all such disease is due to a specific lineage of C. neoformans – VNIa-5. However, in HIV infected patients, infections due to this lineage are not associated with worse outcomes. Here, we demonstrate that the VNIa-5 presents different virulence phenotypes depending on its source. Isolates derived from immunocompetent patients are more virulent than those from HIV infected patients or the environment. Moreover, the virulence phenotype is plastic – sterile culture filtrate from highly virulent VNIa-5 strains can induce increased virulence in less virulent VNIa-5 isolates, which in turn can then induce increased virulence in their low virulence states. We present evidence that this phenomenon is driven by secreted proteins associated with extra-cellular vesicles.

Absorption cycles cogenerating cooling and power are anticipated to show favorable performances compared to separate generation systems. Through several models and a few prototypes, different studies validated the ability of cogeneration cycles to work with low-grade heat (lower than 200 °C). The present work aims to characterize and optimize a water-ammonia based cogeneration system of small capacity (cooling production: 5 kW, electricity production: 1 kW). Firstly, an accurate model of a scroll expander is implemented in a complete cogeneration cycle to simulate the power production. The effects on the expander of both the water/ammonia fraction and temperature of the expanded fluid are analyzed, providing a better understanding of the impacts of the rectifier and of the super-heater on the global cycle performances. Secondly, to foresee the cycle performance, a dual-objective optimization algorithm maximizes both cooling and power production according to variable temperature sources. Finally, the dynamic behavior of the cycle is investigated through transient simulations. Such complex systems present significant inertia when starting or switching from one production mode to another (between cooling and power). This study provides some insight on the most critical elements of the cycle.

International audience; Critical heat flux (CHF) in pool boiling experiments corresponds to the heat flux at which a vapor film is formed on the heated surface resulting from the replacement of liquid by vapor adjacent to this surface. Poor thermal conductivity of vapor can severely deteriorate heat transfer. It is important that systems operate below this limit which is a strong limitation to heat transfer due to the huge increase of the thermal resistance near the wall. The concept of macro- and micro-contact angles has been introduced in a previous paper (Phan et al., 2010 [28]) to describe the bubble growth processes. In this paper, an explicit relation between the bubble departure diameter and the contact angle has been presented. Based on these results, we propose a model of critical heat flux, taking into account the effects of the wettability of the fluid, whose property is known to strongly influence boiling heat transfer. A new correlation for CHF, dependent on the contact angle, is proposed. It is found in fair agreement with existing experimental results concerning subcooled boiling to describe the variation of CHF with wettability.

Although the boiling process has been a major subject of research for several decades, its physics still remain unclear and require further investigation. This study aims at highlighting the effects of surface wettability on pool boiling heat transfer. Nanocoating techniques were used to vary the water contact angle from 20 ◦ to 110 ◦ by modifying nanoscale surface topography and chemistry. The experimental results obtained disagree with the predictions of the classical models. A new approach of nucleation mechanism is established to clarify the nexus between the surface wettability and the nucleate boiling heat transfer. In this approach, we introduce the concept of macro- and micro-contact angles to explain the observed phenomenon. To cite this article: H.T. Phan et al., C. R. Mecanique 337 (2009).

International audience; Experiments were performed to study the effects of surface wettability on flow boiling of water at atmospheric pressure. The test channel is a single rectangular channel 0.5 mm high, 5 mm wide and 180 mm long. The mass flux was set at 100 and 120 kg/m² s and the base heat flux was varied from 30 to 80 kW/m². Water enters the test channel under subcooled conditions. The sample surfaces are titanium (Ti) and diamond-like carbon (DLC) surfaces having a contact angle of 49° and 63°, respectively. The experimental results show different flow patterns that impact the heat transfer significantly. Compared to the Ti surface, the DLC surface shows a deterioration of 10% in heat transfer.

International audience; Experiments were performed to study the effects of surface wettability on two-phase pressure drop of flow boiling of water at atmospheric pressure. The test channel is a single rectangular channel 0.5 mm high, 5 mm wide and 180 mm long. The mass flux was set at 100 kg/m2 s and 120 kg/m2 s, respectively. The base heat flux varied from 30 to 80 kW/m2. Water enters the test channel under subcooled conditions. The study has been performed at low exit vapour quality (less than 0.1). The samples are either hydrophilic like Polydimethylsiloxane (SiOx), Titanium (Ti), Diamond-Like Carbon (DLC) or hydrophobic like Polydimethylsiloxane (SiOC). These surfaces have static contact angles of 26 , 49 , 63 and 103 , respectively. It was observed that the total two-phase pressure drop significantly increases with the static contact angle. In particular, the average deviation between the highly-wetted and the unwetted surfaces is about 170%. To explain this observation, the "wetting pressure drop" notion caused by the surface tension forces generated at the triple contact lines is introduced. Afterwards, a model is proposed to predict the wetting pressure drop as a function of the static contact angle. This model shows a good agreement with the experimental data with 86% of the data included within the lines of 20% error.

Colloque avec actes et comité de lecture. Internationale.; International audience; This work investigates the flow boiling heat transfer in microchannels with the aim of developing compact cooling systems which can be adapted to miniaturized power components. Nano and micro-surface treatments were used as innovative techniques to improve the heat transfer performance as well as to delay the intermittent dryout. It was observed that the micro-structured surfaces show significant enhancements (up to 85%) in heat transfer compared to the smooth surfaces. Especially, using the highly-wetted structured surface, the intermittent dryout is improved.

International audience; Recent research has confirmed a buildup of a thin layer of nanoparticles on the heated surface during nucleate boiling in nanofluids. Most of these studies report no change of heat transfer and, even worse, the presence of heat transfer deterioration. However, a few others report a heat transfer enhancement. In order to understand these controversial results, experiments were performed to explore the mechanism of surface coating during nucleate boiling in nanofluids. The thickness of the nanoparticle layer was observed to depend on the nanoparticles concentration and the experiment duration. Compared to a clean surface, the wettability of the surfaces with a TiO2 nanoparticle layer has been significantly improved. However, up to 50% of heat transfer coefficient deterioration was observed with TiO2-coated surfaces in water pool boiling. An explanation is proposed that involves the role of adhesion energy on heat transfer.

International audience; Over the past eighty years, bubble release during heterogeneous boiling has been the subject of numerous investigations. However, current understanding of factors that influence this process is still incomplete. In this paper, a model is developed to describe the effect of contact angle on the bubble departure from an upward-facing horizontal surface. Based on the concept of macro- and micro-contact angles, this model gives an explicit theoretical relation between the bubble departure diameter and the contact angle. Agreement with previous experimental data confirms the predictive ability of the present model.

Experiments were performed to study the effects of surface wettability on flow boiling of water at atmospheric pressure. The test channel is a single rectangular channel 0.5 mm high, 5 mm wide and 180 mm long. The mass flux was set at 100 kg/m2 s and the base heat flux varied from 30 to 80 kW/m2. Water enters the test channel under subcooled conditions. The samples are silicone oxide (SiOx), titanium (Ti), diamond-like carbon (DLC) and carbon-doped silicon oxide (SiOC) surfaces with static contact angles of 26{\deg}, 49{\deg}, 63{\deg} and 103{\deg}, respectively. The results show significant impacts of surface wettability on heat transfer coefficient., Comment: Papers in ICNMM10 conference, Montreal, Canada

International audience; Experiments were performed to highlight the influence of surface wettability on nucleate boiling heat transfer. Nanocoating techniques were used to vary the water contact angle from 20° to 110° by modifying nanoscale surface topography and chemistry. The bubble growth was recorded by a high speed video camera to enable a better understanding of the surface wettability effects on nucleation mechanism. For hydrophilic (wetted) surfaces, it was found that a greater surface wettability increases the vapour bubble departure radius and reduces the bubble emission frequency. Moreover, lower superheat is required for the initial growth of bubbles on hydrophobic (unwetted) surfaces. However, the bubble in contact with the hydrophobic surface cannot detach from the wall and have a curvature radius increasing with time. At higher heat flux, the bubble spreads over the surface and coalesces with bubbles formed at other sites, causing a large area of the surface to become vapour blanketed. The best heat transfer coefficient is obtained with the surface which had a water contact angle close to either 0° or 90°. A new approach of nucleation mechanism is established to clarify the nexus between the surface wettability and the nucleate boiling heat transfer.

International audience; Although boiling process has been a major subject of research for several decades, its physics still remain unclear and require further investigation. This study aims at highlighting the effects of surface wettability on pool boiling heat transfer. Nanocoating techniques were used to vary the water contact angle from 20 to 110 ◦ by modifying nanoscale surface topography and chemistry. The experimental results obtained disagree with the predictions of the classical models. A new approach of nucleation mechanism is established to clarify the nexus between the surface wettability and the nucleate boiling heat transfer. In this approach, we introduce the concept of macro- and micro- contact angles to explain the observed phenomenon

Although boiling process has been a major subject of research for several decades, its physics still remain unclear and require further investigation. This study aims at highlighting the effects of the surface wettability on pool boiling heat transfer. Nanocoating techniques were used to vary the water contact angle from 20 to 110° by modifying nanoscale surface topography and chemistry. The experimental results obtained disagree with the predictions of the classical models. A new approach of nucleation mechanism is established to clarify the nexus between the surface wettability and the nucleate boiling heat transfer. In this approach, we introduce the concept of macro- and micro-contact angles to explain the observed phenomenon.