Numerical study of using different Organic Rankine cycle working fluids for engine coolant energy recovery

Engine waste heat recovery technology especially Organic Rankine cycle (ORC) has been widely studied in order to achieve higher overall thermal efficiency, reduce the engine emissions and improve the fuel economy. The coolant energy occupies around 30% of the fuel energy can be used as the heat source for ORC system. This paper studies thermal status of the engine heated components when using different ORC working fluids as engine coolant to avoid the heat loos using heat exchanger to transfer coolant to the ORC fluid. A Solid-Liquid Conjugated Heat Transfer (SLCHT) calculation method is developed to calculate the heat transfer inside the engine, which can solve the temperature field of both solid zone and fluid zone. The simulation results have been validated by the experimental data from a 6-cylinder medium duty diesel engine, when water is the coolant in the system. The simulation model is then used to predict the temperature profile using different ORC working fluids and investigate the influence of different ORC working fluids on the cooling effects of the engine heated parts. The maximum temperature of the heated components has been selected as the evaluation parameters. The results reveals that applying selected ORC working fluids in engine as coolant is not practical under the designed conditions, which will make the engine overheated. Further investigation showed that increasing mass flow rate of the coolant can decrease the thermal status of the heated components but still cannot meet the cooling demands even under 200% of the original mass flow rate. The variations of the coolant outlet temperature and exergy were also analysed

Urbanization increased river nitrogen export to western Taiwan Strait despite increased retention by nitrification and denitrification

Abstract(#br)Urban development and increased human activities impose major environmental stress on the receiving bodies of water. Although urban rivers have been recognized as hotspots of regional nitrogen (N) pollution, detailed measurements of river nutrient species in response to urbanization are rarely reported, so the impacts of urban development on N cycling processes and transport to coast remains unclear. Here we investigated the changes in N species (concentration, composition and isotope) and N functional genes between upstream and downstream sections of several rivers affected by urban development in western Taiwan Strait under various flow conditions (low, medium and high flow). Our results suggest that urban sewage (high ammonium) is the predominant substrate that stimulated nitrification and subsequently denitrification and gaseous N removal (N 2 O, N 2 ). Nitrifying and denitrifying functional genes increased their abundance along the urban rivers. There were hydrological and meteorological controls on urban rivers regulating changes in nitrogen retention between seasons. Overall, the enhanced microbe-driven N retention could not balance the increase of urban N loading. Consequently, urbanization increased riverine N export and caused other changes in nutrient supply such as changing the nutrient ratio (N:P:Si ratio), increasing the potential for eutrophication both in the river and in receiving coastal ecosystems

Comparison study of trilateral Rankine cycle, organic flash cycle and basic organic Rankine cycle for low grade heat recovery

Organic Rankine Cycle (ORC) has been widely used for the recovery of low-grade heat into power such as solar energy and industrial waste heat. The overall thermal efficiency of ORC is affected by large exergy destruction in the evaporator due to the temperature mismatching between the heat source and working fluid. Trilateral Cycle (TLC) and Organic Flash Cycle (OFC) have been recognized as potential solutions because of their better performance on temperature matching between the heat source and working fluid at the evaporator. In this study, thermodynamic models of above three cycles are established in MATLAB/REFPROP. Results indicate that TLC obtains the largest net power output, thermal efficiency and exergy efficiency of 13.6 kW, 14.8% and 40.8% respectively at the evaporation temperature of 152℃, which is 37% higher than that of BORC (9.9 kW) and 58% higher than that of OFC (8.6 kW). BORC is more suitable under the conditions low evaporation temperature is relatively low due to the achieved maximum net power output, thermal efficiency and exergy efficiency. OFC has the minimum net power output, thermal efficiency and exergy efficiency under all the conditions of evaporation temperature compared to TLC and BORC. As for the UA value, TLC has the largest one ranging from 7.9 kW/℃ to 8.8 kW/℃ under all conditions while OFC gains the minimum UA value at low evaporation temperature and BORC gains the minimum UA value at high evaporation temperature

Study on the thermal interaction and heat dissipation of cylindrical Lithium-Ion battery cells

Cylindrical Lithium-Ion Batteries have been widely used as power source for electric and hybrid vehicles because of their compact size and high power density. The battery pack is commonly consisted by hundreds of cylindrical Lithium-Ion battery cells in several strings. Because the distance among battery cells is only a few millimeters, the thermal status of battery would directly influent the current efficiency and battery life. In order to maintain proper function of the battery pack, the heat dissipation around battery cells should be deeply investigated and well controlled. This question is undeniably important and which has gained increasing attentions. Researchers have developed some models of the transient temperature distribution in Lithium-Ion battery during the discharge cycle and the thermal management on various kinds of battery packs has been studied. However, because of the compacted and complicated structure inside battery pack, the full thermal status and detail distributions are difficult to be revealed in the same time. In this work, three-dimensional simulation methods have been used to solve the above questions on the combination of several cylindrical Lithium-Ion battery cells. Existing heat generation models in Lithium-Ion battery is defined as the thermal boundary conditions. The flow and convection on the spacing has been studied. The transient thermal interactions and convections among adjacent battery cells have been investigated to explore the influences by spacing and transient heat release rules. The achieved results can be used as critical reference for designing the structures of battery pack and planning the cooling strategies

Smad7 enables STAT3 activation and promotes pluripotency independent of TGF-β signaling

TGF-β and related growth factors critically regulate cell potency and functions. Smad7 is induced by TGF-βs and inhibits the physiological functions of TGF-β signaling. This study describes an unexpected finding that Smad7 promotes self-renewal of embryonic stem cells (ESCs) in a manner independent of its inhibition on TGF-β signaling. Instead, Smad7 acts to induce activation of transcription factor signal transducers and activators of transcription 3 (STAT3) in ESCs. Smad7 activates STAT3 through its direct binding to the cytokine receptor upstream of STAT3 activation. In agreement with the role of STAT3 in maintaining ESC pluripotency, Smad7 promotes ESC self-renewal and induced pluripotent stem cell reprogramming. This finding illustrates a regulatory mechanism for Smad7 in maintaining pluripotency, and likely in cancer and inflammation

Single-shot time-gated fluorescence lifetime imaging using three-frame images

Qualitative and quantitative measurements of complex flows demand for fast single-shot fluorescence lifetime imaging (FLI) technology with high precision. A method, single-shot time-gated fluorescence lifetime imaging using three-frame images (TFI-TGFLI), is presented. To our knowledge, it is the first work to combine a three-gate rapid lifetime determination (RLD) scheme and a four-channel framing camera to achieve this goal. Different from previously proposed two-gate RLD schemes, TFI-TGFLI can provide a wider lifetime range 0.6 ~ 13ns with reasonable precision. The performances of the proposed approach have been examined by both Monte-Carlo simulations and toluene seeded gas mixing jet diagnosis experiments. The measured average lifetimes of the whole excited areas agree well with the results obtained by the streak camera, and they are 7.6ns (N2 = 7L/min; O2 < 0.1L/min) and 2.6ns (N2 = 19L/min; O2 = 1L/min) with the standard deviations of 1.7ns and 0.8ns among the lifetime image pixels, respectively. The concentration distributions of the quenchers and fluorescent species were further analyzed, and they are consistent with the experimental settings

Ppm1b negatively regulates necroptosis through dephosphorylating ​Rip3

该研究论文发现蛋白磷酸酶Ppm1b 通过去磷酸化RIP3负调控程序性细胞坏死（necroptosis），阐明了RIP3磷酸化状态的精确调控对于细胞和机体在生理和病理状态下的存活至关重要。The auto-phosphorylation of murine ​receptor-interacting protein 3 (​Rip3) on Thr 231 and Ser 232 in the necrosome is required to trigger necroptosis. However, how ​Rip3 phosphorylation is regulated is still largely unknown. Here we identified ​protein phosphatase 1B (​Ppm1b) as a ​Rip3 phosphatase and found that ​Ppm1b restricts necroptosis in two settings: spontaneous necroptosis caused by ​Rip3 auto-phosphorylation in resting cells, and ​tumour necrosis factor-α (​TNF)-induced necroptosis in cultured cells. We revealed that ​Ppm1b selectively suppresses necroptosis through the dephosphorylation of ​Rip3, which then prevents the recruitment of ​mixed lineage kinase domain-like protein (​Mlkl) to the necrosome. We further showed that ​Ppm1b deficiency (​Ppm1bd/d) in mice enhanced ​TNF-induced death in a ​Rip3-dependent manner, and the role of ​Ppm1b in inhibiting necroptosis was evidenced by elevated ​Rip3 phosphorylation and tissue damage in the caecum of ​TNF-treated ​Ppm1bd/d mice. These data indicate that ​Ppm1b negatively regulates necroptosis through dephosphorylating ​Rip3 in vitro and in vivo