bluuebunny/crossref_metadata_2025 huggingface dataset:
Dietary melatonin attenuates chromium-induced lung injuryviaactivating the Sirt1/Pgc-1α/Nrf2 pathway
Authors: Han Bing , Li Siyu , Lv Yueying , Yang Daqian , Li Jiayi , Yang Qingyue , Wu Pengfei , Lv Zhanjun , Zhang Zhigang
Published: August 2019

Exposure to chromium (Cr) causes a number of respiratory diseases, including lung cancer and pulmonary fibrosis.
How to assess the potential of emerging green technologies? Towards a prospective environmental and techno-economic assessment framework
Authors: Thomassen Gwenny , Van Dael Miet , Van Passel Steven , You Fengqi
Published: August 2019

The prospective environmental techno-economic assessment framework is proposed, gathering best practices to assess the potential of emerging green chemical technologies.
Integrated microfluidic pumps and valves operated by finger actuation
Authors: Park Juhwan , Park Je-Kyun
Published: August 2019

Integrated microfluidic pumps and valves for fluid delivery and determination of flow paths are operated simultaneously by pushing a button.
Pumpless microfluidic devices for generating healthy and diseased endothelia
Authors: Yang Yang , Fathi Parinaz , Holland Glenn , Pan Dipanjan , Wang Nam Sun , Esch Mandy B.
Published: August 2019

We have developed a pumpless cell culture chip that can recirculate small amounts of cell culture medium (400 μL) in a unidirectional or bidirectional flow pattern, producing physiologic levels of shear suitable for culturing endothelial cells.
Functional characterization of copper transporters zCtr1, zAtox1, zAtp7a and zAtp7b in zebrafish liver cell line ZFL
Authors: Kwok Man Long , Chan King Ming
Published: August 2019

Copper (Cu) is an essential element for all organisms, serving as an enzyme cofactor to maintain cellular activity and vitality. However, Cu homeostasis must be maintained at the physiological and cellular levels as Cu ions can be highly toxic. In mammals, ATP7A is expressed in most tissues, but relatively lower expression is found in the liver, and is responsible for the intestinal uptake of Cu, while ATP7B is highly expressed in the liver, kidneys and placenta, and is responsible for removal of Cu in the liver. CTR1 and ATOX1 are responsible for cellular Cu uptake and intracellular Cu transport, respectively. Here, using a zebrafish liver cell line (ZFL), we studied the cellular functions of four zebrafish Cu transporters. In zebrafish, zAtp7a is expressed mainly in the liver and zAtp7b is expressed mainly in the intestines, different from that of humans which have a high ATP7b level in the liver and high ATP7a level in the intestines. We here found that zctr1 or zatox1 overexpression increased Cu accumulation in ZFL cells. Moreover, zctr1 overexpression made ZFL cells more sensitive to Cu and Zn exposure, and overexpression of zatox1 or zatp7b increased Cu uptake and Cu tolerance in ZFL cells. Overexpression of zatp7a made ZFL cells more sensitive to Zn. Taken together, our findings suggest that zatp7b is responsible for Cu export despite its expression level being much lower than zatp7a in ZFL cells.
Fabrication of nanostructured NiO/WO3with graphitic carbon nitride for visible light driven photocatalytic hydroxylation of benzene and metronidazole degradation
Authors: Devi Meghali , Das Bishal , Barbhuiya Monjur Hassan , Bhuyan Bishal , Dhar Siddhartha Sankar , Vadivel Sethumathavan
Published: August 2019

Fabrication of a novel NiO/WO3nanohybrid modified graphitic carbon nitride nanosheets with enhanced photocatalytic activity towards photocatalytic hydroxylation of benzene and degradation of a pharmaceutical waste metronidazole.
Environmentally friendly covalent coupling of proteins onto oxidized cellulosic materials
Authors: Haske-Cornelius Oskar , Weinberger Simone , Quartinello Felice , Tallian Claudia , Brunner Florian , Pellis Alessandro , Guebitz Georg M.
Published: August 2019

Cellulose is a biodegradable and renewable material that is one of the most abundant biopolymers with many different applications from low value newsprint products to high value biomedical sensor devices.
Outstanding heat loss via nano-octahedra above 20 nm in size: from wustite-rich nanoparticles to magnetite single-crystals
Authors: Castellanos-Rubio Idoia , Rodrigo Irati , Munshi Rahul , Arriortua Oihane , Garitaonandia José S. , Martinez-Amesti Ana , Plazaola Fernando , Orue Iñaki , Pralle Arnd , Insausti Maite
Published: August 2019

Novel octahedral single-crystals of magnetite with non-fluctuating magnetic moments exhibit outstanding heat loss, both in physiological media and when immobilized in agar.
Distortion of mannoimidazole supports a B2,5 boat transition state for the family GH125 α-1,6-mannosidase from Clostridium perfringens
Authors: Males Alexandra , Speciale Gaetano , Williams Spencer J. , Davies Gideon J.
Published: August 2019

Enzyme transition-state mimics can act as powerful inhibitors and allow structural studies that report on the conformation of the transition-state.
Electrochemical synthesis of Au@semiconductor core–shell nanocrystals guided by single particle plasmonic imaging
Authors: Wang Hui , Zhao Wei , Xu Cong-Hui , Chen Hong-Yuan , Xu Jing-Juan
Published: August 2019

Plasmonic photocatalysts with a core–shell heterostructure were synthesized via electrochemical deposition guided by single particle plasmonic imaging.
Alkynylation of radicals: spotlight on the “Third Way” to transfer triple bonds
Authors: Le Vaillant Franck , Waser Jérôme
Published: August 2019

This review explores the alkynylation of radicals as approach for the flexible and efficient synthesis of alkynes.
Dramatic slowing down of the conformational equilibrium in the silyl derivative of glucose in the vicinity of the glass transition temperature
Authors: Wolnica K. , Dulski M. , Kamińska E. , Tarnacka M. , Wrzalik R. , Zięba A. , Kasprzycka A. , Nowak M. , Jurkiewicz K. , Szeja W. , Kamiński K. , Paluch M.
Published: August 2019

This paper reports significantly slowed down of the rotations of silyl moieties along with the deformation in the saccharide ring in 1,2,3,4,6-penta-O-(trimethylsilyl)-d-glucopyranose (S-GLU) in the vicinity of the glass transition temperature.
Structural and functional characterisation of human RNA helicase DHX8 provides insights into the mechanism of RNA-stimulated ADP release
Authors: Felisberto-Rodrigues Catarina , Thomas Jemima C. , McAndrew Craig , Le Bihan Yann-Vaï , Burke Rosemary , Workman Paul , van Montfort Rob L. M.
Published: August 2019

DHX8 is a crucial DEAH-box RNA helicase involved in splicing and required for the release of mature mRNA from the spliceosome. Here, we report the biochemical characterisation of full-length human DHX8 and the catalytically active helicase core DHX8Δ547, alongside crystal structures of DHX8Δ547 bound to ADP and a structure of DHX8Δ547 bound to poly(A)6 single-strand RNA. Our results reveal that DHX8 has an in vitro binding preference for adenine-rich RNA and that RNA binding triggers the release of ADP through significant conformational flexibility in the conserved DEAH-, P-loop and hook-turn motifs. We demonstrate the importance of R620 and both the hook-turn and hook-loop regions for DHX8 helicase activity and propose that the hook-turn acts as a gatekeeper to regulate the directional movement of the 3′ end of RNA through the RNA-binding channel. This study provides an in-depth understanding of the activity of DHX8 and contributes insights into the RNA-unwinding mechanisms of the DEAH-box helicase family.
Optical depth in polarised Monte Carlo radiative transfer
Authors: Baes Maarten , Peest Christian , Camps Peter , Siebenmorgen Ralf
Published: August 2019

Context. The Monte Carlo method is the most widely used method to solve radiative transfer problems in astronomy, especially in a fully general 3D geometry. A crucial concept in any Monte Carlo radiative transfer code is the random generation of the next interaction location. In polarised Monte Carlo radiative transfer with aligned non-spherical grains, the nature of dichroism complicates the concept of optical depth.

Aims. We investigate, in detail, the relation between optical depth and the optical properties and density of the attenuating medium in polarised Monte Carlo radiative transfer codes that take dichroic extinction into account.

Methods. Based on solutions for the radiative transfer equation, we discuss the optical depth scale in polarised radiative transfer with spheroidal grains. We compare the dichroic optical depth to the extinction and total optical depth scale.

Results. In a dichroic medium, the optical depth is not equal to the usual extinction optical depth, nor to the total optical depth. For representative values of the optical properties of dust grains, the dichroic optical depth can differ from the extinction or total optical depth by several tens of percent. A closed expression for the dichroic optical depth cannot be given, but it can be derived efficiently through an algorithm that is based on the analytical result corresponding to elongated grains with a uniform grain alignment.

Conclusions. Optical depth is more complex in dichroic media than in systems without dichroic attenuation, and this complexity needs to be considered when generating random free path lengths in Monte Carlo radiative transfer simulations. There is no benefit in using approximations instead of the dichroic optical depth.
Rapid classification of TESS planet candidates with convolutional neural networks
Authors: Osborn H. P. , Ansdell M. , Ioannou Y. , Sasdelli M. , Angerhausen D. , Caldwell D. , Jenkins J. M. , Räissi C. , Smith J. C.
Published: August 2019

Aims. Accurately and rapidly classifying exoplanet candidates from transit surveys is a goal of growing importance as the data rates from space-based survey missions increase. This is especially true for the NASA TESS mission which generates thousands of new candidates each month. Here we created the first deep-learning model capable of classifying TESS planet candidates.

Methods. We adapted an existing neural network model and then trained and tested this updated model on four sectors of high-fidelity, pixel-level TESS simulations data created using the Lilith simulator and processed using the full TESS pipeline. With the caveat that direct transfer of the model to real data will not perform as accurately, we also applied this model to four sectors of TESS candidates.

Results. We find our model performs very well on our simulated data, with 97% average precision and 92% accuracy on planets in the two-class model. This accuracy is also boosted by another ~4% if planets found at the wrong periods are included. We also performed three-class and four-class classification of planets, blended and target eclipsing binaries, and non-astrophysical false positives, which have slightly lower average precision and planet accuracies but are useful for follow-up decisions. When applied to real TESS data, 61% of threshold crossing events (TCEs) coincident with currently published TESS objects of interest are recovered as planets, 4% more are suggested to be eclipsing binaries, and we propose a further 200 TCEs as planet candidates.
A telescope-ready approach for modal compensation of pyramid wavefront sensor optical gain
Authors: Deo V. , Gendron É. , Rousset G. , Vidal F. , Sevin A. , Ferreira F. , Gratadour D. , Buey T.
Published: August 2019

The pyramid wavefront sensor (PWFS) is the currently preferred design for high-sensitivity adaptive optics (AO) systems for extremely large telescopes (ELTs). Yet, nonlinearities of the signal retrieved from the PWFS pose a significant problem for achieving the full correction potential using this sensor, a problem that will only worsen with the increasing dimension of telescopes. This paper investigates the so-called optical gain (OG) phenomenon, a sensitivity reduction and an overall modification of the sensor response induced by the residual wavefront itself, with considerable effects in standard observation conditions for ELT-sized AO systems. Through extensive numerical analysis, this work proposes a formalism to measure and minimize the first-order nonlinearity error caused by optical gain variation, which uses a modal compensation technique of the calibrated reconstructor; this enables a notable increase in performance in faint guide stars or important seeing scenarios, for example from 16 to 30% H-band Strehl ratio for a sixteenth magnitude star in r0 = 13 cm turbulence. Beyond the performance demonstrated by this compensation, a complete algorithm for realistic operation conditions is designed, which from dithering a few deformable mirror modes retrieves the optimal gains and updates the command matrix accordingly. The performance of this self-updating technique – which successfully allows automatic OG compensation regardless of the turbulent conditions, and its minimal interference with the scientific instrument are demonstrated through extensive end-to-end numerical simulations, all at the scale of an ELT instrument single-conjugate AO system.
Chlorine-bearing molecules in molecular absorbers at intermediate redshifts
Authors: Wallström S. H. J. , Muller S. , Roueff E. , Le Gal R. , Black J. H. , Gérin M.
Published: August 2019

We use observations of chlorine-bearing species in molecular absorbers at intermediate redshifts to investigate chemical properties and 35Cl/37Cl isotopic ratios in the absorbing sightlines. Chloronium (H2Cl+) is detected along three independent lines of sight in the z = 0.89 and z = 0.68 molecular absorbers located in front of the lensed quasars PKS 1830−211 and B 0218+357, respectively. Hydrogen chloride (HCl) was observed only toward PKS 1830−211, and is found to behave differently from H2Cl+. It is detected in one line of sight with an abundance ratio [H2Cl+] / [HCl] ∼1, but remains undetected in the other, more diffuse, line of sight, with a ratio [H2Cl+] / [HCl] > 17. The absorption profiles of these two chlorine-bearing species are compared to other species and discussed in terms of the physical properties of the absorbing gas. Our findings are consistent with the picture emerging from chemical models where different species trace gas with different molecular hydrogen fraction. The 35Cl/37Cl isotopic ratios are measured in the different lines of sight and are discussed in terms of stellar nucleosynthesis.
A numerical model and validation of phase change material integrated thermoelectric radiant cooling panel
Authors: Lim Hansol , Cho Hye-Jin , Cheon Seong-Yong , Lee Soo-Jin , Jeong Jae-Weon
Published: August 2019

A phase change material based radiant cooling panel with thermoelectric module (PCM-TERCP) is proposed in this study. It consists of two aluminium panels, and phase change materials (PCMs) sandwiched between the two panels. Thermoelectric modules (TEMs) are attached to one of the aluminium panels, and heat sinks are attached to the top side of TEMs. PCM-TERCP is a thermal energy storage concept equipment, in which TEMs freeze the PCM during the night whose melting temperature is 16○C. Therefore, the radiant cooling panel can maintain a surface temperature of 16◦C without the operation of TEM during the day. Furthermore, it is necessary to design the PCM-TERCP in a way that it can maintain the panel surface temperature during the targeted operating time. Therefore, the numerical model was developed using finite difference method to evaluate the thermal behaviour of PCM-TERCP. Experiments were also conducted to validate the performance of the developed model. Using the developed model, the possible operation time was investigated to determine the overall heat transfer coefficient required between radiant cooling panel and TEM. Consequently, the results showed that a overall heat transfer coefficient of 394 W/m2K is required to maintain the surface temperature between 16○C to 18○C for a 3 hours operation.
Combinations of heat pump and photovoltaics for renovated buildings
Authors: Heinz Andreas , Gaber Christian
Published: August 2019

The aim of this work is the analysis of hybrid heating systems consisting of an air source heat pump, a storage tank and a photovoltaic (PV) system for the use in renovated residential buildings. The potential for decreasing the electrical energy consumption of the heat pump from the grid by targeted operation of the speed controlled compressor with electricity from PV is determined by means of dynamic system simulations in TRNSYS for a renovated single family house under the assumption that the existing radiator heating system is not replaced, and that therefore relatively high supply temperatures are necessary. Different variants were considered with regard to the size of the PV system, the storage volume and the influence of the heat emission system.
Solar-ice systems for multi-family buildings: hydraulics and weather data analysis
Authors: Carbonell Daniel , Schmidli Jeremias , Philippen Daniel , Haller Michel
Published: August 2019

Dynamic simulations using the TRNSYS environment were used to assess the potentials of solar-ice systems for multi-family buildings in Switzerland. The goals of this paper were: i) to analyze and quantify the effects of different hydraulics in the primary loop (solar collectors, ice storage and heat pump), ii) to determine the energetic performance of solar-ice systems for multi-family buildings and iii) to assess the influence of the chosen weather data on the system performance. Simulations were carried out for a range of collector areas of 1.5 m2/MWh to 2.5 m2/MWh and for ice storage volumes of 0.4 m3/MWh to 0.6 m3/MWh being MWh the total yearly heat demand.

An averaged increase of the ΔSPF of 26% was obtained by using direct solar heat in the warm storage. Adding the possibility to use solar heat for heat pump evaporator, increased the SPFSHP+ by 31 %. Simulations of eight cities in Switzerland using cold, warm and normal weather data sets from SIA were carried out. Results for Davos and Locarno achieved the best results with averaged SPFSHP+ of 7.4 and 6.3 respectively. Simulations for the rest of the cities achieved averaged SPFSHP+ in the range of 3.8 to 4.5. The use a cold weather data respect to the normal one defined by the SIA standard led to an average decrease of the SPFSHP+ of 25 %. The use of a warm weather data led to an increase of the SPFSHP+ of 5 %.
A Field Survey on Indoor Air Pollution in School Classrooms with Different Ventilation Methods
Authors: Murakami Ko , Sakai Kenta , Nakamura Daisuke , Ishikawa Haruno , Tsushima Sayana , Tanabe Shin-ichi
Published: August 2019

The purpose of this study was to investigate the actual indoor air quality within two elementary schools with different types of ventilation methods, and to obtain data pertaining to the emission of bioeffluents within the schools. Field surveys on indoor air quality were conducted at two public elementary schools in Tokyo, both equipped with air-conditioning systems. School-A was also equipped with a heat-exchange ventilation system, while School-B did not have a ventilation system. Results of the study revealed that the target ventilation volume for the heat-exchange ventilation system in School-A was not achieved, indoor air quality in School-B was better in relatively cool conditions than School-A because of the habit of opening windows attached, there was a positive correlation between nonanal and decanal and CO2 concentration in summer, and the concentration of bioeffluents nonanal and decanal may be higher at high temperatures even under the same level of ventilation.
Optimization on segmentation spraying for cooling a moving source at high temperature in a confined space
Authors: Zhi Chengqiang , Ye Wei , Zhang Qianru , Huang Yixiang , Zhang Xu
Published: August 2019

Heavy trucks, train carriages, and other moving vehicles with heating sources, are often loaded into a confined space for parking and maintenance. When the heating source from the vehicle is at high temperature, spray cooling using nozzles can be applied for at least two purposes. First, to further decrease the temperature of the surrounding areas. Second, to flush the surfaces of the vehicle as a primary cleansing method. To reduce water consumption, the number and positions of the running nozzles along the way need to be adjusted and optimized according to the position of the moving vehicle. To achieve that, the optimization of a segmented control method for the nozzles is discussed using both theoretical and computational fluid dynamics (CFD) methods in this paper. 120 ~ 240 nozzles in total were uniformly and linearly distributed on the ceiling of a 120m-long narrow space. The space between two adjacent nozzles are set at 0.5m, 0.7m and 1.0m, respectively. All the nozzles are divided into one to ten groups for segmentation control. One 35m-long vehicle with a heating source at over 800 K was moving at 0.05 m/s to 0.20 m/s. The results showed that, first, for one spraying group, at least 39 running nozzles were needed to minimize the areas of interior structure at temperature > 350K. Second, the water consumption can be reduced dramatically by increasing the number of groups. However, when dividing into more than six groups, the capacity of water saving is no longer significant. Third, when the vehicle is entering, multiple- group of running nozzles are needed to overcome the sudden heating source at high temperature.
Ventilation Performance Improvement in a Container with an Extraction Free Cooling System
Authors: Gülseven Cem , Yılmazoğlu M. Zeki
Published: August 2019

In this study, a far-off local zone telecommunication infrastructure container ventilation system with cabinets is modelled. CFD analysis is performed to obtain the temperature and velocity profile inside the container with given heat loads and volume flow rates provided by fans. In the second part of the study, performance improvement scenarios are simulated. Hot regions are found at the back sides of the cabinets and vortices are formed in the middle plane zone of the volume which reduces the air intake of the fans in corresponding cabinets inside the container. To overcome this issue, a flow director, i.e. vortex breaker is designed to redirect to enhance fan suction, and the orientation of the cabinets have rearranged. According to the results, it is possible to improve the ventilation performance of a container with such an approach. In this study, %2.0735 of improvement is achieved by changing the location of the cabinets and placing a vortex breaker inside the room, where it is a significant change for such far-off local zone telecom applications, considering the extreme environmental conditions.
Simulations on arrangements of induced jet-fans as auxiliary ventilation for a mechanical ventilated space with openings
Authors: Zhao Wenxuan , Ye Wei , Zhang Qianru , Zhang Xu
Published: August 2019

Underground garages, indoor stadiums, or more commonly used seagoing ships, can be used as large multi-purpose spaces, which are suitable for the carriage of a wide range of cargoes, as well as evacuation of people at overseas. The indoor environment in a multi-purpose cabin usually varies, in terms of pollutant emissions, hazardous levels and the corresponding ventilation requirements. A possible solution, in addition to a single regular HVAC system, is to use multiple induced jet fans. However, to pre-determine a universal design of fans, e.g., numbers, locations, directions, angles and flowrates, etc., may not be practical. In this preliminary work, methods to design the auxiliary ventilation system were discussed. The heat sources are located in the four corners on the floor. CFD method is used to further study the effects of six regular and four irregular arrangements of a 2×2 array of fans on local heat dilution with or without natural ventilation (e.g., additional openings in the space). Heat exhaust efficiency is used to evaluate the effects of different arrangements of fans on local heat dilution. The results show that adjustable ventilation using induced fans would be useful to provide various airflow distribution for a large space and the dilution of the heat can be improved and the areas of high temperature inside the space can be reduced. Furthermore, the heat exhaust efficiency would be higher and the induced fans have a more significant effect, especially when additional natural ventilation is available.
Relation between energy use and indoor thermal environment in animal husbandry: a case study
Authors: Bilardo Matteo , Comba Lorenzo , Cornale Paolo , Costantino Andrea , Fabrizio Enrico
Published: August 2019

Climate control is of the foremost importance in structures for intensive animal rearing because many animals (e.g. pigs and broilers) tolerate a small range of climate conditions (mainly air temperature and relative humidity) that may differ considerably from the outdoor environment. For this reason, the indoor climate in the majority of structures for animal husbandry is guaranteed by HVAC systems. On the one hand, the use of mechanical systems makes it possible to avoid production risks due to the unpredictability of the outdoor weather conditions and to maximize the feed efficiency, with positive effects on both the animal welfare and farm profit. On the other hand, the use of HVAC entails not negligible thermal and electrical energy consumptions. In literature, few data about the real thermo-hygrometric conditions and energy consumption of animal houses are present. In this work (in the framework of the EPAnHaus – Energy Performance certification of Animal Houses –project), the results obtained from a long-term monitoring campaign in two growing-finishing pig houses are presented. The performed measurements concerned environmental parameters and electrical power that were acquired during two production cycles (warm and cool seasons). For the environmental monitoring, both the buildings were equipped with temperature and relative humidity sensors embedded in portable data loggers (10 minutes logging time) that were placed in various spots inside the houses. Outdoor data were obtained through a weather station located near the test site. Concerning the energy monitoring, power transducers connected to portable data loggers (10 seconds logging time) were placed in the electric panel of each house to log the electrical energy consumptions due to ventilation, lighting and automatic feeding. The acquired data were used for carrying out analysis concerning the indoor thermal environment, its characterization in relation with the animal welfare, the electrical energy uses and the existing relations between all these aspects. The obtained data were used to evaluate the effectiveness of the HVAC system in guaranteeing the adequate indoor climate conditions (avoiding heat/cold stress conditions) and to identify electrical energy uses.
Investigation of energetic and exergetic performances of parabolic trough collector with using different heat transfer fluids
Authors: Arslan F. Mertkan , Günerhan Hüseyin
Published: August 2019

In this study energetic and exergetic performances of parabolic trough collector is theoretically investigated by using 120 l/min synthetic ‘’Dowtherm A’’ oil , 1200 l/min Air at 100 bar (10 MPa) and 150 l/min molten salt which is mixture of 60 wt% sodium nitrate (NaNO3) and 40 wt% potassium nitrate (KNO3) which are widely used as heat transfer fluids. Fluids performance comparisons were performed with the LS-2 module, which is used with vacuum in annulus and Cermet as a selective coating. LS-2 module has 7.8 m receiver length and is 39 m2 aperture area. As a result, the maximum exergy efficiency of the molten salt, synthetic oil, Air to be 41.19% at 422 °C, 40.82% at 400 °C, 40.33% at 402 °C, respectively. The maximum exergy of air is higher than other working fluids up to 310 ° C but after about 310 ° C the exergy of the molten salt is higher than the others. The molten salt has the best energy efficiency at its operating temperatures (250 °C to 550 °C) than other working fluids.
Carbon-based Nanofluid Applications in Solar Thermal Energy
Authors: Çobanoğlu Nur , Karadeniz Ziya Haktan , Turgut Alpaslan
Published: August 2019

Renewable energy sources such as solar, wind and geothermal are proposed as an alternative to fossil fuels whose excessive use causes global warming. The most popular one of the renewable energy sources is considered as solar energy due to the fact that required energy is provided by the sun entire year around the world. Solar energy systems convert the solar radiation to the useful heat or electricity. In order to achieve better performance in solar thermal systems many studies have been conducted. Some of these studies suggest that heat transfer fluid could be changed with the nanofluids which can be defined as new generation heat transfer fluid. Nanofluids are suspensions of nano-sized particles such as metals, metal-oxides, and Carbon-allotropes (C), in the conventional base-fluids (water, ethylene glycol and oil). Using nanofluid enhances the efficiency and thermal performance of solar systems due to their better thermophysical and optical properties. Recently, C-based nanofluids are getting attention due to their enhanced thermal conductivity and absorptivity at even low concentrations. The results show that C-based nanofluids have a potential to use in solar energy systems: solar collectors, solar stills, photovoltaic/thermal systems.
Contributions to System Integration of PV and PVT Collectors with Heat Pumps in Buildings
Authors: Koch Manuel , Dott Ralf
Published: August 2019

A common approach to improve self-consumption of photovoltaic (PV) generation in buildings with heat pumps (HP) is to overload the thermal storage capacities during times with surplus PV generation (hereinafter referred to as thermal overloading). The impact of battery capacity and domestic hot water (DHW) consumption on the effectiveness of this method in a single-family home (SFH) is evaluated through numerical simulations. Increased battery capacity is shown to decrease the effectiveness of thermal overloading. Regarding DHW consumption, temporal concentration is shown to have a stronger influence on the effectiveness of thermal overloading than total energy. Furthermore, the potential of photovoltaic-thermal collectors (PVT) as heat exchangers for air/brine/water heat pumps (ABWHP) is estimated. The results show that the properties of PVT collectors with high thermal conductivity are in the feasible range for application in a well-insulated SFH in Central European climate.
Using the Hardware-in-the-Loop concept for energetic evaluation of heat generators
Authors: Knorr Martin , Seifert Joachim , Schinke Lars , Beyer Maximilian , Mehrfeld Philipp , Nürenberg Markus
Published: August 2019

Currently available energetic evaluation methods for heat pump and micro-CHP systems lead to results which partly deviate strongly from field measurements. A new evaluation method based on the Hardware-in-the-Loop concept was therefore developed and tested in a research project. The method employs representative days. A procedure for determining the representative days is presented. The functionality of the concept could be proven in a round robin test and the energetic key figures can be confirmed by values from field measurements values.
Energy assessment of hybrid heat pump systems as a retrofit measure in residential housing stock
Authors: Keogh David , Saffari Mohammad , de Rosa Mattia , Finn Donal P.
Published: August 2019

Hybrid electric-gas heat pump systems are a possible retrofit option in older residential buildings. Older buildings can be challenging to retrofit and in this context hybrid systems can offer an intermediate route to decarbonisation of building heating energy demand. This is especially the case, where deep retrofit measures coupled with monovalent electric heat pump systems may not be feasible from an economic perspective. The aim of the current paper is to examine the suitability of a hybrid electric-gas heat pump system in comparison to electric heat pump systems as a retrofit measure for Irish housing stock and to benchmark both options against existing fossil fuel baseline systems. A detailed building energy model of a residential dwelling was developed and calibrated to within acceptable ASHRAE standards. An energy assessment was carried out which investigates each retrofit scenario. Key findings include: (i) both the all-electric and hybrid heat pump systems deliver primary energy savings compared to the fossil fuel baseline systems, (ii) hybrid systems attain higher primary energy savings compared to all-electric heat pump, where the hybrid system incorporates flexible delivery temperatures compared to a fixed delivery temperature tor the all-electric heat pump system.
A laboratory apparatus to study Thermal Response Test in the presence of groundwater flow
Authors: Angelotti Adriana , Molinaroli Luca
Published: August 2019

The standard approach to Thermal Response Test, based on conduction heat transfer in the ground, turns out to be unsuccessful under significant groundwater flow. The applicability of the Moving Infinite Line Source model to interpret the TRT in this case still needs to be proved. In order to study the TRT in the presence of a groundwater flow, an original laboratory apparatus has been developed. The Sand Box design is based on a heat transfer similitude between the real scale TRT problem and the laboratory scale one. The Sand Box sizes (1,2 m x 0.6 m x 1.0 m) are then set in order to keep the boundaries unaffected by the heat source during the TRT. The U-pipe heat exchanger is reproduced through a twocables electrical resistance 1 m long. A hydraulic loop with a peristaltic pump allows to obtain a Darcy velocity across the sandy soil up to 6,7510-5m/s. The measurement system consists in several thermocouples in the porous medium and in a flow meter. The TRT results at null groundwater velocity allow to derive a reference thermal conductivity. The first tests with groundwater flow show the suitability of the apparatus and allow to derive some preliminary considerations.
Validation of black-box performance models for a water-to-water heat pump operating under steady state and dynamic loads
Authors: Fuentes Elena , Salom Jaume
Published: August 2019

The use of simple mathematical models for describing the behaviour of heat pumps is important for assessing the energy performance of this equipment when installed in buildings. However, because of their simplicity, commonly used simple models, may not be able to fully account for the dynamic performance of heat pumps during transient phases. In this study, different performance black box models for an on-off water-to-water heat pump are validated by comparison with laboratory experimental results at steady state and dynamic cycling conditions. The models range from the solution based on the interpolation on the heat pump performance map to the detailed dynamic solution that combines correlations for the quasi-steady state operation and activation functions to model the transient phases. The output temperatures, electrical and thermal power and coefficient of performance from simulations were compared with experimental data from a water-to-water heat pump of 40.5 kW nominal heating capacity operating under cycling conditions. After validation with experiments, annual energy performance simulations of a tertiary building provided with a heat pump were conducted. These simulations quantifying the uncertainty expected when using heat pump performance models in simulation environments for estimating their annual energy performance.
Experimental performance analysis of a multiple-source and multiple-use heat pump system: winter field experiment and heating operation performance evaluation
Authors: Liu Mingzhe , Ooka Ryozo , Hino Toshiyuki , Wen Ke , Choi Wonjun , Lee Doyun , Ikeda Shintaro , Reza Palasz Djafar
Published: August 2019

We herein report the development of a distributed heat pump system that can utilize a variety of renewable energy sources to meet different building heating and cooling demands (i.e., a multiple source and multiple use heat pump system, MMHP). In this system, a water circulating loop is used to connect ground heat exchangers, a unique sky-source heat pump, and various heat pumps for heating and cooling purposes to form a thermal network within a building. This distribution increases the flexibility of the system and allows an improved matching of supply and demand. To evaluate the system performance, an experimental house was constructed, and a winter field experiment was conducted. We found that the reported heat pump for floor heating achieved a stable operation with a high coefficient of performance of ~11.5, while the heat collecting operation performance of the sky-source heat pump varied significantly depending on the amount of solar radiation and the outside air temperature. Finally, since the sky-source heat pump contributes to an improvement in the whole system performance, it appears that there is still room for improved regarding the whole system performance by adjusting the operating and control strategy.
Evaluation of Thermal Behavior of the Skeleton in a Green Building with the Aid of TABS
Authors: Muramatsu Hiroshi , Nobe Tatsuo
Published: August 2019

In this study, an office building in Japan that incorporates energy-saving features and environmental technologies was investigated. This office building features a green façade, natural ventilation, a concrete slab with no suspended ceilings, and thermo-active building systems. Two airconditioning systems were installed in this building—a ceiling radiation air-conditioning system and a whole floor-blow off air conditioning system. In addition, a natural ventilation system was installed. We surveyed the heat flux of the ceiling surface and indoor thermal environment of this building from 2015 through 2016. The ceiling using the heat storage amount of concrete maintains a constant temperature in the workplace during as well as after office hours. We also performed detailed measurements of the heat flux of the ceiling surface and indoor thermal environment in the summer of 2017. The results showed that the ceiling radiation air-conditioning system provided a stable thermal environment. Furthermore, we report that making use of the thermal behavior of the skeleton improved the operation of the ceiling radiation airconditioning system.
Improved thermal energy storage for heating and cooling of buildings
Authors: Koželj Rok , Ahčin Žiga , Zavrl Eva , Stritih Uroš
Published: August 2019

One of the great challenges in the energy sector represents retrofit of residential buildings where 3/4 of buildings in Europe are residential. To reduce energy consumption and increase the use of renewables in existing residential buildings a holistic approach of retrofit with interconnected technological system is needed. In the present paper energy toolkit based on the synergetic interaction between technologies integrated in the system for holistic retrofit of residential buildings which is under development within HEART project (HORIZON 2020) is presented. In this project step towards self-sufficient heating and cooling of building is made with an increase in on-site consumption of self-produced energy in PV from solar energy, where produced electrical energy is used also for heat pump operation. In this case thermal energy storage plays an important role for storing heat or cold for time when solar energy is not available. Improvement of sensible thermal energy storage with implemented cylindrical modules at the top of the heat storage tank and filled with phase change material is investigated experimentally. 43 litres of paraffin with phase change temperature between 27 °C and 29 °C was used in a system, what represented 15 % of total volume of heat storage tank. The results from experiment shows that thermal energy storage unit with integrated modules filled with phase change material can supply desired level of water temperature for twice as long at smaller temperature level as sensible thermal energy storage what is the consequence of higher energy density that can be stored during phase change. The advantage of phase change materials is in thermal energy storage for applications that needs narrow temperature range of supplying and storing thermal energy what is the subject matter of consideration in the case of HEART project.
Subzone Control of Air Distribution to Improve Thermal Comfort and Energy Efficiency
Authors: Zhang Sheng , Cheng Yong , Shao Xiaoliang , Lin Zhang
Published: August 2019

The conventional method for air distribution (e.g., mixing ventilation and stratum ventilation) controls the averaged thermal condition in the occupied zone to satisfy the averaged thermal preference of a group of occupants. However, since the thermal environment cannot be absolutely uniform, the microclimates of occupants can be distinct from the averaged thermal condition of the occupied zone. Moreover, the thermal preferences of occupants are well recognized to be diversified beyond the averaged value. Thus, the conventional method is unable to ensure thermal comfort and risks energy wastage because of overcooling. The method proposed by this study divides the occupied zone into several subzones, and determines the supply air parameters to optimize the overall performance regarding thermal comfort and energy efficiency of the subzones using the multi-criteria decision-making technique. Thermal comfort is indicated by the thermal deviation of the achieved thermal conditions of the subzones from the respective thermal preferences, and energy efficiency is indicated by the heat removal efficiencies of the subzones. Case studies based on experiments of stratum ventilation have demonstrated the effectiveness of the method proposed. Results show that the method proposed achieves thermal comfort for each subzone, and improves the overall performance by 2.1% to 31.0%.
Unsteady RANS Simulation of Air Distribution in a Ventilated Classroom with Numerous Jets
Authors: Ivanov Nikolay , Zasimova Marina , Smirnov Evgueni , Abramov Alexey , Markov Detelin , Stankov Peter
Published: August 2019

The study is devoted to the Unsteady Reynolds-Averaged Navies-Stokes (URANS) simulation of ventilation in an isothermal room with numerous jets supplied from ceiling diffusers. The computations of the airflow under the test conditions considered were carried out in the classroom of the Technical University of Sofia with no occupants. The room floor has a simple rectangular form, but several columns, beams, window sills, and four radiators are located inside the room that makes the geometry more complex. Air is supplied to the room through four ceiling fan coils, the Reynolds number is 2×104. Calculations were carried out using the ANSYS Fluent 18.2 software with the standard k-ε turbulence model chosen. Computational meshes of up to 33 million hexahedral cells clustered to the inlet and outlet sections were used. The main aim of the study presented is to analyze and discuss the complicated 3D flow structure in the room and to give foundation for future measurements of air velocity field in the room.
Thermal comfort and draught assessment in a modern open office building in Tallinn
Authors: Kiil Martin , Mikola Alo , Thalfeldt Martin , Kurnitski Jarek
Published: August 2019

Modern office building users have high expectations about the working environment and thermal comfort, which requires the installation of complex technical systems such as combined cooling and ventilation. Room conditioning units of these systems must ensure temperature and ventilation control in a way that air velocity is low and the air temperature in acceptable range. Achieving air distribution avoiding draught is one of the key elements of a thermal comfort in modern office landscape. Higher air velocity in occupied zone is easily perceived as draught, which causes occupant dissatisfaction and complaints, as well as decrease in the productivity or effective floor space area. To reduce complaints, room air temperature setpoints or ventilation airflow rates are often modified, which may result in higher heating energy demand. In addition, excessive heating setpoint rise will not only consume more energy, but may cause health problems. Compared to cellular offices it is more difficult to ensure thermal comfort conditions in open office spaces where there are no walls for air flows. In addition, due to the higher number of employees it is more difficult to meet satisfactory conditions for everyone. The aim of this study was to evaluate thermal comfort parameters such as room air temperature, air speed and supply air temperature and how the users sense it in a modern office building in Tallinn, Estonia. Design room air temperature setpoints and air exchange rate were evaluated on open office spaces. Measured data with web-based indoor climate questionnaire was analysed. Results show which design and measured parameters make it possible to match the user comfort at all times.
Characteristics of airborne transmission under stratum ventilation
Authors: Huang Tao , Ai Zhengtao , Melikov Arsen
Published: August 2019

The objective of this study is to investigate the characteristics of airborne spread of exhaled droplet nuclei between two occupants in a space conditioned by a horizontal air distribution method, known as stratum ventilation. Experiments were conducted in a full-scale climate chamber. Two breathing thermal manikins were used to simulate a standing infected person and a standing exposed person, respectively. Tracer gas (N2O) was added into the air exhaled by the infected manikin. The tracer gas concentrations in the air inhaled by the exposed manikin and at the ventilation exhaust were continuously monitored. ACH was kept at 2 h-1. The variables in the experiments include the positioning of the manikins, the distance between manikins, and the room air temperature. The horizontal supply airflow to the breathing zone strongly intensifies the mixing between the flow of exhalation and the room air, which reduces the exposure risk of occupants at close proximity and flattens the risk-distance curves. The homogenization of concentration weakens considerably the importance of the relative positioning and location of the infected and exposed persons. All those characteristics of airborne transmission may not be maintained, however, if the horizontal supply jet does not interact directly with the occupants. The findings from this study are intended to contribute for better understanding of airborne transmission indoors.
Utilization of electrostatic precipitators for healthy indoor environments
Authors: Altun Ayse Fidan , Kilic Muhsin
Published: August 2019

A healthy and comfortable indoor environment is the most basic requirement of human beings. The importance of indoor air quality has been increasing day to day. Although ventilation systems have an essential role in improving indoor air quality, it is inevitable to clean the particulates, microorganisms and pollutant gases in the outside fresh air before being transferred to the indoor environment. Electrostatic precipitators are commonly used for collecting particles mostly in industrial plants. This paper presents a review of electrostatic filtration technology. In this study, theoretical and technical developments of electrostatic precipitators, design parameters that effect filtering performance, advantages, challenges, and limitations are discussed.