Flow boiling heat transfer of HFO1234yf and R32 refrigerant mixtures in a smooth horizontal tube: Part I. Experimental investigation

HFO1234yf has been proposed for mobile air-conditioners due to its low global warming potential (GWP) and performance comparable to that of R134a. However, its performance is inferior to that of R410A. This makes it difficult to be applied to residential air-conditioners. In order to apply the low-GWP refrigerant to residential air-conditioners, refrigerant mixtures of HFO1234yf and R32 are proposed, and their flow boiling heat transfer performances were investigated at two mass fractions (80/20 and 50/50 by mass%) in a smooth horizontal tube with an inner diameter of 2 mm. The experiments were conducted under heat fluxes ranging from 6 to 24 kW/m² and mass fluxes ranging from 100 to 400 kg/m² s at the evaporation temperature of 15 °C. The measured heat transfer coefficients were compared with those of pure HFO1234yf and R32. The results showed that the heat transfer coefficients of the mixture with an R32 mass fraction of 20% were 10–30% less than those of pure HFO1234yf for various mass and heat fluxes. When the mass fraction of R32 increased to 50%, the heat transfer coefficients of the mixture were 10–20% greater than those of pure HFO1234yf under conditions of large mass and heat fluxes. Moreover, the heat transfer coefficients of the mixtures were about 20–50% less than that of pure R32. The performances of the mixtures were examined at different boiling numbers. For refrigerant mixture HFO1234yf and R32 (80/20 by mass%), the nucleate boiling heat transfer was noticeably suppressed at low vapor quality for small boiling numbers, whereas the forced convective heat transfer was significantly suppressed at high vapor quality for large boiling numbers. This indicates that the heat transfer is greatly influenced by the mass diffusion resistance and temperature glide of the mixture.     

Linear stability analysis on surface tension‐induced instability of LiBr aqueous solution absorbing water vapor

Linear stability analysis is applied to the absorption of water vapor into lithium bromide aqueous solution film when a small amount of surfactant is added to the solution. The condition under which an instability occurs and the role of the surfactant are investigated. The analysis shows that the film becomes unstable at a positive Marangoni number when the heat transfer is more determining than the mass transfer. In contrast, when the mass transfer is more determining, the film becomes unstable at a negative Marangoni number. As for LiBr aqueous solution, mass transfer is more rate determining than heat transfer, so the instability is promoted and maintained when the Marangoni number is negative. In the case of film flow absorption, the analysis shows that the disturbance of the film flow becomes more unstable in the transverse direction than in the longitudinal direction as the Reynolds number increases. © 2000 Scripta Technica, Heat Trans Asian Res, 29(7): 581–597, 2000     

Nanoindentation and morphological analysis of novel green quasi-ceramic nanocoating materials

The eco-friendly (green) silicone nanocoating compositions containing titanium nanoparticles were developed and tested for the changes in nanomechanical properties using the nanoindentation technique. Titanium-based nanoparticles were incorporated by two different methods. The nanocoating compositions were studied with the Fourier Transform Infrared spectroscopy (FTIR) and Raman spectroscopy. The surface morphology of the nanocoatings was studied with Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). The nanomechanical properties of the nanocoatings were studied using the standard nanoindentation test method and the new substrate independent nanoindentation test method. The results obtained from the two test methods confirm the validity of the model used to develop the substrate independent nanoindentation test method. In brief, this study discusses the development of silicone based nanocoating materials and nanomechanical properties of green nanocoatings containing two different types of nanoparticles, evaluated using two different test methods.     

Intracellular imaging of Qdots‐labeled DNA in cyanobacteria

In this contribution, they have attempted to develop a labeling technique for in vivo imaging of functionally active plasmid DNA in cyanobacterial cells through its decoration with semiconductor quantum dots (Qdots) as fluorescent nanoprobes. For that purpose biotinylated plasmid slr2060 DNA was conjugated with Qdots‐streptavidine. The intact DNA was visualized in a single green color by light microscopy. These Qdots‐DNA conjugates were capable of expressing the acyltransferase enzyme. Qdots‐DNA conjugates and confocal microscope imaging technique were adopted to visualize the gene transport across the membrane of the live cyanobacteria cell in real time. Long‐term kinetic study enabled to reveal the steps of extracellular and intracellular microenvironment for plasmid transportation into the live cell. To confirm these processes a confocal microscope and indicator plate assay test were applied in tandem. In this contribution, Qdots‐labeled plasmid DNA was utilized for the first time for long‐term intracellular imaging studies in cyanobacteria species PCC6803. The results showed that the Qdots‐labeled plasmid DNA detection could be used as a powerful labeling technique for visualization of exogenous DNA entry and tracking into living cells by confocal microscopy. Microsc. Res. Tech. 79:447–452, 2016. © 2016 Wiley Periodicals, Inc.     

Photofading, photosensitization and the effect of aggregation on the fading of triphenodioxazine and copper phthalocyanine dyes on cellulosic film

The photosensitized oxidation of four triphenodioxazine (TPDO) reactive dyes and a copper phthalocyanine (CuPc) reactive dye on cellulosic films by Rose Bengal (RB) was examined in aqueous solution under aerobic conditions. The rates of photo-oxidation of 4,11-bis(vinylsulfonyl)TPDO dyes were smaller than those obtained for 3,10-bis(disubstituted triazinyliminoethylimino)TPDO dyes. The rates of photofading of the four TPDO dyes and a CuPc dye on cellulose were similar in the order to the rates of the photosensitized oxidative fading with RB. Photo-oxidation left the aromatic residue from TPDO ring along with the reactive anchor bound to cellulose. No aggregation effect was observed on the fading of TPDO dyes and a CuPc dye on cellulose. The photosensitivity of the TPDO dyes was very small, this being estimated by the photosensitized fading of an aminopyrazolinylazo dye (Yellow dye) on cellulosic films dyed in admixture with TPDO dyes by use of a yellow filter to shield Yellow dye on exposure. It is concluded that the good light-fastness of the TPDO dyes on cellulosic substrate is attributed to the very small photosensitivity in spite of their relatively large ease with which they are oxidized.     

Prediction of air coil performance under partially wet and totally wet cooling conditions using equivalent dry-bulb temperature method

This paper mainly deals with the cooling and dehumidifying performance of air coils used in refrigeration and air-conditioning systems. A new method, equivalent dry-bulb temperature (EDT) method, is proposed for calculating the heat and mass transfer and for predicting the cooling modes (totally wet, partially wet, and totally dry) of moist air over the coil surface. A numeric model is further developed and validated with the experimental data of plain fin air coils. The deviation in both the cooling capacity and the vapor condensate estimated by the model is within the range of ±10%, and the prediction for the cooling modes of moist air over the coil surfaces is fairly exact.     

Effect of lubricating oil on cooling heat transfer of supercritical carbon dioxide

In this research, the cooling heat transfer coefficient and pressure drop of supercritical CO₂ with PAG-type lubricating oil entrained were experimentally investigated. The inner diameter of the test tubes ranged from 1 to 6 mm. The experiments were conducted at lubricating oil concentrations from 0 to 5%, pressures from 8 to 10 MPa, mass fluxes from 200 to 1200 kg m⁻² s⁻¹, and heat fluxes from 12 to 24 kW m⁻².In comparison to the oil-free condition, when lubricating oil entrainment occurred, the heat transfer coefficient decreased and the pressure drop increased. The maximum reduction in the heat transfer coefficients—about 75%—occurred in the vicinity of the pseudocritical temperature. The influence of oil was significant for a small tube diameter and a large oil concentration. From visual observation, it was confirmed that this degradation in the heat transfer was due to the formation of an oil-rich layer along the inner wall of the test tube. However, when the oil concentration exceeded 3%, no further degradation in the heat transfer coefficient could be confirmed, which implies that the oil flowing along with CO₂ in the bulk region does not influence the heat transfer coefficient and the pressure drops significantly. For a large tube at a lower mass flux, no significant degradation in the heat transfer coefficient was observed until the oil concentration reached 1%. This is due to the transition of the flow pattern from an annular-dispersed flow to a wavy flow for a large tube, with CO₂ flowing on the upper side and the oil-rich layer on the lower side of the test section.     

In Vitro Tumor Cell-Binding Assay to Select High-Binding Antibody and Predict Therapy Response for Personalized 64Cu-Intraperitoneal Radioimmunotherapy against Peritoneal Dissemination of Pancreatic Cancer: A Feasibility Study

Peritoneal dissemination of pancreatic cancer has a poor prognosis. We have reported that intraperitoneal radioimmunotherapy using a ⁶⁴Cu-labeled antibody (⁶⁴Cu-ipRIT) is a promising adjuvant therapy option to prevent this complication. To achieve personalized ⁶⁴Cu-ipRIT, we developed a new in vitro tumor cell-binding assay (⁶⁴Cu-TuBA) system with a panel containing nine candidate ⁶⁴Cu-labeled antibodies targeting seven antigens (EGFR, HER2, HER3, TfR, EpCAM, LAT1, and CD98), which are reportedly overexpressed in patients with pancreatic cancer. We investigated the feasibility of ⁶⁴Cu-TuBA to select the highest-binding antibody for individual cancer cell lines and predict the treatment response in vivo for ⁶⁴Cu-ipRIT. ⁶⁴Cu-TuBA was performed using six human pancreatic cancer cell lines. For three cell lines, an in vivo treatment study was performed with ⁶⁴Cu-ipRIT using high-, middle-, or low-binding antibodies in each peritoneal dissemination mouse model. The high-binding antibodies significantly prolonged survival in each mouse model, while low-and middle-binding antibodies were ineffective. There was a correlation between in vitro cell binding and in vivo therapeutic efficacy. Our findings suggest that ⁶⁴Cu-TuBA can be used for patient selection to enable personalized ⁶⁴Cu-ipRIT. Tumor cells isolated from surgically resected tumor tissues would be suitable for analysis with the ⁶⁴Cu-TuBA system in future clinical studies.