Theoretical analysis of low GWP mixture R600a/R1234ze as a possible alternative to R600a in domestic refrigerators

In this study, a thermodynamic analysis of R600a and R600a/R134ze mixture at three compositions of 0%, 20% and 50% R1234ze is measured in a domestic refrigerator. The main purpose of this study is to theoretically verify the possibility of applying the mixture R600a/R1234ze in large capacity refrigerator. The performance has been assessed for different condensing temperatures between 30 and 50? with constant -20? evaporating temperature .The performance of the refrigerator was compared in terms of volumetric cooling capacity, COP (coefficient of performance), compression ratio and compressor discharge temperature. The results show that the volumetric cooling capacity, COP, compressor power consumption and compressor discharge temperature of R600a/R1234ze mixture are similar to those of pure R600a,so that R600a compressor can be used for R600a/R1234ze mixture without any modifications. The amount charge of the mixture R600a/R1234ze is slight lower than that of R600a in the same equipment. Flammability decreases in R600a/R1234ze mixtures with increasing fractions of R1234ze. This is an desirable characteristic because of the large charge requirement of large refrigeration systems

Experimental investigation of flow boiling heat transfer and pressure drops characteristic of R1234ze(E), R600a, and a mixture of R1234ze(E)/R32 in a horizontal smooth tube

The saturated flow boiling heat transfer coefficients and frictional pressure drops characteristics of R1234ze(E), R600a, and L-41b (R1234ze(E)/R32 (27/73 mass %)) inside an 8 mm inner diameter horizontal tube were investigated. The experiment was carried out at the saturation temperature of 20°C with heat flux ranging from 5.0 to 10.0 kW·m −2 and mass flux ranging from 200 to 400 kg·m −2 ·s −1 . The influence of mass flux, heat flux, and quality on the heat transfer coefficients and frictional pressure drops were examined and discussed. The results show that the local heat transfer coefficients of R1234ze(E) are averagely 33% and 18% lower than those of R600a and L-41b, respectively. The frictional pressure drops of R1234ze(E) are 21% lower than those of R600a but 6% greater than those of L-41b. Meanwhile, the experimental data of local heat transfer coefficients and frictional pressure drops are compared with some well-known correlations available in literatures

Investigation of flow boiling heat transfer characteristic of mixture refrigerant L-41B in a horizontal smooth tube

The saturated flow boiling heat transfer characteristics of L-41b, R1234ze(E)/R32 (27/73 mass%), inside an 8 mm ID horizontal tube were investigated. The experiment were carried out at the saturation temperature of 10 to 20°C with heat flux ranging from 5 to 10 kW/m2 and mass flux ranging from 200-500 kg/m2s. The influence of mass flux, heat flux, and quality on the heat transfer coefficients were examined and discussed. The experimental data of local heat transfer coefficients were compared with four well-known correlations available in literatures. Additionally, a new vapour-phase multiplier correlation to predict the local heat transfer coefficients of L-41b flow boiling inside smooth tubes was developed. The results show that the deviations of the new correlation are within –24.98% to +14.68% to the experimental data and that the 95% prediction values are within ±15%

Cost-effective CuO nanotube electrodes for energy storage and non-enzymatic glucose detection

A facile strategy is developed for the in situ synthesis of low-cost, freestanding, binder-free CuO nanotube electrodes on a conducting Cu foil, totally eliminating non-active materials and extra processing steps. The synergy arising from the ameliorating structure, such as high porosity, large surface area and the ability for fast electron transport, make CuO nanotube electrodes ideal multi-functional electrochemical devices with excellent pseudocapacitive performance and a remarkable sensitivity to glucose for use as non-enzymatic biosensors (NGBs). The electrodes deliver remarkable specific capacitances of 442 and 358 F g(-1) at current densities of 1 and 20 A g(-1), respectively. The capacitance loss after 5000 cycles is only 4.6% at 1 A g(-1), reflecting the excellent cyclic stability of the supercapacitor. The biosensor made from CuO nanotubes presents an extremely rapid and accurate response to glucose in blood in a wide, linear range of 100 mu M to 3 mM, with a sensitivity of 2231 mu A mM(-1) cm(-2). These interesting discoveries may open up the potential for the further development of new, multi-functional electrodes possessing both excellent energy storage and biosensory capabilities

Spray-Coated CsPbBr₃ Quantum Dot Films for Perovskite Photodiodes

Large-area film deposition and high material utilization ratio are the crucial factors for large-scale application of perovskite optoelectronics. Recently, all-inorganic halide perovskite CsPbBr₃ has attracted great attention because of its high phase stability, thermal stability, and photostability. However, most reported perovskite devices were fabricated by spin-coating, suffering from a low material utilization ratio of 1% and a small coverage area. Here, we developed a spray-coating technique to fabricate a CsPbBr₃ quantum dot (QD) film photodiode which had a high material utilization ratio of 32% and a deposition rate of 9 nm/s. The film growth process was studied, and substrate temperature and spray time were two key factors for the deposition of uniform and crack-free QD films. The spray-coated photodiode was demonstrated to be more suitable for working in the photodetector mode because a low dark current density of 4 × 10^–4 mA cm^–2 resulting from an extremely low recombination current contributed to a high detectivity of 1 × 10¹⁴ Jones. A high responsivity of 3 A W^–1 was obtained at −0.7 V under 365 nm illumination, resulting from a low charge-transfer resistance and a high charge recombination resistance. We believe that the spray deposition technique will benefit the fabrication of perovskite QD film optoelectronics on a large scale

Mesoporous ZnCo2O4 nanoflakes grown on nickel foam as electrodes for high performance supercapacitors

ZnCo2O4 nanoflakes, as electrodes for supercapacitors, are grown on a cellular nickel foam using a costeffective hydrothermal procedure. The mesoporous ZnCo2O4 nanoflakes have large electroactive surface areas with strong adhesion to the Ni foam, allowing fast ion and electron transport. The nanoarchitecture electrodes deliver an excellent specific capacitance of 1220 F g(-1) at a current density of 2 A g(-1) in a 2 M KOH aqueous solution and a long-term cyclic stability of 94.2% capacitance retention after 5000 cycles. The fabrication strategy is facile, cost-effective, and can offer great promise for large-scale supercapacitor applications

Dielectrophoretic-Assembled Single and Parallel-Aligned Ag Nanowire–ZnO-Branched Nanorod Heteronanowire Ultraviolet Photodetectors

The branched hierarchical heteronanowires have been widely studied for optoelectronics application because of their unique electronic and photonic performances. Here, we successfully synthesized Ag nanowire–ZnO-branched nanorod heteronanowires based on an improved hydrothermal method. Then we fabricated single heteronanowire across a Au electrode pair with different gap widths and parallel-aligned heteronanowires on a Au interdigitated electrode with a dielectrophoresis method, indicating the flexibility and operability of the dielectrophoresis assembly method. Increased photocurrent and shortened response time could be obtained by air-annealing and Ar-plasma post-treatments. A large responsivity of 2.5 A W^–1 and a linear dynamic range of 74 dB could be obtained, indicating stable responsivity for both weak and strong illumination. The excellent photoresponse performance is attributed to the structure superiority of heteronanowires. The proposed strategy of dielectrophoresis-assembled heteronanowires provides a new opportunity to design and fabricate hierarchical nanostructure photodetectors