All-glass Vacuum Research Articles

The Influence of Storage Tank Volume on the Nighttime Heat Dissipation and Freezing Process of All-Glass Vacuum Tube Solar Water Heaters

The issue of freezing often occurs when using all-glass vacuum tube solar water heaters during cold winter seasons, leading to problems such as pipe ruptures and tank leakage. In order to further study the nocturnal heat dissipation and freezing characteristics of these heaters, a three-dimensional transient numerical model of their nocturnal heat dissipation was established. The model simulated the nocturnal heat dissipation process, and experimental validations were conducted through nocturnal temperature drops of the collector and temperature drops of individual tubes without a storage tank. Experimental and simulation results revealed that in clear weather conditions during cold winters in Luoyang, the all-glass vacuum tube solar water heaters experienced freezing issues during the night, with freezing predominantly starting from the bottom surface of the vacuum tubes. The frozen length along the tube wall and the thickness of ice at the bottom section reached up to 1180 mm and 5 mm, respectively. In the absence of a storage tank, the freezing situation was severe, with approximately 4/5 of the individual tubes completely frozen. Under specified operating conditions, different storage tank volumes exhibited varying degrees of freezing in the all-glass vacuum tube solar water heaters. When the volume was increased to 15 L, the temperature drop in the storage tank and the vacuum tubes decreased by 12.1% and 7.6%, respectively. Larger storage tank volumes resulted in reduced freezing risks in all-glass vacuum tube solar collectors. This study provides valuable guidance for the design and application of solar collectors and serves as a reference for the development and application of solar energy utilization technologies.

Investigation of the effect of solar water heating of vacuum tube on heat loss coefficient

In the solar thermal utilization system, it is necessary to study the factors that affect the heat loss of the hot water storage tank. Therefore, the heat loss coefficient of the hot water storage tank in the all-glass vacuum tubular solar water heater is calculated using experiments and measured data in the present study. Then the problem is analyzed in forced circulation and non-forced circulation conditions. According to the results of the investigation, the heat loss coefficient of the thermal storage tank in the forced circulation state is 12.6 times that of the non-forced circulation condition. The heat loss coefficient is impacted by the tank temperature, intake, and exit water temperatures, circulating water flow rate, wind speed, and ambient temperature, as determined by a linear regression analysis of the experimental data. It is found that in the non-forced circulation, wind speed significantly affects the heat loss coefficient, specifically, the heat loss coefficient increases by 0.49 W/(m2·℃) for every 1 m/s increase of wind speed when all other factors are constant. But wind speed can be neglected in the forced circulation condition. Moreover, it is observed that as the inlet water temperature increases, the corresponding heat loss coefficient increases.

Research on Thermal Insulation Measures of Power Equipment Condition Monitoring Device in Cold Regions

Outdoor winter temperatures in other northern regions such as Heilongjiang Province are relatively low. As an important equipment of ensuring the safety of transmission lines, the stability of the condition monitoring devices is facing great challenges. In order to ensure that the condition monitoring device can operate reliably in winter, so as to avoid the influence of low temperature in winter on the reliability of the condition monitoring device, in this paper a device is designed that uses solar heat for heat preservation for power equipment condition monitoring device. The device uses an all-glass vacuum solar collector tube to convert solar energy into heat, and realizes instant feedback and control of temperature through a bimetallic temperature sensor. After testing, in winter, the internal temperature of the heat insulation box can be increased by about 30°C compared with the outside, which can effectively improve the winter operating environment of the device.

Comparative Study on Performance of Renewable Energy Building Energy Supply System

The air source heat pump water system test bench and the compact all-glass vacuum tube solar water heating system test bench are (were) built on the roof of two adjacent teacher’s apartment buildings with the same structure, shape and material were constructed to study the performance of energy supply systems for different types of renewable energy buildings. The energy supply system performance and the performance parameters are comprehensively and systematically analyzed in the same environment conditions of the same period. The results show that the weight coefficients of the performance parameters of the two energy supply systems are equal by means of extension theory analysis. At the last, the comprehensive correlation degree Kj(1) of water outlet temperature on the performance of renewable energy power supply system is 2.07, the comprehensive correlation degree Kj(2) of water inlet temperature is 2.04, the comprehensive correlation degree Kj(3) of air temperature is 2.14, the comprehensive correlation degree Kj(4) of solar radiation is 4.97, and the comprehensive correlation degree Kj(5) of sunshine hours is 3.78.

All-glass vacuum tube heat transfer simplified model

This paper addresses the design of an algorithm that estimates the irradiance and the selective layer temperature of the all-glass vacuum tube as a function of the ambient temperature in Bucaramanga, Northern Colombia. A Matlab code to meteorological National Aeronautics and Space Administration data processing and to find a linear relationship between the irradiance and ambient temperature on the location of study, was developed. The behavior of this relationship for several hours of the day was studied, and it was found that it is possible to use this relationship as a reliable preliminary approach in water heating systems design using all-glass vacuum tube. This facilitates the design calculations and would encourage the use of solar energy in water heating systems in Colombia.

Rate capability and magnetic field tolerance measurements of fast timing microchannel plate photodetectors

Microchannel plate photodetectors provide both picosecond time resolution and sub-millimeter position resolution, making them attractive photosensors for particle identification detectors of a future U.S. Electron Ion Collider. We have tested the rate capability and magnetic field tolerance of 6 × 6 cm2 microchannel plate photodetectors fabricated at Argonne National Laboratory. The microchannel plate photodetector is designed as a low-cost all-glass vacuum package with a chevron pair stack of next-generation microchannel plates functionalized by atomic layer deposition. The rate capability test was performed using Fermilab’s 120 GeV/c primary proton beam, and the magnetic field tolerance test was performed using a solenoid magnetic with tunable magnetic field strength up to 4 T. The measured gain of the microchannel plate photodetector is stable up to 75 kHz/cm2 and varies depending on the applied magnetic field strength and the rotation angle relative to the magnetic field direction.

Study on convection improvement of standard vacuum tube

For the standard all-glass vacuum tube collector, enhancing the vacuum tube axial natural convection can improve its thermal efficiency. According to the study of the standard all-glass vacuum tube, three kinds of guide plates which can inhibit the radial convection and increase axial natural convection are designed, and theory model is established. Experiments were carried out on vacuum tubes with three types of baffles and standard vacuum tubes without the improvement. The results show that T-type guide plate is better than that of Y-type guide plate on restraining convection and increasing axial radial convection effect, Y type is better than that of flat plate type, all guide plates are better than no change; the thermal efficiency of the tube was 2.6% higher than that of the unmodified standard vacuum tube. The efficiency of the system in the experiment can be increased by 3.1%.

A novel solar absorption refrigeration system using the multi-stage heat storage method

This paper introduces a multi-stage heat storage system using phase change materials with different melting points into the heat pump solar absorption refrigeration system which proposed by our earlier research work. Using meteorological data for the city of Nanjing, the performance of the novel system with a cooling capacity of 10kW is quantitatively analyzed: (1) More than 91m2 of solar collection area is required for the single flat-plate collector to satisfy the daily need of cooling. (2) Four different types of collectors, including single flat-plate collector, all-glass vacuum tube collector, heat pipe evacuated tube collector, and compound parabolic vacuum tube collector are compared. The results of solar collection areas show that the difference among them is not significant. Considering the building adaptability and production cost in the application designs, single flat-plate collector is preferred. (3) The coefficient of performance for the system with multi-stage heat storage system is approximately 1.3–2.4 times to that with the corresponding single-stage heat storage system at the given conditions. (4) The coefficient of performance of the novel system increases with the melting points of the phase change materials in the heat storage system when the solar radiation intensity is high (0.8kW/m2), and behaves the opposite when the solar radiation intensity is low (0.3kW/m2).

Study of the Solar Energy Drying Device and Its Application in Traditional Chinese Medicine in Drying

Background: We referred to nearly 40 years of development and application progress of solar dryer in China literature, especially its application in the field of Chinese herbal medicine drying. Objective: We explored the development direction of China’s development and application of solar dryers, especially focusing on its development and application in traditional Chinese medicine drying. Method: Five types of solar dryers including the greenhouse type solar dryer, the collector type solar dryer, the collector-greenhouse type hybrid solar dryer, the integrated solar dryer and the focusing type solar dryer accounted for the development and application of solar dryers up to 95% in China. The first three types of solar dryers are low temperature dryer (less than or equal to 70°C), while the latter two kinds of solar dryers are high temperature dryer (more than 70°C). In this paper, we respectively introduced and compared the structure, working principle, applications, advantages and disadvantages, and the research status of these five dryer. Results: The integrated solar dryer and the focusing type solar dryer belong to the high temperature dryer types are the future direction of development. Among them, the integrated solar dryer is relatively simple structure and has more promotion prospects. These two kinds of key drying device used in the dryer is the development direction of high efficient vacuum tube. On the other hand, because of their low cost, simple structure and the dry material requirements etc., the three types of low temperature dryers at low temperature for drying materials are also indispensable in the practical application. In contrast, the collector-greenhouse type hybrid solar dryer has more advantages, is the development direction of low temperature drying category. Conclusion: The collector tube which is the key element of the dryer was the core technology of solar dryer. Our country develops more successful of the all-glass vacuum solar thermal collectors and heat pipe-glass vacuum tube. Efficient vacuum tube collector technology is the future developed direction and is equally important to improve the quality of traditional Chinese medicine and dried.

Experimental Assessment of a Multi-Effect Solar Desalination System in Southern China

This paper presents the thermal performance of a multi-effect distillation (MED) solar desalination unit located in southern China. The system was designed and installed in April 2011, and has been in operation since that time till now. The seawater desalination system is driven by 60 m2 all-glass vacuum tubes solar collector with an additional rainwater utilization system to produce fresh water on both sunny and rainy days. The preliminary experimental results show that the water production of the system for per unit of solar collector area could reach up to more than 12.5kg/m2·day under the fine weather conditions. Water production of the system was stable in long period and the annual production could reach to 387.5 m3 in southern China. The economic performance of the system is also discussed. The cost of water production is estimated approximately 4.15 $/m3 for the 15-year service life.

Field test of a solar seawater desalination unit with triple-effect falling film regeneration in northern China

► A new four-stage distillation has been designed, constructed and field tested. ► The field testing had been carried out under the real weather condition for 2 years. ► Annual water production of the system could reach to 250 tons in northern China. ► The cost of water production is estimated approximately 4.6 Dollar/ton for the service life. Based on the mechanism of falling film evaporation condensation, a new four-stage distillation unit with triple-effect regeneration has been designed, constructed and field tested. The seawater desalination system is driven by 80 m 2 all-glass vacuum tube solar collection system with an additional 1 kW wind power system to provide electricity for pumps. The field testing and monitoring of the system had been carried out under the real weather condition for 2 years. The results show that the water production of the system for per unit of solar collector area could reach up to more than 12 kg/m 2 /day under the fine weather conditions. Water production of the system was stable in long period and the annual production could reach to 250 tons in northern China. The economic performance of the system is also discussed. The cost of water production is estimated approximately 4.6 Dollar/ton for the 15-year service life.

All-glass vacuum tube collector heat transfer model used in forced-circulation solar water heating system

The aim of this paper is to establish the heat transfer model of all-glass vacuum tube collector used in forced-circulation solar water heating system. In this model, the simplified heat transfer of collector is composed of the natural convection in single glass tube and forced flow in manifold header. Thus the heat balance equation of water in single tube and the heat balance equation of water in manifold header have been established. The flow equation is also built by analyzing the friction and buoyancy in tube. Through solved these equations the relationship between the collector average temperature, the outlet temperature and natural convection flow rate have been obtained. From this relationship and energy balance equation of collector, the collector outlet temperature can be calculated. The validated experiments of this model were carried out in winter of Beijing.

A three-dimensional performance analysis of all-glass vacuum tubes with coaxial fluid conduit

The thermal performance of a solar system composed of parallel, all-glass (double skin) vacuum tubes has been investigated by using a three-dimensional analytical model. Each vacuum tube is equipped with a coaxial fluid conduit for water to flow through and collect the sun's thermal energy. The space between the exterior of the fluid conduit and the glass tube is filled with antifreeze solution to facilitate heat transfer from the solar heated absorber surface to water and to prevent the functional problems due to freezing in frigid weather conditions. Different from one-dimensional analytical models, the three-dimensional model considered in the present analysis enables the prediction of spatial variation of water temperatures as it flows through the coaxial conduit. This is quite useful in extracting major variables for the operation of the solar system using all-glass vacuum tubes as considered in the present investigation.

The performance simulation of all-glass vacuum tubes with coaxial fluid conduit

A numerical investigation has been carried out for a solar system, which consists of all-glass (double skin) solar vacuum tubes. Water is heated as it flows through the coaxial fluid conduit inserted in each tube. The space between the exterior of the fluid conduit and the glass tube is filled with antifreeze solution. This is to facilitate heat transfer from the solar heated absorber surface to water and to prevent the functional problems due to freezing in frigid weather conditions. Results show good agreement when compared with other experimental data demonstrating the reliability of the present model. The one-dimensional numerical model could be used efficiently in designing all-glass solar collector tubes with different geometrical parameters other than those considered in the present analysis.

Incubation of 14C-trichloroethylene vapor with rat liver microsomes: uptake of radioactivity and covalent protein binding of metabolites.

Microsomal uptake irreversible protein binding of labelled trichloroethylene was measured following incubation with rat liver microsomes in an all-glass vacuum system.

Liver microsomal uptake of [ 14C]vinyl chloride and transformation to protein alkylating metabolites in vitro

[1,2- 14C]Vinyl chloride gas was incubated with rat liver microsomes in an all-glass vacuum system. Microsomal uptake and irreversible protein binding of vinyl chloride radioactivity was determined. Both uptake of vinyl chloride by microsomes and alkylation of proteins by vinyl chloride metabolites were dependent on incubation time, enzymatically active microsomes, NADPH, oxygen, and the partial pressure of vinyl chloride in the atmosphere, and could be inhibited by carbon monoxide. During incubation in presence of NADPH, 10 times more vinyl chloride was taken up by microsomes than in absence of NADPH. Uptake of vinyl chloride by albumin solutions and liposomal suspensions was in a similar range compared to the microsomal uptake without NADPH. Addition of glutathione and cytoplasmic fractions to microsomal incubations with NADPH led to an increase in microsomal uptake of vinyl chloride and to a decrease in protein alkylation by vinyl chloride metabolites. If trichloropropene oxide was present in the microsomal incubation, the protein alkylation reaction by vinyl chloride metabolites was increased twofold, while the microsomal uptake of vinyl chloride was not influenced. Our results are consistent with the view that the microsomal uptake of vinyl chloride radioactivity is due to transformation of vinyl chloride gas to nonvolatile metabolites by microsomal enzymes and that chloroethylene oxide might be the primary microsomal metabolite of vinyl chloride capable of reacting with proteins.