Search

Freezing efficiency was the main factor affecting the efficiency of cold chain logistics and transportation. To further the ice storage performance, three mathematical models of the ice storage equipments were established to explore the influence of the number and the diameter of the tubes on the freezing time, heat flux, and natural convection by analyzing the distribution of the ice fraction and velocity. The results showed that the total freezing time of Type II and Type III, which were arranged the micro-tube, were 76.42 min and 137.50 min, which was more than 90% less than that of type I. Due to a ring cavity of water appearing near the shell of the ice storage tank increased the water natural convection, the freezing time required to increase the ice fraction by 0.05 gradually increased especially with the ice fraction greater than 0.95. To better evaluate the ice storage performance, the freezing efficiency was introduced. The freezing efficiency of Type II and Type III was lower than that of Type I by more than 2.24% and 2.14%, respectively, for the ice fraction range of 0.75 ~ 1. Given the freezing time and ice storage efficiency, it could be found that using type II and making the ice storage rate reach 0.95 could shorten the freezing time and improve the ice storage efficiency. [ABSTRACT FROM AUTHOR]

In order to improve the supply air quality, more and more investigations have been conducted on enthalpy exchanger (or total heat exchanger). Enthalpy exchanger consists of functional layers and support layers. The functional layers, which exchange the heat and moisture between fresh air and exhausted air, play a critical role in improving efficiencies of the exchanger. A paper matrix with low cost and easy fabrication is widely used as the functional layers in current enthalpy exchangers. In this study, modified paper by spraying calcium chloride solution is proposed to improve the hygroscopicity of conventional material. Novel functional layers with different solution concentrations of 5, 10, 20, 30, and 40% are fabricated and analyzed. Performance of exchangers made by the modified functional layers and by original layers are tested and compared. Results show that when airflow velocity is 0.3 m/s (corresponding to 50 m3/h), sensible efficiency, latent efficiency, and enthalpy efficiency of modified enthalpy exchanger with use of 30% solution increase from 62, 44, and 49% to 75, 69, and 71% in the winter conditions and from 53, 51, and 52% to 75.8, 71.5, and 73% in the summer conditions compared with original exchanger, the increasing of pressure drop caused by treatment can be ignored. Besides, application of the modified enthalpy exchanger is tested and it is proven that the modified exchanger can obtain better performance compared with original exchanger. [ABSTRACT FROM PUBLISHER]

A performance comparison of experimental results for CO2trans-critical cycle is presented for an overview of the current level of technology. The published performance data were collected as research objects through comprehensive literature review on experimental research. The methods for data processing, error analysis, and performance evaluation are introduced in the research methodology section. Through the proposed research method, 28 groups of performance results from developed prototypes or test rigs are compared and analyzed using the coefficient of performance and the second law efficiency of thermodynamics. A discussion of the performance comparison between developed CO2devices and commercial products of synthetic working fluid is also presented based on China's national standards (General Administration of Quality Supervision, Insection and Quarantine of the People's Republic of China 2001, 2003). Based on the comparison results, the state-of-art and possible research directions for CO2trans-critical cycle technology are summarized and presented. [ABSTRACT FROM AUTHOR]

Solar energy refrigeration is very attractive for low-temperature grain storage because the cooling load of low-temperature grain storage is roughly in phase with solar energy availability. In this study, a solar-powered adsorption chiller was developed with aim of developing an alternative refrigeration device for low-temperature grain storage. The solar-powered adsorption chiller was put into experimental operation during summer and autumn. Test results show that the solar-powered adsorption chiller can produce a cooling capacity about 66–90 W per m2collector area. Its daily solar-cooling COP (coefficient of performance) is about 0.1–0.13 under the climatic conditions of daily solar radiation being about 16–21 MJ/m2·day. With appropriate ventilation appliance, this kind of solar-powered adsorption chiller could be considered as an alternative for low-temperature grain storage in most areas of China. [ABSTRACT FROM PUBLISHER]