Experimental Study of a Low-Temperature Compressor-Ejector Refrigeration System

The decrease of electricity consumption by refrigerators at least by 10% reduces the load on the power plant by 1.5%, which is a very significant magnitude in the scale of the planetary balance. The calculated-theoretical research of new schemes of combined refrigerating machines with booster and compressive ejector stage showed the reduction of energy consumption, depending on the operating mode, from 10 to 40%. The ejector stage is produced for new systems and for operating compression refrigerating machines, while the price of the additional equipment does not exceed 10% of the cost of the compressor. For the experiment, the basic schematic with booster ejector was considered, where the ballast vapor is used as the motive flow, separated after the first throttling to an intermediate pressure. The purpose of the experiment is to determine the exact value of the optimal intermediate pressure, which ensures the maximum energy values of the entire installation. The decrease of the intermediate pressure, on the one hand, leads to an increase of ballast steam rate, but, on the other hand, the motive steam, the pressure and the temperature are decreased. The entrainment ratio is set by the ratio of the vapor consumption from the evaporator to ballast vapor consumption and is determined by the flow parameters after the first throttling. The main parameter in the system is the compressed vapor pressure behind the ejector, which determines the energy and volume parameters of the compressor. As a result of the experiments, all characteristics of the ejector stage, the compressor and the installation as a whole were obtained. The experimental characteristics of the system prove the results of calculations and simulation of the ejector. The effect of the presence of oil on the operation of the ejector was insignificant, about 1-3%. However, the requirements for separating the oil after the compressor remain rigid. The research has shown both high power plant parameters and stable performance characteristics

The Analysis of Binary Fluid Ejector Assisted Solar Desalination System

The proposed desalination technology represents the combined processes of distillation and congelation of seawater. While distilling runs at two-stage, the condensation heat of the distillate vapors is utilized for cold generation in the Binary Fluid Ejector Refrigeration System (BERS). The congelation process is organized with continuous heat recuperation that enables to mark up about 80% of the fresh water, produced by BERS. The system tolerates any type of seawater (30k ≤ TDS ≤ 100k) and operates with solar thermal heat of 338-356F. The integrated binary fluid ejector heat pump doubles the input of thermal energy at 248F, so the overall output fresh water efficiency is 9 times higher compared to the single stage distillation. This technology represents the novel, economically viable, unrivalled approach that is free from disadvantages typical for most of existed desalination systems. The most efficient flat plate vacuum solar collectors are selected for the study of the integrated solar desalination system. Extensive thermodynamic analysis of the system performance and experimental validation of the results are the core research and development efforts. The main component to operate the solar thermal congelation process is BERS using a binary mixture of low-boiling point refrigerants as the driving fluid of the system. The recent research and experimental studies on utilization of the low-boiling point refrigerants in the ejector-based systems resulted in the 30-50% improved efficiency compared to steam-driven ones, however, it only allowed the ejector systems to become competitive with the other types of the low-grade heat operated heat pumps, such as absorption and adsorption technologies. The application of binary fluids in the ejector-based cooling systems has boosted the energy efficiency as much as 80-120% that potentially makes the binary fluid ejector system the most advanced thermally-driven heat pump ever created. The binary fluid application in BERS allows energy losses reduction by decreasing the velocity difference between working and refrigerant fluids. Binary fluid systems unlike single fluid ones perform a power cycle with a working fluid, that consumes relatively less heat, while the reverse cycle is performed by the most efficient refrigerant fluid, which removes 2-3 times more heat from the low temperature source per refrigerant fluid unit mass. It is important to achieve the maximum entrainment ratio and the lowest ratio of the specific cooling capacity to the specific heat consumption. The contact between primary flow and the secondary flow in the ejector is required for kinetic energy and momentum transfer, which results in both fluids mixing and thereafter requires the formed binary fluid separation by the single components. In order to separate the flows, it is necessary to condense high temperature fluid (working fluid) in fractionating condenser, where, as a result of heat and mass transfer, the concentration of working fluid increases in liquid phase and refrigerant fluid - in vapor phase

Solar Cooling for Mediterranean Region as a Crop Storage Technology

The Mediterranean region is a major supplier of fruits and vegetables to Europe. Fruit harvesting continues the year round, including certain fruits to be harvested from September to June. The follow up of the specific temperature and humidity storage conditions becomes significantly energy intensive that adversely affects the energy balance of exporters, especially when the producing country is run out of affordable energy sources. In order to reduce the energy costs during the crop storage and avoid the crop wastage, the solar ejector cooling systems were introduced. These systems developed recently, are fully autonomous, does not contain mechanically moving parts, reliable and durable in performance. In addition, the new type of thermopump with high energy and performance characteristics was elaborated and tested within the ejector cooling system, driven by the imitated low-grade heat. The results of theoretical and experimental study of the thermopump and the ejector refrigeration system were described in the study along with factors that affect the system's efficiency. The crop storages operating regimes were reviewed during the storage season for the selected products. Temperature ranges defined for systems with constant area ratio ejector at COP values remains stable. Cold accumulators or duplicate conventional systems, applied during the night were considered as backup systems, supporting a non-stop operation

Thermodynamic Analysis of Thermo-vacuum Clothes Drying Operation

Clothes drying accounts for a significant amount of energy consumed in residential and commercial sectors. Thermal vacuum clothes drying technology (TVCD) is proposed as an advanced clothes dryer that can significantly reduce the energy requirements by expediting the drying process. In the conventional convective clothes dryer, hot dry air is introduced into the drum which gets in direct contact to dry the clothes. This process is energy inefficient since the significant amount of heat and the water carried out with the exhaust stream are wasted. In contrast to the conventional convective drying technique, the drying mechanism of TVCD is through nucleate boiling at low temperature due to reduced vessel pressure. The process is not only efficient but also reduces the required time for drying. This paper aims to develop a comprehensive thermodynamic model to predict the transient drying process of TVCD. The three-stage system-level model can simulate the water content variation in the textile under various operational conditions, with detailed analysis of individual components. The preliminary results show that the drying time of 3 lb textile from 70% to 2.5% in TVCD is approximately four times less than the time required in the conventional clothes dryer. Parametric studies help understanding the effect of operating conditions and component geometry on the system performance, and the system\u27s energy consumption is also analyzed

Experimental Drying Characteristics Of Fabrics Under Vacuum

A significant amount of the energy consumed in both residential and commercial sectors is used for clothes drying. In conventional convective clothes drying, hot dry air at atmospheric pressure is passed over and through the clothes in order to remove moisture. Both the heat and water carried out are wasted to ambient resulting in an inefficient process. Additionally, the elevated drying temperatures can damage the fibers of the clothes, reducing their useful lifespan. By drying clothes at pressures below atmospheric, the temperature required to drive out moisture can be reduced. The objective of this study is to investigate the drying behavior of different fabrics under sub-atmospheric conditions. A special apparatus is designed and used for this study with appropriate control on the pressure and contact surface temperature. A wet cloth is placed on a heated plate within a vacuum chamber. The mass of the cloth is measured by a balance while the plate’s temperature and the vacuum chamber’s pressure are maintained. Moisture is driven out of the cloth by conduction from the plate. Clothes are dried from approximately 60% to 0% of moisture by mass and curves of moisture percentage versus time are developed for each fabric at set temperatures and pressures. The overall goal of the analysis to establish the drying behavior of clothes under reduced pressure conditions. The resulting data is summarized in form of appropriate performance correlations which can be used for the design of full-scale devices capable of drying under the considered conditions

Solar Cooling Technologies Using Ejector Refrigeration System

The continuous search for the effective cold generation methods resulted in the creation of thermally driven ejector refrigeration systems (ERS). Producing cold at various temperatures, the ERS serves to save electric energy and reduce greenhouse gas emissions. The theoretical analysis of the ejector cycles carried out for various ERS has proved its capability to generate the cold at +12°C to –40°C, reaching the COP values at 0.7 to 0.1 respectively. The combined cycles of water conversion, heat and cold production appear to be especially effective