Comparative Research on Air Conditioner with Gas-injected Rotary Compressor through Injection Port on Blade

Rotary compressors are widely utilized in air conditionders and heat pumps. However, when rotary compressors were applied in room air conditioners, VRFs and domestic water heaters, the systems will experience heavily degradation of the heating capacity and COP as the ambient temperature goes low. Aimed at these problems, considerable research has been carried out to raise a series of solutions, such as economizer technology, cascade-type vapor compression heat pump system and two stage coupling heat pump system. At present, economizer technology has become a critical method to improve the performance of air source heat pumps with rotary compressors in low ambient temperature. A novel vapor injection structure on a blade for a rotary compressor has been proposed in previous paper to overcome the drawback of the traditional cylinder injection structure. Based on a verified numerical model, the performance of air source heat pumps with rotary compressors with different economizer technology including a two-stage rotary compressor, a single-stage rotary compressor with traditional injection structure and a single rotary compressor with the novel injection structure has been investigated. The results indicate that: compared to rotary compressors with traditional injection structure, air source heat pump with a rotary compressor with proposed injection structure can enhance the heating capacity and COP by 13%~15% and 4.8%~9.6%, respectively; and compared to the twin-cylinder rotary compressor, the performance of air source heat pump with a rotary compressor with proposed injection structure is almost the same, so the rotary compressor with the novel injection structure could be considered to replace the two-stage rotary compressor

A Novel Vapor Injection Structure on the Blade for Rotary Compressor

Rotary compressors have been extensively used in room air conditioners and household refrigerators for their advantages, including high efficiency, strong adaptability, and low cost. However, when air source heat pumps with rotary compressors are applied in cold regions, a series of problems appear. The gas injection has been proved an effective technology to enhance both the heating capacity and COP of scroll, screw, and rotary compressors. In the one-cylinder rotary compressor with gas injection, the compressor injection port is often opened on the cylinder wall. In order to extend the injection time for injecting more refrigerant, the injection port is settled as close as possible to the discharge port. However, the limited area of the injection port and the unavoidable back-flowing of the injection refrigerant into the suction tube diminish the merits of gas injection on the one-cylinder rotary compressor. A novel vapor injection structure on the blade for the rotary compressor has been proposed in this paper to overcome the back-flowing drawback of the traditional cylinder injection structure and increase the injection area. Based on a verified numerical model, the performance of a rotary compressor with the blade injection structure has been investigated. The results indicate that: the proposed vapor injection structure can eliminate the back-flowing of the injected refrigerant; compared to the traditional injection structure, the new structure can enhance the volumetric efficiency and mass flow-rate by 1.8~2.7% and 26.6~57.2%, respectively; and compared to the traditional injection structure, the new structure can increase the heating capacity and COP by 23.1~48.9% and 3.2~8.0%, respectively

Effects of Economizer Type and Size to the Gas Injected System Using Zeotropic R32/R1234ze(E) Mixture

Refrigerant mixtures are commonly regarded as a potential substitute because rare pure refrigerants can totally meet all the requirements of environmental, thermodynamic and safe properties. Meanwhile as an effective means, vapour injection is widely applied to improve the system performance of heat pump under large pressure ratio. However, the difference of using pure refrigerant and refrigerant mixtures, which configuration of vapour injection is more suitable for refrigerant mixtures are still unclear. In this paper, R32/R1234ze(E) mixtures are chosen as refrigerant pairs for its great potential in the future, and the scroll compressor is chosen as well to carry out the research for its wide application in vapour injected system. The thermodynamic model with different suction and injected concentration is derived, on the basis of this model, a detailed compressor and system performance comparison of different vapour injected configurations with R32/R1234ze(E) mixtures are investigated. The results indicate that the lower concentration of R32 in flash tank (FT) system will result in higher power consumption compared with intermediate heat exchanger (IHX) system. For the system performance, the heating capacity of FT system is 5%~9.1% higher than IHX system, while the COP of latter system is usually higher, the largest improvement is 2.7% when charged with R32/R1234ze(E) (40/60) mixtures

Magnetic poles enabled kirigami meta-structure for stable mechanical memory storage with high information density

Some bi or multi-stable Mechanical meta-structures have been implemented as mechanical memory devices which however are with limits such as complex structural forms, low information storage capability and/or fragile structural stability to maintain the stored information bits robustly under external interferences. To address these issues, we refer to the structural intelligence by constructing a simple 3D-printable multi-layered cylindrical kirigami module with gradient structural parameters and propose a mechanical memory device that can robustly store information bits exponentially larger than previous designs. We demonstrate the promising enhancement of information storage capability of our proposed mechanical memory device relies on two mechanisms 1 the deformation sequences of the kirigami module enabled by the gradient structural parameter, which brings the extra dimensional degree of freedom to break the traditional mechanical memory unit with only planar form and merits information bits with spatially combinatorical programmability, and 2 the combinatorics of the deformation independences among the cylindrical kiriagmi unit arrays in the constructed mechanical memory device. Particularly, we achieve both the structural stabilities and the desired structural robustness in the mechanical memory devices by additively introducing magnetic N-S poles in units, which can protect the stored information from interferences like mechanical crushing, impacting and or shaking

Seasonal Applicability of Refrigerant Release Technology in Room Air Conditioner

The room air conditioner is widely used in residential and office buildings for both cooling and heating. However, the operation condition of the room air conditioner changes largely due to the variations of the cooling/heating load of the room, the indoor temperature and the outdoor one, which always decreases the efficiency of the compressor and eventually the seasonal energy efficiency of the air conditioner. The refrigerant release technology relieves even eliminates the over-compression loss of scroll compressor by bypassing the refrigerant in the compression chamber to the suction pipe under small system pressure ratio conditions, By using it, the efficiency of the air conditioner can be increased. The effect of refrigerant-releasing on the annual energy performance of the room air conditioner is analyzed and the applicability is evaluated in this paper. The typical residential and office building models are built in a building load simulation software, DeST. The annual cooling and heating loads of these buildings located in different climate zones are calculated. The numerical models of the fixed speed and inverter room air conditioners with and without refrigerant-releasing function are built and verified. For the air conditioner with refrigerant-releasing, a control strategy to activate the refrigerant release is determined to keep the efficiency as well as satisfy the indoor load. Based on the calculated cooling/heating load and the models of the air conditioners, the energy consumptions of all four kinds of air conditioner during each hour can be calculated. Finally, the performance of variable and fixed speed air conditioner with and without refrigerant release in the cooling period and heating period is obtained and the contribution of refrigerant-releasing is evaluated. The results show that the variable speed air conditioner with refrigerant-releasing saves 24.2~25.5% and 18.9~25.3% energy compared to the one without refrigerant release for the office and residential buildings, respectively. For the fixed speed air conditioner, the refrigerant-releasing technology decreases 20.2~23.0% and 17.1~23.6% energy consumption for residential and office building, respectively. Variable speed air conditioner with refrigerant release saves more energy than fixed speed one. The refrigerant-releasing technology has good applicability for the room air conditioner and should be considered as an effective method to enhance the seasonal performance for it

Twisting the Toll: Electric Vehicles and Information Provision

The transportation sector generates the largest share of greenhouse gas emissions, which concerns governments and communities worldwide. Electric vehicles (EVs) are believed to be the future. Various incentives have been provided to further broaden their acceptance and accelerate their adoption, including toll-exemption programs for EVs. At the same time, an individual’s driving behaviors are largely shaped by navigation applications that provide real-time traffic conditions. In this paper, we aim to understand how information provision affects the optimal structure of the EV-exempt toll. By analyzing a Bayesian routing game, we illustrate the optimality of a non-monotonic tolling strategy as a function of the EV adoption rate. For policymakers, our finding reveals the importance of understanding how the IT-enabled information provision has altered individual drivers\u27 behavior. In addition, the results uncover the general impact of IT, which expands the action space of individuals and the effective regimes of policies