There is no single perfect refrigerant for diverse air conditioning, refrigeration, and industrial applications. The predominant halocarbons (CFCs, HCFCs, and HFCs) combine excellent efficiency and safety with acceptable costs. However, they contribute to ozone depletion potential (ODP) and/or global warming potential (GWP). The Montreal Protocol has eliminated ODP by requiring replacement of C...

Mathematical models have been popularly applied to study the compression processes of superheated refrigerant vapor in compressors. As to the case when refrigerant enters a compressor cylinder in the state of liquid and vapor mixture, however, the availability of fundamental studies is very limited. -A mathematical model is presented to simulate the compression processes of two-phase saturated ...

This study proposes a procedure for a risk analysis for leakages of flammable refrigerants into a poorly ventilated three-dimensional space. It also presents several test cases of risk analyses on flammability and ignitions to a leaked refrigerant. Concentration of a leaked flammable refrigerant at a leakage window, Cin, is determined by mass balance, providing information on the capacity of an...

Abstract: The performances of thermodynamics cycles are dependent on the properties of refrigerants. The performances of Vuilleumier (VM) cycle heat pump adopting mixture refrigerants are analyzed by MATLAB software using REFPROP programming. At given operating parameters and configuration, performances of the VM cycle adopting pure refrigerant, H2, He or N2 are compared. Thermodynamic properti...

In this paper we discuss the threat of malware targeted at extracting information about the relationships in a real-world social network as well as characteristic information about the individuals in the network, which we dub Stealing Reality. We present Stealing Reality (SR), explain why it differs from traditional types of network attacks, and discuss why its impact is significantly more dang...

introduction pulmonary vein (pv) isolation is considered as a key to atrial fibrillation (af) treatment. cryoballoon ablation is an effective therapy for pv isolation for af with minimal side effects and was approved by the us food and drug administration (fda) several years ago. successful isolation of pvs during cryoablation depends on the balloon temperature and helps in early identification...

Air-to-refrigerant heat exchangers are a key component in all air-conditioning, heat pump and refrigeration systems. The most common of types of air-to-refrigerant heat exchangers are tube-fin and microchannel heat exchangers. There has always been a great emphasis on understating the underlying physics and improving the performance of these heat exchangers. More recently, researchers have been...

Tests were run with both R-12 and R-l34a in a water calorimeter. Refrigerant 12 was run with mineral oil as the lubricant. Evaporating and condensing heat transfer coefficients were calculated over a range of temperatures. To evaluate the impact of the lubricant on the heat transfer coefficients, a oil separator was added. Tests were then run with the oil separator over the same temperature ran...

The world-wide agreement to restrict the use of chlorofluorocarbons (CFCs) and hydrofluorocarbons has prompted recent research exploring the possibilities of replacement refrigerants, particularly those occurring naturally in the environment. One such natural refrigerant, carbon dioxide, has been shown for particular applications to have a COP which is competitive with current refrigerants. How...

Refrigerant mass flow rate is an important measurement for monitoring equipment performance and enabling fault detection and diagnostics. However, a traditional mass flow meter is expensive to purchase and install. A virtual refrigerant mass flow sensor (VRMF) uses a mathematical model to estimate flow rate using low-cost measurements and can potentially be implemented at low cost. This study e...