China
Africa
Explore chapters and articles related to this topic
Heat Pump Systems for Drying
Published in Vasile Minea, Industrial Heat Pump-Assisted Wood Drying, 2018
A single-stage mechanical vapor compression air-to-air heat pump operates according to the real cycle schematically represented in Figure 10.5b and c. The compression process 1-2 is polytropic (δq≠0), and the expansion process 4-5 is isenthalpic (dh = 0). The refrigerant is the HFO-1234yf. The heat pump is coupled with a lumber kiln and operates with an average evaporating temperature of 20°C, average condensing temperature of 70°C, and average discharge temperature of 80°C. The superheating at the evaporator outlet is of 5°C and the subcooling amount at the condenser outlet, 8°C. The average refrigerant flow rate is 0.4 kg/s.
Green Lubricants and Lubrication
Published in R. Ganesh Narayanan, Jay S. Gunasekera, Sustainable Material Forming and Joining, 2019
Sayanti Ghosh, Lalit Kumar, Vivek Rathore, Shivanand M. Pai, Bharat L. Newalkar
Further research led to the development of hydrofluorinated olefins (HFOs). Presently, HFO-1234yf (2,3,3,3-tetrafluoroprop-1-ene) is the potential candidate of low global warming refrigerant in mobile air conditioning (Short and Rajewski, 1995). New low GWP refrigerant blends are under development for use in commercial and industrial refrigeration (Council Directive 70/156/EEC, 2006). There is some renewed interest in carbon dioxide and hydrocarbons for commercial use but installation costs and safety issues have limited their application.
Refrigeration Cycles
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
Heat ventilation, air-conditioning, and refrigeration (HVAC&R) equipments have been primarily using high-GWP HFC refrigerants since the 1990s. To comply with the global HFC phasedown targets and proposals, the industry started developing equipment that uses low-GWP alternative refrigerants. As per those regulations, an ideal refrigerant should (i) be non-toxic, (ii) be non-flammable, (iii) have zero ozone depletion potential (ODP), (iv) have zero GWP, (v) have acceptable operating pressures, and (vi) have volumetric capacity appropriate to the application. Low-GWP HFCs include hydrocarbons, ammonia, carbon dioxide, and hydrofluoroolefins (HFOs). Hydrocarbons: The three most viable hydrocarbon refrigerants include propane, isobutane, and propylene. These hydrocarbons have GWP values of 3, and they are classified as A3 refrigerants due to their high flammability.Ammonia: It is classified as B2 refrigerant and has a GWP value of 0. Refrigeration systems in industrial applications often use ammonia as a refrigerant. Due to its class B toxicity rating, ammonia cannot make itself as a suitable candidate for comfort conditioning applications or indoor commercial refrigeration applications.Carbon dioxide (CO2): It is classified as A1 (non-flammable, non-toxic) and has a GWP of 1. CO2 has been proved to be a viable alternative for several applications including heat pumps, water heaters, commercial refrigerated vending machines, supermarket refrigeration, secondary expansion systems, and industrial and transport refrigeration systems. Carbon dioxide is also a technically viable option in mobile vehicle air-conditioning (MVAC) systems.Hydrofluoroolefins (HFOs): These are emerging as the most viable alternative refrigerants. Refrigerant manufacturers have developed several HFO blends specifically to some applications. HFO-1234yf and HFO1234ze are a step ahead along in development. HFO-1234yf and HFO-1234ze are both classified as A2L and have GWP values less than 1. Moreover, the performance of HFO-1234yf is almost close to that of HFC-134a. HFO-1234yf has been extensively used outside the USA for future MVAC systems, and one automobile manufacturing company based in the USA has been dedicated to using HFO-1234yf since 2013. HFO-1234yf also shows the potential as a refrigerant in chillers and commercial refrigeration applications that are currently using HFC-134a. Table 12.1 shows the ozone depletion and global warming potential of various refrigerants.
Exergy and energy analysis of low GWP refrigerants in the perspective of replacement of HFC-134a in a home refrigerator
Published in International Journal of Ambient Energy, 2022
Mohammad Hasheer Shaik, Srinivas Kolla, Bala Prasad Katuru
A systematic procedure is developed for the selection of Low GWP refrigerants to replace HFC134a refrigerant in a domestic refrigerator.Among HFO refrigerants, the refrigerant HFO-1234yf shows a very small reduction in Volumetric cooling capacity, Refrigerating effect, Compressor power consumption and COP when compared to the refrigerant HFC 134a and also it has a low GWP value which makes it possible to replace HFC 134a.The refrigerant HFO-1234yf is a best choice to replace conventional R134a refrigerant without making any modifications to the existing system and also the refrigerant HFC-152a becomes a good choice to replace R134a with some safety precautions when operating at high condenser temperatures.Condenser and Liquid suction heat exchanger (LSHX) have highest and lowest Efficiency defect respectively, among all the system components of a home refrigerator.
Thermodynamic Analysis of Air Conditioning System for a Passenger Vehicle with Suction Line Heat Exchanger Using HFO-1234yf
Published in Heat Transfer Engineering, 2023
Rajendran Prabakaran, Dhasan Mohan Lal, Sung Chul Kim
As shown in Figure 4c, the variance in the cooling capacity between the considered refrigerants is high at a lower EAFR and narrowed as the EAFR increases. The same trend was observed for COP variations also. The refrigeration effect of HFO-1234yf was found to be consistently smaller than that of HFC-134a, although it had a better cooling capacity at idle speeds owing to the enhanced mass flow rate. At idle speed, the COP and cooling capacity of the VAC operated with HFO-1234yf were improved by 2.9–10.7% and 1.5–11.1% as compared to HFC-134a. At 1800 rpm, the evaporator capacity of the HFO-1234yf increased by 6.4% compared to HFC-134a, while it marginally declined at lower EAFR. However, the COP of the VAC with HFO-1234yf decreased by 2–11% for a given EAFRs. Under high-speed conditions, both the evaporator capacity and COP of the VAC were poorer for HFO-1234yf by 1.2–6.3% and 6.3–20.3%. Zhao et al. [16] reported a similar observation when the VAC system operated under moderate and peak load conditions. Overall, the VAC performance with HFO-1234yf was higher in the phases of cooling capacity and COP at idle speed as compared to the system operated with HFC-134a. As the speed increased to the city limit and high speeds, the performance of the system with HFC-134a was found to be superior to that of HFO-1234yf for the considered EAFRs. Similar test results were also observed by Prabakaran et al. [35]. However, Cho and Park [33] found that the VAC system operated with HFO-1234yf performed better after employing the SLHX compared to the system operating with HFC-134a at certain compressor speeds and declined in performance at other speeds.