Search results
Results From The WOW.Com Content Network
trans-1,3,3,3-Tetrafluoropropene (HFO-1234ze(E), R-1234ze(E)) is a hydrofluoroolefin. It was developed as a "fourth generation" refrigerant to replace fluids such as R-134a, as a blowing agent for foam and aerosol applications, and in air horns and gas dusters. [3] The use of R-134a is being phased out because of its high global warming ...
According to ASHRAE standard 34, the R-number of a chemical refrigerant is assigned systematically according to its molecular structure and has between two and four digits. If there are carbon-carbon multiple bonds, there are four digits in all: the number of these bonds is the first digit and the number of carbon atoms minus one (C-1) is next ...
Refrigerants are typically evaluated on both their global warming potential (GWP) and ozone depletion potential (ODP).The GWP scale is standardized to carbon dioxide, where the refrigerant's value is the multiple of the heat that would be absorbed by the same mass of carbon dioxide over a period of time. [11]
However, like methane, R-410A has a global warming potential (GWP) that is appreciably worse than CO 2 (GWP = 1) for the time it persists. R-410A is a mixture of 50% HFC-32 and 50% HFC-125. HFC-32 has a 4.9 year lifetime and a 100-year GWP of 675 and HFC-125 has a 29-year lifetime and a 100-year GWP of 3500.
Difluoromethane is thus a relatively low-risk choice among HFC refrigerants, most of which have higher GWP and longer persistence when leaks occur. The common refrigerant R-410A is a zeotropic, 50/50-mass-percent mixture of difluoromethane and pentafluoroethane .
As a refrigerant, it is designated R-1234yf [1] and marketed under the names Opteon YF by Chemours and as Solstice YF by Honeywell. [3] R-1234yf is also a component of zeotropic refrigerant blend R-454B. HFO-1234yf has a GWP less than carbon dioxide, [4] [2] itself 1,430 times less potent than R-134a. [5]
This is an electron transport chain (ETC). Electron transport chains often produce energy in the form of a transmembrane electrochemical potential gradient. The gradient can be used to transport molecules across membranes. Its energy can be used to produce ATP or to do useful work, for instance mechanical work of a rotating bacterial flagella.
Class 1: This class includes refrigerants that cool by phase change (typically boiling), using the refrigerant's latent heat. Class 2: These refrigerants cool by temperature change or 'sensible heat', the quantity of heat being the specific heat capacity x the temperature change. They are air, calcium chloride brine, sodium chloride brine ...