Stated differently, a drop in temperature of 10° F (5.5° C) causes a pressure decrease of about 82 psi (565 kPa). If an air cylinder is pressurized to 4,500 psi at 96° F and later the temperature drops to 32° F, the pressure gauge will indicate 4,000 psi (4,500/1.13). The scientifically valid change in temperature from 32 to 96 ☏ (0 to 36 ☌) is by a factor of 1.13 (308.71° K/273.15° K), not 3. Instead of comparing 32° F to 96° F, temperatures of 273.15° K and 308.71° K should be compared. While 96 is arithmetically three times 32, the difference in temperature from a scientific point of view is not threefold. Consider the freezing point of water at 32° F (0° C, 273.15° K) and compare it to 96° F (35.6° C or 308.71° K normal human body temperature is 37° C). (See Universal gas constant.) What is particularly important to understand from the formula is that the temperature is in kelvins, not degrees Fahrenheit. The relationship between the temperature and the pressure of a gas is defined by the formula PV = nRT. As temperature decreases, the pressure inside the cylinder decreases. The pressure gauge's indicated gas pressure changes with ambient temperature.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |