21 34 how many pounds of refrigerant must flow

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21-34) How many pounds of refrigerant must flow through a 4-ton evaporator each minute if each pound has an enthalpy of 50.0 Btu/lb? 1 ton = 200 BTU/minute. 4 x 200 BTU/minute = 800 BTUs/minute 800 BTUs/minute/50 BTUs/lb = 12.6 lbs/minute 21-35) What will happen in the evaporator if the compressor capacity is not large enough to remove all of the vapor? Some of the vapor will remain in the evaporator. This will cause an increase in evaporator pressure and temperature and a decrease in system capacity. 21-36) On a blank sheet of paper sketch a typical PH diagram for a refrigeration system. You do not need to duplicate all the scales on the PH diagram. Just show the saturation curve and the four cycle lines. See Figure 21-1.
67 UNIT 22 REVIEW QUESTIONS ANSWER KEY 22-1) Who was the person that was instrumental in developing the first CFCs? Thomas Midgley 22-2) Why it is important to review the MSDS before an accident happens? So that you can act quickly and respond to the necessary first aid measures required in the event of refrigerant exposure to the skin, eyes, or from inhalation, and ingestion. 22-3) What should be done to treat frostbite to the skin? If there is evidence of frostbite, then bathe (do not rub) with lukewarm (not hot) water. If water is not available, cover the affected area with a clean soft cloth. 22-4) What should be done if refrigerant comes into contact with the eyes? If refrigerant comes into contact with the eyes, immediately flush with large amounts of water for at least 15 minutes with warm (not hot) water. 22-5) High levels of refrigerant inhalation may lead to what? At high levels of inhalation, cardiac arrhythmia may occur or even asphyxiation. 22-6) How do you treat a person that has inhaled large amounts of refrigerant? If refrigerant has been inhaled then immediately remove the victim from the space to fresh air. If breathing has stopped, give artificial respiration. Because of the possible disturbances of cardiac rhythm, catecholamine drugs, such as epinephrine (adrenaline) should not be given. 22-7) Can you physically feel that there is a lack of oxygen in a confined space? You may become light headed, however under such circumstances, unconsciousness can occur quickly and with little to no warning. 22-8) What steps would you take if a person fell unconscious due to a lack of oxygen in a confined space? You do not want to rush into the space to rescue someone and become the second victim. First start the ventilation system and use a MSHA/NIOSH approved self-contained breathing apparatus to enter the space if the refrigerant concentration levels are still excessive. 22-9) Most fatal refrigeration accidents have occurred due to which type of refrigerant? Ammonia
68 22-10) How would a refrigerant safety rating of A1 compare to B3? A1 would indicate low toxicity and low flammability while B3 would indicate high toxicity and high flammability.

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