heat and evaporate the liquid refrigerant and enough heat must be extracted from B to condense the gas. Another method is to apply ice or cool B. When the outlet pipe from C is below the liquid level in C the liquid refrigerant will pass to D in liquid form. It is only necessary to either warm C or cool D. This establishes a pressure difference which readily forces the liquid into container D. In charging household systems, it is customary to first use a vacuum pump to eliminate the air and moisture from the re- frigerating system. Then the refrigerant is charged in liquid form. The amount of charge is regulated by weighing or using a glass liquid gauge on the charging receiver. It is extremely dangerous to heat a cylinder containing liquid refrigerant. When the pressure drops in charging it is probably best to place the cylinder in a bucket of water in order to supply sufficient heat to evaporate the liquid refriger- ant from the cylinder rapidly. In charging a thermostat, it is very important to first eliminate the air. The best method is to use a vacuum pump, although it is possible to eliminate practically all of the air by repeatedly charging and discharging the .thermostat bulb and line with the gas to be used. The liquid should fill about two-thirds of the bulb. An overcharged thermostat may cause considerable trouble.<Callout type="warning" title="Safety Hazard">Do not heat cylinders containing liquid refrigerant.</Callout> Method of Determining the Density of a Gas. — The volume of any gas may be approximately determined from its molecular weight at atmospheric pressure of 14.7 lbs. and 60° F., as follows : Weight per cu. ft. = molecular weight / 376 Cu. ft. per pound = molecular weight / 376 The volume of one cu. ft. of sulphur dioxide gas at 14.7 lbs. atmospheric pressure and 60° F. would be found as fol- lows : — 0.170 lbs. / 64 = 0.265 cu. ft./lb. The volume in cu. ft., per pound is found as follows: TABLE XVI.— MOLECULAR WEIGHT OF GASES Gas Molecular Weight Nitrogen— N2 28 Oxygen— O; 32 Carbon Dioxide — COj 44 Sulphur Dioxide — SO. 64 Hydrogen — Hj 2 Ammonia — NHs 17 Air 28.1 <Callout type="important" title="Critical Rule">Always use a vacuum pump to remove air and moisture before charging.</Callout> CHAPTER IV. REFRIGERANTS— TABLES. 1. Properties of Saturated Ammonia — Temp. — Table X'II. 2. Properties of Saturated Ammonia — Pressure — Table XVIII. 3. Properties of Liquid Ammonia. — Table XIX. 4. Properties of Superheated Ammonia Vapors. — Table XX. 5. Properties of Saturated Vapor of Butane. — Table XXII. 6. Properties of Saturated Vapor of Carbon Bisulphide. — Table XXIII. 7. Properties of Carbon Dioxide. — Table XXI. 8. Properties of Saturated Vapor of Carbon Tetrachloride. — Table XXIV. 9. Properties of Saturated Vapor of Chloroform. — Table XXV. 10. Properties of Saturated Vapor of Ethane. — Table XXVI. 11. Properties of Saturated Vapor of Ethyl Chloride. — Table XXIX. 12. Properties of Saturated Vapor of Ethylene Ether. — Table XXVI. 13. Properties of Saturated Vapor of Isobutane. — Table XXX. 14. Properties of Saturated Methyl Chloride Vapor. — Table XXXI. 15. Properties of Saturated Vapor of Nitrous Oxide.- — Table XXVII. 16. Properties of Saturated Vapor of Propane. — Table XXXII. 17. Properties of Saturated Vapor of Sulphur Dioxide.- — Table XXXIII. 18. Properties of Superheated Vapor of Sulphur Dioxide. — Table XXXIV. 19. Standard Ton Data.— Table XXXV. 20. Properties of Aqua-Ammonia (Percent Concentration Table).— Tables XXXVIII, XXXIX. 21. Solubility of Ammonia in Water. — Table XXXVI. 22. Heat of Association of x mmonia. — Table XXXVII. 23. Solubility of Gases in Water at Atmospheric Pressure. — Table XL. 24. Compressibility of Liquids. — Table XLI.
Key Takeaways
- Use a vacuum pump to remove air and moisture before charging refrigerants
- Do not heat cylinders containing liquid refrigerant
- Charge refrigerants in liquid form
Practical Tips
- Always use a vacuum pump to ensure the system is free of contaminants, which can affect performance.
- Keep track of the amount of refrigerant charged by weighing or using a glass gauge for accurate measurements.
- Avoid overcharging thermostats as it may cause malfunctions.
Warnings & Risks
Safety Hazard
Heating cylinders containing liquid refrigerant can lead to dangerous pressure build-up and potential explosions.
Overcharging a thermostat can damage the system, leading to costly repairs or failures. - Ensure proper ventilation when handling refrigerants to avoid inhaling harmful gases.
Modern Application
While the specific techniques for charging household refrigeration systems have evolved since 1927, the principles of maintaining a clean and properly charged system remain crucial. Modern refrigerators use similar methods but with more advanced technology. Understanding these basics can help in troubleshooting or preparing emergency backup systems.
Frequently Asked Questions
Q: What is the best method to remove air and moisture from a refrigeration system before charging?
The best method is to first use a vacuum pump to eliminate the air and moisture from the refrigerating system. This ensures that the system remains clean and prevents issues with performance.
Q: Why is it dangerous to heat cylinders containing liquid refrigerant?
Heating cylinders containing liquid refrigerant can lead to dangerous pressure build-up, which may result in explosions or other serious accidents. It is extremely important to avoid this practice for safety reasons.
Q: How do you determine the volume of a gas from its molecular weight?
The volume of any gas at atmospheric pressure can be approximately determined by dividing the molecular weight by 376. For example, one cubic foot of sulfur dioxide gas at 14.7 lbs. atmospheric pressure and 60° F. would have a volume of 0.265 cu. ft./lb.