A receptacle in which food is placed may be cooled by keeping it wet with a drip system. Take a wooden box with a sound bottom made of one piece and invert it. Tack a layer of cotton batting over it and cover with some coarse cloth. It is now to be kept wet by an automatic drip, such as an old aluminum pan with tiny holes that supply just enough water to keep the cloth saturated. Under this box, lettuce in cold water, a cold pudding, a pat of butter, and other food were placed and kept in good condition. A pan of milk lowered into another of cold water is kept from souring many hours longer than if it was unprotected from the surrounding air.
Requirements for a household refrigerating machine include maintaining food compartments between 40-50°F automatically, freezing water and desserts efficiently, low initial cost, dependable operation without adjustments or service, simplicity in design and operation, quietness of operation, preventing leakage at stuffing box, accessibility for repairs, safety of exterior moving parts, adaptability for installing as a single unit with cabinet, freedom from wear of moving parts, positive valve operation, necessary lubrication under all conditions, protection against misplacement of lubricant, limiting gasket and pipe connections to prevent refrigerating gas escape, protecting the compressor from liquid refrigerant or lubricant damage, insuring necessary cooling of compressor and motor, protecting metals from rust and corrosion.
The reciprocating type of compressor is in general use with refrigerants such as sulphur dioxide, ammonia, methyl chloride, carbon dioxide, and high-pressure air. Blowers and turbine compressors are mostly used with ethyl chloride, ether, formic-aldeliyde, and low-pressure air. Sulphur dioxide compressors are used most extensively on household refrigerating machines.
The condenser is used to cool and liquefy the refrigerant gas as it leaves the compressor or blower. The customary cooling medium is either water or air. Some systems use tap water from the city mains, while others conduct warm water leaving the condenser to a well or tank which is in the ground.
Air-cooled condensers are rapidly gaining favor for small household machines due to lower initial cost and reduced installation costs.
Key Takeaways
- Maintaining food compartments between 40-50°F is crucial for preserving perishable items.
- Sulphur dioxide compressors are commonly used in household refrigerating machines.
- Condensers can use either water or air as cooling mediums, with air-cooled systems becoming more popular.
Practical Tips
- Use a wooden box with wet cloth to keep food cool when modern refrigeration is unavailable.
- Ensure your compressor operates efficiently by using the appropriate lubricant and avoiding over-lubrication.
- Consider installing an air-cooled condenser for lower initial costs and reduced installation complexity.
Warnings & Risks
- Improper lubrication can lead to inefficiencies or damage in compressors, so follow manufacturer guidelines carefully.
- Water-cooled systems require a consistent water supply; ensure there is no risk of freezing lines in cold weather.
Modern Application
While the chapter focuses on early mechanical refrigerators and cooling methods from the 1920s, many principles still apply today. Understanding these historical techniques can be invaluable for emergency situations where modern appliances are unavailable or non-functional.
Frequently Asked Questions
Q: What is a common method to keep food cool without electricity?
A wooden box with wet cloth and an automatic drip system can be used to keep food cool by lowering the temperature of the water in which it is placed.
Q: Why are air-cooled condensers becoming more popular for small household machines?
Air-cooled condensers offer lower initial costs, reduced installation complexity, and eliminate the risk of freezing lines in cold weather compared to water-cooled systems.
Q: What refrigerant is commonly used in household refrigerating machines according to this chapter?
Sulphur dioxide compressors are widely used in household refrigerating machines due to their efficiency and reliability.