

WEATHER AND CLIMATE 



increase the rate of evaporation from the body. When- 

 ever heat is removed from anything it is cooled, and 



FIG. 53. AMMONIA ICE PLANT 



since evaporation must have heat to go on, it cools 

 the surroundings of the liquid which is evaporating. 

 This is important to our health, inasmuch as body 

 temperature is partly controlled by the rate of evapo- 

 ration of moisture from the skin. 



Modern science has learned how to control the 

 cooling of evaporation and how to make it work for 

 man in keeping his foods from spoiling. Artificial ice 

 is made in this way and most of the modern home elec- 

 tric refrigerators work on this principle. 



A gas which can easily be turned into a liquid, such 

 as ammonia or sulphur dioxide, is compressed and 

 is then cooled by water running over the pipes. See 

 Figure 53. The liquid ammonia or other substance 

 is then allowed to expand through a valve. As it ex- 

 pands, heat is taken from the surrounding brine, which 

 is cooled. This brine is then pumped through pipes 

 which surround boxes filled with water. The brine be- 

 comes cooler than the freezing temperature of the wa- 

 ter, and the water freezes. 



Figure 54 shows the working parts of a modern 

 electric refrigerator. The coils in which the liquid 

 evaporates are inside the refrigerator, and thus the 

 heat is taken from the inside. 



The vapors are again drawn into the compressor, 

 compressed to a liquid, and used over. 



REFERENCES FOR FURTHER STUDY 



Texts 



Caldwell and Curtis, Science for Today, Chap. 13 

 Clement, Collister, and Thurston, Our Surroundings, Chap. 



9 

 Hunter and Whitman, Science in Our World of Progress, pp. 



58-63 ; Science in Our Social Life, pp. 96-102 

 Lake, Har!ey, and Welton, Exploring the World of Science, 



Chap. 10 

 Pieper and Beauchamp, Everyday Problems in Science, Unit 



3 



Powers, Neuner, and Bruner, This Changing World, Unit 2 

 Skilling, Tours through the World of Science, Tour 3 

 Van Buskirk and Smith, The Science of Everyday Life, Chap 



6 



Watkins and Bedell, General Science for Today, Chap. 3 

 Webb and Beauchamp, Science by Observation and Experi- 

 ment, Unit 7 (part) 



Wood and Carpenter, Our Environment: How We Adapt 

 Ourselves to It, Unit 2 



Special references 



Barber, First Course in General Science 

 Jameson, Humidity and Health 



WHAT YOU SHOULD AIM TO ACQUIRE FROM 

 THIS STUDY 



1. What evaporation is and the various factors 

 which affect it. 



2. How evaporation is of importance to our health. 



3. How the principle of evaporation applies to cool- 

 ing in the electric refrigerator. 



COOLING COMPARTMENT 



EXPANSION VALVE 



THERMOSTAT -, 



tBRINE TANk 



T ' 



A 



4- ICE JTRAvT 



EXPANSION 



f co,u 



COMPARTMENTS 



TUFRI&ERATOR CABINET 

 SHOWING DIRECTION OF AIR CURRENTS 

 CONDENSER 



h-G-ASLINE 

 SUCTION 

 SHUT OFF 



( ourtfsy Ketvinator 



FIG. 54. ICELESS REFRIGERATION 



