Saturday, October 10, 2009

It's Called a Compressor Because ..

How often have your students asked for study guides and hints before tests? Tell them that the hints are built into the terminology. In many cases, HVAC/R terms define themselves. The names for most components and processes are not randomly chosen, they are frequently drawn from general vocabulary to describe a component or process. For example, a compressor compresses gas. The word compress means to make smaller. When you squeeze something you make it smaller, or compress it. The compressor raises the pressure and temperature of the gas by squeezing it, making its volume smaller. If the students understand that compress means to squeeze, they should have no trouble remembering what the compressor does.


To truly understand HVAC/R terminology students should not simply memorize a list of attributes for the rather large number of HVAC/R terms, but should connect the function to the name. Making these connections also increases memory retention. The method that a compressor uses to accomplish its work is used to describe the types of compressors. Reciprocate means to go back and forth: a reciprocating compressor uses pistons that go back and forth in a cylinder. A scroll is spiral: scroll compressors use intermeshing spirals or scrolls to compress the gas. A screw compressor uses intermeshing auger shaped screws to compress the gas. Connecting the name to the function will help students get a mental picture of the device and increase both understanding and memory retention.


All the components of the refrigeration cycle have names that either describe their function or describe them physically. The key is for students to understand where the name comes from. If students understand that orifice is simply a three syllable word for hole, they should have not problem remembering what an orifice is. One of the reasons I believe in covering the science behind the refrigeration cycle before trying to discus the refrigeration cycle is so that these connections can be made. If the students already understand the processes of evaporation and condensation, they will have no trouble remembering what evaporators and condensers do. This same technique can be used for many aspects of HVAC/R. In electricity potential difference literally means the difference in electrical potential between two points. The refrigerant terms zeotropic and azeotropic can be better understood if you explain the vocabulary they are built on. For most of us, these words are presented simply as arcane terms for refrigerants that are mixtures of two or more refrigerants. The fact that they differ by a single letter makes remembering the difference between the two difficult. Most students complain that the two terms are “all Greek to me!” In fact they do come from Greek roots. “Zeo” is to boil, “trop” is to turn, so zeotropic refrigerants turn, or change as they boil. Placing the letter “a” in front means “not.” For example: amoral means without morals. Similarly, azeotropic refrigerants do NOT turn or change when they boil. Give a few vocabulary lessons and increase your student’s understanding and memory retention. For more HVAC/R vocabulary tips check out the glossary in Fundamentals of HVAC/R, the largest glossary in any major HVAC/R text.

1 comment:

  1. A comprehensive blog with a straight content which not all present to all blog sites. Interesting and well-written. Keep posting.
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