2018 RETA Breeze Jul-Aug

EDUcATIon

Dissecting Industrial Refrigeration: Book 1 Round 2 Rat e s and P r e s s ur e s

by Sarah Selzer, Safety Services Jr. Safety Engineer, Wagner-Meinert LLC

2 hours. When calculating rates both elements are equally important. 2.1 Bob is driving from Notre-Dame- du-Laus, Quebec, Canada to New eld, Maine. He plans to average 50 miles per hour due to the tra c congestion in Montreal. e trip is 415 miles. How long will it take? 2.2 A er an argument with his wife, Jim gets in his truck and drives 60 MPH for 4.5 hours from his wife before stopping for ice cream. How far is he from home? 2.3 Jerry traveled 283 miles in 4 hours. e speed limit was 70 MPH. Did Jerry break the speed limit? Another popular rate calculation each July 4th, is hot dogs per minute. is is a rate of hot dog consumption at the annual hot dog eating competition. 2.4 If Bob eats 14 hotdogs in 17 minutes what is this consumption in hot dogs per minute? In refrigeration we utilize several rate calculations. e quantity of vapor being

is article contains excerpts from RETA’s Industrial Refrigeration Book 1. e reader should take care when applying the knowledge gained from reading this material in their speci c plant. It is important to consider cause and e ect when making any adjustments to facility operating conditions. Rates are very interesting. Rates are not only a measure of what is being done, but also of how fast it is being done. Industrial Refrigeration Book 1 begins to discuss rates on page 1-10. Rates are fundamental measurements of what we do as refrigeration operators. A rate is de ned as a quantity of something changing per unit of time. e classic rate we are all exposed to is “miles per hour”. e number of miles driven, walked, ran, or bobsledded per hour.

can be compressed per minute in the compressor. e quantity of water owing into an evaporative condenser sump could be expressed in gallons owing per minute.

e most widely used rate in refrigeration is tons of refrigeration TR. is is used in conjunction with the BTU. e BTU (British thermal unit) is the amount of work needed to raise the temperature of one pound of water by one-degree Fahrenheit. e quantity of BTUs of heat energy transferred from one object to another over a period of time is expressed as a rate. e terminology is “tons” of refrigeration. For example, one ton of

drawn into a compressor would be expressed as cubic feet per minute.

We all calculate based on miles per hour, even if we don’t realize it. When you are taking a trip and you read it is 50 miles away, you convert it to time in your head. We all do, it is almost automatic. Fi y miles at 50 miles per hour will take an hour. 50 miles at 25 MPH will take

is is a compressor volume calculation describing how many cu. . of vapor

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