Say the word and you'll be free.
Say the word and be like me.

("The Word," by the Beatles, 1965)

PTOA Segment 57:  Where Do We Go From Here? (#2): 

Heat Transfer: The flow of thermal energy from an area that is hotter to an area that is colder.

 

PTOA Segment 58: Can't Live Without It.

Delta,Δ: The 4th letter in the Greek alphabet which mathematicians used for shorthand to mean 'the change between observed measurements."

Delta T (aka "ΔT"): The nickname for "Temperature Differential" which is defined below.

Heat: Flowing thermal energy typically described in units of BTUs or Joules.

The operative word in the above definition is "flowing"; when the energy ceases to be in transition, then "heat" no longer exists.

Heat Sink: A vast cold area into which heat is being transferred from a warmer area. The cold area is so vast that the final temperature of the combined hot and cold areas will be the same temperature as the cold area even after heat transfer has been completed.

Temperature Differential: The driving force for all three types of heat transfer is the existence of an area that is hotter than a nearby colder area.The difference in temperature between the hot area and the cold area is called the Temperature Differential and is typically measured in °F or °C.

The Temperature Differential is calculated by subtracting the hot temperature from the cold temperature as shown below:

Temperature Differential =
Hot Temp (°F or °C)  -  Cold Temp (°F or °C)

The greater the Temperature Differential, the more heat will be transferred over a period of time.

 

PTOA Segment 59: I'm So Hot 4 U And Yur So Cold!

British Thermal Unit (aka BTU): A traditional unit of thermal energy content; the amount of thermal energy it takes to raise the temperature of a pound of water from 58.9 °F to 59.9 °F while at atmospheric pressure.

Heat Rate: The amount of heat that is transferred over a given unit of time, usually and hour. Typical units for heat rate are BTUs/hr or Joules/hr.

The phrase "the rate of heat transfer" is another way of stating "the heat rate is...."

Joule: A joule is equal to 1055 BTUs.

Joules are the scientific units of energy in use internationally. Otherwise stated, joules are the units of energy used in the "International System" of units which are abbreviated "SI" units.

Rate: Used verbally and in written form, "rate" indicates that something is taking place over a specified time interval. For example "per day," "per hour," "per year."

Here are two common process industry examples:

"Slowly increase the flow rate to 100,000 Barrels/day."

"The exchanger is designed to for a heat rate of 480,000 BTU/hr."

The "/" slashmark takes the place of the spoken word 'per' in the expression.

The units of time always appears in the denominator of the expression.

The definition of rate is not limited to its use in Process Technology.

"Birth rate" means "number of births per unit time."

"Interest rate" means "the amount of interest accrued per unit time."

"Murder rate" means how many murders were committed over a period of time.

"Drop out rate" means the number of drop outs over a period of time.

 

PTOA Segment 60: I Am the Walrus

Distance: A basic unit of length, in this case a long length like a kilometer or mile or really long distances like light years.

Length: A basic unit that describes how long a short segment is from here to there, usually expressed in feet or inches or centimeters or millimeters.

Mass: A basic unit that describes 'matter.' Matter is anything that exists, usually measured in pounds, grams, kilograms (mass units applied). See the definition of Stuff.

Matter: The scientific name for "stuff" which is also the same as "mass."

Stuff: One of the basic units and also the non scientific name for "mass" and "matter." Stuff is everything that takes up space in the universe.

On earth, all stuff is can be broken down into whatever elements on the Periodic Table of Elements the stuff is made out of.

Stuff is made up of varying combinations and bonding of elements; ergo stuff can be 100% similar with respect to what it is made out of and still have totally unique physical and chemical properties all because of differences in boding at the atomic level.

Time: a basic unit usually measured in hours, minutes, or seconds.

 

PTOA Segment 61: I Am Still The Walrus

This PTOA Segment 61 informed PTOA Readers and Students that human beings started using mathematical expressions to define concepts like Velocity (aka Speed).

No additional process industry jargon was included in this PTOA Segment.

 

PTOA Segment 62: Can't Touch This

A: A symbol for Surface Area used in the mathematical expression that defines Conduction Heat Transfer.

The units of surface area are typically square feet (ft²), square inches (in²), square meters (m²), or square centimeters (cm²).

The greater the surface area exposed to Conduction Heat Transfer (Q/t), the greater the rate of conduction heat transfer.

Conduction: A type of heat transfer in which the atoms that make up a physical barrier become excited when one of the sides of the barrier is exposed to heat.

The heated atoms start bumping into each other and thus excite nearby atoms ... which then start bumping into each other ... ergo spreading the heat through the physical barrier to the side that is cooler.

d: A symbol for the thickness of the physical barrier that separates a hot area from a cold area in heat transfer via conduction. The units for "d" are typically inches, feet, centimeters, or meters.

Conduction Heat Transfer Rate rate (Q/t)  is "inversely related to" the thickness of the barrier, d. Otherwise stated, d will appear in the denominator of the mathematical expression that defines Conduction Heat Transfer.

The inverse relationship between Conduction Heat Transfer (Q/t) and barrier thickness (d) also means:

• as d increases, Conduction Heat Transfer Rate decreases.
• as d decreases, Conduction Heat Transfer Rate increases. 

Heat Transfer via Conduction:  The transfer of heat through a physical barrier that separates an area that is hotter from an area that is colder.

k: A symbol for the Thermal Conductivity Factor used in the mathematical expression for Conduction Heat Transfer Rate (Q/t).

Typical units for k are  [Watt/(meters-°K)] which equals  0.5779 [ BTU / (foot hr °F)].

PTOA Readers and Students should not be stressed about the weird units for k; they were forced to be weird so that the units of the mathematical expression that defines Conduction Heat Transfer (Q/t) would be consistent. "Consistent" means the "Q/t" on the left side of the expression that defines Conduction Heat Transfer would match the "Q/t" that remains on the right side of the expression once all the factors on the right side are reduced (aka cancelled out).

No kidding. The scientists that dedicated their lives to modelling how heat transfer works in the Universe just added the units where they were needed in the definition of the Thermal Conductivity Factor to force the units on both sides of the expression to be consistent. Scientists use this 'fudge factor of units' method for modelling the Universe all the time.

Physical Barrier: Any barrier that can be seen (even with a microscope) and touched. In Conduction Heat Transfer the physical barrier separates an area that is hotter from an area that is colder.

Q/t: The Conduction Heat Transfer Rate, typically expressed in BTUs/hr or Joules/hr.

Thermal Conductivity Factor: The ability for a material to conduct heat through it.  A high TCF is a good conductor. A low TCF is a poor conductor but a great insulator.

The Thermal Conductivity Factor is represented by the letter k in the mathematical expression that defines Conduction Heat Transfer (Q/t).

Typical units for k are  [Watt/(meters-°K)] which equals  0.5779 [ BTU / (foot hr °F)].

©2015 PTOA Segment 00089
PTOA Process Industry Jargon Recap 3-1

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