Heat and Mass Transfer
FUNDAMENTAL CONCEPTS
Heat transfer is energy in transit, which occurs as a result of temperature gradient or difference.
This temperature difference is thought of as a driving force that causes heat to flow. The concepts of heat transfer and temperature, the key words in the discipline of heat transfer, are 2 of the most basic concepts of thermodynamics.
dffffffffff rifffff orfff ffffffffff fv ing ff ce
Rate of transport process= fffffffffff or rate = coefficient B driving force resist ance
System: a region in space containing a quantity of matter which is separated from its surroundings by a boundary. Closed system (no – flow system): no exchange of matter with the surroundings, only heat and work cross the boundary. Open system (flow system): there is matter exchange with the surroundings in addition to heat and work.
Work (W): is a transient quantity (energy) which only appears at the boundary when a system changes its state due to the movement of a part of the boundary under the action of a force.
Sign convention: system +
-
the work is done by the system on the surroundings: the work exits the
the work is done on the system by the surroundings.
(Although there cannot be said to be any work in a system either before or after the change has taken place, work may be said to “flow” or be “transferred” across the boundary.)
Heat (Q): is “something” (energy transfer), which only appears at the boundary when a system changes its state due to a difference in temperature between the system and its surrounding. Heat, like work, is a transient quantity, which only appears at a boundary while a change is taking place within the system. (Although there cannot be said to be any heat in a system before and after a change of state, loosely speaking heat may be said to “flow” or be “transferred” across the boundary. Strictly speaking it is energy which is transferred, but to say “heat is transferred” is a shorthand way of saying “the
Heat transfer is energy in transit, which occurs as a result of temperature gradient or difference.
This temperature difference is thought of as a driving force that causes heat to flow. The concepts of heat transfer and temperature, the key words in the discipline of heat transfer, are 2 of the most basic concepts of thermodynamics.
dffffffffff rifffff orfff ffffffffff fv ing ff ce
Rate of transport process= fffffffffff or rate = coefficient B driving force resist ance
System: a region in space containing a quantity of matter which is separated from its surroundings by a boundary. Closed system (no – flow system): no exchange of matter with the surroundings, only heat and work cross the boundary. Open system (flow system): there is matter exchange with the surroundings in addition to heat and work.
Work (W): is a transient quantity (energy) which only appears at the boundary when a system changes its state due to the movement of a part of the boundary under the action of a force.
Sign convention: system +
-
the work is done by the system on the surroundings: the work exits the
the work is done on the system by the surroundings.
(Although there cannot be said to be any work in a system either before or after the change has taken place, work may be said to “flow” or be “transferred” across the boundary.)
Heat (Q): is “something” (energy transfer), which only appears at the boundary when a system changes its state due to a difference in temperature between the system and its surrounding. Heat, like work, is a transient quantity, which only appears at a boundary while a change is taking place within the system. (Although there cannot be said to be any heat in a system before and after a change of state, loosely speaking heat may be said to “flow” or be “transferred” across the boundary. Strictly speaking it is energy which is transferred, but to say “heat is transferred” is a shorthand way of saying “the